A PROTOTYPE ROTATING SLAT COLLIMATOR FOR SINGLE-PHOTON EMISSION COMPUTED-TOMOGRAPHY

A collimator consisting of a series of highly attenuating parallel sla ts has been constructed and used in conjunction with a gamma-camera to approximately measure planar projections of a given radionuclide dist ribution. The enlarged solid angle of acceptance afforded by the slat collimator gave rise to an increased geometric efficiency of between 1 2 and 28 times that observed with a low-energy high-resolution (LEHR) parallel-hole collimator. When the slats rotated over the face of the detector and the camera gantry turned about the object, sufficient pro jections were acquired to reconstruct a three-dimensional (3-D) image using the inversion of the 3-D radon transform, The noise behavior of an algorithm for implementing this inversion was studied analytically and the resulting relationship has been verified by computer simulatio n, The substantially improved geometric efficiency of the slat collima tor translated to improvements in reconstructed signal-to-noise ratio (SNR) by, at best, up to a factor of 2.0 with respect to standard para llel-hole collimation. The spatial resolution achieved with the slat c ollimator was comparable to that obtained with a LEHR collimator and n o significant differences were observed in terms of scatter response, Accurate image quantification was hindered by the spatially-variant re sponse of the slat collimator.