Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-01-04
2001-02-13
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C029S025350
Reexamination Certificate
active
06186952
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to ultrasonic imaging catheters, and more particularly, to improved ultrasound imaging assemblies and methods of making same.
Intravascular imaging of blood vessels and surrounding tissues continues to be of great benefit in a wide range of medical fields. A particularly successful design for an intravascular imaging catheter is shown in FIG.
1
. The catheter
10
employs a rotatable imaging assembly
12
containing an ultrasound transducer
14
, where the assembly is attached to the distal end of a flexible drive cable. A flexible sheath
18
is inserted into a patient, and the drive cable and imaging assembly are inserted into the sheath. The transducer may be rotated in order to transmit an ultrasound signal and produce a video image by well-known techniques.
To produce images, it is desirable to have ultrasound signals
20
transmitted by the transducer pass through the sheath (as shown by arrow
22
) and reflect off of tissue or fluids. However, a portion of the ultrasound signals transmitted by the transducer typically are reflected by the sheath (as shown by arrow
24
). The amount of signal reflected typically is greatest when the angle of incidence between the signal and the sheath is about 90 degrees. Hence, as shown in
FIG. 1
, it is desirable to tilt the transducer relative to the sheath, thereby reducing the amount of reflected signal.
Angling the transducer typically involves forming a hole
16
in the assembly at the desired angle. However, the formation of an angled hole, particularly in such a diminutive assembly, presents difficulties. For example, angled holes typically have irregularities caused by the hole formation technique. The transducers often are placed and affixed by hand, which can lead to variations in transducer alignment between otherwise identical assemblies.
It is desirable, therefore, to provide imaging assemblies with firmly affixed transducers positioned at the proper angle relative to the sheath. It also is desirable to provide imaging assemblies that are easier to manufacture, and have greater consistency from assembly to assembly.
SUMMARY OF THE INVENTION
The present invention provides exemplary ultrasound imaging assemblies and methods of making same. Imaging assembles of the present invention have a machined tilt transducer package to position the transducer at the proper angle, thereby reducing the amount of reflected ultrasound signal from the sheath, and to improve consistency from transducer assembly to transducer assembly.
In one exemplary embodiment of the present invention an ultrasound imaging assembly includes a housing having a distal end, a proximal end, and a longitudinal axis. The distal end defines a receptacle. The imaging assembly includes a transducer package having a central axis and an imaging surface positioned at a desired angle relative to the central axis. The transducer package is at least partially disposed within the receptacle so that the central axis is generally perpendicular to the longitudinal axis. Preferably, the imaging surface is not coaxial with the longitudinal axis. In this manner, the imaging surface is positioned to permit a relatively large percentage of the ultrasound signal to pass through a sheath surrounding the imaging assembly. The use of a transducer package having the central axis positioned generally perpendicular to the housing longitudinal axis further permits the use of receptacles that are generally perpendicular to the longitudinal axis. In this manner, assembly-to-assembly variations are reduced, due in part by eliminating the need to make angled holes in the housing.
In one aspect of the present invention, the imaging surface has a shape that is generally elliptical. In another aspect, the transducer package includes an annular array of transducer elements. It will be appreciated by those skilled in the art that the transducer package may include transducer elements and imaging surfaces having a variety of different shapes within the scope of the present invention.
In one particular aspect, the desired angle between the central axis and the imaging surface is between about 30 degrees and about 150 degrees, and more preferably, between about 75 degrees and about 105 degrees. In this manner, the imaging surface is positioned at the proper angle to permit the transmission of ultrasound signals through the sheath. Further, for a transducer package that has a central axis generally perpendicular to the housing longitudinal axis, the angle between the longitudinal axis and the imaging surface is between about +60 degrees and about −60 degrees.
In one aspect, the housing includes stainless steel and may be plated with an electrically conductive material. The housing may be plated, for example, with gold, silver, gold over nickel over copper, and the like. Preferably, the housing proximal end is adapted to be coupled to a drive cable. In this manner, the imaging assembly may be rotated during operation thereof.
In another aspect, the receptacle is a generally cylindrical shaped receptacle having an inner wall. Preferably, the transducer package is disposed within the receptacle to contact the inner wall. In this manner, tight tolerances can be maintained to help reduce or eliminate unwanted transducer package movements within the receptacle.
In one aspect, the transducer package includes at least one matching layer operably attached to a transducer element. Alternatively, the transducer package includes a transducer element operably attached to and between a matching layer and a backing layer. It will be appreciated by those skilled in the art that a plurality of matching layers, or no matching layer, may be used within the scope of the present invention. In one particular aspect, the backing layer is electrically conductive. Alternatively, the backing layer is electrically nonconductive.
In still another aspect, the imaging assembly further includes a potting well located in the distal end. The potting well is adapted to receive an electrically conductive material so that the material is in contact with the transducer package, and preferably in contact with the backing layer.
The present invention further provides an exemplary ultrasound imaging catheter. The imaging catheter includes an imaging assembly, ostensibly as previous described, and a drive cable coupled to the proximal end.
The invention also provides exemplary methods of making an ultrasound imaging assembly. In one exemplary method, a first transducer package is provided having an imaging surface. A cutting device is provided and the first transducer package is positioned so that the imaging surface is at a desired angle relative to the cutting device. The method includes cutting the first transducer package with the cutting device to form a second transducer package having a central axis. The central axis is at the desired angle relative to the imaging surface. The method includes providing a housing having a distal end, a proximal end and a longitudinal axis, with the distal end defining a receptacle. The second transducer package is positioned to be at least partially disposed within the receptacle so that the central axis is generally perpendicular to the longitudinal axis. In this manner, the second transducer package has a machined angle, thereby permitting use of a receptacle that is generally perpendicular to the longitudinal axis. In one aspect, the desired angle between the central axis and imaging surface is between about 30 degrees and about 150 degrees. Alternatively, the desired angle is between about 75 degrees and about 105 degrees.
In one aspect of the present invention, the cutting device is selected from a group of cutting devices consisting of a cutting blade, a drill such as a core drill, a laser, an end mill, and the like. In another aspect, the receptacle and second transducer package are generally cylindrical. In still another aspect, the second transducer package is generally cylindrical and the imaging surface is gene
Bautista Richard A.
Mamayek Donald S.
White David A.
Imam Ali M.
Lateef Marvin M.
Sci-Med Life Systems, Inc.
Townsend and Townsend / and Crew LLP
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