Simple experimentally derived algorithm for computer calculated dose rates associated with 137Cs gynecologic insertions.

A simple mathematical algorithm is derived from experimental data for dose rates from 137Cs sources in a finite tissue equivalent medium corresponding to the female pelvis. An analytical expression for a point source of 137Cs along with a simple numerical integration routine allows for rapid as well as accurate dose rate calculations at points of interest for gynecologic insertions. When compared with theoretical models assuming an infinite unit density medium, the measured dose rates are found to be systematically lower at distances away from a single source; 5 per cent at 2 cm and 10 per cent at 7 cm along the transverse axis. Allowance in the program for print out of dose rates from individual sources to a given point and the feature of source strength modification allows for optimization in terms of increasing the difference in dose rate between reference treatment points and sensitive structures such as the bladder, rectum and colon.