- A patient is prescribed to a depth of 5 cm using a single 6 MV x-ray beam. If 15 MV is prescribed instead:
A. max body dose will increase
B. entrance dose will increase
C. dose to the prescription point will increase
D. exit dose will increase
E. all of the above - 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?
A. 0.68
B. 0.70
C. 0.75
D. 0.80
E. 1.02 - Which of the following detectors would be the best one lo locate a dropped I-125 seed?
A. Gas ionization type survey meter
B. Thermoluminescent dosimeter.
C. Air-equivalent wall “thimble” ionization chamber
D. Film badge.
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?
A. 1000 cGy
B. 700 cGy.
C. 450 cGy
D. 150 cGy
E. 50 cGy
- An electron, a proton, and an alpha particle each have 20 MeV kinetic energy. Which of the following statements is true?
A. The alpha particle travels at almost the speed of light.
B. The alpha particle has the least total relativistic energy (i.e.. kinetic plus rest mass energy).
C. The proton has the highest total relativistic energy
D. The electron travels almost at the speed of light.
E. None of’ the above
- 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.
A. 0.900
B. 0.933
C. 1.072
D. 1.100
E. 1.148
- Why don’t electrons ever get invited to medical physics parties?
A. They always cause a scene
B. They are too negative
C. They can’t handle the radiation
D. They always accelerate too quickly