Units of Measure for Radiation

DOE-HDBK-1130-98

Module 1: Radiological Fundamentals

Instructor's Notes

EO7 Identify the units used

to measure radiation.

1. Roentgen (R)

Is a unit for measuring external exposure.

b. Defined only for effect on air.

c. Applies only to gamma and X rays.

d. Does not relate biological effects of radiation to the human

body.

1 R (Roentgen) = 1000 milliroentgen (mR).

2. Rad (Radiation absorbed dose)

Absorbed dose results from

energy being deposited by

A unit for measuring absorbed dose in any material.

the radiation.

b. Is defined for any material.

c. Applies to all types of radiation.

d. Does not take into account the potential effect that

different types of radiation have on the body.

1 rad = 1000 millirad (mrad).

3. Rem (Roentgen equivalent man)

A unit for measuring dose equivalence.

b. Is the most commonly used unit.

c. Pertains to the human body.

d. Takes into account the energy absorbed (dose) and the

biological effect on the body due to the different types of

radiation.

The Quality Factor (QF) is used as a multiplier to reflect

the relative amount of biological damage caused by the

same amount of energy deposited in cells by the different

types of ionizing radiation. Rem = rad x QF.