Intracardiac ultrasound scanner using a micromachine (MEMS)actuator

摘要

Catheter-based intracardiac ultrasound offers the potential fornimproved guidance of interventional cardiac procedures. The objective ofnthis research is the development of catheter-based mechanical sectornscanners incorporating high frequency ultrasound transducers operatingnat frequencies up to 20 MHz. The authors' current transducer assemblynconsists of a single 1.75 mm by 1.75 mm, 20 MHz, PZT element mounted onna 2 mm by 2 mm square, 75 Μm thick polyimide table that pivots onn3-Μm thick gold plated polyimide hinges. The hinges also serve as thenelectrical connections to the transducer. This table-mounted transducernis tilted using a miniature linear actuator to produce a sector scan.nThis linear actuator is an integrated force array (IFA), which is annexample of a micromachine, i.e., a microelectromechanical system (MEMS).nThe IFA is a thin (2.2 Μm) polyimide membrane, which consists of annetwork of hundreds of thousands of micron scale deformable capacitorsnmade from pairs of metallized polyimide plates. IFAs contract with annapplied voltage of 30-120 V and have been shown to produce strains asnlarge as 20% and forces of up to 8 dynes. The prototype transducer andnactuator assembly was fabricated and interfaced with a GagePCI analog tondigital conversion board digitizing 12 bit samples at a rate of 100nMSamples/second housed in a personal computer to create a single channelnultrasound scanner. The deflection of the table transducer in a lownviscosity insulating fluid (HFE 7100, 3M) is up to ±10° atnscan rates of 10-60 Hz. Software has been developed to produce real-timensector scans on the PC monitor