2020 Joint AAPM | COMP Virtual Meeting
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Session Title: Development of a Clinical Program for MR-Linac Technology: Tips from Installation to Clinical Implementation
Question 1: For a patient treated on an MR-Linac or for repeated MRI simulation scans, the patient only needs to be screened for MRI safety once. Then they should be OK through all of the RT treatment fractions.
Reference:van der Heide UA, Frantzen-Steneker M, Astreinidou E, Nowee ME, van Houdt PJ, MRI basics for radiation oncologists, Clin Transl Radiat Oncol. 2019 Apr 13;18:74-79
Choice A:Yes
Choice B:No
Question 2: Who should be trained about MRI safety in a radiation therapy department?
Reference:van der Heide UA, Frantzen-Steneker M, Astreinidou E, Nowee ME, van Houdt PJ, MRI basics for radiation oncologists, Clin Transl Radiat Oncol. 2019 Apr 13;18:74-79
Choice A:Radiation physicists
Choice B:Radiation oncologists, residents, physician assistants
Choice C:Dosimetrist
Choice D:RTTs
Choice E:All of above
Choice F:only physicists who work around MRI should be trained
Question 3: The following factors need to be considered when performing reference dosimetry in an MR-Linac:
Reference:1/ Malkov V and Rogers DWO. Monte Carlo study of ionization chamber magnetic field correction factors as a function of angle and beam quality. Med Phys 45(2), 908-925, 2018 2/ Iakovenko V et al. Experimental measurement of ionization chamber angular response and associated magnetic field correction factors in MR-Linac. Med Phys 47(4), 1940 – 1948, 2020
Choice A:A correction factor in the TG-51 formalism that accounts for the chamber being irradiated in the presence of a magnetic field.
Choice B:The orientation of the chamber with respect to the magnetic field.
Choice C:The electron return effect where the beam exits the water phantom.
Choice D:A and B only
Choice E:A, B and C
Question 4: Which of the following statements is false with regard to an MR-Linac ?
Reference:1/ Woodings SJ, Bluemink JJ, de Vries JHW, et al. Beam characterisation of the 1.5T MRI-linac. Phys Med Biol. 63(8), 085015, 2018. 2/ Perik et al. The impact of a 1.5 T MRI linac fringe field on neighbouring linear accelerators. Physics and Imaging in Radiation Oncology 4, 12-16, 2017. 3/ O’Brien et al. Monte Carlo study of the chamber-phantom air gap effect in a magnetic field. Med Phys 44(7), 3830-3838, 2017. 4/ Perik et al. Master’s thesis, University of Heidelberg, Germany, 2017.
Choice A:The profiles are skewed in the direction parallel to the magnetic field.
Choice B:Small air gaps, of the order of a fraction of a millimeter, can have noticeable effects when irradiating a farmer chamber in a plastic phantom.
Choice C:Microdiamond detectors can be used when scanning profiles and PDD’s in an MR-Linac.
Choice D:Gafchromic film is prone to air gaps effecting its response.
Choice E:It is advisable to verify that there are no beam steering effects for linacs in close proximity to an MR-Linac.
Question 5: Pancreatic cancer is one of the most common sites for which MRI-guided ART is indicated. All of the following are reasons for this, EXCEPT:
Reference:Boldrini, L., Cusumano, D., Cellini, F., Azario, L., Mattiucci, GC., and Valentini, V, “Online Adaptive Magnetic Resonance Guided Radiotherapy for Pancreatic Cancer: State of the Art, Pearls and Pitfalls, Radiat Oncol, 14 (1), 2019 Apr 29.
Choice A:Target dose is limited by the toxicity of highly radio-sensitive abdominal organs at risk.
Choice B:Treatment delivery is complicated by the significant inter-fractional anatomic changes due to variable organ filling.
Choice C:High soft tissue contrast of MRI aids in accurate daily volumetric contouring.
Choice D:There can be significant pancreatic tumor regression over the course of SBRT delivery.
Question 6: What are 4 essential elements of an online ART workflow prior to treatment delivery?
Reference:Lim-Reinders, S,. Keller, B., Al-Ward, S., Sahgal, A and Kim A., “Online Adaptive Radiation Therapy” IJROBP, 99(4), 2017 Nov 17.
Choice A:Pre-treatment CT for each fraction to acquire density map, DIR, accelerated re-planning and patient specific QA checks.
Choice B:Daily in-room imaging, DIR, accelerated re-planning and patient specific QA checks.
Choice C:Daily in-room imaging, Monte Carlo optimization, DIR and pre-treatment QA measurements.
Choice D:Rigid registration/couch shifts, Monte Carlo optimization, auto-segmentation followed by dosimetrist review and pre-treatment DQA measurements.
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