Groundbreaking MRI technique reveals microvascular pulsations in the aging brain

Researchers at the Mark and Mary Stevens Neuroimaging and Informatics Institute (Stevens INI) at the Keck School of Medicine of USC have developed a groundbreaking brain imaging technique that reveals how tiny blood vessels in the brain pulse with each heartbeat-changes that may hold clues to aging and diseases such as Alzheimer’s.

The study, published in Nature Cardiovascular Research, introduces the first noninvasive method for measuring “microvascular volumetric pulsatility”-the rhythmic expansion and contraction of the brain’s smallest vessels-in living humans. Using ultra-high field 7T magnetic resonance imaging (MRI), the team showed that these microvessel pulses increase with age, especially in the brain’s deep white matter, a region critical for communication between brain networks. As people age, this white matter is particularly susceptible to reduced blood supply of distal arteries, the blood vessels that carry blood away from the heart and into the farthest parts of the body. Increasing microvessel pulses can disrupt systems in the brain, possibly speeding up memory loss and Alzheimer’s disease.

Arterial pulsation is like the brain’s natural pump, helping to move fluids and clear waste. Our new method allows us to see, for the first time in people, how the volumes of those tiny blood vessels change with aging and vascular risk factors. This opens new avenues for studying brain health, dementia, and small vessel disease.”

Danny JJ Wang, PhD, professor of neurology and radiology at the Keck School of Medicine and senior author of the study

For decades, researchers have known that large artery stiffness and pulsatility are linked to stroke, dementia, and small vessel disease. But until now, it has been nearly impossible to measure these pulsations in the brain’s smallest vessels without invasive methods used only in animal studies.

The USC team’s innovation combines two advanced MRI approaches-vascular space occupancy (VASO) and arterial spin labeling (ASL)-to track subtle volume changes in microvessels over the cardiac cycle. The researchers confirmed that older adults show heightened microvascular pulsations in deep white matter compared to younger adults, and that hypertension further amplifies these changes. “These findings provide a missing link between what we see in large vessel imaging and the microvascular damage we observe in aging and Alzheimer’s disease,” said lead author Fanhua Guo, PhD, who is a postdoctoral researcher in Wang’s lab.

Excessive vascular pulsatility may impair the function of the brain’s “glymphatic system,” a newly recognized network that clears waste products like beta-amyloid-proteins that build up in Alzheimer’s disease. Over time, disrupted fluid circulation could accelerate cognitive decline.

“Being able to measure these tiny vascular pulses in vivo is a critical step forward,” said Arthur W. Toga, PhD, director of the Stevens INI. “This technology not only advances our understanding of brain aging but also holds promise for early diagnosis and monitoring of neurodegenerative disorders.”

The researchers are exploring how the method could be adapted for wider clinical use, including on more commonly available 3T MRI scanners. Future studies will test whether microvascular volumetric pulsatility predicts cognitive outcomes and whether it can serve as a biomarker for early intervention in Alzheimer’s disease and related conditions.

“This is just the beginning,” Wang said. “Our goal is to bring this from research labs into clinical practice, where it could guide diagnosis, prevention, and treatment strategies for millions at risk of dementia.”

About the study

In addition to Wang, the study’s other authors are Fanhua Guo, Chenyang Zhao, Qinyang Shou, Kay Jann, and Xingfeng Shao from the Stevens INI, and Ning Jin from Siemens Healthcare.

This research was supported by the National Institutes of Health (NIH) grants UF1-NS100614, S10-OD025312, R01-600 NS114382, R01-EB032169, RF1AG084072, R01-EB028297, R01-NS134712, and R01-NS121040.