B-G meaning in Medical ?

What is Bragg-Gray cavity theory mean?

Bragg-Gray cavity theory relates the radiation dose in a cavity volume of material g {\displaystyle g} to the dose that would exist in a surrounding medium m {\displaystyle m} in the absence of the cavity volume. It was developed in 1936 by British scientists Louis Harold Gray, William Henry Bragg, and William Lawrence Bragg.

Most often, material g {\displaystyle g} is assumed to be a gas, however Bragg-Gray cavity theory applies to any cavity volume (gas, liquid, or solid) that meets the following Bragg-Gray conditions.

The dimensions of the cavity containing g {\displaystyle g} is small with respect to the range of charged particles striking the cavity so that the cavity does not perturb the charged particle field. That is, the cavity does not change the number, energy, or direction of the charged particles that would exist in m {\displaystyle m} in the absence of the cavity.The absorbed dose in the cavity containing g {\displaystyle g} is deposited entirely by charged particles crossing it.

When the Bragg-Gray conditions are met, then

D m = D g ⋅ ( S ρ ) ¯ g m {\displaystyle D_{m}=D_{g}\cdot {\bar {{\Bigl (}{\frac {S}{\rho }}{\Bigr )}}}_{g}^{m}} ,< reference nan