REAL TIME VISUALIZATION TECHNIQUE OF IN VIVO CANCELLOUS BONE AND ESTIMATION SYSTEM OF MECHANICAL INTEGRITY

随着越来越多的人达到高龄，临床医生以及科学家和家庭医生对骨质疏松症产生了越来越大的兴趣。昂贵的被称为DXA(双能X射线吸收)密度计的机器可以扫描骨骼以提供准确的骨密度读数，但由于X射线暴露，这是有害的。到目前为止，还没有令人满意的筛查程序。因为骨质疏松的改变最初出现在松质骨中，直到晚期才检测到皮质变薄。因此，我们必须开发一种低成本、非侵入性的方法来评估体内骨密度(BMD)及其结构，它直接与骨折发生率、松质骨的骨小梁密度和方向以及松质骨的结构相关强度有关。本文提出了一种利用超声检查来可视化活体骨结构及其强度的新方法，该方法可以从力学完整性的角度诊断骨质疏松。研究结果如下：1)利用超声医疗仪器线阵探头的真实信号，建立了一种新的骨和松质骨骨髓可视化信号处理方法；给出了反射信号和阈值的数值表达式，然后以0.18×0.2 mm的小像素绘制出二维骨结构图。2)根据体积密度确定的构建结构的最佳阈值：骨为0.89~0.96，人造陶瓷泡沫样品--堇青石为~1.16。3)提出了一种基于超声检测和可视化结构有限元分析的体内松质骨力学完整性和骨折风险的评估方法，为开发实用的跟骨实时三维可视化设备奠定了基础。

With more people than ever reaching greater age, clinicians, as well as scientists and family doctors, have developed an increasing interest in osteoporosis. Expensive machines called DXA (dual energy x-ray absorptiometry) densitometers can scan bones to give an accurate reading of bone density, but this is harmful due to X-ray exposure. As yet, there is no satisfactory screening procedure. Because osteoporotic changes appear initially in the cancellous bone and it is only at an advanced stage that cortical thinning is detected. Thus, we must develop methods to inexpensively and non-invasively assess the in vivo bone mineral density (BMD) and its structure which can directly relate to fracture incidence, trabecular density and orientation, and architecture-related strength of cancellous bone. In the present report, a new method for visualizing in vivo bone architecture and its strength using ultrasound inspection is proposed, which can allow diagnose of osteoporosis from the viewpoint of mechanical integrity. The results are summarized as follows:1) A new signal processing procedures to visualize bone and bone marrow of cancellous bone has been established using the real signals from a linear array type probe of ultrasonic medical devise; a numerical expression for the reflected signal and threshold value were introduced, then 2D bone architecture was drawn by small size of pixel, 0.18 x 0.2 mm.2) The most suitable threshold value examined which was based on the bulk density to create architecture was 0.89〜0.96 for bone, and 〜1.16 for artificial ceramic foam specimen, cordierite,3) An estimation method of mechanical integrity, fracture risk, of in vivo cancellous bone has been proposed using ultrasound testing and finite element analysis for visualized architecture.Those results would allow development of a practical device of real time and 3-D visualization for heel bone.