Clinical evaluation of single-photon attenuation correction for 3D whole-body PET

We report on the first clinical evaluation of the Cs-137 Single photon tran smission measurement that has been implemented on the Siemens/CTI ECAT ART. Thorax phantom studies are performed to verify the accuracy of the transmi ssion measurement. Pre-injection (with patient repositioning) and post-inje ction transmission scans and attenuation corrected emission images of 25 pa tients are compared with respect to estimated linear attenuation coefficien ts and specific activities in organs, and standardized uptake values in les ions. We find that both pre and post-injection transmission provide accurat e estimates of attenuation correction factors. Post-injection estimates for mean attenuation coefficients and specific activities in larger regions of interest (ROIs) are nearly the same as pre-injection values, but exhibit 1 7-18% greater pixel standard deviation. Estimates of standardized uptake in smaller lesion ROIs are 13% higher with post-injection correction, but the re is little difference in the ROI pixel variances.