U.S. patent application number 13/442634 was filed with the patent office on 2013-10-10 for automatic instrument detection for surgical navigation.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY, A NEW YORK CORPORATION. The applicant listed for this patent is Tobias Schroeder. Invention is credited to Tobias Schroeder.
Application Number | 20130267833 13/442634 |
Document ID | / |
Family ID | 49292854 |
Filed Date | 2013-10-10 |
United States Patent
Application |
20130267833 |
Kind Code |
A1 |
Schroeder; Tobias |
October 10, 2013 |
AUTOMATIC INSTRUMENT DETECTION FOR SURGICAL NAVIGATION
Abstract
An identification system for surgical navigation is described.
The navigation system contains an instrument assembly containing a
coil (of a receiver) having an interior space, an instrument
configured to be removably coupled to the coil, and a prong affixed
to the instrument and configured to be at least partially disposed
within the interior space of the coil when the instrument is
coupled to the coil. The prong can have a length corresponding to
the physical dimensions of the instrument. The navigation system
can also contain a transmitter located within the body of a
patient. The navigation system can be used to identify
interchangeable instruments. Other embodiments are described.
Inventors: |
Schroeder; Tobias; (Boston,
MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Schroeder; Tobias |
Boston |
MA |
US |
|
|
Assignee: |
GENERAL ELECTRIC COMPANY, A NEW
YORK CORPORATION
Schenectady
NY
|
Family ID: |
49292854 |
Appl. No.: |
13/442634 |
Filed: |
April 9, 2012 |
Current U.S.
Class: |
600/424 |
Current CPC
Class: |
G01B 7/02 20130101; A61B
2034/2046 20160201; A61B 2017/00482 20130101; A61B 2034/2051
20160201; A61B 2034/2053 20160201; A61B 2034/2065 20160201; G01B
21/047 20130101; A61B 2034/254 20160201; G01B 21/02 20130101; A61B
5/062 20130101; A61B 34/20 20160201; G01B 7/00 20130101 |
Class at
Publication: |
600/424 |
International
Class: |
A61B 5/06 20060101
A61B005/06 |
Claims
1. An instrument assembly, comprising: a coil having an interior
space; an instrument configured to be removably coupled to the
coil; and a prong affixed to the instrument and configured to be at
least partially disposed within the interior the coil when the
instrument is coupled to the coil, wherein the prong has a length
corresponding to the physical dimensions of the instrument.
2. The assembly of claim 1, wherein the coil has an inductance that
is affected when the instrument is coupled to the coil.
3. The assembly of claim 1, further comprising a receiver
containing the coil.
4. The assembly of claim 1, further comprising a processor operably
connected to the coil and configured to determine if the instrument
is coupled to the coil.
5. The assembly of claim 1, wherein the instrument is a first
instrument, the prong is a first prong, and further comprising: a
second instrument configured to be removably coupled to the coil,
the second instrument having physical dimensions differing from the
physical dimensions of the first instrument; and a second prong
having a length corresponding to the physical dimensions of the
second instrument.
6. The assembly of claim 5, further comprising a processor
configured to determine if the first instrument, the second
instrument, or no instrument is coupled to the coil.
7. The assembly of claim 6, wherein the processor is configured to
identify the physical dimensions of the first instrument based on
the length of the first prong and the physical dimensions of the
second instrument based on the length of the second prong.
8. The assembly of claim 1, wherein the instrument assembly is
configured to be connected to the transmitter of a surgical
navigation system.
9. A surgical navigation system, comprising: a transmitter; and an
instrument assembly communicating with the transmitter, comprising:
a coil having an interior space; an instrument configured to be
removably coupled to the coil; and a prong affixed to the
instrument and configured to be at least partially disposed within
the interior the coil when the instrument is coupled to the coil,
wherein the prong has a length corresponding to the physical
dimensions of the instrument.
10. The system of claim 9, wherein the instrument is a medical
instrument configured to be placed within the body of a
patient.
11. The system of claim 10, wherein the transmitter is connected to
the body of the patient and the transmitter cooperatively operates
with the coil to provide data relating to the location and
orientation of the coil with respect to the transmitter and the
body of the patient.
12. The system of claim 11, further comprising: a processor
operatively coupled to the transmitter and to the coil; and a
display operatively coupled to the processor; wherein the processor
is configured to generate an image of the location of the
instrument with respect to the body of the patient using the data
relating to the location and orientation of the coil.
13. The system of claim 9, wherein the coil has an inductance that
is affected when the instrument is coupled to the coil.
14. The system of claim 9, further comprising a receiver containing
the coil.
15. The system of claim 9, further comprising a processor operably
connected to the coil and configured to determine if the instrument
is coupled to the coil.
16. A method for identifying interchangable instruments, the method
comprising: providing one or more instruments, each of the one or
more instruments having a prong of a length corresponding to the
physical dimensions of the one or more instruments; providing a
receiver configured to be coupled to the one or more instruments,
the receiver having a coil with a depth; and identifying if the one
or more instruments is coupled to the receiver based on the length
of the prong when the one or more instruments is coupled to the
receiver.
17. The method of claim 16, wherein the prong of the one or more
instruments is configured to at least partially fill the depth of
the coil when the one or more instruments is coupled to the
receiver.
18. The method of claim 17, further comprising identifying the
coupling based on the inductance of the coil.
19. The method of claim 18, further comprising: providing a
transmitter operatively coupled to a processor; and providing a
display device operatively coupled to the processor.
20. The method of claim 19, further comprising displaying a
representation of the physical dimensions of the one or more
instruments coupled to the receiver as it is oriented with respect
to the transmitter.
21. The method of claim 16, wherein the one or more instruments is
configured to be used inside of the body of a patient.
22. The method of claim 16, further comprising: uncoupling the one
or more instruments from the receiver; coupling another instrument
to the receiver; and identifying the other instrument based on the
length of the prong in that other instrument.
Description
FIELD
[0001] This disclosure relates generally to identifying
interchangeable instruments, and more particularly to automatically
identifying interchangeable instruments for electromagnetic
tracking systems.
BACKGROUND
[0002] Electromagnetic tracking systems have been used in various
industries and applications to provide position and orientation
information relating to objects. For example, electromagnetic
tracking systems may be useful in aviation applications, motion
sensing applications, retail applications, and medical
applications. In medical applications, electromagnetic tracking
systems have been used to provide an operator (e.g., a physician,
surgeon, or other medical practitioner) with information to assist
in the precise and rapid positioning of an instrument (such as a
medical device, implant, tool, or other implement) located in or
near a patient's body during image-guided surgery. The
electromagnetic tracking system provides positioning and
orientation information for an instrument with respect to the
patient's anatomy or to a reference coordinate system. The
electromagnetic tracking system provides intraoperative tracking of
the precise location of the instrument in relation to
multidimensional images of a patient's anatomy. As the instrument
is positioned with respect to the patient's anatomy, the displayed
image is continuously updated to reflect the real-time position and
orientation of the instrument being used.
[0003] The known physical size and shape of the instrument can be
used to calculate the location and orientation of each portion of
the instrument, which is then used, in turn in generating and
displaying the real time position of each portion of the
instrument. The combination of the image and the representation of
the tracked instrument provide position and orientation information
that allows a medical practitioner to manipulate the instrument to
a desired location with an accurate position and orientation and
display that location along with other reference structures or
anatomy.
[0004] When different instruments are used with electromagnetic
tracking systems, the system must be calibrated to the known
physical size and shape of the particular instrument being used so
it will be properly represented on the display. Hall-effect sensors
in a receiver and permanent magnets organized in a particular
pattern in the instruments have been used to identify the different
instruments.
SUMMARY
[0005] This application relates generally to an automatic
identification system for surgical navigation. The navigation
system contains an instrument assembly containing a coil (of a
receiver) having an interior space, an instrument configured to be
removably coupled to the coil, and a prong affixed to the
instrument and configured to be at least partially disposed within
the interior space of the coil when the instrument is coupled to
the coil, where the prong has a length corresponding to physical
dimensions of the instrument. The navigation system can also
contain a transmitter located within the body of a patient. The
navigation system can identify interchangeable instruments by
providing one or more instruments each having a prong of a length
corresponding to the physical dimensions of the instrument,
providing a receiver configured to be coupled to the one or more
instruments, the receiver having a coil with a depth; and
identifying if the one or more instruments is coupled to the
receiver based on the length of the prong when the one or more
instruments is coupled to the receiver.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] The following description can be better understood in light
of the Figures, in which:
[0007] FIG. 1 shows a schematic of some embodiments of an exemplary
electromagnetic surgical navigation system;
[0008] FIG. 2 shows a side perspective view of some embodiments of
an exemplary sensor and instrument;
[0009] FIGS. 3-5 show cross-sectional views of some embodiments of
exemplary sensors and instruments; and
[0010] FIG. 6 shows a schematic representation of circuitry in some
embodiments for identifying different instruments coupled to a
sensor.
[0011] The Figures illustrate specific aspects of the described
systems and methods for automatic instrument detection for surgical
navigation. Together with the following description, the Figures
demonstrate and explain the principles of the structures, methods,
and principles described herein. In the drawings, the thickness and
size of components may be exaggerated or otherwise modified for
clarity. The same reference numerals in different drawings
represent the same element, and thus their descriptions will not be
repeated. Furthermore, well-known structures, materials, or
operations are not shown or described in detail to avoid obscuring
aspects of the described devices.
DETAILED DESCRIPTION
[0012] The following description supplies specific details in order
to provide a thorough understanding. Nevertheless, the skilled
artisan will understand that the described systems and methods for
identifying interchangeable instruments can be implemented and used
without employing these specific details. Indeed, the described
systems and methods for identifying interchangeable instruments can
be placed into practice by modifying the described systems and
methods and can be used in conjunction with any other apparatus and
techniques conventionally used in the industry. For example, while
the description below focuses automatically identifying different
instruments used with surgical navigation systems, the methods and
systems for automatically identifying instruments may be used in
other systems requiring interchangeable instruments.
[0013] In addition, as the terms on, disposed on, attached to,
connected to, or coupled to, etc. are used herein, one object
(e.g., a material, element, structure, member, etc.) can be on,
disposed on, attached to, connected to, or coupled to another
object--regardless of whether the one object is directly on,
attached, connected, or coupled to the other object or whether
there are one or more intervening objects between the one object
and the other object. Also, directions (e.g., on top of, below,
above, top, bottom, side, up, down, under, over, upper, lower,
lateral, orbital, horizontal, etc.), if provided, are relative and
provided solely by way of example and for ease of illustration and
discussion and not by way of limitation. Where reference is made to
a list of elements (e.g., elements a, b, c), such reference is
intended to include any one of the listed elements by itself, any
combination of less than all of the listed elements, and/or a
combination of all of the listed elements. Furthermore, as used
herein, the terms a, an, and one may each be interchangeable with
the terms at least one and one or more.
[0014] FIG. 1 shows some embodiments of an electromagnetic surgical
navigation system 10. The electromagnetic surgical navigation
system 10 may comprise a transmitter 20 attached to a particular
anatomy of interest (i.e., a part of a patient 5), a processor 30,
a display 40, and a sensor and instrument assembly 100 containing
an instrument 110. Signals from a transmitter 20 and a receiver 120
may be sent to the processor 30. The transmitter 20 may include an
array of one or more transmitter coils (not shown in FIG. 1). The
receiver 120 may also include an array of one or more receiver
coils (not shown in FIG. 1). The processor 30 may include
electronics to generate a current drive signal for the one or more
transmitter coils and to measure the mutual inductances between
transmitter and receiver coils, and a computer to calculate the
position and orientation of the receiver 120 with the respect to
the transmitter 20 (or vice versa).
[0015] For example, in some embodiments each of the receiver 120
and the transmitter 20 may include coil assemblies with a trio of
orthogonal and collocated coils that are arranged in particular
positions and orientations to determine movements and positions of
the coils assemblies relative to each other. Similarly, coil sizes
and number of windings may differ between receiver and transmitter
coil assemblies, as well as among the various coils in a coil
architecture trio, as desired. In some embodiments, the processor
30 may include memory with physical dimensions of various
instruments, such as for the different instruments shown in FIGS.
3-5. The processor 30 may further include sensors or input
capabilities to store the physical dimensions of new instruments or
connectivity to other computers, networks, or databases where
information to provide the physical dimensions of various
instruments may be available, depending on the instrument 110 being
used.
[0016] In order to determine the location of the receiver 120, an
alternating current drive signal may be provided to each coil of
the transmitter 20. This generates an electromagnetic field that is
emitted from each coil of the transmitter 20. The electromagnetic
field generated by each coil in the transmitter 20 may induce a
voltage in each coil of the receiver 120. These voltages may be
indicative of the mutual inductances between the coils of the
transmitter 20 and the coils of the receiver 120. These voltages
and mutual inductances may be sent to the processor 30 for
processing. The processor 30 may use these measured voltages and
mutual inductances to calculate the position and orientation of the
coils of the transmitter 20 relative to the coils of the receiver
120, or the coils of the receiver 120 relative to the coils of the
transmitter 20, including six degrees of freedom (x, y, and z
measurements, as well as roll, pitch and yaw angles).
[0017] The calculated position and orientation of the receiver 120
with respect to the transmitter 20, along with known physical
dimensions of the instrument 110 based on the prong 112 (as
described below), and the physical location and dimensions of the
anatomy of the patient 5, may be used to calculate the position of
any portion of the instrument 110 with respect to the anatomy of
the patient 5. The calculated positions and orientations may then
be displayed on display 40 for use by a physician in properly using
instrument 110 on patient 5.
[0018] FIGS. 2-5 illustrate some embodiments of instrument
assemblies 100 containing an instrument 110 and a receiver 120. As
shown in FIG. 2, the receiver assembly 100 may include an
instrument 110 attached to the sensor 120. The sensor 120 may be
electronically coupled to processor 30 through cord 150. The
instrument 110 may include an opening 118 configured to accommodate
the sensor 120 and provide some structure to assist in holding the
sensor 120 in place with the instrument 110.
[0019] The instrument 110 may be formed of any suitable material
for use as a tool, medical instrument, etc. For example, when used
as a medical instrument, the instrument 110 may comprise any
material suitable for use as a medical instrument, including
plastics, metals, or combinations thereof.
[0020] In the embodiments shown in FIGS. 2-5, the instrument
assembly 100 may also include a tool 160. In FIGS. 3-5 different
tools 160a-160c are shown for the purpose of representing examples
of interchangeable instruments 110 and do not necessarily represent
any particular tool or instrument that may be used with the
electromagnetic surgical navigation system 10. As such, tool 160
may be any portion of an instrument 110 that may be used with the
receiver assembly 100. The specific tools 160a, 160b, and 160c are
described in detail below.
[0021] The instrument 110 may also include a prong 112. The prong
112 may be formed of any material sufficient to affect the
impendence of the coil 126 as described in detail below. For
example, in some embodiments the prong 112 may be formed from a
ferromagnetic material, medical-grade stainless steel, or other
suitable material such as ferrite.
[0022] The prong 112 may have a length selected based on the type
of instrument 110 or tool 160. In some embodiments, the prong may
have a length ranging from about 2 mm to about 10 mm. For example,
as shown in FIG. 3, the instrument contains a prong 112a having an
exposed prong length of d.sub.a. The prong length (i.e., d.sub.a in
FIG. 3) may cooperate with the coil 126 to provide identification
to processor 30 that the instrument 110 contains a tool (i.e., 160a
in FIG. 3) having a particular physical size and shape. The size
and shape of various instruments may be stored into memory and
accessible by processor 30 for use in deriving position information
of the instrument 110. Thus, the particular physical size and shape
of the tool (i.e., 160a) may be determined by the size of the prong
(i.e., 112a). Similarly, the prong length d.sub.b of the prong 112b
may correspond to the tool 160b in FIG. 4 and the prong length
d.sub.e of the prong 112c may correspond to the tool 160c in FIG.
5.
[0023] The prong 112 may be contained in the body of the instrument
110 such that it is securely attached to the instrument 110. In
some embodiments, the prong 112 may be co-molded with the
instrument 110 as the instrument 110 is formed. In such
embodiments, the prong 112 may contain a protrusion that helps to
secure the prong 112 into the instrument 110 without allowing the
prong 112 to fall out of or otherwise move with respect to the
instrument 110. In other embodiments, the prong 112 may be bonded
to the instrument 110 with adhesive, press-fit, or other technique
to couple the prong 112 to the instrument 110. In yet other
embodiments, the prong 112 may be attached or connected to the
instrument by screwing it into a threaded hole.
[0024] The instrument assembly 100 may also include receiver 120.
The receiver 120 may include a sensor 122, a prong hole 124, and a
coil 126, as shown in FIGS. 3-5. In some configurations, the
receiver 120 may be formed using a thermoplastic resin
encapsulating the various interior components of the receiver 120
while leaving the pronghole 124 open for positioning of the prong
112. In other configurations, the receiver 120 may formed of
multiple components such that the interior is accessible for
assembly of the receiver 120, and, in some instances, for repair,
recalibration, or replacement of various components of the receiver
120.
[0025] The receiver 120 contains a sensor 122 which may contain one
or more coils (as described herein) and may work in conjunction
with the transmitter 20 and the processor 30 (as described herein)
to help establish a position of instrument 110 relative to the
patient 5. The sensor 122 and the coil 126 may be electrically
connected to the processor 30 through the conductors 128, which may
be housed in the cord 150 and in the receiver 120.
[0026] The receiver 120 also contains a coil 126. The coil 126 may
be placed around the pronghole 124 (i.e., by winding) in the
embodiments illustrated in FIG. 3-5. The prong 112 may then be
inserted into the pronghole 124 so that the coil 126 surrounds the
prong 112. The receiver 120 and the instrument 110 can be connected
to each other by any suitable connection elements or techniques to
form the instrument assembly 100. For example, the receiver 120 and
the instrument 110 may be coupled using detents, latches, access
door, strap, pin, etc.
[0027] In some embodiments, the coil 126 may be multiple coils.
Impedance of each of the multiple coils may be measured separately
or collectively to achieve increased sensitivity to different
lengths of the prong 112. Each of the multiple coils may have
similar or different configurations, yielding varying impedance
response profiles, which can be used to further differentiate
different prongs. Multiple coils may provide for a response that
resembles a digital response to a particular prong length. In some
embodiments, the configuration of the coil 126 used in the receiver
120 may be selected for sensitivity. For example, the impedance of
coil 126 when the prong 112 is present in the pronghole 124 may be
determined in order to indicate to the processor 30 the specific
type of instrument 110 attached to receiver 120. As described
herein, different lengths of the prong 112 may affect the measured
impedance of the coil 126.
[0028] In the illustrated embodiments, a coil having a particular
number of windings of a particular thickness and physical
properties may be selected such that when different lengths of
prongs are inserted into the coil, the coil inductance changes
depending on the length of the prong. As such, different length
prongs provide different inductances, which correspond to coil
impedance. The inductance can be measured, which can indicate the
length of the prong in the coil. The length of the prong may then
be used to identify the specific type of instrument being used.
[0029] The following example demonstrates how the coil impedance
and inductance may be used to determine prong length to identify a
particular instrument 110. The coil impedance may be determined
using formula (I)
Z.sub.COIL=R.sub.COIL+jwL.sub.COIL (I)
where Z.sub.COIL is the measured voltage/measured current,
R.sub.COIL is the DC resistance of the coil, L.sub.COIL is the coil
inductance, j is the imaginary unit with the property j*j equal to
-1, and w is the angular frequency of the driving voltage and is
equal to 2.pi.f, where f is the driver voltage frequency.
[0030] Prior to attaching the instrument 110 to the receiver 120,
L.sub.COIL may be measured as that of an air-core solenoidal coil.
It can be calculated according to formula (II)
L.sub.COIL=K(h)mu.sub.0N.sup.2A/h (II)
where K(h) is the Nagaoka coefficient for coil length h, mu.sub.0
is permeability of free space, N is the number of coil turns, and A
is the coil cross sectional area. When the instrument 110 is
attached to the receiver 120, the prong 112 enters the coil 126 by
an instrument-specific distance d (such as d.sub.a, d.sub.b,
d.sub.c, as described herein and shown in FIGS. 3-5). Since the
relative permeability of the prong material (mu) is greater than
that of air, the coil inductance increases. As a result, the phase
and magnitude of Z.sub.an changes. For an attached instrument, the
coil inductance can be approximated using formula (III)
-L.sub.COIL=K(h-d)mu.sub.0[N[h-d]/h].sup.2A/[h-d].+-.mu.sub.prongF.sub.L-
mu.sub.0[Nd/h].sup.2A/d (III)
which can be simplified to the formula (IV)
L.sub.COIL=K(h-d)mu.sub.0N.sup.2A[h-d]/h.sup.2.+-.mu.sub.prongF.sub.Lmu.-
sub.0N.sup.2Ad/h.sup.2 (IV)
and further simplified to the formula (V)
L.sub.COIL=N.sup.2mu.sub.0A/h.sup.2[K(h-d)[h-d].+-.mu.sub.prongF.sub.Ld]
(V)
where mu.sub.prong is the apparent relative permeability of the
prong which depends on mu and the ratio of prong length and
diameter, and F.sub.L is a factor that depends on the ratio of the
prong length d and the pronghole depth h.
[0031] For example, in the embodiments shown in FIG. 4, the
following values for an instrument with a 5 mm prong can be
assumed: h=10 mm; coil core diameter=2 mm; N=500; mu=10 (stainless
steel); mu.sub.prong=5.5; d.sub.c=5 mm; K(h)=0.91; K(h-d)=0.84; and
F.sub.L=0.72. For these values, L.sub.COIL prior to the instrument
attachment is L.sub.COIL=0.09 mH. After the instrument attachment,
a value of L.sub.COIL=0.24 mH is obtained. Assuming a coil wire
thickness of 42 AWG, the DC resistance of approximately
R.sub.COIL=20 Ohms is obtained. If the coil is driven at a
frequency of f=10 kHz, the value obtained prior to instrument
attachment is Z.sub.COIL=20 Ohms+j 5.6 Ohms. After attachment, the
value obtained is Z.sub.COIL=20 Ohms+j 14.9 Ohms. Thus, the
magnitude of Z.sub.COIL increased by a factor of about 1.2, and the
phase increases from about 15.6 degrees to about 36.7. Such an
increase is well above the resolution of available current and
voltage measurement technology.
[0032] Thus, the sensitivity of Z.sub.COIL may be affected by the
prong length, d. The higher this sensitivity, the easier it may be
to differentiate between prongs 112 of different lengths (such as
the prongs 112a, 112b, and 112c of FIGS. 3-5). A higher sensitivity
may indicate that more distinct instrument geometries (i.e. prong
lengths) may be accommodated for a given coil depth. The
sensitivity to the prong length d may be partially derived from
L.sub.COIL as delta L.sub.COIL/delta d=N.sup.2 mu.sub.0A/h.sup.2
[mu.sub.prong F.sub.L-K(h-d)] which is 0.031 mH/mm. In terms of
Z.sub.COIL, a delta Z.sub.COIL/delta d=jw 0.031 mH/mm is obtained.
For a given frequency of 10 kHz, a delta Z.sub.COIL/delta d=j 1.9
Ohms/mm is then arrived at. In summary, the sensitivity to various
prong lengths d may be increased by increasing frequency, or
choosing a prong material with higher permeability. And increasing
sensitivity may allow for a wider range of prong lengths to more
accurately identify different types of instruments and instruments
configurations.
[0033] In some configurations, the instrument assembly 100 may
include more than one prong 112 and corresponding additional coils
126. The additional prongs 112 may be of the same or different
lengths to further provide variation in the possible numbers and
variety of instruments 110 that may be used with the receiver 120.
The additional prongs 112 may also function to releasably secure
the receiver 120 to the instrument 110. The instrument assembly 100
may also include other features (not shown) that hold the receiver
120 to the instrument 110, such as detents, bias clips, bands,
etc., or any feature that would removably hold receiver 120 in
contact with instrument 110.
[0034] FIG. 6 shows a simplified circuit 200 that may operate to
determine the inductance of the coil 126,
Z.sub.COIL=R.sub.COIL+jwL.sub.COIL in some embodiments. V.sub.1 may
measure voltage across the coil 126, and V.sub.2 may be used to
determine coil current. The current signal may be measured by
sensing the voltage across resistor R.sub.Sens. The AC voltage
V.sub.Drive may energize the coil 126.
[0035] Thus, by using different prong lengths, permeabilities,
etc., instruments with various configurations and types can be
easily and automatically identified by electromagnetic surgical
navigation system 10. The prong and coil configurations described
herein offer the advantage of a simple, reliable, and compact
automatic instrument identification system for interchangeable
instruments. Because of the robust design of a prong and encased
coil, instruments and receivers may be used multiple times without
significant risk of misidentification.
[0036] The automatic identification system described herein may
simplify the process for a user to use and calibrate.
Conventionally, when different instruments are used with
electromagnetic tracking systems, the system must be calibrated to
the known physical size and shape of the particular instrument
being used so it will be properly represented on the display.
Hall-effect sensors in a receiver and permanent magnets organized
in a particular pattern in the instruments have sometime been used
to identify the different instruments. However, the Hall-effect
sensors can require significant space requirements necessitating a
large receiver, and the permanent magnets may become dislodged or
otherwise unaligned such that proper identification of the
instrument may be compromised.
[0037] In addition to any previously indicated modification,
numerous other variations and alternative arrangements may be
devised by those skilled in the art without departing from the
spirit and scope of this description, and appended claims are
intended to cover such modifications and arrangements. Thus, while
the information has been described above with particularity and
detail in connection with what is presently deemed to be the most
practical and preferred aspects, it will be apparent to those of
ordinary skill in the art that numerous modifications, including,
but not limited to, form, function, manner of operation and use may
be made without departing from the principles and concepts set
forth herein. Also, as used herein, the examples and embodiments,
in all respects, are meant to be illustrative only and should not
be construed to be limiting in any manner.
* * * * *