Fantini S, Hueber D, Franceschini M A, Gratton E, Rosenfeld W, Stubblefield P G, Maulik D, Stankovic M R
Department of Physics, University of Illinois at Urbana-Champaign, Urbana 61801-3080, USA.
Phys Med Biol. 1999 Jun;44(6):1543-63. doi: 10.1088/0031-9155/44/6/308.
We have used continuous-wave (CW) and frequency-domain spectroscopy to investigate the optical properties of the newborn piglet brain in vivo and non-invasively. Three anaesthetized, intubated, ventilated and instrumented newborn piglets were placed into a stereotaxic instrument for optimal experimental stability, reproducible probe-to-scalp optical contact and 3D adjustment of the optical probe. By measuring the absolute values of the brain absorption and reduced scattering coefficients at two wavelengths (758 and 830 nm), frequency-domain spectroscopy provided absolute readings (in contrast to the relative readings of CW spectroscopy) of cerebral haemoglobin concentration and saturation during experimentally induced perturbations in cerebral haemodynamics and oxygenation. Such perturbations included a modulation of the inspired oxygen concentration, transient brain asphyxia, carotid artery occlusion and terminal brain asphyxia. The baseline cerebral haemoglobin saturation and concentration, measured with frequency-domain spectroscopy, were about 60% and 42 microM respectively. The cerebral saturation values ranged from a minimum of 17% (during transient brain asphyxia) to a maximum of 80% (during recovery from transient brain asphyxia). To analyse the CW optical data, we have (a) derived a mathematical relationship between the cerebral optical properties and the differential pathlength factor and (b) introduced a method based on the spatial dependence of the detected intensity (dc slope method). The analysis of the cerebral optical signals associated with the arterial pulse and with respiration demonstrates that motion artefacts can significantly affect the intensity recorded from a single optode pair. Motion artefacts can be strongly reduced by combining data from multiple optodes to provide relative readings in the dc slope method. We also report significant biphasic changes (initial decrease and successive increase) in the reduced scattering coefficient measured in the brain after the piglet had been sacrificed.
我们使用连续波（CW）和频域光谱技术，对新生仔猪的活体大脑进行了非侵入性光学特性研究。将三只麻醉、插管、通气并配备仪器的新生仔猪放入立体定位仪中，以实现最佳实验稳定性、可重复的探头与头皮光学接触以及光学探头的三维调整。通过测量两个波长（758和830纳米）下大脑吸收系数和约化散射系数的绝对值，频域光谱技术在实验诱导的脑血流动力学和氧合扰动期间，提供了脑血红蛋白浓度和饱和度的绝对读数（与CW光谱的相对读数形成对比）。此类扰动包括吸入氧浓度的调节、短暂性脑窒息、颈动脉闭塞和终末期脑窒息。频域光谱技术测得的基线脑血红蛋白饱和度和浓度分别约为60%和42微摩尔。脑饱和度值范围从最低的17%（短暂性脑窒息期间）到最高的80%（短暂性脑窒息恢复期间）。为了分析CW光学数据，我们（a）推导了脑光学特性与微分程长因子之间的数学关系，以及（b）引入了一种基于检测强度空间依赖性的方法（直流斜率法）。对与动脉搏动和呼吸相关的脑光学信号分析表明，运动伪影会显著影响从单个光电极对记录的强度。通过组合来自多个光电极的数据以在直流斜率法中提供相对读数，可大幅减少运动伪影。我们还报告了在仔猪处死后，大脑中测得的约化散射系数出现显著的双相变化（初始下降和随后上升）。
