The new SPECT/CT reconstruction algorithm xSPECT Bone®: reliability and accuracy in daily practice for non-oncologic bone diseases

Objectives: xSPECT Bone ® (xB) is a new reconstruction algorithm developed by Siemens ® in bone hybrid imaging (SPECT/CT). A CT-based tissue segmentation is incorporated into SPECT reconstruction to provide SPECT images with bone anatomy appearance. The objectives of this unique study were, in a context of daily practice, to compare interobserver agreement (IOA) and diagnostic accuracy between two Siemens ® reconstructions (a new one xB/CT and the commonly used Flash 3D ® (F3D)/CT). Methods: Two hundred thirteen consecutive patients referred to the Brest nuclear medicine department for non-oncological bone diseases were evaluated retrospectively. Each SPECT/CT was performed on a Symbia Intevo T6 gamma camera (Siemens ®). Two hundred seven SPECT/CT were included (7 patients were excluded and 2 SPECT/CT were performed for the same patient). All SPECT/CT were independently interpreted by two nuclear physicians (one junior and one senior expert) with xB/CT then with F3D/CT three months later. The diagnoses were classified into 5 categories (Normal scintigraphy; Arthritis; Abarticular disease; Fracture or tumour pathology; Complex Regional Pain Syndrome). IOA and diagnostic accuracy were determined using a McNemar test, an unweighted Kappa coefficient and using the clinical and paraclinical follow-up of more than 18 months. Results: No statistically significant difference between IOA xB and IOA F3D were found (p = 0,532). Agreement for xB after categorical classification of the diagnoses was high (κ xB = 0,89 [95% CI 0,84 - 0,93]) but without statistically significant difference with that of F3D (κ F3D = 0,90 [95% CI 0,86 - 0,94]). Thirty-one (14,9%) inter-reconstruction diagnostic discrepancies were observed whose 21 (10,1%) were classified as major. The follow-up confirmed the diagnosis of F3D in 10 cases, xB in 6 cases and was non-contributory in 5 cases. Conclusion: xB reconstruction algorithm was found reliable, providing high interobserver agreement with similar performances to F3D reconstruction in a context of daily practice. Nevertheless we believe it provides a strong added value to the SPECT/CT images thanks to a striking aesthetic aspect, with the condition of a strict spatial agreement between the SPECT and the CT acquisitions to obtain interpretable xB images.