| Question 1: What property has the least impact MRI-guided radiation therapy dosimetry? |
| Reference: | D. W. Litzenberg, B. A. Fraass, D. L. McShan, T. W. O. O’Donnell, D. A. Roberts, F. D. Becchetti, A. F. Bielajew, and J. M. Moran, “An apparatus for applying strong longitudinal magnetic fields to clinical photon and electron beams,” Phys. Med. Biol. 46, 401 2001.
Y. Chen, A. F. Bielajew, D. W. Litzenberg, J. M. Moran, and F. D. Becchetti, “Magnetic confinement of electron and photon radiotherapy dose: A Monte Carlo simulation with a nonuniform longitudinal magnetic field,” Med. Phys. 32, 3810–3818, 2005.
B. G. Fallone, “Real-time MR-guided radiotherapy: Integration of a low-field MR system,” Med. Phys. 36, 2774, 2009.
Paul J. Keall, Michael Barton, Stuart Crozier, The Australian Magnetic Resonance Imaging–Linac Program, Seminars in Radiation Oncology, Volume 24, Issue 3, 2014, Pages 203-206, ISSN 1053-4296, https://doi.org/10.1016/j.semradonc.2014.02.015 |
| Choice A: | B0 field orthogonal direction relative to direction of x-ray fluence |
| Choice B: | B0 field parallel direction relative to direction of x-ray fluence |
| Choice C: | Increased B0 field strength |
| Choice D: | Compton electrons |
| Choice E: | Kinetic energy of Compton-generated electrons |
| Question 2: Which technical approach to enabling the imaging magnet and MV radiation system to coexist are not available: |
| Reference: | B. G. Fallone, “Real-time MR-guided radiotherapy: Integration of a low-field MR system,” Med. Phys. 36, 2774, 2009.
Paul J. Keall, Michael Barton, Stuart Crozier, The Australian Magnetic Resonance Imaging–Linac Program, Seminars in Radiation Oncology, Volume 24, Issue 3, 2014, Pages 203-206, ISSN 1053-4296, https://doi.org/10.1016/j.semradonc.2014.02.015.
Reference(s): Jan J.W. Lagendijk, Bas W. Raaymakers, Marco van Vulpen,
The Magnetic Resonance Imaging–Linac System, Seminars in Radiation Oncology,
Volume 24, Issue 3, 2014, Pages 207-209, ISSN 1053-4296, https://doi.org/10.1016/j.semradonc.2014.02.009.
Mutic S and Dempsey J 2014 The viewray system: magnetic resonance—guided and controlled radiotherapy Semin. Radiat. Oncol. 24 196–9 |
| Choice A: | Active RF noise cancellation |
| Choice B: | Faraday cages /shields |
| Choice C: | High magnetic permeability metal alloys |
| Choice D: | Active magnetic shielding |
| Choice E: | Low x-ray attenuation RF coils |
| Question 3: With increased magnetic field strength for commercial MRI-guided radiation therapy systems: |
| Reference: | Nejad‐Davarani, S.P., Kim, J.P., Du, D. and Glide‐Hurst, C. (2019), Large field of view distortion assessment in a low‐field MR‐linac. Med. Phys., 46: 2347-2355. https://doi.org/10.1002/mp.13467
S Dorsch et al 2019 Phys. Med. Biol. 64 205011
Tijssen R, Philippens M, Paulson E, Glitzner M, Chugh B, Wetscherek A, Dubec M, Wang J and van der Heide U 2019 MRI commissioning of 1.5 T MR-linac systems—a multi-institutional study Radiother. Oncol. 132 114–20 |
| Choice A: | The frequency of cine imaging during treatment delivery significantly increases |
| Choice B: | The RF interference by the linear accelerator components significantly increases |
| Choice C: | The gantry angle dependence on B0 field inhomogeneity is nearly equivalent |
| Choice D: | The gradient nonlinearity induced spatial distortion is nearly equivalent |
| Choice E: | The baseline temperature of the cryostat significantly decreases |
| Question 4: In MRI-guided radiation therapy the Lorentz Force can be primarily responsible for each of the following, except: |
| Reference: | Karzmark, C.J. (1984), Advances in linear accelerator design for radiotherapy. Med. Phys., 11: 105-128. https://doi.org/10.1118/1.595617
A. F. Bielajew, “The effect of strong longitudinal magnetic fields on dose deposition from electron and photon beams,” Med. Phys. 20, 1171–1179, 1993.
Jan J.W. Lagendijk, Bas W. Raaymakers, Marco van Vulpen,
The Magnetic Resonance Imaging–Linac System, Seminars in Radiation Oncology,
Volume 24, Issue 3, 2014, Pages 207-209, ISSN 1053-4296, https://doi.org/10.1016/j.semradonc.2014.02.009.
Raaymakers BW, Lagendijk JJ, Overweg J, Kok JG, Raaijmakers AJ, Kerkhof EM, van der Put RW, Meijsing I, Crijns SP, Benedosso F, van Vulpen M, de Graaff CH, Allen J, Brown KJ. Integrating a 1.5 T MRI scanner with a 6 MV accelerator: proof of concept. Phys Med Biol. 2009 Jun 21;54(12):N229-37. doi: 10.1088/0031-9155/54/12/N01. Epub 2009 May 19. PMID: 19451689 |
| Choice A: | Asymmetry in radiation dose profiles |
| Choice B: | Eddy currents producing imaging artifacts |
| Choice C: | X-ray production |
| Choice D: | Elevated radiation dose at changing tissue density interfaces |
| Choice E: | Required x-ray shielding thickness |
| Question 5: By approximately how much does the presence of the magnetic field affect the response of the TLD? |
| Reference: | Steinmann et al. Investigation of TLD and EBT3 performance under the presence of 1.5, 0.35 and 0T magnetic field strengths in the MR/CT visible materials. Med Phys. 2019 July: 46 (7):3217-3226. |
| Choice A: | 0% |
| Choice B: | 5% |
| Choice C: | 10% |
| Choice D: | 50% |
| Question 6: What is the criteria for dose agreement (measured/predicted) within the target of IROC Houston’s H&N phantom irradiated with an MRIgRT system? |
| Reference: | Steinmann et al. MRIgRT head and Neck anthropomorphic QA phantom: Design, development, reproducibility and feasibility study. Med Phys. 2020 February 47 (2):604-613. |
| Choice A: | 0.97 - 1.03 |
| Choice B: | 0.95 - 1.05 |
| Choice C: | 0.93 - 1.07 |
| Choice D: | 0.95 - 1.07 |
