A review of totally implantable wireless ultrasonic Doppler blood flowmeters : towards accurate miniaturized chronic monitors
Totally implantable wireless ultrasonic blood flow meters provide directaccess chronic vessel monitoring in hard-to-reach places without using wired bedside monitors or imaging equipment. While the accuracy of wireless implantable Doppler devices satisfies most applications, device size and implant lifetime remain vastly underdeveloped. This paper reviews past and current approaches to miniaturization and implant lifetime extension for wireless implantable Doppler devices, and it proposes approaches to reduce device size and maximize implant lifetime for the next generation of devices. Additionally, this paper reviews current and past approaches to accurate blood flow measurements. This review points towards relying on increased levels of monolithic customization and integration to reduce size. Meanwhile, recommendations to maximize implant lifetime should pursue alternative sources of power, such as transcutaneous wireless power, which stand to extend ∗Corresponding Author: Ervin Sejdić, 3700 O’Hara St. Benedum Hall Room 1238 Pittsburgh, PA 15261; E-mail: esejdic@pitt.edu, Phone: 412-624-8003 Preprint submitted to Ultrasound in Medicine and Biology October 10, 2016 lifetime indefinitely. Coupling together the results will pave the way for ultra-miniaturized totally implantable wireless blood flow monitors for truly chronic implantation.