U.S. patent application number 16/946665 was filed with the patent office on 2021-02-11 for system for measuring the true dimensions and orientation of objects in a two dimensional image.
The applicant listed for this patent is ORTHOPEDIC NAVIGATION LTD.. Invention is credited to Oren Drori, Ram Nathaniel, Dan Rappaport.
Application Number | 20210038176 16/946665 |
Document ID | / |
Family ID | 1000005170005 |
Filed Date | 2021-02-11 |
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United States Patent
Application |
20210038176 |
Kind Code |
A1 |
Nathaniel; Ram ; et
al. |
February 11, 2021 |
SYSTEM FOR MEASURING THE TRUE DIMENSIONS AND ORIENTATION OF OBJECTS
IN A TWO DIMENSIONAL IMAGE
Abstract
The invention is a system for measuring the true dimensions and
orientation of objects in a two dimensional image. The system is
comprised of a ruler comprising at least one set of features each
comprised of two or more markers that are identifiable in the image
and having a known spatial relationship between them and a software
package comprising programs that allow extension of the ruler and
other objects in the two dimensional image beyond their physical
dimensions or shape. The system can be used together with
radiographic imagery means, processing means, and display means to
take x-ray images and to measure the true dimensions and
orientation of objects and to aid in the identification and
location of a surgery tool vs. anatomy in those x-ray images. The
invention provides a method of drawing and displaying on a two
dimensional x-ray image measurements of objects visible in said
image, graphical information, or templates of surgical devices.
Inventors: |
Nathaniel; Ram; (Tel Aviv,
IL) ; Rappaport; Dan; (Tel Aviv, IL) ; Drori;
Oren; (Tel Aviv, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ORTHOPEDIC NAVIGATION LTD. |
Ramat Hasharon |
|
IL |
|
|
Family ID: |
1000005170005 |
Appl. No.: |
16/946665 |
Filed: |
June 30, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16662059 |
Oct 24, 2019 |
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16946665 |
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15256642 |
Sep 5, 2016 |
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16662059 |
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14106771 |
Dec 15, 2013 |
9433390 |
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15256642 |
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12665731 |
Jun 1, 2010 |
8611697 |
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PCT/IL2008/000841 |
Jun 19, 2008 |
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14106771 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G06T 2207/30021
20130101; A61B 6/461 20130101; G06T 2207/30204 20130101; G06T
2200/04 20130101; G06T 7/0012 20130101; A61B 6/12 20130101; G06T
7/73 20170101; A61B 2090/3966 20160201; G06T 11/00 20130101; G06T
2207/10116 20130101; A61B 90/39 20160201; G06T 19/00 20130101; G06T
2207/30052 20130101; G06T 2219/012 20130101; G06T 2207/30008
20130101; G06T 2207/10121 20130101; A61B 6/5211 20130101 |
International
Class: |
A61B 6/12 20060101
A61B006/12; G06T 7/73 20060101 G06T007/73; G06T 11/00 20060101
G06T011/00; G06T 19/00 20060101 G06T019/00; A61B 90/00 20060101
A61B090/00; A61B 6/00 20060101 A61B006/00; G06T 7/00 20060101
G06T007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 21, 2007 |
IL |
184151 |
Claims
1. A system for imaging based surgical support in orthopedic
implant procedures, said system comprising: an invasive surgical
tool including a set of features identifiable in a two dimensional
(2D) medical image and having known spatial relationships between
them; receiving circuitry adapted to receive a given 2D medical
image of the surgical tool in contact with, or within, an organ of
a subject of a given orthopedic implant procedure; an image
processor adapted to derive, from the appearances of said features
in the 2D medical image, a spatial relationship between said
invasive surgical tool and the organ and determine, based on the
derived spatial relationship, an expected collocation of an
orthopedic implant in relation to the organ; and rendering
circuitry adapted to render the expected collocation upon an
associated display.
2. The system according to claim 1, wherein the 2D medical image is
an x-ray.
3. The system according to claim 1, wherein: said receiving
circuitry is further adapted to receive a series of 2D medical
images of the surgical tool in contact with, or within, the organ
of the subject of the given orthopedic implant procedure; said
image processor is further adapted to derive from each given image
of the series, from the appearances of said features in the given
image, a given spatial relationship between said invasive surgical
tool and the organ and determine for each given image of the
series, based on the derived given spatial relationship, a given
expected collocation of the orthopedic implant in relation to the
organ; and said rendering circuitry is further adapted to render
the given expected collocations in sequence in real time.
4. The system according to claim 1, wherein the image processing
circuitry is further adapted to identify a contour of the organ in
the given 2D medical image.
5. The system according to claim 1, wherein said image processor is
further adapted to derive, from the appearances of said features in
the 2D medical image, measurements of dimensions within the image
and render the measurements on the image on the associated
display.
6. A system for imaging based surgical support in orthopedic
implant procedures, said system comprising: a two dimensional (2D)
medical imaging device adapted to capture an image of a subject of
a given orthopedic implant procedure, during the implant procedure;
an image processor adapted: (i) identify, in real time, features of
an invasive surgical tool in contact with, or within, an organ of a
subject of the implant procedure; (ii) derive, from spatial
relationships between the identified features, a spatial
relationship between said invasive surgical tool and the organ; and
(iii) determine, in real time, based on the derived spatial
relationships, an expected collocation of an orthopedic implant in
relation to the organ; and rendering circuitry adapted to render,
in real time, the expected collocation upon an associated
display.
7. The system according to claim 6, wherein the 2D medical imaging
device is an x-ray device.
8. The system according to claim 6, wherein: said 2D imaging device
is further adapted to capture a series of 2D medical images of the
subject, during the implant procedure; said image processor is
further adapted to derive from each given image of the series, from
the appearances of said features in the given image, a given
spatial relationship between said invasive surgical tool and the
organ and determine for each given image of the series, based on
the derived given spatial relationship, a given expected
collocation of the orthopedic implant in relation to the organ; and
said rendering circuitry is further adapted to render the given
expected collocations in sequence in real time.
9. The system according to claim 6, wherein the image processing
circuitry is further adapted to identify a contour of the organ in
the given 2D medical image.
10. A method for imaging based surgical support in orthopedic
implant procedures, said method comprising: capturing a two
dimensional a 2D image of a subject of a given orthopedic implant
procedure, during the implant procedure, using a (2D) medical
imaging device; using an image processor to identify, in real time,
features of an invasive surgical tool in contact with, or within,
an organ of the subject; using the image processor to derive, from
spatial relationships between the identified features, a spatial
relationship between said invasive surgical tool and the organ;
using the image processor to determine, in real time, based on the
derived spatial relationships, an expected collocation of an
orthopedic implant in relation to the organ; and rendering upon an
associated display the expected collocation, in real time.
11. The method according to claim 10, wherein the medical imaging
device is an x-ray device.
12. The method according to claim 10, further comprising: capturing
a series of 2D medical images of the subject, during the implant
procedure; using the image processor to derive from each given
image of the series, from the appearances of said features in the
given image, a given spatial relationship between said invasive
surgical tool and the organ; determining for each given image of
the series, based on the derived given spatial relationship, a
given expected collocation of the orthopedic implant in relation to
the organ; and rendering upon the associated display the given
expected collocations in sequence in real time.
13. The method according to claim 10, further comprising using the
image processor to identify a contour of the organ in the 2D
medical image.
Description
PRIORITY CLAIMS
[0001] This Application is a continuation of U.S. Utility patent
application Ser. No. 16/662,059, titled "A System For Measuring The
True Dimensions And Orientation Of Objects In A Two Dimensional
Image", filed by the inventors of the present Application on Oct.
24, 2019;
[0002] which in turn, is a continuation of U.S. Utility patent
application Ser. No. 15/256,642, titled "A System For Measuring The
True Dimensions And Orientation Of Objects In A Two Dimensional
Image", filed by the inventors of the present Application on Sep.
5, 2016;
[0003] which, in turn, is a continuation of U.S. Utility patent
application Ser. No. 14/106,771, titled "A System For Measuring The
True Dimensions And Orientation Of Objects In A Two Dimensional
Image", filed by the inventors of the present Application on Dec.
15, 2013;
[0004] which, in turn, is a continuation of U.S. Utility patent
application Ser. No. 12/665,731, titled "System For Measuring The
True Dimensions And Orientation Of Objects In A Two Dimensional
Image", filed by the inventors of the present Application on Jun.
1, 2010;
[0005] which, in turn, is a national phase entry of PCT Application
No. PCT/IL08/00841 titled "A System For Measuring The True
Dimensions And Orientation Of Objects In A Two Dimensional Image",
filed by the inventors of the present Application on Jun. 19,
2008;
[0006] which, in turn, claims priority from Israeli Application
184151 filed by the inventors of the present Application on Jun.
21, 2007.
[0007] Based on the above listed priority chain, priority is hereby
claimed from all of the above listed Applications, all of which are
hereby incorporated by reference into the present Application.
FIELD OF THE INVENTION
[0008] The invention is related to the field of medical
radiography. More specifically the invention relates to devices and
methods of accurately measuring the dimensions in a specific
orientation of objects observable in two-dimensional images, e.g.
radiographic images.
[0009] A portion of the disclosure of this patent document contains
material which is subject to copyright protection. The copyright
owner has no objection to the facsimile reproduction by anyone of
the patent document or the patent disclosure, as it appears in the
Patent and Trademark Office patent file or records, but otherwise
reserves all copyright whatsoever.
BACKGROUND OF THE INVENTION
[0010] The technical problem that is addressed by the present
invention has been known since the earliest application of x-rays
as an aid in medical diagnostics and the performance of medical
procedures. The problem is easily understood with reference to FIG.
1A and FIG. 1B. X-ray source 10 is roughly a point source that
emits a cone of x-rays that project an image 40 of radiopaque
object 20 on surface 30. Surface 30 is in some cases essentially
planar but is usually distorted as a result of the configuration of
the equipment used to make the images. The surface 30 can be of any
type made sensitive to x-rays, e.g. a sheet of glass or plastic or
a thin paper or plastic film coated with a material that fluoresces
when struck by x-rays or coated with a photographic emulsion or an
electronic device whose surface has an array of pixels such as a
CCD device. As can be seen in the Figures, the scale of image 40 on
surface 30 depends on the distance of identical objects 20 from the
source 10 (FIG. 1A) and/or on the angle of the object with
reference to planar surface 30 (FIG. 1B). As a result, the surgeon
cannot accurately measure distances or the size, shape, and
orientation of objects in x-ray images and has to rely on intuition
and experience to determine these parameters. The problem is
especially serious in the case of surgical procedures that must be
carried out using frequent x-ray imagery. In this case accurate
work is limited by the ability of the surgeon to know exact values
of the above mentioned parameters. In the absence of this
information, time consuming trial and error is needed to complete
the procedure and the lack of accurate measurements has been
determined to be one of the causes of failures of orthopedic
procedures.
[0011] As mentioned above, this problem was recognized very early
in the development of the field of medical radiography. In January
1897, only a little over one year after the ground breaking paper
by Roentgen that gave the first scientific explanation of the
phenomenon that he called x-rays, a patent application that
eventually became U.S. Pat. No. 581,540 was filed in the U.S.
Patent Office. The invention comprises a grid of radiopaque wires
placed between the object being x-rayed (inside a human body) and
the planar surface on which the images are recorded and an "angle
plate" which is applied to the body to insure parallelism of the
x-rays. The object of the invention being to provide "an improved
radiographic apparatus whereby the exact location of an invisible
object, not permeable or difficulty permeable by the so-called
"Roentgen" or "X" rays, may be accurately ascertained and
measurements made by which operations necessary for the removal of
such objects are controlled and guided".
[0012] In the intervening years since the publication of U.S. Pat.
No. 581,540 and the present, numerous patents have been granted and
scientific articles published that provide different solutions to
different aspects of the same problem. A brief review of some of
these solutions can be found by reviewing the following patents:
[0013] U.S. Pat. No. 1,396,920 describes an indicator comprising
radiopaque marks on a plane parallel to the object to be observed
and the x-ray sensitive plate. In this way the indicator appears on
the x-ray image and the known distances between the marks can be
used to determine the correct scale of the distances that appear in
the image and thus the size of the object can be accurately
determined. [0014] U.S. Pat. No. 5,970,119 describes a scaling
device comprising an easily observable radiopaque member having
radiolucent gaps spaced a known distance apart. The embodiments of
the scaling device can be use externally or incorporated into a
catheter to allow the device to be manipulated into a position in
the vicinity of the anatomical structure to be measured as close as
possible to the plane of the structure while being oriented as
closely as possible to perpendicular to the x-ray beam. [0015] U.S.
Pat. No. 5,052,035 describes a device comprised of a transparent
substrate on which is created a grid of parallel radiopaque lines.
The film is placed over the area of the body of the patient of
interest and an x-ray image is taken. The grid appears in the x-ray
image as an overlay on the anatomical structure. The transparent
substrate is adapted so that, by use of a marking instrument, marks
can be applied to the body. In this way features that appear in the
x-ray image can be accurately located on/in the body of the
patient. [0016] U.S. Pat. No. 3,706,883 describes an elongated
probe (catheter) that includes at least one radiopaque segment of
known length. The probe is introduced into the body and is brought
into proximity to the object to be measured. The radiopaque portion
of the probe appears on the x-ray image next to the object whose
size is unknown. The ratio of the apparent length of the radiopaque
portion of the probe to its known length provides the scale factor
necessary to determine the length of the other objects that appear
in the x-ray image. [0017] U.S. Pat. No. 4,005,527 describes a
depth gauge comprised of alternating sections of radiopaque and
radiolucent material of known length. The depth gauge can be
inserted into a hole or cavity to be observed using x-ray methods.
The gauge will be seen on the x-ray image and can be used to
provide a scale to measure the depth of the hole and dimensions of
other features seen in the image. In one embodiment, the depth
gauge is the shaft of a drill and serves to enable the surgeon to
know the depth of the hole that he has drilled into a bone.
[0018] This brief survey of the prior art gives an indication of a
fact of life that is well known to surgeons, i.e. that the solution
to the problems first recognized in the earliest days of medical
radiography has not yet been found. Each of the solutions proposed
to date, while it might represent an improvement over prior
proposals or may give adequate results for certain procedures, has
not provided an overall solution.
[0019] A surgeon using any of the previous measurement techniques,
whether involving using a regular ruler to measure objects directly
(not through x-ray) or measuring objects on the image itself will
experience the same limitations. Measuring objects directly is
often problematic since access is limited to the objects measured
and measuring on the image itself, besides requiring a calibration,
can only provide measurements on the projection of the object and
in the projection plane.
[0020] While x-ray images are two dimensional and prior art
techniques allow reasonably accurate two dimensional measurements
in the plane of the image itself, the surgeon would ideally like to
have the ability to make three dimensional measurements and measure
the objects at any direction he desires. In particular orthopedic
surgeons would like to be able to accurately measure objects not in
the image plane and to measure objects, without penetrating them,
while retaining the measurement accuracy.
[0021] It is therefore a purpose of the present invention to
provide a ruler which improves upon and overcomes the limitations
of prior art rulers used for measuring distances in radiographic
images.
[0022] It is another purpose of the present invention to provide a
ruler which allows a surgeon to make three dimensional measurements
and measure objects in a radiographic image at any direction he
desires.
[0023] It is another purpose of the present invention to provide a
ruler which allows a surgeon to accurately measure objects not in
the image plane, while retaining the measurement accuracy.
[0024] It is another purpose of the present invention to provide a
ruler which allows a surgeon to accurately measure objects without
penetrating them, while retaining the measurement accuracy.
[0025] Further purposes and advantages of this invention will
appear as the description proceeds.
SUMMARY OF THE INVENTION
[0026] In a first aspect, the invention is a system for measuring
the true dimensions and orientation of objects in a two dimensional
image. The system is comprised of a ruler comprising at least one
set of features each comprised of two or more markers that are
identifiable in the image and having a known spatial relationship
between them and a software package comprising programs that allow
extension of the ruler and other objects in the two dimensional
image beyond their physical dimensions or shape.
[0027] In embodiments of the invention the markers in each set are
arranged in one or more rows having a known spatial relationship
between them. If there is more than one of the sets, at least some
of the sets are aligned in a direction non-parallel to the
measurement direction or to each other.
[0028] Embodiments of the system are adapted to measuring x-ray
images. Embodiments of the system are adapted to enable it to be
used for measuring the true dimensions and orientation of objects
and for aiding in the identification and location of a surgery tool
vs. anatomy in a radiographic image.
[0029] In a second aspect, the invention is an apparatus adapted to
enable it to take x-ray images and to measure the true dimensions
and orientation of objects and to aid in the identification and
location of a surgery tool vs. anatomy in those x-ray images. The
apparatus comprises: [0030] a. a system comprising one or more
rulers and a software package according to the first aspect of the
invention; [0031] b. radiographic imagery means; [0032] c.
processing means; and [0033] d. display means
[0034] characterized in that the software package comprises
programs that allow the processing means to recognize the features
of the ruler on the radiographic image and to use the features to
create a virtual extension of the at least one ruler and to draw
the virtual extension of the at least one ruler on the radiographic
image as an overlay, thereby enabling the user who is pointing the
at least one ruler and looking at the radiographic image to
accurately measure objects that appear in the radiographic
image.
[0035] In embodiments of the invention the software package
comprises a program that allows the zero scale on the virtual
extension of the ruler to be dragged and moved around at will. In
other embodiments, if a three dimensional ruler is used to
determine a measuring plane and a feature known to be on the
measuring plane, then the software package comprises a program that
allows the processing means to measure the angle between two lines
projected on the measuring plane.
[0036] In embodiments of the invention the software package
comprises a program that allows the processing and display means to
provide real time visualization by using either a one or a three
dimensional ruler in order to draw how at least how a part of the
result of the operation will look given the positioning of the
ruler or some other surgical tool visible in the image.
[0037] In embodiments of the invention the software package
comprises a program that allows the processing and display means to
find markers in the image and place templates of implants or other
objects on the image.
[0038] In embodiments of the invention the software package
comprises a program that allows the processing means to
automatically determine the location of a surgical tool in the
image and to apply an image enhancement algorithm that
automatically concentrates on the specific area of interest to the
surgeon.
[0039] In embodiments of the invention the software package
comprises a program that allows the processing and display means to
synchronize AP and axial images.
[0040] In a third aspect the invention is a ruler for use in the
system of the first and second aspects. The ruler has at least one
set of features each comprised of two or more markers that are
identifiable in the image having a known spatial relationship
between them. In embodiments of the invention the markers in each
set are arranged in one or more rows having a known spatial
relationship between them and, if there is more than one of the
sets, at least some of the sets are aligned in a direction
non-parallel to the measurement direction or to each other.
[0041] The ruler can be a hand-held ruler used to "point and
"measure". The ruler may comprise means for slideably attaching it
to a tool. The ruler may be an integral part of a tool, made by
making at least part of the tool from a translucent material and
embedding opaque markers into it. The ruler may be comprised of
small radiopaque markers, with a known spatial relationship between
them, embedded in a radiolucent envelope.
[0042] In a fourth aspect the invention is a method of drawing and
displaying on a two dimensional x-ray image measurements of objects
visible in said image, graphical information, or templates of
surgical devices. The method comprises the steps of: [0043] a.
identifying the location and orientation of at least one known
object; and [0044] b. drawing and displaying the measurements,
graphical information, or templates on the x-ray image on the basis
of the location and the orientation of the known object.
[0045] The method is characterized in that the measurements,
graphical information, or templates are not a part of the known
object. The known object can be a ruler according to the third
aspect of the invention, a surgical tool, or an anatomical
feature.
[0046] All the above and other characteristics and advantages of
the invention will be further understood through the following
illustrative and non-limitative description of preferred
embodiments thereof, with reference to the appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] FIG. 1A and FIG. 1B illustrate the technical problem that is
addressed by the present invention;
[0048] FIG. 2 shows a compression hip plate assembly;
[0049] FIG. 3 illustrates the tip-apex distance (TAD);
[0050] FIGS. 4, 5A and 5B illustrate two embodiments of one
dimensional rulers of the invention;
[0051] FIG. 6 illustrates an embodiment of a three dimensional
ruler of the invention;
[0052] FIG. 7 and FIG. 8 schematically show respectively how one
and two dimensional virtual extensions of the ruler of the
invention are created overlaying the x-ray image of the object of
interest;
[0053] FIG. 9A to FIG. 9C show a handle comprising a ruler of the
invention to be used by a surgeon to correctly align a drill
guide;
[0054] FIG. 10A to FIG. 15 illustrate some of the modes of
operation of the system of the invention;
[0055] FIG. 16 symbolically shows how the system of the invention
is integrated with an imaging system; and
[0056] FIG. 17 is a flow chart outlining the main stages in
processing and displaying the images using the system of the
invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0057] The invention is a system that can be used for measuring the
true dimensions in a specific orientation of objects in two and
three dimensional images. In order to illustrate the invention and
in preferred embodiments thereof, the images considered herein are
radiographic images, in particular x-ray images, wherein by x-ray
images are meant radiographic images, fluoroscopic images, digital
fluoroscopy images, or images taken using any other type that uses
x-rays to obtain them. However it is to be understood that the
device and methods of the invention can be used in any imaging
situation. In the case of x-ray radiography, the device and system
of the invention are used to measure the true dimensions and
orientation of objects that appear in the image and to aid the
surgeon in the identification and location of surgery tools vs.
anatomy in the radiographic image.
[0058] FIG. 16 symbolically shows how the system of the invention
is integrated with an imaging system to improve the users
understanding of the images produced with the imaging system. The
essential components of imaging system 200 are the source of
radiation 202 and the detector 204. The imaging system 200 is
connected to a computer 206. When an at least partially opaque
object 210 is placed in the space between the source 202 and
detector 204 and system 200 is activated, object 202 blocks some of
the radiation causing a shadow to appear on the detector. The
output signals from detector 204 are sent to computer 206 where
they are processed to produce images that can be stored in the
memory of computer 206 and/or displayed on display device 208.
[0059] The system of the invention comprises two components: a
calibration device 70, which is called a "ruler" herein and a
computer software package 216. Radiolucent ruler 70 comprises
radiopaque markers 76. It is placed in the space between source 202
and detector 204 such that at least some of the markers 76 will be
visible in the images gathered by imaging system 200. Computer
software package 216 is loaded into computer 206 in order to
provide the computer with advanced capabilities for processing and
displaying the images as a graphical overlay, displayed over the
x-ray image on the display 206, thereby providing the user with
information not previously available. Illustrative embodiments of
the ruler and of the software as well as descriptions of the new
types of visual information that can be provided to the user will
be described herein below.
[0060] Herein the word "markers" is used to mean features that are
visible in the image, by virtue of their color, luminance or
intensity. In the case of x-ray images, markers have a different
radio-opacity than their immediate surrounding, or comprise
different radio-opacity levels. Markers are regarded as a singular
point in space, e.g. the center of a ball or a corner of a cubical
shape, which is well defined and can be noticed in the image.
Herein the words "marker" and "feature" are used
interchangeably.
[0061] In one embodiment, the ruler comprises two or more features
having a known spatial relationship between them that are visible
and recognizable in a radiographic image. For the purpose of the
measurement the two or more features are aligned parallel to the
measurement direction. The associated software allows, amongst many
other modes of operation to be described herein, the automatic
recognition of features of the ruler in the radiographic image and
the use of these features to create a virtual extension of the
ruler, i.e. to extend the ruler beyond its physical dimensions, and
drawing the virtual extension on the image as an overlay. The
invention enables the surgeon who is pointing the ruler and looking
at the image to accurately measure dimensions of objects that
appear in the radiographic image. The invention is especially
useful and convenient for use with x-ray imaging in which
frequently it is desired to measure the internal organs, bones,
etc. of a body. However, as mentioned above, in principal the
invention can be used with any technique of producing two
dimensional images, e.g. regular photography.
[0062] All prior art methods known to the inventors use the
physical scales on a ruler to measure the dimensions of or
distances between objects of interest either directly or to take a
picture and make the measurements directly on that picture in two
dimensions. These methods are generally not accurate for the
reasons mentioned hereinabove and do not enable easily measuring
objects in different three dimensional orientations. The approach
taken to the problem of making accurate measurements by the
inventors is fundamentally different than that of the prior art
since it makes use of control of both the tool, i.e. the ruler, and
the display, i.e. the visual image including graphic overlay
thereof. The measurement method is dependent on the combination of
the ruler, which cannot be used to achieve the desired result when
used alone and the software, which cannot, be used to make the
measurements without the ruler. Only through the combination of
ruler and software, as described hereinbelow can the desired result
be obtained.
[0063] The invention, in its various embodiments, can be used to
assist the operator in any procedure in which it is desirable or
necessary to measure distances or dimensions of objects in
radiographic images. Such procedures range from common chest
x-rays, that are analyzed "off-line", to orthopedic and other
surgical procedures that can only be carried out "on-line", i.e.
with the aid of inter-surgery radiographic imagery using, for
example, a mobile C-arm x-ray unit. Typical non-limitative examples
of on-line procedures that can be performed with the aid of the
invention are: [0064] Spinal fusion/lumbar spine
fixation--insertion of pedicle vertebral screws; [0065]
Vertebroplastia--injecting cement to a vertebral body via the
pedicles; [0066] Bone biopsy--inserting a long needle through bone,
to reach a tumor or lesion; [0067] Dynamic hip screw (DHS)
placement procedures for per-trochanteric and intertrochanteric hip
fractures; [0068] Three Cannulated Screws placement procedures for
sub-capital fractures; [0069] Proximal Femur Nail (PFN) placement
procedures for oblique-reversed and for sub-troch hip fractures;
and [0070] Trochanteric fixation nail (TFN) fixation.
[0071] For purposes of illustrating the invention, its use in
relation to dynamic hip screw (DHS) placement procedures for hip
trauma procedure under fluoroscopy will now be described. It is
emphasized that the invention is not limited to use in any
particular procedure and is expected to be useful for a wide range
of applications. According to statistics made available by the
American Association of Orthopaedic Surgeons, about 450,000
procedures for treatment of hip trauma were carried out in 2004.
Nearly 90% of the procedures were carried out on persons aged 65 or
older who had suffered breaks in the proximal end of the femur as a
result of a fall. The surgical procedures for treating the
fractures are well known and documented, including descriptions in
textbooks, scientific journals, and even complete protocols that
can be found on the internet. Generally speaking, depending on the
exact nature of the break, the procedure involves attaching one of
a number of different styles of commercially available compression
hip plates to the femur by means of pins or screws inserted into
holes drilled into the bone. A good review of the state of the art
can be found in "Intertrochanteric Fractures" by Dr. Kenneth J.
Koval and Dr. Robert V. Conto, which is a chapter in the book:
Rockwood and Green's Fractures in Adults; Authors: Robert W.
Bucholz, M D; James D. Heckman, M D; Publisher: Lippincott Williams
& Wilkins; 6th edition, 2005.
[0072] A specific protocol for carrying out the surgical procedure
can be downloaded from the web site of Smith & Nephew at
[http://www.smithnephew.com/Downloads/71180375.pdf]
[0073] FIG. 2 shows a compression hip plate assembly 50
manufactured by Smith & Nephew. The assembly comprises a plate
54 that fits against the outer surface of the femur with an
attached barrel 52 that fits into a hole bored into the femur.
After reduction and fixation of the fracture a hole is bored into
the bone through the neck and into the head of the femur in order
to attach lag screw 56. After lag screw 56 has been screwed into
the head of the femur, the barrel is inserted into the hole, the
plate is positioned on the side of the femur, and compression screw
60 is screwed in to attach the plate 54 to the lag screw and
tightened to bring the broken pieces of bone together. Self tapping
bone screws 58 are used to attach the plate firmly to the shaft of
the femur and if necessary, depending on the type of break,
cannulated or cancellous screw 62 can be inserted into the bone to
capture medial fragments. There are hip plate kits available to the
surgeon having many variations of the basic design. The variations
include, for example, the length of lag screw 56, the angle between
screw 56 and plate 54, and the number of cortical screws 58.
[0074] The most demanding part of the procedure is creating the
hole into which the lag screw is inserted. For a successful
procedure, the hole must pass through the bone in a path following
the central axis of the neck of the femur towards the apex of the
femoral head. The surgeon, assisted by a series of x-ray images
taken during the course of the proceeding, uses a small diameter
guide drill to make an initial guide hole. The first problem is to
determine the neck angle to select an appropriate angle plate,
which is used to help determine the proper entry point and to aim
the guide drill. The surgeon, referring to the x-ray images,
estimates the correct angle and entry point and begins to drill
with the guide drill. After drilling a short distance into the
bone, he stops and takes at least two x-rays at right angles to
each other to ascertain that he is indeed drilling in the correct
direction and along the center of the neck. In order to do this he
must mentally project the image of the drill forward through the
anatomical features, a task that is complicated, especially given
the required precision and the challenging image quality. In
addition, a typical C-arm equipped with an image intensifier tube
for generating the images creates a distortion to the image usually
causing straight lines to appear curved in the images: It is noted
that if the surgeon has only to extend the line from the drill
theoretically he is not influenced by the scale and a line in three
dimensional world will still appear to be a line in the two
dimensional projection image; however this theoretical extension is
not an easy task, especially when precision is so important. If the
drill path appears to be correct, then the surgeon drills a bit
further before stopping to check again by repeated x ray imaging.
If, at any stage, the path appears to be incorrect, then the
surgeon must withdraw the guide drill and begin drilling again
using a different angle and/or entry point. Another difficulty is
ascertaining exactly where to stop drilling. It is essential that
the lag screw be attached to as much of the bone as possible;
however sufficient bone must remain at the apex of the head to
prevent the lag screw from breaking through into the hip joint when
the screw is inserted in the hole. This issue involves not only
measurement of drilling orientation but also of drilling depth.
[0075] A typical procedure of this type carried out by an
experienced surgeon takes a considerable amount of time, most of
which is consumed by trial and error attempts to obtain the proper
alignment. Additionally between 100-150 x-ray images are typically
required, which, despite all precautions, represents a serious
health hazard for both the patient and, to a greater extent, for
the operating room staff that can be present for several similar
operations each day.
[0076] The reason that so much time and care is taken to insure
proper alignment of the guide hole is that failure of fixation of
intertrochanteric fractures that have been treated with a
fixed-angle sliding hip-screw device is frequently related to
incorrect position of the lag screw in the femoral head. To insure
success of the procedure and prevent mechanical failure, i.e. bone
cut-out, an accuracy of .+-.2-3 mm of screw location is crucial. A
simple measurement called the tip-apex distance (TAD) is used to
describe the position of the screw. This measurement is illustrated
in FIG. 3. The dashed lines represent the desired direction of the
lateral axis of the lag screw in the radiographic images. X.sub.ap
and D.sub.ap mark the distances from the tip of the lag screw to
the apex of the femoral head and the measured diameter of the lag
screw measured on an anteroposterior (AP) radiograph, respectively.
X.sub.lat and D.sub.lat mark the same parameters measured on a
lateral radiograph, and D.sub.true is the actual diameter of the
lag screw. Then the TAD is given by the formula:
TAD=(X.sub.ap.times.D.sub.true/D.sub.ap)+(X.sub.lat.times.D.sub.true/D.s-
ub.lat)
[0077] The results of many studies show that the failure rate
approaches zero if the TAD is less than 25 mm and the chances of
failure increase rapidly as the TAD increases above 25 mm [M R
Baumgaertner, S L Curtin, D M Lindskog and J M Keggi, "The value of
the tip-apex distance in predicting failure of fixation of
peritrochanteric fractures of the hip", The Journal of Bone and
Joint Surgery, Vol 77, Issue 7, 1058-1064, 1995]. Using present
techniques, the DHS can only be determined after the procedure has
been completed. Using the present invention the surgeon will be
able to estimate the DHS at the preplanning stage before beginning
to drill the guide hole and will be able to know the expected value
at any stage of the procedure.
[0078] FIGS. 4, 5A, and 5B illustrate two embodiments of a
one-dimensional ruler of the invention. In the embodiment shown in
FIG. 4, ruler 70 is comprised of a cylinder 72 of radiolucent
material. A slot 74 is created lengthwise in cylinder 72 so that
the ruler can be slipped over the surgical tool, e.g. a guide, i.e.
a thin bone drill sometimes known as a guide wire, without the
necessity of releasing the guide from the power drill. The
dimensions of the slot are such that the longitudinal axis of the
guide and cylinder 72 coincide when ruler 70 is attached to the
guide. The guide fits tightly in the slot so that the ruler will
not slide freely but can be shifted easily by the surgeon to a new
position when desired. Some embodiments of the ruler will rotate
with the guide and other embodiments of the ruler can be attached
so that the guide may rotate without rotating the attached ruler.
Metal balls 76 are embedded into cylinder 72 in rows that are
parallel to the direction of slot 74. Metal balls "floating" in a
plastic cylinder are preferably used so that the x-ray signature of
the ruler will be dark circles that are easily detectable in the
image. One row of balls 76 is theoretically sufficient; however it
is preferred that at least three rows of balls 76, equally radially
spaced around the circumference of the base of cylinder 72, be used
to insure that at any position of the ruler on the guide at least
one row of balls will not be overlaid by the radiopaque guide or
another row of balls, and will be visible on the x-ray image.
[0079] The exact distance between balls 76 is known so that when
their shadows are detected on the x-ray image the dedicated
software of the invention can identify them and measure the
apparent distance between them directly from the image and use this
measurement together with the known actual distance to calculate
the scale that is used to create the overlays that allow the
surgeon to determine the exact position of the guide relative to
the anatomical structure, dimensions, and other related information
displayed on a screen in "real time". As a minimum, only two balls
76 in one row are needed to be visible in the image in order to
create an acceptable approximation of the C-arm magnification
factor and the sizes of organs and tools for most common cases.
However, since increased accuracy is obtainable by using the
averages of several apparent measurements and also since some balls
may be hard to see in the image it is preferred to use a minimum of
three or four balls in each row to get a more accurate mathematical
extension of the ruler. Also, if the angle between the ruler and
the image plane is large, the scale change along the ruler
extension, in the image, is not negligible. It is therefore
preferred to use more than one measurement, at different heights,
so that an approximation of this effect can be calculated.
[0080] Another way of explaining the problem of crating an accurate
scale for the images and the solution to the problem is the
following: It is known that the magnification increases linearly
with the distance from the x-ray source. Therefore, if there are
only two markers, the distance between them can be measured,
however, it is impossible to determine if this distance is accurate
because the ruler may not lie in a plane parallel to the image.
Therefore, the measured distance between markers can not be counted
on to provide an accurate scale for creating virtual extensions,
overlays and other advanced features provided by the present
invention. To overcome this problem a ruler with several markers,
having a known distance between them, is used. If the ruler is
parallel to the image plane, then the scale is correct and a true
2D calibration is obtained. If, however, the ruler is not parallel
to the image plane, the distance between markers, i.e. the scale,
will grow smaller to one direction and larger in the other
direction, changing with the distance from the x-ray source. In
this case, if there are three markers or more, not only the
distance between markers but also the rate of change of the
distance can be measured and therefore an accurate scale in both
directions can be calculated.
[0081] FIG. 5A shows another embodiment of a ruler 70' of the
invention. In this embodiment the radiolucent body 80 of the ruler
is roughly a prism having an isosceles triangle as its base. The
sides of the prism are cut away to leave a Y-shaped cross section.
A row of metal balls 76 (seen in FIG. 5B, which is a
cross-sectional view of ruler 70') is embedded at the apex of each
of the arms of the "Y". A slot 74 is created along the longitudinal
symmetry axis of body 80 of ruler 70'. Body 80 is slipped over
guide 78 and then a clip 82 is attached to body 80 to hold guide 78
in slot 74. This can be done with the guide attached to the drill.
In this embodiment the width of slot 74 need not necessarily be
essentially equal to the diameter of the guide but it can be wide
enough to allow the ruler to be attached to guides having a wide
range of diameters. Clip 82 comprises a spring loaded brake (not
shown) that locks ruler 70' in place, preventing it from sliding
along guide 78. Pressing downward on clip 82 in the direction of
arrow 84 releases the brake allowing ruler 70' to be moved and
repositioned along the guide. Repositioning can be easily
accomplished by the surgeon using one hand, at any time during the
procedure.
[0082] FIG. 6 illustrates an embodiment of a three dimensional
ruler 70'' of the invention. In this embodiment the radiolucent
body 86 of the ruler has an "L" shaped cross section. Rows of
radiopaque balls 76 are embedded in the walls of body 86. A
suitable arrangement, e.g. a slit and/or a clip such as described
above, are provided to slidingly hold ruler 70'' in place on guide
78.
[0083] Many different arrangements of markers are described herein
with regard to specific illustrative examples of the ruler. In
principal the minimal requirement of the invention for the number
and arrangement of markers is one of the following: [0084] Two
markers aligned in the direction of the measurement--This will
enable determining a scale with not very good accuracy because of
the other degree of freedom described herein above. [0085] Three
markers aligned in the direction of measurement--This will enable
higher accuracy. [0086] A set of at least three markers, not on the
same line, is sufficient in order to create an accurate three
dimensional orientation and thereby enable measurement of an object
in every orientation. [0087] In all cases, the markers do not have
to be equally spaced but must be in a known spatial arrangement.
[0088] In the figures herein several rows of equally spaced markers
have been included so that they will not occlude each other and
therefore allow a better chance of detecting them. There is,
however, no minimal requirement of the number of rows of markers
that must be used.
[0089] In another embodiment, the triangular sleeve with handle
that is used by orthopedic surgeons to aid them in maintaining the
alignment of the drill in a DHS placement procedure, as known to
persons skilled in the art, can be modified by embedding a three
dimensional ruler of the invention inside it, in which case, the
modified sleeve itself can be used to fulfill the functions of the
ruler of the invention that are described herein. The sleeve is
made of radiolucent material and comprises a set of metal balls,
arranged in a known spatial arrangement, such that the 3D
orientation of the ruler may be calculated using the balls that
appear in the image.
[0090] FIG. 9A to FIG. 9C respectively show front and back
perspective views and a cross-sectional view of a handle 90
comprising a ruler of the invention that can replace the
traditional triangular sleeve used by surgeons to aid in aligning a
guide drill. As seen in the Figures, handle 90 has a "T" shape with
a crosspiece 92 at the top of shaft 93 that allows the user to
easily and firmly grip handle 90 with one hand. At the bottom of
shaft 93 is a foot 94. The bottom surface of foot 94 comprises
means, e.g. cleats 96, to prevent the device from sliding on the
surface of the skin. In FIG. 9B the exit hole 98 of slot 74 (FIG.
9C) through which the guide drill passes can be seen on the bottom
of foot 94. At least the foot 94 and the lower portion of shaft 93
(through which slot 74 passes) of handle 90 are made of a
radiolucent material. In the illustrative example shown, embedded
in this material are two rows comprised of five of radiopaque
markers 76 each, a horizontal row embedded in the foot 94 and a
vertical row embedded in the lower part of shaft 93. Notice that
the markers in each row are not equally spaced and that neither of
the rows of markers is aligned in parallel to the direction of the
drilling. However, the software of the system can identify the
markers 76 and from them determine the location and orientation of
the handle 90, from this the exact orientation of slot 74, and can
create a virtual extension of the guide that is inserted into slot
74, in the direction of drilling, beyond its physical dimension.
Using this handle, a ruler need not be attached to the drill and
the system of the invention will recognize the handle and can
extrapolate it in both directions and can also display the implant
template, i.e., a graphic overlay of where the implant would be,
including all its parts, at the current position of the triangle
(see, for example, FIG. 14 and FIG. 15). This approach allows an
"intra-operative real time" visualization and measurement ability
using the tools that are familiar to the surgeon.
[0091] In accordance with the discussion herein above, preferred
embodiments of three dimensional rulers can be constructed
comprising two sets of non-parallel rows of markers in order to
provide a device for which the markers will be identified even when
the ruler is partially occluded by other objects, e.g. bones or
tools in the image. Using such a ruler, a three dimensional grid
can be projected onto the image.
[0092] As discussed hereinabove, embodiments of the ruler of the
invention comprise an elongated radiolucent body in which rows of
radiopaque markers of known size and distance apart are
symmetrically embedded. In its different embodiments, the ruler of
the invention can be: a hand-held ruler used to "point: and
"measure"; the ruler can comprise means for slideably attaching it
to a surgical tool, e.g. handle 90 shown in FIGS. 9A to 9C; or the
ruler can be an integral part of a surgical tool, possibly made by
making at least part of the tool from a translucent material and
embedding radiopaque markers into it. The ruler can be a one
dimensional ruler in which the rows of radiopaque markers are
parallel to the measuring direction or a three dimensional ruler in
which a non parallel rows of markers are embedded. In some
embodiments the ruler could comprise a metal comb or a metal jig,
with no translucent material. The radiopaque markers would then be
either characteristic features of the ruler, e.g. the teeth of the
comb, or could be, e.g. metal balls attached to the body of the
ruler.
[0093] Generally, when the ruler is attached to a surgical tool as
will be demonstrated by example hereinbelow, during a medical
procedure the ruler stays in a fixed position, e.g. at a location
on the surface of the body or an organ within the body of a
patient, while the tool is advanced into or withdrawn from the body
or organ during the course of a diagnostic or surgical
procedure.
[0094] In some preferred embodiments the ruler is made of
bio-compatible USP class 6 materials and is reusable after
sterilization using, for example, ETO. In a preferred embodiment,
the entire ruler, except for the metal balls, is made of plastic.
Under x-ray the ruler is seen as semi transparent and the metal
balls are seen "floating" around the guide/drill. Based on these
fundamentals and the examples of the embodiments described herein,
skilled persons should have no trouble designing a ruler suitable
for use with any diagnostic or surgical tool.
[0095] FIG. 7 and FIG. 8 schematically show respectively how one
and two dimensional virtual extensions of the ruler of the
invention are created overlaying the x-ray image of the object of
interest. In FIG. 7, object 20 and radiopaque balls 76 embedded in
a ruler of the invention, that is attached to guide drill 78, are
shown positioned in the path of a beam of x-rays emitted by source
10. The dashed lines represent the shadows of the radiopaque
objects that form images 40 on the electronic camera. The digital
signals from the camera are processed using the software package of
the invention to determine the distance between the images of the
balls of the ruler. From the measured and known distances a scale
factor is determined and a virtual extension 88 of the ruler is
constructed. The virtual extension can be added as an overlay on
the displayed x-ray image in a number of ways that can be selected
by the operator. In the case of the orthopedic procedures described
herein, the suggested display mode is to place the graphic
presentation of the virtual extension exactly on top of the
longitudinal axis of the guide drill with the origin at the distal
tip of the drill, as seen in the x ray image. This is shown in FIG.
7 on the image plane representing the displayed image in the actual
system. In this way, the surgeon can, using both forward distance
scales and rearward distance scales, determine respectively how
much farther the drill must be advanced and how far into the object
the drill has penetrated.
[0096] Other display features are possible, e.g. color coding to
easily distinguish between forward and rearward distances, the
addition of transverse scales at locations selected by the operator
to enable measurement of the distance from the center of the drill
to the sides of the object for example to confirm that the hole is
being drilled exactly through the center of the object, and the
addition of color coded markings to indicate when the drill is
approaching and/or has arrived at the location that drilling should
cease.
[0097] FIG. 8 is similar to FIG. 7 with the exception that use of
the three dimensional ruler provides sufficient information for the
software to construct a two dimensional grid that can be displayed
on the screen as an overlay on top of the x-ray image. In fact,
since the three dimensional ruler can provide a complete three
dimensional orientation, the grid could be drawn in any
orientation, and not just the original orientation of the ruler (as
shown in the Figure).
[0098] The system of the invention is used with a C-arm X-ray unit
or some other imaging system. It comprises a ruler, and software
that enables display of the virtual extension and allows display of
the overlays and other features described herein, e.g. the software
may include computer vision and recognition algorithms that are
used to identify implants, surgical tools and anatomical features
and to draw their counterparts or extensions during the operation
as an overlay on the x-ray image (see FIG. 11). In some
embodiments, the software works in semi-automatic mode wherein it
allows the user to mark on the balls on the computer screen, e.g.
by pointing to and clicking on them using a computer mouse, and
then calculates the scale and draws the virtual extension. In other
embodiments it is not necessary to mark all or some of the balls in
an image or to mark the balls in successive images. The process may
be started with a user click and then the software automatically
searches for the markers and for the guide in the next image.
[0099] Skilled persons will recognize that the system can be given
the ability to display the images in many different formats to
assist the surgeon, e.g. different colors can be used to
differentiate how far the drill has penetrated into the bone from
the remaining distance. In addition, other types of information,
can be provided by audible signal, e.g. signifying the remaining
distance or when to stop drilling.
[0100] In addition, for imaging systems equipped with an image
intensifier, some embodiments provide an anti-distortion system for
extra accuracy. The anti-distortion system is a conventional one,
as known to persons skilled in the art, comprises a grid placed on
the image intensifier (the receiving end of the C-arm) and software
that uses the image of the grid to correct the image obtained from
the C-arm. Anti-distortion systems suitable for use with the
present invention are described in: [Gronenschild E., "Correction
for geometric image distortion in the x-ray imaging chain: local
technique versus global technique" Med Phys. 1999, December;
26(12):2602-16]. In cases in which an anti-distortion system is
used, the detection of the ruler markers using the software of the
present invention has to be done on the image after the
anti-distortion process.
[0101] FIG. 17 is a flow chart outlining the main stages in
processing and displaying the images using the system of the
invention. In the first stage, 501, the x-ray image obtained using
the imaging system 200 (see FIG. 16) undergoes an image distortion
process. This phase is not mandatory, and depends on the imaging
system. Some imaging systems do not create significant distortions
and for these systems this phase can be skipped. Image distortion
correction is done in any one of the standard ways, known in the
art.
[0102] The next stage 502 is marker identification in the image.
The marker, identification can be done either manually, where the
user points at the location of the markers using a pointing device,
such as a computer mouse; can be done in a semi-automatic manner,
where some user input is required and some of the marker
identification is done automatically; or can be done in a fully
automatic manner, where an image processing algorithm, provided in
the software of the system, is used to detect the markers in the
image.
[0103] In the next stage 503, the software of the system calculates
the scale, using the markers in the image identified in stage 502.
If a one dimensional ruler has been used, then the markers are
co-linear and the only scale that can be deduced is in the
direction of the markers. Since the magnification of an object
depends on its distance from the x-ray source, if only two markers
are used, the exact position and orientation of the ruler cannot be
determined, since a rotation of the ruler may have the same effect,
as a change of distance from the x-ray source, on the distance
between the markers on the image (see FIGS. 1A and 1B). Since the
orientation of the object is not determined, ruler extrapolation
cannot be achieved with high accuracy because, if the measurement
direction is at an acute angle to the x-rays, scaling changes
rapidly along the direction of measurement. In order to be able to
extrapolate the ruler accurately, it is necessary to have at least
three markers on the line, in which case the scale as well as the
orientation of the measurement direction can be calculated with
respect to the x-ray image, since the scale linearly increases with
the distance from the x-ray source. If the user is willing to
ignore this magnification problem, a less accurate approximation
may be obtained using only two markers.
[0104] When using a three dimensional ruler objects can be measured
at any orientation. The minimal requirement in the three
dimensional case is at least 3 markers that are not co-linear.
[0105] In the next step 504 the system draws an overlay over the
x-ray image. The overlay may include any type of graphical or other
information, drawn or printed over the image. Amongst other things,
it may include a virtual extension of a drill, an implant image,
taken from a pre-stored library of implants, or a virtual drawing
of a measurement ruler, aligned with the device. The overlay can
make use of the location and orientation of the device in the
image. Preferred embodiments may include a GUI that enables the
user to easily select and customize the overlay shown over the
images.
[0106] The use of the invention and its advantages will now be
demonstrated with reference a dynamic hip screw (DHS) placement
procedure. The entire procedure is carried out in the operating
room with the aid of a C-arm x-ray system. After completing the
fracture reduction the surgeon begins the pre-operative planning.
This stage is carried out before sterilization and cutting the skin
to expose the bone. The common practice is to take one image from
approximately an anterior/posterior (AP) angle, and do the entire
operation planning on a single image while ignoring the three
dimensional aspects of the bone. Since embodiments of the invention
can be used to identify the surgeon's tools and draw their virtual
extension, e.g. the track that a drill will follow, such
embodiments can be used during the planning stage. The surgeon can
attach a ruler, e.g. ruler 70 (FIG. 4) to the distal end of the
guide drill or slide the guide drill into the slot of a handle,
e.g. handle 90 (FIG. 9A), place the distal end of the guide drill
against the outside surface of the skin, and point the guide in the
direction he wishes to drill. The software of the system will then
draw the virtual extension of the ruler and overlay it on the x-ray
image thereby helping the surgeon to optimize the determination of
penetration point and drilling angle and measure how deep he should
drill. In some embodiments the software package of the invention
enables the surgeon to apply templates of the tools and lag screws
of different dimensions and to determine accurate measurements of
the anatomical features to plan exactly the operation, including
screw selection, and to visualize the end result. FIG. 15 shows
this feature of the operation planning stage.
[0107] FIG. 12 shows the display during operation, after the skin
was already cut and some of the surgical tools were inserted to the
body. The drill 78 is about to enter the femur and the surgeon uses
a triangular sleeve to enter at the correct angle (135 degrees). On
top of this image a two dimensional grid has been drawn to
illustrate how the ruler of the invention and its virtual extension
104 would appear.
[0108] FIG. 13 shows the situation after drilling with the guide
drill 78. The virtual ruler 104 displayed on the screen overlaying
the guide and the bone allows the surgeon to see exactly how far
the drill has penetrated the bone and to confirm that the path is
correct. In order to achieve maximum accuracy a three dimensional
ruler is used to determine the plane on which to draw the line
perpendicular to the drilling direction, i.e. to correct for the
change of scale of the ruler on the drill caused by the fact that
the drill is tilted at an angle relative to the plane of the image.
In most cases a one dimensional ruler could be just as useful; but
in either case, the surgeon can see how far the guide tip is from
the hip joint. This is useful for determining the expected distance
from the joint. Note that this is not exactly the tip apex
distance, but rather a more accurate 3D measurement, that is
similar in concept to the TAD.
[0109] After the screw has been installed in the bone, the virtual
ruler allows the surgeon to accurately measure the tip-apex
distance and verify that the surgery has been performed
properly.
[0110] As is apparent from the description hereinabove, embodiments
of the invention are very versatile when applied to orthopedic
surgery and the software package may have the capability of
allowing the operator to choose from many different operating
modes, depending on the requirements or stage of the procedure. A
list of some prominent modes of operation, some of which are shown
schematically in FIG. 10A to FIG. 15, will now be presented:
[0111] 1. Virtual extension of a tool or object in an image--This
mode of operation can be carried out by the system of the invention
using an image recognition program included in the software package
without the use of the ruler or any other sensors. FIG. 10A is a
drawing showing the guide drill 78 brought close to the femur 100.
FIG. 10B shows guide 78 in contact with femur 100. The software of
the system of the invention, at a command from the operator,
recognizes the guide in the x-ray image and draws its virtual
extension (thin line 102) through the bone. This allows the surgeon
to easily see the path that the drill will follow through the bone
and correct it, if necessary, before starting to drill.
[0112] 2. Virtual extension of the ruler--The pointing aspect of
the ruler of the invention is essentially different from image
calibration or normal rulers. The system extends the ruler so that
the operator only needs to look at the image, which also shows the
ruler, and to point the ruler in the direction he wants to measure
in order to get the measurement. The zero scale on the ruler of the
virtual extension can be dragged and moved around on the image at
will, thereby making it easy for the operator to make any
measurement that he feels is necessary. Note that in prior art
calibration techniques the points the operator wishes to measure
must be marked on the image and the calibration device moved to
measure between the points.
[0113] The pointing aspect is especially important in measuring
objects in live video since in this case the operator can't take
the time to mark the points of interest. An example of such a
measurement is to measure the size of the heart under x-ray while
injecting a contrast liquid to the blood.
[0114] FIG. 11 shows how a surgeon would use the virtual extension
104 of a one dimensional ruler 76, mounted on a guide 78, to
measure how deep he wants to drill. FIG. 12 shows how a surgeon
would use the virtual extension of a three dimensional ruler 76,
mounted on a guide 78, to measure the distance from the insertion
point of the drill, in the direction of drilling.
[0115] 3. Using one or three-dimensional rulers to project accurate
grids on the image. FIG. 13 shows how a surgeon would use the
virtual extension 104 of a three dimensional ruler 76, mounted on a
guide 78, to measure the distance from the hip joint, both in the
direction of drilling, and in the direction perpendicular to it.
This is not exactly the tip-apex distance, but a more accurate 3D
measurement that was not possible in the prior art, and is similar
to the TAD.
[0116] 4. Projecting approximate grids on the image. For example,
working with a one dimensional ruler the software simply assumes
that the other axes have a similar scale.
[0117] 5. Real time visualization--This has two aspects: Use either
a one or a three dimensional ruler in order to draw how the result
of the operation (or part of it) will look given the positioning of
the ruler or some other surgical tool. For example, if it is
decided to drill in a particular direction, the system of the
invention can show how the DHS will be positioned. The other
aspect, based on mode 1, is to simply use an approximate
dimensional scale based on the known or approximate dimensions of
the objects seen in the image to create the grids. This may be
inaccurate and spatially wrong, but can sometimes be good enough.
For example, it is enough to see a guide drill in the image to know
the approximate scale of the image and draw the DHS screw or the
entire DHS implant around it.
[0118] Real time visualization takes place after the planning
stage, during the actual procedure itself. FIG. 14 illustrates this
mode of operation. After fracture reduction the surgeon cuts the
skin and brings the tip of the guide drill 78 into contact with the
bone. He then takes an x-ray image and asks the system of the
invention to draw a virtual extension 102 of the guide on the
image. As a result of the pre-operation planning step (described
herein below) he knows which DHS assembly to use. He now requests
that the system of the invention retrieve the template 106 of the
selected DHS assembly and draw it around the extension 102 of the
guide 78. Note that in FIG. 14, the guide has been deliberately
placed in a wrong direction of drilling and a wrong entry point in
order to demonstrate how drawing the template on the guide can be
helpful for the surgeon, i.e. having the template drawn on the
image makes it very easy for the surgeon to see that he/she is/or
is not drilling in the right place/direction.
[0119] 6. Pre-operative planning--FIG. 15 illustrates this mode of
operation. This mode is carried out on an image taken after the
fracture reduction, using a calibration and a template library.
Here the surgeon chooses different templates and has them drawn,
i.e. overlaid, on the image of the bone to determine exactly which
DHS assembly has the proper parameters to use with the specific
bone and how to place it. Note that this is very different from the
instant visualization, although sometimes the images look similar.
Also, although operation planning is not new, the inventors are not
aware of any other computerized system that enables the planning to
be done inside the operating room. In trauma cases, the planning
has to be done in the operating room since only after fracture
reduction can the operation be planned.
[0120] 7. Image enhancement--The processing means of the system
automatically determines the location of the guide in the image,
therefore an image enhancement algorithm can be applied that
automatically concentrates on the specific area of interest to the
surgeon.
[0121] 8. Synchronizing AP/axial images--This is one of the most
demanding tasks facing surgeons performing surgical procedures
under guidance of a c-arm system. Consider a dynamic hip screw
(DHS) placement procedure and suppose that the surgeon, using the
system of the invention, first takes an image I from an axial
angle, with a ruler on a guide. Then, without moving the guide, he
takes another image J from AP angle. If afterwards he drills a bit
more and then takes a third image K, also from an AP angle, then
the system can calculate how deep the drill got in image I. This is
only possible since the ruler is visible on all the images I, J,
and K and is done by measuring the true distance of drilling
between J and K, and virtually extending the drill by that distance
in image I.
[0122] This is a very important feature that can save the surgeon
the difficulty of going back to the axial angle and taking another
image. This means less radiation and less operating time, and
instant feedback.
[0123] It is to be noted that in certain applications the known
shape and dimensions of surgical tools or even anatomical features
that are visible in the x-ray image can be used in place of a
ruler. In these cases the methods described above can be used to
produce the same visual effects described hereinabove; e.g. virtual
extension of the tool or placement of a template on a bone.
[0124] Although embodiments of the invention have been described by
way of illustration, it will be understood that the invention may
be carried out with many variations, modifications, and
adaptations, without exceeding the scope of the claims.
* * * * *
References