Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
2001-10-24
2004-05-11
Layno, Carl (Department: 3762)
Surgery
Diagnostic testing
Cardiovascular
C600S508000
Reexamination Certificate
active
06735465
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to systems and methods for guiding and locating diagnostic or therapeutic elements on medical instruments positioned in a body.
BACKGROUND OF THE INVENTION
The use of invasive medical devices, such as catheters and laparoscopes in order to gain access into interior regions or spaces of the body for performing diagnostic and therapeutic procedures is well known. In such procedures, it is important for a physician or technician to be able to precisely position the device, including various functional elements located on the device, within the body in order to make contact with a desired body tissue location.
For example, the need for precise control over the positioning of an invasive catheter or surgical probe is especially critical during procedures for testing or ablating myocardial tissue within the beating heart for treating cardiac rhythm disturbances. To perform such a procedure, the physician typically steers a catheter through a main vein or artery into the interior region of the heart that is to be treated. The physician then manipulates the catheter in order to place one or more electrodes carried on the distal portion and/or tip of the catheter into direct contact with the endocardial tissue. The physician may use the electrode(s) to examine the propagation of electrical impulses in heart tissue in order to locate aberrant conductive pathways and to identify the arrhythmia foci. This procedure is called mapping. One such mapping technique is to introduce multiple-electrode array structures carried on the distal end of an invasive catheter into the heart through venous or arterial access. Information obtained from the various electrode elements (operating in either unipolar or bipolar fashion), combined with externally obtained electrocardiogram signals, can be externally processed to detect local electrical events and identify likely arrhythmia foci locations within the heart.
Using the same, or a different catheter or surgical probe device, the physician may then direct energy from one or more distally carried electrode(s) through the myocardial tissue either to an indifferent electrode (in a unipolar electrode arrangement) or to an adjacent electrode (in a bipolar electrode arrangement) to ablate the tissue locations containing the aberrant conductive pathways in order to restore a healthy heart rhythm. This procedure is called ablation therapy.
In theory, minimally invasive mapping techniques allow a physician to identify a target ablation site within the heart, prior to the actual ablation procedure and without the complications of open heart surgery. In practice, however, current minimally invasive mapping techniques do not ensure that an identified target site will be accurately or easily relocated. Accordingly, it would be desirable to provide physicians with the ability to accurately return to a target site in the heart that was previously identified using minimally invasive mapping techniques.
One proposed solution to the problem of identifying and relocating target sites in the heart site is to add a navigation system that is centered outside of a patient's body, in order to provide an “absolute” reference frame that is unaffected by the absolute location of the patient. One such system, disclosed in U.S. Pat. No. 5,391,199 to Ben-Haim (“the '199 patent”), combines an electrophysiological mapping system and a navigational system centered on a reference frame outside of the body in order to attempt to increase a physician's ability to return to an identified target site. The mapping system provides data on points of interest at sites within the body. The exterior navigational system provides data on the “absolute” location of the site with respect to an external reference frame of the site as these points of interest are identified. This is accomplished by placing one or more location sensors adjacent mapping elements on the mapping probe. As taught in the '199 patent, combining the “location information” with “local information” for a sufficient number of sites will provide a three dimensional “map” of data points corresponding to the three-dimensional structure of the heart or other organ.
One problem, however, occurs with mapping catheters having relatively small mapping element carrying structures, e.g., 3-D catheter structures that are 40 mm in diameter or smaller. In these cases, it is difficult to place location elements adjacent all of the mapping elements, and sometimes even adjacent a select few of the mapping elements. Thus, generating a three dimensional map is made difficult. Another problem occurs as a result of the discrete nature of the mapping elements. Oftentimes, critical information is missed between the mapping elements, resulting in a map that, although corresponding to the three-dimensional structure of the heart or other organ, does not accurately identify target sites.
SUMMARY OF THE INVENTION
The present invention provides for systems and processes for refining a registered map.
In a first aspect of the present invention, a method of mapping a body cavity of a patient is provided. The body cavity may be, for example, a heart chamber. A first probe carrying a plurality of mapping elements is positioned adjacent a plurality of locations along the body cavity. The first probe may include a 3-D catheter structure on which the plurality of mapping elements is carried. In one embodiment, the 3-D catheter structure is 40 millimeters or less in size. A second probe carrying a functional element is also positioned in the body cavity. The absolute position, within a three-dimensional coordinate system, of the functional element is determined. Also, the proximity of that functional element to each of the plurality of mapping elements is determined. Based on the absolute position of the functional element and the proximity of the functional element to the mapping elements, an absolute position within the coordinate system of the mapping elements is determined. A map is generated by detecting information local to the body cavity, with the mapping elements, and associating the local information to the absolute positions of the mapping elements. The functional element is then located adjacent a location on the body cavity between the plurality of locations. Here, the functional element of the second probe comprises a mapping element. Prior to locating the functional element adjacent the body cavity location, in one alternative, the first probe is removed from the body cavity. In another alternative, the first probe is maintained within the body cavity while locating the functional element adjacent the body cavity location. The absolute position of the mapping element of the second probe, within the coordinate system, is determined. Additionally, information local to the body cavity is detected using the mapping element, and the local information is associated to the absolute position of the mapping element in order to refine the map.
In an alternative procedure of the first aspect of the present invention, a first probe carrying a plurality of mapping elements are located adjacent a plurality of locations along the body cavity. A second probe carrying a mapping element is positioned in the body cavity. An absolute position within a three-dimensional coordinate system is determined for each of the plurality of mapping elements. A map is generated by detecting local information using the plurality of mapping elements and associating that information to the absolute positions of the plurality of mapping elements. The mapping element of the second probe is adjacent a location on the body cavity between the plurality of locations. An absolute position of the mapping element is determined, local information is detected using the mapping element, and the local information is associated to the absolute position of the mapping element in order to refine the map.
For either of the above-mentioned procedures, the refined map is stored in memory, the refined map is retrieved from memory, and th
Bingham & McCutchen LLP
Layno Carl
Sci-Med Life Systems, Inc.
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