A Health Care Personnel Guide For Assessing Radiation Risk And Selecting Imaging Procedures In Pregnant Women Easy-print edition of this Guide

This reference material is for use by medical staff affiliated with Brigham and Women's Hospital only. It is designed to inform your decision-making as you determine individual risks associated with medical imaging and communicate with your patients. It should not be interpreted as medical advice, nor is it necessarily germane to institutions using other imaging protocols. Patients with questions regarding these issues should speak directly with their caregivers. An additional resource is the Ask the Experts-Pregnancy and Radiation module of the Health Physics Society: http://www.hps.org
Glossary of Radiation Units

Absorbed Dose:The energy imparted by ionizing radiation per unit mass of irradiated material.

Becquerel (Bq): A SI unit of radioactivity. One Bq=1 disintegration per second. One million Bq=1 MegaBecquerel (MBq).

Curie (Ci): A traditional unit expressing the quantity of radioactivity. One Ci=3.7E+10 nuclear disintegrations per second. A milliCurie (mCi)=1/1000 Ci

Gray (Gy): A SI unit of absorbed dose. One Gy=100 rads. One milliGray (mGy)=1/1000 Gy.

Ionizing Radiation: Any radiation capable of displacing electrons from an atom, thereby producing ions. Examples: alpha, x-rays, gamma, beta, positron, and neutrons.

mCi vs. MBq: The conversions between the two radioactivity units are;
1 mCi = 37 MBq, and, 1 MBq = 0.027 mCi.

mrad vs. mGy: The conversions between the two absorbed dose units are;
1 mGy = 100 mrad, and, 1 mrad = 0.01 mGy.

Rad: A traditional unit of absorbed dose. One millirad (mrad) = 1/1000 rad.

Rem: A traditional unit of effective dose. A rem = (rad)(quality factor), where the quality factor (QF) is an indication of the potency of each type of radiation. Photons and beta particles have a QF=1, alpha particles=20.

Sievert: When the absorbed dose in grays is multiplied by the radiation QF, the result is the equivalent dose in sieverts (Sv). One Sv=100 rem. One milliSievert (mSv)=1/1000 Sv.