Blaney Giles, Sassaroli Angelo, Pham Thao, Krishnamurthy Nishanth, Fantini Sergio
Tufts University, Department of Biomedical Engineering.
Photonics. 2019;6(3). doi: 10.3390/photonics6030083. Epub 2019 Jul 26.
We report non-invasive, bilateral optical measurements on the forehead of five healthy human subjects, of 0.1 Hz oscillatory hemodynamics elicited either by cyclic inflation of pneumatic thigh cuffs, or by paced breathing. Optical intensity and the phase of photon-density waves were collected with frequency-domain near-infrared spectroscopy at seven source-detector distances (11-40 mm). Coherent hemodynamic oscillations are represented by phasors of oxyhemoglobin () and deoxyhemoglobin () concentrations, and by the vector / that represents the amplitude ratio and phase difference of and . We found that, on average, the amplitude ratio (|/|) and the phase difference (∠(/)) obtained with single-distance intensity at 11-40 mm increase from 0.1 and -330°, to 0.2 and -200°, respectively. Single-distance phase and the intensity slope featured a weaker dependence on source-detector separation, and yielded |/| and ∠(/) values of about 0.5 and -200°, respectively, at distances greater than 20 mm. The key findings are: (1) single-distance phase and intensity slope are sensitive to deeper tissue compared to single-distance intensity; (2) deeper tissue hemodynamic oscillations, which more closely represent the brain, feature and phasors that are consistent with a greater relative flow-to-volume contributions in brain tissue compared to extracerebral, superficial tissue.
我们报告了对五名健康人类受试者前额进行的非侵入性双侧光学测量，测量了由气动大腿袖带周期性充气或呼吸起搏引发的0.1Hz振荡血流动力学。在七个源探测器距离（11 - 40毫米）下，使用频域近红外光谱法收集光强度和光子密度波的相位。相干血流动力学振荡由氧合血红蛋白（）和脱氧血红蛋白（）浓度的相量表示，以及由表示和的振幅比和相位差的矢量/表示。我们发现，平均而言，在11 - 40毫米处用单距离强度获得的振幅比（|/|）和相位差（∠（/））分别从0.1和 - 330°增加到0.2和 - 200°。单距离相位和强度斜率对源探测器间距的依赖性较弱，在大于20毫米的距离处分别产生约0.5和 - 200°的|/|和∠（/）值。关键发现是：（1）与单距离强度相比，单距离相位和强度斜率对更深层组织更敏感；（2）更能代表大脑的深层组织血流动力学振荡，其和相量与脑组织中相对于脑外浅表组织更大的相对流量与体积贡献一致。
