Measurement of Optical Path Length for Cerebral Near-Infrared Spectroscopy in Newborn Infants

Abstract

The time taken for an extremely short pulse of near-infrared laser light to traverse the heads of 6 preterm infants was measured after death. The values obtained were used to calculate a differential path length factor (DPF), defined as the mean distance travelled by the photons divided by the distance between the points where light entered and left the head. The DPF was found to be 4.39 ± 0.28. Knowledge of this factor will permit accurate quantitative measurements to be made by near-infrared spectroscopy of a range of indices of cerebral oxygenation and haemodynamics in live infants.

Neonatal hemodynamic response to visual cortex activity: high-density near-infrared spectroscopy study

“…Our results are comparable to those from a recent study published by Karen et al, 30 in which they found a mean 31 which used whole-head time-offlight measurements taken up to three days postmortem from premature infants who died of intraventricular hemorrhage. In our study, we elected to use the DPF formulas reported by Duncan et al, 28 as they used both living infants and had a reflectance measurement geometry similar to our own.…”

Neonatal hemodynamic response to visual cortex activity: high-density near-infrared spectroscopy study

“…Our results are comparable to those from a recent study published by Karen et al, 30 in which they found a mean 31 which used whole-head time-offlight measurements taken up to three days postmortem from premature infants who died of intraventricular hemorrhage. In our study, we elected to use the DPF formulas reported by Duncan et al, 28 as they used both living infants and had a reflectance measurement geometry similar to our own.…”

Progress of near-infrared spectroscopy and topography for brain and muscle clinical applications

“…To obtain quantitative values, the DPF, which accounts for the increased pathlength due to light scattering, has to be measured or taken from the literature. [54][55][56][57][58][59] The diffusion approximation of the Boltzmann transport equation is another widely used mathematical model. The diffusion approximation has analytical solutions under the following assumptions: ͑1͒ tissue is homogeneous, ͑2͒ scattering is much larger than absorption, and ͑3͒ the tissue has a specific geometry-infinite, semi-infinite, slab, or two-layered.…”

Cerebral oxygenation and echocardiographic parameters in preterm neonates with a patent ductus arteriosus: an observational study

“…Although it should be noted that NIRS determined rScO 2 can be merely used as a trend monitoring parameter to assess changes in cerebral oxygenation and not as a quantitative measurement. It estimates changes in oxygenation with an assumption of path length of the near-infrared light bundle 26 27. Assessment of cerebral oxygenation over time can alert the clinician to a (developing) hsPDA.…”

Neonatal hemodynamic response to visual cortex activity: high-density near-infrared spectroscopy study

“…Our results are comparable to those from a recent study published by Karen et al, 30 in which they found a mean 31 which used whole-head time-offlight measurements taken up to three days postmortem from premature infants who died of intraventricular hemorrhage. In our study, we elected to use the DPF formulas reported by Duncan et al, 28 as they used both living infants and had a reflectance measurement geometry similar to our own.…”

Progress of near-infrared spectroscopy and topography for brain and muscle clinical applications

“…To obtain quantitative values, the DPF, which accounts for the increased pathlength due to light scattering, has to be measured or taken from the literature. [54][55][56][57][58][59] The diffusion approximation of the Boltzmann transport equation is another widely used mathematical model. The diffusion approximation has analytical solutions under the following assumptions: ͑1͒ tissue is homogeneous, ͑2͒ scattering is much larger than absorption, and ͑3͒ the tissue has a specific geometry-infinite, semi-infinite, slab, or two-layered.…”

Cerebral oxygenation and echocardiographic parameters in preterm neonates with a patent ductus arteriosus: an observational study

“…Although it should be noted that NIRS determined rScO 2 can be merely used as a trend monitoring parameter to assess changes in cerebral oxygenation and not as a quantitative measurement. It estimates changes in oxygenation with an assumption of path length of the near-infrared light bundle 26 27. Assessment of cerebral oxygenation over time can alert the clinician to a (developing) hsPDA.…”

Neonatal hemodynamic response to visual cortex activity: high-density near-infrared spectroscopy study

“…Our results are comparable to those from a recent study published by Karen et al, 30 in which they found a mean 31 which used whole-head time-offlight measurements taken up to three days postmortem from premature infants who died of intraventricular hemorrhage. In our study, we elected to use the DPF formulas reported by Duncan et al, 28 as they used both living infants and had a reflectance measurement geometry similar to our own.…”

Progress of near-infrared spectroscopy and topography for brain and muscle clinical applications

“…To obtain quantitative values, the DPF, which accounts for the increased pathlength due to light scattering, has to be measured or taken from the literature. [54][55][56][57][58][59] The diffusion approximation of the Boltzmann transport equation is another widely used mathematical model. The diffusion approximation has analytical solutions under the following assumptions: ͑1͒ tissue is homogeneous, ͑2͒ scattering is much larger than absorption, and ͑3͒ the tissue has a specific geometry-infinite, semi-infinite, slab, or two-layered.…”

Cerebral oxygenation and echocardiographic parameters in preterm neonates with a patent ductus arteriosus: an observational study

“…Although it should be noted that NIRS determined rScO 2 can be merely used as a trend monitoring parameter to assess changes in cerebral oxygenation and not as a quantitative measurement. It estimates changes in oxygenation with an assumption of path length of the near-infrared light bundle 26 27. Assessment of cerebral oxygenation over time can alert the clinician to a (developing) hsPDA.…”