# Evaluation of Probe Positioning Effects on Optical Parameters in Neonatal Forehead Time-Resolved Spectroscopy Measurements

## TL;DR

This study finds that midline forehead positioning provides more stable optical data for neonatal brain monitoring using time-resolved spectroscopy.

## Contribution

The study identifies optimal probe positioning for consistent optical parameter measurements in neonatal TRS.

## Key findings

- Midline forehead positioning yields more stable scattering and optical path data compared to lateral sites.
- Lateral sites show lower scattering coefficients and shorter mean path lengths.
- tHb, ScO2, and CBV values remain consistent between midline and lateral probe positions.

## Abstract

Time-resolved spectroscopy (TRS) is a promising tool for noninvasive cerebral monitoring in neonates. However, the optimal forehead site for probe placement remains unclear. In this study, we evaluated the effect of probe positioning on TRS-derived optical parameters in neonates. TRS measurements were obtained from the midline and right lateral forehead of 30 neonates (≥36 weeks’ corrected gestational age). We compared various parameters between the two probe positions, including optical intensity, attenuation, mean optical path length, scattering coefficient, total hemoglobin (tHb), cerebral oxygen saturation (ScO2) and cerebral blood volume (CBV). No significant differences were observed in tHb, ScO2 and CBV between the midline and lateral sites. However, the lateral site showed a significantly lower scattering coefficient and shorter mean path length. Light intensity was increased and attenuation was reduced at the lateral site. Thus, while tHb, ScO2 and CBV values were consistent between sites, the midline provided more stable scattering and optical path data. These findings suggest that the midline forehead may be a more suitable site for TRS-based neonatal cerebral monitoring.