STORAGE PHOSPHOR FILM FOR RADIATION THERAPY DOSIMETRY

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Modern radiation therapy modalities, for example, intensity modulated radiation therapy (IMRT), are associated with highly conformal dose distributions with steep gradients. Commissioning of these modalities requires the use of multidimensional dosimeters which have been under intense research and development. A recent report from the Radiological Physics Center (RPC) revealed that roughly 30% of institutions failed to deliver a dose distribution to a head-and-neck phantom that agrees with their own treatment plan to within 7% or 4 mm. The RPC report provides strong evidence that IMRT implementation is prone to error and that improved quality assurance tools are required. The overarching hypothesis of this research is that a low-Z KCl:Eu2+ storage phosphor film (SPF) will provide the first 2D dosimeter capable of conducting benchmark dosimetry measurements, substantially improving the commissioning and quality assurance of radiation therapy treatment planning and delivery systems. Our first aim is to optimize KCl:Eu2+ storage phosphor particle composition and chemical structure to maximize radiation sensitivity, radiation hardness, response uniformity, and signal stability. Our second aim is to develop a process to fabricate an SPF by evaporating the optimized storage phosphor developed in aim 1 to a thickness on the order of one micron using physical vapor deposition onto a nearly water-equivalent substrate. Our third aim is to demonstrate that the SPF dosimeter developed in aim 2 will provide benchmark-quality dose distribution measurements and to demonstrate the flexibility of the SPF fabrication process by building planar and cylindrical dosimeters.