List-mode maximum likelihood reconstruction of Compton scatter camera images in nuclear medicine

Abstract

A Maximum Likelihood (ML) image reconstruction technique using list-mode data has been applied to Compton scattering camera imaging. List-mode methods are appealing in Compton camera image reconstruction because the total number of data elements in the list (the number of detected photons) is significantly smaller than the number of possible combinations of position and energy measurements, leading to a much smaller problem than that faced by traditional iterative reconstruction techniques. For a realistic size device, the number of possible detector bins can be as large as 10 billion per pixel of the image space, while the number of counted photons would typically be a very small fraction of that. The primary difficulty in applying the list-mode technique is in determining the parameters which describe the response of the imaging system. In this work, a simple method for determining the required system matrix coefficients is employed, in which a back-projection is performed in list-mode, and response coefficients determined for only tallied pixels. Projection data has been generated for a representative Compton camera system by Monte Carlo simulation for disk sources with hot and cold spots and energies of 141, 364, and 511 keV, and reconstructions performed.

Study on listmode OSEM reconstruction including image-space resolution recovery techniques for Compton camera

“…LMOSEM reconstruction algorithm which is performed by iterating forward and backward projection in given subset provides two major advantages, acceleration on computation and including elaborate system matrix [8][9][10][11]. The 3D Gaussian resolution model mentioned in previous section is incorporated into LMOSEM using image-space convolution operation which is suggested in Ref.…”

Spatial resolution of the Multiple Coincidences Compton Camera

“…In this study we use a standard three dimensional Maximum Likelihood Expectation Maximization algorithm of Shepp and Vardi that operates on list-mode data similar to as was done in [8]. We use ray-driven forward-and backprojection operators with 500 rays passing through each conical surface in order to provide sufficient sampling.…”

Resolution recovery for Compton camera using origin ensemble algorithm

“…Several analytic and iterative algorithms have been proposed for the CC reconstruction. [3][4][5][6] However, to this date, little progress has been achieved in implementing any of the corrections that would be required for a successful high-resolution image reconstruction. 7,8 It was recently demonstrated 9 that in the standard modeling of image resolution for CC using the shiftvariant point spread functions (PSFs), the recalculation of the PSF model required computing times of the order of months.…”