Computed Tomography Test CT Radiation Safety and Dosimetry

Question 1

Which unit is used to express the effective radiation dose received by a patient during a CT scan?

Accepted Answer

Millisievert (mSv)

Answer

Millisievert (mSv) is the SI unit used to express effective dose, which accounts for the biological effect of radiation on different tissues.

Question 2

What does the term CTDI stand for in CT radiation dosimetry?

Accepted Answer

Computed Tomography Dose Index

Answer

CTDI (Computed Tomography Dose Index) is a standardized measure of radiation dose output from a CT scanner for a single rotation.

Question 3

Which principle of radiation protection states that doses should be kept as low as reasonably achievable?

Accepted Answer

ALARA

Answer

ALARA (As Low As Reasonably Achievable) is the guiding principle for minimizing radiation exposure to patients and staff.

Question 4

Increasing the mAs in CT by a factor of 4 will have what effect on image noise?

Accepted Answer

Reduce noise by 50%

Answer

Since noise is proportional to 1/√mAs, quadrupling mAs reduces noise by half (√4 = 2).

Question 5

What is the primary purpose of using automatic exposure control (AEC) in CT?

Accepted Answer

Adapt tube current to patient size and anatomy

Answer

AEC (also called tube current modulation) automatically adjusts mA based on patient attenuation to optimize image quality while minimizing dose.

Computed Tomography Test Practice Test