PhD Thesis Defense: Savannah Decker

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"Development of Novel Radiotherapy Treatment Monitoring and Quantitative Cherenkov Surface Dosimetry for Diverse Populations"

Abstract

In the US alone, nearly two million people will be diagnosed with cancer annually, and over half of them will receive radiation therapy throughout the course of their care. While widely regarded as safe, radiation therapy presents unique challenges that other procedures, such as surgery, lack. Namely, the invisible nature of the radiation itself makes it impossible to directly visualize treatment. Many immobilization and localization techniques exist to minimize the chance of incorrect radiation dose delivery, yet incidents still occur. Within the last decade, Cherenkov imaging has emerged as a new radiation therapy delivery verification technique. Cherenkov imaging is unique to other modalities because it allows for real-time visualization of beam delivery on the entire surface of the patient, showing light wherever dose is delivered. Beyond the ability to verify the extent of the treatment field, it has the potential to provide a 2D surrogate surface dose map. In this work, we exploit the unique nature of Cherenkov imaging for treatment delivery verification and incident detection in the radiation therapy clinic.

This thesis focuses on several uses of Cherenkov imaging in the clinic, spanning from radiotherapy incident detection to quantitative in vivo dosimetry for diverse patient populations, independent of skin pigmentation. Cherenkov imaging is first explored as a tool for automatic incident detection during treatment, leveraging unique biological fiducials that are inherent to patient images. Expanding to quantitative in vivo dosimetry, the synergistic combination of Cherenkov imaging and scintillation dosimetry is presented as promising alternative to conventional dosimeters, with the unique ability to directly visualize measurement locations relative to the treatment field on the surface of the patient. Lastly, the longstanding concern regarding Cherenkov imaging for dark skin patients is addressed in a multi-institutional collaboration between Dartmouth Hitchcock Health and Moffitt Cancer Center, dedicated to imaging a diverse population, with the successful development of a patient-specific skin pigmentation calibration, a noteworthy advancement towards the realization of quantitative Cherenkov dosimetry.

Thesis Committee

• David Gladstone (chair)
• Brian Pogue
• Lesley Jarvis
• Petr Bruza
• Rongxiao Zhang
• Todd Pawlicki (external, UCSD)

Contact

For more information, contact Thayer Registrar at thayer.registrar@dartmouth.edu.