U.S. patent application number 13/441366 was filed with the patent office on 2012-12-27 for open field system for magnetic surgery.
Invention is credited to Walter M. Blume, Francis M. Creighton, Jeffrey M. Garibaldi, Bevil J. Hogg, Rogers C. Ritter, Peter R. Werp, Charles Wolfersberger.
Application Number | 20120330089 13/441366 |
Document ID | / |
Family ID | 26804441 |
Filed Date | 2012-12-27 |
United States Patent
Application |
20120330089 |
Kind Code |
A1 |
Ritter; Rogers C. ; et
al. |
December 27, 2012 |
OPEN FIELD SYSTEM FOR MAGNETIC SURGERY
Abstract
A system of navigating a magnetic medical device within that
part of a patient located within an operating region of the system,
the system comprising magnets, and preferably electromagnets,
arranged to provide a magnetic field sufficient to navigate the
magnetic medical device within the operating region. There are
preferably three magnetic coils arranged in mutually perpendicular
planes such that their axes intersect in the operating region. The
magnetic coils are sized and arranged so that a patient can easily
access the operating region to allow virtually any portion of the
patient to be positioned within the operating region. The openness
of the magnetic system allows access to the operating region by a
bi-planer imaging system.
Inventors: |
Ritter; Rogers C.;
(Chalottesville, VA) ; Garibaldi; Jeffrey M.; (St.
Louis, MO) ; Wolfersberger; Charles; (Ferguson,
MO) ; Creighton; Francis M.; (St. Louis, MO) ;
Werp; Peter R.; (St. Louis, MO) ; Hogg; Bevil J.;
(St. Louis, MO) ; Blume; Walter M.; (Webster
Groves, MO) |
Family ID: |
26804441 |
Appl. No.: |
13/441366 |
Filed: |
April 6, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09842417 |
Apr 25, 2001 |
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13441366 |
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09211723 |
Dec 14, 1998 |
6241671 |
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09842417 |
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60107144 |
Nov 3, 1998 |
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Current U.S.
Class: |
600/12 |
Current CPC
Class: |
A61B 34/70 20160201;
A61B 6/0487 20200801; A61B 34/73 20160201; A61B 2034/733 20160201;
A61B 6/4441 20130101 |
Class at
Publication: |
600/12 |
International
Class: |
A61N 2/02 20060101
A61N002/02; A61N 2/10 20060101 A61N002/10 |
Claims
1-19. (canceled)
20. A system for navigating a magnetic medical device comprising a
plurality of magnet coils for applying a magnetic field in a
particular direction to orient a magnetic medical device within
that part of a patient located within an operating region of the
system in a selected direction, a plurality of magnet coils being
effective to controllably orient the medical device within
substantially the entirety of the operating region, said operating
region being positioned so that said part of the patient may be
located within the operating region without passing through any of
said magnet coils.
21. A system for navigating a magnetic medical device according to
claim 20, further comprising at least three magnet coils configured
and arranged in an open concave shell to provide a magnetic field
effective within the operating region to orient the magnetic
medical device in a selected direction within the operating
region.
22. A system according to claim 21, wherein the coils are arranged
in a generally hemispherically shaped shell.
23. A system according to claim 21, wherein the shell is mounted
for rotation about a vertical axis.
24. A system according to claim 20, wherein the plurality of magnet
coils are generally aligned along a plurality of oblique axes with
only a single one of said magnet coils being aligned along one of
said axes, and at least one of the magnet coils being aligned along
the others of said axes.
25. A system according to claim 20, wherein the magnet coils are
capable of providing a magnetic field of at least substantially 0.1
Tesla anywhere in an operating region of at least 50.8 mm by 50.8
mm by substantially 50.8 mm.
26. The system according to claim 20, wherein the operating region
has a volume of at least substantially 127 mm by substantially 127
mm by substantially 127 mm.
27. A system according to claim 20, wherein the magnet coils are
arranged and configured so that their axes intersect, and wherein
the coils are spaced sufficiently from the point of intersection to
accommodate a sphere centered on the point of intersection, with a
radius of at least 304.8 mm.
28. The system according to claim 21, further comprising a support
for the patient, and a moveable support for the shell so that said
shell may be reoriented about said patient support and patient.
29. A system according to claim 20, wherein said magnet coils are
positioned so that their respective near field lines are
substantially straight within the operating region.
30. A system for navigating a magnetic medical device within that
part of a patient located within an operating region of the system,
the system comprising: a patient support for supporting a patient,
and at least three electromagnet coils forming a magnet assembly
positioned above the plane of the patient support, being configured
and arranged to provide a magnetic field effective within the
operating region to navigate the magnetic medical device within the
operating region, the at least three electromagnet coils being
positioned above the plane of the patient support and arranged such
that the axes of the electromagnet coils intersect generally in the
center of an operating region of the magnet assembly; wherein the
patient support is movable and has a narrow portion that is sized
to fit within the magnet assembly to allow a portion of the
patient's body, up to and including a patient's chest, to be
positioned within the operating region of the magnet assembly.
31. A system according to claim 30, wherein the spacing of the
electromagnetic coils provide an opening of sufficient size such
that a patient's chest can be positioned within the operating
region.
32. A system according to claim 31, wherein the intersection of the
axes of the magnet is coiled is at least about 150 mm (six inches)
from each of the coils, but no more than about 375 mm (fifteen
inches) from each of the coils.
33. A system according to claim 31 wherein the electromagnet coils
are configured and arranged to be able to provide a magnetic field
of at least about 0.1 Tesla within an operating region which
operating region is spaced at least about 300 mm (twelve inches)
from each of the coils, to selectively orient the magnetic medical
device anywhere within the operating region.
34. A system according to claim 33, wherein the electromagnetic
coils are capable of providing a magnetic field of at least about
0.3 Tesla anywhere within the operating region.
35. A system according to claim 33, wherein the axes of the three
electromagnetic coils are mutually perpendicular.
36. A system according to claim 31, wherein the electromagnetic
coils are mounted in a shell having a generally concave shape.
37. A system for navigating a magnetic medical device within that
part of a patient located within an operating region of the system,
the system comprising: three magnets configured and arranged to
provide a magnetic field effective within the operating region to
navigate the magnetic medical device within the operating
region.
38. A system according to claim 37, wherein the magnets are
electromagnetic coils having intersecting axes.
39. A system according to claim 38, wherein the intersection of the
axes of the magnets is at least about six inches from each of the
coils, but no more than about fifteen inches from each of the
coils.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This Application is a divisional application of U.S. patent
application Ser. No. 09/211,723, filed Dec. 14, 1998, (incorporated
herein by reference), which claims priority of Provisional Patent
Application Ser. No. 60/107,144 filed Nov. 3, 1998, (incorporated
herein by reference).
FIELD OF THE INVENTION
[0002] This invention relates to a magnetic surgery system, and in
particular to an open magnetic surgery system that provides greater
access to the patient for imaging and other purposes.
BACKGROUND OF THE INVENTION
[0003] 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.
[0004] 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 December 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. (1972),
p. 306.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] 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.
[0009] Unless otherwise noted, all referenced issued patents,
patent applications, and other documents are hereby incorporated by
reference in their entirety.
SUMMARY OF THE INVENTION
[0010] The present invention provides an open system for navigating
a magnetic medical device within that part of a patient located
within an operating region of the system. Generally, the system
comprises a plurality of magnets configured and arranged to provide
a magnetic field effective within the operating region to navigate
the magnetic medical device within the operating region, while
providing access to the patent for imaging and other purpose.
[0011] The magnets are preferably electromagnetic coils, and more
preferably superconducting electromagnetic coils. The magnets are
preferably capable of generating a magnetic field of at least about
0.1 Tesla in an operating region of at least about two inches by
two inches by two inches, and more preferably in an operating
region of at least about five inches by five inches by five inches.
In a preferred embodiment, the magnets can generate a field of
about 0.3 Tesla in any direction within the operating region. The
operating region is preferably at least about twelve inches from
each of the magnets, such that the system can accommodate a sphere
having a radius of about twelve inches to provide sufficient room
for a patient and imaging apparatus.
[0012] Generally, a single magnet is arranged and configured to
provide a magnetic field along at least one of a plurality of
oblique axes extending through the operating region, and one or
more magnets are arranged and configured to provide a magnetic
field along each of the other of said oblique axes, said magnetic
fields being effective to controllably navigate the magnetic
medical device within substantially the entirety of the operating
region. Preferably there are three magnets in three mutually
perpendicular planes, arranged such that their axes converge in the
operating region, and more preferably they are arranged so that
their axes intersect in the operating region. The magnets are
arranged in an open configuration, i.e., the patient typically does
not have to extend through a magnet coil to reach the operating
region, as was required in previous magnetic surgery systems. The
coils are sized and positioned so that their respective near field
lines are substantially straight within the operating region.
[0013] The coils are preferably fixed relative to each other, but
may be moveable relative to the patient. The magnets are preferably
enclosed within a concave housing sufficiently large to accommodate
the patient and imaging devices, yet small enough to fit within the
conventional supports for imaging devices. In the most preferred
embodiment, the shell has a generally hemispherical shape, with an
inner diameter of at least about twenty-four inches and an outer
diameter of no more than about fifty inches. The generally
hemispherical shell is mounted so that its axis is at an angle
between vertical and horizontal and thus faces generally
downwardly, but so that the shell can be rotated about a generally
vertical axis.
[0014] To increase the flexibility of the system, there is
preferably an opening in the housing, aligned with one of the
coils, through which a portion of the patient's body can extend to
bring another portion of the patient's body into the system's
operating region. The system can include a patient support for
supporting and for moving the patient relative to the operating
region of the system.
[0015] The system further comprises an imaging system for providing
images of the operating region. The imaging system comprises at
least one, and preferably two imaging devices. Each imaging device
comprises an imaging plate and an x-ray imaging source. The imaging
plates are preferably ones that are minimally affected by magnetic
fields, such as amorphous silicon imaging plates. The imaging
devices are preferably fixedly mounted with respect to each other,
in mutually perpendicular directions to provide perpendicular
bi-planar imaging of the operating region.
[0016] The imaging devices are mounted on a movable support,
independently of the magnet coils. The support allows the imaging
devices to be moved about three axes, and may be, for example a
conventional C-arm support. This allows the imaging devices to be
moved relative to the operating region, to provide the surgeon the
most advantageous view of the procedure. The three axes of movement
of the imaging devices preferably intersect, and more preferably
they intersect in the operating region, and most preferably they
intersect at the same point where the axes of the magnets coils
intersect. This provides the greatest flexibility of imaging in the
operating region.
[0017] More specifically, the system of this invention provides for
navigating a magnetic medical device within that portion of a
patient within an operating region of the system. The system
includes a support for at least a portion of the patient. The
system also includes a magnet assembly including electromagnetic
coils arranged and configured so that the axes of the coils
converge, and a magnet mount holding the magnet assembly so that
the center of the operating region (i.e., the convergence of the
axes) is within the desired portion of the patient on the patient
support. An imaging assembly for providing an image of the
operating region comprises at least one imaging plate and an
imaging beam source mounted on an imaging support to be on opposite
sides of the operating region, and a mechanism for selectively
pivoting the support about three mutually perpendicular axes.
[0018] In the preferred embodiment, a total of three super
conducting magnets coils are configured so that each of their
central axes lies generally along an axis of an orthogonal
coordinate system having its origin approximately centered within
the operating region. The magnets are supported by a generally
hemispherical housing and each magnet is of sufficient strength to
provide a magnetic field in the direction of its respective central
axis having a generally consistent strength of about 0.3 Tesla
throughout substantially the entirety of the operating region. A
control adjusts the strength of the magnetic field of each of said
magnet coils to thereby controllably navigate the magnetic medical
device within that part of a patient within the operating
region.
[0019] The method of navigating according to this invention
includes applying a magnetic field to the magnetic medical device
in the operating region with at least three electromagnetic coils
contained within a magnet housing to navigate the medical device
within the operating region; and providing an image of the magnetic
medical device in the operating region with an imaging apparatus
comprising at least one imaging plate and an imaging beam source,
the imaging plate and imaging beam source being on opposite sides
of the operating region, with the imaging plate being positioned
between the operating region and the magnet housing. The imaging
plate and imaging beam source are movable about three mutually
perpendicular axes which extend through the operating region. These
axes preferably extend through the point of intersection of the
axes of the magnets.
[0020] The present invention also includes a method of determining
a distribution of ramping times for the electromagnetic coils in
the system. This method includes calculating for a selected
magnetic field magnitude and direction, the currents needed in each
coil to provide the selected magnetic field magnitude and direction
at a point in an operating region; estimating, for each of the
calculated currents, a ramping time required to reach the
calculated current; and repeating the current calculating step and
the ramping time estimating step for a plurality of different
points in the operating region, and for selected magnetic field
magnitudes and directions to obtain a distribution of ramping times
as a function of selected magnetic field magnitude and direction
for the system.
[0021] The present invention also includes a method of optimizing
the design of the system, comprising selecting a maximum ramping
time not to be exceeded by a selected percentage of navigational
direction changes of the magnetic medical device; determining a
distribution of ramping times; determining a percentage of ramping
times in the distribution of ramping times that the selected
maximum ramping time is exceeded; and modifying at least one
property of at least one of the electromagnetic coils, the at least
one property including at least one property selected from the
group consisting of coil radius, coil cross-sectional area, coil
distance from the operating region, and coil aspect ratio; and
repeating the computing, determining, and modifying steps until the
percentage of ramping times in the distribution of ramping times
that the selected minimum ramping time is exceeded is not more than
the selected percentage of navigational direction changes.
[0022] A magnetic resonance imaging system comprising an
electromagnet for generating a magnetic field in the vicinity of
the a body for making a magnetic resonance image of a portion of
the body and an x-ray image apparatus, comprising an x-ray image
source and an x-ray image plate, for making an image of the portion
of the body, at least the x-ray image plate being within the
magnetic field generated by the electromagnet.
[0023] Thus the system of the present invention provides for
effective magnetic guidance of magnetic medical devices within the
body for performing medical procedures. The system is capable of
providing magnetic fields of sufficient strength for orientation
and even movement of magnetic medical devices, within a
sufficiently large operating region to allow practical medical
procedures to be completed with magnetic assistance. However, the
magnets are arranged so that the operating region of the system can
be positioned in any portion of the body. The system provides open
access so that imaging plates can be interposed between the patient
and the magnets to provide high-quality images of the operating
region. The imaging apparatus can be moved independently of the
magnets to provide the best possible views of the operating
region.
[0024] These and other features and advantages will be in part
apparent and in part pointed out hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is an isometric view of a first embodiment of a
magnetic navigation system in accordance with the present
invention;
[0026] FIG. 2 is another isometric view of the system the first
embodiment in showing the positions of the magnetic coils and a
patient on the patient support;
[0027] FIG. 2A is an isometric view of the imaging assembly on the
C-arm structure of the system of the first embodiment;
[0028] FIG. 3 is an isometric view from the rear of the system of
the first embodiment;
[0029] FIG. 4 is a right side elevation view of the system of the
first embodiment, showing the range of angular motion of the
imaging system about a transverse horizontal axis;
[0030] FIG. 5 is a top plan view of the system of the first
embodiment showing a range of angular motion of the imaging system
about a vertical axis;
[0031] FIG. 6 is a front elevation view of the system of the first
embodiment showing a range of angular motion of an arcuate section
of the imaging assembly about a horizontal axis;
[0032] FIG. 7 is a left side elevation of the structure for
supporting the electromagnetic coils of the first embodiment;
[0033] FIG. 8 is a top plan view of the structure for supporting
the electromagnetic coils;
[0034] FIG. 9 is a vertical cross-sectional view of the structure
for supporting the electromagnetic coils, taken along the plane of
line 9-9 in FIG. 7;
[0035] FIG. 10 is a cross-sectional view of the structure for
supporting the electromagnetic coils, taken along the plane of
10-10 in FIG. 9;
[0036] FIG. 11 is a rear end elevation view of the electromagnetic
coils and the imaging system;
[0037] FIG. 12 is a left side elevation view of the electromagnetic
coils with a patient therein showing the magnetic field lines of
the axial coil, along with lines of constant magnetic field
strength;
[0038] FIG. 13 is a top plan view of a second embodiment of a
magnetic navigation system constructed according to the principles
of this invention;
[0039] FIG. 14 is a rear end elevation view of the magnetic
navigation system of the second embodiment;
[0040] FIG. 15 is a left side elevation view of the magnetic
navigation system of the second embodiment;
[0041] FIG. 16 is a front end elevation view of the magnetic
navigation system of the second embodiment;
[0042] FIG. 17 is a right side elevation view of the magnetic
navigation system of the second embodiment;
[0043] FIG. 18 is an isometric view of the magnetic navigation
system of the second embodiment;
[0044] FIG. 19 is an isometric view of the magnetic navigation
system of the second embodiment, showing the C-arm for supporting
the imaging apparatus in its neutral position;
[0045] FIG. 20 is an isometric view of the magnetic navigation
system of the second embodiment, showing the magnet assembly
retracted;
[0046] FIG. 21A is an isometric view of the magnetic navigation
system of the second embodiment, showing the C-arm rotated
+30.degree. about a transverse horizontal axis;
[0047] FIG. 21B is an isometric view of the magnetic navigation
system of the second embodiment, showing the C-arm rotated
-30.degree. about a transverse horizontal axis;
[0048] FIG. 22A is an isometric view of the magnetic navigation
system of the second embodiment, showing the c-arm rotated
+30.degree. about a vertical axis;
[0049] FIG. 22B is an isometric view of the magnetic navigation
system of the second embodiment, showing the C-arm rotated
-30.degree. about a vertical axis;
[0050] FIG. 23 is an isometric view of the magnetic navigation
system of the second embodiment, showing the C-arm rotated
90.degree. about the longitudinal horizontal axis;
[0051] FIG. 24 is an isometric view of the magnetic navigation
system of the second embodiment, showing the C-arm at a compound
angle;
[0052] FIG. 25 is an isometric view of the magnet assembly of the
second embodiment;
[0053] FIG. 26 is a top plan view of the magnet assembly of the
second embodiment;
[0054] FIG. 27 is a front elevation view of the magnet assembly of
the second embodiment;
[0055] FIG. 28 is a vertical cross-sectional view of the magnet
assembly of the second embodiment, taken along the plane of line
28-28 in FIG. 27;
[0056] FIG. 29 is an isometric view of the three electromagnet
coils comprising the magnet assembly of the second embodiment;
[0057] FIG. 30 is a top plan view of the three electromagnetic
coils comprising the magnet assembly of the second embodiment;
[0058] FIG. 31 is a front elevation view of the three
electromagnetic coils comprising the magnet assembly of the second
embodiment;
[0059] FIG. 32 is a right side elevation view of the three
electromagnetic coils comprising the magnet assembly of the second
embodiment;
[0060] FIG. 33 is a cross-sectional view of two of the
electromagnetic coils taken along the plane of line 33-33 in FIG.
31;
[0061] FIG. 34 is an isometric view of a third embodiment of a
magnetic navigation system constructed according to the principles
of this invention;
[0062] FIG. 35 is an isometric view of the magnetic navigation
system of the third embodiment, with the magnet assembly rotated
+30.degree.;
[0063] FIG. 36 is an isometric view of the magnetic navigation
system of the third embodiment, with the magnet assembly
retracted;
[0064] FIG. 37 is an isometric view of the magnet assembly of the
third embodiment;
[0065] FIG. 38 is a top plan view of the magnet assembly of the
third embodiment;
[0066] FIG. 39 is a front elevation view of the magnet assembly of
the third embodiment;
[0067] FIG. 40 is a vertical cross-sectional view of the magnet
assembly of the third embodiment, taken along the plane of line
40-40 in FIG. 39;
[0068] FIG. 41 is a front elevation view of the magnet assembly of
the third embodiment, with the cover removed;
[0069] FIG. 42 is a cross-sectional view of the magnet assembly of
the third embodiment, taken along the plane of line 42-42 in FIG.
41.
[0070] FIG. 43 is an isometric view of an alternate construction of
the magnet assembly of the third embodiment, with a portion broken
away to reveal the position of one of the magnets;
[0071] FIG. 44 is a front elevation view of the alternate
construction of the magnet assembly of the third embodiment;
[0072] FIG. 45 is a vertical cross-sectional view of the magnet
assembly of the third embodiment, taken along the plane of line
45-45 in FIG. 44;
[0073] FIG. 46 is a vertical cross-sectional view of the magnet
assembly of the third embodiment;
[0074] FIG. 47 is an isometric view of a fourth embodiment of a
magnetic navigation system in accordance with the present
invention;
[0075] FIG. 48 is a top plan view of the magnetic navigation system
of the fourth embodiment;
[0076] FIG. 49 is a right side elevation view of the magnetic
navigation system of the fourth embodiment;
[0077] FIG. 50 is a front elevation view of the magnetic navigation
system of the fourth embodiment; and
[0078] FIG. 51 is an isometric view of a combination of a magnetic
resonance imaging device and a bi-planar imaging device;
[0079] FIG. 52 is a top plan view of the combination magnetic
resonance imaging device and bi-planar imaging device;
[0080] FIG. 53 is a side elevation view of the combination magnetic
resonance imaging device and bi-planar imaging device; and
[0081] FIG. 54 is an end elevation view of the combination magnetic
resonance imaging device and bi-planar imaging device.
[0082] Corresponding reference numerals indicate corresponding
parts throughout the several views of the drawings.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The First Embodiment
[0083] A first embodiment of an inventive open field magnetic
surgical system constructed according to the principles of this
invention is indicated generally as 50 in FIG. 1. The system 50
comprises a patient support 52, a magnet assembly 54 on a moveable
magnet support 56, and an imaging assembly 58.
[0084] The patient support 52 preferably comprises an elongate bed
60 mounted on a pedestal 62. The foot of bed 60 is oriented toward
the front of system and the head of the bed is oriented toward the
rear of the system. The head of the bed 60 is narrower than foot of
the bed so that it can fit inside the magnet assembly 54 and
accommodate the imaging devices of the imaging assembly 58. The bed
60 is preferably movable with respect to the pedestal 62, to allow
the patient to be moved relative to the magnet assembly 54. The bed
60 can preferably be moved longitudinally forwardly and rearwardly
and vertically upwardly and downwardly, and it can be rotated about
its longitudinal axis.
[0085] The magnet assembly 54 comprises a housing 64 containing
three magnets 66, 68, and 70. The magnets 66, 68, and 70 are
preferably electromagnet coils and more preferably superconducting
electromagnet coils 72, 74, and 76. Suitable power and cooling
conduits are provided within the housing 64, as is known.
[0086] The magnet coils 72, 74, and 76 are arranged to provide a
magnetic force within an operating region sufficient to move a
magnetic medical device within that portion of a patient inside the
operating region. This magnetic medical device may be, for example
a magnet-tipped catheter, endoscope, or other elongate medical
device or a magnet-tipped guidance for guiding an elongate medical
device.
[0087] As best shown in FIGS. 7-10, coil 72 is arranged in a
transverse plane with its axis 72' extending generally
longitudinally, parallel to the axis of the patient support in this
preferred embodiment, the coil 72 has an 26.090 inch outer
diameter, a 19.010 inch inner diameter, and is 2.620 inches thick,
carrying up to 100 amperes at 11.7 kA/cm ; coils 74 and 76 are
similar in construction and preferably oriented in mutually
perpendicular planes that are perpendicular to the plane of coil
72. Each of the coils 74 and 76 has an outside diameter of 21.826
inches, an inside diameter of 15.750 inches, and is 2.850 inches
thick, carrying up to 100 amperes at 11.7 kA/cm. The faces of the
coils 74 and 76 are spaced 11.9 inches from the axis of the coil
72, and the face of the coil 72 is spaced 12.75 inches from the
axes 74' and 76' of the coils 74 and 76. The edges of coils 74 and
76 are spaced 1.88 inches from the edge of coil 72, and coils 74
and 76 are 1.45 inches apart at their closest points. The sizing
and spacing of the magnet coils is described below.
[0088] The magnet coils 72, 74, and 76 are preferably arranged in
mutually perpendicular planes such that the axes 72', 74', and 76'
of the coils intersect at a point in the center of the operating
region.
[0089] The magnet assembly 54 is preferably mounted on a moveable
magnet support 56 with an arm 78, such that the magnet assembly can
rotate about a longitudinal axis parallel to the longitudinal axis
of the bed 60. The magnet assembly can preferably turn about
20.degree. in either direction. This movement helps prevent shading
of the imaging beam in certain circumstances. Of course, the magnet
assembly could be fixedly mounted, if desired, and further could be
fixedly mounted in a different orientation from that shown in the
figures, for example below the patient support 52 to facilitate
urological and GI uses of the system.
[0090] The magnet support 56 contains power supply and coolant for
the coils 72, 74, and 76. Power and coolant are communicated to the
coils in housing 64 through arm 78. As shown in FIG. 3, the magnet
support 56 is slidably mounted on tracks 80 to move forwardly and
rearwardly (toward and away from the patient support). Stops 82 on
the tracks 80 restrict forward motion of the magnet support 56.
There are a plurality of holes 84 longitudinally spaced along the
tracks 80. The magnet support 56 has locking pins (not shown)
controlled by locking handles 86 to engage the holes 84 and lock
the magnet in accurately located positions. Instead of, or in
addition to, this locking mechanism, some other positioning
mechanism such as a motorized or servo-controlled mechanism can be
provided. This allows the position of the magnet assembly 54 to be
automatically controlled by an external controller or computer.
[0091] The housing 64 preferably has an opening 88 aligned with the
central opening of the coil 72, so that a portion of the patient
support and/or the patient thereon can extend through the housing
so that the desired portion of the patient's body can be positioned
within the operating region of the magnet assembly 54.
[0092] The imaging assembly 58 comprises at least one imaging
device, and in the preferred embodiment two imaging devices 90 and
92, mounted on a C-arm support 100 of C-arm 94. Such supports are
made, for example, by General Electric Co. of Syracuse, N.Y. The
imaging devices 90 and 92 are preferably arranged perpendicular to
each other to provide bi-planar imaging in mutually perpendicular
planes. Each of the imaging devices 90 and 92 comprises an imaging
plate 96 and an imaging beam source 98. In this preferred
embodiment the imaging plates 98 are amorphous silicon imaging
plates, known as LAST plates available from Varian, Palo Alto,
Calif. These plates 96 are not affected by the presence of magnetic
fields, such as those caused by the magnet coils 70, 72, and 74.
The imaging beam sources 98 are preferably X-ray sources. Of course
some other imaging beam and imaging plate could be used if
desired.
[0093] As shown in the Figures, C-arm 94 comprises a C-shaped
support 100 on which the X-ray sources 98 of the imaging devices 90
and 92 are mounted. The C-shaped support 100 has a wedge shaped
block 102 having perpendicular faces 104 and 106 which arms 108,
each mounting one of the imaging plates 96, extend. The arms 108
are hollow, providing a protected path for electrical wiring to the
imaging plates 96. The arms 108 are preferably attached to blocks
110 that can move on their respective faces 104 and 106, to permit
adjustment of the positions of the imaging plates 96.
[0094] The C-shaped support 100 is mounted on body 112, and moves
about its circumference relative thereto so that the C-shaped
support turns about its central axis. The body 112 is rotably
mounted to the vertical leg 114 of a generally L-shaped bracket
116. The body 112 can rotate relative to the L-shaped bracket 116
about a generally horizontal axis. The horizontal leg 118 of the
generally L-shaped bracket 116 is pivotally mounted to the base 120
of the system so that the generally L-shaped bracket pivots about a
generally vertical axis.
[0095] The C-arm 94 thus allows the imaging devices 90 and 92 to be
rotated about three mutually perpendicular axes. These axes
preferably intersect, and their intersection is preferably in the
operating region of the magnet assembly 54, and more preferably
their intersection coincides with the intersection of the axes 72',
74', and 76' of the magnet coils 72, 74, and 76. The imaging
devices 90 and 92 rotate about a first axis when the C-shaped
support 100 turns relative to the body 112 (see FIG. 6). The
C-shaped support 100 can preferably rotate clockwise and counter
clockwise over a range of about 90.degree.. The imaging devices 90
and 92 rotate about a second generally horizontal axis when the
body 112 rotates relative to the L-shaped bracket 116 (see FIG. 4).
The body 112 can preferably rotate about 30.degree. forwardly and
rearwardly with respect to the L-shaped bracket 116. The imaging
devices 90 and 92 rotate about a third generally vertical axis when
the L-shaped bracket 116 rotates relative to the base 120 (see FIG.
5). The L-shaped bracket 116 can preferably rotate about 30.degree.
forwardly and rearwardly with respect to the base 120.
[0096] As best shown in FIG. 2A the imaging apparatus 58 provides
bi-planar imaging of the portion of the patient's body inside the
operating region of the magnet assembly 54. The support arms 108
are configured to clear the patient and the head of the bed, and
support the imaging plates 96 in the space between the operating
region and the magnet coils 72, 74, and 76, of the magnet assembly
54 while maintaining the imaging plates aligned with their
respective imaging beam sources 98. The imaging devices 90 and 92
can be moved around the operating region to accommodate movement of
the magnet assembly 54 and to provide the most advantageous views
of the operating region so that the surgeon can see the navigation
of the magnetic medical device.
[0097] The magnet coils 72, 74, and 76 provide a controllable
magnetic field inside that portion of a patient within the
operating region of the magnet assembly 54. The coils 72, 74, and
76 provide a magnetic field of at least about 0.1 Tesla, and in the
preferred embodiment at least about 0.3 Tesla. The imaging devices
90 and 92 provide bi-planar imaging of the operating region. The
imaging plate 96 and the imaging beam source 98 are positioned on
opposite sides of the operating region, with the imaging plates
disposed between the operating region and the magnet coils 72, 74,
and 76. FIG. 11 is a partial representation of the apparatus shown
in FIGS. 1-5, with portions omitted to show the operational
relationship between the electromagnetic coils 72, 74, 76, the
imaging tubes 98, the imaging plate supports 108, and the imaging
plates 96. Also shown is the passageway 88 through which a
physician has access to an operating region R in which the surgical
procedure is taking place in patient P. As explained above, the
passageway 88 allows portions of the patient to extend through the
magnet assembly in order to bring selected portions of the patient
into the operating region. Although FIG. 11 is not drawn to scale,
a comparison of FIG. 11 shows that arcuate support 100, on which
the imaging devices 90 and 92 are mechanically coupled, may
reorient those mechanically-coupled apparatuses about the various
axes with three degrees of freedom to provide different medically
useful views of operating region R within the patient P.
[0098] Sizing and Locating the Electromagnet Coils
[0099] The method by which the size and location of the coils can
be selected is as follows: It is to be understood that use of the
same method, with different compromises or initial assumptions, may
result in a system having coils of somewhat different sizes and
locations, but still within the principles of this invention.
[0100] Using the Biot-Savart Law, it is possible to calculate the
magnetic field everywhere for a coil having a given shape, size,
and total number of ampere-turns. To arrive at the particular
combination of size and location described above, the inventors
started with the assumption that three coils would provide the best
compromise between being too large and too close to provide a
needed internal exclusion volume for imaging equipment and beams,
while not being too weak to provide the needed strength in a given
operating region or procedure volume inside the patient. The three
coil choice follows from experience with six coil coil systems,
and, in accordance with the invention, provides much more freedom
for physicians and imaging.
[0101] The inventors also intended for the body-axis coil (coil 72
in the first embodiment), to be larger and to have a free air bore
large enough for the patient's head, with clearance for tubes,
etc., so that the patient's chest can be positioned within the
operating region. It is also most convenient and economical for
construction purposes and for calculating operating currents to
have the three coils be orthogonal, and for the two transverse
coils to be alike. Other non-orthogonal arrangements could be
calculated, but would result in less efficient structural
designs.
[0102] These qualitative requirements dictate the approximate size
and shape of the three coils. If the coils are huge, they would
provide great freedom for the imaging devices and for the surgeon,
but the coil would be heavy, expensive and have long ramping times
for field changes. If the coils are too small, they would interfere
with the location and motion of the imaging plates 96. That is, the
coils must be far enough from a central convergence point, the
intersection of the three coil axes approximately centered in the
operating region, that a pair of orthogonal imaging plates can move
about the portion of the patient in the operating region, and not
touch the coils, nor shadow each other's imaging x-ray beams. The
dimensional details of the imaging equipment and beams, of the
trial coil sizes and shapes, of the patient and the bed, etc., are
put into a three-dimensional CAD program for interactive
decision-making magnetic field determinations.
[0103] Added to this, the coils must be large enough, individually,
that their near field lines do not bend severely in the operating
region, which is centered near the intersection of their axes.
Otherwise, it becomes difficult to attain the field strengths
needed at the needed distances from the coils, for certain
directions of the field.
[0104] An exact determination of the coil sizes and locations is
achieved by iterative computer modeling in conjunction with the CAD
plots. On a computer, a first trial size is chosen for the three
coils of the set, and the fields are calculated at various angles
and distances from the coil, assuming a current density (e.g.,
14,000 Amperes per square cm) that is suitable for the
superconducting coils of these strengths. From this choice, field
lines and lines of equal field strength at full current for one
coil (e.g., the axial coil, 72 in the first embodiment) are plotted
to scale on a CAD drawing of the system with assumed coil location
and with patient and imaging equipment in place.
[0105] FIG. 12 is an illustration of such a CAD drawing. The
operating region R within a patient P is shown, as are magnetic
field lines f generated by coil 72. Lines F representing contours
of equal magnetic field strength are also shown. Locations of
imaging plates 96 are also represented. The axial coil (72 in the
first embodiment) is also shown in FIG. 12, although its magnetic
field is not represented. (The orientation of coil 74 as shown in
FIG. 12 is not the same as that shown in FIG. 1 and other figures.)
The axes 72' and 74' and of coils 72 and 74, respectively, are also
represented in FIG. 12.
[0106] Given a target field strength requirement, e.g., 0.3 Tesla,
it can be determined, from the iterative computer modeling or by
some other method, whether the individual coils have sufficient
strength to cover, or nearly cover, the operating region, when
appropriately combined. If the coils are too strong, the ramp time
and weight will be too great, and their cross section can be
reduced.
[0107] Each coil supplies most of the field strength for the
direction along its axis. The general requirement of small field
curvature for the field lines leads to the fact that the coils act
predominantly independently for each axis. That is, orthogonal
coils do not contribute an operatively significant field component
along the direction of the axis of the other coils in the operating
region. And, curved lines fail to achieve sufficient strength along
bisecting planes between coils. The total field at any location in
the operating region, and at any required angle, therefore, will
be, for purposes of magnetically-assisted surgery, the sum of the
individual fields from each of the three coils. While this "vector
sum" model which assumes straight field lines is only approximately
correct, a computer can make accurate, detailed calculations of the
total fields of the system with any given set of currents. A final
determination of meeting field requirements in the operating region
involves only modest changes from the trials just described. The
final determination of coil sizes and locations, subject to the
general considerations stated above, uses a computer program to
calculate the magnetic fields and resultant ramping times as
follows.
[0108] The operating region can be broken into small segments or
"nodes," for example, of about 20 along each side, so that a
cubical-shaped operating region would have about 8,000 nodes. For
about 20 random directions, in each node, the computer calculates
the three coil currents needed to provide the required magnetic
field strength at each direction, should the operating point be in
the center of that node. Consequently, a total of 20.times.8,000
calculations are made to provide this sampling of the total
operating region. (Only two angles are needed to specify any
direction in space, for example, a polar and an azimuthal angle.
Therefore, there are only three unknown currents in each
calculation, and the magnetic field strength and direction
constitute three unknowns, so the calculation is a simple matrix
solution. Information about such matrix calculations is provided in
patent application Ser. No. 08/920,446, filed Aug. 29, 1997, on
"Method and Apparatus for Magnetically Controlling Motion Direction
of a Mechanically Pushed Catheter," incorporated by reference
herein in its entirety.
[0109] In using these calculations, it is often important to the
physician in a particular application to be able to make use of a
statistical statement about the distribution of coil currents, and
consequently, the ramping time. For the purpose of determining the
time needed for ramping, the maximum current of each set, is chosen
in a sequence of turns in navigating to a target, and a model of
the ramping needs is used. In one application, the essential
ramping sequence has the following steps: (1) determine the
previous field direction at the magnetic object location, (2)
determine the desired new direction and the angle of the change,
(3) using knowledge of the field needed to make a turn of this
magnitude, set the new field direction and magnitude, (4) execute
the new ramp, and (5) upon completion of the ramp and turn, ramp
the current down.
[0110] Each of these five-step sequences can be evaluated for the
total ramp-up, ramp-down time. The computer can do the estimates
for each of the above-stated 160,000 cases, and perform plots of
either the overall probability distribution of ramp times, or it
can plot binned probabilities for turns of 0-10.degree.,
10-20.degree., etc. Such plots can inform the surgeon of the time
needed for a given angle of turn. And, with an intuitive display,
such as a thermometer type representation on a screen, the surgeon
can quickly decide whether magnetic assist is necessary or useful
on any given turn, thereby increasing the efficiency and
effectiveness of the overall procedure.
[0111] When the optimum compromise of coil size, location and coil
power is determined, the dimensions and magnetic requirements are
met, the design goes to a succeeding stage. From mechanical
application of the Biot-Savart law, it is possible to calculate the
stresses on each coil due to the interaction of currents in it and
in the other coils. Textbooks (e.g., Foundations of Electromagnetic
Theory, Reitz, Milford, and Crysty, 3.sup.rd Ed., page 166) give
equations that may be used to calculate the vector differential
interaction force d.sup.2F between a differential length of a first
coil, dl.sub.1, carrying current I.sub.1, and a differential length
of a second coil, dl.sub.2, carrying current I.sub.2. These can be
integrated or approximately summed. In the latter case, subtended
angles of ten degrees might, for example, be chosen for each coil
and the appropriate interactions vector summed. It would be useful
in such a case to find the total force dF on each segment
subtending 10 degrees of the first coil from the complete 360
degrees of each of the other two coils (the second coil and a third
coil). This complete procedure is able to handle any given cross
section of these circular coils, when used in a typical finite
element program such as "Maxwell EM" by Ansoft Corporation of
Pittsburgh, Pa.
[0112] Then the three components of dF are entered into a finite
element analysis program "FEA" dealing with stresses and forces,
e.g. "pro/MECHANICA".RTM., Parametric Technology Corp., Waltham
Mass., which can be used by one skilled in the art on any inputted
structure supporting the three coils. An individual coil force is
transmitted from its surround, a "bobbin," to the supporting
structure. In one simple but not preferred embodiment, three plates
are welded together, each supporting one of the coils in the
appropriate location. The results of calculation are often plotted
as colored graphs, where regions of different stresses in the
support structure (responding to the magnetic forces) are shown in
different color. In addition, the program can determine deflections
by summing reaction deflection to the stresses in individual
elements of the structures. Then the designer tries different
support struts which can alleviate excessive stresses or
deflections in the first, simpler trial design. By an iterative
process, and standard experience in mechanical design, the designer
arrives at design shapes and/or structure details that minimize the
overall weight of the structure, while exhibiting no excessive
stresses and deflections.
[0113] In addition to the structural support and strength, the coil
mounting system for superconducting systems must consider the
cryogenic materials and transfer of heat and cryogens. Those
skilled in the art have methods and programs to calculate heat
transfer. They also have methods for most efficiently arranging
insulation, vacuum spaces, intermediate heat shields, and ducting
for liquid cryogen transfer, as well as cold gas exit, if the
system is not recondensing and recirculating.
[0114] Several overall cryogenic systems in common practice are
suitable for the practice of this invention. One such system simply
uses liquid helium to cool the superconducting coils. The liquid
helium evaporates and goes out as a gas. This system usually
employs a 77.degree. Kelvin shield attached to a liquid nitrogen
reservoir. Another method uses a cryogenic cooler that cools an
object down to the approximately 4.5.degree. Kelvin needed to
maintain superconducting wires in the superconducting state. This
cryogenic cooler may either be attached solidly to the coil bobbin
or it may, for flexibility, be coupled with liquid helium, which
may either be totally enclosed or may need occasional replenishing.
A cryogenic cooler may be used to cool a shield to intermediate
temperatures. The cryogenic cooler may be attached solidly to the
shield, or with a gas coupling, such as liquid neon. Cryogenic
coolers have been designed to have two or more stages so as to
supply more heat removing power at the higher, intermediate
temperatures, and a lower cooling rate at the liquid helium
temperatures. The selection of which system to use depends upon
both economical and technical features, because cryocoolers are, at
present, relatively expensive. Liquid helium is also expensive,
however, and both space and weight are important considerations.
Therefore, recirculating systems, which can be smaller and lighter,
may be preferred.
[0115] As is known, the coils may have a split or two piece
construction to better accommodate thermal contraction upon
cooling, and to facilitate coolant.
The Second Embodiment
[0116] A second embodiment of an inventive open field magnetic
surgical system constructed according to the principles of this
invention is indicated generally as 200 in FIGS. 13-24. The system
200 is similar in construction to the system 50, and comprises a
patient support 202, a magnet assembly 204 on a moveable magnet
support 206, and an imaging assembly 208.
[0117] The patient support 202 preferably comprises an elongate bed
210 mounted on a pedestal 212. The foot of the bed 210 is oriented
toward the front of the system and the head of the bed is oriented
toward the rear of the system. The head of the bed 210 is narrower
than the foot of the bed so that it can fit inside the magnet
assembly 204 and accommodate the imaging devices of the imaging
assembly 208. The bed 210, is preferably moveable with respect to
the pedestal 212 to allow the patient to be moved relative to the
magnet assembly. The bed can be moved into and out of the system;
raised and lowered, and rotated about its longitudinal axis. Other
movements can be provided to facilitate positioning the patient
relative to the operating volume of the magnet assembly.
[0118] The magnet assembly 204 comprises a housing 214 containing
three magnets 216, 218, and 220. The magnets 216, 218, and 220 are
preferably electromagnetic coils, and more preferably
superconducting electromagnetic coils 222, 224, and 226. The
housing 214 includes a jacket 228 containing suitable power and
cooling apparatus to operate the superconducting coils.
[0119] The magnet coils 222, 224, and 226 are arranged to provide a
magnetic force within the operating volume sufficient to move a
magnetic medical device within that portion of a patient inside an
operating region.
[0120] As best shown in FIGS. 29-33 the magnet coils 222, 224, and
226 are preferably arranged in three mutually perpendicular planes
such that the axes of the three coils intersect generally in the
center of the operating region. Coil 222 is arranged in a
transverse plane with its axis extending generally longitudinally,
parallel to the longitudinal axis of the patient support 202. The
coil 222 is wound around a bobbin 230 that is secured to a plate
232. In this preferred embodiment, the coil 222 has a 28.2 inch
outer diameter, a 21.06 inch inner diameter, and is 4.47 inches
thick.
[0121] Coils 224 and 226 are similar in construction and are
preferably oriented in mutually perpendicular planes that are
perpendicular to the plane of coil 222. Each of the coils 224 and
226 has an outside diameter of 26.48 inches, an inside diameter of
20.23 inches, and is 5.69 inches thick. The faces of the coils 224
and 226 are spaced 13.81 inches from the axis of the coil 222, and
the face of the coil 222 is spaced 13.78 inches from the axes of
the coils 224 and 226. Coil 224 is wound around a bobbin 234 that
is secured to plate 236. Coil 226 is wound around bobbin 238 that
is secured to plate 240. The plates 232, 236 and 240 are secured
together to form a self-supporting structure capable of
withstanding the forces generated by the magnetic fields of the
coils. The housing 214 preferably has an opening 242 therein
aligned with the central opening in coil 222 so that a portion of
the patient support and/or the patient can extend therethrough, to
bring the desired portion of the patient within the operating
region of the magnet assembly 204.
[0122] The housing 214 is preferably mounted on a stanchion 244,
which in this second embodiment forms the magnet support 206. The
housing 214 preferably can pivot relative to the stanchion 244
about a longitudinal (front to back) horizontal axis. The housing
214 can preferably pivot 20.degree. from the center (See FIG. 24)
toward the left (See FIG. 21A) and the right (See FIG. 23). The
bottom of the stanchion 244 is slidably mounted in tracks 246 in
the base 248 of the system 200. Thus the stanchion 244 (and the
housing 214) can be moved forward (toward the patient support 202)
and rearward (away from the patient support).
[0123] The imaging assembly 208 is identical in construction to
imaging assembly 58 (shown best in FIG. 2A), and corresponding
parts are identified with corresponding reference numerals. The
imaging devices 90 and 92 can be pivoted about a horizontal
transverse axis as the body 112 tilts rearwardly (FIG. 21A) and
forwardly (FIG. 21B) relative to the vertical leg 114 of the
generally L-shaped bracket 116. The body 112 can pivot about
30.degree. rearwardly and forwardly. The imaging devices 90 and 92
can be pivoted about a generally vertical axis as the horizontal
leg 118 of generally L-shaped bracket 116 pivots rearwardly (FIG.
22A) and forwardly (FIG. 22B). The L-shaped bracket 116 can pivot
about 30.degree. rearwardly and forwardly. The imaging devices 90
and 92 can be rotated about a third axis as support 100 rotates
relative to body 112 clockwise (FIG. 23) and counterclockwise (FIG.
19). The c-shaped support 100 can rotate 90.degree. relative to
body 112.
[0124] The imaging devices 90 and 92 provide bi-planar imaging of
the portion of a patient's body inside the operating region of the
magnet assembly 204. The support arms 108 are configured to clear
the patient and the head of the bed, and support the imaging plates
96 in the space between the operating volume and magnet coils 222,
224 and 226 of the magnet assembly 204, while maintaining the
imaging plates 96 aligned with their respective imaging beam
sources 98. The imaging devices 90 and 92 can be moved around the
operating region to accommodate movement of the magnet assembly 204
and to provide the most advantageous views of the operating region
so that the surgeon can see the navigation of the medical
device.
The Third Embodiment
[0125] A third embodiment of an inventive open field magnetic
surgery system constructed according to the principles of this
invention is indicated generally as 300 in FIGS. 34-36. The system
300 is similar in construction to systems 50 and 200, and comprises
a patient support 302, a magnet assembly 304 on a moveable magnet
support 306, and an imaging assembly 308.
[0126] The patient support 302 preferably comprises an elongate bed
310 mounted on a pedestal 312. The foot of the bed 310 is oriented
toward the front of the system and the head of the bed is oriented
toward the rear of the system. The head of the bed 310 is narrower
than the foot of the bed so that it can fit inside the magnet
assembly 304 and accommodate the imaging devices of the imaging
assembly 308. The bed 310, is preferably moveable with respect to
the pedestal 312 to allow the patient to be moved relative to the
magnet assembly. The bed can be moved into and out of the system;
raised and lowered, and rotated about its longitudinal axis. Other
movements can be provided to facilitate positioning the patient
relative to the operating volume of the magnet assembly.
[0127] The magnet assembly 304 comprises a generally hemispherical
housing 314 containing three magnets 316, 318 and 320. The magnets
316, 318 and 320 are preferably magnet coils, and more preferably
superconducting electromagnet coils 322, 324 and 326. The housing
314 contains suitable power and cooling apparatus to operate the
superconducting coils.
[0128] The magnet coils 322, 324 and 326 are sized and arranged to
provide a magnetic force within an operating region sufficient to
move a magnetic medical device within that portion of a patient
inside the operating region.
[0129] As best shown in FIGS. 41 and 42 the coils 322, 324 and 326
are preferably arranged in three mutually perpendicular planes such
that the axes of the three coils intersect generally in the center
of the operating region. Coil 322 is arranged so that it is
normally in a vertical transverse plane, with its axis extending
generally longitudinally, parallel to the longitudinal axis of the
patient support 302. In this third preferred embodiment, the coil
322 has 26.09 inch outer diameter, a 19.01 inch inner diameter, and
a thickness of 2.62 inches.
[0130] Coil 324 and 326 are similar in construction and are
preferably oriented in mutually perpendicular planes that are
perpendicular to the plane of coil 322. Each of the coils 324 and
326 has an outside diameter of 21.83 inches, an inside diameter of
15.75 inches, and a thickness of 2.85 inches. The faces of the
coils 324 and 326 are spaced 11.90 inches from the axis of coil
322, and the face of coil 322 is spaced 12.75 inches from the axes
of the coils 324 and 326.
[0131] The housing 314 preferably has an opening 328 therein
aligned with the central opening of coil 322 so that a portion of
the patient support and/or the patient can extend therethrough, to
bring the desired portion of the patient within the operating
volume.
[0132] An alternate construction of the magnet assembly of this
third embodiment is indicated generally as 304' in FIGS. 43-46. The
magnet assembly 304' comprises a generally hemispherical housing
314'. The housing has a cold head mounting assembly 315 for
connecting the magnet assembly 304 to a cooling system. Inside the
housing 314' the three magnets 322', 324', and 326'. The coils
322', 324' and 326' are preferably arranged in three mutually
perpendicular planes such that the axes of the three coils
intersect generally in the center of the operating region. Coil
322' is arranged so that it is normally in a vertical transverse
plane, with its axis extending generally longitudinally, parallel
to the longitudinal axis of the patient support 302. In this third
preferred embodiment, the coil 322' has 24.22 inch outer diameter,
a 17.4 inch inner diameter, and a thickness of 2.62 inches.
[0133] Coils 324' and 326' are similar in construction and are
preferably oriented in mutually perpendicular planes that are
perpendicular to the plane of coil 322'. Each of the coils 324' and
326' has an outside diameter of 22.56 inches, an inside diameter of
16.14 inches, and a thickness of 3.05 inches. The faces of the
coils 324' and 326 are spaced 11.94 inches from the axis of coil
322', and the face of coil 322' is spaced 12.81 inches from the
axes of the coils 324' and 326'.
[0134] The housing 314' preferably has an opening 328' therein
aligned with the central opening of coil 322' so that a portion of
the patient support and/or the patient can extend therethrough, to
bring the desired portion of the patient within the operating
volume.
[0135] The housing 314 has trunions 330 and 332 projecting from its
exterior. These trunions 330 and 332 are connected to a band 334,
that is mounted on an inverted "J" shaped support 336. The band 334
and the support 336 suspend the housing 314 so that the axis of the
generally hemispherical housing 314 extends at an angle with
respect to vertical and horizontal, so that the housing faces
generally downwardly. The axis preferably forms an angle of about
45.degree. with respect to horizontal. The support 336 is mounted
to a platform 338 which is slidably mounted in tracks 340 in base
342. Thus the support 336 (and the housing 314) can be moved
forward (toward the patient support as shown in FIG. 35) and
rearward (away from the patient support as shown in FIG. 36). The
support 336 has a circular bottom 344 which can slide relative to
the platform 338 so that the housing 314 pivots, preferably about a
vertical axis that extends through the point of an intersection of
the axes of the three magnet coils 322, 324 and 326. In this third
preferred embodiment, the housing 314 can pivot 30.degree. toward
each side.
[0136] The imaging assembly 308 is identical to the imaging
assembly 208 of the second embodiment and the imaging assembly 58
of the first embodiment, and corresponding parts are identified
with corresponding reference numerals.
[0137] The imaging devices 90 and 92 can be pivoted about a
horizontal transverse axis as the body 112 tilts rearwardly and
forwardly relative to the vertical leg 114 of the generally
L-shaped bracket 116. The body 112 can pivot about 30.degree.
rearwardly and forwardly. The imaging devices 90 and 92 can be
pivoted about a generally vertical axis as the horizontal leg 118
of generally L-shaped bracket 116 pivots rearwardly and forwardly.
The L-shaped bracket 116 can pivot about 30.degree. rearwardly and
forwardly. The imaging devices 90 and 92 can be rotated about a
third axis as support 100 rotates relative to body 112 clockwise
and counterclockwise. The C-shaped support 100 can rotate
90.degree. relative to body 112.
The Fourth Embodiment
[0138] A fourth embodiment of an inventive open field magnetic
surgery system constructed according to the principles of this
invention is indicated generally as 400 in FIGS. 47-50. The system
400 comprises a patient support 402, a magnet assembly 404, and a
CT imaging assembly 406.
[0139] The patient support 402 preferably comprises an elongate bed
410 mounted on a pedestal 412. The foot of the bed 410 is oriented
toward the front of the system and the head of the bed is oriented
toward the rear of the system. The head of the bed 410 is narrower
than the foot of the bed so that it can fit inside the magnet
assembly 404 and accommodate the imaging devices of the imaging
assembly 406. The bed 410, is preferably moveable with respect to
the pedestal 412 to allow the patient to be moved relative to the
magnet assembly. The bed can be moved into and out of the system;
raised and lowered, and rotated about its longitudinal axis. Other
movements can be provided to facilitate positioning the patient
relative to the operating volume of the magnet assembly.
[0140] The magnet assembly 404 comprises a plurality (in this
fourth preferred embodiment four) magnet coils 414 ,arranged on
planar support 416, on a base 418. The magnet coils 414 are capable
of generating a magnetic field in an operating region of sufficient
strength to navigate a magnetic medical in the portion of the
patient within the operating region. The coils may all have
parallel axes, but this is not essential and some or all of the
coils may be oriented out of the plane of planar support 416.
[0141] The imaging assembly 406 comprises a compact CT imaging
device 420 adapted to provide real time or near real time CT images
of the operating region. The CT imaging device 420 has an opening
422 through which a portion of the patient support 402 and/or the
patient can extend to allow the surgeon to bring virtually any
portion of the patient's body within the operating region of magnet
assembly 404. The CT imaging device is one that is not
significantly affected by the proximity of the magnets 414.
[0142] It should be noted that the same or a very similar magnetic
and imaging equipment and arrangement may be used to provide for
parenchymal navigation for neurosurgical procedures in brain
tissue, such as for implanting catheters or introducing tubes in
curved paths. See Werp et al., "Method of and apparatus for
intraparenchymal positioning of medical devices," application Ser.
No. 08/969,165, filed Nov. 12, 1997; "Apparatus for and Method of
Controlling an Electromagnetic Coil System," application Ser. No.
08/682,867, filed Jul. 8, 1996; Ritter et al., "Control Method for
Magnetic Stereotaxis System," U.S. Pat. No. 5,654,864, issued Aug.
5, 1997; Howard et al., "Magnetic Stereotactic System for Treatment
Delivery," U.S. Pat. No. 5,125,888, issued Jun. 30, 1992; Howard et
al., "Magnetic Stereotactic System for Treatment Delivery," U.S.
Pat. No. 5,707,335, issued Jan. 13, 1998; Howard et al., "Video
Tumor Fighting System," U.S. Pat. No. 4,869,247, issued Sep. 26,
1989; Howard et al., "Magnetic Stereotactic System for Treatment
Delivery," U.S. Pat. No. 5,779,694, issued Jul. 14, 1998; Howard et
al., "Magnetic Stereotactic System for Treatment Delivery,"
application Ser. No. 09/114,414, filed Jul. 13, 1998; "Method and
Apparatus for Magnetically Controlling Motion Direction of a
Mechanically Pushed Catheter," application Ser. No. 08, 920,446,
filed Aug. 29, 1997; and Ritter et al., "Method and Apparatus for
Rapidly Changing a Magnetic Field Produced by Electromagnets,"
application Ser. No. 08/921,298, filed Aug. 29, 1997. Further
applications of the inventive apparatus include the introduction of
biopsy tools, electrodes for palidotomy, or stimulators for other
treatment of Parkinson's disease, and the introduction of drug
infusion apparatus.
[0143] A combination of a magnetic resonance imaging device and a
bi-planar imaging device is shown in FIGS. 51-54. The combination
includes a conventional magnetic resonance imaging device 500 and a
bi-planar imaging assembly 502, which is preferably identical to
imaging assembly 58, shown best in FIG. 2A. This allows the patient
to be imaged with the MRI and then imaged with the bi-planar
imaging assembly close in time, without having to transport the
patient from place to place to obtain the images. This facilitates
calibration of the MRI and the bi-planar x-ray images used during
magnetic surgery. The combination includes a patient support 504,
which is similar in construction to patient support 52, described
above. This allows the patient to be moved into and out of the MRI
500 and into and out of the bi-planar imaging assembly 502. The
close proximity of the MRI 500 and the bi-planar imaging assembly
502 is permitted in part by the use of amorphous silicon imaging
plates, or some other imaging receptor, that is minimally affected
by the significant magnetic fields adjacent the MRI 500.
[0144] It will be recognized by one skilled in the art that the
various embodiments shown and described herein are intended to be
exemplary, that many modifications may be made within the spirit
and scope of the invention. It should also be clear that
embodiments are possible that incorporate some, but not all, of the
features of the invention, such as, by way of example only,
providing fewer directions of motion for a C-arm. Such embodiments
may still fall within the scope and spirit of the invention, even
though achieving only some of the objectives and advantages
thereof. The scope of the invention should therefore be determined
from the claims, including all legal equivalents thereto, with
reference to the specification and the examples and figures
provided therein.
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