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Meeting ID: 914 1267 9740
Passcode: 922333

Abstract: Radiation therapy (RT) is a widely adopted cancer treatment technique, contributing to over 50% of all cancer treatments worldwide while improving quality of life for many others. While effective treatment depends on rigorous quality assurance and plan verification, patient setup variations and anatomical changes during treatment can cause deviations from prescribed doses, potentially compromising treatment efficacy or patient safety. Current dose verification methods rely primarily on point measurements using in vivo dosimeters, which provide limited spatial coverage and lack temporal information which pose critical limitations for large treatment fields and dose gradients.

These constraints become particularly important with emerging ultra-high dose rate radiation delivery, which demonstrates tissue-sparing benefits through the FLASH effect. However, this technique requires precise spatiotemporal dose characterization that existing monitoring systems cannot adequately provide. The need for comprehensive, full-field treatment monitoring and dynamic surface dosimetry therefore spans both conventional and advanced radiotherapy applications.

This thesis addresses these challenges through two complementary approaches. The first involves developing a deformable scintillator array for high-speed, wide-area surface dosimetry across various radiotherapy modalities. Using FLASH pencil beam scanning proton therapy as the primary application due to its demanding spatial, temporal, and dosimetric requirements, a prototype system was constructed and evaluated with anthropomorphic phantoms. Time-resolved surface measurements enabled the development of novel delivery verification metrics and a depth projection algorithm for estimating volumetric dose from surface dynamics. The technology was subsequently adapted for conventional photon therapy, focusing on contralateral breast dosimetry in whole-breast radiotherapy.

The second approach expands treatment monitoring capabilities by investigating spectral characteristics of optical emission during external beam radiotherapy. High-energy particles traveling through tissue produce Cherenkov surface emission and, under ultra-high dose rate conditions, additional forms of tissue luminescence. While previous work demonstrated correlations between local Cherenkov generation and dose deposition, tissue constituents like blood and oxygenation create spectral attenuation that disrupts this relationship upon signal collection. This work employs spectral signal separation techniques across proton, electron, and photon modalities to overcome these limitations, aiming to monitor physiological changes for early toxicity detection and improve correlation between surface emission and deposited dose through tissue attenuation correction.

Thesis Committee: Petr Bruza, PhD (chair), David Gladstone, Lesley Jarvis, Brian Pogue,  Michele Kim (U Penn)