A wide variety of minimally invasive surgical procedures have been developed which employ catheters, endoscopes, or other similar devices that can be navigated remotely from their distal ends. The catheter, endoscope or other medical device is manipulated through the tissue or through an existing body lumen or cavity using a guide wire or other mechanical means. Examples of such procedures include the treatment of aneurysms, arterial ventricular malformations, atrial fibrillation, ureteral stones, and investigations of lumen such as sigmoidoscopies and colonoscopies, ERCP's; and biliary duct examinations. While these procedures are highly beneficial to the patient, they are difficult and time consuming for the physician. Some procedures can only be performed by the most skilled surgeons.
Several attempts have been made to use magnets to assist in such surgeries, as documented in "A New Magnet System for "Intravascular Navigation`," Shyam B. Yodh et al., Med. And Biol. Engrg., Vol. 6, pp. 143-147 (1968); "Magnetically Controlled Intravascular Catheter," John Alksne, Surgery, Vol. 61, no. 1, 339-345 (1968); "The `Pod`, a New Magnetic Device for Medical Applications," E. H. Frei et al., in Proceedings of 16th Ann. Conference on Engineering in Medicine and Biology, Vol. 5, Nov. 18-20, 1963, pp. 156-157; "Magnetic Propulsion of Diagnostic or Therapeutic Elements Through the Body Ducts of Animal or Human Patients," U.S. Pat. No. 3,358,676, issued Dec. 19, 1967 to E. H. Frei et al.; "Selective Angiography with a Catheter Guided by a Magnet," H. Tillander, IEEE Transactions on Magnetics, Vol. Mag-6, No. 2, 355-375 (1970); and "Cerebral Arterioveneous Malformations Treated with Magnetically Guided Emboli," Jack Driller et al., in Proc. of 25th Ann. Conf. On Engineering and Biology, Vol. 14 (1972), p. 306.
For various reasons these previous attempts at magnetically assisted surgery have not proven to be successful, nor are they widely used. One reason has been the inability of the previous systems to adequately guide the probes within the vessels, partly for mechanical and hydrodynamic reasons, partly from the lack of adequate computer and control technology, and partly because of an inability to provide adequate real time imaging for the procedures. Because of the small size of the vessels to be navigated, extremely high resolution and flexibly moveable fluoroscopes are needed to provide adequate imaging. These fluoroscopes are large instruments. Even now, accessibility of adequate imaging in the presence of the large magnets needed to move small magnetic guiding "seeds" on medical devices is difficult.
Systems have been disclosed for magnetic guidance of catheters and guidewires to facilitate navigation of difficult vascular turns. An example of such a system is provided in U.S. utility patent application Ser. No. 09/020,934, filed Feb. 9, 1998, entitled "Method and Apparatus Using Shaped Field of Repositionable Magnet to Guide Implant," incorporated by reference herein in its entirety. Other effective magnetic surgical systems have required relatively large magnets. Often, superconducting magnets with associated cooling systems are used to generate the most effective magnetic fields, and two magnets for each spatial direction have been provided for a total of six magnets, each having an associated cooling system. Such a system is disclosed in U.S. patent application Ser. No. 08/920,446, filed Aug. 29, 1997, entitled "Method and Apparatus for Magnetically Controlling Motion Direction of a Mechanically Pushed Catheter," incorporated by reference herein in its entirety.
Imaging means can be used in conjunction with magnetically guided surgery. An example of such a system is described in U.S. utility patent application Ser. No. 09/020,798, filed Feb. 9, 1998, entitled "Device and Method for Specifying Magnetic Field for Surgical Applications," incorporated by reference herein in its entirety. While magnetically guided surgery with such systems is practical, the sheer bulk and size of their magnetic systems results in less accessibility of the operating region of the patient than a surgeon might prefer. Also, imaging equipment (such as X-ray equipment) for observing the operating region has been fixed to the magnetic system assembly, or otherwise been immobile or of limited mobility relative to the magnets and/or the patient. This relative immobility tends to reduce the ability of the surgeons to see the medical operating device in the patient, making the operation somewhat more difficult for the surgeon and somewhat riskier for the patient than might otherwise be the case. Another difficulty with using magnetic systems for these purposes is that the conventional fluoroscopes cannot be used in magnetic fields of any significant magnitude. It would therefore be desirable to provide an apparatus for magnetically-assisted surgery that provides flexibility of both the imaging and of the magnetic field application.
A difficulty associated with magnetic guidance is that relatively large magnetic fields are needed to guide the small magnets that can fit within the small vessels and body lumens. The large superconducting coils employed in previous systems to provide these relatively large magnetic fields put huge amounts of energy into the fields. Because of the tendency for the coils to quench if ramped (powered) up or down too rapidly, the rate at which current can be applied or removed from the coils is limited, even with advantageous ramping methods such as the "constant power ramp." See U.S. patent application Ser. No. 08/921,298, filed Aug. 29, 1997, entitled "Method and Apparatus for Rapidly Changing a Magnetic Field Produced by Electromagnets," incorporated by reference herein in its entirety. The distance between the coil and the operating region is also a factor in ramping time, and thus it is desirable to provide a system having coils located and sized so as to optimize both the "openness" described above in terms of the accessibility to the surgeon of an operating region of a patient, and the rapidity of field directional changes.
Unless otherwise noted, all referenced issued patents, patent applications, and other documents are hereby incorporated by reference in their entirety.