2017 AAPM Annual Meeting
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Session Title: SRS/SBRT: Clinical Implementation and Small Volume Dose Limits in Brain/Spine
Question 1: 1. A metastatic tumor at T8 on MRI is seen involving the right posterior vertebral body and right pedicle. What should be included as part of the CTV?
Reference:Cox et al. International Spine Radiosurgery Consortium consensus guidelines for target volume definition in spinal stereotactic radiosurgery. Int J Radiat Oncol Biol Phys. 2012 Aug 1;83(5):e597-605.
Choice A:The vertebral body only.
Choice B:The vertebral body and the right pedicle.
Choice C:The vertebral body and bilateral pedicles.
Choice D:The vertebral body and the right pedicle, transverse process, and lamina.
Choice E:The vertebral body and bilateral pedicles, transverse processes, and laminae.
Question 2: The predicted point max absolute dose to the thecal sac for 2-fraction SBRT that results in a 5% probability of radiation myelopathy is:
Reference:Sahgal et al. Probabilities of radiation myelopathy specific to stereotactic body radiation therapy to guide safe practice. Int J Radiat Oncol Biol Phys. 2013 Feb 1;85(2):341-7.
Choice A:12.4 Gy
Choice B:14.6 Gy
Choice C:17.0 Gy
Choice D:23.0 Gy
Choice E:25.3 Gy
Question 3: The most common pattern of failure after spine SBRT is:
Reference:Thibault et al. Salvage Stereotactic Body Radiotherapy (SBRT) Following In-Field Failure of Initial SBRT for Spinal Metastases. Int J Radiat Oncol Biol Phys. 2015 Oct 1;93(2):353-60. Al-Omair et al. Surgical resection of epidural disease improves local control following postoperative spine stereotactic body radiotherapy. Neuro Oncol. 2013 Oct;15(10):1413-9.
Choice A:Progression within the vertebral body.
Choice B:Progression within the epidural space.
Choice C:Progression within the posterior elements of the vertebral segment when not included in the CTV.
Choice D:Progression in the para-spinal extra-osseous soft tissues.
Question 4: Dose to modiolus is closely related to which of the cochlear dose?
Reference:Pract Radiat Oncol. January 2017 doi: 10.1016/j.prro.2016.08.005. Inherent functional dependence among cochlear dose surrogates for stereotactic radiosurgery of vestibular schwannomas.
Choice A:Mean Dose.
Choice B:Maximum Dose.
Choice C:Median Dose.
Choice D:Minimum Dose.
Choice E:Modal Dose.
Question 5: According to TG101 recommendations, the maximum dose calculation grid size for a spine SBRT treatment should be...
Reference:Stereotactic body radiation therapy: The report of TG101, Med Phys 2010: pg 4078, DOI: 10.1118/1.3438081
Choice A:2mm.
Choice B:3 mm.
Choice C:4 mm.
Choice D:5 mm.
Question 6: In the measurement of very small fields (< 1x1 cm), typical variation in output factors caused by wrong detector and/or incorrect setup is...
Reference:Das et al, Task Group 106, Med Phys 35, 4186 (2008). Benedict et al, Task Group 101, Med Phys 37, 4078 (2010
Choice A:<2%.
Choice B:2 - 5%.
Choice C:5 -10%.
Choice D:10%.
Question 7: For lung SBRT of small targets, independent checks of TPS calculated monitor units (MUs)..
Reference:Das et al, Task Group 106, Med Phys 35, 4186 (2008). Benedict et al, Task Group 101, Med Phys 37, 4078 (2010)
Choice A:Should never be done because they never agree with TPS.
Choice B:Will always produce same MUs as TPS because both account for heterogeneity corrections.
Choice C:Will produce lower MUs than TPS because independent calculations fail to account for reduced scatter conditions in TPS.
Choice D:Will produce higher MUs because scatter is missing in independent calculations.
Choice E:Will produce higher MUs because independent calculations are 2D and TPS is 3D.
Question 8: Which of the following QA tests must be an integral part of SRS/SBRT commissioning since it validates all three systems: imaging, treatment planning and image guidance:
Reference:Das et al, Task Group 106, Med Phys 35, 4186 (2008). Benedict et al, Task Group 101, Med Phys 37, 4078 (2010)
Choice A:Fusion QA.
Choice B:Dose Output QA.
Choice C:IMRT QA.
Choice D:MLC Picket fence QA.
Choice E:End to End QA.
Question 9: Detector size impacts all of the following SRS commissioning measurements except:
Reference:Das et al, Task Group 106, Med Phys 35, 4186 (2008). Benedict et al, Task Group 101, Med Phys 37, 4078 (2010)
Choice A:Output factors.
Choice B:Penumbra.
Choice C:PDD.
Choice D:Beam Profile.
Choice E:FWHM.
Question 10: Good practice recommendation to ensure accuracy of small field output factors measured in your clinic is to use...
Reference:Das et al, Task Group 106, Med Phys 35, 4186 (2008). Benedict et al, Task Group 101, Med Phys 37, 4078 (2010)
Choice A:One Ion Chamber.
Choice B:Any one ion chamber + one diode.
Choice C:Two ion chambers + one diode.
Choice D:One ion chamber + two diodes.
Choice E:Trust your instincts!
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