jroque10
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Which region of a gas-filled detector's voltage response curve is characterized by incomplete charge collection due to ion recombination?
A. Ionization region
B. Recombination region
C. Proportional region
D. Geiger-Müller region
B
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Which of the following radionuclides is MOST likely to exhibit an iodine escape peak in its gamma-ray spectrum when measured with a NaI(Tl) detector?
A. I-131
B. Tc-99m
C. F-18
D. C-11
A
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What is the PRIMARY advantage of using a semiconductor detector for gamma-ray spectrometry compared to a NaI(Tl) detector?
A. Higher detection efficiency
B. Lower cost and greater availability
C. Superior energy resolution
D. Greater sensitivity to low-energy radiation
C
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Which of the following techniques is MOST effective in reducing the radiation dose from an internal source, such as a radiopharmaceutical administered to a patient?
A. Increasing the distance from the patient
B. Using lead shielding to attenuate gamma rays
C. Minimizing the administered activity and optimizing its biodistribution
D. Reducing the time spent in close proximity to the patient
C
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Which decay mode is responsible for the emission of two 511 keV photons in opposite directions, a characteristic signature used in PET imaging?
A. Electron capture
B. Isomeric transition
C. Positron annihilation
D. Beta-minus decay
C
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Which of the following factors is MOST likely to contribute to a decrease in the intrinsic efficiency of a scintillation detector?
A. Increasing the energy of the incident gamma rays
B. Using a thicker scintillation crystal
C. Improving the optical coupling between the crystal and the photomultiplier tube
D. Reducing the electronic noise in the detector system
A
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Which of the following statements BEST describes the purpose of a quench correction in liquid scintillation counting?
A. To compensate for variations in the sample volume
B. To account for the loss of counts due to chemical quenching or color quenching in the scintillation cocktail
C. To adjust for the background radiation levels in the counting environment
D. To correct for the dead time losses in the detection system
B
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What is the PRIMARY reason for using a molybdenum-99/technetium-99m generator system in nuclear medicine?
A. To produce short-lived PET radioisotopes
B. To generate high-energy therapeutic radioisotopes
C. To provide a readily available source of technetium-99m, a versatile and widely used diagnostic radionuclide
D. To minimize radioactive waste disposal concerns
C
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A technologist is performing a daily constancy check on a dose calibrator using a Cs-137 source. The measured activity is significantly lower than the expected value. Which of the following is the LEAST likely explanation for this discrepancy?
A. Contamination in the lining or dipper of the dose calibrator
B. A change in the geometry of the source or the detector
C. A malfunction in the voltage supply to the ionization chamber
D. Incorrect calibration settings or isotope selection
B
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Which of the following radiation quantities is MOST appropriate for estimating the risk of stochastic effects, such as cancer induction, from exposure to ionizing radiation?
A. Effective dose
B. Absorbed dose
C. Exposure
D. Air kerma
A
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Which of the following scenarios would result in the GREATEST increase in the radiation dose rate from a point source of gamma rays?
A. Doubling the distance from the source
B. Halving the distance from the source
C. Increasing the activity of the source by 50%
D. Adding a lead shield with a thickness equal to one half-value layer
B
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Which type of gas-filled detector relies on the Townsend avalanche phenomenon to produce a large output pulse for each detected radiation event?
A. Ionization chamber
B. Dose calibrator
C. Geiger-Müller counter
D. Proportional counter
C
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Which of the following statements regarding the biological effects of ionizing radiation is LEAST accurate?
A. Children are generally more susceptible to radiation-induced harm than adults.
B. High doses of radiation delivered over a short period are more damaging than the same dose spread over a longer time.
C. The concept of radiation hormesis suggests that low doses of radiation have a protective effect by stimulating DNA repair mechanisms.
D. Exposure to ionizing radiation can lead to both deterministic effects (severity depends on dose) and stochastic effects (probability of occurrence depends on dose).
C
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Which of the following practices is LEAST likely to contribute to the ALARA principle in a nuclear medicine department?
A. Wearing lead aprons and thyroid shields when handling radioactive materials
B. Storing radioactive sources in designated shielded containers when not in use
C. Using syringes with integral shielding to minimize hand exposure during injections
D. Disposing of all radioactive waste in the designated decay-in-storage area, regardless of its half-life
D
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Which of the following is a critical design feature of a well counter that contributes to its high detection efficiency?
A. The use of a thin-window detector to minimize radiation absorption
B. The incorporation of multiple photomultiplier tubes to increase light collection
C. The near-4π geometry of the detector, maximizing the capture of emitted radiation
D. The ability to perform pulse height analysis to discriminate against background radiation
C
