1) lesion at 1-cm depth in tissue is to be treated with 6-MeV electron beam with bolus. A dose of 1.5 Gy to 80% is prescribed. If output is 1cGy/MU, SSD is 104 cm and cone factor is 0.8, what should the thickness of the bolus be, and how many MU should be delivered?
ANSWER: C. 0 cm, 170 MU
2) Which of the following is true regarding geometric penumbra?
ANSWER: A. It increases as source diameter increases.
3) To achieve a standard deviation of 2%, _ counts must be collected.
ANSWER: C. 2500
4) All of the following reduce resolution in positron emission tomography (PET) except:
ANSWER: D. Size of the focal spot.
5) Which parameter(s) change as a result of coherent scatter of a photon from an atom?
ANSWER: C. Direction of travel.
6) Which imaging modality would allow one to distinguish an artificial diamond made of zirconium oxide ZrO2 (zirconium has atomic number 40) from a natural one made of carbon atoms (atomic number 6)?
ANSWER: B. Diagnostic X-rays.
7) Which of the following is not true regarding pair production?
ANSWER: A. The threshold photon energy is 0.511 MeV
8) The maximum number of photoelectrons produced in a photoelectric interaction by a single photon with incident energy of 150 keV is _.
ANSWER: A. 1
9) The mass attenuation coefficients for most materials (except hydrogen) are similar when _ interactions predominate.
ANSWER: B. Compton
10) A superficial x-ray treatment is prescribed with a 2 mm A1 filter. By mistake, a 1 mm filter is used All of the following will occur except:
ANSWER: D. Increased PDD.