Abstract: Objective To study the clinical value of contrast enhanced ultrasound in evaluating the early vascularization of bone grafts during regeneration process and provide early diagnostic information for impaired bone regeneration.Methods An ectopic bone formation model was established in 25 male Sprague Dawley (SD) rats with Calcium phosphate cement/recombination human bone morphogenetic protein-2(CPC/rhBMP-2) in the left posterior leg proximal femoral head muscle space of the rats.High frequency ultrasound,CEUS and pathological examination were performed at 3,7,14,21,28 days after operation.Blood perfusion and osteogenesis in CPC/rhBMP-2 were compared with pathological results at different time points.Results 3 days after operation,CEUS showed a small amount of stellate contrast media perfusion on the periphery of the stent.As time went on,CEUS showed that the contrast medium was filling gradually into the center,and quantitative analysis of time intensity curve showed that the peak intensity (PI) and area under the curve (AUC) gradually increased,PI and AUC reached the maximum value at 14 days after operation.Later,the PI and AUC of the contrast medium decreased at the 21 day and the 28 day after operation,the differences among the groups were statistically significant (p<0.05),while there was no significant difference in peak time at each time point (p>0.05).Pathological examination was showed as follows:different degrees of neovascularization occurred in the grafts at the 3,7,14,21,28 days after operation and the number of vascularization at the 14 days after operation was the most obvious,which were consistent with the CEUS examination.Conclusion Neovascularization of CPC/rhBMP-2 can be displayed early with the use of CEUS,which can provide a valuable diagnostic evidence for the growth assessment of transplanted bones and impaired bone regeneration.