absorbed dose

The gray is a special name for joule per kilogram, to be used as the coherent SI unit for absorbed dose.

where $\text{d}m$ is the element of mass of the irradiated matter.

In the limit of a small domain, the mean specific energy $\overline{z}=\frac{\Delta \overline{\epsilon }}{\Delta m}$ is equal to the absorbed dose $D$ .

The absorbed dose can also be expressed in terms of the volume of the mass element by:

where $\rho$ is the mass density of the mass element.

In report 85a of the ICRU a definition with an equivalent meaning is given as:

The absorbed dose, $D$ , is the quotient of $\text{d}\overline{\epsilon }$ by $\text{d}m$ , where $\text{d}\overline{\epsilon }$ is the mean energy imparted by ionizing radiation to matter of mass $\text{d}m$ :