Scatter correction for camera based coincidence and single photon imaging protocols

The authors have investigated and tested a strategy for acquiring projection data from a mixed field of a positron emitter, a single photon source, and a transmission source, and independently reconstructing each of the three data sets. Tc-99m is imaged through the collimator using conventional SPECT techniques. The annihilation and the transmission radiations are detected as they penetrate (uncollimated) through the collimator septa. The success of independently reconstructing each data set rests on the effectiveness of the scatter subtraction method. A few scatter compensation methods were tested. A scatter compensation algorithm (based on 3 energy windows) within an iterative reconstruction algorithm was applied and quantitative improvements of the emission reconstructions are reported. The authors' experimental results of immediately sequential Tc-99m, FDG, and I-131 transmission data, demonstrate that each isotope can be imaged in the presence of the others. This method could be extended to truly simultaneous acquisitions.