Speaker
Description
Hyperspectral time-resolved (hTR) near-infrared spectroscopy (NIRS) is an advanced analytical technique that provides high-resolution spectral measurements across hundreds of wavelengths, offering improved depth sensitivity compared to conventional continuous-wave (CW) systems. In clinical settings, this technique could enable real-time identification of adverse changes in cerebral blood oxygenation and metabolism; however, designing a system for in-vivo monitoring is challenging due to trade-offs between spectral range, spectral resolution, and acquisition time. We have pioneered an approach that harnesses compressive sensing and highly parallelized time-correlated single-photon counting (TCSPC) to reduce the acquisition time for a 256-point TR spectrum to <6 seconds. Here, we assess the depth sensitivity of our device in phantoms and present in-vivo results tracking the cerebral hemodynamic response to a hypercapnia challenge in healthy adult humans.
The hTR-NIRS device pairs an illumination architecture that implements the compressive sensing acquisition scheme and a SPAD array with 64 TCSPC-enabled pixels for detection. Two-layer tissue-mimicking phantom experiments were performed, where the top layer (10-mm-thick) remained static while the bottom layer’s blood oxygenation and metabolism were altered. hTR-NIRS probes were placed on the surface of the top layer, while CW-NIRS probes were placed on both the top and bottom layers for validation. A hypercapnia challenge (10 mmHg above normocapnia for 6 minutes) was performed with 5 healthy adults using a computer-controlled gas delivery circuit, with hTR and CW-NIRS probes fixed to the left side of each subject’s forehead. The phantom results demonstrate that hTR-NIRS reduces surface contamination by more than 50% compared to CW-NIRS and can successfully track changes in blood oxygenation and metabolism beneath a 10-mm-thick static top layer. The in-vivo results validate the capability of our system to track the dynamic cerebral hemodynamic response typical of hypercapnia. Future work will increase the sample size and monitor cerebral metabolism changes in-vivo during functional activation.
| Keyword-1 | Near-infrared spectroscopy |
|---|---|
| Keyword-2 | Time-resolved |
| Keyword-3 | Neuromonitoring |