Object shape dependent PSF model for SPECT imaging

Abstract

An analytical expression for the point spread function (PSF) and the line spread function (LSF) of a parallel hole gamma camera is presented, for homogeneous media and for photons having mainly Compton interactions in the object. The PSF of scattered photons is described by convolving a zeroth-order modified Bessel function of the second kind with the unscattered PSF, which is approximated by a Gaussian. The complete PSF (scatter plus nonscatter) depends on the source distance (z) and depth (d) of the source in the object. For convex-shaped emitting objects, the dependence of the PSF on the object contour can be incorporated by a simple correction. Thus, a complete mathematical model of the imaging of an activity distribution in a homogeneous medium is obtained. The model has been evaluated for /sup 99m/Technetium line sources by using a LEAP collimator at various energy windows ( Delta E). It is shown that the model is valid to a high accuracy at Delta E=15%, for a large range of values of z and d.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>