Quantitative /sup 131/I SPECT with triple energy window Compton scatter correction

In this work accuracy of quantitative /sup 131/I SPECT with triple energy window (TEW) scatter correction is evaluated by phantom measurements. The TEW method is a pixel by pixel correction where the scatter fraction in the photopeak window is estimated by linear interpolation between two adjacent narrow sub-windows. Quantification procedure includes marker based X-ray CT-SPECT image fusion to determine object boundaries and to generate attenuation maps. TEW scatter correction significantly reduces the effect of background activity on reconstructed counts within an object, but it still exists due to the finite position resolution of the system. Therefore, a background dependent calibration factor was used for quantification. Quantitative accuracy with TEW correction was 5% and 14% for a tumor and lung respectively of a physical phantom with non-uniform activity and non-uniform scattering medium.