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Sourced by Dr.M. Akhtaruzzman, Editor (Scientific), AFOMP Pulse
1. The loss of contrast in a therapy verification image compared with a simulator radiographic image is mostly a result of _____.
A. an increased number of pair productions
B. an increased number of Compton interactions
C. an increased number of photoelectric interactions
D. a decreased number of photoelectric interactions
ANSWER: D
2. A 4-MV linac beam, 10 cm x 10 cm with a 45° wedge, is used to deliver 200 cGy to a tumor located at the isocenter (100 cm SAD) at 10-cm depth. Given the following:
1. output at 100 cm SSD at d max 1.2 cm is 1.04 cGy/MU
2. wedge factor 0.70
3. back-scatter-factor 1.03
4. percent depth dose 60%
5. tissue-air-ratio 0.75
What is the number of monitor units (MU) required for this treatment?
A. 206
B. 258
C. 296
D. 366
ANSWER: D
3. AAPM’ Report 85 on “Tissue Inhomogeneity Corrections For Megavoltage Photon Beams”(2004) draws some general conclusions. All of the following are true statements except:
A. The widespread availability of CT and 3-D planning systems makes inhomogeneity corrections more accurate than was previously possible.
B. Inhomogeneity corrections should account for changes in the electron densities of tissues traversed.
C. Because different treatment planning systems use different inhomogeneity algorithms, making such corrections will introduce even larger errors in dose reporting than were previously made without them.
D. Monte Carlo dose calculations can calculate the effects of inhomogeneities on scatter radiation, whereas analytical dose calculations only correct for changes in effective depth.
ANSWER: C
4. After 10 half-lives the activity A of a radionuclide is reduced to approximately:
A. A/10
B. Ae1/10
C. A/1000
D. Zero
ANSWER: C
5. Which of the following is true, regarding patients scanned on a PET-CT unit?
A. Patients should remain in a shielded room after the scan for the rest of the day, and are then released with specific radiation precautions.
B. When the dose rate at 1 meter is less than 5 mR/hr, patients can be released with no radiation precautions.
C. Patients can be released immediately after the scan, but must not share a bathroom with other people for 1 week.
D. Patients are released when the dose rate at 1 meter is less than 2mR/hr, but must avoid contact with children for l week.
ANSWER: B
6. In pair production, _____.
A. the electrons and positrons are emitted at 180° to each other
B. positrons and antineutrinos are produced when the interactions occur
C. photons with energies greater than 2.04 MeV are necessary for the interactions to occur
D. the annihilation of the positron produces two photons that travel in approximately opposite directions
ANSWER: D
7. A neutral atom has 6 electrons and a mass number of t3. The number of neutrons in the nucleus is _____.
A. 13
B. 6
C. 7
D. 19
ANSWER: C
8. Activity can be expressed as:
A. ∆N/∆t
B. 0.693/T1/2
C. 0.693/HVL
D. 1.44/T1/2
ANSWER: A
9. Which of the following is true for low-level radioactive wastes, such as tubing and swabs contaminated with Tc-99m?
A. They can never be thrown away since some activity always remains.
B. They can be thrown away immediately since the amount of activity is generally harmless.
C. They can only be disposed of by a commercial rad-waste service,
D. They can be stored until reaching background levels and then disposed of with other medical trash.
ANSWER: D
10. According to NCRP Repot 93. the average annual dose from man-made and natural radiation in the United States is 360 mrem. The largest contributor to this value is:
A. Radon and its daughters.
B. Nuclear weapons testing.
C. Medical X-rays.
D. Natural radiation sources excluding radon.
ANSWER: A