Sooriyan, Pamela2018-05-102018-05-102017-03https://hdl.handle.net/11299/196528University of Minnesota Ph.D. dissertation. March 2017. Major: Biophysical Sciences and Medical Physics. Advisor: John Broadhurst. 1 computer file (PDF); vii, 85 pages.External beam radiation therapy mainly uses Bremsstrahlung photons produced when highly accelerated electrons are incident on a target of high atomic number, gamma rays produced by radionuclides, and electrons beams. In the mega-voltage range of photon beams, the dose absorbed by the tumor is primarily by the incident photons losing their energy to the tissues of the tumor by Compton scattering and pair production. Enhancing photonuclear disintegrations offers the possibility of increasing the dose to the tumor (for the same delivered dose) by introducing secondary charged particles in the irradiated region. The dose delivered by secondary charged particles from the 16O(γ,n)15O reaction in bone was measured in an attempt to explore the feasibility of local dose enhancement due to photo nuclear disintegrations. For an externally delivered dose of 13 Gray, the additional dose due to positrons was measured to be 0.26 + 0.0013 mGy in bone and 0.04 + 0.0005 mGy in tissue, using a photon beam that had about 1.3% of photons of energy needed to initiate the 16O(γ,n)15O reaction.enThesis or Dissertation