Final PhD Oral Examination (Thesis Title: “Development of Trajectory-Based Techniques for the Stereotactic Volumetric Modulated Arc Therapy of Cranial Lesions”)

Abstract:
Introduction: Stereotactic Radiosurgery is the delivery of a large, highly focused radiation dose to well defined targets in the brain. This thesis explores linac-based inverse planning algorithms that can be implemented to improve the dosimetric and delivery performance of Volumetric ModulatedArc Therapy treatments for these indications.

Methods: In this work, algorithms for Couch-Gantry, and Collimator-Gantry trajectory optimization were developed. Treatment plans calculated with
these algorithms were compared dosimetrically to conventional methods used for treatment planning. Additionally, the clinical feasibility of the
methods developed were tested by performing end-to-end patient specific Quality Assurance on prospective treatments and by developing machine specific quality assurance for the intra-treatment movement of the couch and collimator.

Results: This thesis introduces a robust method for optimizing the trajectory of the couch by delivering treatments along patient generalized trajectories. These treatments were able to dosimetrically outperform Dynamic Conformal Arcs, and had higher delivery efficiency than multi-arc
volumetric modulated arc therapy. Similarly, collimator trajectory optimization was shown to reduce the dose bath when compared with the clinical standard of care. These methods were shown to be safe for delivery using phantom verification studies.

Conclusion: This thesis outlines methods for stereotactic radiosurgery which show dosimetric improvement over previous methodology and are
clinically feasible.