Effect of Span and MRD Configurations on Small Animal PET Image Quality and Quantitative Accuracy.

Background: Employing 2D rebinned sinograms in PET scanners has the potential to accelerate the overall reconstruction speed. Among the available rebinning techniques, Single-Slice Rebinning (SSRB) offers a computationally efficient approach.

Objective: This study aimed to evaluate the influence of varying span and Maximum Ring Difference (MRD) parameters in SSRB on the image quality of the Xtrim PET scanner.

Material and methods: This Monte Carlo simulation study used a GATE-simulated Xtrim-PET scanner. 3D list-mode data were histogrammed into 576 sinograms, and SSRB was applied to generate 2D sinograms. Subsequently, Maximum-Likelihood Expectation-Maximization (MLEM) reconstruction was performed on the sinograms with different MRD and span. Image quality was assessed using image quality, rod, and uniform phantoms. Furthermore, axial resolution was evaluated using point sources.

Results: Analysis of linear profiles in uniform phantom revealed a 2.6 mm inaccuracy in axial activity estimation when comparing spans of 21 and 7. Increased span and MRD lead to artifactual data in regions of high activity gradients, as observed in both uniform and rod phantoms. However, the Recovery Coefficient (RC) and Spilled-Over Ratio (SOR) remained unaffected. Concomitantly, increasing the span improved uniformity and reduced the coefficient of variation by 1.6% and 5.9%, respectively. Axial resolution remained largely unaffected by variations in span and MRD.

Conclusion: The RC and SOR remain robust to variations in span and MRD. However, higher levels of axial data compression were associated with the introduction of axial artifacts. Additionally, axial resolution was unaffected by increases in span and MRD, likely due to the limited field of view of the Xtrim-PET scanner.