Non-invasive optical monitoring of the newborn piglet brain using continuous-wave and frequency-domain spectroscopy

Abstract

Abstract.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 μM 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.

Effect of age on brain oxygenation regulation during changes in position

“…SO 2 was calculated as SO 2 = OHb/(OHb ± HHb) and tHb = OHb + HHb (Gratton et al, 1997). The FD-NIRS monitor utilized multidistance technique and modulated near-infrared light to determine hemoglobin content in brain tissue ( mol/L) (Fantini et al, 1999). Each diode emitted light at wavelengths of 690 or 830 nm.…”

Comparison of a layered slab and an atlas head model for Monte Carlo fitting of time-domain near-infrared spectroscopy data of the adult head

“…[6][7][8][9][10][11][12][13][14] We focused this study on evaluating the method for TD-NIRS data, in comparison with the traditional homogeneous model. Comparing the performance of this approach for different NIRS modalities (CW, FD, and TD), incorporating realistic noise characteristic for each technology, will require further studies beyond the scope of the present manuscript.…”

“…Various continuous-wave (CW), [1][2][3][4][5] frequency-domain (FD), [6][7][8][9][10][11][12][13][14] and time-domain (TD) [15][16][17][18][19] near-infrared spectroscopy (NIRS) approaches offer the ability to determine the absolute absorption and scattering coefficients of biological tissue. The retrieved optical absorption measured at multiple wavelengths allows quantification of different chromophores' concentrations within the tissue.…”

“…The frequency-domain multidistance (FDMD) approach based on a homogeneous model 6 has been extensively validated with Monte Carlo simulations, 14 phantoms, 6,12 and animal models. 11,13 It has been successfully applied to the monitoring of brain oxygenation and metabolism in healthy and brain-injured infants. 8,9,20 Time-resolved approaches are generally based on the nonlinear fit of temporal point spread functions (TPSFs).…”

Regional Differences of Hemodynamics and Oxygenation in the Human Calf Muscle Detected with Near-Infrared Spectrophotometry

“…Data Analysis.-The absolute values for absorption, scattering, and DPF were calculated (29,31) in three center regions according to the sensor (Fig 1) and the frequency-domain equations. Quantitative values for relative changes in oxyhemoglobin and deoxyhemoglobin in all 22 locations were obtained by combining the attenuation changes with the DPF data (32).…”