Ultrasonic Imaging Catheter

ABSTRACTWe report on a new imaging catheter using high frequency ultrasound toproduce short range (8 mm), high resolution rotary scan images from within bloodvessels. The objective of the system is to aid the interventional physician inperforming angioplasty on stenoses. This system provides an adjunct, andpotentially an alternative, to fluoroscopy and optical angioscopy in thediagnosis and visualization of stenotic lesions. We have constructed prototypesof a 6 F (2 mm) system and begun clinical evaluation in human peripheral vessels. 2. BACKGROUNDIntravascular and intraluminal ultrasound imaging is not a new concept;articles and patents from more than fifteen years ago describe simple rotationalultrasound scanners within catheters.) Until very recently, however, there hasnot been much interest in clinical use of such devices in the vasculature. Theexpansion of balloon angioplasty since its initial clinical use in 1977, andespecially its growth over the last two or three years in radiology, cardiology,and gastroenterology, has renewed interest in better visualization of vascularlesions. Major improvements in the technology of vascular catheters and relatedhardware (guidewires, introducer sheaths, catheter extrusion materials, etc.)have supported the development of great skill among interventionalists in the useof these tools.Another reason for the growth in clinical interest in intravascular imaginghas been the recent explosion in "next generation angioplasty" research. Lasers,atherectomy cutters, electrical and rf tissue ablators, abrasive grinders,stents, and other devices will all be competing with each other and with improvedangioplasty balloons for a place in the clinical armamentarium.2 All of thesedevices raise the demand for imaging technology; the physician can't treat whathe can't see. This has caused a surge in interest in imaging methods includingimproved digital fluoroscopy as well as "catheters you can see through ".Conventional fluoroscopy, even using expensive biplane and digitalequipment, provides the interventionalist with only a limited view of lesions.Improved methods are needed for determination of luminal size, lesion shape,eccentricity, depth into the vessel wall, and for characterization of the tissueof the lesion (e.g., hard or soft plaque, thrombus). The objective of our workis to evaluate whether the ultrasound imaging catheter is useful for thesefunctions.