3D Radiation Dosimetry Using a Radio-Fluorogenic gel

Abstract

A radio-fluorogenic (RFG) gel is a polymer gel that can be applied as a 3D radiation dosimeter in radiotherapy. The gel becomes fluorescent in UV light after exposure to high-energy radiation and the intensity of the fluorescence is proportional to the local radiation dose. This radiation-induced fluorescence is permanent, which distinguishes it from transitory optical emission or scintillation effects. In the thesis we demonstrate that a quasi-rigid RFG gel, consisting of tertiary-butyl acrylate (TBA) with ca 100 ppm maleimido-pyrene (MPy), has the potential to produce spatially resolved images of dose deposition. The work focuses on the fundamental radiation chemistry and photophysics of the medium. In particular, we have investigated the dose and dose-rate dependences of polymer formation and fluorescence intensity using cobalt-60 gamma-ray sources. We have also used collimated beams of 200 kVp X-rays to produce complex radiation fields for test purposes and constructed a tomographic method for reconstructing full 3D images of the dose distribution with submillimetre spatial resolution. Our ultimate goal is to provide a method of quantitative, spatially-resolved dosimetry that can be applied to particle beams and other forms of high-energy radiation that produce the complex radiation fields applied in modern radiotherapy treatment of cancer.