Surgery – Miscellaneous – Devices placed entirely within body and means used therewith
Reexamination Certificate
1999-01-11
2001-07-03
Gilbert, Samuel G. (Department: 3736)
Surgery
Miscellaneous
Devices placed entirely within body and means used therewith
Reexamination Certificate
active
06253770
ABSTRACT:
TECHNICAL FIELD
The present invention relates to medical instruments, and more specifically relates to medical instruments such as catheters having internal lumens and having sensors for detecting the position or orientation of the instrument.
BACKGROUND ART
Many minimally invasive medical procedures are performed using a catheter with a lumen. For example, in angioplasty, a balloon is inflated using saline solution conveyed through a lumen. In many cases it is desirable to inject medicine or radio-opaque dyes through a catheter's lumen. In some procedures, a tool is guided through the lumen. After the use of the tool is completed, the tool is retracted and may be replaced by another tool.
U.S. Pat. Nos. 5,480,422, 5,383,454, 5,295,486 and 5,437,277 and PCT application PCT/US95/01103, the disclosures of which are incorporated herein by reference, describe a few of the many types of position sensing tips for catheters. The position sensor in the catheter tip allows the physician to monitor location of the tip within the body without continually imaging the body and catheter. This capability can significantly reduce the radiation exposure of the patient and of the physician. For many position sensors size is an important factor. In some cases, the larger the sensor the more precise the position estimate. The maximum size of the position sensor typically is limited by the diameter of the catheter. In general, catheters with a smaller diameter are more flexible and can be used in a larger portion of the vascular system than catheters with a large diameter.
It is difficult to accommodate both a large lumen and a position sensor in the tip of a catheter, since the position sensor typically occupies almost the entire cross-section of the catheter.
DISCLOSURE OF THE INVENTION
It is an object of one aspect of the present invention to provide a catheter or other similar medical probe having both a position sensor at its tip and a large lumen.
A catheter according to one aspect of the invention includes a body defining a lumen and further includes a sensor such as a position sensor mounted to the body at a sensor location. Typically, the body and lumen are elongated, and the sensor location is adjacent the distal tip of the body. The catheter is adjustable between two configurations. In a first configuration, the lumen is constricted and/or obstructed by the sensor and the catheter has a first diameter at the sensor location. The first diameter at the sensor location may be similar to the diameter of the rest of the catheter. In a second configuration, the catheter is expanded at the sensor location so that the catheter has a second diameter at the sensor location, larger than the first diameter. In the second configuration, the constriction or obstruction of the lumen by the sensor is reduced or eliminated. Typically, the second diameter of the catheter at the sensor location is larger than the diameter of the rest of the catheter. As used herein with reference to an elongated body such as a catheter, the term “diameter” means the maximum dimension of the object transverse to the direction of elongation. The catheter body may be expanded at the sensor location by inflating a balloon in the body. Alternatively or additionally, a stylet is either inserted or removed from the lumen to affect a change in the shape of the lumen.
In another preferred embodiment of the present invention, a catheter including a body with a lumen and a position sensor has two configurations. In a first configuration, the lumen runs the entire length of the catheter but is obstructed by the position sensor at the tip of the catheter. In a second configuration, the distal end of tip of the catheter is moved aside so that it does not block the lumen. Preferably, the distal tip is shunted aside at a known orientation relative to the long axis of the catheter. Alternatively, the distal end of the tip of the catheter, which contains the position sensor is folded back onto the catheter. Preferably, the distal end of the tip is secured in a known position after such movement, for example, securing it in a socket.
Preferably, the catheter changes between configurations by inserting or by removing a stylet from the lumen. Alternatively, the change is achieved using a piezoelectric actuator.
In a preferred embodiment of the invention, the catheter is constrained in an obstructed configuration by a rigid sheath. When the sheath is moved from the catheter tip, the catheter changes configuration to the non-obstructed configuration. The catheter may change configuration due to its own resilience. That is, the catheter is resiliently biased to the non-obstructed configuration.
Another embodiment of the invention relates to a catheter having an elongated body defining an axis and an axially-extensive lumen. The catheter further includes a position sensor. The position sensor comprises at least one lateral sensing coil having windings which are not coaxial with the catheter. Stated another way, the windings of the lateral sensing coil do not lie in planes perpendicular to the axis of the catheter body, so that the voltage induced on the coil has components representing changes in magnetic field in a lateral direction orthogonal to the axis of the catheter body. In one embodiment, the lateral sensing coil is formed as at least two portions, which are spaced apart from one another along the long axis of the catheter. Thus, the lateral sensing coil obstructs the passage of a lumen only half as much as a coil formed in a single portion. Alternatively or additionally, portions of the lateral sensing coil may be disposed on opposite sides of the lumen, and may be spaced apart from one another in a direction transverse to the axis.
In another embodiment, the windings of the lateral sensing coil may extend around the lumen. Thus, the windings of the lateral sensing coil may be disposed in planes oblique to the lengthwise axis of the lumen. The lateral sensing coil as a whole is coaxial with the catheter, but the windings are not perpendicular to the axis of the coil. Alternatively, the lateral sensing coil a may be a thin coil oriented at an angle of less than 90 degrees to the long axis of the catheter.
Yet another aspect of the invention provides a probe comprising a body defining a lumen and a plurality of transducer assemblies mounted to said body around said lumen. Each transducer assembly includes one or more transducers such as coils or other transducers. The different transducer assemblies are sensitive to field components such as magnetic or electromagnetic field components in different directions. Each transducer assembly has a center of sensitivity representing the sensitivity of the transducer or transducers in such assembly. As further discussed below, the center of sensitivity of a transducer assembly is the locus of the midpoint of the sensitivity of the entire transducer assembly, i.e., the locus of a theoretical point transducer having the same response as the transducer assembly. Preferably, the centers of sensitivity of all of the transducer assemblies are disposed at a common point. Stated another way, when exposed to a field, all of the transducers will act cooperatively as a multidirectional point sensor disposed at the common point. The common point may be located within the lumen of the probe. As further discussed below, this simplifies the mathematics required to deduce values such as position and orientation of the probe from the signals obtained by the transducers.
Preferably, a first transducer assembly includes a first coil such as a helical coil having turns encircling the lumen and having a coil axis extending in a first direction codirectional with said lumen. A second transducer assembly includes a pair of second coils disposed on opposite sides of the lumen. The second coils have axes extending in a second direction transverse to said first direction. Preferably, the second coils are aligned with one another in the first direction but are offset from one another in a third direction transverse to s
Acker David E.
Fenster Maier
Millet Marcus J.
Biosense Inc.
Capezzuto Louis J.
Gilbert Samuel G.
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