Toward an optimized PET reconstruction protocol for spinal cord: superiority of OSEM with TOF and PSF

Although multiple PET reconstruction approaches have been successfully applied in brain and oncologic imaging, their performance in the context of spinal cord imaging remains unverified. This study aims to identify the optimal reconstruction method for spinal cord PET image analysis based on assessments of image quality and quantitative uptake.

We retrospectively analyzed ¹⁸F-fluorodeoxyglucose (FDG) PET/MR data from 22 patients with cervical spinal cord tumors. PET images were reconstructed using Ordered Subset Expectation Maximization (OSEM), OSEM + Point Spread Function (PSF), OSEM + Time-of-Flight (TOF), and OSEM + TOF + PSF algorithms. Image quality was assessed by noise, signal-to-noise ratio (SNR), and signal-to-background ratio (SBR), both overall and within equally sized small (n = 11) and large (n = 11) tumor subgroups. Tumor uptake metrics, including SUV_mean, SUV_max, SUVR_mean, and SUVR_max of the lesions, were quantified for each method. The differences among reconstruction methods were assessed using the Friedman test.

There were no significant differences in image noise among reconstruction methods (P > 0.05). Compared to OSEM reconstruction, the OSEM + PSF + TOF method significantly improved SNR (Z = 3.62, P < 0.01) and SBR (Z = 2.80, P = 0.03); the SBR of OSEM + PSF + TOF was also significantly higher than that of OSEM + PSF (Z = 3.04, P = 0.01). In large tumors, while image noise remained unaffected by the reconstruction method (P > 0.05), both SNR and SBR were significantly impacted (both P < 0.05). Specifically, OSEM + TOF + PSF achieved significantly higher SNR compared to OSEM (Z = 3.30, P < 0.01), and higher SBR compared to OSEM + PSF (Z = 3.14, P = 0.01). Quantitative lesion uptake metrics (SUV_max, SUV_mean, SUVR_max, and SUVR_mean) were significantly higher for OSEM + TOF + PSF compared to both OSEM and OSEM + PSF reconstructions (all P < 0.05). Additionally, SUV_mean (Z = 2.92, P = 0.02) and SUVR_mean (Z = 2.83, P = 0.03) values from OSEM + TOF + PSF reconstruction were significantly higher than those from OSEM + TOF.

The OSEM + PSF + TOF reconstruction method demonstrated significant advantages in both image quality and quantitative assessment of FDG uptake, making it the recommended choice for spinal cord PET image reconstruction.