First images of live blood vessels in unprecedented clarity

By Helen Thomson BREAK out the bubbly. We have the clearest images yet of blood vessels in live animals, thanks to microbubbles. The new ultrasound technique allows doctors to image organs deep in the body in microscopic detail for the first time, and will aid the diagnosis and treatment of diseases such as cancer and strokes. The resolution we can reach when imaging organs is limited, and compromises have to be made between clarity, speed and how deep inside the body we try to look. But tiny gas-filled bubbles about 2 micrometres in diameter can give a clear view of deep tissues in close to real time. By injecting these microbubbles into the organs of a live rat and targeting them with ultrasound, Mickael Tanter at the Langevin Institute in Paris and his colleagues have visualised its tiniest blood vessels. The technique takes advantage of how high-frequency ultrasound waves interact with these microbubbles. When one hits a microbubble, some of its energy bounces back. Tanter says that if ultrasound imaging is used at a high-speed rate of several thousand frames per second, echoes can be distinguished coming from each individual bubble in each frame, allowing his team to track their exact location as they travel throughout the blood system. It took the team just tens of seconds to create an image of the blood vessels in the rat brain with pixels about the size of a red blood cell. In small animals such as rats, ultrasound waves can normally only be used to image features of about 150 micrometres or more. By using microbubbles, Tanter and his team managed to create images with a resolution of 10 micrometres (Nature, DOI: 10.1038/nature16066). He says they already know they can do better, and that they will soon reach a resolution of only 3 micrometres, even when imaging deep-seated organs such as the liver. This kind of microscopic imaging will soon be used in clinics to help us understand diseases that modify blood-vessel systems, says Tanter. For instance, the number of tiny vessels that appear alongside tumours when they start to form can help doctors diagnose what stage a cancer is at. “It will also be used to map the whole brain at unprecedented resolutions and give new insights in the understanding and follow-up of stroke,” says Tanter. This is a very exciting new technique, says Eleanor Stride, who studies the therapeutic use of microbubbles at the University of Oxford. She says that the possibility of replacing current imaging techniques for visualising the blood supply, which use potentially harmful radiation, is great news for patients. “Being able to image micro-scale blood vessels is extremely important for accurate diagnosis and treatment monitoring in multiple diseases,” she says. (Image: ESPCI/Inserm/CNRS) This article appeared in print under the headline “Close-up of living blood vessels” More on these topics:
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