AbstractID: 9635 Title: Evaluation of an Independent Dose
Verification Program for HDR Planning
A comprehensive evaluation of an in-house independent dose verification program for high dose rate
(HDR) brachytherapy plans has been performed to determine its accuracy and ability to detect
potential errors in HDR treatment planning. The independent check program utilizes the point
source and line source approximation based on AAPM TG-43. The line source approximation
method treats an HDR source train of active length L in an implant catheter, with variable dwell
times at different dwell positions, as a linear source with its total dwell time uniformly distributed
along its active length. The point source approximation method treats the HDR source train as an
effective point source, located at a point on the source train L/4 cm from its mid-point. Given this
assumption, dose at a point in the central plane is a function of source length L, and distance d from
the dose calculation point to the mid-point of the catheter. Dose in cGy per 1000 Ci-sec is calculated
as a function of L and d, and the resultant tabulated in a look-up table. Point doses for multi-catheter
implant are summed to provide the cumulative point dose. All results are provided on a spreadsheet
for quick verification and patient chart documentation. This technique has been fully investigated
for accuracy. Dose discrepancy between computer and manual calculation is usually within 3%.
Errors such as incorrect dwell position spacing or inter-catheter spacing can be detected. This
method has been fully commissioned and used as an independent check for all our HDR treatments.