An investigation of scatter in attenuation correction for PET

It is noted that the acceptance of scattered photons in the PET (positron emission tomograph) transmission scan can be minimized by setting discriminator thresholds to reject scattered events, improving the shielding geometry of the detectors with narrow planes and long septa or using line transmission sources and sinogram windowing. Postacquisition corrections for transmission scatter include subtraction of characteristic scatter distributions and deconvolution techniques. It is shown that the problem of scatter in the transmission scan can be avoided entirely if ellipse-calculated or hybrid measured/calculated attenuation correction is used. Hybrid attenuation correction is similar to calculated attenuation but uses regions of interest defined on the transmission image instead of an ellipse to delineate the attenuation borders. Projections are taken through the attenuation map to produce an attenuation-correction sinogram