Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-10-17
2003-07-15
Jaworski, Francis J. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S466000
Reexamination Certificate
active
06592526
ABSTRACT:
FIELD OF INVENTION
This invention relates to improvements in devices for intravascular ultrasound (IVUS) guided catheter systems.
BACKGROUND OF INVENTION
Intravascular ultrasound is a rapidly evolving imaging technique most commonly employed in coronary and iliofemoral arteries. The technique has the potential to facilitate the study of aneurysm progression, atherosclerosis or dissection and to outline the effect of endovascular intervention in more detail than angiography.
The presently used intravascular ultrasound systems fall into two categories: stationary electronic systems and mechanically driven rotating transducer systems. In both systems, an acoustic element or transducer is used to transmit a signal, which impinges upon, and reflects from, surfaces of different acoustic densities, which the signal encounters. An acoustic transducer receives the reflected wave. These data are sent to a processing system via an electrical cable where they are manipulated and displayed as an image. The systems are mounted to catheters, or axially elongate structures, which are routed through body lumens such as arteries to reach the site of imaging.
The non-rotating or stationary catheter of the stationary electronic system houses an array of small acoustic elements, which are positioned cylindrically at the catheter tip. After positioning the catheter in a vessel, body lumen or cavity, subgroups of acoustic elements may together generate an echo image. The spacing between the acoustic elements in the transducer array creates areas where the acoustic signal is neither transmitted nor received. When the data is processed, gaps of missing information occur, resulting in a poor quality image. The advantage of the stationary electronic system is that the catheter is very flexible and a central lumen is available for guidewire insertion. No distortion of the image, due to inhomogeneous mechanical rotation, is present. The stationary catheters are reliable and inexpensive but produce a poor quality image.
The mechanical intravascular ultrasound-imaging catheter comprises a mechanically rotating catheter shaft with a single ultrasound transducer. Either the acoustic element rotates or the acoustic element is stationary and a mirror rotates. In this manner, the acoustic signal is transmitted and received in a continuous 360-degree sweep. There are no gaps in the data and a higher quality image results. Realizing a driving mechanism while keeping the catheter fully flexible and steerable as well as miniature are challenging problems. Distortion of the image due to an unequal rotation of the element or mirror at the catheter tip is a limitation of these systems. Advantages of the mechanical probes include high-resolution imaging and absence of near field artifact. The mechanically rotating devices produce an acceptable image but are unreliable and expensive.
Both stationary electronic systems and mechanical systems typically operate with acoustic frequencies from 10 to 30 MHz.
Medical interventions are often performed using endovascular techniques. These interventions include balloon dilatation, atherectomy, stent or device placement and removal, drug delivery, thrombolytic therapy, thrombectomy, vessel irradiation, embolic device delivery and thermal therapy by radio waves or microwaves. Guidance of these endovascular interventions is preferably accomplished using intravascular ultrasound imaging.
The present invention, using a solid-state actuator, is more reliable and less expensive than the rotating catheters with a single acoustic transducer. It can also easily have a central lumen for instrumentation or for a guidewire. In addition, the present invention produces a higher resolution image with fewer gaps in the information than the stationary imaging catheters. This invention creates a high-resolution ultrasound image with higher reliability and less expense than is currently available. This invention has the ability to generate real-time three-dimensional ultrasound images of the region surrounding the acoustic transducers.
Another significant advantage of the present invention is its ability to navigate tortuous vasculature in order to reach the site of the lesion in the body vessel or lumen. It is, because of its greater flexibility, useful in catheters used to treat lesions of the cerebrovasculature or distal coronary circulation. Interventional devices, delivering therapies such as atherectomy, thrombectomy and irradiation, stent placement or removal, thrombogenic therapy and thrombolytic therapy, guided by this high-resolution ultrasound system, offer improved guidance and precision of placement as well as flexibility at potentially reduced cost and higher reliability than that obtainable from rotating shaft devices. Thus, this invention fills a market demand for a high resolution, reliable and inexpensive imaging and therapeutic catheter.
SUMMARY OF INVENTION
The present invention is a catheter comprising an array of ultrasound transducers and actuators along with signal processing, display, and power subsystems. The actuators on the catheter cause the array to oscillate. This allows the array to produce more imaging points of the object to be viewed than a non-rotating or a stationary array. Additional computer processing of the ultrasound data produces an image with a higher resolution than images produced from data from a non-oscillating transducer array.
The present invention comprises a catheter, or axially elongate structure, which has a distal tip and a proximal end. The catheter optionally comprises a central lumen or a guidewire tip. The central lumen is often used for guidewire passage. It may also comprise additional lumens for purposes such as balloon inflation and deflation, stent deployment, device retrieval, contrast media or material injection, electromagnetic emissions and drug injection or removal. The distal tip comprises an array of at least one transducer for transmitting ultrasound energy radially outward, an array of at least one transducer for receiving ultrasound signals, and one or more actuators. The transmitting and receiving transducers may optionally be the same physical entity. The transmitting and receiving transducers are electrically connected to the proximal end of the catheter by a transmission line, cable or wire bundle, which is electrically connected to a decoder, a power generator, and a display instrument. The actuators are also electrically connected to the proximal end of the catheter with a transmission line, cable or wire bundle, which is electrically connected to a power supply. The ultrasound transducer array on the distal tip of the catheter transmits and receives ultrasound signals, which are processed by a computer to create an image of the object subjected to the ultrasound signals.
The transducer array, located near the distal tip of the catheter, rotates clockwise and then counterclockwise either with the rest of the catheter or, preferably independent of the catheter. The array may be rotated through an angle equal to or less than 360 degrees. Most advantageously, the array is rotated sufficiently to fill in the information gaps but not more than required to minimize the requirements of the actuator and linkages. The array is then capable of rotating backwards the same amount. The net motion is a rotating oscillation or a vibration. The oscillating array may be optionally covered with a non-oscillating shield. Preferentially, the array will be rotated much less than 360 degrees so multiple transducers are required in the array to maintain a full field of view.
In one embodiment, the distal tip of the catheter comprises an imaging array that is directed forward as well as the imaging array that is directed radially outward. The forward directed array allows for acquisition of additional information on the vessel distal to the catheter.
The present invention does not continually rotate. It vibrates rotationally in the same manner as an agitator to gather data to fill in the missing information between array elements. The rotating
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