A wireless ultrasound patch is placed on the neck. The probe is placed on the carotid artery. (Credit: Xu lab at UC San Diego)

A fully wireless ultrasound patch can continuously track critical vital signals such as heart rate and blood pressure. The patch, which can capture detailed medical information and wirelessly transmit the data to a smart device (such as a laptop or smartphone), could represent a major step forward in at-home health care technology.

The ultrasound system is composed of a probe, a circuit, and a battery. As the current system was designed with a focus on cardiovascular health, the ultrasound probe was typically placed on the carotid artery in this study. The probe is attached to a flexible circuit, which activates the ultrasound transducers, collects the ultrasound echoes, amplifies, and filters these echoes, and transmits the digitized signal to a terminal device. The entire system is powered by a commercial rechargeable lithium polymer battery.

To assess its generalizability, the researchers cross-validated their machine learning model among 10 healthy subjects representing three distinct racial groups. Using a machine learning technique called domain adaptation, the researchers found that a model trained on data from one participant wearing the patch could be successfully adapted for the other participants.

With minimal model retraining, the patch could track the pulsations of the carotid artery with high accuracy, allowing for measurements like blood pressure, arterial stiffness, and cardiac output. Continual monitoring of these measurements among high-risk populations could provide advance warning of heart failure.