Estimation of primary plus small angle scatter in scintigrams using two photopeak energy windows and a linear model

In scintigraphic imaging, scattered photons decrease image contrast and can lead to quantitative errors in single photon emission computed tomographic (SPECT) reconstructions. The point spread function for scattered photons can be characterized as having a narrow and a wide component. A method for estimating the wide scatter component has been developed. Subtracting this estimate from the original image yields an estimate of the primary plus the narrow scatter component. The method is based on the difference between the energy spectrum for the wide scatter component and that for primary plus the narrow scatter component. The assumptions of this method are tested using measurements of line sources at four depths. It is then applied to images of the Rollo contrast-detail phantom taken at a number of depths. Increased contrast and quantitative accuracy are obtained with no significant change in a lesion detectability index (with ratio of mean contrast to standard deviation in contrast for repeat acquisitions)