The Role of Reprojected Planar Data Derived from Fast Whole-Body Bone SPECT/CT

Background/Objectives: The purpose of this prospective study was to investigate the preferred reconstruction SPECT parameters for generating reprojected planar images in bone studies, and to evaluate, by visual reader assessment, the feasibility of using these reprojected images as a substitute for traditional planar whole-body (WB) bone scan images. This was a single-centre feasibility study; diagnostic accuracy was not assessed. Methods: Patients referred for planar bone scintigraphy (PBS) and WB-SPECT/CT were prospectively enrolled. Reprojected planar bone scintigraphy (R-PBS) data were generated using forward projection of the three-bed SPECT/CT data. Three nuclear medicine (NM) specialists, blinded to the imaging reconstruction, evaluated both sets of images in a randomised order. The preferred reconstruction parameters for R-PBS were determined by visual assessment using a 4-point ordinal visual scoring scale. A side-by-side comparison of PBS vs. R-PBS was conducted, including assessments of image quality, artefact generation, image preference, and any clinical significance that may affect report interpretation. The agreement between the physicians' evaluations was measured using the Kappa coefficient test. Results: Of the four reconstruction parameter combinations, 6 iterations, 8 subsets, and a 5 mm Gaussian post-filter yielded the highest visual quality scores. PBS images scored higher on image quality, though this difference was not statistically significant (p > 0.05). The inter-rater agreement for image quality scores was moderate for both PBS and R-PBS images. The results indicate that among the 33 reader-level assessments derived from 11 patient pairs and reviewed by the 3 readers, PBS images were preferred 13 times (~40%), R-PBS 10 times (30%), and no preference was indicated for the remaining 10 (30%). Conclusions: In this small feasibility cohort, R-PBS images derived from fast WB-SPECT/CT data were of visual quality comparable to PBS and may have potential as an alternative to PBS. If confirmed in larger studies with formal diagnostic accuracy assessment, R-PBS could remove the need for a separate PBS acquisition and reduce overall patient imaging time.