Computed Tomography Test CT Radiation Safety and Dosimetry 2 — Questions and Answers
Question 1: The DLP (Dose Length Product) in CT is calculated by multiplying CTDI_vol by which parameter?
- Scan length (Correct answer)
- Slice thickness
- Rotation time
- Pitch factor
Correct answer: Scan length
DLP = CTDIvol × scan length (in cm), providing an estimate of total energy deposited during the entire CT examination.
Question 2: Which of the following best describes the dose profile of a helical CT scan with a pitch greater than 1?
- Gaps exist between dose profiles from successive rotations (Correct answer)
- Overlapping dose profiles occur
- Dose is uniformly distributed
- Patient dose is eliminated
Correct answer: Gaps exist between dose profiles from successive rotations
A pitch >1 means the table moves faster than one detector width per rotation, creating gaps in the dose profile and generally reducing patient dose.
Question 3: In CT, which body region is most sensitive to radiation-induced cancer risk?
- Bone marrow and gonads (Correct answer)
- Brain
- Extremities
- Skin
Correct answer: Bone marrow and gonads
Bone marrow and gonads have the highest tissue weighting factors (wT), making them most sensitive to stochastic radiation-induced cancer risk.
Question 4: What is the recommended lead apron shielding thickness to protect gonads from scattered CT radiation?
- 0.5 mm lead equivalent (Correct answer)
- 0.1 mm lead equivalent
- 2.0 mm lead equivalent
- No shielding is needed
Correct answer: 0.5 mm lead equivalent
A 0.5 mm lead equivalent apron is standard for gonadal shielding, though its effectiveness in CT is debated due to scatter from all directions.
Question 5: Which population group requires the most careful dose optimization in CT due to higher radiation sensitivity?
- Pediatric patients (Correct answer)
- Elderly patients
- Athletic adults
- Male patients
Correct answer: Pediatric patients
Children are more radiosensitive than adults and have more years of life remaining in which radiation-induced cancers could develop, requiring strict dose minimization.
Question 6: What does the size-specific dose estimate (SSDE) correct for compared to CTDIvol?
- Patient body size and diameter (Correct answer)
- Scanner manufacturer differences
- Contrast agent type
- Scan protocol complexity
Correct answer: Patient body size and diameter
SSDE adjusts CTDIvol based on the patient's effective diameter to provide a more accurate estimate of actual patient dose.
Computed Tomography Test CT Radiation Safety and Dosimetry 2
The DLP (Dose Length Product) in CT is calculated by multiplying CTDI_vol by which parameter?