It only takes 30 to 90 seconds to take the images for ultrasound localisation microscopy. © Roberto Schirdewahn

Medical Engineering Bubbles in Ultrasound Reveal Tiny Vessels

A touch of the button is all it takes to improve the resolution of ultrasound images fivefold. This is down to bubbles floating in the bloodstream and a clever algorithm.

To the trained eyes of a doctor, the grey-white shapes and textures of an ultrasound image reveal more than to the layperson. But the tiniest vascular structures have remained elusive – until now. The team from the Department of Medical Engineering at Ruhr University Bochum headed by Professor Georg Schmitz is perfecting ultrasound localization microscopy (ULM). By deploying a commercially available contrast agent with microbubbles and performing a number of calculation steps, it’s now possible, for example, to image the vascular structure of a mouse kidney in minute detail, as well as the vascular structure of tumors. Rubin, the science magazine of Ruhr University Bochum, Germany, features an article on this research.

Schmitz and his team have been refining this technique for over ten years. In 2011, they came up with the brilliant idea of using a contrast agent consisting of microbubbles for the high-resolution imaging of vessels in ultrasound. They follow the flow of blood into the smallest vessels and reflect ultrasound waves so well that they light up white in the image. “The contrast agent only remains in the body for around ten minutes, then the bubbles are broken down and the gas is exhaled through the lungs,” explains Georg Schmitz. It only takes 30 to 90 seconds to take the images.

Marking the center of each vesicle

In order to increase the resolution of an ultrasound image so dramatically, it’s necessary to perform several intermediate steps. The involuntary movements of the patient’s body must be taken into account. In the next step, the algorithm developed by the researchers removes the background from the images so that only the vesicles are displayed. Then, the center of each individual bubble must be marked. And finally: the tricky calculation of which bubble has traveled along which path. “Our algorithm always looks at a group of neighboring images and uses the highest probability to decide which path a bubble has taken,” explains Georg Schmitz.

What ultimately emerges from the entire calculation after a few minutes is an image of the system of small vessels through which the bubbles have moved. It’s even possible to read off the direction and speed in which the bubbles have streamed through.

Measuring or predicting therapeutic success

“The direction of movement and the shape of the small vessels through which the blood flows are information that physicians need to know precisely,” stresses Georg Schmitz, who has worked with clinical partners on several projects. “This is because it allows them to identify the characteristics of a tumor, for example: Where is it supplied from? What do the supplying blood vessels look like?” Such information can provide insight into how aggressive a disease is and possibly also which therapy will or will not work. Looking at the smallest vessels is also valuable for monitoring the effect of chemotherapy. Ultrasound localization microscopy is currently the only clinical imaging method that can make such fine blood vessels visible at a depth of several centimeters.

Detailed article in science magazine Rubin

You can find a detailed article on this topic in the science magazine Rubin, the “In Motion” edition. For editorial purposes, the texts on the website may be used free of charge provided the source “Rubin – Ruhr-Universität Bochum” is named, and images from the download page may be used free of charge provided the copyright is mentioned and the terms of use are complied with.

Rubin can be subscribed to via an online form free of charge as a newsletter or print magazine.

Press contact

Prof. Dr. Georg Schmitz
Chair for Medical Engineering
Faculty of Electrical Engineering and Information Technology
Ruhr University Bochum
Germany
Phone: +49 234 32 27573
Email: georg.schmitz@ruhr-uni-bochum.de

Published

Wednesday
29 May 2024
11:12 am

By

Meike Drießen (md)

Translated by

Donata Zuber

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