U.S. patent application number 14/159104 was filed with the patent office on 2014-05-15 for trajectory storage apparatus and method for surgical navigation systems.
This patent application is currently assigned to Medtronic Navigation, Inc.. The applicant listed for this patent is Medtronic Navigation, Inc.. Invention is credited to Thomas A. Carls, Kevin T. Foley, Anthony J. Melkent, David A. Simon.
Application Number | 20140135796 14/159104 |
Document ID | / |
Family ID | 24174865 |
Filed Date | 2014-05-15 |
United States Patent
Application |
20140135796 |
Kind Code |
A1 |
Simon; David A. ; et
al. |
May 15, 2014 |
Trajectory Storage Apparatus and Method for Surgical Navigation
Systems
Abstract
A method and apparatus for determining, calculating, and/or
viewing a trajectory. The trajectory can be displayed on a display
relative to image data of a patient. A user can use the system to
determine relationships between two or more trajectories that have
been determined. The relationships can be within two dimensional,
three-dimensional, or four dimensional space. The relationships can
include distance, angle, etc. The relationships can also be
determined between real time trajectories and stored trajectories,
or combinations thereof.
Inventors: |
Simon; David A.; (Boulder,
CO) ; Foley; Kevin T.; (Germantown, TN) ;
Carls; Thomas A.; (Memphis, TN) ; Melkent; Anthony
J.; (Germantown, TN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Medtronic Navigation, Inc. |
Louisville |
CO |
US |
|
|
Assignee: |
Medtronic Navigation, Inc.
Louisville
CO
|
Family ID: |
24174865 |
Appl. No.: |
14/159104 |
Filed: |
January 20, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12966407 |
Dec 13, 2010 |
8634897 |
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14159104 |
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11128808 |
May 13, 2005 |
7853305 |
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12966407 |
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10177739 |
Jun 21, 2002 |
6920347 |
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11128808 |
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09545092 |
Apr 7, 2000 |
6535756 |
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10177739 |
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Current U.S.
Class: |
606/130 |
Current CPC
Class: |
A61B 2034/104 20160201;
A61B 2090/378 20160201; A61B 34/25 20160201; A61B 34/10 20160201;
A61B 2090/376 20160201; A61B 6/12 20130101; A61B 2034/2072
20160201; A61B 2017/00725 20130101; A61B 34/20 20160201; A61B
2034/107 20160201; A61B 6/4441 20130101; A61B 90/36 20160201; A61B
2090/061 20160201 |
Class at
Publication: |
606/130 |
International
Class: |
A61B 19/00 20060101
A61B019/00 |
Claims
1. A system, comprising: a tracking device having a trackable
portion; an instrument having a first portion extending from the
tracking device to be engaged by a user; a computer to integrate a
tracked trajectory of the instrument and an image; and a display
device to display an icon representing the tracked trajectory
overlaid on the image.
2. The system of claim 1, wherein the image is a pre-acquired
image.
3. The system of claim 1, further comprising: a navigation system
having a detector to detect the tracking device.
4. The system of claim 3, wherein the navigation system includes at
least one of an acoustic tracking system, an optical tracking
system, a LED/reflectors tracking system, or an electromagnetic
tracking system.
5. The system of claim 1, further comprising: a memory system to
store at least one trajectory of the instrument; wherein the
computer is able to determine an angle between a real-time
trajectory and the at least one stored trajectory.
6. A method of illustrating a first trajectory and a second
trajectory of an instrument, comprising: obtaining image data from
an imaging system; tracking an instrument with a tracking system;
displaying the image data; displaying a first trajectory of the
instrument; and displaying a second trajectory of the
instrument.
7. The method of claim 6, further comprising: obtaining the first
trajectory at a first instrument position; and obtaining the second
trajectory at a second instrument position that is different from
the first instrument position.
8. The method of claim 7, further comprising: storing the first
trajectory in a memory.
9. The method of claim 8, further comprising: measuring an angle
between the second trajectory and the first trajectory.
10. The method of claim 9, wherein the second trajectory is a
real-time trajectory.
11. A system for storing at least one trajectory, comprising: a
tracking system having a detector; a tracking device having a
tracking marker to be detected by the detector; an instrument
having a first member extending from the tracking device; a memory
unit having stored therein instructions; a central processing unit
in communication with the memory unit and to execute the
instructions; and a display to display a first trajectory of the
instrument and a second trajectory of the instrument; wherein the
central processing unit is operable to execute the instructions to
compute geometric measurements regarding the first trajectory
relative to the second trajectory.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/966,407 filed on Dec. 13, 2010, which is a
continuation of U.S. patent application Ser. No. 11/128,808 filed
on May 13, 2005, now U.S. Pat. No. 7,853,305 issued on Dec. 14,
2010, which is a continuation of U.S. patent application Ser. No.
10/177,739 filed on Jun. 21, 2002, now U.S. Pat. No. 6,920,347
issued on Jul. 19, 2005, which is a Continuation of U.S. patent
application Ser. No. 09/545,092 filed on Apr. 7, 2000, now U.S.
Pat. No. 6,535,756 issued on Mar. 18, 2003. The entire disclosures
of each of the above applications are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of Invention
[0003] The present invention is directed generally to image-guided
medical procedures, and more particularly, to systems and methods
for the storage and geometric measurement of instrument
trajectories used in image-based surgical guided navigation
systems.
[0004] 2. Description of the Related Art
[0005] Image based surgical techniques have been used with success
in aiding physicians for performing a wide variety of delicate
surgical procedures. These procedures are typically used when the
visualization of a surgical tool could be obscured by a patient's
anatomy, or when the surgical tool is visible but the patient's
anatomy may be difficult to visualize in three dimensions. Such
procedures include, for example, spinal implant placement, the
alignment of broken bone fragments, and the fixation of bone
fractures. Prior art techniques to accurately position a surgical
instrument have included the use of x-ray images to localize its
position. Through the repeated acquisition of x-ray images during
the procedure, real-time placement of the instrument relative to
the patient's anatomy can be displayed. More recently, virtual
fluoroscopically-based surgical navigation systems have been
employed to track an instrument trajectory and superimpose its
representation onto pre-acquired images without requiring x-rays to
be repeatedly taken during the actual surgical procedure.
[0006] In many situations, a surgeon would like to create a static
visual reference using the real-time and generally instantaneous
instrument trajectory displayed by the surgical navigation system
as the instrument progresses in the general direction of a
selected, desired path. For example, some procedures require the
serial placement of several implants which must be placed in a
precise relative geometry. Currently, the surgeon must reacquire a
new set of images after each implant is placed to properly
determine the trajectory of the subsequent implant. This can be a
time consuming process which increases the amount of radiation
exposure to the patient and operating room personnel.
[0007] Other situations may require the surgeon to make accurate
geometric measurements of a patient's anatomy. For example, some
surgical procedures require the precise removal of a specific
amount of bone taken in the shape of a wedge. In order to determine
this amount, an angular measurement of the bone at the surgical
site would assist in this procedure. Another example would be in
allowing the surgeon to make distance measurement between bone
implant sites to ensure proper implant placement. In light of the
foregoing, there is a need for the ability to save surgical
instrument trajectories and have the capability to perform
measurements thereon.
SUMMARY OF THE INVENTION
[0008] The present invention is directed generally to image guided
medical procedures, and, particularly, to medical procedures
involving the tracking of surgical instruments. More specifically,
the present invention is directed to a device and method for
storing instrument trajectories.
[0009] To achieve these objects and other advantages and in
accordance with the purposes of the invention, as embodied and
broadly described herein, the invention is directed to an apparatus
and method for the storage of trajectories and measurements which
may be performed thereon for use in conjunction with image-guided
surgical navigation systems.
[0010] In one aspect of the invention, an instrument trajectory is
tracked in real-time by a surgical navigation system. An icon
representing this real-time trajectory is overlaid on one or more
pre-acquired images of the patient. At the surgeon's command, the
navigation system can store the trajectory of the instrument and,
if desired, create a static icon representing the saved trajectory
for display on each pre-acquired image. The icon representing the
stored trajectory is simultaneously displayed with the real-time
trajectory's icon so the surgeon may visually compare them. The
surgeon has the option of saving additional trajectories by
reissuing the storage command.
[0011] In another aspect of the invention, the surgeon may measure
angles between pairs of any two trajectories. The angles are
computed in the plane of the image, and are, therefore, computed
separately for each image displayed. One option is to compute one
or more angles between the real-time trajectory and saved
trajectories. These angles are preferably computed and displayed on
each pre-acquired image. As the real-time trajectory changes, the
displayed values are preferably updated in each image in real-time.
Another option is to measure one or more angles between pairs of
any two stored trajectories. As with the prior option, these angles
could be computed and displayed separately for each image.
[0012] In yet another aspect of the invention, three dimensional
distances between pairs of points defined by one or more sets of
two trajectories can be computed and displayed. One option is to
measure the distance between the real-time trajectory and one or
more saved trajectories. These measurements would be computed in
real-time and updated on the display as the real-time trajectory
varies. Another option would be computing and displaying distances
between pairs of points defined by one or more sets of two
user-selected stored trajectories. For either of these two options,
the defined points may be represented by the tip of each trajectory
as computed by the system, or may be defined by a user-selected
extension projected from the trajectory's tip.
[0013] Preferably, the invention can overcome the problems of the
prior art by providing the surgeon with the visual reference and
measurement information required for some surgical procedures.
[0014] Both the foregoing general description and the following
detailed description are exemplary, and are intended to provide
further explanation of the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate an embodiment
of the invention and together with the description, serve to
explain the principles of the invention.
[0016] FIG. 1 is a simplified block diagram of an embodiment of a
system for the storage and measurement of instrument trajectories
in accordance with the present invention.
[0017] FIG. 2 is a simplified side view of an embodiment of a
system for use in instrument trajectory storage and measurement in
accordance with the present invention.
[0018] FIG. 3 is a block diagram of a process used to select,
store, and compute geometric properties of trajectories in
accordance with the present invention.
[0019] FIG. 4 is an exemplary diagram of a display in accordance
with an embodiment of the invention showing several stored
instrument trajectories and the real-time trajectory superimposed
on two images of a patient's anatomy.
[0020] FIG. 5 is a simplified block diagram of an exemplary
computer system used in the surgical navigation system in
accordance with one embodiment of the invention.
[0021] FIG. 6 is a block diagram of a process used compute the
angle between two trajectories in accordance with the present
invention.
[0022] FIG. 7 is a is a block diagram of a process used compute the
distance between the tips of two trajectories in accordance with
the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0023] Reference will now be made in detail to the present
preferred embodiments of the invention, examples of which are
illustrated in the accompanying drawings. Wherever possible, the
same reference numbers will be used throughout the drawings to
refer to the same or like parts.
[0024] With reference to FIG. 1, there is shown schematically an
apparatus in accordance with the present invention for the storage
of instrument trajectories. Image-based surgical navigation system
100 enables a surgeon to generate and display on monitor 115 the
trajectory of instrument 125, which is preferably a surgical
instrument configured in any known manner. Data representing one or
more pre-acquired images 105 is fed to navigation computer 110.
Navigation computer 110 tracks the position of instrument 125 in
real-time utilizing detector 120. Computer 110 then registers and
displays the trajectory of instrument 125 with images 105 in
real-time. An icon representing the trajectory of instrument 125 is
superimposed on the pre-acquired images 105 and shown on monitor
115. At the surgeon's command, the real-time trajectory of
instrument 125 can be stored in computer 110. This command also
creates a new static icon representing the trajectory of the
instrument on display 115 at the time the surgeon's command was
issued. The surgeon has the option of issuing additional commands,
each one storing an real-time trajectory and creating a new static
icon for display by default. The surgeon can override this default
and choose to not display any static icon. The surgeon also has the
option to perform a number of geometric measurements using the
real-time and stored instrument trajectories. While the present
invention described in more detail below is exemplified by a
fluoroscopic-based system, it is not limited to the described
embodiment and could be practiced with many different types of
navigation systems.
[0025] FIG. 2 illustrates fluoroscopic image-based surgical
navigation system 200 according to the preferred embodiment of the
present invention. System 200, described below in sufficient detail
to allow an understanding and appreciation of the present
invention, is explained in greater detail in U.S. patent
application Ser. No. 09/274,972 of David A. Simon et al., entitled
"Navigation Guidance via Computer Assisted Fluoroscopic Imaging,"
filed on Mar. 23, 1999, now U.S. Pat. No. 6,470,207 issued on Oct.
22, 2002, the entire disclosure of which is hereby incorporated by
reference. However, it should be understood that the invention is
not confined to use with this particular image guided surgical
system.
[0026] Further referring to FIG. 2, an image-based surgical
navigation system 200 for acquiring and displaying x-ray images
appropriate for a given surgical procedure is shown. Pre-acquired
images of patient 202 are collected when a patient, lying on
platform 205, is placed within C-arm 212 of imaging device 210. The
term "pre-acquired," as used herein, does not imply any specified
time sequence. Preferably, however, the images are taken at some
time prior to when surgical navigation is performed. Usually,
images are taken from two substantially orthogonal directions, such
as anterior-posterior (A-P) and lateral, of the anatomy of
interest. Imaging system 210 further includes x-ray source 214 and
x-ray receiving section 216 mounted on opposite sides of C-arm 212.
Receiving section 216 includes target tracking markers 222. System
210 further includes C-arm control computer 226 which allows a
physician to control the operation of imaging device 210. One
implementation of imaging device 210 is the Model 9600 C-arm
fluoroscope from OEC Medical Systems, Inc. of Salt Lake City, Utah,
although tracking markers 222 are typically not included in the
Model 9600 C-arm fluoroscope and may have to be added, however, the
9600 is otherwise structurally similar to imaging device 210. It is
to be understood, however, that the invention is not confined to
the use of this type of imaging device.
[0027] Fluoroscopic images taken by imaging system 210 are
transmitted to computer 226 where they may be forwarded to surgical
navigation computer 110. Computer 110 provides the ability to
display the received images via monitor 115. Other devices, for
example, such as heads up displays, may also be used to display the
images.
[0028] Further referring to FIG. 2, image-based surgical navigation
system 100 generally performs the real-time tracking of instrument
125, and, in the preferred embodiment, also tracks the position of
receiver section 216 and reference frame 235. Detector 120 senses
the presence of tracking markers on each object to be tracked.
Detector 120 is coupled to computer 110 which is programmed with
software modules that analyze the signals transmitted by detector
120 to determine the position of each object in detector space. The
manner in which the detector localizes the object is known in the
art, and is discussed, for example, in PCT Application No.
PCT/US95/12894 (Publication No. WO 96/11624) to Bucholz, the entire
disclosure of which is incorporated by reference. Any type of
tracking system known in the art can be used, including, by way of
example only, acoustic, optical, LED/reflectors, electromagnetic,
and/or other similar devices.
[0029] In general, instrument 125 is tracked by surgical
navigation-system 100 using attached tracking markers 230 in order
for its three-dimensional position to be determined in detector
space. Computer 110 integrates this information with the
pre-acquired images of patient 202 to produce a display which
assists surgeon 270 when performing surgical procedures. An iconic
representation of the trajectory of instrument 125 is
simultaneously overlaid on the pre-acquired images of patient 202
and displayed on monitor 115. In this manner, surgeon 270 is able
to see the trajectory of the instrument relative to the patient's
anatomy in real-time.
[0030] Further referring to FIG. 2, the system according to the
invention preferably has the ability to save the dynamic real-time
trajectory of instrument 125. By issuing a command using
foot-switch 280, for example, computer 110 receives a signal to
store the real-time trajectory of the instrument in the memory of
computer 110. This "storage command" also instructs computer 110 to
generate a new static icon representing the saved trajectory of the
instrument, essentially "freezing" the icon at the point when
foot-switch 280 was closed. The static icon, along with the icon
representing the real-time trajectory of the instrument, can be
simultaneously superimposed over the pre-acquired image. If
multiple images are being displayed, both static and real-time
icons can be superimposed on all of the displayed images. Other
means of issuing the storage command, such as, for example, through
a graphical user interface, may also be used. The surgeon also has
the option of storing multiple instrument trajectories. Each time a
desired storage command is issued, the real-time trajectory of the
instrument is stored in computer 110 and a new static icon
representing the stored trajectory is displayed on the pre-acquired
image, or if more than one image is being displayed, on all the
pre-acquired images. These storage trajectory features are
described in more detail below.
[0031] The system according to the invention preferably has the
additional capability to measure angles between the real-time
trajectory and one or more of the stored trajectories. These
"dynamic angles" are measured in the image plane and are updated in
real-time as the real-time trajectory varies. The computed values
may then be displayed simultaneously with the pre-acquired image.
If more than one pre-acquired image is being displayed, the angles
for each image are preferably computed and displayed separately
since they will be different for each image plane. Preferably, the
system is configured to compute and display one or more angles
between pairs of stored trajectories selected by surgeon 270. As
with the dynamic angle measurements, the angles between the stored
trajectories are computed in the image plane. They are preferably
calculated and displayed separately for each displayed image. These
angle calculation features will be described in more detail
below.
[0032] Furthermore, the system preferably also has the ability to
compute three-dimensional distances between pairs of points defined
by the real-time trajectory and one or more stored trajectories
selected by surgeon 270. These "dynamic distance" values are
displayed with the image and vary as the instruments trajectory
changes. The system also preferably has the ability to measure
distances between pairs of points defined by one or more pairs of
stored trajectories and to display this information with the image.
For either distance measuring option, the point pairs above may be
defined by the tips of the instrument trajectories, or they may be
defined by extending the tips by a user-specified amount. Each of
these options will be discussed in more detail below. Unlike the
angle calculation, the three-dimensional distance is not a planar
measurement, as such it will not vary among different images. The
distance parameters may be displayed separately for each image, or,
as in the preferred embodiment, may only be displayed in one
location.
[0033] Image-based surgical navigation system 100 utilized in the
preferred embodiment of the present invention may be the same as
that used in the FluoroNav.TM. system, which utilizes the
StealthStation.RTM.. Treatment Guidance Platform, both of which are
available from Medtronic Sofamor Danek, Inc.
[0034] FIG. 3 shows flowchart 300 illustrating the preferred
embodiment for storing instrument trajectories and computing
geometric quantities. System 100 tracks instrument 125 by detecting
tracking markers 230 with detector 120. Positions are computed in
real-time in detector space by computer 110 and converted to frame
space, which is a coordinate system associated with reference frame
235. The conversions used may be ones which are well known to those
skilled in the art. The instrument trajectory is preferably tracked
using two points, the tip and the hind, on instrument 125 which are
obtained using known offsets from tracking markers 230 (step 305).
The computation of the tip and hind positions is described in more
detail below. An icon representing the real-time trajectory of
instrument 125 may be superimposed on one or more pre-acquired
images 105 (step 310). The real-time instrument tracking proceeds
until the computer receives a storage command from the surgeon. In
the preferred embodiment, this command is given by a signal
initiated by actuation of foot-switch 280. The surgeon may also use
a graphical user interface, which is described in more detail
below, running on computer 110 to issue a storage command (step
315). Upon receipt of the command, computer 110 stores the
real-time trajectory of instrument 125 by placing the positions of
the instrument's tip and hind into memory (step 320). Computer 110
then displays an icon representing the stored trajectory which may
be superimposed, along with the real-time trajectory, on the
pre-acquired image. If more than one pre-acquired image is being
displayed, both the stored and real-time icons can be superimposed
on all pre-acquired images (step 325).
[0035] After one or more trajectories are saved, surgeon 270 has
the option of computing several geometric measurements through
exercising the appropriate commands on the computer's 110 graphic
interface (step 330). The surgeon will then typically select which
trajectories to perform the measurements upon. Measurements may be
performed between the real-time trajectory and one or more
user-selected stored trajectories. Alternatively, a number of
measurements may also be made between pairs of user-selected stored
trajectories which are chosen through the user interface (step
335). Once the trajectory pairs are chosen, surgeon 270 can select
to have the angles and/or a distance measurements performed (step
340). The distance and angle calculations are described below in
more detail.
[0036] Finally, the values the surgeon chose to measure can be
displayed on monitor 115 simultaneously with the pre-acquired image
and trajectory icons. If the measurement being performed includes
the real-time trajectory, each displayed value can be updated in
real-time as the position of instrument 125 changes. If multiple
pre-acquired images are being displayed, the angles can be
displayed on each desired image. However, in the preferred
embodiment, the distance values will typically be displayed in one
location. (step 345).
[0037] FIG. 4 shows an exemplary display which is consistent with
the preferred embodiment of the invention. Display 400 preferably
includes of three primary default windows, 403a-c. Two fluoroscopic
images, 402 and 405, taken from different orientations of a
patient, are shown in two windows, 403a-b, respectively. Control
and status window 403c provides the surgeon with a set of software
controls to vary the system parameters and control the modes and
functionalities of the FluoroNav.TM. system. Note that image 405 is
partially obscured by dialog box 410.
[0038] Further referring to FIG. 4, image 402 shows seven stored
trajectories, 415a-g, and one real-time trajectory, 417. The hind
points of each stored trajectory are denoted with cross symbols
420a-f. Note the cross symbol of trajectory 415f is not indicative
of a hind point, but of an extension. Extensions will be described
in more detail later. The hind point of real-time trajectory 417 is
indicated by cross 422. Obviously, many other symbols other than a
cross may be used to denote the hind point. Each trajectory,
represented by a directional indicator such as a line, can be
automatically assigned a different color and unique numerical label
to easily identify it. Other types of directional indicators may
also be used, and different shapes, styles, sizes, and textures can
be employed to differentiate among the trajectories. Only labels
425a-d, associated with trajectories 415a, 415d, 415f, and 415g,
respectively, are shown in window 403a. The surgeon has the option
of not showing the label for any trajectory if desired. The surgeon
also has the option of changing the default color or label text for
any trajectory through the controls contained in dialog box 410.
The functionality of dialog box 410 will be described in more
detail below.
[0039] In certain situations, the surgeon may wish to know where
the tip of the instrument would be if it were extended along a path
direction indicated by its current trajectory. When software button
430 in window 403c is toggled on, computer 110 will calculate and
display the icon based upon the previously set extension, as set by
slider bar 435, and the current trajectory of the instrument.
Toggling button 430 again will result in no extension being
displayed. For example, if button 430 were previously activated and
slider 435 is set to 45 mm, selecting button 430 will set the
slider value to 0 mm. Activating it a second time will restore it
to 45 mm. The estimated position of the tip can be calculated by
computer 110 by projecting a fixed length beyond the instrument's
tip in the direction of the line formed by each instrument's tip
and hind. As shown in FIG. 4, an exemplary extension 418 is shown
in a different line style from trajectory icon 415g. This
difference could also be a change in color, type, and/or texture
between extension 418 and current trajectory 415g. Computer 110 may
vary the length of the extension as directed by the surgeon through
manipulating control slider 435 using computer 110's mouse or
keyboard. The extension feature is described in greater detail in
U.S. patent application Ser. No. 09/274,972, now U.S. Pat. No.
6,470,207 issued on Oct. 22, 2002 which has been incorporated by
reference. Although the look-ahead technique described above
projects the graphical representation of the instrument into the
image, there is no requirement that the instrument's graphical
representation be in the space of the image for the extension to be
projected into the image. In other words, for example, the surgeon
may be holding instrument 125 above the patient and outside the
space of the image, so that the representation of the instrument
does not appear in the images. However, it may still be desirable
to project ahead a fixed length into the image to facilitate
planning of the procedure.
[0040] Further referring to FIG. 4, dialog box 410 allows the
surgeon to control various aspects of how trajectories and labels
are displayed. Whenever the surgeon initiates a command to store a
trajectory, a row is automatically created in dialog box 410 and is
identified by a number appearing in column 440. The surgeon has the
option of removing a saved trajectory from display 403a by
selecting the appropriate button in column 445. The color or
texture of a button in column 445 can indicate the current icon
display status.
[0041] Column 450 contains fields which indicate the text used in
the labels for each stored trajectory. Computer 110 can select
numerical values as defaults, which are illustrated in labels.
425a-d, or the surgeon may select a custom label. This is
accomplished by using computer 110's mouse to select the
appropriate field of column 450 corresponding to the stored
trajectory to be renamed. Once selected, the surgeon can use
computer 110's keyboard to enter the desired text for the label.
Furthermore, the label of each trajectory can be selectively
displayed by activating the appropriate button in column 455 with
the mouse. The color or texture of the button can be used to
indicate the display status of the label for each stored
trajectory. In this example, buttons corresponding to trajectories
1,5,6, and 7 are in the "on" state which results only in labels
425a-d being displayed in window 403a.
[0042] Selection of one of the buttons in column 456 causes the
default color of the stored trajectory to be overridden by the
user. Activation of the appropriate button displays a palette of
colors from which one may choose to color the respective icon.
[0043] The surgeon also has the ability to select the mode of
display for each icon. Selecting pull-down menu 458 allows the user
to chose from one of three different display modes for each stored
trajectory. The first mode, "Hind->Tip," creates an icon by
drawing a line from the instruments hind position to the
instruments tip position as shown in icons 415a-e. The second mode,
"Tip->Ext.," creates an icon by drawing a line from the
instrument's tip to the end of the extension. This mode is shown in
icon 415f, which is displayed as a light colored cross to denote
the extension. The third display mode, "Hind->Ext.," draws a
line from the hind of the instrument to the tip of the extension.
This mode is exemplified in icon 415g and extension 418. Column 457
indicates the display mode associated with each stored
trajectory.
[0044] Further referring to FIG. 4, the surgeon has the option to
have computer 110 compute and display measurements between selected
trajectories. Button 459 commands computer 110 to display the
measurements and allows the user to select which measurements to
display. Pull-down menus 461, 463 allow the user to choose the
trajectories which will be used to perform the measurements. Note
that the real-time instrument may be used in conjunction with one
or more pairs of any of the stored trajectories, or the
measurements may be made against one or more pairs of any two saved
trajectories. Text fields 460, 462 indicate which trajectories will
be used in the measurement. The results of the measurement
calculation will be displayed in windows 403a-b. In FIG. 4, the
planar angle between real-time trajectory 417 and stored trajectory
415a is shown at 470 in window 403b and 480 in window 403a. The
difference between values 470 and 480 is due to the different
planar geometries associated with images 402 and 405.
[0045] Referring to FIG. 5, components and modules of a computer
system 110 used to perform various processes of the present
invention are described. Although a STEALTH STATION.RTM. image
guided system manufactured by Medtronic Sofamor Danek has been
identified, it will be appreciated that the present invention may
be utilized with other types of computer systems. One aspect of the
computer system 110 includes a graphical user interface system
operating in conjunction with a display screen of a display monitor
115. The graphical user interface system is preferably implemented
in conjunction with operating system 515 running computer 110 for
displaying arid managing the display objects of the system. The
graphical user interface is implemented as part of the computer
system 110 to receive input data and commands from a conventional
keyboard 520 and mouse 525. Foot-switch 280 is also configured to
enable the user to initiate the storage of instrument 125's
real-time trajectory. For simplicity of the drawings and
explanation, many components of a conventional computer system have
not been illustrated such as address buffers, memory buffers, and
other standard control circuits because these elements are well
known in the art and a detailed description thereof is not
necessary for understanding the present invention.
[0046] A computer program used to implement the various steps of
the present invention is generally located in memory unit 500, and
the processes of the present invention are carried out through the
use of a central processing unit (CPU) 505. Those skilled in the
art will appreciate that the memory unit 500 is representative of
both read-only memory and random access memory. The memory unit
also contains a database 550 that stores data, for example, image
data and tables, including such information as stored instrument
tip and hind positions, extension values, and geometric transform
parameters, used in conjunction with the present invention. CPU
505, in combination with the computer software comprising operating
system 515, scanning software module 530, tracking software module
535, calibration software module 540, and display software module
545, controls the operations and processes of computer system 110.
The processes implemented by CPU 505 may be communicated as
electrical signals along bus 560 to an I/O interface 570 and a
video interface 575.
[0047] Scanning software module 530 performs the processes
associated with creating a coordinate reference system and
reference images for use in connection with the present invention
and are known to those skilled in the art. Tracking software module
535 performs the processes necessary for tracking objects in an
image guided system as described herein and are known to those
skilled in the art. Calibration software module 640 computes the
geometric transform which corrects for image distortions and
registers the images to the anatomical reference frame 235, and
thus the patient's anatomy.
[0048] Display software module 545 applies, and if desired,
computes the offsets between the guide tracking markers 230 and the
tip and hind of the instrument in order generate an icon
representing the trajectory of the instrument for superposition
over the images. For instruments with fixed lengths and
angulations, these offsets can be measured once and stored in
database 550. The user would then select from a list of
instruments, the one being used in the procedure so the proper
offsets are applied by display software module 545. For instruments
with variable lengths and angulations, the offsets could be
measured manually and entered via keyboard 520, or measured using
the navigation system 100 in conjunction a tracked pointer or
tracked registration jig (not shown). If a tracked pointer is used,
the user will touch the tip and tail of the instrument while it is
being tracked. The offsets are computed by display software module
545 and stored for later use. Similarly, if a tracked registration
jig is used, the instrument is placed within the jig while it is
being tracked. The jig will measure the extremities of the
instrument and display software module 545 will again compute the
offsets and store them for later use in database 550.
[0049] Pre-acquired image data 105 can be fed directly into
computer 110 digitally through I/O interface 570, or may be
supplied as video data through video interface 575. In addition,
items shown as stored in memory can also be stored, at least
partially, on hard disk 580 if memory resources are limited.
Furthermore, while not explicitly shown, image data may also be
supplied over a network, through a mass storage device such as a
hard drive, optical disks, tape drives, or any other type of data
transfer and storage devices which are known in the art.
[0050] FIG. 6 shows a block diagram illustrating a method for
calculating a planar angle between two trajectories for the
preferred embodiment. After surgeon 270 selects the trajectories
using pull-down menus 461,463 as described above, the tip and the
hind positions of each trajectory are projected into the image
plane. Since x-ray receiving section 216 is tracked by navigation
system 100 utilizing tracking markers 222, the coordinates of the
image plane are well defined. Using the tip, hind, and image plane
coordinates, the projection is performed using techniques well
known to those skilled in the art (610). A first line segment is
constructed by connecting the projected tip and hind points
corresponding to the first trajectory computed above (step 620). In
the same manner, a second line segment is constructed utilizing the
projected points of the second trajectory (step 630). The angle
corresponding to the intersections of the two aforementioned line
segments can then be computed by techniques known to those skilled
in the art (step 640).
[0051] FIG. 7 shows a block diagram illustrating a method of the
preferred embodiment for calculating a distance between points in
space as defined by two trajectories. After surgeon 270 selects two
trajectories using pull-down menus 461, 463 in the manner described
above, a first point is determined using the three-dimensional tip
position of the first trajectory as computed by navigation system
100. If a "look-ahead" extension is associated with the first
trajectory, it is added to the tip position (step 710). A second
point associated with the second trajectory is computed in the same
manner as described for step 710 (step 720). The distance may then
be computed using the three-dimensional coordinates of the first
and second points by a standard Euclidean distance formula which is
well known in the art.
[0052] The foregoing description is presented for purposes of
illustration and explanation. It is not intended to be exhaustive
or to limit the invention to the precise form disclosed, and
modifications of variations are possible in light of the above
teachings or may be acquired from practice of the invention. The
principles of the invention and its practical application enable
one skilled in the art to utilize the invention in various
embodiments and with various modifications as are suited to the
particular use contemplated.
[0053] For example, pre-acquired images obtained from different
modalities may be used in place of those produced by the C-arm
fluoroscope x-ray imager. Such modalities include, by way of
example only, computer tomography, ultrasound, PET, or magnetic
resonance imaging.
[0054] The foregoing description of the embodiments has been
provided for purposes of illustration and description. It is not
intended to be exhaustive or to limit the disclosure. Individual
elements or features of a particular embodiment are generally not
limited to that particular embodiment, but, where applicable, are
interchangeable and can be used in a selected embodiment, even if
not specifically shown or described. The same may also be varied in
many ways. Such variations are not to be regarded as a departure
from the disclosure, and all such modifications are intended to be
included within the scope of the disclosure.
* * * * *