Interferometric diffuse correlation spectroscopy improves measurements at long source-detector separation and low photon count rate.
Interferometric diffuse correlation spectroscopy improves measurements at long source-detector separation and low photon count rate.
复制标题
DOI：
10.1117/1.jbo.25.9.097004
复制
发表时间：
2020-09
影响因子：
3.5
通讯作者：
Carp S
中科院分区：
文献类型：
--
作者：
Robinson M;Boas D;Sakadžic S;Franceschini MA;Carp S
意义：漫射相关光谱（DCS）作为一种无创监测组织血流的技术，在神经监测、运动科学和乳腺癌管理方面的应用已经在研究中显示出有效性。DCS解决这些组织血流的能力与测量的光学灵敏度和信噪比（SNR）有关，在某些情况下，特别是成人脑血流测量，在很大一部分人群中是不足的。DCS灵敏度和信噪比的提高可以使该技术在临床上得到更好的应用。目的：对干涉漫射相关光谱（iDCS）进行了表征，并与传统的外差DCS进行了比较，以确定利用外差检测可能带来的好处。方法：采用熔融光纤耦合器对纯差式DCS系统进行改造，形成Mach-Zehnder干涉仪。在两个扩展的源-检测器距离（2.4、3.6 cm）、不同的光子计数率和参考臂功率水平范围内，使用脂内幻像进行了外差和外差检测的比较。对iDCS信号混频特性进行了理论比较。比较了不同测量条件下自相关曲线的扩散系数和信噪比的估计精度。结果：发现外差自相关函数中存在的混合信号与导出的理论一致，从而精确测量了幻影的扩散系数。作为参考臂功率增加的函数，所有测量情况下观察到自相关曲线的信噪比提高高达80%，扩散系数拟合的变异性减少。结论：iDCS有可能改善扩展源检测器分离时组织血流的表征，提高深度灵敏度和信噪比。
Significance: The use of diffuse correlation spectroscopy (DCS) has shown efficacy in research studies as a technique capable of noninvasively monitoring blood flow in tissue with applications in neuromonitoring, exercise science, and breast cancer management. The ability of DCS to resolve blood flow in these tissues is related to the optical sensitivity and signal-to-noise ratio (SNR) of the measurements, which in some cases, particularly adult cerebral blood flow measurements, is inadequate in a significant portion of the population. Improvements to DCS sensitivity and SNR could allow for greater clinical translation of this technique. Aim: Interferometric diffuse correlation spectroscopy (iDCS) was characterized and compared to traditional homodyne DCS to determine possible benefits of utilizing heterodyne detection. Approach: An iDCS system was constructed by modifying a homodyne DCS system with fused fiber couplers to create a Mach–Zehnder interferometer. Comparisons between homodyne and heterodyne detection were performed using an intralipid phantom characterized at two extended source–detector separations (2.4, 3.6 cm), different photon count rates, and a range of reference arm power levels. Characterization of the iDCS signal mixing was compared to theory. Precision of the estimation of the diffusion coefficient and SNR of the autocorrelation curve were compared between different measurement conditions that mimicked what would be seen in vivo. Results: The mixture of signals present in the heterodyne autocorrelation function was found to agree with the derived theory and resulted in accurate measurement of the diffusion coefficient of the phantom. Improvement of the SNR of the autocorrelation curve up to and up to 80% reduction in the variability of the diffusion coefficient fit were observed for all measurement cases as a function of increased reference arm power. Conclusions: iDCS has the potential to improve characterization of blood flow in tissue at extended source–detector separations, enhancing depth sensitivity and SNR.