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Description  |
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Background of the Invention
This invention relates generally to imaging systems, and more particularly,
to a system for forming a coordinate system in an image whereby the
location and orientation of an image plane, with respect to certain
anatomical features, can be determined and reproduced for subsequent
imaging using the same or various other types of imaging modalities,
thereby facilitating localization of other anatomical features during
imaging.
Imaging machines are now commonplace in the nuclear medicine departments of
many hospitals, as well as in medical research facilities. As is known,
the images produced by such machines appear as a slice through a portion
of the body being imaged. It is, however, a problem with such imaging
systems that it is extremely difficult to reproduce a particular image.
That is, after taking a first set of images, it is difficult at a later
time to adjust the location of the patient or of the equipment to take a
subsequent image in the same image plane as a prior image. Of course, one
approach to this problem is simply to take a multiplicity of images of a
given region of a body, but even this approach will not solve the problem
since this approach generally would rely on axial displacement of the
images with respect to the anatomical region being imaged, but would not
take into consideration the many possible variations in angular
orientation of the image plane. Moreover, this approach is not feasible
when attempting to reproduce an image plane using different imaging
modalities, particularly in view of the fact that different equipment is
used for the different modalities, resulting in different slice
thicknesses and appearance. The strikingly different appearance of the
images resulting from the different modalities, as well as other
differences, render a visual effort at matching an image plane highly
impractical.
One prior art attempt at achieving the benefits of the present invention
includes the placement of radioactive markers at selected positions in the
body to be imaged. However, the position of such markers is not
reproducible, and cannot be used in different imagers. There is a need for
a system which affords reproducibility of position, is noninvasive, and
can be used for a variety of imagers.
The difficulties in the present state of the art regarding reproducibility
of an image plane are particularly acute in cerebral imaging. There is a
need for a coordinate system for the localization of neuroanatomical
features of cerebral images, and to provide anatomic images which
correspond to prior functional images. Additionally, it is especially
desirable to correlate images resulting from different imaging modalities.
For example, it is highly desirable to correlate functional PET or SPECT
images with MRI or CT images. Such images, with their distinct
appearances, cannot be correlated visually. Accordingly, there is a need
for a system which permits reproducibility of image planes, within a few
millimeters in the x, y, and z directions.
It is, therefore, an object of this invention to provide a simple and
economical system for defining the location and orientation of image
planes in various types of imaging systems.
It is another object of this invention to provide an apparatus for
reproducibly positioning an image plane definition system with respect to
a living being.
It is also an object of this invention to provide a system for defining an
image plane which can be employed in different imaging modalities.
It is a further object of this invention to a system to facilitate
reproducibility of image planes, within a few millimeters in the x, y, and
z directions, with reference to external anatomical landmark features on
the skull and face.
It is additionally an object of this invention to provide a system which
provides reproducibility of image planes for multiple tomographic
modalities, such as CT, MRI, PET, and SPECT.
It is yet a further object of this invention to provide a coordinate system
for defining an image plane and which does not cause discomfort to the
patient when applied.
It is also another object of this invention to provide a coordinate system
for a patient which will remain in place, on the patient, for an
indefinite period of time.
It is yet an additional object of this invention to provide a system which
affords reproducibility of images to within 1-`millimeters.
It is still another object of this invention to provide a noninvasive
system for correlating image planes.
Summary of the Invention
The foregoing and other objects are achieved by this invention which
provides an apparatus for defining an image plane of an image through a
selected portion of the body of a being. In accordance with the invention,
the apparatus is provided with a plurality of elongated channel sections
for containing a material, preferably in the form of a fluid, which is
visible in the image. A first carrier supports a first predetermined
number of the elongated channel sections in respective orientations
transverse to the image plane and in predetermined space relation with
respect to one another. Also, a second carrier supports a second
predetermined number of the elongated channel sections, also in respective
orientations transverse to the image plane and in predetermined space
relation with respect to one another. A support is provided for
maintaining the first and second carriers in fixed spatial relation to one
another and to the body of the being.
In a specific illustrative embodiment of the invention, the selected
portion of the body of the being which is desired to be imaged is the head
of the being. In this embodiment, the support means is provided with an
ear coupling arrangement, illustratively in the form of an ear plug, for
coupling the support arrangement to the ear of the being. This embodiment
may also include a slot which is cut into the anterior portion of the base
of the triangles which is placed directly over the lateral canthus. The
slot and ear coupling arrangement ensures that the carriers are placed
reproducibly on the head of a human being with respect to the bony
anatomical landmarks, i.e., the lateral canthus and external acoustic
meatus. In this manner, reproducibility of subsequent images is achieved
by reference to the bony and other features of the head and face.
The first carrier is provided with first and second carrier portions for
supporting respective ones of the plurality of elongated channel sections
therealong, the first and second carrier portions being coupled to one
another at respective first ends thereof, and to a base member at
respective second ends. The first and second carrier portions and the base
member are arranged, in the specific embodiment, to form a triangle. In
addition, there is provided a third carrier portion arranged substantially
to bisect the triangle. In an embodiment of the invention where the being
is a human being, the ear coupling arrangement is coupled to the base
member. With the aid of the ear coupling arrangement, the base member of a
specific illustrative embodiment of the invention is situated on the head
of the human being so as to be substantially parallel with the
canthomeatal line.
In one embodiment, the elongated channel sections are coupled to one
another to form a continuous channel having an input for receiving an
imaging-opaque fluid, and an output for eliminating same. In such an
embodiment, the elongated channel sections correspond to portions of a
continuous length of flexible tubing.
In accordance with a further specific illustrative apparatus embodiment of
the invention which is specifically for use in imaging the head of a human
being, an elongated flexible channel is provided for containing an
imaging-opaque fluid which is visible in the image. First and second
carriers are each provided for supporting three respective portions of the
elongated flexible channel at respective orientations transverse to the
image plane and in predetermined space relation with respect to one
another. A support arrangement maintains the first and second carriers in
fixed spatial relation to one another and to the head of the human being.
In a further embodiment, the portions of the elongated flexible channel
supported by each of the carriers are each substantially straight. Of
course, other predeterminable contours or curves can be used in the
practice of the invention. In the straight embodiment, however, the
portions of the elongated flexible channel supported by the carriers are
arranged substantially as legs of a triangle.
The present invention can be used in any of several known imaging
modalities. For example, in embodiments where the image is to be obtained
via PET, the image-opaque fluid contained in the channel may be a solution
of .sup.18 F contrast material. If the image is to be obtained via MRI,
the image-opaque fluid can be a solution of Ni contrast material. When the
image is to be obtained via CT, the image-opaque fluid can be a solution
of I contrast material.
In accordance with a method aspect of the invention, a plurality of
elongated channel members having an imaging-opaque characteristic in the
vicinity of the selected portion of the body, are place in an orientation
transverse to the image plane, and in predetermined space relationship to
one another, whereby a distance between the elongated channel members
varies in response to position of the image plane along the elongated
channel members. The method further includes the steps of forming the
image to include therein images of the cross-sections of the elongated
channel members, and determining a location of the image plane of the
image in response to the distance between the images of the cross-sections
of the elongated channel members.
In one method embodiment of the invention, the step of determining includes
the step of determining distances between the images of the cross-sections
of the elongated channel members. Moreover, this step can include, in some
embodiments, the step of determining a ratio of distances between selected
ones of the images of the cross-sections of the elongated channel members.
The determination of distances and ratios of distances can be performed by
computer analysis.
BRIEF DESCRIPTION OF THE DRAWING
Comprehension of the invention is facilitated by reading the following
detailed description, in conjunction with the annexed drawing, in which:
FIG. 1 is an isometric representation of a specific illustrative embodiment
of the invention for use in imaging the head of a human being;
FIG. 2 is a schematic representation of the embodiment of FIG. 1 installed
on the head of a human being;
FIG. 3 is a schematic representation of the embodiment of FIG. 1 as
correlated to the anatomy of the brain of a human being;
FIGS. 4 and 5 are schematic representations showing the effect of axial
translation of the image plane on the resulting image;
FIGS. 6 and 7 are schematic representations of the effect of angular
rotation of the image plane on the resulting image; and
FIGS. 8 and 9 are schematic representations of alternative embodiments of
the invention.
DETAILED DESCRIPTION
FIG. 1 is an isometric representation of a coordinate system 10 which is
intended for use in the imaging of the head of a human being. As shown
coordinate system 10 is provided with two triangular sections, 11 and 12.
Referring to triangular section 11, two legs, 14 and 15 of a substantially
isosceles triangle are coupled to one another at coupling point 16, and to
a base member 17. In addition, there is provided a third leg 18 which is
coupled to coupling point 16 and base member 17.
Triangular section 12 is structured similar to triangular section 11. This
triangular section is provided with two legs, 23 and 24, which are coupled
to one another at a coupling point 55, to form a further, substantially
isosceles triangle. Triangular section 12 is further provided with a
corresponding third leg 56 which is coupled to coupling point 55, and to
corresponding base member 29. In addition, each of the base members, in
this specific illustrative embodiment, is provided with an ear plug 19 for
coupling with the ear of the human. In an advantageous embodiment, slots
27 and 28 are cut into the anterior portions of base members 17 and 29,
respectively. A thin, transparent film 50 is received within slots 27 and
28. Film 50 has centerline 51 printed thereon. Centerline 51 is positioned
over the corner of the eye, or the lateral canthus, of the human subject.
Triangular sections 11 and 12 are coupled to one another by a head strap
20, a first elastic strap 21, and an elastic chin strap 22. These straps
are used for mounting the coordinate system on the head of the human
being, and securing same in a manner which affords reproducibility of the
position to within 1-2 millimeters.
Coordinate system 10 is further provided with an elongated flexible tubing
25, which is shown to be arranged along legs 14, 15 and 18 of triangular
section 11. Clips 34 can be provided to the base members in order to
prevent the tubing from dangling freely. In addition, flexible tubing 25
is arranged along the legs of triangular section 12 in a manner similar to
that described with respect to triangular section 11. More particularly,
the portion of flexible tubing 25 which is arranged to extend along leg 23
of triangular section 12 is designated in this figure as 31. The portion
which extends along leg 24 is designated as 30; and the portions of
flexible tubing 25 extending along third leg 56 and base member 29 are
designated as 32 and 33, respectively. The flexible tubing is terminated
at each end with respective ports 26 and 27 which permit and control the
passage through the flexible tubing of an image-opaque fluid. Each leg of
the triangular sections, in this embodiment, is provided with a straight
portion of flexible tubing 25.
In an advantageous embodiment, the coordinate system of the instant
invention is constructed entirely of light-weight nylon and rubber. Of
course, other flexible polymeric materials can be utilized in the
construction of the invention. However, use of non-magnetic materials
renders the coordinate system suitable for use with all types of scanners,
including MRI.
FIG. 2 is a schematic representation of the embodiment of FIG. 1
superimposed on the head of a human being. As shown, the triangular
section 12 is represented as having a leg 30, a leg 31, a bisecting leg
32, and a base member 33. These elements of structure correspond to
portions of flexible tubing 25, shown in FIG. 1. The base member is
positioned on the side of the head so as to be parallel to cantho-meatal
line 35. For purposes of illustration, triangular section 12 is
represented in FIG. 3 as superimposed on a human brain. Such
superimposition is stable, and responsive, in this embodiment, to external
anatomical features of the head.
FIGS. 4 and 5 are schematic, simplified representations of the effect of
axial translation of an image plane 40, which is represented
cross-sectionally as a line, on a brain image 42. As shown in this figure,
image plane 40 intersects legs 30, 31, and 32 near where they are joined
together, and therefore they are represented cross-sectionally in brain
image 42 by correspondingly designated image dots, shown on the right-hand
side of the figure, which are relatively close together. Triangular
section 11, which would be on the other side of the brain, is similarly
represented by dots 14, 18, and 15, which correspond in their designation
to the legs of triangular section 11, and are also similarly close
together.
FIG. 5 is identical to FIG. 4, except that image plane 40 is disposed
somewhat lower in coordinate system 12, such that it intersects legs 30,
32, and 31 where they are further apart. Correspondingly, brain image 42
shows corresponding dots 30, 32, and 31 to be spaced further apart from
one another than is represented in FIG. 4. Additionally, points 14, 18,
and 15, which correspond to the leg of triangular section 11 are similarly
spaced further apart than represented in FIG. 4.
FIG. 6 is a schematic representation similar to FIGS. 4 and 5, except that
the image plane is arranged at an angle .THETA. through coordinate system
12. This corresponds to the head being tilted back during imaging so that
the image plane is lower in the anterior, or face region, than at the back
of the head. As can be seen in this figure, this angular orientation of
the image plane causes dots 31 and 32 to be further apart than dots 32 and
30. The ratio of the distances, A:B, in this situation is greater than
unity.
FIG. 7 is identical to FIG. 6, except that image plane 40 is arranged at an
angle .THETA. upward, corresponding to the head being tilted forward
during imaging. In this situation, the ratio A:B is less than unity. As is
evident from the foregoing, when the angle .THETA. has a value of zero,
the ratio of A:B will equal unity.
FIGS. 8 and 9 are schematic representations of variations in the coordinate
system of the present invention. More specifically, FIG. 8 shows the
coordinate system formed of four triangular sections, two on each side.
The triangular sections on each side are inverted with respect to one
another and joined together at their respective apexes.
With respect to FIG. 9, only two triangular sections are used, one on each
side. However, in this embodiment, the triangles are inverted with respect
to one another. Thus, the apex of one triangle is down while that of the
other is up.
An advantage of the coordinate system is that computer analysis can be used
to reconstruct one set of consecutive image planes, illustratively MRI
images, to match another given set of consecutive images, illustratively
PET images, based upon the information provided by use of the coordinate
system with respect to their respective orientations.
Although the invention has been described in terms of specific embodiments
and applications, persons skilled in the art can, in light of this
teaching, generate additional embodiments without exceeding the scope or
departing from the spirit of the claimed invention. Accordingly, it is to
be understood that the drawing and description in this disclosure are
proffered to facilitate comprehension of the invention, and should not be
construed to limit the scope thereof.
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