Implementation of an analytically based scatter correction in SPECT reconstructions

Photon scattering is one of the main effects contributing to the degradation of image quality and to quantitative inaccuracy in nuclear imaging. We have developed a scatter correction based on a simplified version of the analytic photon distribution (APD) method, and have implemented it in an iterative image reconstruction algorithm. The scatter distributions generated using this approach were compared to those obtained using the original APD method. Reconstructions were performed using computer simulations, phantom experiments, and patient data. Images corrected for scatter, attenuation, and collimator blurring were compared to images corrected only for attenuation and collimator blurring. In the simulation studies, results were compared to an ideal situation in which only the primary (unscattered) photon data were reconstructed. Results showed that in all cases, the scatter-corrected images demonstrated substantially improved image contrast relative to no scatter correction. For simulated data, scatter-corrected images had very similar contrast and noise properties to the primary-only reconstructions. Additional work is required to further reduce the computation times to clinically viable amounts.

I. Introduction

In order to improve image quality and the quantitative accuracy of single photon emission computed tomography (SPECT) reconstructions, it is necessary to use a reconstruction algorithm that includes accurate and patient specific corrections for photon attenuation, collimator blurring and photon scatter. Although corrections for attenuation and collimator blurring are becoming clinically viable, scatter corrections are still not commonly used because the methods are too inaccurate for quantitative imaging or require prohibitively long computation times.