Diagnostic Performance of SPECT/CT Versus Diffusion-Weighted Mri in Characterization of Indeterminate Osseous Lesions Detected on Bone Scan

Abstract Background: Characterization of solitary osseous lesions on planar bone scintigraphy (PBS) is challenging. In this pilot study, we aimed to explore the diagnostic performance of 99mTc-MDP bone scintigraphy using SPECT/CT in comparison to magnetic resonance imaging including diffusion-weighted imaging (MR-DWI) in patients with solitary indeterminate osseous lesions detected on PBS. Methods: This pilot study prospectively recruited 46 cancer patients who underwent PBS, with a finding of a solitary osseous lesion that was deemed indeterminate by two nuclear medicine physicians not involved in subsequent reading. A targeted SPECT/CT and MR-DWI were read independently by two nuclear medicine physicians and two radiologists, respectively, on a 5-point probability score. The final diagnosis of disease status was formulated from subsequent clinical/imaging follow-up within six months. Results: Agreement between SPECT/CT readers was 0.73 (95% confidence interval [CI]:0.51-0.85) and 0.99 (95%CI:0.99-1.00) between MR-DWI readers. According to the follow-up, 16/46 patients proved to have osseous metastasis. The area under the curve (AUC) from ROC analysis was 0.79 (95%CI:0.65-93) for SPECT/CT and 0.73 (95%CI:0.57-0.89) for MR-DWI. No statistically significant difference was noted regarding sensitivity or specificity. MR-DWI was more accurate for lesions located in the appendicular skeleton (n=17; AUC=0.92,95%CI:0.68-1.0) compared to axial lesions (n=29; AUC=0.65,95%CI:0.45-0.81). The performance of SPECT/CT was comparable for both sites. Diagnostic indices from both modalities were comparable for sclerotic and non-sclerotic lesions on the CT part of SPECT/CT.Conclusions: In this exploratory report, no significant difference was seen in the overall diagnostic performance between SPECT/CT and MR-DWI for characterization of solitary indeterminate osseous lesions depicted on PBS. MR-DWI results were more reproducible; however, the overall accuracy of MR-DWI varied according to lesion site, density patterns on CT, and the primary tumor type. Such differences were less obvious with SPECT/CT.