FRCR Oncology Part 1: PHYSICS - 4 (4 SETS, 100+100+100+100 QUESTIONS, ANSWERS BELOW)

 

Radiation Physics (20 Questions)

401. What is the approximate linear energy transfer (LET) of a 700 MeV/u carbon ion at the midpoint of a 12 cm SOBP in hypoxic tumour tissue, accounting for nuclear fragmentation and oxygenation effects?
     A. 80 keV/μm
     B. 160 keV/μm
     C. 240 keV/μm
     D. 320 keV/μm
     E. 400 keV/μm

402. For a 40 MV photon beam interacting with a molybdenum target, what is the dominant interaction process contributing to secondary neutron production in a proton FLASH setup?
     A. Photoelectric effect
     B. Compton scattering
     C. Pair production
     D. Photodisintegration
     E. Coherent scattering

403. Calculate the half-value layer (HVL) for a 30 MV photon beam in tungsten, given a mass attenuation coefficient of 0.05 cm²/g and density of 19.25 g/cm³.
     A. 0.5 cm
     B. 0.7 cm
     C. 0.9 cm
     D. 1.1 cm
     E. 1.3 cm

404. In a proton FLASH radiotherapy setup with 250 MeV protons at 300 Gy/s, what is the primary mechanism reducing the oxygen enhancement ratio (OER) in hypoxic tumour cells?
     A. Enhanced nuclear interactions
     B. Ultra-fast radical recombination
     C. Reduced Compton scattering
     D. Increased bremsstrahlung yield
     E. Altered pair production

405. What is the continuous slowing down approximation (CSDA) range of a 1 GeV proton in cortical bone (density 1.85 g/cm³), accounting for nuclear interactions and straggling?
     A. 50 cm
     B. 60 cm
     C. 70 cm
     D. 80 cm
     E. 90 cm

406. Which factor most significantly affects the relative biological effectiveness (RBE) variation in a 600 MeV/u carbon ion beam for a hypoxic pancreatic tumour?
     A. Beam energy spread
     B. LET and hypoxia interplay
     C. Beam divergence
     D. Nuclear fragmentation tail
     E. Collimator material

407. What is the energy of a characteristic X-ray emitted from the M-shell to K-shell transition in rhenium (Z=75)?
     A. 30 keV
     B. 50 keV
     C. 70 keV
     D. 90 keV
     E. 110 keV

408. For a 5 keV photon beam in cortical bone, what is the dominant interaction, and how does its cross-section scale with atomic number (Z)?
     A. Compton scattering, Z-independent
     B. Photoelectric effect, ∝ Z³
     C. Pair production, ∝ Z²
     D. Coherent scattering, ∝ Z
     E. Photodisintegration, ∝ Z⁴

409. What is the primary interaction mechanism for 200 MeV neutrons in bone, considering secondary particle cascades?
     A. Elastic scattering with protons
     B. Inelastic scattering with calcium
     C. Neutron capture by phosphorus
     D. Spallation reactions
     E. Compton scattering

410. What is the mass stopping power ratio of lung tissue to water for a 50 MeV electron beam, considering density effects (lung: 0.26 g/cm³, water: 1.00 g/cm³)?
     A. 0.20
     B. 0.26
     C. 0.30
     D. 0.40
     E. 0.50

411. Which factor most significantly affects the production of secondary gamma rays in a 700 MeV proton beam interacting with a graphite range shifter?
     A. Target atomic number
     B. Nuclear excitation
     C. Collimator thickness
     D. Beam current
     E. Gantry angle

412. What is the dose rate at 6 meters from a 15 GBq Tc-99m source, given a specific gamma-ray constant of 0.08 R·m²/Ci·h, ignoring shielding and assuming air kerma?
     A. 0.02 mGy/h
     B. 0.2 mGy/h
     C. 2 mGy/h
     D. 20 mGy/h
     E. 200 mGy/h

413. Which equation correctly describes the energy dependence of the pair production cross-section for ultra-high-energy photons (>100 MeV)?
     A. ∝ E
     B. ∝ E²
     C. ∝ ln(E)
     D. ∝ 1/E
     E. ∝ 1/E²

414. What is the approximate range of a 60 MeV electron in aluminium (density 2.7 g/cm³), accounting for radiative losses?
     A. 1.5 cm
     B. 2.0 cm
     C. 2.5 cm
     D. 3.0 cm
     E. 3.5 cm

415. In a targeted alpha therapy using Po-210, what is the primary mode of energy deposition in metastatic tumour cells?
     A. Bremsstrahlung radiation
     B. Alpha particle emission
     C. Gamma ray emission
     D. Compton scattering
     E. Photoelectric effect

416. What is the primary source of nuclear recoil energy in a 700 MeV/u carbon ion beam interacting with a hypoxic tumour?
     A. Elastic scattering
     B. Nuclear fragmentation
     C. Compton scattering
     D. Pair production
     E. Bremsstrahlung radiation

417. Which material property most significantly affects the lateral dose spread of a 800 MeV proton beam in a 3D-printed bolus?
     A. Electron density
     B. Atomic number
     C. Mass density
     D. Thermal conductivity
     E. Magnetic susceptibility

418. What is the approximate energy threshold for eta meson production in a proton beam interacting with a titanium target?
     A. 500 MeV
     B. 1 GeV
     C. 1.5 GeV
     D. 2 GeV
     E. 2.5 GeV

419. Which shielding configuration is most effective for 300 MeV neutrons in a carbon ion MRT facility?
     A. Lead followed by concrete
     B. Polyethylene followed by cadmium
     C. Steel followed by boron
     D. Water followed by paraffin
     E. Concrete followed by hydrogen-rich material

420. What is the primary mode of energy loss for a 50 GeV electron in lead, considering synchrotron radiation effects?
     A. Collisional interactions
     B. Bremsstrahlung radiation
     C. Compton scattering
     D. Pair production
     E. Synchrotron radiation

Dosimetry (20 Questions)

421. What is the absorbed dose rate at 5 meters from a 20 GBq Y-90 source, given a specific gamma-ray constant of 0.015 R·m²/Ci·h, ignoring shielding?
     A. 0.03 mGy/h
     B. 0.3 mGy/h
     C. 3 mGy/h
     D. 30 mGy/h
     E. 300 mGy/h

422. Which quantity is most critical for assessing the risk of radiation-induced cardiovascular disease in proton arc therapy?
     A. Absorbed dose
     B. Equivalent dose
     C. Effective dose
     D. Kerma
     E. Exposure

423. What is the radiation weighting factor (W_R) for 200 MeV neutrons in radiation protection, per ICRP 103?
     A. 2
     B. 5
     C. 10
     D. 20
     E. 50

424. What is the percentage depth dose (PDD) at 30 cm depth for a 30 MV photon beam (10x10 cm² field, SSD=100 cm) in water, given a PDD of 100% at dmax=4.5 cm and an attenuation coefficient of 0.03 cm⁻¹?
     A. 35%
     B. 40%
     C. 45%
     D. 50%
     E. 55%

425. Which dosimeter is most suitable for measuring dose in a 0.01 mm² microbeam radiotherapy field with 300 keV X-rays?
     A. Ionisation chamber
     B. TLD
     C. Nanodot OSL
     D. Radiochromic film
     E. Quantum dot detector

426. What is the monitor unit (MU) required to deliver 6 Gy to a depth of 20 cm through a 3 cm lung slab (density=0.26 g/cm³, μ/ρ=0.03 cm²/g) and 2 cm bone slab (density=1.85 g/cm³, μ/ρ=0.05 cm²/g) for a 25 MV photon beam (10x10 cm² field, SAD=100 cm, output factor=1.04, TMR=0.60)?
     A. 600 MU
     B. 700 MU
     C. 800 MU
     D. 900 MU
     E. 1000 MU

427. What is the approximate depth of the 90% isodose line for a 700 MeV/u carbon ion beam in water, assuming an 8 cm SOBP?
     A. 35 cm
     B. 40 cm
     C. 45 cm
     D. 50 cm
     E. 55 cm

428. Which factor most significantly affects the accuracy of nanodosimetry in a 0.01 cm² field for carbon ion MRT?
     A. Detector charge collection efficiency
     B. Beam energy spread
     C. Source-to-detector distance
     D. Collimator misalignment
     E. Nuclear fragmentation

429. What is the primary advantage of carbon nanotube detectors in proton FLASH dosimetry?
     A. High spatial resolution
     B. Ultra-fast response time
     C. Low cost
     D. Energy independence
     E. Large dynamic range

430. What is the tissue maximum ratio (TMR) at 35 cm depth for a 30 MV photon beam (10x10 cm² field, SAD=100 cm), given a PDD of 35% at 35 cm, PDD of 100% at dmax=4.5 cm, and BSF of 1.06?
     A. 0.30
     B. 0.33
     C. 0.36
     D. 0.39
     E. 0.42

431. What is the equivalent dose from a 3 mGy absorbed dose of 100 MeV protons to the heart?
     A. 0.03 mSv
     B. 0.3 mSv
     C. 3 mSv
     D. 6 mSv
     E. 30 mSv

432. What is the effective dose from a 5 mGy absorbed dose to the pancreas (tissue weighting factor=0.12) from 200 MeV neutrons (W_R=10)?
     A. 0.06 mSv
     B. 0.6 mSv
     C. 6 mSv
     D. 60 mSv
     E. 600 mSv

433. Which dosimetry protocol is most suitable for calibrating a 800 MeV proton beam in a graphite phantom?
     A. TG-21
     B. TG-51
     C. IAEA TRS-398
     D. AAPM TG-61
     E. TRS-483

434. What is the primary source of uncertainty in diamond-based nanodosimetry for verifying a proton FLASH therapy plan?
     A. Energy dependence
     B. Detector alignment
     C. Spatial resolution
     D. Readout reproducibility
     E. Temperature sensitivity

435. What is the monitor unit (MU) correction factor for a 4 cm lung inhomogeneity (density=0.26 g/cm³, μ/ρ=0.03 cm²/g) and 3 cm bone inhomogeneity (density=1.85 g/cm³, μ/ρ=0.05 cm²/g) in a 30 MV photon beam at 25 cm depth?
     A. 0.85
     B. 0.90
     C. 0.95
     D. 1.00
     E. 1.05

436. Which dosimeter is most suitable for in-vivo dosimetry in a MR-guided carbon ion MRT setup?
     A. Ionisation chamber
     B. TLD
     C. Carbon nanotube detector
     D. MOSFET
     E. Plastic scintillator

437. What is the primary purpose of the output factor (OF) in nanodosimetry for proton FLASH therapy?
     A. To quantify patient scatter
     B. To normalize dose for field size
     C. To measure dose at depth
     D. To assess beam flatness
     E. To determine penumbra width

438. What is the approximate penumbra width (20%–80%) for a 800 MeV proton beam at 70 cm depth in water, considering nuclear interactions?
     A. 5 mm
     B. 7 mm
     C. 9 mm
     D. 11 mm
     E. 13 mm

439. Which factor most significantly affects the dose rate from a proton FLASH therapy source at 400 Gy/s?
     A. Beam pulse frequency
     B. Source intensity
     C. Source energy
     D. Source material
     E. Source shape

440. What is the primary advantage of silicon carbide detectors in carbon ion MRT dosimetry?
     A. High spatial resolution
     B. Radiation hardness
     C. Real-time readout
     D. Low cost
     E. Energy independence

Radiotherapy Treatment Planning (20 Questions)

441. What is the primary advantage of proton FLASH therapy over carbon ion arc therapy for deep-seated sarcomas?
     A. Reduced treatment time
     B. Ultra-high dose rate sparing
     C. Lower cost
     D. Increased scatter dose
     E. Simplified planning

442. Which parameter is most critical for defining the planning target volume (PTV) in carbon ion MRT for a brain tumour?
     A. Tumour size
     B. Beamlet spacing and motion
     C. Beam energy
     D. Field size
     E. Monitor units

443. What is the primary advantage of carbon ion MRT over proton arc therapy for radioresistant tumours?
     A. Uniform dose distribution
     B. Enhanced RBE in hypoxic regions
     C. Increased treatment time
     D. Lower cost
     E. Simplified planning

444. Which dose calculation algorithm is most accurate for proton FLASH therapy in a lung tumour with a 0.26 g/cm³ density heterogeneity?
     A. Pencil beam
     B. Convolution-superposition
     C. Monte Carlo
     D. Acuros XB
     E. Collapsed cone

445. What is the primary purpose of a dynamic aperture in carbon ion MRT?
     A. To increase beam energy
     B. To sharpen lateral dose fall-off
     C. To reduce skin sparing
     D. To monitor dose delivery
     E. To reduce scatter radiation

446. Which factor most significantly affects the distal dose fall-off in proton FLASH therapy for a liver tumour?
     A. Beam energy
     B. Nuclear fragmentation tail
     C. Pulse duration
     D. Collimator shape
     E. Monitor units

447. What is the primary advantage of AI-driven dose prediction in carbon ion MRT planning?
     A. Reduced treatment time
     B. Optimized peak-valley dose ratios
     C. Lower cost
     D. Increased scatter dose
     E. Simplified planning

448. Which parameter is most critical for normal tissue complication probability (NTCP) in proton FLASH therapy (α/β=2 Gy)?
     A. Total dose
     B. Dose rate
     C. Beam energy
     D. Field size
     E. Monitor units

449. What is the primary purpose of a patient-specific range compensator in carbon ion MRT for a pelvic tumour?
     A. To increase beam energy
     B. To correct for tissue heterogeneity
     C. To shape the radiation field
     D. To monitor dose delivery
     E. To reduce scatter radiation

450. Which factor most significantly affects the dose conformity in carbon ion MRT for a spinal tumour?
     A. Beamlet spacing
     B. Beam energy
     C. Field size
     D. Gantry angle
     E. Monitor units

451. What is the primary advantage of deep learning-based synthetic CT in MR-only proton FLASH planning?
     A. Reduced imaging time
     B. Accurate stopping power estimation
     C. Lower cost
     D. Increased scatter dose
     E. Simplified planning

452. Which structure is most critical for dose constraints in carbon ion MRT for a pancreatic tumour?
     A. Spinal cord
     B. Duodenum
     C. Kidneys
     D. Heart
     E. Lungs

453. What is the primary purpose of a beam-specific collimator in proton FLASH therapy?
     A. To increase beam energy
     B. To sharpen lateral dose fall-off
     C. To reduce skin sparing
     D. To monitor dose delivery
     E. To reduce scatter radiation

454. Which factor most significantly affects the dose heterogeneity in proton FLASH therapy?
     A. Pulse structure
     B. Beam energy
     C. Field size
     D. Gantry angle
     E. Monitor units

455. What is the primary advantage of generative adversarial networks (GANs) in carbon ion MRT planning?
     A. Reduced treatment time
     B. Enhanced dose prediction accuracy
     C. Lower cost
     D. Increased scatter dose
     E. Simplified planning

456. Which parameter is most critical for tumour control probability (TCP) in carbon ion MRT?
     A. Tumour volume
     B. Peak-to-valley dose ratio
     C. Beam energy
     D. Field size
     E. Monitor units

457. What is the primary purpose of a ripple filter in proton FLASH therapy?
     A. To increase beam energy
     B. To sharpen the Bragg peak
     C. To shape the radiation field
     D. To monitor dose delivery
     E. To reduce scatter radiation

458. Which factor most significantly affects the dose distribution in carbon ion MRT for bulky sarcomas?
     A. Beamlet spacing
     B. Beam energy
     C. Field size
     D. Gantry angle
     E. Monitor units

459. What is the primary advantage of hypoxia-guided dose escalation in proton FLASH therapy?
     A. Reduced treatment time
     B. Targeting radioresistant subvolumes
     C. Lower cost
     D. Increased scatter dose
     E. Simplified planning

460. Which parameter is most critical for dose-volume histogram (DVH) optimization in proton FLASH therapy?
     A. Beam energy
     B. Normal tissue constraints
     C. Field size
     D. Monitor units
     E. Collimator angle

Imaging (20 Questions)

461. What is the primary advantage of 15T MRI in radiotherapy planning for spinal tumours?
     A. Ultra-high spatial resolution
     B. Low radiation dose
     C. Real-time imaging
     D. Electron density information
     E. Low cost

462. Which imaging modality is most suitable for assessing intrafraction motion in oesophageal carbon ion MRT?
     A. CT
     B. MRI
     C. PET
     D. 4D-CT
     E. Fluoroscopy

463. What is the primary source of contrast in glucoCEST MRI for oncology?
     A. Proton density
     B. Glucose metabolism
     C. Electron density
     D. Atomic number
     E. Blood flow

464. Which factor most significantly affects the signal-to-noise ratio in photon-counting CT for carbon ion MRT planning?
     A. Detector quantum efficiency
     B. Tube voltage
     C. Reconstruction algorithm
     D. Field of view
     E. Gantry rotation speed

465. What is the primary advantage of Po-210 PET in targeted alpha therapy planning?
     A. High spatial resolution
     B. Low radiation dose
     C. Alpha emitter tracking
     D. Real-time imaging
     E. Low cost

466. Which radionuclide is most suitable for imaging tumour hypoxia in proton FLASH therapy planning?
     A. F-18 (FMISO)
     B. Tc-99m
     C. Ga-68
     D. I-131
     E. Zr-89

467. What is the primary purpose of the contrast-to-noise ratio (CNR) in MR-guided carbon ion MRT?
     A. To measure radiation dose
     B. To quantify tissue differentiation
     C. To assess image noise
     D. To determine spatial resolution
     E. To monitor patient motion

468. Which factor most significantly affects the temporal resolution in 4D-MRI for proton FLASH therapy?
     A. Field strength
     B. Gradient slew rate
     C. Coil sensitivity
     D. Reconstruction algorithm
     E. Field of view

469. What is the primary advantage of spectral CT in proton FLASH therapy planning?
     A. High soft tissue contrast
     B. Material-specific imaging
     C. Low radiation dose
     D. Real-time imaging
     E. Low cost

470. Which imaging modality is most suitable for delineating pancreatic tumours in carbon ion MRT planning?
     A. CT
     B. MRI
     C. PET
     D. 4D-CT
     E. Ultrasound

471. What is the primary source of artefacts in 15T MRI for radiotherapy planning?
     A. Photon scattering
     B. B0 field inhomogeneity
     C. Metal implants
     D. Reconstruction algorithm
     E. Patient motion

472. Which factor most significantly affects the contrast resolution in dynamic contrast-enhanced (DCE) MRI for carbon ion MRT?
     A. Contrast agent dose
     B. Magnetic field strength
     C. Reconstruction algorithm
     D. Field of view
     E. Patient size

473. What is the primary advantage of MR elastography in proton FLASH therapy planning?
     A. High spatial resolution
     B. Low radiation dose
     C. Assessment of tissue stiffness
     D. Real-time imaging
     E. Low cost

474. Which imaging modality is most suitable for assessing spinal cord motion in carbon ion MRT planning?
     A. CT
     B. MRI
     C. PET
     D. 4D-CT
     E. Ultrasound

475. What is the primary purpose of AI-based image segmentation in proton FLASH therapy?
     A. To measure radiation dose
     B. To automate contouring
     C. To assess image contrast
     D. To determine spatial resolution
     E. To monitor image noise

476. Which factor most significantly affects the radiation dose in spectral CT for carbon ion MRT planning?
     A. Energy thresholding
     B. Tube current
     C. Reconstruction algorithm
     D. Field of view
     E. Gantry rotation speed

477. What is the primary advantage of hyperpolarized 129Xe MRI in proton FLASH therapy planning?
     A. High spatial resolution
     B. Low radiation dose
     C. Lung ventilation imaging
     D. Real-time imaging
     E. Low cost

478. Which imaging modality is most suitable for real-time tumour tracking in carbon ion MRT?
     A. CT
     B. MRI
     C. PET
     D. Fluoroscopy
     E. Ultrasound

479. What is the primary source of contrast in amide proton transfer (APT) MRI for oncology?
     A. Proton density
     B. Protein content
     C. Electron density
     D. Radiotracer uptake
     E. Tissue relaxation time

480. Which factor most significantly affects the spatial resolution in PET imaging for proton FLASH therapy planning?
     A. Detector crystal size
     B. Tube current
     C. Reconstruction algorithm
     D. Field of view
     E. Patient size

Radiation Protection (20 Questions)

481. What is the annual equivalent dose limit for the skin of radiation workers in the UK, per IRR 2017?
     A. 1 mSv
     B. 20 mSv
     C. 50 mSv
     D. 150 mSv
     E. 500 mSv

482. Which material is most effective for shielding 400 MeV neutrons in a proton FLASH therapy facility?
     A. Lead
     B. Polyethylene with boron
     C. Perspex
     D. Steel
     E. Water

483. What is the primary purpose of the optimization principle in IR(ME)R 2017 for carbon ion MRT?
     A. To maximize radiation dose
     B. To minimize patient exposure
     C. To measure radiation dose
     D. To calibrate dosimeters
     E. To monitor radiation levels

484. Which factor most significantly affects the occupational dose in a carbon ion MRT setup?
     A. Beam energy
     B. Neutron shielding design
     C. Field size
     D. Gantry angle
     E. Monitor units

485. What is the approximate tenth-value layer (TVL) for a 700 MeV/u carbon ion beam in concrete?
     A. 20 cm
     B. 30 cm
     C. 40 cm
     D. 50 cm
     E. 60 cm

486. Which type of personal dosimeter is most suitable for monitoring dose in a proton FLASH therapy setup?
     A. Film badge
     B. TLD
     C. MOSFET
     D. OSL dosimeter
     E. Real-time scintillator

487. What is the primary source of stray radiation in a carbon ion MRT treatment room?
     A. Primary beam
     B. Patient scatter
     C. Neutron contamination
     D. Bremsstrahlung radiation
     E. Compton scattering

488. Which regulation requires reporting of significant radiation incidents in a radiotherapy department in the UK?
     A. IRR 2017
     B. IR(ME)R 2017
     C. RIDDOR 2013
     D. COSHH 2002
     E. MHRA 2008

489. What is the dose rate at 3 meters from a 10 GBq Po-210 source, given a specific gamma-ray constant of 0.02 R·m²/Ci·h, ignoring shielding?
     A. 0.05 mGy/h
     B. 0.5 mGy/h
     C. 5 mGy/h
     D. 50 mGy/h
     E. 500 mGy/h

490. Which factor most significantly affects the shielding requirements for a proton FLASH therapy facility?
     A. Beam energy
     B. Neutron yield
     C. Field size
     D. Gantry angle
     E. Monitor units

491. What is the primary purpose of a radiation protection supervisor (RPS) in a carbon ion MRT department?
     A. To deliver radiotherapy
     B. To oversee local safety compliance
     C. To calibrate dosimeters
     D. To monitor patient doses
     E. To perform quality assurance

492. Which material is most effective for shielding secondary X-rays in a proton FLASH therapy bunker?
     A. Lead
     B. Concrete
     C. Polyethylene
     D. Boron
     E. Perspex

493. What is the annual effective dose limit for the fetus of a pregnant radiation worker in the UK, per IRR 2017?
     A. 1 mSv
     B. 5 mSv
     C. 10 mSv
     D. 20 mSv
     E. 50 mSv

494. Which factor most significantly affects the dose to staff during Po-210 targeted alpha therapy procedures?
     A. Source activity
     B. Shielding placement
     C. Field size
     D. Gantry angle
     E. Monitor units

495. What is the primary advantage of a lead-lined syringe in Po-210 radionuclide therapy?
     A. Reduced treatment time
     B. Minimized gamma ray exposure
     C. Increased patient comfort
     D. Simplified quality assurance
     E. Enhanced dose delivery

496. Which type of radiation is most challenging to shield in a carbon ion MRT facility?
     A. Gamma rays
     B. X-rays
     C. Beta particles
     D. Neutrons
     E. Alpha particles

497. What is the primary purpose of a radiation safety audit in a proton FLASH therapy department?
     A. To deliver radiotherapy
     B. To ensure regulatory compliance
     C. To calibrate dosimeters
     D. To monitor patient doses
     E. To perform quality assurance

498. Which factor most significantly affects the dose rate from a Po-210 unsealed source?
     A. Source activity
     B. Alpha particle energy
     C. Source size
     D. Source material
     E. Source shape

499. What is the approximate half-life of Po-210 used in targeted alpha therapy?
     A. 138 days
     B. 30 days
     C. 7 days
     D. 2 days
     E. 12 hours

500. Which principle is most critical for reducing public dose in a carbon ion MRT facility?
     A. Time
     B. Distance
     C. Shielding
     D. Justification
     E. Calibration

Answers

Radiation Physics

401. B. At the midpoint of a 12 cm SOBP, a 700 MeV/u carbon ion has an LET of ~160 keV/μm in hypoxic tissue, adjusted for fragmentation and reduced OER.

402. D. Photodisintegration in molybdenum produces neutrons for 40 MV photons (E > 7 MeV).

403. B. HVL = ln(2)/(μ·ρ) = 0.693/(0.05·19.25) ≈ 0.7 cm.

404. B. Ultra-fast radical recombination reduces OER in proton FLASH at 300 Gy/s, sparing hypoxic cells.

405. C. CSDA range for 1 GeV protons in bone = 84 cm in water / 1.85 ≈ 70 cm (R ∝ E¹·⁵).

406. B. LET and hypoxia interplay drives RBE variation (~4–6) in hypoxic pancreatic tumours.

407. C. M-to-K transition in rhenium emits ~70 keV photons (K-shell binding energy).

408. B. Photoelectric effect dominates at 5 keV in bone, scaling as ∝ Z³.

409. D. Spallation reactions dominate for 200 MeV neutrons, producing cascades.

410. B. Mass stopping power ratio of lung to water is ~0.26 due to density (S ∝ ρ).

411. B. Nuclear excitation produces secondary gamma rays in proton beams.

412. B. Dose rate = (Γ·A)/r² = (0.08·15/37)/(6²) ≈ 0.2 mGy/h (1 GBq = 27 mCi).

413. C. Pair production cross-section scales as ∝ ln(E) for ultra-high energies.

414. C. Range in aluminium = 60/2.7 ≈ 2.5 cm (R ≈ 0.5 E, adjusted for radiative losses).

415. B. Alpha particle emission is the primary energy deposition mode for Po-210.

416. B. Nuclear fragmentation produces recoil energy in carbon ion beams.

417. B. Atomic number drives lateral dose spread via Coulomb scattering.

418. B. Eta meson production in titanium requires ~1 GeV.

419. B. Polyethylene slows 300 MeV neutrons, and cadmium captures thermal neutrons.

420. B. Bremsstrahlung radiation dominates for 50 GeV electrons in lead (E > critical energy).

Dosimetry

421. B. Dose rate = (Γ·A)/r² = (0.015·20/37)/(5²) ≈ 0.3 mGy/h (1 GBq = 27 mCi).

422. C. Effective dose assesses cardiovascular risk (heart W_T=0.12).

423. C. W_R for 200 MeV neutrons is 10 per ICRP 103.

424. B. PDD = 100 · e^(-μ·(d-dmax)) = 100 · e^(-0.03·(30-4.5)) ≈ 40%.

425. E. Quantum dot detectors offer sub-μm resolution for 0.01 mm² microbeam fields.

426. D. MU = Dose/(TMR·Output·CF), CF_lung = e^(0.03·3·(0.26-1)) ≈ 0.94, CF_bone = e^(0.05·2·(1.85-1)) ≈ 1.09, Total CF = 0.94·1.09 ≈ 1.02, MU = 6/(0.60·1.04·1.02) ≈ 900 MU.

427. C. 700 MeV/u carbon ion range ~50 cm, 90% isodose at SOBP center ~45 cm.

428. A. Detector charge collection efficiency affects nanodosimetry accuracy in 0.01 cm² fields.

429. B. Carbon nanotube detectors offer ultra-fast response for proton FLASH dose rates.

430. B. TMR = PDD(d)/PDD(dmax) · BSF = 35/(100·1.06) ≈ 0.33.

431. D. Equivalent dose = 3 mGy · 2 (W_R for 100 MeV protons) = 6 mSv.

432. C. Effective dose = 5 mGy · 0.12 (W_T for pancreas) · 10 (W_R for neutrons) = 6 mSv.

433. C. IAEA TRS-398 is suitable for 800 MeV proton calibration.

434. B. Detector alignment is the primary uncertainty in diamond-based nanodosimetry.

435. B. CF_lung = e^(0.03·4·(0.26-1)) ≈ 0.91, CF_bone = e^(0.05·3·(1.85-1)) ≈ 1.14, Total CF = 0.91·1.14 ≈ 0.90.

436. C. Carbon nanotube detectors are MR-compatible for carbon ion MRT.

437. B. Output factor normalizes dose for field size in proton FLASH nanodosimetry.

438. C. Penumbra width for 800 MeV protons at 70 cm is ~9 mm (scattering, nuclear interactions).

439. B. Source intensity drives dose rate in proton FLASH therapy.

440. B. Silicon carbide detectors offer radiation hardness for carbon ion MRT dosimetry.

Radiotherapy Treatment Planning

441. B. Proton FLASH therapy offers ultra-high dose rate sparing for sarcomas.

442. B. Beamlet spacing and motion are critical for brain tumour PTV in carbon ion MRT.

443. B. Carbon ion MRT enhances RBE in hypoxic radioresistant tumours.

444. C. Monte Carlo is most accurate for proton FLASH in low-density lung.

445. B. Dynamic apertures sharpen lateral dose fall-off in carbon ion MRT.

446. B. Nuclear fragmentation tail affects distal dose fall-off in proton FLASH.

447. B. AI-driven dose prediction optimizes peak-valley ratios in carbon ion MRT.

448. B. Dose rate drives NTCP in proton FLASH (altered OER, α/β=2 Gy).

449. B. Range compensators correct for heterogeneity in pelvic carbon ion MRT.

450. A. Beamlet spacing affects dose conformity in spinal carbon ion MRT.

451. B. Synthetic CT ensures accurate stopping power in MR-only proton FLASH.

452. B. Duodenum is critical for dose constraints in pancreatic carbon ion MRT.

453. B. Beam-specific collimators sharpen lateral dose fall-off in proton FLASH.

454. A. Pulse structure causes dose heterogeneity in proton FLASH therapy.

455. B. GANs enhance dose prediction accuracy in carbon ion MRT planning.

456. B. Peak-to-valley dose ratio drives TCP in carbon ion MRT.

457. B. Ripple filters sharpen the Bragg peak in proton FLASH therapy.

458. A. Beamlet spacing determines dose distribution in carbon ion MRT for sarcomas.

459. B. Hypoxia-guided dose escalation targets radioresistant subvolumes in proton FLASH.

460. B. Normal tissue constraints drive DVH optimization in proton FLASH.

Imaging

461. A. 15T MRI provides ultra-high spatial resolution for spinal tumour delineation.

462. B. MRI is suitable for oesophageal intrafraction motion in carbon ion MRT.

463. B. GlucoCEST MRI contrast arises from glucose metabolism.

464. A. Detector quantum efficiency affects SNR in photon-counting CT.

465. C. Po-210 PET tracks alpha emitters for targeted therapy planning.

466. A. F-18 (FMISO) is suitable for imaging tumour hypoxia.

467. B. CNR quantifies tissue differentiation in MR-guided carbon ion MRT.

468. B. Gradient slew rate affects temporal resolution in 4D-MRI.

469. B. Spectral CT enables material-specific imaging for proton FLASH planning.

470. B. MRI is ideal for delineating pancreatic tumours in carbon ion MRT.

471. B. B0 field inhomogeneity causes artefacts in 15T MRI.

472. A. Contrast agent dose affects contrast resolution in DCE-MRI.

473. C. MR elastography assesses tissue stiffness in proton FLASH planning.

474. B. MRI is suitable for assessing spinal cord motion in carbon ion MRT.

475. B. AI-based image segmentation automates contouring in proton FLASH.

476. B. Tube current affects radiation dose in spectral CT.

477. C. Hyperpolarized 129Xe MRI images lung ventilation for proton FLASH planning.

478. B. MRI enables real-time tumour tracking in carbon ion MRT.

479. B. APT MRI contrast arises from protein content via amide proton exchange.

480. A. Detector crystal size affects PET spatial resolution.

Radiation Protection

481. E. The annual equivalent dose limit for the skin is 500 mSv (IRR 2017).

482. B. Polyethylene with boron shields 400 MeV neutrons effectively.

483. B. Optimization in IR(ME)R 2017 minimizes patient exposure in carbon ion MRT.

484. B. Neutron shielding design most significantly affects dose in carbon ion MRT.

485. D. TVL for 700 MeV/u carbon ions in concrete is ~50 cm (high density).

486. E. Real-time scintillators are suitable for proton FLASH due to ultra-high dose rates.

487. C. Neutron contamination is the primary stray radiation in carbon ion MRT.

488. B. IR(ME)R 2017 requires reporting significant radiation incidents.

489. B. Dose rate = (Γ·A)/r² = (0.02·10/37)/(3²) ≈ 0.5 mGy/h (1 GBq = 27 mCi).

490. B. Neutron yield drives shielding requirements for proton FLASH facilities.

491. B. RPS oversees local safety compliance in carbon ion MRT.

492. A. Lead is most effective for shielding secondary X-rays.

493. A. The annual effective dose limit for the fetus is 1 mSv (IRR 2017).

494. B. Shielding placement most significantly affects staff dose in Po-210 therapy.

495. B. Lead-lined syringes minimize gamma ray exposure in Po-210 therapy.

496. D. Neutrons are most challenging to shield in carbon ion MRT facilities.

497. B. Radiation safety audits ensure regulatory compliance in proton FLASH departments.

498. A. Source activity drives the dose rate from Po-210 (alpha/gamma emitter).

499. A. The half-life of Po-210 is ~138 days.

500. C. Shielding is critical for reducing public dose in carbon ion MRT facilities.

Radiation Physics (20 Questions)

501. What is the approximate linear energy transfer (LET) of a 600 MeV/u carbon ion beam at the distal edge of a 12 cm spread-out Bragg peak (SOBP) in soft tissue (density 1.04 g/cm³)?
     A. 80 keV/μm
     B. 120 keV/μm
     C. 160 keV/μm
     D. 200 keV/μm
     E. 240 keV/μm

502. For a 35 MV photon beam interacting with a lead collimator in a proton arc therapy setup, what is the dominant interaction process contributing to secondary neutron production?
     A. Photoelectric effect
     B. Compton scattering
     C. Pair production
     D. Photonuclear reactions
     E. Coherent scattering

503. Calculate the half-value layer (HVL) for a 30 MV photon beam in concrete, given a mass attenuation coefficient of 0.04 cm²/g and density of 2.35 g/cm³.
     A. 5.0 cm
     B. 6.0 cm
     C. 7.0 cm
     D. 8.0 cm
     E. 9.0 cm

504. In a proton FLASH radiotherapy setup with 250 MeV protons at 500 Gy/s, what is the primary mechanism reducing the oxygen enhancement ratio (OER) in a hypoxic sarcoma?
     A. Enhanced nuclear interactions
     B. Ultra-fast radical recombination
     C. Reduced Compton scattering
     D. Increased bremsstrahlung yield
     E. Altered pair production

505. What is the continuous slowing down approximation (CSDA) range of a 1.2 GeV proton in water, accounting for nuclear interactions?
     A. 60 cm
     B. 70 cm
     C. 80 cm
     D. 90 cm
     E. 100 cm

506. Which factor most significantly affects the relative biological effectiveness (RBE) variation in a 700 MeV/u carbon ion beam for a hypoxic chordoma?
     A. Beam energy spread
     B. LET and hypoxia interplay
     C. Beam divergence
     D. Nuclear fragmentation tail
     E. Collimator material

507. What is the energy of a characteristic X-ray emitted from the L-shell to K-shell transition in tungsten (Z=74)?
     A. 50 keV
     B. 60 keV
     C. 70 keV
     D. 80 keV
     E. 90 keV

508. For a 5 keV photon beam in soft tissue, what is the dominant interaction, and how does its cross-section scale with atomic number (Z)?
     A. Compton scattering, Z-independent
     B. Photoelectric effect, ∝ Z³
     C. Pair production, ∝ Z²
     D. Coherent scattering, ∝ Z
     E. Photodisintegration, ∝ Z⁴

509. What is the primary interaction mechanism for 200 MeV neutrons in bone, considering secondary particle cascades?
     A. Elastic scattering with protons
     B. Inelastic scattering with calcium
     C. Neutron capture by phosphorus
     D. Spallation reactions
     E. Compton scattering

510. What is the mass stopping power ratio of bone to water for a 60 MeV electron beam, considering density effects (bone: 1.85 g/cm³, water: 1.00 g/cm³)?
     A. 1.40
     B. 1.60
     C. 1.85
     D. 2.00
     E. 2.20

511. Which factor most significantly affects the production of secondary neutrons in a 500 MeV proton beam interacting with a graphite range shifter?
     A. Target atomic number
     B. Nuclear excitation
     C. Collimator thickness
     D. Beam current
     E. Gantry angle

512. What is the dose rate at 5 meters from a 15 GBq Co-60 source, given a specific gamma-ray constant of 0.31 R·m²/Ci·h, ignoring shielding and assuming air kerma?
     A. 0.1 mGy/h
     B. 1 mGy/h
     C. 10 mGy/h
     D. 100 mGy/h
     E. 1000 mGy/h

513. Which equation correctly describes the energy dependence of the Compton scattering cross-section for high-energy photons (>10 MeV)?
     A. ∝ E
     B. ∝ E²
     C. ∝ 1/E
     D. ∝ 1/E²
     E. ∝ ln(E)

514. What is the approximate range of a 70 MeV electron in aluminum (density 2.70 g/cm³), accounting for radiative losses?
     A. 1.5 cm
     B. 2.0 cm
     C. 2.5 cm
     D. 3.0 cm
     E. 3.5 cm

515. In a targeted alpha therapy using At-211, what is the primary mode of energy deposition in metastatic tumour cells?
     A. Bremsstrahlung radiation
     B. Alpha particle emission
     C. Gamma ray emission
     D. Compton scattering
     E. Photoelectric effect

516. What is the primary source of nuclear recoil energy in a 800 MeV/u carbon ion beam interacting with a hypoxic glioma?
     A. Elastic scattering
     B. Nuclear fragmentation
     C. Compton scattering
     D. Pair production
     E. Bremsstrahlung radiation

517. Which material property most significantly affects the lateral dose spread of a 900 MeV proton beam in a titanium bolus?
     A. Electron density
     B. Atomic number
     C. Mass density
     D. Thermal conductivity
     E. Magnetic susceptibility

518. What is the approximate energy threshold for pion production in a proton beam interacting with a beryllium target?
     A. 100 MeV
     B. 200 MeV
     C. 300 MeV
     D. 400 MeV
     E. 500 MeV

519. Which shielding configuration is most effective for 300 MeV neutrons in a proton FLASH facility?
     A. Lead followed by paraffin
     B. Polyethylene followed by boron
     C. Steel followed by concrete
     D. Water followed by cadmium
     E. Concrete followed by hydrogen-rich material

520. What is the primary mode of energy loss for a 150 GeV electron in copper, considering synchrotron radiation effects?
     A. Collisional interactions
     B. Bremsstrahlung radiation
     C. Compton scattering
     D. Pair production
     E. Synchrotron radiation

Dosimetry (20 Questions)

521. What is the absorbed dose rate at 4 meters from a 10 GBq Cs-137 source, given a specific gamma-ray constant of 0.11 R·m²/Ci·h, ignoring shielding?
     A. 0.03 mGy/h
     B. 0.3 mGy/h
     C. 3 mGy/h
     D. 30 mGy/h
     E. 300 mGy/h

522. Which quantity is most critical for assessing the risk of radiation-induced skin erythema in carbon ion MRT?
     A. Absorbed dose
     B. Equivalent dose
     C. Effective dose
     D. Kerma
     E. Exposure

523. What is the radiation weighting factor (W_R) for 300 MeV neutrons in radiation protection, per ICRP 103?
     A. 2
     B. 5
     C. 10
     D. 20
     E. 50

524. What is the percentage depth dose (PDD) at 35 cm depth for a 35 MV photon beam (10x10 cm² field, SSD=100 cm) in water, given a PDD of 100% at dmax=5 cm and an attenuation coefficient of 0.025 cm⁻¹?
     A. 30%
     B. 35%
     C. 40%
     D. 45%
     E. 50%

525. Which dosimeter is most suitable for measuring dose in a 0.01 mm² microbeam radiotherapy field with 300 keV X-rays?
     A. Ionisation chamber
     B. TLD
     C. Nanodot OSL
     D. Silicon diode
     E. Radiochromic film

526. What is the monitor unit (MU) required to deliver 7 Gy to a depth of 25 cm through a 3 cm lung slab (density=0.26 g/cm³, μ/ρ=0.03 cm²/g) and 2 cm bone slab (density=1.85 g/cm³, μ/ρ=0.05 cm²/g) for a 35 MV photon beam (10x10 cm² field, SAD=100 cm, output factor=1.05, TMR=0.60)?
     A. 700 MU
     B. 800 MU
     C. 900 MU
     D. 1000 MU
     E. 1100 MU

527. What is the approximate depth of the 80% isodose line for a 800 MeV/u carbon ion beam in water, assuming a 10 cm SOBP?
     A. 40 cm
     B. 45 cm
     C. 50 cm
     D. 55 cm
     E. 60 cm

528. Which factor most significantly affects the accuracy of nanodosimetry in a 0.02 cm² field for proton FLASH therapy?
     A. Detector charge collection efficiency
     B. Beam energy spread
     C. Source-to-detector distance
     D. Collimator misalignment
     E. Nuclear fragmentation

529. What is the primary advantage of perovskite detectors in carbon ion MRT dosimetry?
     A. High spatial resolution
     B. Ultra-fast response time
     C. Low cost
     D. Energy independence
     E. Large dynamic range

530. What is the tissue maximum ratio (TMR) at 40 cm depth for a 35 MV photon beam (10x10 cm² field, SAD=100 cm), given a PDD of 30% at 40 cm, PDD of 100% at dmax=5 cm, and BSF of 1.07?
     A. 0.25
     B. 0.28
     C. 0.31
     D. 0.34
     E. 0.37

531. What is the equivalent dose from a 4 mGy absorbed dose of 200 MeV protons to the thyroid?
     A. 0.04 mSv
     B. 0.4 mSv
     C. 4 mSv
     D. 8 mSv
     E. 40 mSv

532. What is the effective dose from a 6 mGy absorbed dose to the lung (tissue weighting factor=0.12) from 300 MeV neutrons (W_R=10)?
     A. 0.072 mSv
     B. 0.72 mSv
     C. 7.2 mSv
     D. 72 mSv
     E. 720 mSv

533. Which dosimetry protocol is most suitable for calibrating a 900 MeV proton beam in a soft tissue phantom?
     A. TG-21
     B. TG-51
     C. IAEA TRS-398
     D. AAPM TG-61
     E. TRS-483

534. What is the primary source of uncertainty in diamond-based nanodosimetry for verifying a carbon ion MRT plan?
     A. Energy dependence
     B. Detector alignment
     C. Spatial resolution
     D. Readout reproducibility
     E. Temperature sensitivity

535. What is the monitor unit (MU) correction factor for a 2 cm lung inhomogeneity (density=0.26 g/cm³, μ/ρ=0.03 cm²/g) and 3 cm bone inhomogeneity (density=1.85 g/cm³, μ/ρ=0.05 cm²/g) in a 35 MV photon beam at 30 cm depth?
     A. 0.90
     B. 0.95
     C. 1.00
     D. 1.05
     E. 1.10

536. Which dosimeter is most suitable for in-vivo dosimetry in a MR-guided carbon ion MRT setup?
     A. Ionisation chamber
     B. TLD
     C. Silicon diode
     D. MOSFET
     E. Plastic scintillator

537. What is the primary purpose of the collimator scatter factor (Sc) in proton FLASH dosimetry?
     A. To quantify phantom scatter
     B. To normalize dose for collimator settings
     C. To measure dose at depth
     D. To assess beam flatness
     E. To determine penumbra width

538. What is the approximate penumbra width (20%–80%) for a 900 MeV proton beam at 80 cm depth in water, considering nuclear interactions?
     A. 6 mm
     B. 8 mm
     C. 10 mm
     D. 12 mm
     E. 14 mm

539. Which factor most significantly affects the dose rate from a carbon ion MRT source at 600 Gy/s?
     A. Beam pulse frequency
     B. Source intensity
     C. Source energy
     D. Source material
     E. Source shape

540. What is the primary advantage of silicon nanowire detectors in proton FLASH dosimetry?
     A. High spatial resolution
     B. Radiation hardness
     C. Real-time readout
     D. Low cost
     E. Energy independence

Radiotherapy Treatment Planning (20 Questions)

541. What is the primary advantage of carbon ion MRT over proton FLASH therapy for hypoxic pancreatic tumours?
     A. Reduced treatment time
     B. Enhanced RBE in hypoxic regions
     C. Lower cost
     D. Increased scatter dose
     E. Simplified planning

542. Which parameter is most critical for defining the clinical target volume (CTV) in proton FLASH therapy for a lung tumour?
     A. Tumour size
     B. Microscopic disease extent
     C. Beam energy
     D. Field size
     E. Monitor units

543. What is the primary advantage of proton FLASH therapy over carbon ion MRT for superficial sarcomas?
     A. Uniform dose distribution
     B. Ultra-high dose rate sparing
     C. Increased treatment time
     D. Lower cost
     E. Simplified planning

544. Which dose calculation algorithm is most accurate for carbon ion MRT in a lung tumour with a 0.26 g/cm³ density heterogeneity?
     A. Pencil beam
     B. Convolution-superposition
     C. Monte Carlo
     D. Acuros XB
     E. Collapsed cone

545. What is the primary purpose of a multi-leaf collimator (MLC) in proton FLASH therapy?
     A. To increase beam energy
     B. To shape the radiation field
     C. To reduce skin sparing
     D. To monitor dose delivery
     E. To reduce scatter radiation

546. Which factor most significantly affects the distal dose fall-off in carbon ion MRT for a liver tumour?
     A. Beam energy
     B. Nuclear fragmentation tail
     C. Pulse duration
     D. Collimator shape
     E. Monitor units

547. What is the primary advantage of deep learning-based optimization in proton FLASH therapy planning?
     A. Reduced treatment time
     B. Adaptive plan optimization
     C. Lower cost
     D. Increased scatter dose
     E. Simplified planning

548. Which parameter is most critical for normal tissue complication probability (NTCP) in proton FLASH therapy (α/β=3 Gy)?
     A. Total dose
     B. Dose rate
     C. Beam energy
     D. Field size
     E. Monitor units

549. What is the primary purpose of a range modulator in carbon ion MRT?
     A. To increase beam energy
     B. To create a spread-out Bragg peak
     C. To shape the radiation field
     D. To monitor dose delivery
     E. To reduce scatter radiation

550. Which factor most significantly affects the dose conformity in carbon ion MRT for a brain tumour?
     A. Beamlet spacing
     B. Beam energy
     C. Field size
     D. Gantry angle
     E. Monitor units

551. What is the primary advantage of MRI-CT fusion in proton FLASH therapy planning?
     A. Reduced imaging time
     B. Enhanced tissue delineation
     C. Lower cost
     D. Increased scatter dose
     E. Simplified planning

552. Which structure is most critical for dose constraints in proton FLASH therapy for a pancreatic tumour?
     A. Spinal cord
     B. Duodenum
     C. Kidneys
     D. Heart
     E. Lungs

553. What is the primary purpose of a beam-specific range shifter in carbon ion MRT?
     A. To increase beam energy
     B. To adjust beam range
     C. To shape the radiation field
     D. To monitor dose delivery
     E. To reduce scatter radiation

554. Which factor most significantly affects the dose heterogeneity in carbon ion MRT for bulky sarcomas?
     A. Nuclear fragmentation
     B. Beam energy
     C. Field size
     D. Gantry angle
     E. Monitor units

555. What is the primary advantage of synthetic CT in carbon ion MRT planning?
     A. Reduced imaging time
     B. Accurate stopping power estimation
     C. Lower cost
     D. Increased scatter dose
     E. Simplified planning

556. Which parameter is most critical for tumour control probability (TCP) in carbon ion MRT?
     A. Tumour volume
     B. Peak-to-valley dose ratio
     C. Beam energy
     D. Field size
     E. Monitor units

557. What is the primary purpose of a compensator in proton FLASH therapy for a pelvic tumour?
     A. To increase beam energy
     B. To correct for tissue heterogeneity
     C. To shape the radiation field
     D. To monitor dose delivery
     E. To reduce scatter radiation

558. Which factor most significantly affects the dose distribution in proton FLASH therapy for ocular melanoma?
     A. Beamlet spacing
     B. Beam energy
     C. Field size
     D. Gantry angle
     E. Monitor units

559. What is the primary advantage of radiomics-guided planning in proton FLASH therapy?
     A. Reduced treatment time
     B. Targeting high-risk subvolumes
     C. Lower cost
     D. Increased scatter dose
     E. Simplified planning

560. Which parameter is most critical for dose-volume histogram (DVH) optimization in proton FLASH therapy?
     A. Beam energy
     B. Normal tissue constraints
     C. Field size
     D. Monitor units
     E. Collimator angle

Imaging (20 Questions)

561. What is the primary advantage of 15T MRI in radiotherapy planning for brain tumours?
     A. Ultra-high spatial resolution
     B. Low radiation dose
     C. Real-time imaging
     D. Electron density information
     E. Low cost

562. Which imaging modality is most suitable for assessing intrafraction motion in lung carbon ion MRT?
     A. CT
     B. MRI
     C. PET
     D. 4D-CT
     E. Fluoroscopy

563. What is the primary source of contrast in diffusion-weighted MRI for oncology?
     A. Proton density
     B. Water diffusion
     C. Electron density
     D. Atomic number
     E. Blood flow

564. Which factor most significantly affects the signal-to-noise ratio in spectral CT for carbon ion MRT planning?
     A. Detector quantum efficiency
     B. Tube voltage
     C. Reconstruction algorithm
     D. Field of view
     E. Gantry rotation speed

565. What is the primary advantage of At-211 PET in targeted alpha therapy planning?
     A. High spatial resolution
     B. Low radiation dose
     C. Alpha emitter tracking
     D. Real-time imaging
     E. Low cost

566. Which radionuclide is most suitable for imaging tumour hypoxia in proton FLASH therapy planning?
     A. F-18 (FMISO)
     B. Tc-99m
     C. Ga-68
     D. I-131
     E. Zr-89

567. What is the primary purpose of the contrast-to-noise ratio (CNR) in MR-guided carbon ion MRT?
     A. To measure radiation dose
     B. To quantify tissue differentiation
     C. To assess image noise
     D. To determine spatial resolution
     E. To monitor patient motion

568. Which factor most significantly affects the temporal resolution in 4D-CT for proton FLASH therapy?
     A. Gantry rotation speed
     B. Detector sensitivity
     C. Tube current
     D. Reconstruction algorithm
     E. Field of view

569. What is the primary advantage of dual-energy CT in proton FLASH therapy planning?
     A. High soft tissue contrast
     B. Improved stopping power estimation
     C. Low radiation dose
     D. Real-time imaging
     E. Low cost

570. Which imaging modality is most suitable for delineating pancreatic tumours in carbon ion MRT planning?
     A. CT
     B. MRI
     C. PET
     D. 4D-CT
     E. Ultrasound

571. What is the primary source of artefacts in 15T MRI for radiotherapy planning?
     A. Photon scattering
     B. B0 field inhomogeneity
     C. Metal implants
     D. Reconstruction algorithm
     E. Patient motion

572. Which factor most significantly affects the contrast resolution in dynamic contrast-enhanced (DCE) MRI for carbon ion MRT?
     A. Contrast agent dose
     B. Magnetic field strength
     C. Reconstruction algorithm
     D. Field of view
     E. Patient size

573. What is the primary advantage of MR spectroscopy in proton FLASH therapy planning?
     A. High spatial resolution
     B. Low radiation dose
     C. Metabolic tumour profiling
     D. Real-time imaging
     E. Low cost

574. Which imaging modality is most suitable for assessing liver tumour motion in proton FLASH therapy planning?
     A. CT
     B. MRI
     C. PET
     D. 4D-CT
     E. Ultrasound

575. What is the primary purpose of AI-based image segmentation in carbon ion MRT planning?
     A. To measure radiation dose
     B. To automate contouring
     C. To assess image contrast
     D. To determine spatial resolution
     E. To monitor image noise

576. Which factor most significantly affects the radiation dose in dual-energy CT for carbon ion MRT planning?
     A. Energy binning
     B. Tube current
     C. Reconstruction algorithm
     D. Field of view
     E. Gantry rotation speed

577. What is the primary advantage of hyperpolarized 13C MRI in proton FLASH therapy planning?
     A. High spatial resolution
     B. Metabolic tumour profiling
     C. Low radiation dose
     D. Real-time imaging
     E. Low cost

578. Which imaging modality is most suitable for real-time tumour tracking in carbon ion MRT?
     A. CT
     B. MRI
     C. PET
     D. Fluoroscopy
     E. Ultrasound

579. What is the primary source of contrast in chemical exchange saturation transfer (CEST) MRI for proton FLASH therapy?
     A. Proton density
     B. Molecular exchange
     C. Electron density
     D. Radiotracer uptake
     E. Tissue relaxation time

580. Which factor most significantly affects the spatial resolution in PET imaging for proton FLASH therapy planning?
     A. Detector crystal size
     B. Tube current
     C. Reconstruction algorithm
     D. Field of view
     E. Patient size

Radiation Protection (20 Questions)

581. What is the annual equivalent dose limit for the lens of the eye for radiation workers in the UK, per IRR 2017?
     A. 1 mSv
     B. 20 mSv
     C. 50 mSv
     D. 150 mSv
     E. 500 mSv

582. Which material is most effective for shielding 400 MeV neutrons in a carbon ion MRT facility?
     A. Lead
     B. Polyethylene with boron
     C. Perspex
     D. Steel
     E. Water

583. What is the primary purpose of the justification principle in IR(ME)R 2017 for carbon ion MRT?
     A. To maximize radiation dose
     B. To ensure clinical benefit
     C. To measure radiation dose
     D. To calibrate dosimeters
     E. To monitor radiation levels

584. Which factor most significantly affects the occupational dose in a proton FLASH therapy setup?
     A. Beam energy
     B. Neutron shielding design
     C. Field size
     D. Gantry angle
     E. Monitor units

585. What is the approximate tenth-value layer (TVL) for a 800 MeV/u carbon ion beam in concrete?
     A. 20 cm
     B. 30 cm
     C. 40 cm
     D. 50 cm
     E. 60 cm

586. Which type of personal dosimeter is most suitable for monitoring dose in a carbon ion MRT setup?
     A. Film badge
     B. TLD
     C. MOSFET
     D. OSL dosimeter
     E. Real-time scintillator

587. What is the primary source of stray radiation in a proton FLASH therapy treatment room?
     A. Primary beam
     B. Patient scatter
     C. Neutron contamination
     D. Bremsstrahlung radiation
     E. Compton scattering

588. Which regulation requires reporting of radiation incidents in a radiotherapy department in the UK?
     A. IRR 2017
     B. IR(ME)R 2017
     C. RIDDOR 2013
     D. COSHH 2002
     E. MHRA 2008

589. What is the dose rate at 3 meters from a 8 GBq At-211 source, given a specific gamma-ray constant of 0.04 R·m²/Ci·h, ignoring shielding?
     A. 0.1 mGy/h
     B. 1 mGy/h
     C. 10 mGy/h
     D. 100 mGy/h
     E. 1000 mGy/h

590. Which factor most significantly affects the shielding requirements for a proton FLASH therapy facility?
     A. Beam energy
     B. Neutron yield
     C. Field size
     D. Gantry angle
     E. Monitor units

591. What is the primary purpose of a radiation protection supervisor (RPS) in a proton FLASH therapy department?
     A. To deliver radiotherapy
     B. To oversee local safety compliance
     C. To calibrate dosimeters
     D. To monitor patient doses
     E. To perform quality assurance

592. Which material is most effective for shielding secondary X-rays in a carbon ion MRT bunker?
     A. Lead
     B. Concrete
     C. Polyethylene
     D. Boron
     E. Perspex

593. What is the annual effective dose limit for a pregnant radiation worker in the UK, per IRR 2017?
     A. 1 mSv
     B. 5 mSv
     C. 10 mSv
     D. 20 mSv
     E. 50 mSv

594. Which factor most significantly affects the dose to staff during At-211 targeted alpha therapy procedures?
     A. Source activity
     B. Shielding placement
     C. Field size
     D. Gantry angle
     E. Monitor units

595. What is the primary advantage of a lead-lined syringe in At-211 radionuclide therapy?
     A. Reduced treatment time
     B. Minimized gamma ray exposure
     C. Increased patient comfort
     D. Simplified quality assurance
     E. Enhanced dose delivery

596. Which type of radiation is most challenging to shield in a carbon ion MRT facility?
     A. Gamma rays
     B. X-rays
     C. Beta particles
     D. Neutrons
     E. Alpha particles

597. What is the primary purpose of a radiation safety audit in a carbon ion MRT department?
     A. To deliver radiotherapy
     B. To ensure regulatory compliance
     C. To calibrate dosimeters
     D. To monitor patient doses
     E. To perform quality assurance

598. Which factor most significantly affects the dose rate from an At-211 unsealed source?
     A. Source activity
     B. Alpha particle energy
     C. Source size
     D. Source material
     E. Source shape

599. What is the approximate half-life of At-211 used in targeted alpha therapy?
     A. 7 hours
     B. 7 days
     C. 2 days
     D. 12 hours
     E. 1 hour

600. Which principle is most critical for reducing public dose in a proton FLASH therapy facility?
     A. Time
     B. Distance
     C. Shielding
     D. Justification
     E. Calibration

Answers

Radiation Physics

501. D. At the distal edge of a 12 cm SOBP, a 600 MeV/u carbon ion has an LET of ~200 keV/μm in soft tissue due to increased stopping power.

502. D. Photonuclear reactions in lead produce neutrons for 35 MV photons (E > 7 MeV).

503. C. HVL = ln(2)/(μ·ρ) = 0.693/(0.04·2.35) ≈ 7.0 cm.

504. B. Ultra-fast radical recombination reduces OER in proton FLASH at 500 Gy/s.

505. C. CSDA range for 1.2 GeV protons in water = 83 cm in water / 1.00 ≈ 80 cm (R ∝ E¹·⁵).

506. B. LET and hypoxia interplay drives RBE variation (~4–6) in hypoxic chordoma.

507. C. L-to-K transition in tungsten emits ~70 keV photons (K-shell binding energy).

508. B. Photoelectric effect dominates at 5 keV in soft tissue, scaling as ∝ Z³.

509. D. Spallation reactions dominate for 200 MeV neutrons, producing cascades.

510. C. Mass stopping power ratio of bone to water is ~1.85 due to density (S ∝ ρ).

511. A. Target atomic number (low Z of graphite) enhances neutron production.

512. B. Dose rate = (Γ·A)/r² = (0.31·15/37)/(5²) ≈ 1 mGy/h (1 GBq = 27 mCi).

513. C. Compton scattering cross-section scales as ∝ 1/E for high-energy photons.

514. C. Range in aluminum = 70/2.70 ≈ 2.5 cm (R ≈ 0.5 E, adjusted for radiative losses).

515. B. Alpha particle emission is the primary energy deposition mode for At-211.

516. B. Nuclear fragmentation produces recoil energy in carbon ion beams.

517. B. Atomic number drives lateral dose spread via Coulomb scattering.

518. C. Pion production in beryllium requires ~300 MeV.

519. B. Polyethylene slows 300 MeV neutrons, and boron captures thermal neutrons.

520. B. Bremsstrahlung radiation dominates for 150 GeV electrons in copper (E > critical energy).

Dosimetry

521. B. Dose rate = (Γ·A)/r² = (0.11·10/37)/(4²) ≈ 0.3 mGy/h (1 GBq = 27 mCi).

522. A. Absorbed dose is critical for skin erythema (threshold ~2 Gy).

523. C. W_R for 300 MeV neutrons is 10 per ICRP 103.

524. C. PDD = 100 · e^(-μ·(d-dmax)) = 100 · e^(-0.025·(35-5)) ≈ 40%.

525. D. Silicon diodes offer sub-mm resolution for 0.01 mm² microbeam fields.

526. D. MU = Dose/(TMR·Output·CF), CF_lung = e^(0.03·3·(0.26-1)) ≈ 0.93, CF_bone = e^(0.05·2·(1.85-1)) ≈ 1.09, Total CF = 0.93·1.09 ≈ 1.01, MU = 7/(0.60·1.05·1.01) ≈ 1000 MU.

527. C. 800 MeV/u carbon ion range ~50 cm, 80% isodose at SOBP edge ~50 cm.

528. A. Detector charge collection efficiency affects nanodosimetry accuracy in 0.02 cm² fields.

529. B. Perovskite detectors offer ultra-fast response for carbon ion MRT dose rates.

530. B. TMR = PDD(d)/PDD(dmax) · BSF = 30/(100·1.07) ≈ 0.28.

531. D. Equivalent dose = 4 mGy · 2 (W_R for 200 MeV protons) = 8 mSv.

532. C. Effective dose = 6 mGy · 0.12 (W_T for lung) · 10 (W_R for neutrons) = 7.2 mSv.

533. C. IAEA TRS-398 is suitable for 900 MeV proton calibration.

534. B. Detector alignment is the primary uncertainty in diamond-based nanodosimetry.

535. B. CF_lung = e^(0.03·2·(0.26-1)) ≈ 0.96, CF_bone = e^(0.05·3·(1.85-1)) ≈ 1.14, Total CF = 0.96·1.14 ≈ 0.95.

536. C. Silicon diodes are MR-compatible for carbon ion MRT.

537. B. Collimator scatter factor normalizes dose for collimator settings in proton FLASH.

538. C. Penumbra width for 900 MeV protons at 80 cm is ~10 mm (scattering, nuclear interactions).

539. B. Source intensity drives dose rate in carbon ion MRT.

540. A. Silicon nanowire detectors offer high spatial resolution for proton FLASH dosimetry.

Radiotherapy Treatment Planning

541. B. Carbon ion MRT enhances RBE in hypoxic pancreatic tumours.

542. B. Microscopic disease extent is critical for lung CTV in proton FLASH.

543. B. Proton FLASH therapy offers ultra-high dose rate sparing for superficial sarcomas.

544. C. Monte Carlo is most accurate for carbon ion MRT in low-density lung.

545. B. MLCs shape the radiation field in proton FLASH.

546. B. Nuclear fragmentation tail affects distal dose fall-off in carbon ion MRT.

547. B. Deep learning optimizes adaptive plans in proton FLASH.

548. B. Dose rate drives NTCP in proton FLASH (α/β=3 Gy).

549. B. Range modulators create a spread-out Bragg peak in carbon ion MRT.

550. A. Beamlet spacing affects dose conformity in brain carbon ion MRT.

551. B. MRI-CT fusion enhances tissue delineation in proton FLASH.

552. B. Duodenum is critical for dose constraints in pancreatic proton FLASH.

553. B. Range shifters adjust beam range in carbon ion MRT.

554. A. Nuclear fragmentation causes dose heterogeneity in carbon ion MRT for sarcomas.

555. B. Synthetic CT ensures accurate stopping power in carbon ion MRT.

556. B. Peak-to-valley dose ratio drives TCP in carbon ion MRT.

557. B. Compensators correct for heterogeneity in pelvic proton FLASH.

558. A. Beamlet spacing determines dose distribution in ocular proton FLASH.

559. B. Radiomics-guided planning targets high-risk subvolumes in proton FLASH.

560. B. Normal tissue constraints drive DVH optimization in proton FLASH.

Imaging

561. A. 15T MRI provides ultra-high spatial resolution for brain tumour delineation.

562. B. MRI is suitable for lung intrafraction motion in carbon ion MRT.

563. B. Diffusion-weighted MRI contrast arises from water diffusion.

564. A. Detector quantum efficiency affects SNR in spectral CT.

565. C. At-211 PET tracks alpha emitters for targeted therapy planning.

566. A. F-18 (FMISO) is suitable for imaging tumour hypoxia.

567. B. CNR quantifies tissue differentiation in MR-guided carbon ion MRT.

568. A. Gantry rotation speed affects temporal resolution in 4D-CT.

569. B. Dual-energy CT improves stopping power estimation for proton FLASH.

570. B. MRI is ideal for delineating pancreatic tumours in carbon ion MRT.

571. B. B0 field inhomogeneity causes artefacts in 15T MRI.

572. A. Contrast agent dose affects contrast resolution in DCE-MRI.

573. C. MR spectroscopy profiles tumour metabolism in proton FLASH.

574. B. MRI is suitable for assessing liver tumour motion in proton FLASH.

575. B. AI-based image segmentation automates contouring in carbon ion MRT.

576. B. Tube current affects radiation dose in dual-energy CT.

577. B. Hyperpolarized 13C MRI profiles tumour metabolism for proton FLASH.

578. B. MRI enables real-time tumour tracking in carbon ion MRT.

579. B. CEST MRI contrast arises from molecular exchange via proton transfer.

580. A. Detector crystal size affects PET spatial resolution.

Radiation Protection

581. B. The annual equivalent dose limit for the lens is 20 mSv (IRR 2017).

582. B. Polyethylene with boron shields 400 MeV neutrons effectively.

583. B. Justification in IR(ME)R 2017 ensures clinical benefit in carbon ion MRT.

584. B. Neutron shielding design most significantly affects dose in proton FLASH.

585. D. TVL for 800 MeV/u carbon ions in concrete is ~50 cm (high density).

586. E. Real-time scintillators are suitable for carbon ion MRT due to high dose rates.

587. C. Neutron contamination is the primary stray radiation in proton FLASH.

588. B. IR(ME)R 2017 requires reporting radiation incidents in radiotherapy.

589. B. Dose rate = (Γ·A)/r² = (0.04·8/37)/(3²) ≈ 1 mGy/h (1 GBq = 27 mCi).

590. B. Neutron yield drives shielding requirements for proton FLASH facilities.

591. B. RPS oversees local safety compliance in proton FLASH.

592. A. Lead is most effective for shielding secondary X-rays.

593. A. The annual effective dose limit for a pregnant worker is 1 mSv (IRR 2017).

594. B. Shielding placement most significantly affects staff dose in At-211 therapy.

595. B. Lead-lined syringes minimize gamma ray exposure in At-211 therapy.

596. D. Neutrons are most challenging to shield in carbon ion MRT facilities.

597. B. Radiation safety audits ensure regulatory compliance in carbon ion MRT.

598. A. Source activity drives the dose rate from At-211 (alpha/gamma emitter).

599. A. The half-life of At-211 is ~7 hours.

600. C. Shielding is critical for reducing public dose in proton FLASH facilities.

Radiation Physics (20 Questions)

601. What is the approximate linear energy transfer (LET) of a 900 MeV/u carbon ion at the proximal edge of a 10 cm SOBP in bone (density 1.85 g/cm³), accounting for nuclear fragmentation?
     A. 50 keV/μm
     B. 100 keV/μm
     C. 150 keV/μm
     D. 200 keV/μm
     E. 250 keV/μm

602. For a 50 MV photon beam interacting with a graphite target in a proton arc therapy setup, what is the dominant interaction process contributing to secondary pion production?
     A. Photoelectric effect
     B. Compton scattering
     C. Pair production
     D. Photonuclear reactions
     E. Coherent scattering

603. Calculate the half-value layer (HVL) for a 40 MV photon beam in concrete, given a mass attenuation coefficient of 0.035 cm²/g and density of 2.35 g/cm³.
     A. 6.0 cm
     B. 7.0 cm
     C. 8.0 cm
     D. 9.0 cm
     E. 10.0 cm

604. In a proton FLASH radiotherapy setup with 300 MeV protons at 400 Gy/s, what is the primary mechanism reducing the oxygen enhancement ratio (OER) in a hypoxic chordoma?
     A. Enhanced nuclear interactions
     B. Ultra-fast radical recombination
     C. Reduced Compton scattering
     D. Increased bremsstrahlung yield
     E. Altered pair production

605. What is the continuous slowing down approximation (CSDA) range of a 1.5 GeV proton in soft tissue (density 1.04 g/cm³), accounting for nuclear interactions?
     A. 80 cm
     B. 90 cm
     C. 100 cm
     D. 110 cm
     E. 120 cm

606. Which factor most significantly affects the relative biological effectiveness (RBE) variation in a 800 MeV/u carbon ion beam for a hypoxic osteosarcoma?
     A. Beam energy spread
     B. LET and hypoxia interplay
     C. Beam divergence
     D. Nuclear fragmentation tail
     E. Collimator material

607. What is the energy of a characteristic X-ray emitted from the N-shell to K-shell transition in iridium (Z=77)?
     A. 60 keV
     B. 80 keV
     C. 100 keV
     D. 120 keV
     E. 140 keV

608. For a 8 keV photon beam in lung tissue, what is the dominant interaction, and how does its cross-section scale with atomic number (Z)?
     A. Compton scattering, Z-independent
     B. Photoelectric effect, ∝ Z³
     C. Pair production, ∝ Z²
     D. Coherent scattering, ∝ Z
     E. Photodisintegration, ∝ Z⁴

609. What is the primary interaction mechanism for 300 MeV neutrons in soft tissue, considering secondary particle cascades?
     A. Elastic scattering with protons
     B. Inelastic scattering with oxygen
     C. Neutron capture by nitrogen
     D. Spallation reactions
     E. Compton scattering

610. What is the mass stopping power ratio of bone to water for a 70 MeV electron beam, considering density effects (bone: 1.85 g/cm³, water: 1.00 g/cm³)?
     A. 1.50
     B. 1.65
     C. 1.85
     D. 2.00
     E. 2.20

611. Which factor most significantly affects the production of secondary neutrons in a 600 MeV proton beam interacting with a beryllium range shifter?
     A. Target atomic number
     B. Nuclear excitation
     C. Collimator thickness
     D. Beam current
     E. Gantry angle

612. What is the dose rate at 8 meters from a 20 GBq Co-60 source, given a specific gamma-ray constant of 0.31 R·m²/Ci·h, ignoring shielding and assuming air kerma?
     A. 0.05 mGy/h
     B. 0.5 mGy/h
     C. 5 mGy/h
     D. 50 mGy/h
     E. 500 mGy/h

613. Which equation correctly describes the energy dependence of the bremsstrahlung cross-section for ultra-high-energy electrons (>100 MeV)?
     A. ∝ E
     B. ∝ E²
     C. ∝ 1/E
     D. ∝ 1/E²
     E. ∝ ln(E)

614. What is the approximate range of a 80 MeV electron in titanium (density 4.54 g/cm³), accounting for radiative losses?
     A. 1.0 cm
     B. 1.5 cm
     C. 2.0 cm
     D. 2.5 cm
     E. 3.0 cm

615. In a targeted alpha therapy using Ac-225, what is the primary mode of energy deposition in metastatic tumour cells?
     A. Bremsstrahlung radiation
     B. Alpha particle emission
     C. Gamma ray emission
     D. Compton scattering
     E. Photoelectric effect

616. What is the primary source of nuclear recoil energy in a 900 MeV/u carbon ion beam interacting with a hypoxic sarcoma?
     A. Elastic scattering
     B. Nuclear fragmentation
     C. Compton scattering
     D. Pair production
     E. Bremsstrahlung radiation

617. Which material property most significantly affects the lateral dose spread of a 1 GeV proton beam in a silicon-based bolus?
     A. Electron density
     B. Atomic number
     C. Mass density
     D. Thermal conductivity
     E. Magnetic susceptibility

618. What is the approximate energy threshold for kaon production in a proton beam interacting with a graphite target?
     A. 1 GeV
     B. 1.5 GeV
     C. 2 GeV
     D. 2.5 GeV
     E. 3 GeV

619. Which shielding configuration is most effective for 400 MeV neutrons in a carbon ion MRT facility?
     A. Lead followed by paraffin
     B. Polyethylene followed by boron
     C. Steel followed by concrete
     D. Water followed by cadmium
     E. Concrete followed by hydrogen-rich material

620. What is the primary mode of energy loss for a 200 GeV electron in lead, considering synchrotron radiation effects?
     A. Collisional interactions
     B. Bremsstrahlung radiation
     C. Compton scattering
     D. Pair production
     E. Synchrotron radiation

Dosimetry (20 Questions)

621. What is the absorbed dose rate at 6 meters from a 15 GBq Cs-137 source, given a specific gamma-ray constant of 0.11 R·m²/Ci·h, ignoring shielding?
     A. 0.04 mGy/h
     B. 0.4 mGy/h
     C. 4 mGy/h
     D. 40 mGy/h
     E. 400 mGy/h

622. Which quantity is most critical for assessing the risk of radiation-induced cataracts in proton FLASH therapy?
     A. Absorbed dose
     B. Equivalent dose
     C. Effective dose
     D. Kerma
     E. Exposure

623. What is the radiation weighting factor (W_R) for 400 MeV neutrons in radiation protection, per ICRP 103?
     A. 2
     B. 5
     C. 10
     D. 20
     E. 50

624. What is the percentage depth dose (PDD) at 40 cm depth for a 40 MV photon beam (10x10 cm² field, SSD=100 cm) in water, given a PDD of 100% at dmax=5.5 cm and an attenuation coefficient of 0.02 cm⁻¹?
     A. 25%
     B. 30%
     C. 35%
     D. 40%
     E. 45%

625. Which dosimeter is most suitable for measuring dose in a 0.008 mm² microbeam radiotherapy field with 400 keV X-rays?
     A. Ionisation chamber
     B. TLD
     C. Nanodot OSL
     D. Silicon nanowire detector
     E. Radiochromic film

626. What is the monitor unit (MU) required to deliver 8 Gy to a depth of 30 cm through a 4 cm lung slab (density=0.26 g/cm³, μ/ρ=0.03 cm²/g) and 3 cm bone slab (density=1.85 g/cm³, μ/ρ=0.05 cm²/g) for a 40 MV photon beam (10x10 cm² field, SAD=100 cm, output factor=1.06, TMR=0.55)?
     A. 800 MU
     B. 900 MU
     C. 1000 MU
     D. 1100 MU
     E. 1200 MU

627. What is the approximate depth of the 85% isodose line for a 900 MeV/u carbon ion beam in water, assuming a 12 cm SOBP?
     A. 45 cm
     B. 50 cm
     C. 55 cm
     D. 60 cm
     E. 65 cm

628. Which factor most significantly affects the accuracy of nanodosimetry in a 0.015 cm² field for carbon ion MRT?
     A. Detector charge collection efficiency
     B. Beam energy spread
     C. Source-to-detector distance
     D. Collimator misalignment
     E. Nuclear fragmentation

629. What is the primary advantage of quantum dot detectors in proton FLASH dosimetry?
     A. High spatial resolution
     B. Ultra-fast response time
     C. Low cost
     D. Energy independence
     E. Large dynamic range

630. What is the tissue maximum ratio (TMR) at 45 cm depth for a 40 MV photon beam (10x10 cm² field, SAD=100 cm), given a PDD of 25% at 45 cm, PDD of 100% at dmax=5.5 cm, and BSF of 1.08?
     A. 0.20
     B. 0.23
     C. 0.26
     D. 0.29
     E. 0.32

631. What is the equivalent dose from a 5 mGy absorbed dose of 300 MeV protons to the lens of the eye?
     A. 0.05 mSv
     B. 0.5 mSv
     C. 5 mSv
     D. 10 mSv
     E. 50 mSv

632. What is the effective dose from a 7 mGy absorbed dose to the liver (tissue weighting factor=0.04) from 400 MeV neutrons (W_R=10)?
     A. 0.028 mSv
     B. 0.28 mSv
     C. 2.8 mSv
     D. 28 mSv
     E. 280 mSv

633. Which dosimetry protocol is most suitable for calibrating a 1 GeV proton beam in a bone phantom?
     A. TG-21
     B. TG-51
     C. IAEA TRS-398
     D. AAPM TG-61
     E. TRS-483

634. What is the primary source of uncertainty in graphene-based nanodosimetry for verifying a proton FLASH therapy plan?
     A. Energy dependence
     B. Detector alignment
     C. Spatial resolution
     D. Readout reproducibility
     E. Temperature sensitivity

635. What is the monitor unit (MU) correction factor for a 3 cm lung inhomogeneity (density=0.26 g/cm³, μ/ρ=0.03 cm²/g) and 4 cm bone inhomogeneity (density=1.85 g/cm³, μ/ρ=0.05 cm²/g) in a 40 MV photon beam at 35 cm depth?
     A. 0.90
     B. 0.95
     C. 1.00
     D. 1.05
     E. 1.10

636. Which dosimeter is most suitable for in-vivo dosimetry in a MR-guided proton FLASH therapy setup?
     A. Ionisation chamber
     B. TLD
     C. Silicon nanowire detector
     D. MOSFET
     E. Plastic scintillator

637. What is the primary purpose of the collimator scatter factor (Sc) in carbon ion MRT dosimetry?
     A. To quantify phantom scatter
     B. To normalize dose for collimator settings
     C. To measure dose at depth
     D. To assess beam flatness
     E. To determine penumbra width

638. What is the approximate penumbra width (20%–80%) for a 1 GeV proton beam at 90 cm depth in water, considering nuclear interactions?
     A. 7 mm
     B. 9 mm
     C. 11 mm
     D. 13 mm
     E. 15 mm

639. Which factor most significantly affects the dose rate from a proton FLASH therapy source at 500 Gy/s?
     A. Beam pulse frequency
     B. Source intensity
     C. Source energy
     D. Source material
     E. Source shape

640. What is the primary advantage of diamond detectors in carbon ion MRT dosimetry?
     A. High spatial resolution
     B. Radiation hardness
     C. Real-time readout
     D. Low cost
     E. Energy independence

Radiotherapy Treatment Planning (20 Questions)

641. What is the primary advantage of proton FLASH therapy over carbon ion MRT for superficial skin cancers?
     A. Reduced treatment time
     B. Ultra-high dose rate sparing
     C. Lower cost
     D. Increased scatter dose
     E. Simplified planning

642. Which parameter is most critical for defining the clinical target volume (CTV) in carbon ion MRT for a pancreatic tumour?
     A. Tumour size
     B. Microscopic disease extent
     C. Beam energy
     D. Field size
     E. Monitor units

643. What is the primary advantage of carbon ion MRT over proton FLASH therapy for hypoxic gliomas?
     A. Uniform dose distribution
     B. Enhanced RBE in hypoxic regions
     C. Increased treatment time
     D. Lower cost
     E. Simplified planning

644. Which dose calculation algorithm is most accurate for proton FLASH therapy in a bone tumour with a 1.85 g/cm³ density heterogeneity?
     A. Pencil beam
     B. Convolution-superposition
     C. Monte Carlo
     D. Acuros XB
     E. Collapsed cone

645. What is the primary purpose of a multi-leaf collimator (MLC) in carbon ion MRT?
     A. To increase beam energy
     B. To shape the radiation field
     C. To reduce skin sparing
     D. To monitor dose delivery
     E. To reduce scatter radiation

646. Which factor most significantly affects the distal dose fall-off in proton FLASH therapy for a brain tumour?
     A. Beam energy
     B. Nuclear fragmentation tail
     C. Pulse duration
     D. Collimator shape
     E. Monitor units

647. What is the primary advantage of reinforcement learning-based optimization in carbon ion MRT planning?
     A. Reduced treatment time
     B. Adaptive plan optimization
     C. Lower cost
     D. Increased scatter dose
     E. Simplified planning

648. Which parameter is most critical for normal tissue complication probability (NTCP) in carbon ion MRT (α/β=3 Gy)?
     A. Total dose
     B. Peak-to-valley dose ratio
     C. Beam energy
     D. Field size
     E. Monitor units

649. What is the primary purpose of a range modulator in proton FLASH therapy?
     A. To increase beam energy
     B. To create a spread-out Bragg peak
     C. To shape the radiation field
     D. To monitor dose delivery
     E. To reduce scatter radiation

650. Which factor most significantly affects the dose conformity in proton FLASH therapy for a spinal tumour?
     A. Beamlet spacing
     B. Beam energy
     C. Field size
     D. Gantry angle
     E. Monitor units

651. What is the primary advantage of CT-MRI fusion in carbon ion MRT planning?
     A. Reduced imaging time
     B. Enhanced tissue delineation
     C. Lower cost
     D. Increased scatter dose
     E. Simplified planning

652. Which structure is most critical for dose constraints in carbon ion MRT for a liver tumour?
     A. Spinal cord
     B. Stomach
     C. Kidneys
     D. Heart
     E. Lungs

653. What is the primary purpose of a beam-specific range shifter in proton FLASH therapy?
     A. To increase beam energy
     B. To adjust beam range
     C. To shape the radiation field
     D. To monitor dose delivery
     E. To reduce scatter radiation

654. Which factor most significantly affects the dose heterogeneity in proton FLASH therapy for bulky sarcomas?
     A. Pulse structure
     B. Beam energy
     C. Field size
     D. Gantry angle
     E. Monitor units

655. What is the primary advantage of machine learning-based synthetic CT in proton FLASH planning?
     A. Reduced imaging time
     B. Accurate stopping power estimation
     C. Lower cost
     D. Increased scatter dose
     E. Simplified planning

656. Which parameter is most critical for tumour control probability (TCP) in proton FLASH therapy?
     A. Tumour volume
     B. Dose rate
     C. Beam energy
     D. Field size
     E. Monitor units

657. What is the primary purpose of a compensator in carbon ion MRT for a pelvic tumour?
     A. To increase beam energy
     B. To correct for tissue heterogeneity
     C. To shape the radiation field
     D. To monitor dose delivery
     E. To reduce scatter radiation

658. Which factor most significantly affects the dose distribution in carbon ion MRT for ocular melanoma?
     A. Beamlet spacing
     B. Beam energy
     C. Field size
     D. Gantry angle
     E. Monitor units

659. What is the primary advantage of radiomics-guided dose escalation in carbon ion MRT?
     A. Reduced treatment time
     B. Targeting high-risk subvolumes
     C. Lower cost
     D. Increased scatter dose
     E. Simplified planning

660. Which parameter is most critical for dose-volume histogram (DVH) optimization in carbon ion MRT?
     A. Beam energy
     B. Normal tissue constraints
     C. Field size
     D. Monitor units
     E. Collimator angle

Imaging (20 Questions)

661. What is the primary advantage of 18T MRI in radiotherapy planning for pancreatic tumours?
     A. Ultra-high spatial resolution
     B. Low radiation dose
     C. Real-time imaging
     D. Electron density information
     E. Low cost

662. Which imaging modality is most suitable for assessing intrafraction motion in liver carbon ion MRT?
     A. CT
     B. MRI
     C. PET
     D. 4D-CT
     E. Fluoroscopy

663. What is the primary source of contrast in sodium MRI for oncology?
     A. Proton density
     B. Sodium concentration
     C. Electron density
     D. Atomic number
     E. Blood flow

664. Which factor most significantly affects the signal-to-noise ratio in photon-counting CT for proton FLASH planning?
     A. Detector quantum efficiency
     B. Tube voltage
     C. Reconstruction algorithm
     D. Field of view
     E. Gantry rotation speed

665. What is the primary advantage of Ac-225 PET in targeted alpha therapy planning?
     A. High spatial resolution
     B. Low radiation dose
     C. Alpha emitter tracking
     D. Real-time imaging
     E. Low cost

666. Which radionuclide is most suitable for imaging tumour hypoxia in carbon ion MRT planning?
     A. F-18 (FMISO)
     B. Tc-99m
     C. Ga-68
     D. I-131
     E. Zr-89

667. What is the primary purpose of the contrast-to-noise ratio (CNR) in MR-guided proton FLASH therapy?
     A. To measure radiation dose
     B. To quantify tissue differentiation
     C. To assess image noise
     D. To determine spatial resolution
     E. To monitor patient motion

668. Which factor most significantly affects the temporal resolution in 4D-MRI for carbon ion MRT?
     A. Field strength
     B. Gradient slew rate
     C. Coil sensitivity
     D. Reconstruction algorithm
     E. Field of view

669. What is the primary advantage of spectral CT in carbon ion MRT planning?
     A. High soft tissue contrast
     B. Material-specific imaging
     C. Low radiation dose
     D. Real-time imaging
     E. Low cost

670. Which imaging modality is most suitable for delineating brain tumours in proton FLASH therapy planning?
     A. CT
     B. MRI
     C. PET
     D. 4D-CT
     E. Ultrasound

671. What is the primary source of artefacts in 18T MRI for radiotherapy planning?
     A. Photon scattering
     B. B0 field inhomogeneity
     C. Metal implants
     D. Reconstruction algorithm
     E. Patient motion

672. Which factor most significantly affects the contrast resolution in dynamic contrast-enhanced (DCE) MRI for proton FLASH therapy?
     A. Contrast agent dose
     B. Magnetic field strength
     C. Reconstruction algorithm
     D. Field of view
     E. Patient size

673. What is the primary advantage of MR elastography in carbon ion MRT planning?
     A. High spatial resolution
     B. Low radiation dose
     C. Assessment of tissue stiffness
     D. Real-time imaging
     E. Low cost

674. Which imaging modality is most suitable for assessing oesophageal tumour motion in carbon ion MRT planning?
     A. CT
     B. MRI
     C. PET
     D. 4D-CT
     E. Ultrasound

675. What is the primary purpose of AI-based image segmentation in proton FLASH therapy?
     A. To measure radiation dose
     B. To automate contouring
     C. To assess image contrast
     D. To determine spatial resolution
     E. To monitor image noise

676. Which factor most significantly affects the radiation dose in spectral CT for proton FLASH planning?
     A. Energy thresholding
     B. Tube current
     C. Reconstruction algorithm
     D. Field of view
     E. Gantry rotation speed

677. What is the primary advantage of hyperpolarized 13C MRI in carbon ion MRT planning?
     A. High spatial resolution
     B. Metabolic tumour profiling
     C. Low radiation dose
     D. Real-time imaging
     E. Low cost

678. Which imaging modality is most suitable for real-time tumour tracking in proton FLASH therapy?
     A. CT
     B. MRI
     C. PET
     D. Fluoroscopy
     E. Ultrasound

679. What is the primary source of contrast in amide proton transfer (APT) MRI for carbon ion MRT?
     A. Proton density
     B. Protein content
     C. Electron density
     D. Radiotracer uptake
     E. Tissue relaxation time

680. Which factor most significantly affects the spatial resolution in PET imaging for carbon ion MRT planning?
     A. Detector crystal size
     B. Tube current
     C. Reconstruction algorithm
     D. Field of view
     E. Patient size

Radiation Protection (20 Questions)

681. What is the annual equivalent dose limit for the lens of the eye for radiation workers in the UK, per IRR 2017?
     A. 1 mSv
     B. 20 mSv
     C. 50 mSv
     D. 150 mSv
     E. 500 mSv

682. Which material is most effective for shielding 500 MeV neutrons in a proton FLASH therapy facility?
     A. Lead
     B. Polyethylene with boron
     C. Perspex
     D. Steel
     E. Water

683. What is the primary purpose of the justification principle in IR(ME)R 2017 for proton FLASH therapy?
     A. To maximize radiation dose
     B. To ensure clinical benefit
     C. To measure radiation dose
     D. To calibrate dosimeters
     E. To monitor radiation levels

684. Which factor most significantly affects the occupational dose in a carbon ion MRT setup?
     A. Beam energy
     B. Neutron shielding design
     C. Field size
     D. Gantry angle
     E. Monitor units

685. What is the approximate tenth-value layer (TVL) for a 900 MeV/u carbon ion beam in concrete?
     A. 30 cm
     B. 40 cm
     C. 50 cm
     D. 60 cm
     E. 70 cm

686. Which type of personal dosimeter is most suitable for monitoring dose in a proton FLASH therapy setup?
     A. Film badge
     B. TLD
     C. MOSFET
     D. OSL dosimeter
     E. Real-time scintillator

687. What is the primary source of stray radiation in a carbon ion MRT treatment room?
     A. Primary beam
     B. Patient scatter
     C. Neutron contamination
     D. Bremsstrahlung radiation
     E. Compton scattering

688. Which regulation requires reporting of radiation overexposures in a radiotherapy department in the UK?
     A. IRR 2017
     B. IR(ME)R 2017
     C. RIDDOR 2013
     D. COSHH 2002
     E. MHRA 2008

689. What is the dose rate at 4 meters from a 12 GBq Ac-225 source, given a specific gamma-ray constant of 0.03 R·m²/Ci·h, ignoring shielding?
     A. 0.1 mGy/h
     B. 1 mGy/h
     C. 10 mGy/h
     D. 100 mGy/h
     E. 1000 mGy/h

690. Which factor most significantly affects the shielding requirements for a proton FLASH therapy facility?
     A. Beam energy
     B. Neutron yield
     C. Field size
     D. Gantry angle
     E. Monitor units

691. What is the primary purpose of a radiation protection supervisor (RPS) in a carbon ion MRT department?
     A. To deliver radiotherapy
     B. To oversee local safety compliance
     C. To calibrate dosimeters
     D. To monitor patient doses
     E. To perform quality assurance

692. Which material is most effective for shielding secondary X-rays in a proton FLASH therapy bunker?
     A. Lead
     B. Concrete
     C. Polyethylene
     D. Boron
     E. Perspex

693. What is the annual effective dose limit for a pregnant radiation worker in the UK, per IRR 2017?
     A. 1 mSv
     B. 5 mSv
     C. 10 mSv
     D. 20 mSv
     E. 50 mSv

694. Which factor most significantly affects the dose to staff during Ac-225 targeted alpha therapy procedures?
     A. Source activity
     B. Shielding placement
     C. Field size
     D. Gantry angle
     E. Monitor units

695. What is the primary advantage of a lead-lined glove in Ac-225 radionuclide therapy?
     A. Reduced treatment time
     B. Minimized gamma ray exposure
     C. Increased patient comfort
     D. Simplified quality assurance
     E. Enhanced dose delivery

696. Which type of radiation is most challenging to shield in a proton FLASH therapy facility?
     A. Gamma rays
     B. X-rays
     C. Beta particles
     D. Neutrons
     E. Alpha particles

697. What is the primary purpose of a radiation safety audit in a proton FLASH therapy department?
     A. To deliver radiotherapy
     B. To ensure regulatory compliance
     C. To calibrate dosimeters
     D. To monitor patient doses
     E. To perform quality assurance

698. Which factor most significantly affects the dose rate from an Ac-225 unsealed source?
     A. Source activity
     B. Alpha particle energy
     C. Source size
     D. Source material
     E. Source shape

699. What is the approximate half-life of Ac-225 used in targeted alpha therapy?
     A. 10 days
     B. 7 days
     C. 2 days
     D. 12 hours
     E. 1 hour

700. Which principle is most critical for reducing public dose in a carbon ion MRT facility?
     A. Time
     B. Distance
     C. Shielding
     D. Justification
     E. Calibration

Answers

Radiation Physics

601. B. At the proximal edge of a 10 cm SOBP, a 900 MeV/u carbon ion has an LET of ~100 keV/μm in bone, adjusted for fragmentation.

602. D. Photonuclear reactions in graphite produce pions for 50 MV photons (E > 140 MeV).

603. C. HVL = ln(2)/(μ·ρ) = 0.693/(0.035·2.35) ≈ 8.0 cm.

604. B. Ultra-fast radical recombination reduces OER in proton FLASH at 400 Gy/s.

605. C. CSDA range for 1.5 GeV protons in soft tissue = 104 cm in water / 1.04 ≈ 100 cm (R ∝ E¹·⁵).

606. B. LET and hypoxia interplay drives RBE variation (~5–7) in hypoxic osteosarcoma.

607. B. N-to-K transition in iridium emits ~80 keV photons (K-shell binding energy).

608. B. Photoelectric effect dominates at 8 keV in lung tissue, scaling as ∝ Z³.

609. D. Spallation reactions dominate for 300 MeV neutrons, producing cascades.

610. C. Mass stopping power ratio of bone to water is ~1.85 due to density (S ∝ ρ).

611. A. Target atomic number (low Z of beryllium) enhances neutron production.

612. B. Dose rate = (Γ·A)/r² = (0.31·20/37)/(8²) ≈ 0.5 mGy/h (1 GBq = 27 mCi).

613. C. Bremsstrahlung cross-section scales as ∝ 1/E for ultra-high energies.

614. C. Range in titanium = 80/4.54 ≈ 2.0 cm (R ≈ 0.5 E, adjusted for radiative losses).

615. B. Alpha particle emission is the primary energy deposition mode for Ac-225.

616. B. Nuclear fragmentation produces recoil energy in carbon ion beams.

617. B. Atomic number drives lateral dose spread via Coulomb scattering.

618. B. Kaon production in graphite requires ~1.5 GeV.

619. B. Polyethylene slows 400 MeV neutrons, and boron captures thermal neutrons.

620. B. Bremsstrahlung radiation dominates for 200 GeV electrons in lead (E > critical energy).

Dosimetry

621. B. Dose rate = (Γ·A)/r² = (0.11·15/37)/(6²) ≈ 0.4 mGy/h (1 GBq = 27 mCi).

622. B. Equivalent dose assesses cataract risk to the lens (W_R-dependent).

623. C. W_R for 400 MeV neutrons is 10 per ICRP 103.

624. C. PDD = 100 · e^(-μ·(d-dmax)) = 100 · e^(-0.02·(40-5.5)) ≈ 35%.

625. D. Silicon nanowire detectors offer sub-μm resolution for 0.008 mm² microbeam fields.

626. D. MU = Dose/(TMR·Output·CF), CF_lung = e^(0.03·4·(0.26-1)) ≈ 0.91, CF_bone = e^(0.05·3·(1.85-1)) ≈ 1.14, Total CF = 0.91·1.14 ≈ 1.04, MU = 8/(0.55·1.06·1.04) ≈ 1100 MU.

627. B. 900 MeV/u carbon ion range ~60 cm, 85% isodose at SOBP center ~50 cm.

628. A. Detector charge collection efficiency affects nanodosimetry accuracy in 0.015 cm² fields.

629. B. Quantum dot detectors offer ultra-fast response for proton FLASH dose rates.

630. B. TMR = PDD(d)/PDD(dmax) · BSF = 25/(100·1.08) ≈ 0.23.

631. D. Equivalent dose = 5 mGy · 2 (W_R for 300 MeV protons) = 10 mSv.

632. C. Effective dose = 7 mGy · 0.04 (W_T for liver) · 10 (W_R for neutrons) = 2.8 mSv.

633. C. IAEA TRS-398 is suitable for 1 GeV proton calibration.

634. B. Detector alignment is the primary uncertainty in graphene-based nanodosimetry.

635. B. CF_lung = e^(0.03·3·(0.26-1)) ≈ 0.94, CF_bone = e^(0.05·4·(1.85-1)) ≈ 1.18, Total CF = 0.94·1.18 ≈ 0.95.

636. C. Silicon nanowire detectors are MR-compatible for proton FLASH.

637. B. Collimator scatter factor normalizes dose for collimator settings in carbon ion MRT.

638. C. Penumbra width for 1 GeV protons at 90 cm is ~11 mm (scattering, nuclear interactions).

639. B. Source intensity drives dose rate in proton FLASH therapy.

640. B. Diamond detectors offer radiation hardness for carbon ion MRT dosimetry.

Radiotherapy Treatment Planning

641. B. Proton FLASH therapy offers ultra-high dose rate sparing for superficial cancers.

642. B. Microscopic disease extent is critical for pancreatic CTV in carbon ion MRT.

643. B. Carbon ion MRT enhances RBE in hypoxic gliomas.

644. C. Monte Carlo is most accurate for proton FLASH in high-density bone.

645. B. MLCs shape the radiation field in carbon ion MRT.

646. B. Nuclear fragmentation tail affects distal dose fall-off in proton FLASH.

647. B. Reinforcement learning optimizes adaptive plans in carbon ion MRT.

648. B. Peak-to-valley dose ratio drives NTCP in carbon ion MRT (α/β=3 Gy).

649. B. Range modulators create a spread-out Bragg peak in proton FLASH.

650. A. Beamlet spacing affects dose conformity in spinal proton FLASH.

651. B. CT-MRI fusion enhances tissue delineation in carbon ion MRT.

652. B. Stomach is critical for dose constraints in liver carbon ion MRT.

653. B. Range shifters adjust beam range in proton FLASH.

654. A. Pulse structure causes dose heterogeneity in proton FLASH for sarcomas.

655. B. Synthetic CT ensures accurate stopping power in proton FLASH.

656. B. Dose rate drives TCP in proton FLASH therapy.

657. B. Compensators correct for heterogeneity in pelvic carbon ion MRT.

658. A. Beamlet spacing determines dose distribution in ocular carbon ion MRT.

659. B. Radiomics-guided dose escalation targets high-risk subvolumes in carbon ion MRT.

660. B. Normal tissue constraints drive DVH optimization in carbon ion MRT.

Imaging

661. A. 18T MRI provides ultra-high spatial resolution for pancreatic tumour delineation.

662. B. MRI is suitable for liver intrafraction motion in carbon ion MRT.

663. B. Sodium MRI contrast arises from sodium concentration.

664. A. Detector quantum efficiency affects SNR in photon-counting CT.

665. C. Ac-225 PET tracks alpha emitters for targeted therapy planning.

666. A. F-18 (FMISO) is suitable for imaging tumour hypoxia.

667. B. CNR quantifies tissue differentiation in MR-guided proton FLASH.

668. B. Gradient slew rate affects temporal resolution in 4D-MRI.

669. B. Spectral CT enables material-specific imaging for carbon ion MRT planning.

670. B. MRI is ideal for delineating brain tumours in proton FLASH.

671. B. B0 field inhomogeneity causes artefacts in 18T MRI.

672. A. Contrast agent dose affects contrast resolution in DCE-MRI.

673. C. MR elastography assesses tissue stiffness in carbon ion MRT planning.

674. B. MRI is suitable for assessing oesophageal tumour motion in carbon ion MRT.

675. B. AI-based image segmentation automates contouring in proton FLASH.

676. B. Tube current affects radiation dose in spectral CT.

677. B. Hyperpolarized 13C MRI profiles tumour metabolism for carbon ion MRT.

678. B. MRI enables real-time tumour tracking in proton FLASH.

679. B. APT MRI contrast arises from protein content via amide proton exchange.

680. A. Detector crystal size affects PET spatial resolution.

Radiation Protection

681. B. The annual equivalent dose limit for the lens is 20 mSv (IRR 2017).

682. B. Polyethylene with boron shields 500 MeV neutrons effectively.

683. B. Justification in IR(ME)R 2017 ensures clinical benefit in proton FLASH.

684. B. Neutron shielding design most significantly affects dose in carbon ion MRT.

685. D. TVL for 900 MeV/u carbon ions in concrete is ~60 cm (high density).

686. E. Real-time scintillators are suitable for proton FLASH due to ultra-high dose rates.

687. C. Neutron contamination is the primary stray radiation in carbon ion MRT.

688. B. IR(ME)R 2017 requires reporting overexposures in radiotherapy.

689. B. Dose rate = (Γ·A)/r² = (0.03·12/37)/(4²) ≈ 1 mGy/h (1 GBq = 27 mCi).

690. B. Neutron yield drives shielding requirements for proton FLASH facilities.

691. B. RPS oversees local safety compliance in carbon ion MRT.

692. A. Lead is most effective for shielding secondary X-rays.

693. A. The annual effective dose limit for a pregnant worker is 1 mSv (IRR 2017).

694. B. Shielding placement most significantly affects staff dose in Ac-225 therapy.

695. B. Lead-lined gloves minimize gamma ray exposure in Ac-225 therapy.

696. D. Neutrons are most challenging to shield in proton FLASH facilities.

697. B. Radiation safety audits ensure regulatory compliance in proton FLASH departments.

698. A. Source activity drives the dose rate from Ac-225 (alpha/gamma emitter).

699. A. The half-life of Ac-225 is ~10 days.

700. C. Shielding is critical for reducing public dose in carbon ion MRT facilities.

Radiation Physics (20 Questions)

701. What is the approximate relative biological effectiveness (RBE) of a 1 GeV/u carbon ion at the midpoint of a 14 cm SOBP in a hypoxic pancreatic tumour, considering LET and oxygenation effects?
     A. 2.5
     B. 3.5
     C. 4.5
     D. 5.5
     E. 6.5

702. For a 55 MV photon beam interacting with a tungsten collimator in a carbon ion MRT setup, what is the dominant interaction process contributing to secondary neutron production?
     A. Photoelectric effect
     B. Compton scattering
     C. Pair production
     D. Photodisintegration
     E. Coherent scattering

703. Calculate the tenth-value layer (TVL) for a 45 MV photon beam in lead, given a mass attenuation coefficient of 0.06 cm²/g and density of 11.34 g/cm³.
     A. 2.0 cm
     B. 3.0 cm
     C. 4.0 cm
     D. 5.0 cm
     E. 6.0 cm

704. In a carbon ion MRT setup with 450 keV X-rays, what is the primary mechanism enhancing peak-to-valley dose ratios in hypoxic tissue?
     A. Enhanced Compton scattering
     B. Spatial fractionation
     C. Reduced pair production
     D. Increased nuclear interactions
     E. Altered bremsstrahlung yield

705. What is the CSDA range of a 1.8 GeV proton in water, accounting for nuclear interactions and straggling?
     A. 100 cm
     B. 110 cm
     C. 120 cm
     D. 130 cm
     E. 140 cm

706. Which factor most significantly affects the neutron dose equivalent in a 60 MV linac with a graphite target for proton FLASH therapy?
     A. Target atomic number
     B. Photonuclear reaction cross-section
     C. Collimator thickness
     D. Beam current
     E. Gantry angle

707. What is the energy of a characteristic X-ray emitted from the M-shell to K-shell transition in platinum (Z=78)?
     A. 50 keV
     B. 70 keV
     C. 90 keV
     D. 110 keV
     E. 130 keV

708. For a 15 keV photon beam in bone, what is the dominant interaction, and how does its cross-section scale with energy (E)?
     A. Compton scattering, ∝ 1/E
     B. Photoelectric effect, ∝ 1/E³
     C. Pair production, ∝ E²
     D. Coherent scattering, ∝ 1/E²
     E. Photodisintegration, ∝ E

709. What is the primary interaction mechanism for 350 MeV neutrons in cortical bone, considering secondary particle production?
     A. Elastic scattering with protons
     B. Inelastic scattering with calcium
     C. Neutron capture by phosphorus
     D. Spallation reactions
     E. Compton scattering

710. What is the mass stopping power ratio of soft tissue to water for a 80 MeV electron beam, considering density effects (soft tissue: 1.04 g/cm³, water: 1.00 g/cm³)?
     A. 0.90
     B. 1.00
     C. 1.04
     D. 1.10
     E. 1.20

711. Which factor most significantly affects the production of secondary positrons in a 60 MV photon beam interacting with a molybdenum collimator?
     A. Target atomic number
     B. Pair production threshold
     C. Collimator thickness
     D. Beam divergence
     E. Gantry angle

712. What is the dose rate at 9 meters from a 30 GBq Ir-192 source, given a specific gamma-ray constant of 0.13 R·m²/Ci·h, ignoring shielding?
     A. 0.03 mGy/h
     B. 0.3 mGy/h
     C. 3 mGy/h
     D. 30 mGy/h
     E. 300 mGy/h

713. Which equation correctly describes the energy dependence of the pair production cross-section for ultra-high-energy photons (>200 MeV)?
     A. ∝ E
     B. ∝ E²
     C. ∝ ln(E)
     D. ∝ 1/E
     E. ∝ 1/E²

714. What is the approximate range of a 90 MeV electron in steel (density 7.85 g/cm³), accounting for bremsstrahlung losses?
     A. 1.0 cm
     B. 1.5 cm
     C. 2.0 cm
     D. 2.5 cm
     E. 3.0 cm

715. In a targeted alpha therapy using Bi-213, what is the primary mode of energy deposition in tumour cells?
     A. Bremsstrahlung radiation
     B. Alpha particle emission
     C. Gamma ray emission
     D. Compton scattering
     E. Photoelectric effect

716. What is the primary source of secondary protons in a 1 GeV/u carbon ion beam interacting with a hypoxic tumour?
     A. Elastic scattering
     B. Nuclear fragmentation
     C. Compton scattering
     D. Pair production
     E. Bremsstrahlung radiation

717. Which material property most significantly affects the angular scattering of a 1.2 GeV proton beam in a carbon fibre range shifter?
     A. Electron density
     B. Atomic number
     C. Mass density
     D. Thermal conductivity
     E. Magnetic susceptibility

718. What is the approximate energy threshold for phi meson production in a proton beam interacting with a titanium target?
     A. 1 GeV
     B. 1.5 GeV
     C. 2 GeV
     D. 2.5 GeV
     E. 3 GeV

719. Which shielding configuration is most effective for 600 MeV neutrons in a proton FLASH therapy facility?
     A. Lead followed by concrete
     B. Polyethylene followed by boron
     C. Steel followed by water
     D. Perspex followed by cadmium
     E. Concrete followed by paraffin

720. What is the primary mode of energy loss for a 300 GeV electron in tungsten, considering radiative effects?
     A. Collisional interactions
     B. Bremsstrahlung radiation
     C. Compton scattering
     D. Pair production
     E. Synchrotron radiation

Dosimetry (20 Questions)

721. What is the absorbed dose rate at 5 meters from a 18 GBq Lu-177 source, given a specific gamma-ray constant of 0.02 R·m²/Ci·h, ignoring shielding?
     A. 0.05 mGy/h
     B. 0.5 mGy/h
     C. 5 mGy/h
     D. 50 mGy/h
     E. 500 mGy/h

722. Which quantity is most critical for assessing the risk of radiation-induced thyroid cancer in carbon ion MRT?
     A. Absorbed dose
     B. Equivalent dose
     C. Effective dose
     D. Kerma
     E. Exposure

723. What is the radiation weighting factor (W_R) for 500 MeV neutrons in radiation protection, per ICRP 103?
     A. 2
     B. 5
     C. 10
     D. 20
     E. 50

724. What is the percentage depth dose (PDD) at 45 cm depth for a 45 MV photon beam (10x10 cm² field, SSD=100 cm) in water, given a PDD of 100% at dmax=6.0 cm and an attenuation coefficient of 0.018 cm⁻¹?
     A. 20%
     B. 25%
     C. 30%
     D. 35%
     E. 40%

725. Which dosimeter is most suitable for measuring dose in a 0.006 mm² microbeam radiotherapy field with 450 keV X-rays?
     A. Ionisation chamber
     B. TLD
     C. Nanodot OSL
     D. Perovskite detector
     E. Radiochromic film

726. What is the monitor unit (MU) required to deliver 9 Gy to a depth of 35 cm through a 5 cm lung slab (density=0.26 g/cm³, μ/ρ=0.03 cm²/g) and 2 cm bone slab (density=1.85 g/cm³, μ/ρ=0.05 cm²/g) for a 45 MV photon beam (10x10 cm² field, SAD=100 cm, output factor=1.07, TMR=0.52)?
     A. 900 MU
     B. 1000 MU
     C. 1100 MU
     D. 1200 MU
     E. 1300 MU

727. What is the approximate depth of the 90% isodose line for a 1 GeV/u carbon ion beam in water, assuming a 15 cm SOBP?
     A. 50 cm
     B. 55 cm
     C. 60 cm
     D. 65 cm
     E. 70 cm

728. Which factor most significantly affects the accuracy of dosimetry in a 0.025 cm² field for carbon ion arc therapy?
     A. Detector lateral response
     B. Beam energy spread
     C. Source-to-detector distance
     D. Collimator misalignment
     E. Nuclear interactions

729. What is the primary advantage of carbon nanotube detectors in carbon ion MRT dosimetry?
     A. High spatial resolution
     B. Ultra-fast response time
     C. Low cost
     D. Energy independence
     E. Large dynamic range

730. What is the tissue maximum ratio (TMR) at 50 cm depth for a 45 MV photon beam (10x10 cm² field, SAD=100 cm), given a PDD of 20% at 50 cm, PDD of 100% at dmax=6.0 cm, and BSF of 1.09?
     A. 0.15
     B. 0.18
     C. 0.21
     D. 0.24
     E. 0.27

731. What is the equivalent dose from a 6 mGy absorbed dose of 400 MeV protons to the skin?
     A. 0.06 mSv
     B. 0.6 mSv
     C. 6 mSv
     D. 12 mSv
     E. 60 mSv

732. What is the effective dose from a 8 mGy absorbed dose to the stomach (tissue weighting factor=0.12) from 500 MeV neutrons (W_R=10)?
     A. 0.096 mSv
     B. 0.96 mSv
     C. 9.6 mSv
     D. 96 mSv
     E. 960 mSv

733. Which dosimetry protocol is most suitable for calibrating a 1.2 GeV proton beam in a water phantom?
     A. TG-21
     B. TG-51
     C. IAEA TRS-398
     D. AAPM TG-61
     E. TRS-483

734. What is the primary source of uncertainty in alanine dosimetry for verifying a proton FLASH therapy plan?
     A. Energy dependence
     B. Dose-rate dependence
     C. Chemical stability
     D. Readout reproducibility
     E. Temperature sensitivity

735. What is the monitor unit (MU) correction factor for a 4 cm lung inhomogeneity (density=0.26 g/cm³, μ/ρ=0.03 cm²/g) and 3 cm bone inhomogeneity (density=1.85 g/cm³, μ/ρ=0.05 cm²/g) in a 45 MV photon beam at 40 cm depth?
     A. 0.85
     B. 0.90
     C. 0.95
     D. 1.00
     E. 1.05

736. Which dosimeter is most suitable for in-vivo dosimetry in a synchrotron-based carbon ion MRT setup?
     A. Ionisation chamber
     B. TLD
     C. MOSFET
     D. Diamond detector
     E. Plastic scintillator

737. What is the primary purpose of the phantom scatter factor (Sp) in proton FLASH dosimetry?
     A. To quantify collimator scatter
     B. To normalize dose for phantom size
     C. To measure dose at depth
     D. To assess beam flatness
     E. To determine penumbra width

738. What is the approximate penumbra width (20%–80%) for a 1.2 GeV proton beam at 100 cm depth in water, considering nuclear interactions?
     A. 8 mm
     B. 10 mm
     C. 12 mm
     D. 14 mm
     E. 16 mm

739. Which factor most significantly affects the dose rate from a carbon ion MRT source with 600 keV X-rays?
     A. Beamlet size
     B. Source intensity
     C. Source energy
     D. Source material
     E. Source shape

740. What is the primary advantage of Fricke dosimetry in carbon ion MRT?
     A. High spatial resolution
     B. Chemical stability
     C. Absolute dose measurement
     D. Real-time readout
     E. Low cost

Radiotherapy Treatment Planning (20 Questions)

741. What is the primary advantage of carbon ion MRT over proton FLASH therapy for radioresistant sarcomas?
     A. Reduced treatment time
     B. Enhanced RBE in hypoxic regions
     C. Lower cost
     D. Increased scatter dose
     E. Simplified planning

742. Which parameter is most critical for defining the planning organ-at-risk volume (PRV) in carbon ion MRT for a brain tumour?
     A. Tumour size
     B. Organ motion and setup error
     C. Beam energy
     D. Field size
     E. Monitor units

743. What is the primary advantage of cyclotron-based proton FLASH therapy for deep-seated tumours?
     A. Uniform dose distribution
     B. Ultra-high dose rate delivery
     C. Increased treatment time
     D. Lower cost
     E. Simplified planning

744. Which dose calculation algorithm is most accurate for carbon ion MRT in a lung tumour with a 0.26 g/cm³ density heterogeneity?
     A. Pencil beam
     B. Convolution-superposition
     C. Monte Carlo
     D. Acuros XB
     E. Collapsed cone

745. What is the primary purpose of a dynamic collimator in proton FLASH therapy?
     A. To increase beam energy
     B. To sharpen lateral dose fall-off
     C. To reduce skin sparing
     D. To monitor dose delivery
     E. To reduce scatter radiation

746. Which factor most significantly affects the lateral dose spread in carbon ion MRT for a pancreatic tumour?
     A. Beam energy
     B. Multiple Coulomb scattering
     C. Gantry rotation speed
     D. Collimator shape
     E. Monitor units

747. What is the primary advantage of AI-based dose prediction in carbon ion MRT planning?
     A. Reduced treatment time
     B. Improved plan robustness
     C. Lower cost
     D. Increased scatter dose
     E. Simplified planning

748. Which parameter is most critical for tumour control probability (TCP) in proton FLASH therapy?
     A. Tumour volume
     B. Dose rate
     C. Beam energy
     D. Field size
     E. Monitor units

749. What is the primary purpose of a patient-specific bolus in carbon ion MRT for a superficial tumour?
     A. To increase beam energy
     B. To conform dose to target depth
     C. To shape the radiation field
     D. To monitor dose delivery
     E. To reduce scatter radiation

750. Which factor most significantly affects the dose conformity in carbon ion MRT for a liver tumour?
     A. Beamlet spacing
     B. Beam energy
     C. Field size
     D. Gantry angle
     E. Monitor units

751. What is the primary advantage of deep learning-based contouring in carbon ion MRT planning?
     A. Reduced treatment time
     B. Improved contour accuracy
     C. Lower cost
     D. Increased scatter dose
     E. Simplified planning

752. Which structure is most critical for dose constraints in proton FLASH therapy for a pancreatic tumour?
     A. Spinal cord
     B. Duodenum
     C. Kidneys
     D. Heart
     E. Lungs

753. What is the primary purpose of a beam-specific aperture in carbon ion MRT?
     A. To increase beam energy
     B. To sharpen lateral dose fall-off
     C. To reduce skin sparing
     D. To monitor dose delivery
     E. To reduce scatter radiation

754. Which factor most significantly affects the dose heterogeneity in carbon ion MRT for bulky sarcomas?
     A. Nuclear fragmentation
     B. Beam energy
     C. Field size
     D. Gantry angle
     E. Monitor units

755. What is the primary advantage of knowledge-based planning in proton FLASH therapy?
     A. Reduced treatment time
     B. Automated plan optimization
     C. Lower cost
     D. Increased scatter dose
     E. Simplified planning

756. Which parameter is most critical for normal tissue complication probability (NTCP) in carbon ion MRT?
     A. Tumour volume
     B. Peak-to-valley dose ratio
     C. Beam energy
     D. Field size
     E. Monitor units

757. What is the primary purpose of a ridge filter in proton FLASH therapy?
     A. To increase beam energy
     B. To create a spread-out Bragg peak
     C. To shape the radiation field
     D. To monitor dose delivery
     E. To reduce scatter radiation

758. Which factor most significantly affects the dose distribution in carbon ion MRT for ocular melanoma?
     A. Beamlet spacing
     B. Beam energy
     C. Field size
     D. Gantry angle
     E. Monitor units

759. What is the primary advantage of PET-guided dose painting in carbon ion MRT?
     A. Reduced treatment time
     B. Targeting metabolically active regions
     C. Lower cost
     D. Increased scatter dose
     E. Simplified planning

760. Which parameter is most critical for dose escalation in proton FLASH therapy?
     A. Beam energy
     B. Dose rate
     C. Field size
     D. Monitor units
     E. Collimator angle

Imaging (20 Questions)

761. What is the primary advantage of 20T MRI in carbon ion MRT planning for brain tumours?
     A. Ultra-high spatial resolution
     B. Low radiation dose
     C. Real-time imaging
     D. Electron density information
     E. Low cost

762. Which imaging modality is most suitable for assessing tumour perfusion in pancreatic proton FLASH therapy?
     A. CT
     B. MRI
     C. PET
     D. 4D-CT
     E. Ultrasound

763. What is the primary source of contrast in perfusion-weighted MRI for carbon ion MRT?
     A. Proton density
     B. Blood flow dynamics
     C. Electron density
     D. Atomic number
     E. Tissue relaxation time

764. Which factor most significantly affects the spatial resolution in photon-counting CT for proton FLASH planning?
     A. Detector pixel size
     B. Tube voltage
     C. Reconstruction algorithm
     D. Field of view
     E. Gantry rotation speed

765. What is the primary advantage of Bi-213 PET in targeted alpha therapy planning?
     A. High spatial resolution
     B. Low radiation dose
     C. Alpha emitter tracking
     D. Real-time imaging
     E. Low cost

766. Which radionuclide is most suitable for imaging bone metastases in proton FLASH therapy planning?
     A. F-18 (NaF)
     B. Tc-99m
     C. Ga-68
     D. I-131
     E. Zr-89

767. What is the primary purpose of the modulation transfer function (MTF) in MR-guided carbon ion MRT?
     A. To measure radiation dose
     B. To quantify spatial resolution
     C. To assess image contrast
     D. To determine image noise
     E. To monitor patient motion

768. Which factor most significantly affects the signal-to-noise ratio in 20T MRI for proton FLASH planning?
     A. Field strength
     B. Gradient strength
     C. RF coil sensitivity
     D. Reconstruction algorithm
     E. Field of view

769. What is the primary advantage of dual-energy CT in carbon ion MRT planning?
     A. High soft tissue contrast
     B. Improved stopping power estimation
     C. Low radiation dose
     D. Real-time imaging
     E. Low cost

770. Which imaging modality is most suitable for delineating liver tumours in carbon ion MRT planning?
     A. CT
     B. MRI
     C. PET
     D. 4D-CT
     E. Ultrasound

771. What is the primary source of artefacts in PET-MRI hybrid imaging for proton FLASH therapy?
     A. Photon scattering
     B. Attenuation correction errors
     C. Metal implants
     D. Reconstruction algorithm
     E. Patient motion

772. Which factor most significantly affects the temporal resolution in dynamic PET imaging for carbon ion MRT?
     A. Detector timing resolution
     B. Radiotracer activity
     C. Reconstruction algorithm
     D. Field of view
     E. Patient size

773. What is the primary advantage of MR spectroscopy in proton FLASH therapy planning?
     A. High spatial resolution
     B. Low radiation dose
     C. Metabolic tumour profiling
     D. Real-time imaging
     E. Low cost

774. Which imaging modality is most suitable for assessing lung tumour motion in carbon ion MRT planning?
     A. CT
     B. MRI
     C. PET
     D. 4D-CT
     E. Ultrasound

775. What is the primary purpose of deformable image registration in proton FLASH therapy planning?
     A. To measure radiation dose
     B. To align imaging datasets with motion
     C. To assess image contrast
     D. To determine spatial resolution
     E. To monitor image noise

776. Which factor most significantly affects the radiation dose in 4D-MRI for proton FLASH planning?
     A. Field strength
     B. Gradient slew rate
     C. Acquisition time
     D. Reconstruction algorithm
     E. Field of view

777. What is the primary advantage of arterial spin labelling (ASL) MRI in carbon ion MRT planning?
     A. High spatial resolution
     B. Non-invasive perfusion imaging
     C. Low radiation dose
     D. Real-time imaging
     E. Low cost

778. Which imaging modality is most suitable for real-time dosimetry in proton FLASH therapy?
     A. CT
     B. MRI
     C. PET
     D. Cherenkov imaging
     E. Ultrasound

779. What is the primary source of contrast in dynamic contrast-enhanced (DCE) MRI for carbon ion MRT?
     A. Proton density
     B. Contrast agent kinetics
     C. Electron density
     D. Radiotracer uptake
     E. Tissue relaxation time

780. Which factor most significantly affects the image noise in MR elastography for proton FLASH planning?
     A. Voxel size
     B. Gradient strength
     C. Reconstruction algorithm
     D. Field of view
     E. Patient size

Radiation Protection (20 Questions)

781. What is the annual equivalent dose limit for the skin of radiation workers in the UK, per IRR 2017?
     A. 1 mSv
     B. 20 mSv
     C. 50 mSv
     D. 150 mSv
     E. 500 mSv

782. Which material is most effective for shielding 700 MeV neutrons in a carbon ion MRT facility?
     A. Lead
     B. Concrete with hydrogen
     C. Perspex
     D. Steel
     E. Water

783. What is the primary purpose of the optimization principle in IR(ME)R 2017 for carbon ion MRT?
     A. To maximize radiation dose
     B. To minimize patient exposure
     C. To measure radiation dose
     D. To calibrate dosimeters
     E. To monitor radiation levels

784. Which factor most significantly affects the occupational dose in a proton FLASH therapy setup?
     A. Beam energy
     B. Neutron shielding design
     C. Field size
     D. Gantry rotation speed
     E. Monitor units

785. What is the approximate half-value layer (HVL) for a 1 GeV/u carbon ion beam in steel?
     A. 10 cm
     B. 15 cm
     C. 20 cm
     D. 25 cm
     E. 30 cm

786. Which type of personal dosimeter is most suitable for monitoring dose in a carbon ion MRT setup?
     A. Film badge
     B. TLD
     C. MOSFET
     D. OSL dosimeter
     E. Real-time scintillator

787. What is the primary source of stray radiation in a proton FLASH therapy treatment room?
     A. Primary beam
     B. Patient scatter
     C. Neutron contamination
     D. Bremsstrahlung radiation
     E. Compton scattering

788. Which regulation requires optimization of medical radiation exposures in the UK?
     A. IRR 2017
     B. IR(ME)R 2017
     C. RIDDOR 2013
     D. COSHH 2002
     E. MHRA 2008

789. What is the dose rate at 3 meters from a 10 GBq Bi-213 source, given a specific gamma-ray constant of 0.05 R·m²/Ci·h, ignoring shielding?
     A. 0.15 mGy/h
     B. 1.5 mGy/h
     C. 15 mGy/h
     D. 150 mGy/h
     E. 1500 mGy/h

790. Which factor most significantly affects the shielding requirements for a carbon ion MRT facility?
     A. Beam energy
     B. Neutron yield
     C. Field size
     D. Gantry angle
     E. Monitor units

791. What is the primary purpose of a radiation protection advisor (RPA) in a proton FLASH therapy department?
     A. To deliver radiotherapy
     B. To provide expert safety advice
     C. To calibrate dosimeters
     D. To monitor patient doses
     E. To perform quality assurance

792. Which material is most effective for shielding secondary gamma rays in a carbon ion MRT bunker?
     A. Lead
     B. Concrete
     C. Polyethylene
     D. Boron
     E. Perspex

793. What is the annual effective dose limit for the public in the UK, per IRR 2017?
     A. 1 mSv
     B. 5 mSv
     C. 10 mSv
     D. 20 mSv
     E. 50 mSv

794. Which factor most significantly affects the dose to staff during Bi-213 targeted alpha therapy procedures?
     A. Source activity
     B. Shielding placement
     C. Field size
     D. Gantry angle
     E. Monitor units

795. What is the primary advantage of a remote afterloading system in Bi-213 radionuclide therapy?
     A. Reduced treatment time
     B. Minimized staff exposure
     C. Increased patient comfort
     D. Simplified quality assurance
     E. Enhanced dose delivery

796. Which type of radiation is most hazardous for external exposure in a carbon ion MRT facility?
     A. Alpha particles
     B. Beta particles
     C. Gamma rays
     D. Neutrons
     E. X-rays

797. What is the primary purpose of a radiation protection committee in a proton FLASH therapy department?
     A. To deliver radiotherapy
     B. To oversee safety policies
     C. To calibrate dosimeters
     D. To monitor patient doses
     E. To perform quality assurance

798. Which factor most significantly affects the dose rate from a Bi-213 unsealed source in targeted alpha therapy?
     A. Source activity
     B. Alpha particle energy
     C. Source size
     D. Source material
     E. Source shape

799. What is the approximate half-life of Bi-213 used in targeted alpha therapy?
     A. 46 minutes
     B. 7 days
     C. 2 days
     D. 12 hours
     E. 1 hour

800. Which principle is most critical for reducing patient dose in carbon ion MRT imaging?
     A. Time
     B. Distance
     C. Shielding
     D. Optimization
     E. Calibration

Answers

Radiation Physics

701. C. RBE at the midpoint of a 14 cm SOBP for 1 GeV/u carbon ions in hypoxic pancreatic tumour is ~4.5 due to LET (~200 keV/μm).

702. D. Photodisintegration in tungsten produces neutrons for 55 MV photons (E > 7 MeV).

703. B. TVL = ln(10)/(μ·ρ) = 2.303/(0.06·11.34) ≈ 3.0 cm.

704. B. Spatial fractionation enhances peak-to-valley dose ratios in carbon ion MRT under hypoxia.

705. C. CSDA range for 1.8 GeV protons in water is ~120 cm (R ∝ E¹·⁵).

706. B. Photonuclear reaction cross-section drives neutron dose in graphite targets.

707. B. M-to-K transition in platinum emits ~70 keV photons (K-shell binding energy).

708. B. Photoelectric effect dominates at 15 keV in bone, scaling as ∝ 1/E³.

709. D. Spallation reactions dominate for 350 MeV neutrons in bone, producing cascades.

710. C. Mass stopping power ratio of soft tissue to water is ~1.04 due to density (S ∝ ρ).

711. B. Pair production threshold (>1.022 MeV) drives positron production in 60 MV beams.

712. B. Dose rate = (Γ·A)/r² = (0.13·30/37)/(9²) ≈ 0.3 mGy/h (1 GBq = 27 mCi).

713. C. Pair production cross-section scales as ∝ ln(E) for ultra-high energies.

714. B. Range in steel = 90/7.85 ≈ 1.5 cm (R ≈ 0.5 E, adjusted for bremsstrahlung).

715. B. Alpha particle emission is the primary energy deposition mode for Bi-213.

716. B. Nuclear fragmentation produces secondary protons in carbon ion beams.

717. B. Atomic number drives angular scattering in carbon fibre range shifters.

718. B. Phi meson production in titanium requires ~1.5 GeV.

719. B. Polyethylene slows 600 MeV neutrons, and boron captures thermal neutrons.

720. B. Bremsstrahlung radiation dominates for 300 GeV electrons in tungsten (E > critical energy).

Dosimetry

721. B. Dose rate = (Γ·A)/r² = (0.02·18/37)/(5²) ≈ 0.5 mGy/h (1 GBq = 27 mCi).

722. C. Effective dose assesses thyroid cancer risk (thyroid W_T=0.04).

723. C. W_R for 500 MeV neutrons is 10 per ICRP 103.

724. C. PDD = 100 · e^(-μ·(d-dmax)) = 100 · e^(-0.018·(45-6.0)) ≈ 30%.

725. D. Perovskite detectors offer sub-μm resolution for 0.006 mm² microbeam fields.

726. D. MU = Dose/(TMR·Output·CF), CF_lung = e^(0.03·5·(0.26-1)) ≈ 0.90, CF_bone = e^(0.05·2·(1.85-1)) ≈ 1.09, Total CF = 0.90·1.09 ≈ 0.98, MU = 9/(0.52·1.07·0.98) ≈ 1200 MU.

727. B. 1 GeV/u carbon ion range ~65 cm, 90% isodose at SOBP center ~55 cm.

728. A. Detector lateral response affects dosimetry accuracy in 0.025 cm² fields.

729. B. Carbon nanotube detectors offer ultra-fast response for carbon ion MRT.

730. B. TMR = PDD(d)/PDD(dmax) · BSF = 20/(100·1.09) ≈ 0.18.

731. D. Equivalent dose = 6 mGy · 2 (W_R for 400 MeV protons) = 12 mSv.

732. C. Effective dose = 8 mGy · 0.12 (W_T for stomach) · 10 (W_R for neutrons) = 9.6 mSv.

733. C. IAEA TRS-398 is suitable for 1.2 GeV proton calibration.

734. B. Dose-rate dependence is the primary uncertainty in alanine dosimetry for FLASH.

735. B. CF_lung = e^(0.03·4·(0.26-1)) ≈ 0.91, CF_bone = e^(0.05·3·(1.85-1)) ≈ 1.14, Total CF = 0.91·1.14 ≈ 0.90.

736. D. Diamond detectors are synchrotron-compatible for carbon ion MRT.

737. B. Phantom scatter factor normalizes dose for phantom size in proton FLASH.

738. C. Penumbra width for 1.2 GeV protons at 100 cm is ~12 mm (scattering, nuclear interactions).

739. B. Source intensity drives dose rate in carbon ion MRT with 600 keV X-rays.

740. C. Fricke dosimetry offers absolute dose measurement for carbon ion MRT.

Radiotherapy Treatment Planning

741. B. Carbon ion MRT enhances RBE in hypoxic regions for radioresistant sarcomas.

742. B. Organ motion and setup error are critical for brain PRV in carbon ion MRT.

743. B. Cyclotron-based proton FLASH delivers ultra-high dose rates for deep tumours.

744. C. Monte Carlo is most accurate for carbon ion MRT in low-density lung.

745. B. Dynamic collimators sharpen lateral dose fall-off in proton FLASH.

746. B. Multiple Coulomb scattering affects lateral dose spread in pancreatic carbon ion MRT.

747. B. AI-based dose prediction improves plan robustness in carbon ion MRT.

748. B. Dose rate drives TCP in proton FLASH therapy.

749. B. Patient-specific boluses conform dose to superficial targets in carbon ion MRT.

750. A. Beamlet spacing affects dose conformity in liver carbon ion MRT.

751. B. Deep learning-based contouring improves accuracy in carbon ion MRT.

752. B. Duodenum is critical for dose constraints in pancreatic proton FLASH.

753. B. Beam-specific apertures sharpen lateral dose fall-off in carbon ion MRT.

754. A. Nuclear fragmentation causes dose heterogeneity in carbon ion MRT for sarcomas.

755. B. Knowledge-based planning automates optimization in proton FLASH.

756. B. Peak-to-valley dose ratio drives NTCP in carbon ion MRT.

757. B. Ridge filters create a spread-out Bragg peak in proton FLASH.

758. A. Beamlet spacing determines dose distribution in ocular carbon ion MRT.

759. B. PET-guided dose painting targets metabolically active regions in carbon ion MRT.

760. B. Dose rate is critical for dose escalation in proton FLASH.

Imaging

761. A. 20T MRI provides ultra-high spatial resolution for brain tumour delineation.

762. B. MRI is suitable for assessing perfusion in pancreatic proton FLASH.

763. B. Perfusion-weighted MRI contrast arises from blood flow dynamics.

764. A. Detector pixel size affects spatial resolution in photon-counting CT.

765. C. Bi-213 PET tracks alpha emitters for targeted therapy planning.

766. A. F-18 (NaF) is suitable for imaging bone metastases.

767. B. MTF quantifies spatial resolution in MR-guided carbon ion MRT.

768. C. RF coil sensitivity affects SNR in 20T MRI.

769. B. Dual-energy CT improves stopping power estimation for carbon ion MRT.

770. B. MRI is ideal for delineating liver tumours in carbon ion MRT.

771. B. Attenuation correction errors cause artefacts in PET-MRI hybrid imaging.

772. A. Detector timing resolution affects temporal resolution in dynamic PET.

773. C. MR spectroscopy profiles tumour metabolism in proton FLASH.

774. D. 4D-CT is suitable for assessing lung tumour motion in carbon ion MRT.

775. B. Deformable image registration aligns datasets with motion in proton FLASH.

776. C. Acquisition time affects radiation dose in 4D-MRI (non-ionizing, but time impacts dose equivalence).

777. B. ASL MRI offers non-invasive perfusion imaging for carbon ion MRT.

778. D. Cherenkov imaging is suitable for real-time dosimetry in proton FLASH.

779. B. DCE-MRI contrast arises from contrast agent kinetics.

780. A. Voxel size affects image noise in MR elastography.

Radiation Protection

781. E. The annual equivalent dose limit for the skin is 500 mSv (IRR 2017).

782. B. Concrete with hydrogen shields 700 MeV neutrons effectively.

783. B. Optimization in IR(ME)R 2017 minimizes patient exposure in carbon ion MRT.

784. B. Neutron shielding design most significantly affects occupational dose in proton FLASH.

785. C. HVL for 1 GeV/u carbon ions in steel is ~20 cm (high Z and density).

786. E. Real-time scintillators are suitable for carbon ion MRT due to high dose rates.

787. C. Neutron contamination is the primary stray radiation in proton FLASH.

788. B. IR(ME)R 2017 requires optimization of medical radiation exposures.

789. B. Dose rate = (Γ·A)/r² = (0.05·10/37)/(3²) ≈ 1.5 mGy/h (1 GBq = 27 mCi).

790. B. Neutron yield drives shielding requirements for carbon ion MRT facilities.

791. B. RPA provides expert safety advice in proton FLASH departments.

792. A. Lead is most effective for shielding secondary gamma rays.

793. A. The annual effective dose limit for the public is 1 mSv (IRR 2017).

794. B. Shielding placement most significantly affects staff dose in Bi-213 therapy.

795. B. Remote afterloading minimizes staff exposure in Bi-213 therapy.

796. D. Neutrons are most hazardous for external exposure in carbon ion MRT.

797. B. Radiation protection committee oversees safety policies in proton FLASH.

798. A. Source activity drives the dose rate from Bi-213 (alpha/gamma emitter).

799. A. The half-life of Bi-213 is ~46 minutes.

800. D. Optimization is critical for reducing patient dose in carbon ion MRT imaging.