Acoustic resolution photoacoustic Doppler velocimetry in blood-mimicking fluids.
Acoustic resolution photoacoustic Doppler velocimetry in blood-mimicking fluids.
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DOI：
10.1038/srep20902
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发表时间：
2016-02-19
影响因子：
4.6
通讯作者：
Beard P
中科院分区：
文献类型：
--
作者：
Brunker J;Beard P
光声多普勒测速仪提供了一个重要的机会，以克服现有的血流测量方法的局限性。通过在几毫米深的组织中进行高空间分辨率的测量，它可以探测许多不同疾病的微血管血流异常特征。虽然以前的工作已经证明了在固体幻影的可行性，在血液中的测量已被证明更具挑战性。这种困难通常归因于要求吸收体的空间分布相对于最小可检测声波波长是不均匀的。通过使用3 μm吸收微球的血液模拟流体悬浮液进行严格的研究，发现感知的异质性不仅受到固有探测器带宽的限制;此外，由于探测器视场内的空间平均而导致的带宽限制也降低了感知的异质性并损害了速度测量精度。发现这些有害影响通过高通滤波以选择与高异质性相关联的光声信号分量来减轻。还观察到由于有限的光穿透到流动容器中而导致的测量读数不足。准确的平均速度测量恢复使用“范围选通”，它进一步映射的横截面速度分布。这些见解可能有助于为使用光声方法进行微血管血流的深层组织非侵入性映射铺平道路。
Photoacoustic Doppler velocimetry provides a major opportunity to overcome limitations of existing blood flow measuring methods. By enabling measurements with high spatial resolution several millimetres deep in tissue, it could probe microvascular blood flow abnormalities characteristic of many different diseases. Although previous work has demonstrated feasibility in solid phantoms, measurements in blood have proved significantly more challenging. This difficulty is commonly attributed to the requirement that the absorber spatial distribution is heterogeneous relative to the minimum detectable acoustic wavelength. By undertaking a rigorous study using blood-mimicking fluid suspensions of 3 μm absorbing microspheres, it was discovered that the perceived heterogeneity is not only limited by the intrinsic detector bandwidth; in addition, bandlimiting due to spatial averaging within the detector field-of-view also reduces perceived heterogeneity and compromises velocity measurement accuracy. These detrimental effects were found to be mitigated by high-pass filtering to select photoacoustic signal components associated with high heterogeneity. Measurement under-reading due to limited light penetration into the flow vessel was also observed. Accurate average velocity measurements were recovered using “range-gating”, which furthermore maps the cross-sectional velocity profile. These insights may help pave the way to deep-tissue non-invasive mapping of microvascular blood flow using photoacoustic methods.