Ultrasound localization microscopy can image microscopic vessels and measure blood flow in the brain

To image microscopic vessels and measure blood flow in the brain, researchers use a tool called ultrasound localization microscopy. It works by using microscopic bubbles circulating in the bloodstream as a contrast agent to measure the reflection of high frequency acoustic waves passing through the body. Until recently, acquiring images in this manner was slow and data-intensive.

Researchers at the Beckman Institute for Advanced Science and Technology have developed a curve-based algorithm to rapidly measure and reconstruct whole-brain vasculature and blood flow in the brains of mice. Their work could be used to enable future research into the neurovascular mechanisms underlying conditions such as Alzheimer’s disease.

Qi You, a graduate student researcher at the University of Illinois at Urbana-Champaign, led the research under Pengfei Song, assistant professor of electrical and computer engineering and bioengineering.

Their approach deploys ultrasound technology to produce whole-brain images of animal microvasculature in just seconds.

Our method is a huge improvement for the practicality of this technology. Instead of averaging two or three minutes of data together, we only need one or two seconds of data and have a good picture. The temporal resolution is greatly improved, and this is very important for measuring the dynamic properties of blood flow.”

Pengfei Song, Assistant Professor of Electrical and Computer Engineering and Bioengineering

The method relies on rotating and scaling many small arbitrary curves to fit the local structure of the microbubble imaging data.

“Locally, vessels are actually very similar to curves, these little curves. You can decompose any arbitrary shaped vessel into a combination of arbitrary curves. When you apply a curvature transformation to the microbubble data, you find that you only need a very small amount of data to represent the entire complete structure of the vessels.We have verified this algorithm in several different types of tissues and vascular structures, on which it performs well. are heterogeneous, but locally they follow a similar homogeneous structure,” You said.

Combining this curve pattern with a parsimony-promoting algorithm yielded an efficient and highly generalizable method for measuring blood flow and vascularity from microbubble data in the mouse brain.

The research was carried out in collaboration with Dr. Dan Llano, professor of molecular and integrative physiology.

“We have developed a tool capable of imaging whole-brain microvasculature with very high spatial resolution and depth of penetration. For researchers like Dan, the use of small animal disease models is very important to mechanistically understand pathologies such as aging, Alzheimer’s disease or strokes. says the song.

The method requires a very small amount of microbubble data to reconstruct blood flow and tissue microvasculature. It takes advantage of the inherent sparseness of fast ultrasound imaging and speeds up post-processing by 10 to 30 seconds, You said.

Song pointed to Beckman’s unique interdisciplinary environment as a key driver for the collaboration.

“Our technology is, to our knowledge, the only one capable of imaging whole-brain microvasculature at very high resolution, so it’s a very attractive tool for neuroscientists,” Song said. “Beckman’s collaborative environment encourages scientists to connect with each other and create this type of research. On the fourth floor, we build these powerful imaging tools and collaborate with researchers like Dan on the second floor who will use the things we’re building. The Beckman Institute is essential to that research.”

Microbubbles are widely used as ultrasound imaging contrast in clinical ultrasound of humans, opening the door for future clinical translation of the technology as non-invasive assessment of stroke, vascular occlusion, and pain. neurovascular health, Song said.

“Many neurological diseases and disorders have a very strong correlation with vascular disease. Ultimately, our ultrasound technology could be a good candidate for a screening technology, due to its low cost, portability, and convenience. There is also a strong need to develop this technology for preclinical applications,” he said.


Beckman Institute for Advanced Science and Technology

Journal reference:

You, Q. et al. (2022) Curvelet transform-based parsimony-promoting algorithm for rapid ultrasound localization microscopy. IEEE Transactions on Medical Imaging. doi.org/10.1109/TMI.2022.3162839.

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