Preview

PDF, English - main document Download (17MB) | Terms of use

Abstract

During low-dose-rate brachytherapy radioactive seeds are inserted into a tumor using hollow needles. Treatment planning refers to defining seed positions such that dose parameters for both the target and the organs at risk obey certain constraints. State-of-the-art planning techniques allow to intra-operatively update the plan with actual seed positions, but do not consider seed placement uncertainties and resulting dose deviations beforehand. We propose two strategies to be included in treatment planning, which can help to overcome the need for frequent plan updating. Firstly, a needle insertion simulation is introduced, without the necessity for boundary conforming meshing using an embedded domain method. Secondly, we quantify seed placement sensitivity by calculating the gradients of the dose parameters with respect to the seeds’ positions. Due to the limited need for human interaction, the introduced simulation offers a possibility to be included in brachytherapy treatment planning. However, large computation times hinder real-time applications. The sensitivity analysis using automatic differentiation can easily be integrated into existing treatment planning systems and has the following advantages: During planning the displacement tolerances serve as a measure of plan robustness and reduce the time for manual planning by indicating sensitive seeds. During seed placement the tolerances show acceptable placement deviations and thus reduce possible needle re-insertions.