A positron tomograph with 600 BGO crystals and 2.6 mm resolution

Abstract

A description is given of the imaging performance of the Donner 600-Crystal Positron Tomograph, a single 60-cm-diameter ring of 3-mm-wide bismuth germanate (BGO) crystals coupled individually to 14-mm phototubes. With a pulse height threshold of 200-keV and a slice thickness of 5 mm, the sensitivity is 7024 events/s per mu Ci/Ml in a 20-cm cylinder of water. The measured rates for 18 mu Ci/ml are 95000 trues/s plus 20000 randoms/s. A 0.3-mm-diameter /sup 22/Na line source near the center of the tomograph has a circular point-spread function (PSF) with a full-width at half-maximum (FWHM) of 2.6 mm. At 5 cm from the center the PSF is elliptical with a FWHM of 2.7 mm tangential*3.2 mm radial. At 10 cm the PSF has a FWHM of 2.8 mm tangential*4.8 mm radial. Attenuation data have been accumulated with a 20 mCi /sup 68/Ge orbiting transmission source, and 100 million coincident events have been collected in 200 s.