Infrared light scattering methods have been developed and employed to non-invasively monitor human cerebral blood flow (CBF). However, the number of reflected photons that interact with the brain is low when detecting blood flow in deep tissue. To tackle this photon-starved problem, we present and demonstrate the idea of interferometric speckle visibility spectroscopy (ISVS). In ISVS, an interferometric detection scheme is used to boost the weak signal light. The blood flow dynamics are inferred from the speckle statistics of a single frame speckle pattern. We experimentally demonstrated the improvement in the measurement of fidelity by introducing interferometric detection when the signal photon number is low. We apply the ISVS system to monitor the human CBF in situations where the light intensity is ∼100-fold less than that in common diffuse correlation spectroscopy (DCS) implementations. Due to the large number of pixels (∼2 × 10⁵) used to capture light in the ISVS system, we are able to collect a similar number of photons within one exposure time as in normal DCS implementations. Our system operates at a sampling rate of 100 Hz. At the exposure time of 2 ms, the average signal photoelectron number is ∼0.95 count/pixel, yielding a single pixel interferometric measurement signal-to-noise ratio (SNR) of ∼0.97. The total ∼2 × 10⁵ pixels provide an expected overall SNR of 436. We successfully demonstrate that the ISVS system is able to monitor the human brain pulsatile blood flow, as well as the blood flow change when a human subject is doing a breath-holding task.

中文翻译：

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干涉斑点可见度光谱法（ISVS）用于人脑血流监测

已经开发了红外光散射方法，并将其用于非侵入性地监视人脑血流（CBF）。但是，当检测深层组织中的血流时，与大脑相互作用的反射光子数量很少。为了解决这个光子匮乏的问题，我们提出并演示了干涉光斑可见度光谱学（ISVS）的思想。在ISVS中，干涉检测方案用于增强弱信号光。从单帧散斑图案的散斑统计推断血流动力学。我们通过在信号光子数较低时引入干涉检测来实验性地证明了保真度测量的改进。我们将ISVS系统用于在光强度比普通漫射相关光谱法（DCS）实现的强度低约100倍的情况下监视人体CBF的情况。由于像素数量众多（〜2×10⁵）用于在ISVS系统中捕获光，我们能够在一个曝光时间内收集与普通DCS实施方案中类似数量的光子。我们的系统以100 Hz的采样率运行。在2 ms的曝光时间，平均信号光电子数约为0.95个计数/像素，从而产生约0.97的单像素干涉测量信噪比（SNR）。总共约2×10 ⁵像素可提供436的预期整体SNR。我们成功地证明了ISVS系统能够监视人脑搏动的血流以及人类进行呼吸时的血流变化。保持任务。