99mTc-Methylene diphosphonate SPECT/CT as the one-stop imaging modality for the diagnosis of osteoid osteoma.

Purpose: The aim of this study was to evaluate the utility of Tc-methylene diphosphonate (Tc-MDP) single-photon emission tomography (SPECT)/computed tomography (CT) for the diagnosis of osteoid osteoma and compare the same with three-phase planar bone scintigraphy (BS) and CT alone.

Materials And Methods: Data of 31 patients (age: 20.6±13.2 years; male: 80.6%) who had undergone Tc-MDP BS with SPECT/CT for clinically and/or radiographically suspected osteoid osteoma were retrospectively evaluated. Planar BS images were analyzed by an experienced nuclear medicine physician. CT images were evaluated by an experienced radiologist. SPECT/CT images were evaluated by the nuclear medicine physician and radiologist in consensus. On the basis of the diagnostic confidence the interpreters used a scoring scale of 1-3, in which 1 is negative for osteoid osteoma, 2 is equivocal, and 3 is positive for osteoid osteoma. For the calculation of sensitivity, specificity, and predictive values for planar BS, CT, and SPECT/CT an interpretive score of 2 or higher was taken as positive for osteoid osteoma. Receiver operating characteristic curve analysis was performed and the area under the curve was calculated and compared. Histopathology and microbiology/clinical imaging follow-up was used as the reference standard.

Results: There were nine equivocal lesions on planar BS and five equivocal lesions on CT, but none on SPECT/CT. The sensitivity, specificity, and accuracy of SPECT/CT were all 100%; those of CT were 77.8, 92.3, and 83.8% and those of planar BS were 100, 38.4, and 74.1%, respectively. On comparison, the area under the curve of SPECT/CT was significantly larger than that of planar BS (1.00 vs. 0.761; P=0.005) and CT (1.00 vs. 0.872; P=0.044). However, no significant difference was seen between planar BS and CT (0.761 vs. 0.872; P=0.236).

Conclusion: Tc-MDP SPECT/CT shows excellent diagnostic accuracy for osteoid osteoma and can be used as a one-stop imaging modality for the same. It is superior to planar BS and CT alone for the diagnosis of suspected osteoid osteoma.