AbstractID: 8178 Title: Implementation of a Practical Independent
Dose Verification Program for HDR Planning
A practical independent dose verification program for high dose rate brachytherapy (HDR) treatment
plans has been instituted that utilizes the manual point dose calculation based on AAPM TG-43.
The program approximates that an HDR source train of active length L in an implant catheter of
variable dwell times at different dwell positions is a line source with its total dwell time uniformly
distributed along the active length. Given this assumption the dose rate at a point in the central plane
is a function of active length L, and the distance d from the dose point to the mid-point of the line
source. In accordance with the Paterson-Parker formalism, the dose in cGy per 1000 Ci-sec is
calculated as a function of L and d, and the resultant tabulated in a two-dimensional look-up table.
Both L and d are easily obtained from the treatment plan, and the point dose from the line source can
be quickly calculated. For an implant with multiple catheters, doses from each catheter are summed
to provide the cumulative point dose. A computer spreadsheet has been developed to provide quick
verification dose calculations and appropriate documentation for the chart. This practical technique
has been fully commissioned and used as an independent calculation for breast, prostate, and vaginal
cylinder HDR treatments, and the difference between computer plans and manual methods is usually
within +/- 3%. This program has been designed for the Varian Vari-Source, however the
methodology can be directly applied to other vendors.