ASSIST is working with Centre for Research in Medical Devices (CÚRAM) and the Centre for Cancer Research and Cell Biology (CCRCB) at Queens University Belfast to develop novel externally-powered implants for continuous cardiac health monitoring. A particular device involves abdominal aortic aneurysm (AAA), which is a condition in which the aortic wall becomes enlarged, which can ultimately lead to rupturing of the artery, significant internal bleeding and death. Most aneurysms are currently treated by endovascular aneurysm repair (EVAR), by lining the aorta using a stent-graft. Monitoring the sealing of these grafts is essential to ensure no leaks are present.
We develop a system that is powered externally using ultrasound. The ultrasonic transducer that receives power is also used to measure the size of the aneurysm and to communicate the measurements to the outside. Such an implantable monitoring device that can be activated on demand or periodically, eliminates the need for the patient to come back to the hospital for imaging-based assessments and hence minimizes the radiation exposure to the patient.
Ultrasound is an attractive modality for transferring power to biomedical implants. Ultrasound is already widely accepted in medical diagnostic applications with intensities as high as 720 mW/cm2 as regulated by the FDA. A receiving ultrasonic transducer embedded in the implanted device can convert acoustic power to electrical power for use by the sensors and associated data processing circuitry. We implement the described device by using a capacitive micromachined ultrasonic transducer (CMUT) that is integrated with supporting circuits in a small implantable form factor.