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1. High energy photon beams from an accelerator require flattening filters in order to _____.
ANSWER: E. – make the beam flat across the full field
2. The equivalent square of a 10 x 20-field is _____.
ANSWER: B. – 13 x 13
3. A single field 6-MV beam is used to deliver 200 cGy at the isocenter (100 cm SAD), which is at a depth of 10 cm. The patient thickness is 20 cm. Using the factors given below, calculate the dose at 5-cm depth.
ANSWER: C. 261 cGy
4. A batch of 1-125 seeds is ordered so that the activity will be 0.48 mCi/seed on the day of the prostate implant. If the seeds arrive 5 days before the implant, the expected activity on receipt is _____ mCi/seed.
ANSWER: B. 0.51
5. At a radiologist’s workstation, the instantaneous exposure rate through the wall from a chest cassette holder is 500 mR/h during exposures of 10 mAs at 100 kV and 100 mA. The maximum exposure at the workstation during 1 week for 200 exposures would be approximately _____ mR.
ANSWER: B. 2.8
6. A radiation worker standing for 3 hours at 1 meter from a 5 mCi radioactive source. for which Ã=2.0 R.cm2/mCi-hr, will be exposed to about _____ mR.
ANSWER: C. – 3