Developmental changes in cerebral optical parameters in neonates using near-infrared time-resolved spectroscopy

采用便携式三波长近红外时间分辨光谱（TRS）系统测量脑内光吸收系数（μa）、光还原散射系数（μ s）、血红蛋白（Hb）浓度和血红蛋白氧饱和度（SO2）。在仔猪缺氧模型的基础研究中，研究了脑内差分通路长度因子（DPF）与血红蛋白氧合状态的关系。在一项使用新生儿的临床研究中，研究了这些参数的发育变化。(1)缺氧仔猪模型脑光路长度的TRS测定我们研究了在逐步缺氧负荷条件下，平均光路长度与脑动脉（SaO2）和矢状窦静脉Hb氧饱和度（SvO2）的关系。定义平均光路长度与光电间距离的比值为DPF。在FiO2为0.21时，761,795和835 nm处DPF值分别为5.02±0.36 （mean±SD）、5.31±0.32和4.92±0.34。DPF在761和795 nm处与SaO2呈显著的线性正相关。DPF和SvO2在761和795 nm处也呈显著的正线性相关。影响DPF的因素是缺氧时脱氧血红蛋白升高和脱氧血红蛋白降低。(2)用TRS法测定发育中的脑光学参数、802及脑血容量。研究对象为19例胎龄为25 ~ 41周的新生儿。在761795和835 nm处DPF值分别为4.9±0.52、5.02±0.53和4.64±0.46。各波长的μ s值分别为6.30±1.30、6.04±1.11和6.37±1.45/cm。CBV为2.2±0.6 ml/100g，与文献报道值相近。在95 ~ 100%的SpO2下，SO2为73±4.0%。SO2与产后周呈显著负线性关系。这是因为随着大脑的发育，大脑的耗氧量会增加。

We used a portable three-wavelength near-infrared time-resolved spectroscopy (TRS) system to measure the light absorption coefficient (μa), light reduced scattering coefficient (μ's), hemoglobin (Hb) concentration and Hb oxygen saturation (SO2) in the brain. In a basic study using a piglet hypoxic model, the relationship between differential pathlength factor (DPF) and hemoglobin oxygenation state in the brain was investigated. In a clinical study using neonates, the developmental changes in those parameters were investigated.(1)Measurement of cerebral light pathlength by TRS in a piglet model of hypoxiaWe investigated the relationships of mean light pathlength with arterial (SaO2) and sagittal sinus venous Hb oxygen saturation (SvO2) in the brain under the condition of stepwise hypoxia loading. The ratio of mean light pathlength to interoptode distance is defined as the DPF. At FiO2 of 0.21, the DPF values at 761,795 and 835 nm were estimated to be 5.02±0.36, (mean±SD), 5.31±0.32 and 4.92±0.34,respectively. There was a significant positive linear correlation between DPF at 761 and 795 nm and SaO2. The DPF and SvO2 also showed a significant positive linear correlation at 761 and 795 nm. The factors influencing the DPF were increase in deoxyHb and decrease in oxyHb during hypoxia.(2)Measurement of cerebral optical parameter,802 and cerebral blood volume by TRS in the developing brainThe subjects were 19 neonates whose gestational age was 25 to 41 weeks. The DPF values at 761,795 and 835 nm were estimated to be 4.9±0.52,5.02±0.53 and 4.64±0.46,respectively. The values of μ's at each wavelength were 6.30±1.30,6.04±1.11 and 6.37±1.45/cm respectively. The CBV was 2.2±0.6 ml/100g, which is similar to the value previously reported. The SO2 was 73±4.0% under 95-100% of SpO2. The SO2 and postconceptual weeks showed a significant negative linear relationship. The reason for this is the increase in cerebral oxygen consumption with development of the brain.