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

The authors report on the first clinical evaluation of the ¹³⁷Cs single photon transmission measurement that has been implemented on the Siemens/CTI ECAT ART. Thorax phantom studies are performed to verify the accuracy of the transmission measurement. Pre-injection (with patient repositioning) and post-injection transmission scans and attenuation corrected emission images of 25 patients are compared with respect to estimated linear attenuation coefficients and specific activities in organs, and standardized uptake values in lesions. The authors find that both pre- and post-injection transmission provide accurate 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 17-18% greater pixel standard deviation. Estimates of standardized uptake in smaller lesion ROIs are 13% higher with post-injection correction, but there is little difference in the ROI pixel variances