Study On ¹⁸F-NAF PET/CT In The Model Of Steroid-induced Femoral Head Osteonecrosis In Rabbits

Objective:To study its imaging features of Micro-CT,X-ray,MRI and ¹⁸F-NaF PET/CT and pathological changes at 1,2,3,4 weeks after molding,by establishing rabbit model of steroid-induced femoral head osteonecrosis.Compare the findings of ¹⁸F-NaF PET/CT in steroid-induced femoral head osteonecrosis of rabbits with the findings of X-ray,MRI,micro-CT and histopathological,to explore the value of ¹⁸F-NaF PET/CT in the quantitative and qualitative diagnosis of early steroid-induced femoral head osteonecrosis in rabbits.Methods:36 healthy adult New Zealand white rabbits were selected and12 were divided into group A?the control group?and 24 were divided into group B?the model group?randomly.All rabbits were examined by X-ray,MRI,¹⁸F-NaF PET/CT at 1,2,3 and 4 weeks after modeling.The imaging manifestations of bilateral femoral head were observed,and the minimum standardized uptake value?SUVmin?,the maximum standardized uptake value?SUVmax?,mean standardized uptake value?SUVmean?of ¹⁸F^-were quantitatively determined.At 1,2,3 and 4 weeks after modeling,3 rabbits in group A and 5 rabbits in group B were sacrificed and bilateral femoral head specimens were taken out for micro-CT examination and histopathological examination at each time.Bone microstructure parameters were recorded including bone trabecular volume fraction?BV/TV?,bone trabecular number?Tb.N?,bone trabecular separation degree?Tb.Sp?and bone trabecular thickness?Tb.Th?.The percentage of empty bone lacunae was calculated and the incidence of osteonecrosis was calculated.Statistical analysis was performed on SUVmin,SUVmax and SUVmean values,bone microstructure parameters and histopathology.Statistical analysis was performed on SUVmin,SUVmax and SUVmean values,bone microstructure parameters and histopathology,and P<0.05 was considered statistically significant,and P<0.05 was considered statistically significant.Results:X-ray and conventional MRI at 1,2,3 and 4 weeks after modeling could not detect obvious femoral head osteonecrosis.From the second week after modeling,BV/TV,Tb.Th and Tb.N were significantly reduced compared with the control group at the same time node,P<0.05,and the difference was statistically significant.Tb.Sp was increased compared with the control group at the same time node,P<0.05,and the difference was statistically significant.In the model group,Tb.Th,Tb.N and Tb.Sp were compared at 1W,2W,3W and 4W,Tb.Th and Tb.N decreased gradually,while Tb.Sp increased gradually,compared with the previous time node,P<0.05,and the difference was statistically significant.Two weeks later,¹⁸F-NaF PET/CT images showed increased bone metabolism of the hip joint.SUVmax,SUVmin and SUVmean of 1W,2W,3W and 4W in the model group were all higher than those in the control group at the same time node,with P<0.01,and the difference was statistically significant.In the model group,horizontal comparisons of SUVmax,SUVmin and SUVmean were conducted at 1W,2W,3W and 4W.Compared with the previous time nodes,SUVmax,SUVmin and SUVmean presented a gradually increasing trend,P<0.01,and the difference was statistically significant.In the model group,at week 2,some femoral trabeculae showed increased adipocytes and empty bone lacunae,but the trabeculae were not ruptured.In the model group,trabecular fracture occurred in the fourth week,the number of empty bone lacunae increased significantly,and the bone marrow showed necrosis and dissolution,filled with a large number of hypertrophic fat cells,and some fused into vesicles.The hollow bone lacuna rate in the model group was compared at 1W,2W,3W and 4W.Compared with the previous node,the hollow bone lacuna rate increased gradually,P<0.05,and the difference was statistically significant.The success rates of 1W,2W,3W and 4W are 0%?0/10?,10%?1/10?,40%?4/10?and 60%?6/10?,respectively.Conclusion:The model of steroid-induced femoral head osteonecrosis in rabbits was successfully established by LPS combined with prednisolone acetate.During the first 4 weeks of modeling with this method,X-ray and MRI showed no abnormal imaging changes.Two weeks after modeling,¹⁸F NaF PET/CT images showed increased bone metabolism of the femoral head.¹⁸F NaF PET/CT can more early quantitatively evaluate the rabbit femoral head necrosis model of glucocorticoid,which is better than MRI examination and is a non-invasive sensitive examination method for the diagnosis of"pre-early"femoral head osteonecrosis.Bone metabolism showed a gradually increasing trend in early SONFH stage.