Laser speckle contrast imaging (LSCI) is a powerful tool to monitor blood flow distribution and has been widely used in studies of microcirculation, both for animal and clinical applications. Conventionally, LSCI usually works on reflective-detected mode. However, it could provide promising temporal and spatial resolution for in vivo applications only with the assistance of various tissue windows, otherwise, the overlarge superficial static speckle would extremely limit its contrast and resolution. Here, we systematically investigated the capability of transmissive-detected LSCI (TR-LSCI) for blood flow monitoring in thick tissue. Using Monte Carlo simulation, we theoretically compared the performance of transmissive and reflective detection. It was found that the reflective-detected mode was better when the target layer was at the very surface, but the imaging quality would rapidly decrease with imaging depth, while the transmissive-detected mode could obtain a much stronger signal-to-background ratio (SBR) for thick tissue. We further proved by tissue phantom, animal, and human experiments that in a certain thickness of tissue, TR-LSCI showed remarkably better performance for thick-tissue imaging, and the imaging quality would be further improved if the use of longer wavelengths of near-infrared light. Therefore, both theoretical and experimental results demonstrate that TR-LSCI is capable of obtaining thick-tissue blood flow information and holds great potential in the field of microcirculation research.

激光散斑对比成像 (LSCI) 是监测血流分布的强大工具，已广泛用于动物和临床应用的微循环研究。通常，LSCI 通常在反射检测模式下工作。然而，只有在各种组织窗口的帮助下，它才能为体内应用提供有前途的时间和空间分辨率，否则，过大的表面静态散斑将极大地限制其对比度和分辨率。在这里，我们系统地研究了透射检测 LSCI (TR-LSCI) 在厚组织中监测血流的能力。使用蒙特卡罗模拟，我们从理论上比较了透射和反射检测的性能。结果发现，当目标层位于最表面时，反射检测模式更好，但成像质量会随着成像深度的增加而迅速下降，而透射检测模式可以获得更强的厚组织信背景比（SBR）。我们通过组织体模、动物和人体实验进一步证明，在一定厚度的组织中，TR-LSCI对厚组织成像表现出明显更好的性能，如果使用更长波长的近-红外线。因此，理论和实验结果均表明，TR-LSCI能够获取厚组织血流信息，在微循环研究领域具有巨大潜力。我们通过组织体模、动物和人体实验进一步证明，在一定厚度的组织中，TR-LSCI对厚组织成像表现出明显更好的性能，如果使用更长波长的近-红外线。因此，理论和实验结果均表明，TR-LSCI能够获取厚组织血流信息，在微循环研究领域具有巨大潜力。我们通过组织体模、动物和人体实验进一步证明，在一定厚度的组织中，TR-LSCI对厚组织成像表现出明显更好的性能，如果使用更长波长的近-红外线。因此，理论和实验结果均表明，TR-LSCI能够获取厚组织血流信息，在微循环研究领域具有巨大潜力。