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Proceedings Paper

Implantable Ultrasonic Sensor For Postoperative Monitoring Of Blood Flow In Man
Author(s): Raphael S. Rabinovitz; Craig J. Hartley; Lloyd H. Michael; Peggy L. Jackson; Gary L. Liedtke; Gerald W. Parker; George P. Noon
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Paper Abstract

We have developed and built a miniature implantable 10 or 20 MHz pulsed ultrasonic Doppler sensor to provide continuous monitoring of blood flow in patients. The sensor is made from silicone rubber material and during surgery can be wrapped around a blood vessel and secured in place with a releasable tie. No tissue puncturing techniques are required. The wire leads and a release cable are sheathed in 2 mm diameter tubing and are exteriorized through the skin. Two to six days postoperatively when monitoring is no longer needed, the release cable is activated to release the tie, and the sensor is extracted from the patient by pulling on the tubing. We have tested 38 sensors on 6 carotid and 17 coronary arteries (2.5-4.5 mm diameter) and 15 ascending aortas (15-19 mm diameter) in 20 chronically instrumented dogs for up to 16 days. At the end of the implantation period, the sensors were extracted from the awake dogs with no visible behavioral reaction. Postmortem exams showed that none of the vessels were thrombosed or damaged, and the sensors were free of tissue. Doppler audio signals acquired with 20 MHz crystals from vessels 2.5-4.5 mm diameter had signal-to-noise ratios greater than 32 db, and the velocity signals had excellent linear correlations (r=0.99) with EMF sensors and timed blood collections. It has been found that the implantable sensor is a simple, reliable, and safe method of providing continuous monitoring of blood flow during and after surgery. The sensor has been granted F.D.A. Investigational Device Exemption (I.D.E.) approval, and we have begun clinical intraoperative evaluations on coronary artery bypass grafts (3-5 mm in diameter).

Paper Details

Date Published: 8 August 1989
PDF: 11 pages
Proc. SPIE 1068, Catheter-Based Sensing and Imaging Technology, (8 August 1989); doi: 10.1117/12.952170
Show Author Affiliations
Raphael S. Rabinovitz, Baylor College of Medicine (United States)
Craig J. Hartley, Baylor College of Medicine (United States)
Lloyd H. Michael, Baylor College of Medicine (United States)
Peggy L. Jackson, Baylor College of Medicine (United States)
Gary L. Liedtke, Baylor College of Medicine (United States)
Gerald W. Parker, Baylor College of Medicine (United States)
George P. Noon, Baylor College of Medicine (United States)

Published in SPIE Proceedings Vol. 1068:
Catheter-Based Sensing and Imaging Technology
Alan I. West, Editor(s)

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