A revamped optical brain-monitoring method has achieved a 20-fold boost in signal quality, bringing noninvasive measurements of cerebral blood flow closer to routine clinical use.
Researchers refined interferometric diffusing wave spectroscopy (iDWS), a technique that tracks subtle fluctuations in scattered laser light caused by moving blood cells. By coherently amplifying weak light returning from the brain with a stronger reference beam, the system can extract signals from deeper tissue layers.
The team optimized multiple parameters – including detector performance, laser power, noise filtering, and data processing – resulting in a dramatic improvement in signal-to-noise ratio. This enabled reliable detection of pulsatile cerebral blood flow at source–detector separations of up to 4–4.5 cm in adults, pushing beyond the limits of conventional diffuse correlation spectroscopy.
Crucially, the system uses a relatively inexpensive CMOS sensor rather than costly photon-counting arrays, potentially reducing hardware costs by two orders of magnitude. The researchers also engineered a compact, cart-based setup that remains stable without bulky vibration-isolated tables, allowing bedside deployment.
“Our novel iDWS approach involves boosting of the weak optical field returning from the brain by coherent amplification with a stronger reference field. In this way, interferometry enables a non-scientific complementary-metal-oxide-semiconductor sensor to parallelize measurements of weak coherent light fluctuations,” said lead author Mingjun Zhao in a press release.
Early tests in a neuro intensive care unit demonstrated real-time monitoring of blood flow in a patient, highlighting the technique’s clinical promise. With further validation, iDWS could support diagnosis and monitoring of conditions such as stroke and traumatic brain injury.
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