Differential diagnostic value of single-photon emission computed tomography/spiral computed tomography with Tc-99m-methylene diphosphonate in patients with spinal lesions.

PURPOSE

The objective of this study was to compare the diagnostic value obtained using single-photon emission computed tomography (SPECT)/spiral computed tomography (CT) with Tc-99m methylene-diphosphonate with that obtained using SPECT alone in patients with spinal lesions.

METHODS

This was a retrospective study of 56 patients who underwent planar whole-body scintigraphy because of bone pain or osseous lesions that had been detected by other imaging techniques, or for the investigation of bone metastasis in patients with extraskeletal malignancies. Only patients who had hot spots detected in their spine and who had undergone single-photon emission computed tomography/computed tomography (SPECT/CT) imaging were included. One lesion from each patient was resected or biopsied for pathological diagnosis, and lesions for which a pathological diagnosis could be made were included in this study. Single-photon emission computed tomography (SPECT) and SPECT/CT images were independently interpreted by two experienced nuclear medicine physicians who had not been involved in the selection of data for the study. The physicians were aware of patients' sex, age, history of histologically confirmed extraskeletal malignancy, and whole-body scintigraphy results, but were unaware of the results of other investigations, such as X-ray, MRI, and laboratory tests. SPECT images were analyzed first, followed by SPECT/CT images. Each lesion was graded on a 4-point diagnostic scale (1, benign; 2, likely benign; 3, likely malignant; 4, malignant), and the inter-reviewer agreement and the agreement of the SPECT and SPECT/CT diagnoses with the pathology results were evaluated by κ scores.

RESULTS

The pathology results revealed 39 malignant bone tumors and 17 benign lesions. In the malignant cases, 20 were bone metastases and 19 were malignant tumors of another histological type. The reviewers rated 67.9% of lesions as equivocal (grade 2-3) by SPECT, but only 19.6% as equivocal by SPECT/CT. The κ scores for inter-reviewer agreement were 0.467 for SPECT and 0.905 for SPECT/CT (both P<0.0001). The κ scores for the agreement of the interpretation of SPECT and SPECT/CT with the pathology results were 0.493 and 0.689, respectively (both P<0.0001).

CONCLUSION

Compared with SPECT imaging, SPECT/spiral CT hybrid imaging significantly reduced the number of lesions judged to be equivocal. This reduction allowed for a definitive diagnosis to be made by imaging in the majority of patients.