基于光声多普勒效应的模拟微血管血流三维速度矢量测量

The measurement of blood flow status in small branch blood vessel or micro-blood vessel is the main method of avoiding blood vessel lesion ,hemorrhage , ischemia and it is also the main method of the evaluatioin of vascular anastomosis effects in cerebrovascular disease, blood microcirculation disorder,limb replantation and so on.It is also the main index of chronic vascular lesions. Miro-blood velocity measurement based on photoacoustic doppler effects is a promising method which could overcome the limitations of conventional ultrasoud and angiography. It also can unify the advantages of spatial resolution, velocity resolution and detecting depth together. However, the current research was focused mainly on 1D velocity measurement and this brings large measurement error. It is not propitious for the velocity measurement in microcirculation network. In order to solve the problem, the proposed project plan to carry out the research of 3D velocity vector measurement in micro-blood vessel based on photoacoustic doppler effects:1)In experiment, a pulsed laser will be used as the pumping source to generate photoacoustic signal. Using the micro-blood vessel in optically scattering media as the tissue-mimicking phantom, the time domain photoaoustic signal of carbon particles or whole blood will be collected sequentially by three transducer orthogonal distributed in space.2)In theory , because the central frequency shift of the wide band photoacoustic signal was not obvious, a time domain correlation method will be used to calculate the velocity vector components .The corresponding theoretical model of multi-transducer time domain correlation will also be set up.

对细小分支血管和微血管进行血流状态检测是心脑血管病、血液微循环障碍、指(肢)再植等手术及介入治疗中避免血管损伤、评价血管吻合效果、防止出血和缺血的主要手段，也是慢性血管病变的主要诊断指标。基于光声多普勒效应的微血管血流检测有望克服传统多普勒超声和血管造影的局限性，实现空间分辨率、速度分辨率、探测深度的统一，但目前的研究主要是速度一维分量的测量，这对微血管内流速不高的血流会带来较大的测量误差，对血液微循环网络的流速测量也非常不利。为此，本项目拟开展基于光声多普勒效应的三维血流速度矢量测量研究:1）实验上，以脉冲激光为激励源，针对光散射介质中的模拟微血管血流，采用空间正交分布的三个超声探头连续采集流动碳颗粒或全血的时域光声信号。2）理论上，由于脉冲激光激励的宽带光声多普勒信号的中心频率位移随流速变化不明显，采用时域互相关对速度矢量的各个分量进行测量，建立多探头时域互相关三维速度矢量测量模型。

针对微细血管进行血流速度的实时检测在血液微循环疾病和指（肢）再植的早期诊断、临床治疗和治疗效果的评价中具有重要的意义。基于脉冲回波方式的传统多普勒超声和血管造影在此方面具有一定的局限性，在测量的精度和实时性方面很难达到临床要求。光声多普勒效应（Photoacoustic Doppler, PAD）作为一种新的速度测量方法具有较高的空间分辨率和一定的探测深度，有望成为解决此问题的有效方法。针对此，本项目按照研究计划进行了基于光声多普勒效应的模拟血流速度矢量测量研究，研究计划要点包括：1)建立基于时域相关的速度纵向和横向分量测量理论模型。2)建立基于时域相关的速度矢量测量理论模型。3)光散射介质中的速度矢量测量。4)光散射介质中的深度方向A扫的三维速度矢量测量。该项目研究工作均按计划进行，建立了基于时域自相关的速度纵向和横向分量测量模型、进行了基于时域自相关的速度二维矢量的测量、采用模拟生物组织样品在光散射介质中进行了一定探测深度处的二维速度矢量测量、进行了光散射介质中深度方向A扫的的三维速度矢量测量。所建立的测量理论模型和采用的实验方法对基于脉冲激光的光声多普勒微细血管血流测量具有意义。