Resolution recovery on list mode MLEM reconstruction for Dynamic Cardiac SPECT system

TL;DR

This paper demonstrates that incorporating spatially variant point spread function (SV-PSF) deconvolution into list mode MLEM reconstruction significantly enhances resolution and image quality in the DC-SPECT system, surpassing conventional methods.

Contribution

It introduces a PSF deconvolution method with list mode MLEM for DC-SPECT, improving resolution recovery and image quality over existing approaches.

Findings

Achieved 4.5 mm spatial resolution at the center.

Significant image quality improvement with PSF modeling.

Outperformed GE Discovery 570c system in resolution and counts.

Abstract

The Dynamic Cardiac SPECT (DC-SPECT) system is being developed at the Massachusetts General Hospital, featuring a static cardio focus asymmetrical geometry enabling simultaneous high resolution and high sensitivity imaging. Among 14 design iterations of the DC-SPECT with varying number of detector heads, system sensitivity and system resolution, the current version being fabricated features 10 mm FWHM geometrical resolution (without resolution recovery) and 0.07% sensitivity; this is 1.5x resolution gain and 7x sensitivity gain compared to a conventional dual head gamma camera. This work presents improvement in imaging resolution by implementing a spatially variant point spread function (SV-PSF) with list mode MLEM reconstruction. A resolution recovery method by PSF deconvolution is validated on list mode MLEM reconstruction for DC-SPECT. A spatial invariant PSF is included as an additional test to show the influence of the accuracy of PSF modelling on the reconstructed image quality. We compare the MLEM reconstruction with and without PSF deconvolution; an analytic model is used for the calculation of system response, and the results are compared to Monte Carlo (MC) based methods. Results show that with PSF modelling applied, the quality of the reconstructed image is improved, and the DC-SPECT system can achieve a 4.5 mm central spatial resolution with average 795 counts/(s*Mbq). The results show substantial improvement over the gold standard GE Discovery 570c performance (spatial resolution 7 mm with an average 460 counts/s*MBq, central resolution 5.8 mm). The impact of PSF deconvolution is significant, and the improvements of the reconstructed image quality is more evident compared to MC simulated system matrix with the same sampling size as in simulation.