Attenuation effects in gamma-camera coincidence imaging

Images produced by gamma camera coincidence (GCC) techniques have a much lo wer count-density than those produced by dedicated PET scanners. We examine the effects of attenuation and attenuation correction on GCC images using gamma-camera emission data and PET emission and transmission data from phan tom and human studies. The effects studied include contrast, noise, and gen eral image quality. Results show that lung lesion contrast is improved but the signal-to-noise ratio is slightly degraded by the application of attenuation correction. Ad ditionally, the corrected images do not contain the distortions of the unco rrected images and they more accurately show the activity distribution of t he imaged object. The noise studies suggest that statistically appropriate transmission data for implementing an attenuation correction can be acquired in a small fract ion of the time used for an emission scan.