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研制：为了利用血管内超声显示任意方向的动脉壁M型图像，我们研制了一套全方位M型血管内超声成像系统。中心频率为30 MHz的1 mm×1 mm超声换能器安装在导管末端，M型动脉壁图像可在任意方向上显示。分辨率为0.15 mm。M型血管内超声评价人体动脉壁硬度：我们根据M型血管内超声测量的心动周期瞬时动脉壁厚度与同时腔内压之间的关系来评价局部动脉壁的弹性特性。在人类中，肾动脉分支后动脉僵硬增加，并向外周方向显著增加。此外，人的动脉壁硬度随着年龄的增长而增加。这些发现与管壁厚度/管腔比的增加有关，这可能反映了动脉的形态变化与动脉硬化的进展有关。

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.