PhD Thesis Proposal: Savannah Decker

For Zoom information contact savannah.m.decker.th@dartmouth.edu

"Development of Inclusive Cherenkov Surface Dosimetry and Novel Incident Detection in Radiotherapy for All Patient Demographics"

Abstract

In the U.S. alone, nearly 2 million people will be diagnosed with cancer this year, 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.

The first aim of this thesis focuses on the use of Cherenkov imaging for the detection and quantification of radiation therapy treatment incidents. A clinic-wide, always-on Cherenkov imaging system was deployed, and incidents were uniquely detected that would have otherwise gone unnoticed without this system. This inspired further work, focusing on quantifying both inter- and intra-fractional incidents with several image comparison metrics, serving as a foundational step towards automatic incident detection. Lastly, for estimating the extent of unplanned delivery incidents, remote scintillation in vivo dosimetry via a Cherenkov imaging system was deployed for the rapid estimation of breast dose in whole breast radiotherapy.

The second aim of this thesis focuses on extending the use of Cherenkov imaging to diverse patient populations. Previous work, primarily conducted at Dartmouth Hitchcock Health, has suffered from an extreme lack of diversity, with nearly all patient data sampled from a Caucasian population. As melanin is a known optical absorber of Cherenkov emission wavelengths, darker patients with more melanin will yield a different Cherenkov output than lighter, Caucasian patients for the same delivered dose. In this work, we have developed the first multi-institutional partnership dedicated to collecting diverse patient data. Our work aims to quantify the effect of skin tone on Cherenkov emission towards an absolute calibration, such that 2D surface dose maps may be generated independent of skin tone for a truly inclusive optical dosimetry tool.

Thesis Committee

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

Contact

For more information, contact Theresa Fuller at theresa.d.fuller@dartmouth.edu.