Optical Technology Advances Non-Invasive Functional Imaging of the Human Brain

Illustration of the optical blood flow measurements for quantifying resting state functional connectivity.

By: Biophotonics.World Team

Health

A team of researchers at Wright State University has demonstrated for the first time that optical blood flow contrast measured by Diffuse Correlation Spectroscopy (DCS) can be used to detect Resting State Functional Connectivity (RSFC) in the human brain. RSFC indicates spontaneous activity of the resting brain showing high synchronization in functionally related regions, adjacent or even remote regions. These in sync regions are known as “networks”. This phenomena was first uncovered by a functional magnetic resonance imaging (fMRI) study using blood-oxygen-level dependent (BOLD) signals that indicates oxygenation levels of the cerebral blood. Abnormalities in RSFC have been associated with neuronal disorders such as autism, Alzheimer’s, and depression. Thus, RSFC studies represent a valuable tool for studying patients with disorders that can make performance of task-based assessments difficult. However, many such patients, such as young autistic children, are poor candidates for assessment by fMRI, which requires patients to hold still for long intervals inside a confined imaging space with loud noise from the magnet.Optical imaging is fast, wearable, thus highly suitable for the most patients.

The research was led by an optical imaging expert Dr. Ulas Sunar, an associate professor of Biomedical, Industrial and Human Factors Engineering and the Ohio Research Scholar for Medical Imaging at Wright State University, along with Dr. Jun Li, Chien Poon, Jeremy Kress and Dr. Dan Rohrbach. The team has recently published in Journal of Biophotonics the first validated use of optical blood flow contrast to detect RSFC in the human brain. DCS is a relatively new optical technology based on detecting light scattering from moving blood cells and can quantify absolute cerebral blood flow related contrast. It is a complementary technique to widely known functional near infrared spectroscopy (fNIRS) that measures blood oxygenation.

The Sunar group used blood flow parameter to quantify RSFC in in nine healthy adult males as a proof-of-concept study. To determine whether DCS-based CBF could accurately detect RSFC, two areas of the brain with known RSFC properties were examined.  Connectivity between two sites within the left and right dorsolateral frontal cortex (DLFC) were chosen, as they are known to have strong connectivity.  Also, connectivity between the inferior frontal cortex (IFC) and the DLFC were chosen, as they are known to have low connectivity. The DCS technique showed high connectivity withinthe DLFC areas, butlower connectivity between the IFC and DLFC areas, which matches similar studies performed previously with other methods such as fMRI. “These are exciting results in our field since the study has proven the potential of DCS as a non-invasive means to assess RSFC in humans. Cerebral blood flow is a avery important parameter for neuronal disease characterization and it can show much higher contrast than other parameters such as cerebral oxygenation” said Sunar.

The optical imaging set-ups are far less sensitive to motion artifacts than fMRI and have been successfully used for functional brain imaging even in very young infants.The Sunar team is planning to utilize DCS technique for accurate characterization of neuronal diseases such as autism. They anticipate that this modality will ultimately become a highly useful tool for non-invasively assessing brain function in young and disabled patients.

Journal of Biophotonics publication: https://onlinelibrary.wiley.com/doi/abs/10.1002/jbio.201700165 

Sunar Research Group:  http://biomil.org