Implementation of an analytically based scatter correction in SPECT reconstructions

Photon scattering is one of the main effects contributing to the degradation of image quality and to quantitative inaccuracy in nuclear imaging. We have developed a scatter correction based on the analytic photon distribution (APD) method, and implemented it in an iterative image reconstruction algorithm. The performance of the method was evaluated using computer simulated projection data, experimental data obtained from physical phantoms, and patient data. The scatter corrected images were compared to images that were only corrected for attenuation and collimator blurring. In the simulation studies our results could also be compared to an ideal scatter correction in which images were reconstructed only from unscattered photon data. In all cases, our scatter corrected images demonstrate improved image contrast. In the simulated data the contrast for images only corrected for attenuation and collimator blurring were on average 29% poorer than the ideal correction. Images for which our scatter correction was applied had contrast that was on average within 3% of the ideal correction. The scatter corrected reconstruction requires between 4 to 5 hours of total CPU time, on a 1.7 GHz processor with 1Gb RDRAM, using clinical data.