Quantification of bone metabolic activity in the natural course of fractural lesions measured by quantitative...

While increased uptake at the bone fractural site gradually decreases over time on bone scans, the rate of change has not been quantitatively evaluated. The purpose of this study was to quantify the extent of bone metabolic changes in fractural lesions on bone SPECT/CT.

We reviewed bone scans acquired by dedicated SPECT/CT and chose those scans in which quantitative SPECT/CT of the same range was acquired twice or more. We set the region of interest on lesions of bone fracture and degeneration, and measured the maximum standardized uptake value (SUV_max). From the SUV_max of lesions and the interval between scans, a value for 30-day change in SUV_max was calculated as ∆SUV_max30d. The relationship between preSUV_max, SUV_max for the first scan of the comparison, and ∆SUV_max30d was evaluated utilizing a linear least-squares method. Furthermore, we assessed the ability to differentiate between fracture and degeneration using receiver operating characteristics (ROC) analysis and the Mann-Whitney U test. All cases were then categorized into five groups according to preSUV_max. Values of p <0.05 were considered statistically significant.

We investigated 175 scans from 60 patients and analyzed scan combinations for 157 fractural lesions and 266 degenerative lesions. The relationship between preSUV_max of fractural lesions and ∆SUV_max30d was approximated as ∆SUV_max30d =-0.15×preSUV_max +1.35 (R ²=0.60, p<0.0001). Area under the curves for all cases, 30≤ preSUV_max, 20≤ preSUV_max <30, 15≤ preSUV_max <20, 10≤ preSUV_max <15, and preSUV_max <10 were 0.73, 0.89, 0.86, 0.80, 0.91, and 0.59, respectively. Median ∆SUV_max30d was significantly lower at fractural lesions than at degenerative lesions (-0.62 vs -0.04; p <0.0001). As for analyses of groups divided by preSUV_max, all median ∆SUV_max30d for fractural lesions were significantly lower than those of degenerative lesions except for the group with preSUV_max <10.

The increased uptake at the fractural bone lesion observed in the quantitative bone SPECT/CT gradually decreased at the rate of SUV 0.15 per month, which showed a different trend with degenerative change.