Abstract
<p> Cancer is the second leading cause of death in the United States. The probability of a person developing cancer during one’s lifetime is about 40%. It places a tremendous financial and psychological burden on people. As an external beam radiation therapy modality, proton therapy is an effective modality to fight against cancer and has gained much attention due to its unique dosimetric properties. Protocols have been developed for both passive and pencil beam scanning systems to deliver dose conformal to the tumor so that normal tissue toxicity could be mitigated. <br />
This dissertation proposes a novel inverse optimization procedure to create a patient-specific 3D conformal dose modulator paired with a corresponding fluence map for proton beam therapy. It combines the advantages of both passive and pencil beam scanning systems to deliver a conformal dose to the target using only one energy layer of the pencil beam scanning system. We first investigated the feasibility of using mini-pyramids as the fundamental structure of an energy modulation device. Then, we developed an inverse optimization algorithm to generate a 3D conformal modulator based on the intended dose distribution and basic physics principle. The robustness of the inverse algorithm was validated by Monte Carlo simulation. The physical modulator was 3D printed, and film dosimetry was performed to verify the effectiveness qualitatively. <br />
This dissertation demonstrated a robust algorithm to produce a 3D conformal dose modulator paired with a proton fluence map, inversely calculated using adaptive ring optimization techniques based on dose objectives, dose constraints, and the shape of the target. The employment of such a device can reduce the overall treatment time, thus mitigating some uncertainties while delivering dose to the target with great accuracy.<br />
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