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Advanced concepts in prompt gamma-ray imaging for ion-cancer verification

  • Author(s): Ellin, Justin
  • Advisor(s): Vetter, Kai
  • et al.
Abstract

The major paradigm in the treatment of cancer has been to develop and improve methods for more focused targeting of cancerous cells while reducing the toxicity to healthy tissue. In radiation oncology, that effort has been focused recently on the use of proton beams. The dose kinematics of protons – namely the Bragg curve – allows for better conformity to tumors. However, as protons do not escape the patient, additional safety margins are added to treatment plans which undermine the theoretical therapeutic benefits of protons unless reliable in vivo range verification tools are found.This dissertation describes advanced techniques and concepts as applied to a multi-knife edge slit collimator 2D imaging system. First, the physics of proton therapy is reviewed and a survey is given of current ongoing system designs for proton range verification. Next, an overview is given of the system as well as new improvements to the hardware and software of the data acquisition system. New measurements were then conducted using a 67.5 MeV proton beam at an order of magnitude higher beam current than has been done previously. Details of additional gain and crystal segmentation adaptation algorithms developed to correct for beam-induced effects on the photomultipliers are then described. The incorporation of a separate detector to provide timing information about the arrival of the beam is then discussed: both the potential benefits as well as limitations found in its use here that will inform future iterations of the design. Lastly, a physics kernel is introduced based on published angular excitation functions to further enhance image quality. The system was found to be able to determine the range of the proton beam to within 1 mm (2σ) with the delivery of 10^10 protons across a 6 cm FOV. Future investigations utilizing the techniques proposed here should only enhance this sensitivity and contribute to efforts to better patient outcomes.

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