Quantitative evaluation of local biomechanics of thoracic aorta

本研究的目的是应用超声诊断仪建立主动脉壁生物力学定量测量系统，为动脉瘤破裂和手术提供客观指标。助学金期间研究的具体对象是利用血管内超声(IVUS)和经食道超声心动图测量主动脉壁局部弹性。临床IVUS仪器的射频信号经模拟/数字(A/D)转换器以500mSA/S的采样率采集并存储在工作站中。同时用10kSa/S的A/D转换器采集心电图和冠状动脉内压。计算了相邻火焰中相同地址的射频线的相关系数和位移。假设高相关性区域表示血管壁，实现了对血管壁的自动识别。当两帧之间相差33ms时，计算组织速度。组织速度成像定义为高相关区域的组织速度。用中心频率4~7 MHz的TEE获得降主动脉的短轴切面。同步记录心电图和血压。采用相邻帧感兴趣区平方模板匹配法计算二维组织速度矢量。比较IVUS所见与冠脉病变切除标本，TEE所见与手术切除标本比较，血压变化引起的被动运动与组织成分及巨噬细胞等炎性细胞的表达有关。最后介绍了超声技术在生物力学测量中的应用。

The objectives of the present study are to develop a quantitative measurement system of biomechanics of aortic wall by applying ultrasound diagnostics device and to establish an objective indication for rupture of aneurysm and operation. The concrete object of the research during grant-in-aid is to measure the local elasticity of aortic wall by using intravascular ultrasound (IVUS) and transesophageal echocardiography. (TEE)Radio-frequency (RF) signal of clinical IVUS apparatus was sampled via analogue/digital (A/D) converter with sampling rate of 500 MSa/s and stored in a workstation. Electrocardiogram and intracoronary pressure were also sampled via A/D converter with 10 kSa/s, simultaneously. The correlation and displacement of RF lines of the same address in neighboring flames were calculated. Assuming that high correlation area indicated vascular wall, automatic recognition of vascular wall was performed. Tissue velocity was calculated as the difference of the frames was 33 ms. Tissue Velocity Imaging was defined as the tissue velocity in high correlation areas. Short axis view of descending aorta was obtained by a TEE with the central frequency of 4-7 MHz. Electrocardiogram and blood pressure were recorded simultaneously. Two dimensional tissue velocity, vectors were calculated by template matching method of squared region of interests in neighboring frames. IVUS findings and excised specimen by directional coronary atherectomy were compared and TEE findings and surgicaly excised specimen were compared The passive movement by blood pressure variance was correlated with tissue components and expression of inflammatory cells such as macrophages. Finally, precise measurement of biomechanics by applying ultrasonic technology was shown in the present research.