A research team from the University of Glasgow in the UK has made a major breakthrough: for the first time, they have successfully detected light signals penetrating the complete skull of an adult.This latest research, published in the journal Neurophotonics, breaks through the depth limitations of existing optical brain imaging technology and is expected to lead to new devices that can detect deeper brain tissue.
Near-infrared spectroscopy (fNIRS) has been used for decades as a non-invasive means of detecting brain function. The principle is to indirectly reflect neural activity by analyzing changes in the absorption of near-infrared light of specific wavelengths by cerebral blood flow.
Although it has the advantages of portability and low cost, traditional fNIRS has significant limitations: the light can only penetrate to a depth of about 4 centimeters on the surface of the brain, making it difficult to reach deep brain areas closely related to memory, emotion regulation, motor functions, etc. This has led to a technical bottleneck in deep brain tissue research without relying on expensive and bulky magnetic resonance imaging (MRI) equipment.
To overcome this problem, the research team designed an innovative experimental plan: using a high-power pulsed laser as the light source, coupled with an ultra-high-sensitivity single-photon detector, and conducting measurements under conditions that strictly shielded from ambient light.Eventually, they managed to record faint light signals that entered from one side of the head, penetrated the entire skull, and exited from the other side.
To ensure the reliability of the results, the team not only conducted precise human skull penetration experiments, but also used computer simulation technology to completely reconstruct the propagation path of light in the multi-layered structures of the skull (such as scalp, skull, cerebrospinal fluid, and brain tissue). The simulation results are highly consistent with the experimental data and reveal an important phenomenon: when photons pass through complex brain tissue, they preferentially propagate along structures with lower scattering coefficients such as cerebrospinal fluid.
Although the current technology still has limitations - a single detection process takes about 30 minutes, and the subjects need to be light-skinned and have no hair areas - this proof-of-principle study provides a new design idea and physical basis for the development of next-generation fNIRS systems.
The research team predicts that with the continuous iterative optimization of light sources, detectors and related algorithms, this penetrating optical detection method is expected to develop into a portable and economical deep brain imaging solution.In the future, this technology may be applied to bedside or on-site rapid diagnosis of stroke, brain trauma, brain tumors and other diseases, especially in special scenarios where large MRI equipment cannot be used (such as field medical treatment and resource-poor areas).
