1. High energy photon beams from an accelerator require flattening filters in order to _____.
A. increase low-energy photons
B. correct for the pulsing of radiation
C. increase fluence along the central axis of the beam
D. increase depth dose
E. make the beam flat across the full field
2. The equivalent square of a 10 x 20-field is _____.
A. 12 x 12
B. 13 x 13
C. 15 x 15
D. 18 x 18
E. 20 x 20
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.
A. 245 cGy
B. 255 cGy
C. 261 cGy
D. 268 cGy
E. 281 cGy
( %DD for 100 cm SSD, 5-cm depth 87%
%DD for 100 cm SSD, 10-cm depth 68%
TMR 5-cm depth 0.93
TMR 10-cm depth 0.79
TMR 15-cm depth 0.65
TMR 20-cm depth 0.53 )
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.
A. 0.45
B. 0.51
C. 0.55
D. 0.57
E. 0.59
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.
A. 0.28
B. 2.8
C. 28
D. 280
E. 2800
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.
A. 0.6
B. 1
C. 3
D. 30
E. 300