Abstract: A method for inhibiting hyperplasia at an anastomotic junction of a vascular fistula or vascular graft comprises exposing the anastomotic junction to vibrational energy at a mechanical index and for a time sufficient to inhibit hyperplasia. Kits are described comprising the catheter or a probe suitable for performing the methods together with instructions for use setting forth the methods. The methods and kits are particularly suitable for treating anastomotic junctions formed to provide vascular access for hemodialysis, hemofiltration, and the like. The methods and kits are also suitable for treating other vascular grafts, such as those formed during cardiac bypass graft surgery, vascular repair, and the like.

Abstract: Transducers and systems for applying ultrasonic energy to enhance drug delivery are illustrated.

Abstract: A method for inhibiting hyperplasia at an anastomotic junction of a vascular fistula or vascular graft comprises exposing the anastomotic junction to vibrational energy at a mechanical index and for a time sufficient to inhibit hyperplasia. Kits are described comprising the catheter or a probe suitable for performing the methods together with instructions for use setting forth the methods. The methods and kits are particularly suitable for treating anastomotic junctions formed to provide vascular access for hemodialysis, hemofiltration, and the like. The methods and kits are also suitable for treating other vascular grafts, such as those formed during cardiac bypass graft surgery, vascular repair, and the like.

Abstract: A method of treating a target region in a body lumen, said method comprising: directing a uniform dose of ultrasonic energy from an interior of the lumen radially outward over a treatment length of the lumen, wherein the dosage of ultrasonic energy received at any one point along the length varies by no more than plus or minus 6 decibels from that received at any other point along the length.

Abstract: A method of treating a target region in a body lumen, said method comprising: directing a uniform dose of ultrasonic energy from an interior of the lumen radially outward over a treatment length of the lumen, wherein the dosage of ultrasonic energy received at any one point along the length varies by no more than plus or minus 6 decibels from that received at any other point along the length.

Abstract: A guide wire having pressure sensing capabilities for measuring the pressure of liquid in a vessel comprising a flexible elongate member and having proximal and distal extremities and having an outside diameter of 0.018" or less. The distal extremity of said flexible elongate member is adapted to be disposed in the liquid in said vessel. A housing is carried by the flexible elongate member and has a diameter substantially the same as the diameter of the flexible elongate member. The housing has a space therein with a pressure sensor mounted in the space in the housing. The pressure sensor has a diaphragm that is sensitive to changes of pressure in the liquid in the vessel. The diaphragm is rectangular in shape and is bordered by a rim surrounding the well. A backing plate is formed of an insulating material bonded to the crystal and serves to reinforce the rim of the crystal of semiconductor material.

Abstract: Ultrasonic transducer with a selectable beamwidth comprising a body of piezoelectric material in the form of an annulus having an outer diameter D and a thickness T. The body has proximal and distal generally planar parallel surfaces and a centrally disposed hole extending therethrough. The body has a cylindrical wall with a width W extending from the hole to the outer diameter. The transducer is capable of operating at low and high resonance frequencies with the low frequency resonance being determined by the diameter D and an aspect ratio of D/T and the high frequency resonance being determined by the thickness T and an aspect ratio of W/T.

Abstract: A guide wire assembly comprises a tubular body having a distal end and an proximal end. At least a portion of the body comprises a single continuous helical spring to which one or more tubular electrodes are secured. The electrodes are insulated from the spring by means of an insulator. The electrodes can take a variety of forms, including conductive ribbons, longitudinally split conductive tubes, tubular sections, etc. The guide wire assembly may further include a variety of sensors, such as velocity sensors or temperature sensors. In order to allow flowable material to be passed to the distal end of the guide wire, the guide wire can include a catheter tube passable over the tubular body of the guide wire.

Abstract: Ultrasonic transducer with a selectable beamwidth comprising a body of piezoelectric material in the form of an annulus having an outer diameter D and a thickness T. The body has proximal and distal generally planar parallel surfaces and a centrally disposed hole extending therethrough. The body has a cylindrical wall with a width W extending from the hole to the outer diameter. The transducer is capable-of operating at low and high resonance frequencies with the low frequency resonance being determined by the diameter D and an aspect ratio of D/T and the high frequency resonance being determined by the thickness T and an aspect ratio of W/T.

Abstract: A guidewire having pressure sensing capabilities for measuring the pressure of liquid in a vessel comprising a flexible elongate member and having proximal and distal extremities and having an outside diameter of 0.018" or less. The distal extremity of said flexible elongate member is adapted to be disposed in the liquid in said vessel. A housing is carried by the flexible elongate member and has a diameter substantially the same as the diameter of the flexible elongate member. The housing has a space therein with a pressure sensor mounted in the space in the housing. The pressure sensor has a diaphragm that is sensitive to changes of pressure in the liquid in the vessel. The diaphragm is rectangular in shape and is bordered by a rim surrounding the well. A backing plate is formed of an insulating material bonded to the crystal and serves to reinforce the rim of the crystal of semiconductor material.

Abstract: Ultrasonic transducer with a selectable beamwidth comprising a body of piezoelectric material in the form of an annulus having an outer diameter D and a thickness T. The body has proximal and distal generally planar parallel surfaces and a centrally disposed hole extending therethrough. The body has a cylindrical wall with a width W extending from the hole to the outer diameter. The transducer is capable of operating at low and high resonance frequencies with the low frequency resonance being determined by the diameter D and an aspect ratio of D/T and the high frequency resonance being determined by the thickness T and an aspect ratio of W/T.

Abstract: A method of diagnosing and treating the human or animal body comprises feeding a flexible guide wire, dimensioned to be inserted into human coronary arteries, along a blood vessel in the human or animal body and epicardially mapping the electrocardiographic signals by means of electrodes secured to the guide wire. The method of diagnosing and treating the human or animal body may include the step of ablating selected body tissue by establishing a DC or radio frequency current through the body tissue between a pair of electrodes in which at least one of the electrodes is located on the guide wire. The method may also include passing flowable material to or from selected tissue by means of a catheter passed over the guide wire. The method may optionally include sensing the velocity of blood flow in the blood vessel by means of a velocity sensor mounted on the guide wire, or the temperature of selected body tissue by means of a temperature sensor mounted on the guide wire.

Abstract: An apparatus for generating a velocity spectrogram is described. The apparatus includes a transducer which is positionable within a vessel. The transducer receives a time-varying Doppler signal which contains information related to fluid velocity values within the vessel. A Fourier transformation device processes the time-varying Doppler signal to generate a sequence of spectra. Each spectrum corresponds to a segment of the time-varying Doppler signal and defines a set of velocities and their corresponding spectral values. A device is used to identify the instantaneous spectral peak velocity within each spectra. The peak velocity corresponds to the highest velocity within a spectra which has a spectral value above a defined threshold value which is related to the background noise level. The sequence of spectral peak velocities is plotted on a visual interface device to form an instantaneous spectral peak velocity waveform.

Abstract: System for measuring a characteristic of flow of liquid in a vessel of a patient comprising a transducer positioned in a vessel in a patient for supplying ultrasonic energy. The transducer produces a substantially inform beam which encompasses the vessel. The transducer receives ultrasonic energy back scattered from the red blood cells and provides an electrical output signal. A first moment detector is provided which receives the electrical output from the transducer and provides a first moment signal. Normalization is provided to the output of the first moment detector to provide an electrical output representing a characteristic of the flow of the liquid in the vessel.

Abstract: System for measuring a characteristic of flow of liquid in a vessel of a patient comprising a transducer positioned in a vessel in a patient for supplying ultrasonic energy. The transducer produces a substantially uniform beam which encompasses the vessel. The transducer receives ultrasonic energy back scattered from the red blood cells and provides an electrical output signal. A first moment detector is provided which receives the electrical output from the transducer and provides a first moment signal. Normalization is provided to the output of the first moment detector to provide an electrical output representing a characteristic of the flow of the liquid in the vessel.

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: System for measuring a characteristic of flow of liquid in a vessel of a patient comprising a transducer positioned in a vessel in a patient for supplying ultrasonic energy. The transducer produces a substantially uniform beam which encompasses the vessel. The transducer receives ultrasonic energy back scattered from the red blood cells and provides an electrical output signal. A first moment detector is provided which receives the electrical output from the transducer and provides a first moment signal. Normalization is provided to the output of the first moment detector to provide an electrical output representing a characteristic of the flow of the liquid in the vessel.

Abstract: Apparatus for measuring 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 adapted to be disposed in the vessel. First and second ultrasonic transducers are carried by the catheter on one side of the catheter and face the wall of the vessel so that the beams from the transducers each cross substantially the longitudinal axis of the vessel. The first transducer beam is inclined at an angle with respect to the longitudinal axis of the vessel. The second transducer beam is inclined in a direction which is generally perpendicular to the longitudinal axis of the vessel.

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.

Abstract: An ultrasound system for investigating a subject comprises a probe, a signal processing module, and an interconnecting cable. The probe includes an annular phased array transducer defining multiple signal processing channels. The signal processing module includes a controller, a transmitter, a receiver, delay circuitry, and a video section. Within the delay circuitry, each signal processing channel includes an inphase branch and a quadrature branch. Each branch includes an analog-to digital converter (ADC) and a delay first-in-first-out (FIFO) memory. Dynamically variable delays are implemented by varying the sampling and FIFO input rates relative to constant FIFO output rates. The variable clock rates are derived by switching between phase-staggered replicas of a master clock MCLK, which has a rate at the nominal center frequency of the ultrasound signal prior to sampling.