To explore the stability, distribution, and influencing factors of standardized uptake value (SUV) measured by ^99mTc-MDP SPECT/CT imaging of the normal lumbar spine, as well as its value in bone mineral density (BMD) evaluation.

A total of 103 patients [13 males and 90 females; age: (54.86±7.84) years] who underwent lumbar vertebra ^99mTc-MDP SPECT/CT and BMD evaluation by dual-energy X-ray absorptiometry at 30 days before or after SPECT/CT from May 2021 to June 2023 were retrospectively analyzed. Clinical data, SUVmax, SUVmean, CT value, and BMD of the lumbar spine were collected. The consistency and correlation of lumbar SUV measured by different observers were analyzed by Bland Altman and Pearson correlation analysis. The correlation between lumbar SUV, BMD, CT values, and various parameters was analyzed by Pearson correlation analysis. One-way ANOVA was used to compare the differences of various parameters in subjects with different BMD, and the LSD test was used for comparisons between groups.

SUVmax and SUVmean showed a good consistency and high correlation between observers, with 1.3% and 3.3% of points located outside the 95% limits of agreement, respectively (r =0.985 and 0.850, respectively, P<0.001 for both). The SUVmax and SUVmean of all 504 lumbar vertebra were 7.91±2.26 and 4.70±1.40, respectively. TLumbar SUVmax and SUVmean gradually increased from L₁ to L₃, with L₃ having the highest value, followed by L₅ and L₄. Lumbar SUVmax and SUVmean were significantly negatively correlated with age (P<0.05 for both), and positively correlated with body mass (P<0.001 or 0.05), BMI (P<0.001 for both), and CT value (P<0.05 for both), but they had no significant correlation with height. Lumbar SUVmax and SUVmean were signifcantly positively correlated with BMD obtained in the same period in 83 patients (P<0.05). Lumbar BMD and CT value were significantly negatively correlated with age (P<0.05 or 0.001), and BMD was positively correlated with CT value (P<0.001). There were statistically significant differences in SUVmax, SUVmean, BMD, and CT values among patients with different BMD (P<0.001 for all).

SUV measured by quantitative SPECT/CT bone imaging is easy to obtain and stable. The distribution and influencing factors must be considered when lumbar SUV is applied in clinical practice. SPECT/CT bone imaging for measuring lumbar SUV has high value in BMD evaluation.