Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1999-07-20
2001-11-13
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S467000
Reexamination Certificate
active
06315732
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates generally to the field of ultrasound imaging, and in particular, to the imaging of body lumens with ultrasound imaging catheters.
Physicians make use of catheters today in medical procedures that are best performed by gaining access into interior regions of the body. For example, in electrophysiological therapy, ablation is used to treat cardiac rhythm disturbances. Such a therapy may be used, for example, to treat atrial fibrillation by forming long, thin lesions of different curvilinear shapes in heart tissue.
During these procedures, a physician steers a catheter through a vein or artery into the interior region of the heart that is to be treated. An ablation element carried on the distal end of the catheter is positioned near the tissue that is to be ablated. For such treatments, the delivery of ablating energy must be closely governed to avoid incidence of tissue damage and coagulum formation. Further, the ablation catheters must be precisely positioned adjacent to and preferably in contact with the tissue to be treated, to ensure the lesions are properly located.
Physicians and staff performing diagnostic and therapeutic procedures, such as electrophysiological therapy, typically require an imaging system to assist them in positioning the ablation catheter. Mini-transesophageal echocardiography (mini-TEE) probes are available, however, these probes must be swallowed or inserted down the patient's throat. Such probes are poorly tolerated by patients unless they are fully anesthetized. Further, these probes can be rather large (i.e., 20 French in diameter), use complex transducer configurations and are costly enough to discourage their disposal after a single use.
Alternatively, the use of ultrasound imaging systems, and in particular ultrasound imaging catheters, would be particularly useful in helping physicians monitor the positioning of ablation catheters. It is desirable, therefore, to have an ultrasound imaging catheter small enough to enter narrow and tortuous regions of the patient's vascular system. It also is desirable if such imaging systems were easy to operate and cost efficient to encourage their disposal after use.
SUMMARY OF THE INVENTION
The present invention provides ultrasound imaging catheters, systems and methods for their use. Catheters and systems of the present invention will be particularly useful to monitor the positioning of ablation catheters. Catheters and systems of the present invention provide a relatively simple and inexpensive apparatus compared to alternative monitoring techniques, such as mini-TEE probes.
In one embodiment, the present invention provides an imaging catheter comprising a catheter body having a distal end, a proximal end and a longitudinal axis. A transducer is rotatably coupled to the catheter body distal end. The transducer has an axis of rotation that is different from the catheter body longitudinal axis. Preferably, the transducer axis of rotation is generally perpendicular to the longitudinal axis. In this manner, the transducer rotates to produce images in an imaging plane that is generally parallel to the longitudinal axis. Such a configuration provides an exemplary side-looking imaging catheter.
In one aspect the catheter body has a diameter that is less than about 16 French. Catheters of such dimensions are sufficiently small enough to enter tortuous regions of a patient's vasculature. In another aspect, the transducer comprises PZT. The transducer also may comprise piezoplastics, piezocomposites, piezoceramics (e.g. PZT) and the like.
In one particular aspect, the transducer is rotatably coupled to the distal end to permit 360 degree rotation of the transducer about the transducer rotational axis relative to the distal end. In such an arrangement, the transducer is rotated to produce ultrasound images throughout an imaging plane without the need to rotate the catheter body. In another particular aspect, the transducer is rotatably coupled to the distal end to permit up to about 180 degree rotation of the transducer about the rotational axis relative to the distal end.
In one aspect, the transducer defines a face that is generally elliptical in shape, although other transducer shapes are possible within the scope of the present invention. In another aspect, the face has a major axis length that is greater than a diameter of the catheter body. In this manner, the transducer face major axis preferably is positioned generally parallel to the catheter body longitudinal axis. The transducer can be rotated up to about 180 degrees of rotation using a wiper-like or teeter-totter type of rotational movement.
In another aspect, the transducer comprises an annular array of transducer elements. In one aspect, the annular array defines a face that is generally elliptical in shape. Alternatively, the annular array defines a face that is generally circular in shape. The face may be generally flat or have a spherical or other curvature. Exemplary annular arrays for use in the present invention are further described in U.S. patent application Ser. No. 09/017,581, entitled “Annular Array Ultrasound Catheter,” filed Feb. 3, 1998, and assigned to the assignee of the present invention, the complete disclosure of which is incorporated herein by reference.
In one aspect, the imaging catheter further includes a drive cable and a gear mechanism disposed within a working lumen of the catheter body. The drive cable is coupled to the transducer and to the gear mechanism. The drive cable and gear mechanism are adapted to rotate the transducer. In this manner, the drive cable and gear mechanism rotate the transducer, thereby eliminating the need to rotate the catheter body. In another aspect of the invention, the imaging catheter further includes a housing rotatably coupled to the distal end. The transducer is mounted within the housing. In such an embodiment, the transducer is rotated relative to the distal end by rotating the housing. Alternatively, the imaging catheter comprises a housing operably attached to the distal end with the transducer being rotatably coupled to the housing.
In another embodiment of the present invention, an imaging catheter is provided comprising a catheter body as previously described. The catheter further includes a plurality of transducer elements configured in an annular array. The annular array is rotatably coupled to the catheter body distal end, and has an axis of rotation that is at a non-zero angle relative to the catheter body longitudinal axis. Preferably, the annular array axis of rotation is generally perpendicular to the longitudinal axis.
In still another embodiment of the present invention, an imaging catheter includes a catheter body having a distal end, a proximal end and a longitudinal axis. A transducer is rotatably coupled to the distal end to permit up to about 180 degrees of rotation about an axis of rotation that is not coaxial with the longitudinal axis. More preferably, the transducer axis of rotation is generally perpendicular to the catheter body longitudinal axis. In one aspect, the transducer defines a face that is generally parallel to the longitudinal axis during a period of non-rotation. Preferably, the transducer is adapted to rotate so that the face creates an angle with the longitudinal axis that is between about +90° and about −90°.
The present invention further provides imaging catheter systems. In addition to an imaging catheter as previously described, the system includes a controller operably attached to the imaging catheter. The controller operates to display ultrasound images from signals received from the transducer and provides power to the imaging catheter. Such a system is particularly useful for the monitoring of accurate positioning of an ablation catheter prior to and/or during ablation.
The invention further provides exemplary methods of imaging a body lumen. One particular method includes the steps of providing an imaging catheter comprising a catheter body and a transducer coupled to the
Belef W. Martin
Beyhan Niyazi
Mamayek Donald S.
Suorsa Veijo T.
Lateef Marvin M.
Patel Maulin
Sci-Med Life Systems, Inc.
Townsend and Townsend / and Crew LLP
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