The influence of attenuation-map quality on the absolute quantitative accuracy of SPECT images

We have investigated the influence of higher resolution CT attenuation maps, relative to those from conventional transmission scans, on attenuation (AC) and scatter corrections (SC) in SPECT reconstructions. Using both types of attenuation maps and phantom emission data, we evaluated the scatter distributions, image quality, and the absolute quantitative accuracy of SPECT images. Small but systematic differences in the total number of counts attributed to scatter were observed using different combinations of SC and attenuation maps. Our results also indicate that SC can be significantly influenced by errors in image co-registration. Improved image quality and more precise measurements of reconstructed activity concentration are possible using CT attenuation data. However, the use of segmented attenuation maps from SPECT transmission scans provides sufficient quantitative accuracy for most applications