Diffusion fMRI: Addressing Limitations of Current Medical Imaging Techniques

We in the Song Lab at Washington University in St. Louis Medical Center are working on a new magnetic resonance imaging (MRI) modality that has shown tremendous potential in bridging the gap between functional and structural MRI.

Structural MRI is the type of scan your doctor would order if you have a torn muscle. It images the structural connections in the body, such as muscles, tendons, ligaments, and even organs.

Functional MRI (fMRI) is employed in order to observe neuronal firing in the brain and central nervous system. This technique uses blood oxygen-level dependent contrast, or the amount of oxygenated blood flow in a certain region, to measure the body’s response to stimuli. This technique has served as a valuable tool for psychological exams and evaluating brain injuries.

However, these techniques image very different tissues in the body because certain tissues, such as nerve fibers, lack vascularity, which means fMRI’s dependence on blood flow limits its efficacy in studies of neurodegenerative diseases and brain ailments.

Thus, the current issue plaguing researchers and physicians is figuring out how to combine these MRI methods to gather structural AND functional information without relying on blood flow to illustrate the functional aspect. Most studies have been entirely unsuccessful.

Until now.

As described in a study that the Song Lab recently published, we have developed a technique that utilizes diffusion MRI to assess water diffusion within nerve fibers in response to visual stimuli. Thus, we are using the change in water diffusivity (structural MRI) within nerve fibers to illustrate the effects that functional stimuli have on the brain and the central nervous system as a whole (fMRI).

This marks the first time that researchers have been able to combine structural MRI and fMRI and validate the utility of the method for further use. Our current studies are focused on using this method to gain a better understanding of the physiological events that occur in nerve axons and surrounding myelin in response to neural stimuli. We can then apply this knowledge to combat diseases such as multiple sclerosis, Alzheimer’s disease, and more.




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