2026 Theses Doctoral

A Wearable Ultrasound Imager for Chronic Point-of-Care Settings

Letchumanan, Jagannaath Shiva

Point-of-care ultrasound (POCUS) is greatly transforming healthcare due to the safety and ubiquity of ultrasound imaging, with rapid diagnoses being possible at the patient's bedside. Wearable ultrasound imagers have the capability to augment POCUS as they become more cost-effective and do not require expertise to operate unlike standard ultrasound machines or the modern hand-held devices. Wearables leverage the use of integrated circuits and wafer-level processing techniques, that can be scaled to mass production, resulting in a plethora of recent works in the wearable ultrasound space.

However, most conformable devices are often tethered to bulky imaging systems through long passive cables, or use very few channels limiting the imaging volume. Similarly, work in ultrasound-specific integrated circuits (IC) is predominantly done on rigid substrates like FR4 printed circuit boards, which are sub-optimal for acoustic transmission and create coupling issues due to their rigidity. For chronic imaging and observation, a truly wearable device is required: one that is both mechanically-flexible and has built-in front-end circuits to reduce cable length and effective system volume.

In this thesis, I detail the design of the FlexUS device, which contains an application-specific integrated circuit (ASIC), a flexible and conformable polyimide substrate for acoustic backing and thermal dissipation, an acoustic matching layer that is also bio-compatible and a fully self-contained data processing flow that does not require any complex electronics other than a laptop. The FlexUS device was able to map the internal jugular vein and carotid arteries, as well as track motion of the pleura, demonstrating its use case for guiding central venous catheters and chronic pulmonary observation.