Added value of SPECT/spiral CT versus SPECT or CT alone in diagnosing solitary skeletal lesions

Summary Aim: The aim of this study was to investigate the added value of SPECT/spiral CT versus SPECT or CT alone in the differential diagnosis of solitary skeletal lesions.Methods: This was a retrospective study on a total of 69 patients who had a solitary skeletal “hot spot” that could not be definitively diagnosed using planar scintigraphy. Thus, SPECT/ spiral CT was performed on the indeterminate lesions. SPECT, CT and SPECT/spiral CT images were independently interpreted by two experienced doctors who have both identification of CT and nuclear medicine. Each lesion was graded on a 4-point diagnostic scale (1: benign, 2: likely benign, 3: likely malignant, 4: malignant). The final diagnosis of each lesion was based on pathological confirmation after surgery within 3 weeks of the bone scan.Results: Final diagnoses based on the pathological results revealed that 43 of the 69 patients were diagnosed with malignancy, and the remaining 26 patients were diagnosed as having benign lesions. For SPECT and CT scans, both of the reviewers rated 55.1% (38/69) and 37.7 % (26/69) of lesions as equivocal, with the help of SPECT/CT, 33.3 % (23/69) of lesions were rated as equivocal. The diagnostic accuracies of SPECT, CT alone and SPECT/CT were 66.7 % (46/69),82.6 % (57/69) and 85.5 %(59/69), respectively. The kappa scores for the degree of agreement between SPECT, CT alone or SPECT/CT with pathological results were 0.185 (p = 0.054), 0.612 (p < 0.001) and 0.671 (p < 0.001), respectively.Conclusion: Compared with SPECT or imaging alone, SPECT/ spiral CT imaging was more accurate and valuable in the differential diagnosis of solitary skeletal lesions and resulted in significantly fewer equivocal findings.