FRCR FRCR Physics and Radiation Safety 2

Question 1

What is the annual occupational whole-body effective dose limit recommended by the NCRP for radiation workers in the US?

Accepted Answer

50 mSv

Answer

The NCRP (Report No. 116) recommends a 50 mSv annual effective dose limit for radiation workers, with a lifetime limit of 10 mSv × age.

Question 2

The photoelectric effect is enhanced by which factor in tissue?

Accepted Answer

Atomic number cubed (Z³)

Answer

The photoelectric effect varies approximately as Z³/E³, so higher atomic number materials absorb far more radiation, explaining contrast with iodine and barium.

Question 3

What is the purpose of added filtration in a diagnostic X-ray tube?

Accepted Answer

Remove low-energy photons that add dose without contributing to image

Answer

Added filtration (typically aluminum) removes low-energy photons that would be absorbed by the patient without contributing useful diagnostic information.

Question 4

Radiographic grids are used primarily to:

Accepted Answer

Reduce scattered radiation reaching the detector

Answer

Grids selectively absorb off-axis scatter before it reaches the image receptor, improving image contrast at the cost of increased patient dose.

Question 5

Which phenomenon describes the increase in patient skin dose when the X-ray tube is operated close to the skin?

Accepted Answer

Inverse square law effect

Answer

As the source-to-skin distance decreases, the inverse square law causes a rapid increase in dose rate at the skin surface.

FRCR - Fellow of the Royal College of Radiologists Practice Test

FRCR - Fellow of the Royal College of Radiologists Practice Test

FRCR FRCR Physics and Radiation Safety 2