Material and Method: Eighty diagnosed or suspected cancer patients with indeterminate lesions on planar scintigraphy were recruited in the present prospective study. Additional whole body Evolution SPECT/CT was performed after whole body planar scintigraphy. All lesions on both imagings were categorized into 5 categories; definitely metastasis, probably metastasis, indeterminate, probably benign and definitely benign. The diagnosis of each lesion was confirmed by follow-up imaging, pathological findings or clinical follow-up for at least 6 months.

Results: Detected lesions on planar scintigraphy and Evolution SPECT/CT imaging were 442 and 477 lesions, respectively.The sensitivity, specificity and accuracy of planar scintigraphy and Evolution SPECT/CT imaging in the diagnosis of metastatic lesions were 27% (95% CI: 13.8, 44.1), 63.2% (95% CI: 58.5, 67.7), 60%, and 97.3% (95% CI: 85.8, 99.9), 100% (95% CI: 96.4, 100) and 99.8%, respectively. Indeterminate lesions on planar scintigraphy were 34.2% (151 lesions from total 442 lesions, which 135 of these 151 indeterminate lesions or 89.4% were located in axial skeleton). Evolution SPECT/CT images were able to characterize all indeterminate lesions.

Conclusion: Differentiation of benign and metastatic lesions by Evolution SPECT/CT images has superior diagnostic performance and diagnostic confidence over the planar scintigraphy. Thus, Evolution SPECT/CT images should be considered in characterization of indeterminate lesions on planar scintigraphy, especially in the axial skeleton.

Keywords: Bone scan, planar scintigraphy, Evolution SPECT/CT, bone metastases