Maximum standardized uptake value from quantitative bone single-photon emission computed tomography/computed tomography in differentiating metastatic and degenerative joint disease of the spine in prostate cancer patients.

OBJECTIVE: Qualitative interpretation in bone scan is often complicated by the presence of degenerative joint disease (DJD), especially in the elderly patient. The aim of this study is to compare objectively 99m Tc-MDP tracer uptake between DJD and osseous metastases of the spine using semi-quantitative assessment with SPECT SUV.

METHODS: Bone scan with SPECT/CT using 99m Tc-MDP was performed in 34 patients diagnosed with prostate carcinoma. SPECT/CT was performed based on our institutional standard guidelines. SUVmax based on body weight in 238 normal vertebrae visualized on SPECT/CT was quantified as baseline. A total of 211 lesions in the spine were identified on bone scan. Lesions were characterized into DJD or bone metastases based on its morphology on low-dose CT. Semi-quantitative evaluation using SUVmax was then performed on 89 DJD and 122 metastatic bone lesions. As most of the bone lesions were small in volume, the effect of partial volume effect (PVE) on SUVmax was also assessed. The corrected SUVmax values were obtained based on the recovery coefficient (RC) method.

RESULTS: The mean SUVmax for normal vertebrae was 7.08 ± 1.97, 12.59 ± 9.01 for DJD and 36.64 ± 24.84 for bone metastases. The SUVmax of bone metastases was significantly greater than DJD (p value < 0.05). To assess for diagnostic accuracy, receiver operating characteristic (ROC) curve was performed. The area under the curve (AUC) was found to be fairly high at 0.874 (95% CI 0.826-0.921). The cutoff SUVmax value ≥ 20 gave a sensitivity of 73.8% and specificity of 85.4% in differentiating bone metastases from DJD. The corrected SUVmax for both DJD and bone metastases was smaller with a mean of 6.82 ± 6.02 and 24.77 ± 20.61, respectively. The cutoff SUVmax value was also lower with a value of 10, which gave a sensitivity of 73.8% and specificity of 86.5%.

CONCLUSION: SPECT SUVmax was significantly higher in bone metastases than DJD. Semi-quantitative assessment with SUVmax can complement qualitative analysis. A cutoff SUVmax of ≥ 20 can be used to differentiate bone metastases from DJD. Partial volume effect should be taken into consideration in the quantification of small lesion size.