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Anti-Bubble Transducer Housing for Ultrasonic Transducers

IP.com Disclosure Number: IPCOM000239324D
Publication Date: 2014-Oct-29
Document File: 2 page(s) / 39K

Publishing Venue

The IP.com Prior Art Database

Related People

Gerald Cabrera: AUTHOR

Abstract

Rotational intravascular ultrasound (IVUS) catheters comprise of an ultrasound transducer, rotated by a flexible driveshaft, and contained within a saline-filled catheter/sheath. Before using the device, the sheath must be filled with saline, which serves as a biocompatible lubricant for rotation of the flexible driveshaft within the sheath as well as conducting ultrasound. When filling the sheath with saline, it is important to expunge any air bubbles from within the sheath, since these bubbles can block the ultrasound waves if they collect in the vicinity of the transducer, thus introducing artifacts in IVUS images.

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Anti-Bubble Transducer Housing for Ultrasonic Transducers

Volcano Corporation, San Diego, CA

October 2014

Introduction

Rotational intravascular ultrasound (IVUS) catheters comprise of an ultrasound transducer, rotated by a flexible driveshaft, and contained within a saline-filled catheter/sheath.  Before using the device, the sheath must be filled with saline, which serves as a biocompatible lubricant for rotation of the flexible driveshaft within the sheath as well as conducting ultrasound.  When filling the sheath with saline, it is important to expunge any air bubbles from within the sheath, since these bubbles can block the ultrasound waves if they collect in the vicinity of the transducer, thus introducing artifacts in IVUS images.

Keywords: Rotational IVUS, bubbles, MEMS, ultrasound transducer, flushing

Anti- Bubble Transducer Housing


The primary method for removing bubbles from the catheter sheath is to flush the catheter with bubble-free saline, as needed, but sometimes bubbles stubbornly persist.  Various improvements to the catheter design could reduce formation and retention of bubbles on the transducer surface. One idea for bubble suppression is to coat the transducer face with a hydrophilic substance to encourage wetting of the transducer face. Another possible solution is to coat the inner lumen of the sheath with a hydrophilic material to encourage wetting of that inner surface of the sheath. Or, yet another solution could employ both of these design improvements.

Fig. 1 Shows a cross-sectional view of the ultrasound transducer mounted in housing at the distal tip of an IVUS probe.  As the housing (and saline) spin inside the sheath, bubbles are forced toward the center of rotation of the housing where they accumulate near the transducer face with no easy escape path.  As the catheter is flushed, the predominant fluid flow tends to remain close to the wall of the sheath, and it is difficult to flush the bubbles away from the transducer face, which is near the center of rotation.

Bubbles are naturally drawn to the transducer face by centrifugal force in a spinning fluid.  Centrifugal force is normally thought of in terms of an outward force on a spinning object, but centrifugal force on a buoyant object (such as an air bubble) pushes the object towards the center of rotation as the denser saline is pushed outward.  The transducer in a rotational IVUS catheter is typically located with its face close to the center of rotation within the sheath, and any bubbles in the vicinity of the transducer will tend to collect in a line in the middle of the transducer face, as close to the center of rotation as they can go.  These bubbles are difficult to flush away, since the saline flush...