Treatment plan optimization for rotating-shield brachytherapy

In this thesis, we aim to develop fundamentally new techniques and algorithms for efficiently computing rotating-shield brachytherapy (RSBT) treatment plans. We propose that these algorithms will pave the way for making RSBT available in clinical practices. RSBT is an intensity modulated high-dose-rate brachytherapy (HDR-BT) technique. Theoretically, RSBT offers advantages over the conventional HDR-BT. Although this technique is promising in theory, its application in practice is still at an early stage. The RSBT technique entails rotating a radiation-attenuating shield about a brachytherapy source to directionally modulate the radiation in an optimized fashion. The unshielded brachytherapy source used in conventional HDR-BT delivers radially symmetric dose distributions, thus the intensity modulation capability of the conventional HDR-BT is limited. With the capability of making anisotropic radiation, RSBT will revolutionize the brachytherapy technique through superior dose conformity, increased flexibility and inherent accuracy. Due to the enhanced power of intensity-modulation, RSBT will also enable dose escalation without increasing toxicity to the organs-at-risk, thus improving quality of life for millions of cancer patients. Although the first conceptual RSBT method was proposed more than ten years ago, there are still tremendous challenges for applying it in clinical practices. Creating efficient and automated treatment planning system is one of the major