A Spline Approach to Parallel-Hole Collimator Deblurring for aSRT-Reconstructed SPECT Images

In the present work, we present a spline-based method for deblurring aSRT-reconstructed images of single photon emission computed tomography (SPECT) systems equipped with parallel-hole collimators. aSRT, or the attenuated spline reconstruction technique, is a recently developed analytic algorithm capable of reconstructing attenuation-corrected SPECT images. Our approach is based on the characterization of the collimator in terms of its blurring profile, rather than the use of the point response function. By deblurring the initial attenuated sinogram, we are able to reconstruct using aSRT images with less blurring. Simulation studies were performed by using an image quality (IQ) phantom and an appropriate attenuation map. Reconstructed images were generated for 180 views over 360 degrees and twenty realizations of Poisson noise were created at a noise level of 50% of the total counts. For the purposes of the IQ phantom simulations, we employed a typical low energy high resolution (LEHR) collimator and blurred the relevant data using a Gaussian blur profile was with a corresponding standard deviation, σ, value of 0.019. Comparisons between blurred and deblurred sinogram reconstructions were performed using two appropriate metrics, namely hot contrast (local metric) and no-reference blur metric (global metric). The preliminary results indicate that the algorithm presented in this work is capable of compensating for the collimator blur effect, especially in aSRT-reconstructed SPECT images. The metrics employed indicate that our method can be proven to be useful in clinical SPECT imaging as well as in biomedical image processing and analysis in general. Therefore, the proposed blurring-compensating technique for parallel-hole collimation could provide efficient deblurring in SPECT imaging and may be helpful in improving image quality of SPECT reconstructions.