Non-Invasive, Depth-Resolved Cerebral Oximeter

In the field of medical monitoring, accurately and continuously assessing the oxygen delivery and consumption status of brain tissue is crucial for postoperative recovery and critical care management. Currently, near-infrared spectroscopy (NIRS) technology, a non-invasive optical imaging technique, can estimate changes in oxyhemoglobin (HbO₂) and deoxyhemoglobin (HbR) concentrations by detecting variations in light intensity and the absorption characteristics of hemoglobin at multiple NIR wavelengths. However, existing NIRS devices are significantly affected by interference from extracranial superficial tissues and are limited to detecting only relative changes in cerebral oxygenation. This limitation hinders its ability to provide accurate and reliable measurements of individual cerebral physiological parameters.

Against this backdrop, a research team led by Dr Chen Nanguang, Senior Principal Investigator from the Biomedical and Health Technology Research Platform of NUSRI Suzhou, has developed a time-domain near-infrared spectroscopy (TD-NIRS) instrument. By bridging optical engineering with clinical needs, this innovation addresses the limitations of conventional cerebral oximetry and offers a safe, reliable, and depth-resolved approach for assessing cerebral tissue oxygen metabolism in critical and postoperative patients.

The TD-NIRS cerebral oximeter is a non-invasive device that employs medically safe, dual-wavelength NIR light (680 nm and 850 nm). Disposable optical fibre probes are placed on the patient’s forehead, allowing light to penetrate the scalp and skull to reach brain tissue, where it continuously monitors cerebral hemodynamics and oxygenation.

While NIR light cannot traverse the entire adult head, the TD-NIRS system positions both the light source and detector on the same side, using a source-detector separation of 2.5 to 4 cm and picosecond temporal resolution to analyse photon absorption and scattering in tissue. Through inverse reconstruction algorithms, the system provides depth-resolved quantification of cerebral oxygenation parameters beneath the superficial cortex, including HbO₂, HbR, and regional cerebral tissue oxygen saturation (StO₂).

TD-NIRS technology enables real-time assessment of tissue perfusion changes following brain injury or intervention, assisting physicians in evaluating patient responses to resuscitation, muscle support, ventilator support, transfusion, and other measures. Continuous monitoring of cerebral oxygen indicators using the TD-NIRS system helps optimise therapeutic targets and provides deeper understanding of individual pathophysiological profiles in patients with hypoxic-ischemic brain injuries. This facilitates early identification of high-risk patients, prevention of secondary injury, and ultimately improves clinical outcomes.