^99mTc-Annexin V SPECT imaging of femur head avascular necrosis in rabbits: a comparison with ^99mTc-MDP bone scan

Objectives To compare early detection effect of apoptosis ^99mTc-Annexin V SPECT imaging with ^99mTc-MDP bone imaging in a rabbit model of early avascular necrosis of femur head.

Methods Adult New Zealand white rabbits were i.m. injected methylprednisolone (7.5 mg/kg) twice per week for up to 8 weeks to generate femur head necrosis model (n=32). Sixteen rabbits were treated with saline as control. ^99mTc-Annexin SPECT and ^99mTc-MDP SPECT were performed 5, 6, 7 and 8wk after treatment, each point included 8 methylprednisolone treated rabbits and 4 with saline (control). Rabbits were scarified after SPECT studies and bilateral femoral heads were removed and sectioned to detect cells apoptosis by TUNEL.

Results Femur head apoptosis cells index was significant higher in 5, 6, 7 and 8 after methylprednisolone treatment (26.82±2.48, 28.73±2.36, 29.54±2.12 and 32.82±2.48, respectively) than saline control (3.51±1.24, 4.13±1.67, 3.78±1.32, 3.49±1.53) (P<0.001). ^99mTc-Annexin V uptake in the femur head was significant higher in disease group (T/N: 2.16±0.73, 2.67±0.54, 3.14±0.73 and 3.18±0.72) at each imaging time points than controls (1.34±0.47, 1.42±0.54, 1.28±0.63, 1.43±0.52) (P<0.01 in all). On the other hand, significantly increased in femur head ^99mTc-MDP uptake was observed only 8 weeks after methylprednisolone treated rabbits (T/N: 5.49±0.63 vs controls 2.83±0.51)(P<0.01), but not earlier. Furthermore, ^99mTc-Annexin V uptake was positively correlated with apoptosis cells index, not ^99mTc-MDP.

Conclusions ^99mTc-Annexin V apoptosis imaging is superior to ^99mTc-MDP bone imaging for early detection of glucocorticoid-induced avascular necrosis of femur head in the rabbit. ^99mTc-Annexin V apoptosis imaging may early predict glucocorticoid-induced avascular necrosis in clinical setting.

Research Support This study was supported by Natural Science foundation of China (81360224)