Optimization of time domain diffuse correlation spectroscopy parameters for measuring brain blood flow.
Optimization of time domain diffuse correlation spectroscopy parameters for measuring brain blood flow.
复制标题
DOI：
10.1117/1.nph.8.3.035005
复制
发表时间：
2021-07
期刊：
影响因子：
5.3
通讯作者：
Carp SA
中科院分区：
文献类型：
--
作者：
Mazumder D;Wu MM;Ozana N;Tamborini D;Franceschini MA;Carp SA
意义：通过根据光子在组织中的传播时间区分光子，时域漫相关光谱(TD-DCS)可以提高对脑血流动力学的敏感性，并减少来自脑外各层的污染。我们开发了严格的模拟和评估程序，以确定监测脑血流灌注的最佳时间门参数，考虑到仪器特性和实际测量噪声。目的：模拟在实际实验噪声存在的情况下，不同仪器响应函数(IRF)的TD-DCS脑血流监测性能，并评估其对脑血流的灵敏度、信噪比(SNR)和抵抗不同时间门外血流的影响的能力，以确定最佳操作参数。方法：采用蒙特卡罗模拟方法，对765 nm和1064 nm激发波长的光传播进行模拟，模拟的是MRI衍生的人头几何形状。我们使用一个虚拟探测器，源-探测器间距为1厘米，放置在前额叶区域。对上述性能度量进行了评估，以确定不同IRF的最佳时间门(S)。模拟噪声估计的验证是通过在基于脂肪内的液体体模上进行的实验完成的。结果：我们发现TD-DCS的性能强烈地依赖于系统的IRF。在高斯脉冲形状中，脉冲长度似乎提供了最好的性能，在宽门(500fps或更大)下，在765和1064nmTPSF峰值后的开始时间分别为400kcps和600mcps，在实验中看到的光子检测速率下的1-S积分时间(765kcps为600kcps和1064nm处为4mcps)。结论：我们的工作表明，最优时间门满足了对足够灵敏度和足够信噪比的相互竞争的要求。可实现的性能进一步受到系统IRF的影响，其中使用电光激光整形获得的准高斯脉冲提供了最好的结果。
Significance: Time domain diffuse correlation spectroscopy (TD-DCS) can offer increased sensitivity to cerebral hemodynamics and reduced contamination from extracerebral layers by differentiating photons based on their travel time in tissue. We have developed rigorous simulation and evaluation procedures to determine the optimal time gate parameters for monitoring cerebral perfusion considering instrumentation characteristics and realistic measurement noise. Aim: We simulate TD-DCS cerebral perfusion monitoring performance for different instrument response functions (IRFs) in the presence of realistic experimental noise and evaluate metrics of sensitivity to brain blood flow, signal-to-noise ratio (SNR), and ability to reject the influence of extracerebral blood flow across a variety of time gates to determine optimal operating parameters. Approach: Light propagation was modeled on an MRI-derived human head geometry using Monte Carlo simulations for 765- and 1064-nm excitation wavelengths. We use a virtual probe with a source–detector separation of 1 cm placed in the pre-frontal region. Performance metrics described above were evaluated to determine optimal time gate(s) for different IRFs. Validation of simulation noise estimates was done with experiments conducted on an intralipid-based liquid phantom. Results: We find that TD-DCS performance strongly depends on the system IRF. Among Gaussian pulse shapes, pulse length appears to offer the best performance, at wide gates (500 ps and larger) with start times 400 and 600 ps after the peak of the TPSF at 765 and 1064 nm, respectively, for a 1-s integration time at photon detection rates seen experimentally (600 kcps at 765 nm and 4 Mcps at 1064 nm). Conclusions: Our work shows that optimal time gates satisfy competing requirements for sufficient sensitivity and sufficient SNR. The achievable performance is further impacted by system IRF with quasi-Gaussian pulse obtained using electro-optic laser shaping providing the best results.