Stepping source prostate brachytherapy: From target definition to dose delivery

Brachytherapy is an effective way to treat tumours locally and conformally, and is widely used in the treatment of prostate cancer. Prior to the treatment, a CT or MRI scan is acquired. The use of MRI led to a mean increase of 3% in dose coverage of the target volume (chapter 2). Although this seems limited, in some cases the use of MRI resulted in an increase in target coverage of 5%-10%.
During the treatment, deviations from the planned dose can occur. A minor decrease of in target coverage was measured (chapter 3). Rectum and bladder doses increased during the treatment, which should be taken into account during treatment planning.
The change in distance between the catheters was used to derive a mean increase of 4% in prostate volume, ranging from -10% to +16% (chapter 4). These measurements reaffirm the stability of the prostate implants used for the PDR treatments, which guarantees safe and reliable delivery of the planned dose.
Two novel tools for treatment plan optimization of temporary implant brachytherapy are presented (chapter 5). EGO creates a dose distribution that is as homogeneous as possible across the implant. With IIP the user subsequently shapes the dose distribution according to the patient’s anatomy by (local) adaptations of the dose. Four treatment planning methods are compared using 26 prostate implants (chapter 6). Planning time was shortest with the automated methods. Differences in DVH parameters were small, but the inverse methods, including EGO-IIP, showed a slight advantage as compared to graphical optimization.