- A patient is prescribed to a depth of 5 cm using a single 6 MV x-ray beam. If 15 MV is prescribed instead:
ANSWER: D. exit dose will increase
- A patient is treated on a linac (100 cm SAD) with a field adjacent to a previously treated field. The previous field has a collimator setting of 22 x 22 cm 2, 110 cm SSD. The current field has a collimator setting of 10 x 10 cm 2, 100 cm SSD. What gap is required at the skin for these fields to intersect at 5 cm depth?
ANSWER: D. 0.80
- Which of the following detectors would be the best one lo locate a dropped I-125 seed?
ANSWER: E. Geiger counter
- Based on the ICRP 60 (1990) and BEIR V (1990) reports, what whole-body dose delivered to a large group of people would result in the death of 50% of the group within 60 days, without medical intervention?
ANSWER: C. 450 cGy
- An electron, a proton, and an alpha particle each have 20 MeV kinetic energy. Which of the following statements is true?
ANSWER: D. The electron travels almost at the speed of light.
- A new isotope Cs-131 with a half-life of approximately 10 days can be used for permanent implants If the activity of a calibration seed is 1.000 mCi on a given day and time, the activity 24 hours prior to this time is_____ mCi.
ANSWER: C. 1.072
- Why don’t electrons ever get invited to medical physics parties?
ANSWER: B. They are too negative