Characterization of focal bone lesions in the axial skeleton: performance of planar bone scintigraphy compared with SPECT and SPECT fused with CT.

OBJECTIVE: The purpose of this study was to evaluate the diagnostic performance of planar 99mTc methylene diphosphonate bone scintigraphy compared with SPECT and SPECT fused with CT in patients with focal bone lesions of the axial skeleton. SUBJECTS AND METHODS: Thirty-seven patients with 42 focal lesions of the axial skeleton were included in this prospective study. All patients underwent planar scintigraphy, SPECT through the focal lesions, and SPECT-guided CT. SPECT and CT images then were fused digitally. The three types of images were evaluated separately from one another by two experienced reviewers working to consensus. Visibility of the lesions, diagnostic performance, and certainty in diagnosis were evaluated. Performance for specific diagnoses also was evaluated. Histologic, MRI, and clinical follow-up findings were used as the reference standard. RESULTS: Visibility of the lesions was significantly better with SPECT than with planar scintigraphy (p < 0.0001). Sensitivity and specificity for differentiation of benign and malignant bone lesions were 82% and 94% for planar scintigraphy, 91% and 94% for SPECT, and 100% and 100% for SPECT fused with CT. Differences between the three methods of differentiating benign and malignant lesions did not reach statistical significance. Certainty in diagnosis was significantly higher for SPECT fused with CT than for planar scintigraphy (p = 0.004) and SPECT (p = 0.004). A specific diagnosis was made with planar scintigraphy in 64% of cases, with SPECT in 86%, and with SPECT fused with CT in all cases. CONCLUSION: Planar scintigraphy may suffice for differentiating benign and malignant lesions of the axial skeleton, but SPECT fused with CT significantly increases certainty in diagnosis and is the best tool for making a specific diagnosis.