Goal: does localization affect dose?

Jun Lian, Larry Potter, K Eljabaly, Kathy Deschesne and Sha Chang

Purpose: High dose rate brachytherapy (HDR) is a very effective cancer treatment method. Localization of source positions is essential for dosimetric accuracy. Nucletron’s PLATO TPS provides multiple means to reconstruct and localize source positions. Three commonly used methods are: (1) catheter describing using film, (2) catheter tracking using film, and (3) seed identifying on CT slices. Although all of these methods have been used in the clinic, the dose variance among them is unknown. The purpose of this project is to study quantitively the dose discrepancy of these different source reconstruction methods.

Results: Dose points from CT based plan was used as a reference. When comparing plans by the source reconstruction method, we found significant dose difference on certain dose point between film based planning and CT based planning. The biggest dose difference was 10.3% on fiducial A.

Conclusion: Through a series of planning on a phantom, we found the doses can differ significantly between the film and CT based- method. At certain locations, the film based- plan may underestimate the dose.