| Question 1: Which of the following single set of equipment is required for machine specific reference dosimetry? |
| Reference: | IAEA, "Dosimetry of Small Static Fields Used in External Beam Radiotherapy." Volume 483 of Technical Report Series, IAEA, Vienna (2017). |
| Choice A: | A variety of solid state detectors and small ionization chambers, a water phantom, a measuring assembly (electrometer) and stability check devices. |
| Choice B: | Reference-class ionization chambers, a solid phantom, a measuring assembly (electrometer), stability check devices, calibrated thermometer and barometer. |
| Choice C: | A two-dimensional detector array, build-up and backscatter material, a measuring assembly (electrometer) and stability check devices. |
| Choice D: | Reference-class ionization chambers, a water phantom, a measuring assembly (electrometer), stability check devices, calibrated thermometer and barometer. |
| Question 2: There are several issues associated with reference dosimetry of FFF beams but accurate calibration can still be realized. Select the incorrect answer. |
| Reference: | McEwen et al, "Addendum to the AAPM's TG-51 protocol for clinical reference dosimetry of high-energy photon beams." Med. Phys. 41: 041501, (2014). |
| Choice A: | Use %dd(10)x to accurately select kQ for FFF beams. |
| Choice B: | Use a chamber with volume less than 0.02 cm^3. |
| Choice C: | Use Prp, the correction for radial profile (field flatness) or a short reference-class chamber to minimize variations in field flatness over the detector sensitive volume. |
| Choice D: | Determine the appropriate ion recombination correction for the FFF beam. |
| Question 3: The AAPM WGTG51 is drafting an addendum to TG-51 for electron beam reference dosimetry. They are considering recommending the use of cylindrical chambers for reference dosimetry of all electron beams, even with energy less than 6 MeV. One of the main reasons for this is: |
| Reference: | Muir and Rogers, "Monte Carlo calculations of electron beam quality conversion factors for several ion chamber types," Med. Phys. 41:111701, 2014. |
| Choice A: | Cylindrical chambers are not as stable as plane-parallel chambers. |
| Choice B: | Perturbation corrections for cylindrical chambers are variable for similar chambers. |
| Choice C: | Beam quality conversion factors, kQ, for cylindrical ion chambers are now well known from Monte Carlo calculations. |
| Choice D: | Clinical medical physicists are not comfortable using cylindrical chambers for electron beam reference dosimetry. |
| Question 4: Indicate the single set of two largest contributors to small field output correction factor and its uncertainty for a cylindrical, air-filled ionization chamber |
| Reference: | IAEA, "Dosimetry of Small Static Fields Used in External Beam Radiotherapy." Volume 483 of Technical Report Series, IAEA, Vienna (2017). |
| Choice A: | The stopping power ratio water-to-air and the central electrode effect |
| Choice B: | The stopping power ratio water-to-air and the chamber wall effect |
| Choice C: | The fluence perturbation effect and the volume averaging effect |
| Choice D: | The stopping power ratio water-to-air and the volume averaging effect |
| Choice E: | The ionization chamber wall effect and the stem effect |
| Question 5: In the figure which orientation is the correct orientation for measurements of beam profiles using solid state detectors? |
| Reference: | IAEA, "Dosimetry of Small Static Fields Used in External Beam Radiotherapy." Volume 483 of Technical Report Series, IAEA, Vienna (2017). |
| Choice A: | a |
| Choice B: | b |
| Choice C: | c |
| Question 6: Indicate the correct statements regarding the response of microchambers, diodes and diamond detectors in the following: |
| Reference: | (1) IAEA, "Dosimetry of Small Static Fields Used in External Beam Radiotherapy." Volume 483 of Technical Report Series, IAEA, Vienna (2017). (2) De Coste et al , "Is the PTW 60019 microDiamond a suitable candidate for small field reference dosimetry?" Phys Med Biol 62: 7036 – 7055 (2017). |
| Choice A: | Cylindrical air-filled microionization chambers under-respond in small fields (1 cm x 1 cm and smaller) relative to the reference field |
| Choice B: | Unshielded diodes show, relative to intermediate fields (3 cm x 3 cm), detector over-response in large fields (15 cm x 15 cm) as well as in small fields (5 mm x 5 mm) |
| Choice C: | With shielded diodes, relative to smaller fields the detector overresponse is suppressed in large fields (15 cm x 15 cm) |
| Choice D: | Microdiamond detectors under-respond in small fields (4 mm x 4 mm and smaller) |
| Choice E: | Microdiamond detectors show a modest over-response in fields between 4 mm x 4 mm and 15 mm x 15 mm |
| Choice F: | All of the above statements are correct |
