Abstract: Vascular catheter for measuring flow characteristics of a liquid in a vessel having a wall and an axis extending longitudinally of the vessel parallel to the vessel wall comprising a flexible elongate tubular member adapted to be introduced into the vessel and having proximal and distal extremities. The flexible elongate member has a lumen extending therethrough. The flexible elongate member has at least one preformed bend thereon adjacent the distal extremity. A plurality of ultrasonic transducers are mounted on the flexible elongate member adjacent to the bend. Conductors are connected to the ultrasonic transducers and extend through the proximal extremity of the flexible elongate tubular member. The flexible elongate member has an opening therein in the distal extremity which is a communication with the lumen.

Abstract: A doppler guide wire having an inflatable balloon thereon which is inflatable with a balloon inflation medium. An elongate flexible member having proximal and distal extremities. An ultrasonic transducer is secured to the distal extremity of the elongate flexible member. An inflatable balloon mounted on the distal extremity of the elongate flexible member proximal of the ultrasonic transducer. A balloon inflation lumen opens into the interior of the balloon and extends along the length of the elongate flexible member. Conductors are connected to the ultrasonic transducer and extend along the length of the elongate flexible member.

Abstract: Method for providing micro-miniature high efficiency ultrasonic transducer assembly having a diameter of 0.018 inches or less. A transducer is formed from a selected transducer material to provide a cylindrical transducer having front and back sides with a thickness which is one-half of the diameter of the transducer +/-5%. The frequency constant of the material is ascertained. The frequency of operation of the transducer is ascertained by dividing the frequency constant by the thickness of the transducer in mils. The transducer is mounted in a housing and leads are secured to the front and back sides of the transducer.

Abstract: Apparatus for measuring the volumetric flow of a liquid in a vessel having a wall and having an axis extending longitudinally of the vessel parallel to the vessel wall. A flexible catheter is provided which has a longitudinal axis adapted to be disposed in the vessel. The catheter has front and back sides. First, second, third and fourth transducers are carried by the catheter. The first, second and fourth transducers are disposed on the front side of the catheter and the third transducer is positioned on the back side of the catheter. The second and fourth transducers are spaced apart a predetermined distance. The first, second and third transducers comprise a first set of transducers and the first, third and fourth transducers comprise a second set of transducers. Instrumentation is connected to the first, second, third and fourth transducers. The instrumentation causes the first, second, third and fourth transducers to emit ultrasonic energy beams therefrom.

Abstract: Guidewire comprising a flexible elongate member having a distal extremity with an ultrasonic transducer secured to the distal extremity of the flexible elongate member. The transducer has a diameter ranging from 0.007 inches to 0.018 inches and has a thickness and a diameter to provide a transducer having an aspect ratio with a thickness which is one-half of the diameter .+-.5%. Electrical leads are connected to the transducer and extend the length of the flexible elongate member.