Quantification of osteoblastic activity of the epiphyseal plate by quantitative bone SPECT/CT

Objectives: To quantify the function of the epiphyseal plate is worthwhile for the management of children with growth disorders. The aim of this retrospective study is to test the reliability of a novel SPECT/CT scanner for the quantification of osteoblastic activity by the uptake value of the epiphyseal plate in the bone scan.

Methods: A total of 16 patients (6--79 y, Female 8, Male 8, all Asian) who received Tc-99m HMDP bone scan acquired by a quantitative SPECT/CT scanner were enrolled in this study. Background of the patients were trauma (n = 2), malignant tumor (n = 3), and benign bone tumor or inflammation (n = 11). SPECT/CT images were reconstructed by Ordered Subset Conjugate-Gradient Minimizer, and standardized uptake value (SUV) was calculated by placing region of interest on the distal margin of each femur of left and right. A leg that has active tumoral or inflammatory lesion over the epiphyseal plate, and a leg that was missing were eliminated from the analyses. The patients were divided into 3 groups by their age; A (under 15 y, n = 5, 9 legs), B (between 15 to 19 y, n = 5, 9 legs), and C (over 20 y, n = 6, 10 legs). Differences among groups were compared by the Mann-Whitney U-test. For the group A and B, the relationship between age and maximum SUV (SUVmax) were also evaluated by the linear regression analysis. A p-value less than 0.05 was considered to be significant.

Results: Average ± standardized deviation of SUVmax in each group was 26.0 ± 3.3 in group A, 6.8 ± 3.0 in group B, and 4.6 ± 2.0 in group C, respectively. There was a significant difference between groups A and B (p < 0.001), whereas there was no significant difference between group B and C (p = 0.13). A significant negative linear correlation between age and SUVmax was observed in the groups of under 20 y (r = 0.91, p < 0.001).

Conclusion: The epiphyseal plates of children under 15 who have higher osteoblastic activity showed higher SUV measured by the quantitative bone SPECT/CT. This method has the possibility to be one of the objective and quantitative way to evaluate osteoblastic activity in the epiphyseal plates. Research Support: None