Speaker
Description
Broadband continuous-wave near-infrared spectroscopy (bNIRS) is an effective technique for non-invasive neuromonitoring in neonates. However, most bNIRS devices are based on expensive custom-built spectrometers. The development of low-cost, compact, off-the-shelf spectrometers is critical for widespread clinical adoption. To guide this development, here we determine the minimum spectral resolution needed for accurate estimation of oxy- and deoxy-hemoglobin (HbO and Hb) concentrations in tissue.
Using a spectrometer with variable slit width, we acquired bNIRS measurements from fully oxygenated and deoxygenated tissue-mimicking blood-Intralipid phantoms at 13 slit widths, resulting in data at 13 spectral resolutions (from 0.9 nm to 19.9 nm, mean step size of 1.6 nm). Data for intermediate oxygenation levels were simulated using NIRFAST. HbO and Hb concentrations were estimated from the phantom experiments and the simulations using differential spectral analysis based on the solution to the diffusion equation for a semi-infinite homogeneous medium. The results were compared with the ground truth concentrations.
The concentration of Hb was consistently estimated with high accuracy for resolutions up to 10 nm (10.8 ± 5.4% for phantom experiments and 8.1 ± 7.3% for simulations), whereas HbO estimates were more variable (20.4 ± 16.6% for phantom experiments and 22.9 ± 9.5% for simulations), likely due to cross talk with light scattering. A steady increase in error was observed in the estimation of both Hb and HbO concentrations beyond 10 nm. The results suggest that the minimum spectral resolution for accurate bNIRS tissue oximetry is 10 nm, which is considerably coarser than what is typically reported in the literature (0.3 to 5.5 nm). This implies that a wider slit width may be used to boost light throughput, increasing SNR while decreasing the required integration time for such measurements. Ultimately, this work provides an evidence-based standard for selecting the spectral resolution of off-the-shelf spectrometers for tissue oximetry.
| Keyword-1 | Near-infrared spectroscopy |
|---|---|
| Keyword-2 | Continuous-wave |
| Keyword-3 | Spectral resolution |