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June 24, 2019 — Medgadget

Imaging the heart for signs of disease is still quite rudimentary. While CT, ultrasound, and PET (positron-emission tomography) scanners generate impressive looking graphics, they’re a long way from giving doctors a true representation of the anatomy and function of the heart and nearby vasculature.

Contrast agents are widely used to allow these modalities to produce better images of the heart, but they’re indiscriminate in what they help to illuminate. Similar to a flood light, these agents tend to make everything they permeate brighter on the output display. This results in larger vessels being visible, but smaller ones getting lost in the picture.

Researchers at Drexel University appear to have developed the first heart-activated contrast agent for ultrasound imaging. The material consists of a drop of perfluorocarbon, already used as an ultrasound contrast agent, placed inside a lipid. Lipids are widely used by our own bodies to protect signaling molecules, store energy, and as parts of cellular membranes because they’re not soluble in water.

When the voltage- and ultrasound-sensitive lipids carrying the perfluorocarbon get close to the heart during ultrasound imaging, they break apart because of the cardiac electrical activity and ultrasound waves. This means that they release their contents, activating the contrast medium in the cardiac vessels.

This makes it unnecessary to use catheters and other devices to release the contrast agent as close to the heart as possible, something that is performed today using indiscriminate contrast agents. The material can be injected in any vein.

“Our goal is to provide a sharper image and we can achieve that by tailoring our tracer dye so it’s only visible in the area that we’re trying to see,” said Steven Wrenn, PhD., the corresponding author of the research appearing in journal Applied Acoustics. “If you’re trying to get a close look at blood flow to the myocardium you want to distinguish between the blood that’s in the muscle and the blood that’s being pumped by the muscle. It’s not helpful if a contrast agent is in the muscle and also lighting up in the chambers of the heart — it’s like trying to see fainter stars when there’s a full moon.”

The researchers plan to present their research at the upcoming 34th Advances in Contrast Ultrasound International Bubble Conference in Chicago, September 5th and 6th, 2019

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