This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We wish to test the hypothesis that monochromatic x-ray radiation at and above the K-edge of various heavy metals bonded to substrates within neoplastic cells is more effective that conventional radiation therapy for killing neoplastic cells in vitro. This program is part of the Compton Light Source (CLS)project at the SLAC Klystron Department to develop a tunable, compact source of quasi-monoenergetic x-rays for use in cancer detection and treatment. While the CLS is under development, we propose to use a beamline at the Stanford Synchrotron Radiation Laboratory (SSRL) for studying dose enhancement in x-ray phototherapy. The proposed work will use an SSRL beamline to irradiate established cell lines labeled with high-Z atoms. Dose enhancement will be assessed through dose-response curves generated both by traditional colony counting and by bioluminescence assay. Candidates for radiosensitizing agents include Iodine, Gadolinium, Indium, Platinum, and Gold. Saples will be irradiated at energies 0-30 keV above the K-edges of these elements. Although SSRL beamlines produce relatively low fluxes at these energies, cell culture geometry can be adjusted to the small beam size, and samples may be irradiated for long times (hours) to reach higher integrated photon intensities. Broader bandwidths (up to 1 keV) are permitted in these experiments as a trade-off for reaching higher fluxes.
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