Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2003-05-05
2004-12-21
Robinson, Daniel (Department: 3742)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S407000
Reexamination Certificate
active
06834201
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an apparatus for navigating medical devices within the body to sites of treatment delivery, and methods of using this apparatus to achieve this navigation. More specifically, this invention relates to the use of a magnetic field from an MR imaging device to navigate a magnetic medical device within the body.
BACKGROUND OF THE INVENTION
The need for improved surgical navigation techniques stimulated the development of magnetic stereotaxis as a novel means for guiding a surgical implant, such as a catheter, along nonlinear paths within a body part. In particular, it is useful in intraparenchymal applications within the brain, where linear stereotactic techniques (either framed or frameless) do not permit the probe to follow single-pass curvilinear paths to a target location deep within the brain, as first taught by Howard et al. in U.S. Pat. No. 4,869,247 incorporated herein by reference. Howard et al. subsequently taught magnetic stereotactic techniques for volume-contoured therapy delivery within the brain and elsewhere in the human body in succeeding U.S. Pat. Nos. 5,125,88, 5,707,334, and 5,779,694 incorporated herein by reference. Advanced versions of magnetically guided surgical systems capable of performing magnetic stereotactic procedures in the brain and in other body parts have been disclosed in U.S. patents by Werp et al., U.S. Pat. No. 5,9331,818; Blume et al., U.S. Pat. No. 6,014,580; Werp et al., U.S. Pat. No. 6,015,414; Ritter et al., U.S. Pat. No. 6,128,174; and Blume et al., U.S. Pat. No. 6,157,853. In all of these approaches, as well as in any of the other known techniques for magnetic manipulation of a probe mass or implant located within the body (see Gillies et al., “Magnetic manipulation instrumentation for medical physics research,”
Review of Scientific Instruments
, pp. 533-562 (USA 1994)), incorporated herein by reference, the controlled movement of the probe mass or implant is actuated by a magnetic field created external to the body. In all such arrangements the magnetic component of the implant (typically located at the tip of a catheter) is a passive ferromagnetic or permanent magnetic element of a geometry consistent with that of the catheter's form and function, and within which there either exists or can be made to exist, adequate magnetic moment to create the forces and torques needed to steer and/or guide the implant within the body part into which it has been inserted.
Magnetic stereotaxis is particularly useful for navigation of medical devices throughout body tissues, cavities, and vessels. Discussion of applications to catheter navigation within the chambers of the heart for electrophysiologic mapping and ablation can be found in Hall et al., U.S. patent application Ser. No. 09/405,314, incorporated herein by reference. Disclosure of navigation of catheters within the myocardial tissue of the heart can be found in Sell et al., U.S. patent application Ser. No. 09/398,686, incorporated herein by reference. Removal of tissues from body lumens and cavities via magnetic navigation of atherectomy tools is disclosed in Hall et al., U.S. patent application Ser. No. 09/352,161, incorporated herein by reference. Catheters for magnetic navigation within the blood vessels of the brain and other body parts are disclosed in Garibaldi, U.S. patent application Ser. No. 60/153,307, incorporated herein by reference.
Four inherent limitations to this general design of magnetic stereotaxis system are the following. First, it is generally unsafe to perform magnetic resonance (MR) imaging studies during or after a magnetic stereotaxis procedures in which the magnetic element of the implant is still resident within the patient, as might be contemplated in situations where updated MR data might be needed for ongoing magnetic stereotaxis navigation requirements. This is because the large fields intrinsic to all types of MR scanners (either standard bore-type systems or the lower-field interventional-style systems) are large enough to cause otherwise uncontrolled displacement of the implant within the patient. The nature of this particular problem is discussed in the broader context of MR-driven forces on implants, by Planert et al., “Measurements of magnetism-related forces and torque moments affecting medical instruments, implants, and foreign objects during magnetic resonance imaging at all degrees of freedom,”
Medical Physics
, pp. 851-856 (USA 1996) and by Manner et al., “MR Imaging in the presence of small circular metallic implants,”
Acta Radiological
, pp. 551-554 (Denmark 1996), the disclosures of both of which are incorporated herein by reference.
A second limitation of the existing art is that relatively complex arrangements of magnetic field sources external to the patient must be assembled and controlled in order to carry out magnetic stereotactic movement of the implant. A single static background field is virtually always inappropriate for effecting controlled movement of the magnetic element in the implant used in existing magnetic stereotaxis procedures. A third limitation, related to the second, is that a magnetic element left in the brain or another body part can create a significant imaging artifact when that body part is imaged by an MR scanner, most typically rendering that imaging data set useless or of greatly reduced diagnostic and therapeutic value to the clinician and patient.
A fourth limitation is that appreciably and clinically precious time could be lost when carrying out a sequential and reciprocal process of conducting a magnetic stereotaxis procedure that must be interleaved with intra-operative MR imaging studies for diagnostic, therapeutic or navigational purposes. These limitations are not traversed by Kucharczyk et al. in their U.S. patent application Ser. No. 09/174,189 and in their International Application No. PCT/US99/24253, (the disclosure of both of which are incorporated herein by reference), which teach means for serial and reciprocal movement of the patient from a magnetic stereotaxis system to an MR scanner for purposes of updating the imaging information used for the reference portion of the magnetic stereotaxis procedure.
A more nearly ideal situation would arise if it were possible to integrate the form and function of a MR scanner and a magnetic stereotaxis system in such a way that magnetic stereotaxis procedures could be carried out within an MR scanner (or vice versa), and all done in such a way that the form and function of the MR scanning process would not interfere with those of the magnetic stereotaxis process, but that the respective forms and functions would instead complement and/or enhance each other. The subject of the present invention is a means and technique that accomplishes this goal and circumvents the existing limitations by incorporating a triaxial arrangement of miniature electromagnets as the magnetic element at the tip of the medical device or catheter. By externally regulating the electrical currents that pass through each of the independent coils, the torque and force on the tip of the medical device or catheter can be made to react to a static magnetic field of a MR scanner in such a way that the tip of the medical device or catheter can be guided along a preferred path to reach a target location within a brain or other body part. The resulting means and technique will thus exhibit all of the advantages of conventional magnetic stereotaxis (primarily the ability to navigate the medical device or catheter along complex curvilinear paths), while incorporating the further advantages of rapid sequential MR imaging of the patient, without introducing imaging artefacts on the MR images, since imaging is performed during periods when no currents flow through the triaxial coil components.
Medical devices with one or more miniaturized coils on them have been disclosed for a variety of other purposes, but none have been designed for use as the actuator in a combined magnetic stereotaxis and MR imaging process such as the type that is the subje
Broaddus William C.
Garibaldi Jeffrey M.
Gillies George T.
Hastings Roger N.
Harness & Dickey & Pierce P.L.C.
Robinson Daniel
Stereotaxis, Inc.
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