Institute of Complementary Medicine, University of Bern, Bern, Switzerland.
Department of Neonatology, Biomedical Optics Research Laboratory, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
Adv Exp Med Biol. 2018;1072:331-337. doi: 10.1007/978-3-319-91287-5_53.
Frequency-domain near-infrared spectroscopy (FD-NIRS) enables to measure absolute optical properties (i.e. the absorption coefficient, μ, and the reduced scattering coefficient, [Formula: see text]) of the brain tissue. The aim of this study was to investigate how the optical properties changed during the course of a functional NIRS experiment. The analyzed dataset comprised of FD-NIRS measurements of 14 healthy subjects (9 males, 5 females, aged: 33.4 ± 10.5 years, range: 24-57 years old). Each measurement lasted 33 min, i.e. 8 min baseline in darkness, 10 min intermittent light stimulation, and 15 min recovery in darkness. Optical tissue properties were obtained bilaterally over the prefrontal cortex (PFC) and visual cortex (VC) with FD-NIRS (Imagent, ISS Inc., USA). Changes in μ and [Formula: see text] were directly measured and two parameters were calculated, i.e. the differential pathlength factor (DPF) and the effective attenuation coefficient (μ). Differences in the behavior of the optical changes were observed when comparing group-averaged data versus single datasets: no clear overall trend was presented in the group data, whereas a clear long-term trend was visible in almost all of the single measurements. Interestingly, the changes in [Formula: see text] statistically significantly correlated with μ, positively in the PFC and negatively in the VC. Our analysis demonstrates that all optical brain tissue properties (μ, [Formula: see text], μ and DPF) change during these functional neuroimaging experiments. The change in [Formula: see text] is not random but follows a trend, which depends on the single experiment and measurement location. The change in the scattering properties of the brain tissue during a functional experiment is not negligible. The assumption [Formula: see text] ≈ const during an experiment is valid for group-averaged data but not for data from single experiments.
频域近红外光谱（FD-NIRS）可用于测量脑组织结构的绝对光学特性（即吸收系数μ和散射系数[Formula: see text]）。本研究旨在探讨在功能近红外光谱实验过程中光学特性如何发生变化。分析数据集包含 14 名健康受试者（9 名男性，5 名女性，年龄：33.4±10.5 岁，范围：24-57 岁）的 FD-NIRS 测量结果。每次测量持续 33 分钟，即 8 分钟黑暗基线，10 分钟间歇性光刺激，15 分钟黑暗恢复。FD-NIRS（美国 ISS 公司的 Imagent）在额皮质（PFC）和视觉皮质（VC）双侧获取光学组织特性。直接测量μ和[Formula: see text]的变化，并计算两个参数，即差分路径长度因子（DPF）和有效衰减系数（μ）。当比较组平均数据与单个数据集时，观察到光学变化的行为存在差异：组数据没有呈现出清晰的整体趋势，而几乎所有的单个测量都显示出明显的长期趋势。有趣的是，[Formula: see text]的变化与μ呈正相关（在 PFC 中）和负相关（在 VC 中）。我们的分析表明，在这些功能神经影像学实验中，所有的光学脑组织特性（μ、[Formula: see text]、μ和 DPF）都会发生变化。[Formula: see text]的变化不是随机的，而是遵循一种趋势，这种趋势取决于单个实验和测量位置。在功能实验中，脑组织的散射特性变化不容忽视。在实验过程中，假设[Formula: see text]≈const 对于组平均数据是有效的，但不适用于单个实验的数据。
