| Question 1: A typical electronic portal imaging device based on amorphous silicon detector technology will demonstrate: |
| Reference: | Greer PB and Popescu CC. Dosimetric properties of an amorphous silicon electronic portal imaging device for verification of dynamic intensity modulated radiation therapy. Medical Physics 30(7):1618-27, 2003.
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| Choice A: | A linear dose response relationship. |
| Choice B: | A linear-quadratic dose response relationship. |
| Choice C: | No energy dependence. |
| Choice D: | None of the above. |
| Question 2: Which of the following statements about small, undesired EPID displacements ("flex") is most correct. |
| Reference: | Mans A, Remeijer P, Olaciregui-Ruiz I, et al. 3D Dosimetric verification of volumetric-modulated arc therapy by portal dosimetry. Radiotherapy and Oncology 94(2):181-187, 2010.
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| Choice A: | EPID flex is constrained by manufacturers to be less than 1 mm, and is therefore insignificant and requires no software compensation. |
| Choice B: | EPID flex is always compensated for by the software application. |
| Choice C: | EPID flex has been reported to be up to 4 mm and may require compensation. |
| Question 3: Flood-field calibration of an EPID: |
| Reference: | Boriano A, Lucio F, Calamia E, Russi E, and Marchetto F. A new approach for the pixel map sensitivity (PMS) evaluation of an electronic portal imaging device (EPID). Journal of Applied Clinical Medical Physics 14: 234–250, 2013. |
| Choice A: | Determines the absolute dose response relationship for each pixel in the imager panel using a large open field. |
| Choice B: | Smooths the detector-to-detector response differences using a large open field, and assumes the open field has a flat dose distribution over a large area. |
| Choice C: | Is only useful for imaging applications and is not applied when performing portal dosimetry or linac. |
| Question 4: A major potential source of artifacts in EPID-based VMAT dose reconstruction is:
|
| Reference: | McCowan et al. Clinical Implementation of a Model-Based In Vivo Dose Verification System for Stereotactic Body Radiation Therapy-Volumetric Modulated Arc Therapy Treatments Using the Electronic Portal Imaging Device. Int J Radiat Oncol Biol Phys. 2017 Apr 1;97(5):1077-1084.
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| Choice A: | Frame-averaging artifacts. |
| Choice B: | Partial volume effects. |
| Choice C: | Kernel artifacts. |
| Choice D: | None of the above. |
| Question 5: One advantage of using EPID over ion-chamber matrix detectors is:
|
| Reference: | McCowan et al. Clinical Implementation of a Model-Based In Vivo Dose Verification System for Stereotactic Body Radiation Therapy-Volumetric Modulated Arc Therapy Treatments Using the Electronic Portal Imaging Device. Int J Radiat Oncol Biol Phys. 2017 Apr 1;97(5):1077-1084. |
| Choice A: | Water equivalent. |
| Choice B: | Can capture larger treatment fields. |
| Choice C: | Higher resolution. |
| Question 6: For newer linacs, the EPID mechanical flex or sag, due to gravity, is on the order of:
|
| Reference: | Rowshanfarzad et al. Detection and correction for EPID and gantry sag during arc delivery using cine EPID imaging. Med Phys. 2012 Feb;39(2):623-35 |
| Choice A: | 1cm. |
| Choice B: | 1mm. |
| Choice C: | None of the Above. |
| Question 7: A Pixel sensitivity map is often applied to raw EPID images to correct:
|
| Reference: | Greer PB, Correction of pixel sensitivity variation and off-axis response for amorphous silicon EPID dosimetry. Med. Phys. 32 (12), December 2005
|
| Choice A: | Background noise. |
| Choice B: | Ghosting effect. |
| Choice C: | Variations in pixel response. |
| Choice D: | All of the above. |
| Choice E: | None of the above. |
| Question 8: Beam profile changes measured on a 2D detector array (EPID or ionization chamber) are sensitive to photon beam energy change and can be used as a metric for photon energy verification:
|
| Reference: | Gao S, Balter PA, Rose M, Simon WE. Measurement of changes in linear accelerator photon energy through flatness variation using an ion chamber array. Med Phys 40(4):042101, 2013. Dawoud SM, Weston SJ, Bond I, Ward GC, Rixham PA, Mason J, Huckle A, Sykes JR. Measuring linac photon beam energy through EPID image analysis of physically wedged field. Med. Phys. 41 (2), 2014.
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| Choice A: | True. |
| Choice B: | False. |
| Question 9: What does TG-100 recommend for making adjustments to your existing QA program based on new paradigms for quality and safety? |
| Reference: | Huq et al. The report of the Task Group 100 of the AAPM: Application of risk analysis methods to radiation therapy quality management. Med Phys 43(7):4209-4262, 2016. |
| Choice A: | When making large changes to your existing QA program, it is best to do it all at once. |
| Choice B: | You should only make small, incremental changes to your existing QA program over many years. |
| Choice C: | Do not make sudden, major changes to your existing QA program. |
| Choice D: | One should never change their existing QA program. |
| Question 10: When evaluating QA data from equipment or processes against a quality indicator (e.g., daily linac output QA), what is good description of tolerance levels or limits for the quality indicator?
|
| Reference: | Pawlicki et al. The Systematic Application of Quality Measures and Process Control in Clinical Radiation Oncology. Semin Radiat Oncol 22:70-76, 2012.
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| Choice A: | A quantitative description of the degree of adherence to a quality indicator. |
| Choice B: | The boundary within which the process is considered operating normally. |
| Choice C: | A requirement for the average performance of a process. |
| Choice D: | The degree to which measured quantities in the clinic are allowed to vary without risking harm to the patients. |
