Evaluation of Progression of Arteriosclerosis by the Quantitative Assessment of Acoustic Tissue Characteristics Using Acoustic Microscopy

本研究的目的是检查我们是否可以评估心肌活力的声学特性和弹性性能的基础上，通过测量超声衰减，传播速度，体积模量与扫描声学显微镜。本研究采用犬冠状动脉前降支（LAD）阻断15分钟，再灌注60分钟，观察缺血心肌（如顿抑心肌）的声学特性。心肌标本（顿抑心肌）取自缺血区心肌内膜，切成4 μ m厚，无石蜡切片.光镜和电镜观察均未发现缺血心肌与正常心肌有明显差异。电镜下可见线粒体和动脉膜轻微肿胀，缺血心肌细胞轻度水肿。传播速度为1656（±）SY。[)36m缺血心肌（顿抑心肌）为1657（]SY. ±[)8m/s正常。两者之间无显著性差异。因此，我们认为顿抑心肌的微小变化不会引起声学特性的显著变化。此外，为了评估缺血心肌的硬度，我们采用了一种新的方法来测量组织标本的体积模量和密度。为了测量试样的体积模量和密度，研制了一种覆盖在试样上的声学覆盖膜。该覆盖膜由聚碳酸酯制成，并置于样品和传播介质之间。从覆盖膜反射的信号的强度表示样品的声阻抗（Zs）。因此，如果我们使用这种覆盖膜使用声学显微镜测量样品的Zs和Vs，我们可以估计样品的Ks和rhos如下：Ks=ZsVs，rhos=Zs/Vs，这样我们就可以评估缺血心肌的硬度。

The aim of this study is to examine whether we can evaluate myocardial viability based on acoustic characteristics and elastic properties by measuring the ultrasonic attenuation, propagation velocity, and bulk modulus with a scanning acoustic microscopy. We investigated acoustic properties in ischemic myocardium such as stunned myocardium.The dogs were studied during 15 min of temporary LAD occlusion followed by 60 min of reperfusion. Myocardial specimens (stunned myocardium) which were obtained from endocardium in ischemic regin, were cut in 4 micron thickness, and prepared without paraffin on slide glass.1. We could not find any differences between iscemic myocardium (stunned myocardium) and normal using optical microscopy and electron microscopy. Using electron microscopy, only minimal swelling of the mitochondria and arcolemma was noted, with scattered evidence of mild cellular edema present in iscemic myocardium.2. Propagation velocity was 1656(]SY.+-[)36m/s in iscemic myocardium (stunned myocardium), and was 1657(]SY.+-[)8m/s in normal. There was no significant difference between them. Therefore, we considered that minimal changes in stunned myocardium produced no significant changes in acoustic properties.3. Furthermore, in order to evaluate the hardness of the ischemic myocardium, we use a new method to measure the bulk modulus and density of tissue specimen. We developed an acoustic cover membrane covering specimen in order to measure bulk modulus (Ks) and density (rhos) of specimen. This cover membrane is made of polycarbonate and is interposed between the specimen and the propagating medium. The intensity of the signal reflected from the cover membrane represents the acoustic impedance (Zs) of the specimen. So, if we measure Zs and Vs of specimen using the acoustic microscopy with this cover membrane, we can estimate Ks and rhos of specimen as follows ; Ks=ZsVs, rhos=Zs/Vs. In this way, we can evaluate the hardness of ischemic myocardium.