Researchers from the University of Birmingham in the UK and Washington University School of Medicine have developed a new non-invasive brain imaging method for studying the shape of the brain’s surface and oxygenation of brain tissues. Their discovery enables deeper brain imaging with higher resolution than prior studies with similar capabilities. This exciting development can one day improve brain mapping, ICU patient monitoring, and early diagnosis of a number of neurological conditions.
Functional neuroimaging provides valuable medical information about the health and condition of brain tissue. Functional near-infrared spectroscopy (fNIRS) is a non-invasive inexpensive technology that has been valuable in the clinic, using the interactions of near-infrared light with brain tissue to identify the brain surface and measure oxygenation. Current approaches use continuous wave (CW) near-infrared light, based on light attenuation, which provides images of limited depth and resolution. To improve on this, the researchers studied and tested the potential of a new optical imaging system to measure changes in the phase and intensity of light, providing more information than existing approaches that rely on only light attenuation.
The technology relies on 32 light sources and 30 light receivers that are placed around the skull of a patient. The sources emit light at 690 and 830 nanometers at various intensities, but in a controlled manner. The light enters the brain tissue, gets scattered, absorbed, and reflected, and the receiver modules measure the phase and intensity of light that reaches them. The different wavelengths of near-infrared light are used in order to provide oxygenation information, since those specific wavelengths have different levels of absorption by oxygenated hemoglobin.
The researchers provided theoretical calculations and simulations that describe the advantage of their approach compared to prior work. They also performed an in-vivo test with a single human patient. The patient was presented with a visual stimulus and tested with the new fNIRS device, and then with the continuous wave fNIRS device. They observed high quality oxygen signals coming from the visual cortex, demonstrating the new fNIRS device can visualize oxygen concentrations and provide valuable information about activation. Further analysis of the in-vivo results showed that the new device outperformed the prior technology in resolution and in imaging depth.
According to Rickson Mesquita, Associate Editor editor of journal Neurophotonics, who is at the University of Campesinas’ Institute of Physics in Sao Paolo, Brazil, the findings mark exciting new possibilities in the fNIRS arena: “I believe this manuscript can be significant from the methods perspective … Importantly, their simulations and data appear to show that, by adding the phase information from the FD data, the depth sensitivity is greatly improved. The results are carefully addressed, and the authors’ conclusions are of great interest to the fNIRS community.”