It goes without saying that the earlier someone can be warned of an impending heart attack or stroke, the better. A new skin patch could provide such warnings, by sending ultrasound pulses into the wearer's body.
Building upon a previously developed device, the patch was created at the University of California-San Diego by a team led by Prof. Sheng Xu. Worn on the neck or chest, it consists of a thin sheet of flexible, stretchable polymer, inside of which is a 12 by 12 grid of millimeter-sized ultrasound transducers. The patch is currently hard-wired to a computer and power source, but plans call for it to ultimately be self-contained and wireless.
In one operational mode, all of the transducers can be set to transmit ultrasound wave pulses at the same time. This produces an ultrasound beam that focuses directly down onto one area of the body, up to 14 cm (5.5 in) beneath the skin.
In the other mode, the transducers transmit their waves out of sync with one another, but still rapidly enough that they form one cohesive beam. In this case, however, that beam can be pointed in different angles, as opposed to just straight down from the patch. This means that different areas could be scanned without having to stick the patch right above each one.
In either case, the ultrasound beam travels through the body tissue and into a major blood vessel. The beam then echoes off the red blood cells moving through that vessel, and back up to the patch.
By analyzing how the frequency of the echo is affected by the rate at which the blood cells are flowing, it's possible to continuously monitor the wearer's blow flow, blood pressure and heart function – all in real time. This information can in turn be used to determine if cardiovascular problems are beginning to occur.
When tested, the patch was shown to perform on par with traditional handheld ultrasound probes. Such probes have to be operated by trained technicians in clinics, however, plus the results can vary depending on the skills of individual users – this is reportedly not the case with the patch.
"Just stick it on the skin, then read the signals," says PhD student Sai Zhou, co-author of a paper on the study. "It's not operator-dependent, and it poses no extra work or burden to the technicians, clinicians or patients. In the future, patients could wear something like this to do point of care or continuous at-home monitoring."
The paper was recently published in the journal Nature Biomedical Engineering.