PhD Thesis Defense: Austin Sloop

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Meeting ID: 964 9282 1071
Passcode: 444735

"Developing Real-Time, Online Beam-Control of UHDR Irradiators to Facilitate FLASH Translational Investigations"

Abstract

The field of radiation oncology seeks novel techniques to increase the therapeutic ratio to treat malignancies while minimizing damage and toxicities in healthy tissues. While it was observed that delivering therapeutic doses at high dose rate could elicit lower biological effects over a half-century ago, the field of ultra-high dose rate (UHDR) radiation therapy (colloquially known as FLASH RT) has seen a resurgence in recent years due to an alignment of accelerator capability, dosimetric advances, and improved biotechnological techniques. This has opened the door to studying potential underlying mechanisms such that we may leverage the effects of FLASH tissue sparing in the near future. Collaboration of Dartmouth College with the Dartmouth Cancer Center established a leading FLASH development platform with two linacs currently being used for preclinical studies while preparing for an early clinical study. 

Patient safety is a core tenet; however, FLASH RT has the potential to cause immense harm if radiation is improperly applied. Modern linear accelerators can produce UHDR fluences but safely delivering a precise amount of dose and verifying what was delivered are two of the biggest challenges to FLASH RT. Under UHDR operation, desired doses can be achieved in a small number of pulses delivered over several milliseconds so a single unwanted pulse can result in a significant deviation from the therapy plan. This work developed critical dosimetry and control systems of electron clinical irradiators to produce clinically usable, safe UHDR beams. Specifically:

• Linac modification and beam controller (clinical Varian C-arm linac and an IntraOp Mobetron intraoperative unit)
• Dosimeters viable under UHDR conditions (including diamond, semiconductor, and current transfer dosimeters)
• New calibration methods, QA procedures, and experimental workflows
• Real-time dose monitoring and output control of a novel irradiator, towards meeting state regulatory requirements for human FLASH trials at Dartmouth.

Thesis Committee

• Petr Bruza (Chair)
• David Gladstone
• Lesley Jarvis, MD
• Kyle Gallagher (University of Nebraska Medical Center)

Contact

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