# Calculating exposure / dose from cross sections

1. Aug 13, 2014

### TauDay

Given a monoenergetic beam of photons, how are the interaction cross sections used to calculate a) the dose rate to a small volume of tissue, and b) the exposure rate.

I assume this question references the below equations:

$$\dot{D} = \theta ( \frac{μ}{ρ} )_{med} * E_{ab}$$

$$\dot{X} = \theta ( \frac{μ}{ρ} )_{air} * E_{γ}$$

2. Aug 23, 2014

### Staff: Mentor

Does one have a textbook from which equations were taken.

In looking at dose and exposure, one must keep in mind that the some radiation passes through a volume without reacting. One would use a Monte Carlo code to track the radiation through a volume and count the interactions in the volume as well as the total radiation passing through.

One is interested in the radiation absorbed, i.e., the radiation that interacts with the matter in the volume.