U.S. patent application number 09/117802 was filed with the patent office on 2002-03-14 for medical probes with field transducers.
Invention is credited to ACKER, DAVID E., BEJERANO, YANIV.
Application Number | 20020032380 09/117802 |
Document ID | / |
Family ID | 27452482 |
Filed Date | 2002-03-14 |
United States Patent
Application |
20020032380 |
Kind Code |
A1 |
ACKER, DAVID E. ; et
al. |
March 14, 2002 |
MEDICAL PROBES WITH FIELD TRANSDUCERS
Abstract
A field transducer (30) for determining position or orientation
in a medical instrument locating system is placed at an arbitrary
position or orientation with respect to a feature (62) of the
instrument (46). The transducer (30) may be attached at an
arbitrary location on the instrument (46), or the instrument (400,
404) may be bent as desired by the user. A transform relating
position or orientation of a feature of the instrument to position
or orientation of the transducer is obtained in a calibration
cycle. A field transducer may be part of a disposable unit which is
irrevocably altered when used with an instrument, so that the unit
cannot be reused.
Inventors: |
ACKER, DAVID E.; (SETAUKET,
NY) ; BEJERANO, YANIV; (HAIFA, IL) |
Correspondence
Address: |
AUDLEY A CIAMPORCERO JR
ONE JOHNSON & JOHNSON PLAZA
NEW BRUNSWICK
NJ
089337003
|
Family ID: |
27452482 |
Appl. No.: |
09/117802 |
Filed: |
December 10, 1998 |
PCT Filed: |
February 14, 1997 |
PCT NO: |
PCT/US97/02443 |
Current U.S.
Class: |
600/439 |
Current CPC
Class: |
A61B 1/00062 20130101;
A61B 2090/0814 20160201; A61B 1/31 20130101; A61B 2017/22008
20130101; A61M 25/0127 20130101; A61B 8/0841 20130101; A61B 1/00055
20130101; A61B 90/36 20160201; A61B 2090/3929 20160201; A61B
1/00059 20130101; A61B 2090/363 20160201; A61B 5/065 20130101; A61B
2560/0276 20130101; A61B 8/0833 20130101; A61M 2025/1052 20130101;
A61B 17/22012 20130101; A61B 2034/2072 20160201; A61M 2025/0166
20130101; A61B 17/3403 20130101; A61B 2034/2051 20160201; A61B 5/06
20130101; A61B 2562/08 20130101; A61M 25/0023 20130101; A61M
2025/0025 20130101; A61B 8/4254 20130101; A61B 2017/00482 20130101;
A61M 25/10 20130101; A61B 2090/3958 20160201; A61B 2018/00988
20130101; A61B 90/90 20160201; A61B 17/3415 20130101; A61B 90/39
20160201; A61B 5/283 20210101; A61B 2018/00178 20130101; A61B
2017/00725 20130101; A61B 34/20 20160201; A61B 10/02 20130101 |
Class at
Publication: |
600/439 |
International
Class: |
A61B 005/05 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 17, 1996 |
IL |
119262 |
Claims
What is claimed is:
1. A method of configuring and operating a probe comprising the
steps of: (a) providing a probe including a first field transducer
and a probe body so that the field transducer is disposed in an
arbitrary, user-selected disposition relative to a feature of the
probe body; (b) while said feature of the probe body is at a known
disposition in said frame of reference, determining a calibration
disposition of the field transducer in a frame of reference by
transmitting one or more non-ionizing fields between the first
field transducer mounted on the probe body and one or more
reference field transducers mounted in said frame of reference and
monitoring one or more characteristics of the fields at one or more
of said transducers; (c) determining a transform between
disposition of said field transducer and disposition of said
feature of said probe body from said calibration disposition and
said known disposition; and thereafter (d) determining the
disposition of said feature of the probe by (1) determining the
disposition of the first field transducer by transmitting one or
more non-ionizing fields between the first field transducer and
said reference field transducers and monitoring one or more
characteristics of the fields and (2) applying said transform to
the so-determined disposition of the first field transducer.
2. A method as claimed in claim 1 wherein said step of providing
said probe includes the step of adjusting said probe body to a
user-selected configuration.
3. A method as claimed in claim 2 wherein said adjusting step
includes the step of deforming the probe body.
4. A method as claimed in claim 3 wherein said probe body includes
an elongated pointer and said deforming step includes the step of
bending the pointer.
5. A method as claimed in claim 4 wherein said bending step is
performed so as to form the pointer to a generally J-shaped
configuration.
6. A method as claimed in claim 1 wherein the step of providing
said probe includes the step of affixing the first field transducer
to the probe body in a location on the body selected by the
user.
7. A method as claimed in claim 1 further comprising the step of
finding at least one said known disposition by transmitting one or
more non-ionizing fields between a field transducer and said
reference field transducers and monitoring one or more
characteristics of the fields while such field transducer is
engaged with an object having a fixed position in said field of
reference.
8. A method as claimed in claim 7 wherein the field transducer used
in said step of finding at least one said known disposition is said
first field transducer.
9. A method as claimed in claim 1 further comprising the step of
repeating said steps (b) and (c) using a plurality of different
features of said probe to thereby determine a transform between the
disposition of said first field transducer and the disposition of
each of said features, and, in step (d), determining the
dispositions of all of said plural features.
10. A method as claimed in claim 9 further comprising the step of
displaying an image of said probe including representations of all
of said features, each such representation being disposed at a
location in said image corresponding to a position of such feature
determined in step (d).
11. A method as claimed in claim 10 wherein said step (d) is
performed while the probe is at least partially disposed in or on
the body of a medical patient, the method further comprising the
step of superposing said image on an image of the patient in
registration therewith.
12. A method as claimed in claim 1 further comprising the steps of
repeating steps (b) and (c) for the same feature of said probe
using different known dispositions of said feature, whereby
different calibration dispositions of said first field transducer
are determined during different repetitions, and calculating said
transform from a plurality of said calibration dispositions and a
plurality of said known dispositions.
13. A component for use in a medical probe system comprising: (a) a
field transducer for detecting or radiating a non-ionizing field so
that the disposition of the field transducer can be at least
partially determined from properties of such field; and (b) a
selectively operable mounting element adapted to secure the field
transducer to a body of a medical instrument so that the
disposition of the transducer relative to the body of the
instrument can be selected from among a range of dispositions.
14. A component for use in a medical probe system comprising: (a) a
field transducer for detecting or radiating a non-ionizing field so
that the disposition of the field transducer can be at least
partially determined from properties of such field; and (b) a
selectively operable mounting element adapted to secure the field
transducer to any one of a plurality of different medical
instruments having bodies of different configurations.
15. A component as claimed in claim 13 or claim 14 wherein said
mounting element includes an adhesive for bonding the field
transducer to the instrument body.
16. A component as claimed in claim 13 or claim 14 wherein said
mounting element includes a clip attached to the field transducer
and adapted to grip an instrument body to thereby mechanically
connect the field transducer to the instrument body.
17. A disposable device comprising: (a) a field transducer for
detecting or radiating a non-ionizing field so that the disposition
of the field transducer can be at least partially determined from
properties of such field; (b) a mounting element for securing the
field transducer to a medical instrument, said mounting element
being adapted to engage a body of a medical instrument releasably
so that said field transducer can be removed from the instrument
but such removal cannot be accomplished readily without altering at
least one feature of the disposable device.
18. A device as claimed in claim 17 wherein said mounting element
is adapted to engage the instrument so that said device cannot be
removed readily from the instrument without deforming a part of the
mounting element.
19. A device as claimed in claim 17 wherein device includes an
electrical circuit element and said mounting element is adapted to
engage the instrument so that said device cannot be removed readily
from the instrument without altering said electrical circuit
element.
20. A device as claimed in claim 19 wherein said electrical circuit
element constitutes a part of said field transducer.
21. A device as claimed in claim 17 or claim 18 or claim 19 or
claim 20 wherein said mounting element includes features having a
predetermined configuration adapted to engage features of the
instrument so as to support the field transducer in a predetermined
disposition relative to the instrument.
22. A disposable device according to claim 21 wherein said mounting
element includes a body housing said field transducer, said body
having at least one appendage, said body being adapted to engage a
cavity in the instrument with said appendage engaged in the
instrument such that said body cannot be removed readily from the
cavity without irreversibly deforming said appendage.
23. A disposable device comprising: (a) a field transducer for
detecting or radiating a non-ionizing field so that the disposition
of the field transducer can be at least partially determined from
properties of such field; (b) a mounting element for securing the
field transducer to a medical instrument; and (c) an electrical
circuit element bearing information specific to the individual
disposable device.
24. A device according to claim 23 wherein said electrical circuit
element bears calibration information related to the individual
disposable device.
25. A device as claimed in claim 23 wherein said electrical circuit
element bears information identifying the individual disposable
device.
26. A device as claimed in claim 23 wherein said electrical circuit
element bears information indicating whether the disposable device
has been used.
27. A disposable device comprising: (a) a field transducer for
detecting or radiating a non-ionizing field so that the disposition
of the field transducer can be at least partially determined from
properties of such field; (b) a mounting element for securing the
field transducer to a medical instrument; and (c) means for
detecting information on the instrument specifying one or more
characteristics of the instrument.
28. A device as claimed in claim 27 wherein said detecting means
includes means for detecting information on the instrument denoting
a type of instrument.
29. A pointing device comprising: (a) an elongated probe body
having a formable region which can be selectively deformed to a
desired shape and which will tend to remain in such shape after
deformation; and (b) a field transducer on said probe body for
detecting or radiating a non-ionizing field so that the disposition
of the field transducer can be at least partially determined from
properties of such field.
30. A pointing device as claimed in claim 29 wherein said probe
body includes a flexible region more flexible than said formable
region disposed at a distal end of the probe body and selectively
operable means at for deflecting said flexible region to a curved
configuration, and wherein said field transducer is mounted on said
flexible region.
31. A method of performing a procedure within the body of a
mammalian subject comprising the steps of deforming the formable
region of a probe as claimed in claim 29 or claim 30 to a
configuration corresponding to the configuration of organs within
the subject based upon image data showing said organs, and then
inserting the probe into said subject.
32. A method as claimed in claim 31 wherein said the probe is
inserted between the brain and the dura of said subject.
33. A method of probing the body of a mammalian subject comprising
the steps of advancing a distal end of a substantially flaccid,
elongated probe having a field transducer adjacent said distal end
between the brain and dura of said subject while monitoring the
position of said distal end by detecting non-ionizing fields
transmitted to of from said field transducer.
Description
TECHNICAL FIELD
[0001] The present invention relates to medical probes having field
transducers used for detecting the disposition of the probe, and to
the medical procedures utilizing such probes.
BACKGROUND OF THE INVENTION
[0002] Conventional surgical procedures involve cutting through
bodily structures to expose a lesion or organ within the body for
treatment. Because these procedures create considerable trauma to
the patient, physicians have developed minimally invasive
procedures using probes inserted into the body. For example,
devices commonly referred to as endoscopes include an elongated
body having a distal end and a proximal end. The distal end of the
probe body can be inserted into the gastrointestinal tract through
a body orifice. The endoscope may be equipped with optical devices
such as cameras or fiber optics to permit observation of the
tissues surrounding the distal end, and surgery may be performed by
inserting and maneuvering surgical instruments through a channel in
the endoscope body. Other probes commonly referred to as
laparoscopes and arthroscopes are inserted into the body through
small holes formed in surrounding tissues to reach the bodily
structures to be treated or measured. Still other probes, commonly
referred to as catheters, can be advanced through the vascular
system, as through a vein or artery, or through other bodily
passages such as the urinary tract.
[0003] The physician can guide the probe to the desired location
within the body by feel or by continuously imaging the probe and
the body, as by fluoroscopy, during the procedure. Where the probe
includes optical elements, the physician can guide the probe based
on visual observation of the tissues surrounding the distal tip of
the probe. However, this option is available only for probes such
as conventional endoscopes which are large enough to accommodate
the optical elements.
[0004] As described, for example, in U.S. Pat. Nos. 5,558,091,
5,391,199; 5,443,489; and in PCT International Publication WO
96/05768 Application PCT/US 95/01103, the disclosures of which are
hereby incorporated by reference herein, the disposition of a probe
- - - its position, orientation, or both - - - can be determined by
using one or more field transducers such as a Hall effect or
magnetoresistive device, coil or other antenna carried on the
probe, typically at or adjacent the distal end of the probe, or at
a precisely known location relative to the distal end of the probe.
One or more additional field transducers disposed outside the body
in an external frame of reference. The field transducers preferably
are arranged to detect or transmit non-ionizing fields or field
components such as a magnetic field, electromagnetic radiation or
acoustical energy such as ultrasonic vibration. By transmitting the
field between the external reference field transducers and the
field transducers on the probe, characteristics of field
transmission between these devices can be determined. The position
and/or orientation of the field transducer, in the external frame
of reference can be deduced from these transmission
characteristics. As the field transducer is mounted to the probe,
the position of the probe can be determined by determining the
position of the field transducer in the external frame of
reference. Because the field transducer allows determination of the
position of the probe, such a transducer is also referred to as a
"position sensor".
[0005] As described, for example, in the aforementioned U.S. Pat.
No. 5,558,091, the frame of reference of the external field
transducers can be registered with the frame of reference of
imaging data such as magnetic resonance imaging data, computerized
axial tomographic data, or conventional x-ray image data and hence
the position and orientation data derived from the system can be
displayed can as a representation of the probe superimposed on an
image of the patient's body. The physician can use this information
to guide the probe to the desired location within the patient's
body, and to monitor its orientation during treatment or
measurement of the body structure. This arrangement greatly
enhances the ability of the physician to navigate the distal end of
the probe through bodily structures. It offers significant
advantages over conventional methods of navigating probes by feel
alone. Because it does not require acquisition of an optical image
of the surrounding tissues for navigation purposes, it can be used
with probes which are too small to accommodate optical elements.
The transducer-based system avoids the difficulties associated with
navigation of a probe by continuous imaging of the probe and
patient during the procedure. For example, it avoids exposure to
ionizing radiation inherent in fluoroscopic systems.
[0006] However, still further improvements in transducer-based
probe navigation and treatment systems would be desirable. In
particular, it would be desirable to provide greater versatility in
probe configurations. Thus, the diverse medical procedures require
numerous different tools for use within the body. It would be
desirable if any such tool could be guided and located in the same
manner as the probes discussed above, without the need to adapt or
redesign the tool to a accommodate the field transducer or position
sensor. It would also be desirable to provide probes in diverse
configurations matching different anatomical structures. Merely by
way of example, it is sometimes desirable to advance a relatively
stiff probe through anatomical structures defining a path having a
particular radius of curvature unique to the patient. It is
impractical to stock transducer-equipped probes in all of the
various configurations required to accommodate different patients.
Also, because field transducers can be impaired by exposure to
certain sterilization processes, it would be desirable to provide
single-use or limited-use field transducers which can be applied to
an instrument.
DISCLOSURE OF INVENTION
[0007] The present invention addresses these and other needs.
[0008] One aspect of the present invention provides methods of
configuring and operating a probe. A method according to this
aspect of the invention preferably includes the steps providing a
probe including a first field transducer and a probe body so that
the field transducer is disposed in an arbitrary, user-selected
disposition relative to a feature of the probe body, such as at an
arbitrary disposition relative to the distal end of the probe body.
The probe is calibrated by placing the aforesaid feature of the
probe body at one or more known dispositions in the frame of
reference defined by the external or reference field transducers of
the system. While this feature of the probe body is in such known
disposition, one or more calibration dispositions of the field
transducer in the reference-transducer frame of reference is or are
determined by transmitting one or more non-ionizing fields between
the first field transducer mounted on the probe body the reference
field transducers and monitoring one or more characteristics of the
fields at one or more of said transducers. The calibration process
further includes the step of determining a transform between
disposition of the first field transducer and disposition of said
feature of said probe body from said one or more calibration
dispositions and said one or more known dispositions. After the
calibration steps, disposition of said feature of the probe is
determined by (1) determining the disposition of the first field
transducer by transmitting one or more non-ionizing fields between
the first field transducer and said reference field transducers and
monitoring one or more characteristics of the fields and (2)
applying said transform to the so-determined disposition of the
first field transducer.
[0009] Because the transform between disposition of the first field
transducer and disposition of the probe body feature is determined
during the calibration cycle, there is no need for any particular,
predetermined spatial relationship between the first field
transducer or position sensor and the distal end or other feature
of the probe body to be tracked by the system during use. All that
is required is that the spatial relationship remain fixed after
calibration. Thus, according to this aspect of the invention, there
is no need for any special configuration of the probe body;
provided that the first field transducer or position sensor can be
securely attached to a medical instrument of any type which can be
inserted into the patient or contacted with the patient, that
medical instrument can serve as an instrumented probe. This aspect
of the invention allows the physician to use existing tools and to
track the disposition of existing tools in the same manner as a
specialized sensor-equipped probe.
[0010] The step of providing the probe can include the step of
adjusting the probe body to a user-selected configuration, as by
bending or otherwise deforming the probe body. In one preferred
arrangement, the probe body includes a formable section which can
be bent manually by the physician into a desired configuration
after review of an image showing the relevant anatomical features,
but which thereafter retains its shape. The probe is calibrated
after bending. Thus, even if the sensor or first field transducer
is mounted remote from the distal tip, the position of the distal
tip can be tracked with sufficient accuracy to allow navigation of
the tip through the anatomy. In effect, the physician can
custom-form a probe as needed for any procedure. A further aspect
of the present invention provides a pointing device or probes with
a formable distal regions and with a field transducer or position
sensor at the distal end, so that the position of the distal end
can be monitored even without calibration as discussed above.
[0011] The known disposition used in the calibration cycle can be
determined using the first field transducer, without the other
elements of the probe, as by engaging the first field transducer
with a fixed object in the external reference frame and determining
disposition of the first field transducer.
[0012] A related aspect of the present invention provides
components for use in a medical probe system. One component
according to this aspect of the invention includes a field
transducer as referred to above and a selectively operable mounting
element adapted to secure the field transducer to a body of a
medical instrument so that the disposition of the field transducer
relative to the body of the instrument can be selected from among a
range of dispositions. Preferably, such range includes all
positions on the body; i.e., the mounting element can secure the
field transducer anywhere on the instrument body. A component
according to a further, related aspect of the invention includes
the field transducer with a selectively operable mounting element
adapted to secure the field transducer to any one of a plurality of
different medical instruments having bodies of different
configurations. In components according to these aspects of the
invention, the mounting element may include an adhesive for bonding
the field transducer to the instrument body, or else may include a
clip attached to the field transducer, the clip being adapted to
grip an instrument body.
[0013] The calibration steps can be repeated several times for a
single feature of the probe body, using the same or different known
dispositions and calibration dispositions, so as to enhance the
accuracy of the calibration process. Alternatively or additionally,
the calibration steps can be performed using more than one feature
of a probe, so that a separate transform is developed for each
feature. During use, the system can track all of the features for
which such calibration steps were performed. For example, where a
probe is bent to a user-defined shape, the calibration step can be
performed for many points along the probe, and the system can
display locations of these many points during use. Thus, the system
can display a realistic depiction of the user-defined shape. A
disposable device according to a further aspect of the invention
includes a field transducer as discussed above, and a mounting
element for securing the field transducer to a medical instrument,
the mounting element being adapted to engage a body of the medical
instrument so that said disposable device cannot be removed readily
from the instrument without altering at least one feature of the
disposable device. For example, the mounting element may be adapted
to engage the instrument so that said device cannot be removed
readily from the instrument without deforming or breaking a part of
the mounting element. Devices according to related aspects of the
invention incorporate the field transducer, a mounting element and
a usage monitoring circuit element for recording use of the device.
Thus, the usage monitoring circuit element may provide an
indication representing the number of times the disposable device
has been used or the total time the disposable device has been
operatively used. These arrangements help to prevent improper reuse
of the device.
[0014] The present invention will be better understood from the
following detailed description of preferred embodiments of the
invention, taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0015] FIG. 1 is a diagrammatic perspective view depicting a device
in accordance with one embodiment of the invention.
[0016] FIG. 2 is a diagrammatic perspective view depicting the
device of FIG. 1 in conjunction with a medical instrument.
[0017] FIG. 3 is a further diagrammatic perspective view depicting
the instrument and device of FIG. 1 and in conjunction with
additional components and a medical patient.
[0018] FIG. 4 is a further diagrammatic perspective view depicting
a device in accordance with another embodiment of the
invention.
[0019] FIG. 5 is a diagrammatic end elevational view depicting
components in accordance with a further embodiment of the
invention.
[0020] FIG. 6 is a diagrammatic side elevational view depicting the
components of FIG. 5.
[0021] FIG. 7 is a schematic, top view, illustration of a surgical
instrument having mounted thereon a disposable device, in
accordance with a further embodiment of the present invention;
[0022] FIG. 8 is a schematic, partly cross-sectional, side-view,
illustration of the surgical instrument of FIG. 7.
[0023] FIG. 9 is a diagrammatic sectional view depicting apparatus
in accordance with a further embodiment of the invention.
[0024] FIG. 10 is a diagrammatic sectional view depicting apparatus
in accordance with yet another embodiment of the invention.
[0025] FIG. 11 is a diagrammatic sectional view depicting apparatus
in accordance with a further embodiment of the invention.
[0026] FIG. 12 is a diagrammatic elevational view depicting the
apparatus of FIG. 11 in conjunction with a medical instrument.
[0027] FIG. 13 is a diagrammatic view depicting the apparatus of
FIG. 11 in conjunction with another medical instrument.
MODES FOR CARRYING OUT THE INVENTION
[0028] A disposable device in accordance with one embodiment of the
invention includes a field transducer 30 permanently mounted in a
body 32. Field transducer 30 is adapted to detect or radiate a
non-ionizing field such as a magnetic, electromagnetic or acoustic
field in such a manner that disposition of the field transducer can
be at least partially determined from properties of the detected or
radiated field. Field transducer or sensor 30 may be a multiaxis,
solid-state position sensor of the type disclosed in U.S. Pat. No.
5,558,091. Such a multiaxis sensor includes a plurality of
transducers sensitive to magnetic field components in mutually
orthogonal directions. Other suitable field transducers or sensors
include coils as disclosed in the aforementioned U.S. Pat. No.
5,391,199 and PCT International Publication WO 95/05768,
incorporated by reference herein. The coils may be provided as a
single coil having a single axis of sensitivity or as a plurality
of mutually orthogonal coils capable of detecting electromagnetic
field components in orthogonal directions. The sensor or field
transducer 30 is provided with an appropriate cable 34 having a
terminal block or plug 35.
[0029] Body 30 is mechanically connected to or molded integrally
with a polymeric clip 38. Clip 38 includes a pair of opposed legs
40 and 42 and a integral clasp 44 for holding the legs 40 and 42 in
a closed position in which the legs are adjacent to one another.
Clip 38 may be molded integrally with body 32 or else may be
attached to the body by any suitable mechanical fastener, adhesive
or bonding procedure. Clip 32 is adapted to encircle a part of a
medical instrument or probe and grasp the encircled part between
legs 40 and 42. For example, a conventional surgical forceps 46 has
a pair of opposed elongated arms 48 and 50. Arm 48 can be grasped
between opposed legs 40 and 42 of the clip. When clasp 44 is
engaged with leg 40, legs 40 and 42 are forcibly engaged on
opposite sides of arm 48 and tightly grip arm 48 so as to hold body
32, and hence field transducer or position sensor 30. Clip 38 is
capable of engaging arm 48 at any point along its length selected
by the user and of course is capable of engaging any other
elongated implement which can be placed between legs 40 and 42.
[0030] The apparatus further includes a set of reference field
transducers or antennas 52 (FIG. 3) mounted in a frame of reference
external to the patient. For example, field transducers 52 may be
mounted to a patient-supporting bed. Antennas 52 are linked to a
field transmitting and receiving device 54 and a computer 56, which
in turn is linked to a displayed device such as a cathode ray tube
58. These elements are arranged to cooperate with field transducer
30 or other movable field transducers or position sensors, to
determine the dispositions of the movable field transducer in the
frame of reference of the external field transducers or antennas.
These elements of the apparatus can be as described in the
aforementioned '091 or '199 patents. Other devices for detecting
disposition of probes equipped with position sensors by
transmission of non-ionizing fields are known in the art. As is
known in the art, electromagnetic or magnetic fields can be
transmitted between an antenna or field transducer mounted in a
frame of reference and a movable position sensor or field
transducer, and the disposition of the movable field transducer can
be calculated from the characteristics of the transmitted. Thus,
the external field transducers or antennas 52 and the movable
position sensor or field transducer 30 cooperatively define a
plurality of transmitter-receiver pairs. Each such pair includes
one transmitter and one receiver as elements of the pair. One
element of each such pair is disposed at an unknown disposition and
the other element of each such pair is disposed at a known
disposition in the external frame of reference. Typically, at least
one element of each transmitter-receiver pair is disposed at a
different position or orientation than the corresponding element of
the other pairs. By detecting the characteristics of field
transmission between elements of the various pairs, the system can
deduce information concerning the disposition of the field
transducer in the external frame of reference. The disposition
information can include the position of the movable field
transducer, the orientation of the movable field transducer or
both.
[0031] In a method according to one embodiment of the invention,
the physician first places device 28, and hence field transducer 30
at any convenient reproducible disposition within the frame of
reference established by reference field transducers or antennas 52
as, for example, by abutting body 32 (FIG. 1) against some fixed
object 60 in the vicinity of the reference of field transducers.
Object 60 may be any object which does not interfere with a
transmission of the fields as, for example, a non-magnetic object
when electromagnetic fields are used. Object 60 need not be any
specially configured or placed element. However, if desired object
60 may be especially configured to engage body 32 in a precise,
reproducible manner as, for example, to engage a particular edge or
feature of body 32.
[0032] Alternatively, object 60 may be configured so that it can be
engaged by clip 38. In either case, device 28 and hence the movable
field transducer or position sensor 30 is held in a fixed
calibration or reference position and orientation. The field
transmitting and receiving unit 54 and computer 56 are then
actuated in the normal manner to determine the position and
orientation of the movable or first field transducer 30 within
device 28. In this step the system determines the position of
object 60 in the frame of reference of reference field transducers
or antennas 52 using device 28 and the first or movable field
transducer 30. Thus, the position of object 60 is a known position.
In particular, object 60 may include a tip, edge or hole, and the
location of such tip edge or hole is known.
[0033] Device 28 is then attached to a medical instrument or probe
46 using clasp 38. A convenient feature of the instrument or probe
to be tracked is selected by the physician. Such feature should be
at a location on the instrument or probe which is rigidly connected
to the location where device 28 is attached. For the particular
forceps illustrated in FIG. 2, the feature to be tracked is the
distal end 62 of the same arm 48 on which device 28 is mounted. The
user then engages the preselected feature of the probe or
instrument, such as distal tip 62 with fixed object 60 so as to
place this feature of the instrument or probe 46 in a known
position such as on the tip, edge or hole of object 60. That is,
the feature 62 of the probe or instrument 46 is in the same known
disposition as previously occupied by the first field transducer 30
and device 28. While the selected feature of the instrument is in
this known disposition, the field transmit and receive unit is
actuated once again to record a calibration disposition of first
field transducer 30, i.e., the position and orientation of the
first field transducer while tip 62 is disposed in engagement with
object 60. Based on the calibration disposition of the first field
transducer 30 and the known disposition of feature 62, the system
calculates a transform between the position of first field
transducer 30 and the position of feature or tip 62 on the
instrument body.
[0034] Because arm 48 is a rigid body, there is a constant vector
V.sub.p relating the position P.sub.p of the first field transducer
30 to the position P.sub.t of the tip or feature 62. The
relationship is
P.sub.t=P.sub.p+O.sub.p.sup.-1V.sub.p (1)
[0035] where O.sub.p is the orientation matrix defining the
orientation of the first field transducer 30 in the frame of
reference defined by reference transducers 52. When the tip or
feature 62 is in the known position in engagement with object 60,
P.sub.t=P.sub.0 where P.sub.0 is the known position of feature 62,
i.e., the position of object 60. Also, because the system
determines the calibration disposition of first field transducer 30
in this condition, including both the position and orientation of
the first field transducer, the values of P.sub.p and O.sub.p are
also known. That is:
P.sub.0=P.sub.1+O.sub.1.sup.-1V.sub.p (2)
[0036] Where: P.sub.1 represents the measured calibration position
of the first field transducer in the calibration condition and
O.sub.1 represents the measured orientation of the first field
transducer in the calibration condition. This equation is solved
for vector V.sub.p:
V.sub.pO.sub.1(P.sub.0-P.sub.1) (3)
[0037] The calculated value of V.sub.p represents a transform
between position and orientation of the first field transducer 30
or device 28 and the position of feature 62 on the instrument body.
At this point, the calibration cycle is complete. The calibration
steps may be repeated while keeping tip or feature 62 in the same
position, in engagement with object 60, but varying the orientation
of the instrument body, so as to bring the first field transducer
30 to a new calibration disposition, such as a new position and
orientation, and repeating the steps required to derive vector Vp
from the new calibration disposition. Alternatively or
additionally, the calibration steps may be repeated using one or
more additional known positions of tip or feature 62. Thus,
additional objects (not shown) may be provided at known positions
within the frame of reference of the reference field transducers
52, and tip 62 may be engaged with each of these additional objects
to establish an additional known position of the tip. While the tip
is at each additional known position, the position and orientation
of the first field transducer are recorded as discussed above to
establish one or more additional calibration dispositions of the
field transducer for each additional known disposition of tip 62.
Here again, vector Vp is recalculated for each calibration
disposition. The results of the various calculations can be
combined with one another, to establish a best estimate for Vp. For
example, Vp can be calculated by averaging the results for each
component of the vector or, preferably, by selecting a vector value
of Vp to yield the least mean square error with respect to the
individually-calculated values. Additionally, the calibration can
be tested by placing tip 62 on one or more additional known
locations, such as on one or more additional objects, computing the
position of the tip based upon the disposition of the field
transducer and vector Vp, and then comparing the computed position
and the known location. An alarm signal can be issued, or system
operation can be inhibited, if the two locations differ by more
than a preselected tolerance.
[0038] Following the calibration cycle, the system continues to
monitor the position and orientation of the first field transducer
30 and hence of device 28. The system continually applies the
transform or vector V.sub.p determined during the calibration cycle
in equation (1), above, using new measured values of the position
P.sub.p and orientation O.sub.p of the first field transducer 30
and thus determines the location P.sub.t of feature 62 in the frame
of reference defined by reference transducers 52. This positional
information can be treated in a known manner by computer 56 as, for
example, to superpose a representation of feature 62 on image data
showing a medical patient. As described, for example, in the
aforementioned '091 patent, information concerning position and/or
orientation of an object in the frame of reference defined by
transducer 52 can be registered to the frame of reference of a
previously acquired image using additional field transducers or
position sensors 70. Thus, the system can display a representation
62' on display screen 58 in registry with the previously acquired
image such as an MRI, CT or similar image. Alternatively, as
described in U.S. Provisional Application 60/012,275 filed Feb. 26,
1996, the disclosure of which is incorporated by reference herein
and as further described in co-pending, commonly assigned PCT
Application entitled, Medical Procedures and Apparatus Using
Intrabody Probes, filed of even date herewith and claiming priority
from the aforesaid '275 Provisional Application, the disclosure of
which is hereby also incorporated by reference herein, the
information concerning position of feature 62 may be used to
calculate the position of feature 62 relative to another probe
advanced within the body and this information may be provided to
the physician so that feature 62 can be guided or pointed toward
such other probe.
[0039] A pseudocode description and accompanying algorithms are set
forth in the appendix at the end of the present specification.
Although the foregoing discussion provides for recovery of only the
position of feature 62, and not its orientation, the orientation
can be derived in the same manner. Thus, during the calibration
cycle, the instrument can be held in a known orientation as, for
example, by holding a known edge 64 of arm 48 in engagement with a
particular face or feature of object 60. The computer can then
calculate a direct transform between matrix O.sub.p defining the
orientation of the first field transducer 30 and the orientation
matrix defining the direction of edge 64 and hence defining the
orientation of the probe or instrument 46. Here again, a
calibration value O.sub.1 for matrix O.sub.p is determined by
measuring O.sub.p while the probe is in the known disposition and
field transducer 34 is in the corresponding calibration
disposition. Prior to this step, the known orientation of the face
or feature of object 60 is established, as by measuring the
orientation of device 28 while an edge of device body 32 is engaged
with the face or feature of object 60.
[0040] The step of measuring the position and/or orientation of
object 60 using device 28 may be omitted if the location of object
60 relative to reference transducers 52 is already known as, for
example, where the object is supplied in a rigid unit with the
transducers. Conversely, the location of object 60 may be measured
using a different field transducer.
[0041] A device 128 according to a further embodiment of the
invention utilizes a clip or fastener 138 in the form of a flexible
band generally similar to the bands used as cable ties in the
electrical industry. For example, band 138 may be similar to the
cable ties sold under the registered trademark TY-RAP by the Thomas
& Betts Corporation of Memphis, Tenn., U.S.A. The band
incorporates a head 140 with a hole 142. A locking barb 144 is
disposed in head 140. The free end 146 of the band may be inserted
through the hole and pulled past barb 144, whereupon the barb locks
the free end in place and prevents its retraction out of the hole.
This band may serve to lock the body 132 of the device to the
instrument or probe. Once the band is tightened around the probe or
instrument, it is difficult or impossible to remove or move the
device from the tool and free the band for engagement with another
instrument. A relatively weak, frangible section 148 may be
provided along the length of the band so that the user can remove
the device from an instrument after use. However, because the band
is broken during removal, it is apparent to any subsequent user
that the device has already been used. Even if the band can be slid
off the end of the instrument without breaking the band, it will
still be apparent to the user that the device has been used,
because the band will remain engaged in head 140.
[0042] As depicted in FIGS. 5 and 6, the attachment between the
body 232 holding a field transducer and instrument or tool may
include an adhesive 238. Body 232 is engaged with an intermediate
element or clip 234, which in turn bears a layer of a relatively
strong adhesive. Body 232 may be either removably attached to
intermediate clip 234 or permanently mounted thereto.
[0043] A surgical instrument 310 and disposable device 312 in
accordance with another embodiment of the present invention are
depicted in FIGS. 7 and 8. Instrument 310 may include any surgical
and/or diagnostic instrument as is known in the art, for example, a
scalpel as shown or a forceps discussed above. Device 312 includes
a body 313, which encapsulates the field transducer 315. Body 312
is provided with resilient appendages 314 having externally bent
ends 320. Appendages 314 are preferably spaced from body 313, when
no force is applied to the appendages, so that ends 320 can be
displaced inwardly towards body 313 when appendages 314.
[0044] Device 312 is preferably installed in a cavity 316 formed in
a preselected portion, for example a handle 311, of instrument 310.
Cavity 316 is preferably slightly larger than device 312. As shown
in FIG. 8, cavity 316 preferably includes circumferential
extensions 322 which are adapted to accommodate bent ends 320 of
appendages 314 when device 312 is fully inserted into cavity 316,
as shown in the drawings. Cavity 316 further includes an access
extension 318 which enables access to cavity 316 from a direction
opposite to the direction from which device 312 is installed.
Extension 318 is considerably narrower than body 313 of device 312.
Body 313 is provided with features which closely fit to the
features of handle 311, so that body 313 will be disposed in a
precise, repeatable location on instrument 310, in precise, known
registration with respect to the blade of the instrument. For
example, body 313 may include a projection 319 which fits closely
within access opening 318. Thus, the field transducer 315 will be
located at a known disposition with respect to other features of
the instrument, such as the distal tip or blade. In this
embodiment, the calibration steps discussed above are not required.
However, such steps may be performed to check that device 312 is
properly mounted, or to provide better precision.
[0045] To install device 312 in cavity 316, appendages 314 are
urged against body 313, allowing body 313 to be pushed into cavity
316 together with bent ends 320. For example, cavity 316 may have a
"lead-in" or inclined ramp surfaces surrounding its open side. As
body 313 is pushed into the cavity, ends 320 ride are forced
inwardly toward body 313 by the inclined surfaces. When bent ends
320 reach circumferential extensions 322, appendages 314 spring
back to their original condition and, thus, ends 320 are locked in
extensions 322. It should be appreciated that, once ends 320 are
locked in extensions 322, device 312 cannot be readily uninstalled,
i.e., removed from cavity 316, because appendages 314 cannot be
readily urged against body 313. When ends 320 of appendages 314 are
securely locked in extensions 322, device 312 is firmly mounted in
cavity 316, body 313 is precisely and securely located relative to
instrument 310.
[0046] To remove device 312, a rigid, narrow, member (not shown) is
inserted via access extension 318 and forcefully pushed against the
projection 319 of body 313. Since ends 320 are securely locked by
extensions 322, device 312 cannot be removed with appendages 314
intact. Appendages 314 and ends 320 are designed to break off body
313 when the force exerted on body 313 exceeds a predetermined
threshold. Once appendages 314 are broken off body 313 and device
312 is removed, the device cannot be securely installed as
described above. Thus, once removed, device 312 must be replaced
with a new, unused device 312, thereby preventing re-use of the
device.
[0047] Additionally or alternatively, device 312 may include a
circuit element, e.g. a single conductor, which is adapted to be
physically or electrically damaged during forced removal of device
312 from cavity 316. The electrical connection associated with
device 312 may be arranged to connect such conductor in series with
a testing circuit in the reusable elements of the system as, for
example, in field transmitting and receiving unit 54 (FIG. 3). The
testing circuit may inhibit operation of the system or issue a
warning signal if the circuit element is damaged. Alternatively,
the device may be arranged so that the field transducer itself is
damaged and rendered inoperative during removal of device 312 from
cavity 316. In these arrangements, disposable device 312 cannot be
removed readily from instrument 310 readily without altering the
device in some manner which renders it unusable. It should be
appreciated that absolute assurance against removal without
alteration is not required. All that is required is that the
normal, convenient process for removing disposable device cause the
alteration. For example, in the arrangement of FIGS. 7 and 8, a
skilled person determined to defeat the system may be able to
disengage ends 320 by careful work using a tool inserted between
appendages 314 and the cavity wall. However, the system is still
effective to prevent reuse as the vast majority of users will use
the normal removal process.
[0048] The physical configuration of the device can be altered to
allow reuse of device 312. For example, ends 320 may be omitted or
may be shaped to allow disengagement without breakage. Device 312
may include a usage monitoring element 317, e.g. an electronic key,
as described, for example, in commonly assigned U.S. Provisional
Patent Application 60/011723, filed Feb. 15, 1996, in commonly
assigned U.S. Provisional Patent Application 60/017635, filed May
17, 1996, and in U.S. Pat. No. 5,383,874, the disclosures of which
are incorporated herein by reference. Device 317 may include a
non-volatile memory or other electronic circuit element bearing
information relating to the usage of device 312. Element 317 is
also connected to the reusable components of the system by the same
electrical connector which connects field transducer 315 to the
system. The reusable system may increment a count maintained by
circuit element 317 each time device 312 is connected, so that the
circuit element maintains a count of the number of times device 312
has been used. Alternatively or additionally, the reusable system
may increment a count stored in element 317 periodically while the
device is connected, so that element 317 maintains a record of
total usage time. The reusable system may be arranged to inhibit
use when the usage count exceeds a specified value. Element 317 may
store other information specific to device 312, such as a serial
number and/or lot number identifying the device, calibration data
and the like.
[0049] Device 312 also may be arranged to interact with the
instrument in other ways, so that the device "reads" information
from the instrument pertinent to operation of the system. For
example, where the same device may be engaged with a plurality of
different instruments, the device may read identifying information
on the instrument and convey that information to the position
sensing system. For example, device 312 may be equipped with
switches or exposed contacts which engage corresponding elements of
the device; different types of devices, or different individual
devices, may be equipped with devices to trip these different
switches or connect to different exposed contacts, thereby
providing an electrical code indicative of the device. Other
conventional optical, mechanical or electrical code-reading devices
can be used. The device information can indicate a particular
device shape (for a rigid device) or can convey information
defining the degree of rigidity of the device, the distance from a
predefined transducer mounting location to the tip of the device,
or other information about characteristics of the device which may
influence the precision of the system. For example, in a system
using magnetic fields, the device information may specify a
particular device as bearing magnetic material and thus indicate to
the system that the position-determining accuracy of the system
will be lower than normal.
[0050] The particular physical designs of mating elements are
merely exemplary. In the embodiments discussed above, the
connection between the device incorporating the first field
transducer (the device mounted on the instrument) and the rest of
the position detecting system is made through a hard-wired
connection with a plug. Such a hard-wired connection can be
replaced by a radio, infrared or other wireless telemetry link, in
which case the device desirably includes an independent power
supply such as a battery. Telemetry avoids the physical encumbrance
of loose wires trailing from the instrument. Alternatively, if
wires are used, they can be secured to the instrument, as by tape,
clips or adhesive. Numerous other combinations of features are
known in the art of disposable medical instrument design for
locking mating parts together. Features such as snaps, latches,
bayonet locks, screw threads and the like can be employed. In the
embodiment of FIGS. 7 and 8, the resilient elements are formed on
the body of the disposable device. However, the reverse
arrangement, where the handle or other part of the reusable device,
incorporates resilient parts, can also be utilized. A handle as
illustrated in FIGS. 7 and 8 may be configured so that the handle
can be releasably associated with other portions of the instrument,
such as an elongated rod or tube for insertion into the body.
[0051] In some preferred embodiments of the present invention, the
disposable device includes a field transducer or position sensor
adapted for multiple, yet controlled, use. In these preferred
embodiments of the invention, the instrument and the position
sensor are sterilized separately and, after sterilization, the
position sensor is removably mounted on the mounting site of the
instrument. After the instrument has been used, the position marker
is removed without being altered. Such multiple-use position
sensors may be used in a system in which each position sensor is
assigned to a specified surgical/diagnostic instrument or a
specified type of surgical/diagnostic instrument. In some preferred
embodiments, the position sensor may includes identifying circuitry
as discussed above, and the system may be arranged to allow
operation of each position sensor only in conjunction with the
specified instrument or type of instrument. Additionally or
alternatively, the position sensor mounting on the instrument may
have a shape unique to the specified instrument or type of
instrument. Each position sensor is uniquely shaped to be mountable
only on the instrument to which the marker is assigned.
[0052] An instrument in accordance with another embodiment of the
invention includes an elongated probe body 400 (FIG. 9) having a
relatively rigid proximal portion and a formable region 404.
Formable region 404 is arranged so that the user can bend it to the
desired shape and so that after bending, the formable region will
substantially retain its new shape. In the embodiment illustrated,
the formable region includes a corrugated polymeric covering and an
internal reinforcing wire which can be plastically deformed. Wire
406 may be formed from a relatively soft metal having a "dead-bend"
or non-resilient characteristic. Merely by way of example, annealed
aluminum and soft alloys such as common solders and other
lead-based alloys, silver solders and others have outstanding
dead-bend characteristics. Metals having some resilience also can
be employed. Instrument 400 further includes a field transducer or
position sensor 408 mounted on proximal portion 402. In operation,
the physician can deform formable region 404 to a shape required to
accommodate anatomical structures of a particular patient,
typically by reviewing images of the anatomical structures such as
CT, X-ray or MRI images. This process brings the distal tip 410 of
the instrument body to an arbitrary, user-selected location 410'
with respect to position sensor or field transducer 408. The
instrument is then calibrated as described above, to establish the
vector between transducer 408 and tip location 410'. Provided that
the configuration of the formable section does not change during
use, the system can accurately track the location of tip 410.
insert C Thus, the formable section should be rigid enough to
retain its shape after forming. Stated another way, the forces
applied to bend the formable section deliberately are substantially
greater than the forces encountered by the formable section during
use in the patient's body.
[0053] The calibration process can be repeated for numerous points
along the bent probe as, for example, at each of points 411, 413,
415, and 417, in addition to the tip 410'. For example, each of
these features or points along the bent probe can be engaged with
the object of known location (60, FIG. 3) while a calibration
disposition of first field transducer 408 is acquired. Thus, the
system acquires a vector or transform relating the position of each
of the additional points to the position and orientation of field
transducer 408. In use, the system displays representations of each
of these additional points, as well as a representation of tip
410', on the display 58 (FIG. 3). The system thus displays a
multi-point curve representing the shape of the probe during use.
Where a large number of features are calibrated in this manner, the
system can display an image of the arbitrarily-shaped probe
approximating a silhouette of the probe. This image can be
superposed on the previously-acquired patient image, as discussed
above with reference to a single point representation. A similar
approach can be used to obtain a silhouette of a non-formable tool
such as a single arm of the forceps of FIG. 2. However, if the
geometry of a non-formable tool with reference is known in advance,
as from stored data defining the geometry of the tool, the vectors
for all points on the tool can be deduced from the vector for a
single point established as above. For example, the position vector
from first field transducer 30 to any point along forceps arm 48
can be deduced from the vector Vp from the first field transducer
30 to tip 62, discussed above, and known data defining the shape of
arm 48. The computer system may store a library of tool shapes and
select a tool shape for use in such computation based on input from
the user. In a variant of the probe depicted in FIG. 9, the
position sensor is disposed at tip 410, so that calibration is not
required, and deformation of the formable section during use will
not affect positioning accuracy. However, this requires that the
probe be of adequate diameter to accommodate the position
sensor.
[0054] Probes having formable sections can be used in a wide
variety of procedures, but are particularly useful in procedures
involving the brain. When the probe is in a generally J-shaped
configuration as shown in broken lines in FIG. 9, it can inserted
between the brain and the dura through a craniotomy to reach around
the hippocampus. A further useful neurosurgical procedure in
accordance with the present invention utilizes a probe having a
long, flaccid flexible region such as a thin rubber tube, and a
position sensor at the distal end of such flexible region. For
example, the flexible region may be a tube of a soft silicone
rubber or other soft polymer of about 2 mm diameter of less. The
flexible region is threaded between the brain and dura of a
mammalian subject such as a human patient. If the probe encounters
an obstacle, the physician can continue to urge the probe in the
distal or threading direction. Even if the soft, flexible region
kinks, it will not damage the brain. This procedure allows the
physician to probe obstacles with confidence. It is particularly
useful during operations to install cortical electrode strips
during epilepsy mapping.
[0055] A probe in accordance with a further embodiment of the
invention includes a rigid proximal portion 502 and formable
portion 504 as discussed above with reference to FIG. 9, and
further includes a flexible region 520 at the distal end of the
probe. Region 520 is considerably more flexible than formable
portion 504. For example, region 520 may include a soft, supple
polymeric tube, such as a thin tube of a soft silicone rubber.
Region 520 optionally may include a spring 522 to provide
resilience. A steering mechanism is provided which allows the user
to control the shape of flexible region 520. In the particular
arrangement illustrated, the steeling mechanism includes an
actuator button 524 movably mounted to the proximal region 502 and
a cable 526 extending within the probe from a fixed end 528
adjacent button 524 to a point in flexible region 520 adjacent the
distal end 510 of the probe. By pressing button 524 inwardly, the
user can pull on cable 526 and thus bend flexible region 520 as
depicted in broken lines at 520'. A spring 530 biases button 524
away from cable 526, so that the flexible region tends to return to
the position illustrated in solid lines in FIG. 10. Other devices
are known in the art for selectively bending the distal end of a
probe using control inputs supplied at the proximal end, and those
devices can be used in the device of FIG. 10. Formable region 504
can be manually bent as shown in broken lines at 504.' A field
transducer 508 is mounted in flexible region 520 and provided with
leads extending to the proximal end of the probe for connection to
the position monitoring system. Probes as discussed above with
reference to FIG. 10 can be used to control the configuration of a
flexible endoscope. When the probe is inserted into the working
channel of the endoscope, the distal end of the endoscope will bend
along with the distal end of the probe. In a variant of the probe
depicted in FIG. 10, formable region 504 can be omitted, and the
flexible region 520 may be joined directly to the distal end of a
rigid proximal portion. Such a probe can be used with a rigid
endoscope; the rigid section of the probe is positioned within the
rigid endoscope, whereas the flexible region protrudes from the
distal tip of the endoscope.
[0056] As shown in FIG. 11, a device in accordance with another
embodiment of the invention includes a body 600 housing a field
transducer or position sensor 602. Body 600 has a lumen 604 with a
pair of resilient O-rings 606 mounted therein. In use, the body can
be mounted on an elongated instrument such as a biopsy needle by
advancing the needle through lumen 604, thereby frictionally
engaging the needle with O-rings 606. A unit of this type typically
is provided in sterile condition, so that it does not contaminate
the biopsy needle or other instrument. For example, the device may
be provided in a sterile overwrap and the needle may be thrust
through the sterile overwrap into lumen 604. The entire body 600,
including O-rings 606, can be provided as a single integral elastic
unit. In a further variant, the elastic component can be replaced
by a shrinkable tube so that the disposable device, with the
position sensor or field transducer thereon, can be attached to a
medical instrument by shrinking the tube around a part of the
instrument. Such a shrinkable tube may be a heat-shrinkable
shrinkable tube of the type commonly used in the electrical
industry, or may be shrinkable by chemical action. Where the
disposable device is to be mounted on a portion of the instrument
which will be advanced into the patient during use, such as on or
adjacent the distal end of a needle, the field transducer or
position sensor desirably is a compact unit such as a
lithographically-formed coil or set of coils. A preferred
lithographic coil has a size of 0.8 mm wide by 3 mm long, a
thickness of 0.3 mm and includes a rectangular coil having the
following characteristics: a line width of 6 .mu., a line spacing
of 6 .mu. and a line thickness of 2 .mu.. The number of windings is
preferably the maximum number which fit in the coil. A thin (0.3
mm) ferrite layer may be provided adjacent the coil to increase its
sensitivity. The coil may be formed on a silicon substrate, or
preferably, on a flexible polyimide substrate which can conform to
the needle. Preferably, more than one layer of conduction lines is
provided. The use of sensor-equipped biopsy needles, and other
probes, are described in greater detail in co-pending, commonly
assigned PCT Application entitled LOCATABLE BIOPSY NEEDLE, filed of
even date herewith, the disclosure of which is hereby incorporated
by reference herein.
[0057] As depicted in FIG. 12, a jig 610 can be used to position a
disposable device having a field transducer or position sensor
thereon in a predetermined disposition relative to a feature of an
instrument or probe. Thus, jig 610 has a surface 612 for engaging
the bevel 614 of a biopsy needle 613, and surfaces 616 and 618 for
engaging surfaces of a disposable device 600, such as surfaces of
the disposable device body 602. The instrument or biopsy needle 613
is positioned temporarily in the jig, with the bevel 614 engaging
surface 612 of the jig, and the disposable device is brought into
engagement with surfaces 616 and 618, thereby positioning body 602
at a predetermined position and orientation with respect to bevel
614. Such jig-based positioning can be used as an alternative to
the calibration process discussed above. In a further alternative,
the body 600 of the disposable device carrying the field transducer
or position sensor is brought to a known position relative to the
feature to be tracked, such as bevel 614, by abutting the
disposable device body 600 against another feature of the
instrument, such as the hub 618 of the needle, which is located at
a known position relative to feature 614. A tool 620 of known
dimensions may be interposed between the disposable device body and
feature 618. Other jigs may be used for instruments of different
configurations.
[0058] It will be appreciated by persons skilled in the art that
the present invention is not limited to what has been thus far
described. Rather, the scope of the present invention is limited
only by the claims.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0059] The present application claims benefit of United States
Provisional Applications No. 60/011,743, filed Feb. 15, 1996, US
60/011,723 Filed Feb. 15, 1996 US 60/017,635 Filed May 17, 1996,
the disclosures of which are hereby incorporated by reference
herein.
[0060] The following PCT applications, each of which names
Biosense, Inc as an applicant are also incorporated by reference
herein: Catheter Based Surgery filed on or about Feb. 14, 1997 in
the Israeli Receiving Office; Intrabody Energy Focusing filed on or
about Feb. 14, 1997 in the Israeli Receiving Office; Locatable
Biopsy Needle, filed on or about Feb. 14, 1997 in the Israeli
Receiving Office; Catheter Calibration and Usage Monitoring filed
on or about Feb. 14, 1997 in the Israeli Receiving Office; Precise
Position Determination of Endoscopes filed on or about Feb. 14,
1997 in the Israeli Receiving Office; Medical Procedures and
Apparatus Using Intrabody Probes filed Feb. 14, 1997 in the United
States Receiving Office; Catheter with Lumen filed Feb. 14, 1997 in
the United States Receiving Office; Movable Transmit or Receive
Coils for Location System filed Feb. 14, 1997 in the United States
Receiving Office; and Independently Positionable Transducers for
Location System filed Feb. 14, 1997 in the United States Receiving
Office. The PCT application entitled, Multi-Element Energy Focusing
filed Feb. 14, 1996 in the Israeli Receiving Office and naming
Victor Spivak as applicant is also incorporated by reference
herein.
INDUSTRIAL APPLICABILITY
[0061] The invention can be used in medical and related
procedures.
1APPENDIX acquire position p.sub.o: acquire position p.sub.1 and
orientation o.sub.1; call function attach_find Vec to get v.sub.p;
while using tool { acquire probe position p.sub.p and orientation
o.sub.p; call function attach_convertPos; 3) Code for function
attach_findVec, attach_convertPos The following is the C code of
the implementation of the tool calibration algorithm: Function
attach_findVec is to find vector v.sub.p by using v.sub.p = o.sub.1
(p.sub.o - p.sub.1) Function attach_convertPos is to use v.sub.p to
find tool tip position by using p.sub.1 = p.sub.p +
o.sub.p.sup.-1v.sub.p void attach_findVec (pos_in_1, pos_ref,
on_in_1. pos_vec) double pos_in_1[3]; /* probe location reading
when placing tip of the attached tool at the absolute location
reference point in mapping space */ double pos_ref[3]; /* probe
location reading when placing tip of the probe at the absolute
location reference point in mapping space */ double ori_in_1[3][3];
/* probe orientation matrix when placing tip of the attached tool
at the absolute location reference point in mapping space, i.e.,
the orientation associated with pos_in_1 [3]; the matrix should be
normalized and orthogonal */ double pos_vec[3]; /* resulted
constant vector of tool calibration that is going to be used for
calculating tool tip position */ ( int i; double difference[3];
for(i = 0; i < 3; i--) difference[i] = pos_ref[i] = pos_in_1[i];
pos_vec[0] = ori_in_1[0] [0; = difference[0] = ori_in_1[0][1] =
difference[1] = ori_in_1[0][2] = difference[2] = pos vec[1] =
ori_in_1[1][0] = difference[0] = ori_in_1[1][1] = difference[1]=
ori_in_1[1][2] = difference[2]; pos_vec[2] = ori_in_1[2][0] =
difference[0] = ori_in_1[2][1] = difference[1] = ori_in_1[2][2] =
difference[2]; void attach_convertPos (pos_in, pos_out, ori_vec,
pos_vec) double pos_in[3]; /* the location vector reading of the
probe attached to the tool */ double pos_out[3]; /* the converted
location which reflects the tool tip position after returning of
this routine */ double ori_vec[3][3]; /* the orientation matrix
reading of the probe attached to the tool; the matrix should be
normalized and orthogonal */ double pos_vec[3]; /* the constant
vector from tool calibration procedure, i.e., the resulted vector
from routine attach_findVec */ int i,j; double ori_vec_rev [3][3];
/* find the reverse of the matrix ori_vec */ for(i = 0; i < 3;
i--) for(j = 0; j < 3; j--)( ori_vec_rev[i][j] = ori_vec[j][i];
) pos_out[0] = pos_in[0] = ori_vec_rev[0][0]= pos_vec[0] =
ori_vec_rev[0][1] = pos_vec[1] =ori_vec_rev[0][2] = pos_vec[2];
pos_out[1] = pos_in[1] = ori_vec_rev[1][0] = pos_vec[0] =
ori_vec_rev[1][1] = pos_vec[1] = ori_vec_rev[1][2] = pos_vec[2];
pos_out[2] = pos_in[2] = ori_vec_rev[2][0] = pos_vec[0] =
ori_vec_rev[2][1] = pos_vec[1]
* * * * *