U.S. patent application number 15/126425 was filed with the patent office on 2017-03-23 for method for determining the spatial position of objects.
The applicant listed for this patent is Brainlab AG. Invention is credited to Oliver Fleig, Sabine Kling, Timo Neubauer, Mario Schubert.
Application Number | 20170079723 15/126425 |
Document ID | / |
Family ID | 50792425 |
Filed Date | 2017-03-23 |
United States Patent
Application |
20170079723 |
Kind Code |
A1 |
Fleig; Oliver ; et
al. |
March 23, 2017 |
METHOD FOR DETERMINING THE SPATIAL POSITION OF OBJECTS
Abstract
The present invention relates to a method for determining the
spatial position of objects, in particular medical objects. First
position data is acquired that describes a spatial position of an
object in a first coordinate system. First transformation data is
acquired that transforms the object's position from the first
coordinate system to a second coordinate system. Based on the
foregoing data, second position data is acquired that specifies the
spatial position of the object in the second coordinate system.
Second transformation data is acquired that transforms the object's
position from the second coordinate system to an inertial
coordinate system. Based on the second position data and the second
transformation data, inertial position data is determined that
specifies a position of the object in the inertial coordinate
system.
Inventors: |
Fleig; Oliver; (Baldham,
DE) ; Neubauer; Timo; (Neukeferloh, DE) ;
Schubert; Mario; (Poing, DE) ; Kling; Sabine;
(Unterschleissheim, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Brainlab AG |
Feldkirchen |
|
DE |
|
|
Family ID: |
50792425 |
Appl. No.: |
15/126425 |
Filed: |
May 14, 2014 |
PCT Filed: |
May 14, 2014 |
PCT NO: |
PCT/EP2014/059870 |
371 Date: |
September 15, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 2034/2055 20160201;
A61B 34/20 20160201; A61B 2034/2063 20160201; A61B 2034/2048
20160201; A61B 2034/2051 20160201; A61B 2090/502 20160201 |
International
Class: |
A61B 34/20 20060101
A61B034/20 |
Claims
1. A data processing system, comprising at least one computer
having at least one processor configured to execute a
computer-implemented medical data processing method for determining
the spatial position of medical objects, the data processing method
comprising the steps of: acquiring, at the processor and via a
medical tracking system comprising a sensor array, first position
data which comprise first position information describing the
spatial position of an object within a first co-ordinate system
positionally assigned to said sensor array which is configured to
determine the spatial position of at least one tracking marker
attached to the object; acquiring, at the processor, first
transformation data which comprise first transformation information
describing a transformation of the object's position from the first
co-ordinate system into a second co-ordinate system positionally
assigned to an inertial sensor array which is attached to the
medical tracking system's sensor array and configured to sense any
motion of the medical tracking system's sensor array within an
inertial co-ordinate system positionally assigned to a treatment
room which accommodates the object; acquiring, at the processor and
on the basis of the first position data and the first
transformation data, second position data which comprise second
position information describing the spatial position of the object
within the second co-ordinate system; acquiring, at the processor,
second transformation data which comprise second transformation
information describing a transformation of the object's position
from the second co-ordinate system into the inertial co-ordinate
system; determining, by the processor and on the basis of the
second position data and the second transformation data, inertial
position data which comprise inertial position information
describing the spatial position of the object within the inertial
co-ordinate system.
2. A computer implemented medical data processing method for
determining the spatial position of medical objects, the method
comprising executing, on at least one processor of at least one
computer, the steps of: acquiring at the processor and via a
medical tracking system comprising a sensor array, first position
data which comprise first position information describing the
spatial position of an object within a first co-ordinate system
positionally assigned to said sensor array which is configured to
determine the spatial position of at least one tracking marker
attached to the object; acquiring, at the processor, first
transformation data which comprise first transformation information
describing a transformation of the object's position from the first
co-ordinate system into a second co-ordinate system positionally
assigned to an inertial sensor array which is attached to the
medical tracking system's sensor array and configured to sense any
motion of the medical tracking system's sensor array within an
inertial co-ordinate system positionallly assigned to a treatment
room which accommodates the object; acquiring, at the processor and
on the basis of the first position data and the first
transformation data, second position data which comprise second
position information describing the spatial position of the object
within the second co-ordinate system; acquiring, at the processor,
second transformation data which comprise second transformation
information describing a transformation of the object's position
from the second co-ordinate system into the inertial co-ordinate
system; determining, by the processor and on the basis of the
second position data and the second transformation data, inertial
position data which comprise inertial position information
describing the spatial position of the object within the inertial
co-ordinate system.
3. (canceled)
4. The method according to claim 2, wherein the second co-ordinate
system corresponds to the first co-ordinate system.
5. The method according to any one of claim 2, wherein the inertial
position data are stored for at least one object and in particular
for a plurality of points which are palpated during a point
acquisition and registration procedure, wherein the tracked object
is a point acquisition instrument, in particular a pointer
instrument.
6. (canceled)
7. A tracking system for determining the spatial position of
medical objects comprising: a sensor array which is configured to
determine the spatial position of at least one tracking marker
attached to an object; an inertial sensor array which is attached
to said sensor array; and the computer of claim 14.
8. The tracking system according to claim 7, wherein the sensor
array comprises at least one sensor selected from the group
consisting of: optical cameras, which are sensitive to infrared
light; EM (electromagnetic) tracking sensors; ultrasound tracking
sensors.
9. The tracking system according to claim 7, wherein the inertial
sensor array comprises at least one sensor selected from the group
consisting of: accelerometers; sensors or sensor arrangements which
are configured to be sensitive to the earth's gravitational field;
magnetometers; gyroscopes; optical cameras, which are sensitive to
infrared light; pressure sensors which are sensitive to atmospheric
pressure.
10. The tracking system according to claim 7, wherein at least the
sensor array and the inertial sensor array are freely movable.
11. The tracking system according to claim 10, wherein the sensor
array and the inertial sensor array are housed in a common unit
that is configured to be worn by a person, as a device similar to
spectacles, and to provide the wearer with additional information
based on the determined spatial position of the at least one
object.
12. The tracking system according to claim 7, which is also
configured to process signals from at least one sensor assigned to
the tracking system, which is in turn configured to detect the
motion of an untracked object within the inertial co-ordinate
system and comprises at least one pressure sensor which is arranged
between a part of a patient's body and a supporting structure and
allows an indication as to whether said object has moved.
13. A non-transitory computer-readable program storage medium
storing a computer program which, when executed on a processor of a
computer or leaded into the memory of a computer, causes the
computer to perform a computer-implemented medical data processing
method for determining the spatial position of medical objects, the
data processing method comprising the steps of: acquiring, at the
processor and via a medical tracking system comprising a sensor
array, first position data which comprise first position
information describing the spatial position of an object within a
first co-ordinate system positionally assigned to said sensor array
which is configured to determine the spatial position of at least
one tracking marker attached to the object; acquiring, at the
processor, first transformation data which comprise first
transformation information describing a transformation of the
object's position from the first co-ordinate system into a second
co-ordinate system positionally assigned to an inertial sensor
array which is attached to the medical tracking system's sensor
array and configured to sense any motion of the medical tracking
system's sensor array within an inertial co-ordinate system
positionally assigned to a treatment room which accommodates the
object; acquiring, at the processor and on the basis of the first
position data and the first transformation data, second position
data which comprise second position information describing the
spatial position of the object within the second co-ordinate
system; acquiring, at the processor and on the basis of the first
position data and the first transformation data, second position
data which comprise second position information describing the
spatial position of the object within the second co-ordinate
system; acquiring, at the processor, second transformation data
which comprise second transformation information describing a
transformation of the object's position from the second co-ordinate
system into the inertial co-ordinate system; determining, by the
processor and on the basis of the second position data and the
second transformation data, inertial position data which comprise
inertial position information describing the spatial position of
the object within the inertial co-ordinate system.
14. A computer comprising the non-transitory computer-readable
program storage medium according to claim 13.
15. A medical tracking system for determining a spatial position of
medical objects within a treatment room, comprising: a sensor array
configured to determine a spatial position of an object within a
first coordinate system, wherein the first coordinate system is
defined relative to the sensor array; an inertial sensor array
configured to detect motion of the sensor array relative to a
global coordinate system associated with the treatment room; and a
computer having at one processor configured to execute a computer
program that configures the processor to: acquire, via the sensor
array, first position information that indicates the position of
the object within the first coordinate system; acquire first
transformation information that describes a transformation from the
first coordinate system to a second coordinate system, wherein the
second coordinate system is defined relative to the inertial sensor
array; transform the position of the object from the first
coordinate system to the second coordinate system based on the
first position information and the first transformation
information; acquire second transformation information that
describes a transformation from the second coordinate system to the
global coordinate system based on motion detected by the inertial
sensor array; and determine global position information that
describes the position of the object within the global coordinate
system of the treatment room.
16. The medical tracking system of claim 15, wherein the sensor
array and the inertial sensor array are freely movable at least
within the treatment room.
17. The medical tracking system of claim 15, further comprising a
common unit housing the sensor array and the inertial sensor
array.
18. The medical tracking system of claim 17, wherein the common
unit is a wearable, spectacle-like device.
19. The medical tracking system of claim 18, wherein the wearable,
spectacle-like devices includes a head-mounted display.
20. The medical tracking system of claim 15, wherein the inertial
sensor array is attached to sensor array.
21. The medical tracking system of claim 15, wherein the first
coordinate system corresponds to the second coordinate system.
22. The medical tracking system of claim 15, wherein the sensor
array determines the spatial position of the object within the
first coordinate system based on at least one tracking marker
attached to the object.
Description
[0001] The invention relates to the general technical field of
determining the spatial position of objects in a medical
environment. In medical procedures such as image-guided surgery
(IGS), it is desirable to know the spatial position (spatial
location and/or spatial orientation) of objects such as medical
instruments and devices, as well as anatomical structures of a
patient who is to be treated. The spatial position of a medical
instrument or a medical device relative to an anatomical structure
can for example be determined in order to provide medical staff
with a virtual representation of the medical instrument or device
and the anatomical structure in their correct spatial relationship,
such that a medical procedure can be carried out on the patient
with the aid of image guidance.
[0002] For this purpose, medical tracking systems are used which
are configured to determine the spatial position of objects
provided with trackable tracking markers, and which provide a
medical navigation system with the corresponding data, such that
the tracked objects can ultimately be visualised to medical staff
in the correct position relative to each other by means of a
display device such as a computer monitor.
[0003] Optical navigation systems are a specific type of navigation
system which usually comprise a camera array, a computer and a
display, wherein all of these components have to be located within
the operating theatre. The camera array is configured to determine
the position of objects such as surgical instruments which have
detectable tracking markers, in particular a so-called reference
star, attached to them. In order to track an object over time, its
spatial position has to be determined at different points in time
relative to a common reference co-ordinate system, for reference
purposes, and stored. Such a reference co-ordinate system is
usually established by a so-called reference array, the position of
which can also be determined with the aid of the camera array. It
is therefore necessary to simultaneously detect the position of
both the object to be tracked and the reference array which may be
provided within the operating theatre at an expedient position, for
example on the operating table or on an anatomical structure. Data
concerning the instrument position and the reference array position
are determined for each point in time, for example with respect to
a reference co-ordinate system assigned to the reference array, and
stored. DE 196 396 15 shows a neuronavigation system for surgery,
comprising a reference array with optically detectable markers
which reflect infrared light.
[0004] However, as the number of surgical instruments to be tracked
by an optical tracking system increases, so too does the issue of
"line of sight". This because a permanent line of sight to the
markers of each of the objects to be tracked and also to the
reference array has to be ensured, which however becomes
increasingly difficult to maintain as the number of objects
increases.
[0005] One problem to be solved by the invention is therefore that
of providing a method for determining the spatial position of
objects, in particular within a surgical environment, which at
least partially overcomes the problems of the prior-art tracking
and navigation systems, in particular the problems arising from
line-of-sight issues in connection with optical tracking
systems.
[0006] This problem is solved by the subject-matter of any appended
independent claim. Advantages, advantageous features, advantageous
embodiments and advantageous aspects of the present invention are
disclosed in the following and contained in the subject-matter of
the independent claims. Different advantageous features can be
combined in accordance with the invention wherever technically
expedient and feasible. Specifically, a feature of one embodiment
which has the same or a similar function to another feature of
another embodiment can be exchanged with said other feature, and a
feature of one embodiment which adds an additional function to
another embodiment can in particular be added to said other
embodiment.
[0007] In accordance with the present invention, a method for
determining the spatial position of objects, in particular medical
objects, comprises the following steps: [0008] acquiring first
position data which comprise first position information describing
the spatial position of an object within a first co-ordinate
system; [0009] acquiring first transformation data which comprise
first transformation information describing a transformation of the
object's position from the first co-ordinate system into a second
co-ordinate system; [0010] acquiring, on the basis of the first
position data and the first transformation data, second position
data which comprise second position information describing the
spatial position of the object within the second co-ordinate
system; [0011] acquiring second transformation data which comprise
second transformation information describing a transformation of
the object's position from the second co-ordinate system into an
inertial co-ordinate system; [0012] determining, on the basis of
the second position data and the second transformation data,
inertial position data which comprise inertial position information
describing the spatial position of the object within the inertial
co-ordinate system.
[0013] Within the framework of the present invention, the term of
spatial position encompasses in particular at least one of spatial
location and spatial orientation. For certain applications, such as
for example determining the inertial position data on the basis of
the second position data and the second transformation data within
the method outlined in the preceding paragraph, it can be
sufficient to consider preferably the spatial orientation. In
particular, the first position data and the second position data
describe (in particular define) the spatial orientation of object.
In particular, the position of the object is understood to be
defined by preferably (only) the orientation of the object. It is
not necessary to have knowledge of the location (i.e. the
three-dimensional coordinates at which the object is located) of
the object. Rather, it will be sufficient to have knowledge of the
orientation (i.e. the spatial alignment which may be defined by
angular values in a three-dimensional--e.g. angular--co-ordinate
system) of the object.
[0014] In the framework of the present invention, the terms
"spatial position", "spatial location" and "spatial orientation"
are also called merely "position", "location" and "orientation",
respectively, without using the adjective "spatial", however with
the same meaning as if the adjective "spatial" were used.
[0015] The present invention is described in other terms in the
following paragraph, wherein this concise description is however to
be considered merely as an example and in no way limits the
invention to the features described in said paragraph.
[0016] The present invention provides a method for determining the
spatial position of medical objects such as surgical instruments
and anatomical structures, both of which are provided with tracking
markers, wherein the position of each of the tracking markers and
therefore each of the corresponding objects is determined by means
of a tracking sensor array, in particular a tracking camera array
comprising one or more cameras, configured to detect tracking
markers attached to the objects to be tracked. Data concerning the
position of each of the objects are initially determined by the
tracking sensor array with reference to the tracking sensor
co-ordinate system and then transformed into data describing the
position of each of the objects with respect to a co-ordinate
system assigned to an inertial sensor array which is fixed to the
tracking sensor array and therefore capable of detecting any
movement of the tracking sensor array with respect to the "global
co-ordinate system" which is invariant over time. By transforming
the data, considering a possible movement of the tracking sensor
array and storing the positional data with respect to the global
co-ordinate system or inertial co-ordinate system for each of the
tracked objects, the inertial co-ordinate system acts as a centre
of reference, thereby enabling a comparison of the relative
position of the tracked objects over time, even when the tracking
sensor array together with the tracking sensor co-ordinate system
assigned to it is moved relative to the surgical environment, and
even without any additionally provided tracking reference as known
from the prior art.
[0017] In accordance with one preferred embodiment of the present
invention, the first position data are acquired by means of a
medical tracking system comprising a (tracking) sensor array
configured to determine the spatial position of at least one
tracking marker which is attached to an object to be tracked,
wherein the first co-ordinate system is in particular positionally
assigned to said sensor array.
[0018] Such a sensor array can in particular comprise any kind of
sensor(s) which can be used to determine the position of tracking
markers attached to the object to be tracked. Feasible tracking
sensors include for example optical cameras, which can also include
cameras which are sensitive to infrared light, EM (electromagnetic)
tracking sensors and ultrasound tracking sensors.
[0019] Although most aspects of the present invention are described
here in connection with an optical tracking system comprising one
or more optical tracking cameras, any kind of non-optical tracking
system may also benefit from the present invention. The tracking
sensor array can for example be rendered movable or even portable
and can therefore be placed nearer to the objects to be tracked,
which can increase its accuracy during the tracking procedure. A
tracking reference which acts as a centre of reference, and which
is therefore an essential component of conventional tracking
systems with movable tracking sensors, is not however needed in
accordance with the present invention, since the position of the
tracked objects is determined with respect to an inertial
co-ordinate system which remains invariant over time.
[0020] The inertial co-ordinate system can for example be
positionally assigned to a treatment room which accommodates the
treatment/surgical set-up. In other words, the inertial co-ordinate
system is a "global co-ordinate system" which is invariant with
respect to the operating theatre.
[0021] The second co-ordinate system can also be positionally
assigned to (i.e. positionally invariant with respect to) an
inertial sensor array which is fixedly attached to the medical
tracking system's sensor array and configured to sense any motion
of the medical tracking system's sensor array within the inertial
co-ordinate system, wherein the second co-ordinate system in
particular corresponds to the first co-ordinate system. An
expedient inertial sensor array can comprise at least one sensor
selected from the group consisting of: [0022] accelerometers,
[0023] sensors or sensor arrangements which are configured to be
sensitive to the earth's gravitational field; [0024] magnetometers;
[0025] gyroscopes; [0026] optical cameras, in particular cameras
which are sensitive to infrared light; [0027] pressure sensors
which are sensitive to atmospheric pressure.
[0028] Currently available inertial sensors may be used to
precisely determine the spatial orientation of the object in the
inertial co-ordinate system. Determination of the exact
three-dimensional spatial location is however also basically
achievable from the viewpoint of physics. In the framework of the
present invention, it is sufficient to determine the spatial
orientation, exact knowledge about the three-dimensional location
of the object is not necessary to carry out the present
invention.
[0029] The transformations applied in the framework of the present
invention (in particular the transformation of the object's
position from the second co-ordinate system into the inertial
co-ordinate system) therefore comprise at least one of the
following: [0030] a rotational transformation (in three rotational
degrees of freedom) from the second co-ordinate into the inertial
co-ordinate system, which transformation is usable to determine the
spatial orientation of the object in the inertial co-ordinate
system; [0031] a complete transformation (in three rotational
degrees of freedom and three translational degrees of freedom) from
the second co-ordinate system into the inertial co-ordinate system,
which transformation is usable to determine the complete spatial
position (i.e. both the spatial location and the spatial
orientation) of the object in the inertial co-ordinate system.
[0032] The second co-ordinate system assigned to the inertial
sensor array does not necessarily have to be different to the first
co-ordinate system assigned to the tracking sensor array, but
rather can also be identical to it.
[0033] In accordance with another preferred embodiment of the
present invention, the inertial position data are stored for at
least one object and/or anatomical structure and in particular for
a plurality of points which are palpated (for example during a
point acquisition and registration procedure), wherein the tracked
object is a point acquisition instrument, in particular a pointer
instrument. Since the positional data for each of the
objects/points can be stored over time and therefore compared
relative to a common centre of reference, namely the inertial
co-ordinate system, an accurate tracking procedure and/or point
acquisition procedure is possible even without an invariantly
installed camera array and/or additionally provided reference
array.
[0034] Another aspect of the present invention relates to a program
which, when running on a computer, causes the computer to perform
the method steps of any embodiment described above and/or to a
program storage medium on which the program is stored and/or to a
computer comprising such a program storage medium and/or to a
signal wave, in particular a digital signal wave, carrying
information which represents the program.
[0035] A third aspect of the present invention relates to a
tracking system which comprises: [0036] a sensor array which is
configured to determine the spatial position of at least one
tracking marker attached to an object; [0037] an inertial sensor
array which is attached to said sensor array; and [0038] a computer
which is configured to perform the method steps as described
above.
[0039] One preferred embodiment of the tracking system in
accordance with the invention comprises a freely movable tracking
sensor array and a freely movable inertial sensor array attached to
it. The tracking sensor array and the inertial sensor array are
preferably accommodated in a common unit or housing which is freely
movable within the operating theatre and relative to the inertial
co-ordinate system. A tracking system in accordance with the
present invention can consist of a mobile phone comprising an
optical camera which can be used as a tracking sensor array and
accelerometers which can be used as inertial sensors.
[0040] The common unit which accommodates both the tracking sensor
array and the inertial sensor array can be configured so as to be
worn by a person, in particular as a device similar to spectacles,
and specifically configured to provide the wearer with additional
information based on the determined spatial position of the at
least one object. One example of such a spectacle-like device which
can be used in connection with the present invention is the
miniaturised computer Google Glass.TM. which is worn as a so-called
optical head-mounted display. By wearing such a device, surgeons
can keep their hands free for other tasks and the tracking sensor
array can be automatically positioned right next to the region of
interest and/or object to be tracked.
[0041] Using such a spectacle-like device, it is for example
possible to detect mistakes during a registration procedure and
inform the user of the detected problem directly on the device by
overlaying the information. Depending on the device used, the
information could be overlaid directly onto the surgeon's field of
view or onto a video image being displayed within the surgeon's
field of view.
[0042] There are no sterility issues, since the spectacle-like
device is worn, like regular spectacles, on the nose. Unlike
existing solutions, it is not necessary to for example drape a
monitor in order to press buttons on the monitor, or to drape a
smart device in such a way that it can be used within the sterile
field.
[0043] The terminology used in this document is described in more
detail below, wherein this description also forms part of the
disclosure of the present invention.
[0044] Within the framework of the invention, computer program
elements can be embodied by hardware and/or software (this includes
firmware, resident software, micro-code, etc.). Within the
framework of the invention, computer program elements can take the
form of a computer program product which can be embodied by a
computer-usable, in particular computer-readable data storage
medium comprising computer-usable, in particular computer-readable
program instructions, "code" or a "computer program" embodied in
said data storage medium for use on or in connection with the
instruction-executing system. Such a system can be a computer; a
computer can be a data processing device comprising means for
executing the computer program elements and/or the program in
accordance with the invention, in particular a data processing
device comprising a digital processor (central processing unit or
CPU) which executes the computer program elements, and optionally a
volatile memory (in particular a random access memory or RAM) for
storing data used for and/or produced by executing the computer
program elements. Within the framework of the present invention, a
computer-usable, in particular computer-readable data storage
medium can be any data storage medium which can include, store,
communicate, propagate or transport the program for use on or in
connection with the instruction-executing system, apparatus or
device. The computer-usable, in particular computer-readable data
storage medium can for example be, but is not limited to, an
electronic, magnetic, optical, electromagnetic, infrared or
semiconductor system, apparatus or device or a medium of
propagation such as for example the Internet. The computer-usable
or computer-readable data storage medium could even for example be
paper or another suitable medium onto which the program is printed,
since the program could be electronically captured, for example by
optically scanning the paper or other suitable medium, and then
compiled, interpreted or otherwise processed in a suitable manner.
The data storage medium is preferably a non-volatile data storage
medium. The computer program product and any software and/or
hardware described here form the various means for performing the
functions of the invention in the example embodiments. The computer
and/or data processing device can in particular include a guidance
information device which includes means for outputting guidance
information. The guidance information can be outputted, for example
to a user, visually by a visual indicating means (for example, a
monitor and/or a lamp) and/or acoustically by an acoustic
indicating means (for example, a loudspeaker and/or a digital
speech output device) and/or tactilely by a tactile indicating
means (for example, a vibrating element or a vibration element
incorporated into an instrument). For the purpose of this document,
a computer is a technical computer which in particular comprises
technical, in particular tangible components, in particular
mechanical and/or electronic components. Any device mentioned as
such in this document is a technical and in particular tangible
device.
[0045] It is the function of a marker to be detected by a marker
detection device (for example, a camera or an ultrasound receiver
or analytical devices such as CT or MRI devices) in such a way that
its spatial position (i.e. its spatial location and/or
orientation/alignment) can be ascertained. The detection device is
in particular part of a navigation system. The markers can be
active markers. An active marker can for example emit
electromagnetic radiation and/or waves which can be in the
infrared, visible and/or ultraviolet spectral range. A marker can
also however be passive, i.e. can for example reflect
electromagnetic radiation in the infrared, visible and/or
ultraviolet spectral range or can block X-ray radiation. To this
end, the marker can be provided with a surface which has
corresponding reflective properties or can be made of metal in
order to block the X-ray radiation. It is also possible for a
marker to reflect and/or emit electromagnetic radiation and/or
waves in the radio frequency range or at ultrasound wavelengths. A
marker preferably has a spherical and/or spheroid shape and can
therefore be referred to as a marker sphere; markers can however
also exhibit a cornered, for example cubic, shape.
[0046] A marker device can for example be a reference star or a
pointer or a single marker or a plurality of (individual) markers
which are then preferably in a predetermined spatial relationship.
A marker device comprises one, two, three or more markers, wherein
two or more such markers are in a predetermined spatial
relationship. This predetermined spatial relationship is in
particular known to a navigation system and is for example stored
in a computer of the navigation system.
[0047] A "reference star" refers to a device with a number of
markers, advantageously three markers, attached to it, wherein the
markers are (in particular detachably) attached to the reference
star such that they are stationary, thus providing a known (and
advantageously fixed) position of the markers relative to each
other. The position of the markers relative to each other can be
individually different for each reference star used within the
framework of a surgical navigation method, in order to enable a
surgical navigation system to identify the corresponding reference
star on the basis of the position of its markers relative to each
other. It is therefore also then possible for the objects (for
example, instruments and/or parts of a body) to which the reference
star is attached to be identified and/or differentiated
accordingly. In a surgical navigation method, the reference star
serves to attach a plurality of markers to an object (for example,
a bone or a medical instrument) in order to be able to detect the
position of the object (i.e. its spatial location and/or
alignment). Such a reference star in particular features a way of
being attached to the object (for example, a clamp and/or a thread)
and/or a holding element which ensures a distance between the
markers and the object (in particular in order to assist the
visibility of the markers to a marker detection device) and/or
marker holders which are mechanically connected to the holding
element and which the markers can be attached to.
[0048] The present invention is also directed to a navigation
system for computer-assisted surgery. This navigation system
preferably comprises the aforementioned computer for processing the
data provided in accordance with the data processing method as
described in any one of the preceding embodiments. The navigation
system preferably comprises a detection device for detecting the
position of the detection points which represent the main points
and auxiliary points, in order to generate detection signals and to
supply the generated detection signals to the computer, such that
the computer can determine the absolute main point data and
absolute auxiliary point data on the basis of the detection signals
received. In this way, the absolute point data can be provided to
the computer. The navigation system also preferably comprises a
user interface for receiving the calculation results from the
computer (for example, the position of the main plane, the position
of the auxiliary plane and/or the position of the standard plane).
The user interface provides the received data to the user as
information. Examples of a user interface include a display device
such as a monitor, or a loudspeaker. The user interface can use any
kind of indication signal (for example a visual signal, an audio
signal and/or a vibration signal). One example of a display device
is an augmented reality device (also referred to as augmented
reality glasses) which can be used as so-called "goggles" for
navigating. A specific example of such augmented reality glasses is
Google Glass (a trademark of Google, Inc.). An augmented reality
device can be used both to input information into the computer of
the navigation system by user interaction and to display
information outputted by the computer.
[0049] A navigation system, in particular a surgical navigation
system, is understood to mean a system which can comprise: at least
one marker device; a transmitter which emits electromagnetic waves
and/or radiation and/or ultrasound waves; a receiver which receives
electromagnetic waves and/or radiation and/or ultrasound waves; and
an electronic data processing device which is connected to the
receiver and/or the transmitter, wherein the data processing device
(for example, a computer) in particular comprises a processor (CPU)
and a working memory and advantageously an indicating device for
issuing an indication signal (for example, a visual indicating
device such as a monitor and/or an audio indicating device such as
a loudspeaker and/or a tactile indicating device such as a
vibrator) and a permanent data memory, wherein the data processing
device processes navigation data forwarded to it by the receiver
and can advantageously output guidance information to a user via
the indicating device. The navigation data can be stored in the
permanent data memory and for example compared with data stored in
said memory beforehand.
[0050] The method in accordance with the invention is in particular
a data processing method. The data processing method is preferably
performed using technical means, in particular a computer. The data
processing method is preferably constituted to be executed by or on
a computer and in particular is executed by or on the computer. In
particular, all the steps or merely some of the steps (i.e. less
than the total number of steps) of the method in accordance with
the invention can be executed by a computer. The computer in
particular comprises a processor and a memory in order to process
the data, in particular electronically and/or optically. The
calculating steps described are in particular performed by a
computer. Determining steps or calculating steps are in particular
steps of determining data within the framework of the technical
data processing method, in particular within the framework of a
program. A computer is in particular any kind of data processing
device, in particular electronic data processing device. A computer
can be a device which is generally thought of as such, for example
desktop PCs, notebooks, netbooks, etc., but can also be any
programmable apparatus, such as for example a mobile phone or an
embedded processor. A computer can in particular comprise a system
(network) of "sub-computers", wherein each sub-computer represents
a computer in its own right. The term "computer" includes a cloud
computer, in particular a cloud server. The term "cloud computer"
includes a cloud computer system which in particular comprises a
system of at least one cloud computer and in particular a plurality
of operatively interconnected cloud computers such as a server
farm. Such a cloud computer is preferably connected to a wide area
network such as the World Wide Web (WWW) and located in a so-called
cloud of computers which are all connected to the World Wide Web.
Such an infrastructure is used for "cloud computing", which
describes computation, software, data access and storage services
which do not require the end user to know the physical location
and/or configuration of the computer delivering a specific service.
In particular, the term "cloud" is used in this respect as a
metaphor for the Internet (or World Wide Web). In particular, the
cloud provides computing infrastructure as a service (IaaS). The
cloud computer can function as a virtual host for an operating
system and/or data processing application which is used to execute
the method of the invention. The cloud computer is for example an
elastic compute cloud (EC2) as provided by Amazon Web Services.TM..
A computer in particular comprises interfaces in order to receive
or output data and/or perform an analogue-to-digital conversion.
The data are in particular data which represent physical properties
and/or which are generated from technical signals. The technical
signals are in particular generated by means of (technical)
detection devices (such as for example devices for detecting marker
devices) and/or (technical) analytical devices (such as for example
devices for performing imaging methods), wherein the technical
signals are in particular electrical or optical signals. The
technical signals in particular represent the data received or
outputted by the computer. The computer is preferably operatively
coupled to a display device which allows information outputted by
the computer to be displayed, for example to a user. One example of
a display device is an augmented reality device (also referred to
as augmented reality glasses) which can be used as "goggles" for
navigating.
[0051] The expression "acquiring data" in particular encompasses
(within the framework of a data processing method) the scenario in
which the data are determined by the data processing method or
program. Determining data in particular encompasses measuring
physical quantities and transforming the measured values into data,
in particular digital data, and/or computing the data by means of a
computer and in particular within the framework of the method in
accordance with the invention. The meaning of "acquiring data" also
in particular encompasses the scenario in which the data are
received or retrieved by the data processing method or program, for
example from another program, a previous method step or a data
storage medium, in particular for further processing by the data
processing method or program. The expression "acquiring data" can
therefore also for example mean waiting to receive data and/or
receiving the data. The received data can for example be inputted
via an interface. The expression "acquiring data" can also mean
that the data processing method or program performs steps in order
to (actively) receive or retrieve the data from a data source, for
instance a data storage medium (such as for example a ROM, RAM,
database, hard drive, etc.), or via the interface (for instance,
from another computer or a network). The data can be made "ready
for use" by performing an additional step before the acquiring
step. In accordance with this additional step, the data are
generated in order to be acquired. The data are in particular
detected or captured (for example by an analytical device).
Alternatively or additionally, the data are inputted in accordance
with the additional step, for instance via interfaces. The data
generated can in particular be inputted (for instance into the
computer). In accordance with the additional step (which precedes
the acquiring step), the data can also be provided by performing
the additional step of storing the data in a data storage medium
(such as for example a ROM, RAM, CD and/or hard drive), such that
they are ready for use within the framework of the method or
program in accordance with the invention. The step of "acquiring
data" can therefore also involve commanding a device to obtain
and/or provide the data to be acquired. In particular, the
acquiring step does not involve an invasive step which would
represent a substantial physical interference with the body,
requiring professional medical expertise to be carried out and
entailing a substantial health risk even when carried out with the
required professional care and expertise. In particular, the step
of acquiring data, in particular determining data, does not involve
a surgical step and in particular does not involve a step of
treating a human or animal body using surgery or therapy. In order
to distinguish the different data used by the present method, the
data are denoted (i.e. referred to) as "XY data" and the like and
are defined in terms of the information which they describe, which
is then preferably referred to as "XY information" and the
like.
[0052] The present invention will work well in connection with
tools, particularly tools used in connection with orthopedics of
Brainlab.RTM., such as products called "Digital Ortho Tools", which
will then give the surgeons the feeling they are working with
intelligent tools instead of a complex navigation system. With this
invention it is possible to combine inertial sensors with a camera
system so that it is not necessary to have an external reference on
the table or on the patient and so e.g. additional pins within the
patients' bone can be avoided. Additionally line of sight issues as
known from the optical tracking system can be reduced significantly
as only one reference has to be visible to the camera during the
point acquisition. The overall system is more flexible and the
workflow of the surgeon is not interrupted by a complex navigation
system.
[0053] In the following, the invention is described with reference
to the one enclosed FIGURE which represents a preferred embodiment
of the invention, without the invention being in any way limited to
the specific features shown in this FIGURE.
[0054] FIG. 1 schematically shows an embodiment of the tracking
system in accordance with the present invention.
[0055] As is shown in FIG. 1, a tracking camera array 1 is
configured to detect the spatial position of a tracking marker
array 2 attached to a part of a patient's body (the object to be
tracked). The positional data are determined by the camera array 1
with respect to a first co-ordinate system A which is assigned to
the camera array 1. The positional data are then transformed into
positional data which describe the spatial position of the object
with respect to a second co-ordinate system B assigned to an
inertial sensor array 3 which is fixedly attached to the camera
array 1. The inertial sensor array 3 detects any motion of the
camera array 1 together with the inertial sensor array 3 with
respect to an invariant inertial co-ordinate system I. The
positional data are then transformed into data which describe the
object's position (in particular its orientation) with respect to
the inertial co-ordinate system I. The data which describe the
object's position within the inertial co-ordinate system I are then
stored by means of a computer 4 for subsequent use, for example
during a tracking procedure used to acquire the position of
landmarks on a part of the patient's body.
* * * * *