[Investigation of the Optimal Parameters for Block Sequential Regularized Expectation Maximization (BSREM) Reconstruction in Bone SPECT Using a Ring-type Semiconductor SPECT/CT].

Purpose: This research aims to optimize the block sequential regularized expectation maximization (BSREM) reconstruction in bone single photon emission computed tomography (SPECT) images using a ring-type SPECT/computed tomography (CT) system in terms of image quality and accuracy of quantitative evaluation.

Methods: SPECT images were acquired using a ring-type SPECT/CT and from a SIM² bone phantom containing a 99m-Tc solution. BSREM parameters were assessed with coefficient of variation (CV), recovery coefficient (RC), contrast noise ratio (CNR), standardized uptake value max (SUVmax), and its root mean square error (RMSE_SUVmax). Clinical images were reconstructed, and the reconstructions were evaluated as superior based on phantom results.

Results: Increasing γ led to higher RC and CV, while increasing β lowered these values. CNR showed no consistent trend. In terms of quantitative evaluation, γ value 5.0, β values 0.3-0.9, and γ value 10, βvalues 0.3-0.9 resulted in lower RMSE_SUVmax compared to Anger type. Based on the phantom experiment, γ value 5.0, β values 0.5-0.9, and γ value 10, β values 0.7-0.9 were evaluated as superior. Clinical images under these reconstructions, determined from the phantom experiments, with γ value 5.0, β value 0.9, showed the smoothest of normal bone and the clearest separation of neighboring tumors.

Conclusion: As reconstruction parameters for BSREM reconstruction in bone SPECT on a ring-type semiconductor SPECT/CT system, a γ value of 5.0 and a β value of 0.9 were considered suitable for image quality and quantitative evaluation.