Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-10-27
2004-03-02
Manuel, George (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C606S130000
Reexamination Certificate
active
06701179
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
Not Applicable
REFERENCE TO MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE INVENTION
This invention relates to methods of and devices for generating magnetic fields, and more particularly to the physical characteristics of magnetic field generating coils.
There are various known methods for determining the position of a medical instrument during surgery. For instance, U.S. Pat. No. 5,592,939 to Martinelli, hereby incorporated by reference, discloses a method and apparatus for detecting the position of a medical instrument during surgery. This invention, however, is not limited to any specific method of determining the position of a medical instrument during surgery. For example,
FIG. 1
is a diagram of an examination deck
200
with a medical instrument in a surgical environment. During surgery, for example, examination deck
200
lies below a patient. The medical device, such as a catheter
203
, is placed inside the patient. Catheter
203
has a coil
14
at its distal end. Methods and systems consistent with the '939 patent determine the location and orientation of catheter
203
inside the patient relative to examination deck
200
.
Catheter
203
includes a conductor
16
that leads along catheter
203
to a location outside the patient. Examination deck
200
comprises magnetic field generating coils that produce magnetic fields within a navigational domain
12
. The magnetic fields induce voltage signals in sensing coil
14
. Measurements taken at conductor
16
of the induced voltage signals provide sufficient information to compute the orientation and position of sensing coil
14
.
FIGS. 2A
,
2
B,
2
C, and
3
show magnetic field generating coils.
FIG. 2A
is a diagram of a coil set
202
for generating a substantially uniform magnetic field in the X direction. Driver
28
supplies current in the direction indicated by the arrows. Coil elements
20
and
22
are horizontal, while coil elements
24
and
26
are vertical. Elements
24
and
26
are “compensation” coils, i.e. “Cunard” coils, which cancel some undesirable field components generated by elements
20
and
22
in the Y and Z directions. As a result, coil set
202
generates a substantially uniform X direction field as indicated by field line
27
.
FIG. 2B
is a diagram of a coil set
204
for generating a substantially uniform magnetic field in the Y direction. Coil set
204
includes element
30
spaced from element
32
, but parallel to element
32
. Driver
34
supplies current in the direction indicated by the arrows. Coil set
204
generates a substantially uniform Y direction field as indicated by field line
33
.
FIG. 2C
is a diagram of a coil set
206
for generating a substantially uniform magnetic field in the Z direction. Driver
44
supplies current in the direction indicated by the arrows. Coil elements
36
and
38
are horizontal, while elements
40
and
42
are vertical. Elements
40
and
42
are compensation coils, i.e. Cunard coils, that cancel some undesirable field components in the X and Y directions. As a result, coil set
206
generates a substantially uniform Z direction magnetic field as indicated by field line
43
.
FIG. 3
is a diagram of three pairs of delta coil sets
300
for generating three gradient magnetic fields. The configuration includes a first delta coil pair
50
-
52
, a second delta coil pair
54
-
56
, and a third delta coil pair
58
-
60
. Delta coil pairs
50
-
52
,
54
-
56
, and
58
-
60
are arranged in a circular orientation about the Y axis such that there is an axis perpendicular to the direction of elongation of the coils at ,
120
, and
240
relative to the Z axis. The magnetic field generated by long delta coil
50
and short delta coil
52
is shown by the field lines extending from coils
50
-
52
. The field lines from delta coils
50
-
52
group form a family of substantially constant signal surfaces, i.e. the magnetic fields have a spatial gradient in two of the axis dimensions and a substantially zero field value in the remaining axial dimension.
Discussion of
FIGS. 1
,
2
A,
2
B,
2
C, and
3
are for illustrative purposes only. See U.S. Pat. No. 5,592,939 for further examples.
FIG. 3B
is a diagram of a patient undergoing cranial surgery with a device consistent with this invention. In
FIG. 3B
, the medical device is a probe
302
that is placed inside a head
308
of a patient.
Coil sets
202
-
204
,
300
in
FIGS. 2A-2C
, and
3
are contained within the examination deck
200
of FIG.
1
. Placing all these coils in examination deck
200
, however, causes examination deck
200
to be relatively thick. It is desirable, however, that examination deck
200
be relatively thin for a number of reasons. First, a thinner examination deck
200
is lighter, less cumbersome, and requires less space in a crowded surgery room. Second, if coil sets
202
-
204
,
300
are arranged so that each is a different distance from navigational domain
12
, then the magnetic field strength in navigational domain
12
from each coil set is different. Different magnetic field strengths reduce accuracy of the positioning system. Further, it can be less expensive and easier to manufacturer a thin examination deck as compared to a thick examination deck.
Examination deck
200
, in turn, is placed on an examination table
306
.
FIG. 3A
is a diagram of examination deck
200
placed on the examination fable
306
, consistent with this invention, in a medical setting. Examination table
306
introduces other design constraints,including the width and length of the examination deck
200
, which introduces design constrains on the size and shape of coils inside examination deck
200
. Preferably, the magnetic field generating coils are such that examination deck easily fits onto standard size examination tables, such as examination table
306
.
Therefore, it is desirable to provide an apparatus that allows coil sets to be arranged substantially coplanar with respect to navigational domain
12
. It is also desirable to provide an apparatus that allows examination deck
200
to fit on a standard examination table.
It is an object of the present invention to substantially overcome the above-identified disadvantages and drawbacks of the prior art.
SUMMARY OF THE INVENTION
The foregoing and other objects are achieved by the invention which in one aspect comprises an apparatus for determining a location of a sensor in a surgical navigation domain. The apparatus includes a first magnetic field generator having a first coil set, a second magnetic field generator having a second coil set. The first and second coil sets are disposed substantially within a common plane. The apparatus further includes a processor configured to receive a plurality of signals. The processor calculates the location of the sensor from the plurality of signals. The sensor produces the plurality of signals in response to magnetic fields generated by the first and second magnetic field generators.
In another embodiment of the invention, the first coil set includes at least one delta coil pair for generating a gradient magnetic field-in the navigation domain.
In another embodiment of the invention, each delta coil pair further includes one or more end correction coils. Each delta coil pair is electrically coupled to the corresponding end correction coil, and current flows through the end correction coil in a direction opposite of the direction of the current flowing through the corresponding delta coil pair.
In another embodiment of the invention, the second coil set includes at least one uniform coil pair for generating a uniform magnetic field in the navigational domain.
In another embodiment of the invention, the first coil set includes a first delta coil pair longitudinally oriented along a first axis, a second delta coil pair longitudinally oriented along a second axis, and a third delta coil pair longitudinally oriented along a third axis. The three delta coil pairs are arranged such that the second axis is rotated within the common pla
Hunter Mark W.
Jascob Brad
Martinelli Michael A.
Harness & Dickey & Pierce P.L.C.
Manuel George
Qaderi Runa Shah
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