Diagnostic value of ⁹⁹mTc-MDP SPECT/spiral CT in assessing indeterminate spinal solitary lesion of patients without malignant history.

OBJECTIVE: Metastases and benign conditions of spine are common, however, the diagnoses of imaging modalities in the nature of spinal lesions are difficult, especially for the solitary lesions in spine. This study aims to retrospectively evaluate the diagnostic value of single photon emission computed tomography (SPECT)/spiral computed tomography (CT) in assessing indeterminate spinal solitary lesion of patients without certain medical history of malignancies.

METHODS: A total of 48 patients (28 male, 20 female, average 54.9 ± 14.8 years) without malignant history but with a solitary lesion of spine on the Tc-99m-methylene diphosphonate planar scintigraphy, were enrolled in this study. SPECT/spiral CT was simultaneously performed on the abnormal lesions of the spine. SPECT alone and SPECT/spiral CT images were independently analyzed and interpreted by two experienced nuclear medicine physicians. Finally, the indeterminate spinal single lesion was confirmed with pathological results. The agreements of the SPECT and SPECT/spiral CT diagnoses with the pathology were evaluated using a weighted kappa score, respectively.

RESULTS: Among 48 patients, the pathological results revealed 37.5 % (18/48) benign and 62.5 % (30/48) malignant lesions. For SPECT alone, 6 of 18 benign cases and 28 of 30 malignant conditions were correctly diagnosed. For SPECT/spiral CT, 9 of 18 benign and 29 of 31 malignant lesions were exactly judged. For these patients without malignant history, the diagnostic accuracy, specificity, positive predictive value, and negative predictive value of SPECT and SPECT/spiral CT in assessing abnormal spinal solitary lesion were 70.8 % (34/48) vs 79.2 % (38/48), 33.3 % (6/18) vs 50.0 % (9/18), 70.0 % (28/40) vs 76.3 % (29/38), 75.0 % (6/8) vs 90.0 % (9/10), respectively. Moreover, the kappa scores for the agreement of SPECT alone and SPECT/spiral CT with the pathological confirmation were 0.300 and 0.512, respectively (both P < 0.005).

CONCLUSIONS: Compared with SPECT imaging, hybrid SPECT/spiral CT imaging improves the diagnostic accuracy and specificity in evaluating indeterminate spinal solitary lesion of patients without certain malignant history. Moreover, based on whole-body bone scan with high sensitivity, cheap price, widespread and time-saving use, SPECT/spiral CT is a good imaging modality for the diagnosis and evaluation of the nature of solitary lesion in spine.