. Author manuscript; available in PMC: 2017 Jan 1.

Published in final edited form as: Trends Cardiovasc Med. 2015 Apr 15;26(1):55–65. doi: 10.1016/j.tcm.2015.04.005

Table 1.

Common radiation dose metrics

Metric	Description	Unit
Radioactivity	Atom decay/time	curie (Ci) becquerel (Bq)
Exposure	Total charge of ions traveling through air	roentgen (R)
	Kerma: Sum of kinetic energy of charged particles liberated per unit mass
Metrics Reflecting Kinetic Energy	- Incident air kerma: Kerma to air from an incident X-ray beam at the patient/phantom surface without backscatter included	gray (Gy)
	- Entrance surface air kerma: Kerma to air at the patient/phantom surface including backscatter	gray (Gy)
	- Air kerma-area product: Integral of air kerma over the area of the xray beam (independent of distance)	Gy-m²
	- Air kerma-length product: Integral of air kerma over a line of length	Gy-m
Absorbed dose	Radiation deposited in tissue per unit weight	gray (Gy)
Metrics Reflecting Biologic effects	-Equivalent dose: Multiplies dose with a radiation weighting factor to account for relative biological effect. -Effective dose: Weighted sum of equivalent doses. Accounts for biological effectiveness and tissue sensitivity by multiplying equivalent dose with a tissue sensitivity weighting factor	sievert (Sv)