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Pressurized Xenon-Filled Multiwire Proportional Chamber for Radionuclide Imaging

A pressurized multiwire proportional chamber radionuclide imaging system has been constructed which has operated at pressures of up to 11 atmospheres absolute using a xenon-methane gas mix. The experimental detector has an active imaging area of 25 sq. cm. and an effective depth of 11 cm. An all digital readout system has been constructed with an intrinsic resolution of 1.3 mm FWHM. The FWHM has been measured for various radionuclides: iodine-125 (28 keV), 1.3 mm; thallium - 201 (75 keV), 2 mm; technetium-99 m (140 keV), 3 mm. Our primary goal has been the investigation of properties of such detectors that offer advantages over conventional gamma cameras, including high data rate and improved spatial resolution, particularly for isotopes with photon energies below 100 keV. We have fabricated a gas purification system which permits long term operation of the system without degradation and have investigated construction techniques to produce reliable devices which could be used in a hospital environment.