Evaluation of visco-elasticity of local arterial wall using M-mode intravascular ultrasound

1.m型血管内超声成像系统的发展：为了利用血管内超声描绘任意方向的动脉壁m型图像，我们开发了一种全方位的m型血管内超声系统。在导管尖端安装一个中心频率为30 MHz的1mm x 1mm超声换能器，并在任意方向上描绘m型动脉壁图像。分辨率为0.15mm。此外，我们可以获得几乎实时的动脉壁二维图像。m型血管内超声评估人体动脉壁刚度：我们根据m型血管内超声测量的心脏周期瞬时动脉壁厚度与同期腔内压力之间的关系来评估局部动脉壁弹性特性。人肾动脉分支后，动脉硬度增加，向外周明显增加。此外，人动脉壁硬度随年龄增长而增加。这些发现与壁厚/管腔比的增加有关，这可能反映了与动脉硬化进展相关的动脉形态学改变。

1.Development of M-mode intravascular ultrasound imaging system :In order to depict arbitrary directional M-mode images of arterial wall using intravascular ultrasound, we developed an omni-directional M-mode intravascular ultrasound system. A 1mm x 1mm ultrasound transducer with 30 MHz center frequency, is mounted at the tip of catheter, and the M-mode arterial wall images are depicted in arbitrary direction. The resolution is 0.15mm. In addition, we can gain almost real time two-dimensional images of the arterial wall by the system.Assessment of stiffness of human arterial wall by M-mode intravascular ultrasound :We evaluated local arterial wall elastic property based on the relationship between instantaneous arterial wall thickness during cardiac cycle measured by M-mode intravascular ultrasound and simultaneous intraluminal pressure. In human, arterial stiffness increased after branching of the renal artery and increased greatly towards the periphery. In addition, human arterial wall stiffness increased with advancing age. These findings were related to an increase of wall thickness/luminal ratio, which may reflect a morphological change in the artery associated with the progression of arteriosclerosis.