动态监测骨质疏松性微结构退化的超声全波反演方法

Ultrasonic full-waveform inversion for dynamically monitoring bone micro-structure deterioration in osteoporosis progression

研究了基于全波反演(FWI)的骨骼超声层析成像方法,用于动态监测骨质疏松性微结构退化的进程。采用雌性小鼠注射药物建立骨质疏松症模型,在第0,2,4,6周通过Micro-CT扫描活体小鼠,重建获得小鼠股骨骨骼结构。以第0周骨骼结构为基准输入模型,通过不同的超声收发模式(透射、反射及透射-反射双模式),仿真分析了FWI监测不同骨质疏松进程的骨微结构退化的效果。结果表明,初始模型为均匀介质(纯水)时,FWI反演失效,不能准确重建骨骼结构。初始模型中考虑了基准骨骼结构(第0周)时,FWI能准确反演骨骼组织声速(均方根误差(RMSE)<17 m/s,平均相对误差(MRE)<7.2%),精确重建骨骼结构(结构相关系数(CC)>0.85),因此可以准确监测不同骨质疏松进程(第2,4,6周)的骨微结构退化情况。对比不同超声收发模式,透射-反射双模式FWI监测骨微结构退化的性能优于单一透射或反射FWI监测方法。考虑了基准骨骼模型的FWI可用于动态监测骨微结构退化,对评估骨质疏松进展具有一定意义。

The aim of this study is to investigate the method of ultrasound tomography of bone based on ultrasonic full-waveform inversion(FWI),and to dynamically monitor the progression of osteoporotic micro-structural deterioration.Female mice are injected with 4-vinylcyclohexene diepoxide(VCD)to induce premature ovarian failure and establish the mice osteoporosis model.The mice are scanned by Micro-CT in vivo at different osteoporosis progression(the 0,2,4 and 6 weeks),and bone micro-structure in the femurs of mice are reconstructed.Taking the initial bone micro-structure of mice(at the 0 week)as the baseline input model,the effects of FWI on monitoring bone micro-structure deterioration in osteoporosis progression are numerically analyzed,with different ultrasound transmitting and receiving modes(transmission,reflection and transmission-reflection dual mode).The results show that FWI failed to reconstruct bone micro-structure when using the uniform medium(pure water)as the initial model.Compared with the initial model with uniform medium(pure water),the FWI using the baseline bone(at the 0 week)model could accurately monitor the bone micro-structure deterioration in different osteoporotic processes(at the 2,4,6 week),the ultrasound velocity inversion is with a root-mean-square error(RMSE)<17 m/s,mean relative error(MRE)<7.2%,and structural correlation coefficient(CC)>0.85.Compared with different ultrasound transmitting and receiving modes,the combination of transmission-reflection dual-mode in FWI is significantly superior to the single transmission or reflection FWI in monitoring bone micro-structural deterioration.This study demonstrate that FWI using the baseline bone model can be used to dynamically monitor bone micro-structural deterioration and might have some significance in assessing the progression of osteoporosis.