Ultrasonic sensors for monitoring the condition of a vascular graft

Abstract

A parameter indicative of the status of fluid flow is remotely monitored in a vessel, a natural graft, or a synthetic graft. One or more transducers are provided either in a wall of a synthetic graft or adjacent to a vessel or natural graft to monitor the parameter. A conformal array transducer or a tilted element is used to monitor fluid flow or velocity through the graft or vessel based on the effect of the fluid on ultrasonic waves produced by the transducers. The conformal array transducer comprises a plurality of elements that curve around the graft or vessel and are excited with an input signal provided by an implantable electronics circuit, producing ultrasonic waves that propagate into the fluid flowing within the graft or vessel. Transit time or Doppler measurements are made using an appropriate number of these transducer to determine either fluid flow or velocity. Various implantable electronic circuits are provided that enable a selected transducer to be driven and to receive an ultrasonic signal or a pressure signal indicative of the status of fluid flow monitored by the transducer. The implanted electronic circuit is connected to an implanted radio frequency (RF) coil. An external coil that is connected to a power supply and monitoring console is coupled to the implanted RF coil to convey power and receive data signals from the transducer that are indicative of the parameter being monitored.