Grant: Operating Grant

The major advance in modern radiation therapy has been the development of techniques to better shape radiation dose to tumor volumes, while minimizing the dose to surrounding normal tissue. The verification of such delivery with traditional measurement methods is difficult, since the doses need to be determined in three dimensions (3D). A promising technique for volumetric 3D dose measurement is gel dosimetry, based on the imaging of certain gel systems which change under irradiation. Despite its promise, gel dosimetry has not come into widespread clinical use, mainly because of difficulties in reproducibility during gel preparation and readout, toxicity of gel components in certain gels, and limited access to imaging modalities (e.g., magnetic resonance imaging) for dose readout. In the last few years we have used CIHR funding to advance clinical gel dosimetry by: 1) developing recipes for new dosimeters using knowledge gained from fundamental physical experiments and mathematical modeling, 2) developing less-toxic polymer-based dosimeters, and 3) characterizing and optimizing optical computed tomography (optical CT) imaging to achieve accurate and reproducible 3D gel dosimetry. In this application we propose to 1) continue to invent, characterize, and test formulations for gel dosimeters, 2) develop standard protocols by which specific gels can be used with specific readout schemes, 3) evaluate the dose measurement integrity of gel dosimetry by comparing to standard techniques, and 4) develop standard software to evaluate and compare gel-measured doses to the planned dose delivery and to dose measurements using conventional tools available in the clinic. Objectives 1) and 2) provide the basic information required to develop the rigorous protocols for gel dosimetry (including preparation, handling and readout) required for good dosimetry, while objectives 3) and 4) are necessary steps towards translating the dosimetry to clinical use.