Development of scatter correction techniques for quantitative 3D imaging in a whole body PET scanner with the septa retracted

In order to give quantitation to the 3D data acquisition technique in a whole body PET scanner (CTI/Siemens 951R) with the septa retracted, we have investigated two separate methods for the reduction of the scattered photons in the final images. The first method is a dual energy window scatter correction technique which involves the collection of two separate sets of 3D sinograms at the same time but at two different energy windows. The upper energy window data are corrected by a weighted subtraction of smoothed lower energy window data. The weighting parameters are derived from phantom studies. The second method is an unsharp mask scatter correction technique which has the advantage over the first method by using only a single set of 3D sinograms. The 3D reconstructed images are digitally post processed using a low pass filter and these images are weighted and subtracted from the original 3D images to remove the scattered photons. Both of these techniques are being evaluated in phantom and F-18 FDG human brain studies in which 2D and 3D images of the same subject have been compared. The initial results show good quantitation of the images obtained through the use of these two methods.