Inter observer reproducibility of SPECT-low dose CT in classifying indeterminate lesion on planar bone scan in...

to assess the inter observer reproducibility of Single Photon Computed Tomography-Computerised Tomography (SPECT-CT) in classifying indeterminate foci of abnormal metabolism on planar bone scan (PBS), in oncologic diseases, in the limit of performance of a low dose CT.

49 patients (27 men, 22 women) whose PBS showed indeterminate lesions underwent SPECT/CT. The mean age was 57 ± 13 years (range 22-80 years). Lesions were classified as malignant, benign or indeterminate by two readers. Inter observer agreement was assessed by a weighted Kappa test.

On PBS, readers identified 63 indeterminate lesions. SPECT-CT showed 95 lesions (31,7% lesion detected more than PBS). Reviewer 1 becomes more confident in final diagnosis of 45 patients. 4 cases remained indeterminate. For the second reviewer, final reports were modified in 37 cases. The Kappa value was 0,74. Scintigraphic, morphologic imaging and follow up identified no false negative and 2 false positive.

Despite the poor quality of images provided by a low dose scanner, side by side reading of SPECT-CT performs significantly better than planar bone scan for the detection and the classification of equivocal lesions with good inter reviewer agreement.