High resolution dosimetric detector for synchrotron microbeam cancer therapy

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The recent availability of the Biomedical Imaging and Therapy (BMIT) beam line at the Canadian Light Source (CLS) in Saskatoon is a truly exceptional and a unique opportunity to carry out research that has impact in the overall target area of biomedical technologies. During this strategic grant we propose to develop a high resolution dosimetric detector for use in monitoring the high dose profile in Microbeam Radiation Therapy (MRT). Microbeam Radiation Therapy is based on the irradiation of tumors with microplanar arrays of intense synchrotron-generated x-rays. Irradiation with parallel arrays of thin, planar slices of x-ray beams spares the normal tissue, including the central nervous system, and preferentially damages tumors. MRT has been shown to be of great benefit in cancer therapy, and relies on the availability of a synchrotron source - hence the exceptional and unique opportunity in Canada. One of the biggest problems in applying MRT is the measurement of the high dose profile in the synchrotron generated beam, since the dose is large and varies over distances of micrometers. Thus, a high spatial resolution, high dynamic range dosimetric detector is needed to be able to perform MRT. We propose a novel high resolution dosimetric detector plate which is based on the conversion of rare-earth (RE) ions in a glass or glass-ceramic plate to another oxidation state by the incident high dose radiation. The converted amount depends on the dose and is highly localized to the incident radiation region. The fluorescence emission from the new oxidation state (after suitable excitation) of the RE ion can be easily distinguished from that from unconverted ions. Fluoroscopic confocal imaging, with filters to remove the emission from unconverted RE ions, will be used to obtain the dose distribution. Further, the research will aim to develop reusable dosimetric plates, and will optimize the RE-doped plate medium, response and the read-out optics for high resolution measurements. The strategic project has direct enormous health benefits to Canada, uses the Canadian synchrotron, and trains HQP in interdisciplinary experimental skills.