Dose Measurement

Question 1

Used to describe the reconstructed CT section

Answer 1

Slice sensitivity profile (SSP).

Question 2

The section of tissue exposed to ionizing radiation. It is greater in width than the SSP.

Answer 2

Dose profile.

Question 3

Term to describe the ability of x-rays to ionize a volume of air.

Answer 3

Exposure.

Question 4

What unit is exposure measured in?

Answer 4

Roentgens (R).

Question 5

The amount of x-ray energy absorbed in a unit of mass

Answer 5

Absorbed dose.

Question 6

What unit is absorbed dose measured in?

Answer 6

Grays (Gy).

Question 7

Describes the amount of radiation absorbed in a quantity of air.

Answer 7

Air kerma.

Question 8

Accounts for the type of tissue that the radiation is deposited in. Different tissues are assigned weighting factors based on their individual radiosensitivity.

Answer 8

Effective dose (EfD).

Question 9

Effective dose approximates the relative risk from exposure to ionizing radiation. It is measured in

Answer 9

Sieverts (Sv).

Question 10

The CT dose index (CTDI) is

Answer 10

An approximate measure of the dose received in a single CT section or slice. It is calculated for the central slice in a series that is surrounded by 7 slices on each side.

Question 11

CTDI is measured by

Answer 11

Performing scans of both head and body sized CT phantoms using specific technical parameters. A radiation dosimeter, such as an ionization chamber is placed within each phantom during the scans. The exposure measured by the dosimeter is used to calculate the CTDI for each acquisition.