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Having thus described the preferred embodiment, the invention is now
claimed to be:
1. A clinical method in which a surgical instrument is precisely positioned
relative to an internal region of the subject in advance of an invasive
procedure, the method comprising:
imaging a volume of the subject to locate a structure within the subject
precisely and producing three dimensional diagnostic mapping data
indicative thereof;
transferring the subject to a clinical treatment station at which the
invasive procedure is to be performed, imaging the patient to relocate the
structure within the patient relative to the treatment station by
generating a two dimensional calibration reference image through the
imaged volume that includes the structure prior to instituting the
invasive procedure;
configuring an analogous two dimensional image from the three dimensional
diagnostic mapping data;
comparing the calibration reference and diagnostic data two dimensional
images to determine the relative orientation between the patient and the
three dimensional mapping data; and,
in accordance with the comparing step, moving and orienting the surgical
instrument to position the surgical instrument relative to the imaged
volume for invasive treatment of the located structure.
2. The method as set forth in claim 1 further including generating a series
of planar slice images generated from the mapping data and selecting a
point of entry into the subject and a path through the patient for the
invasive procedure from the planar slice images.
3. The method as set forth in claim 2 further including at the clinical
treatment station prior to the two dimensional calibration reference image
generating step, fixing the position of the surgical instrument relative
to the subject such that the surgical instrument is constrainable to enter
the subject through the selected point of entry and follow the selected
path through the subject.
4. The method as set forth in claim 3 further including inserting the
surgical instrument through the entrance site and along the selected path
of the subject.
5. The method as set forth in claim 4 wherein the instrument insertion step
is performed automatically with a robotic arm arrangement which carries
the surgical instrument.
6. The method as set forth in claim 1 wherein the step of imaging a volume
includes scanning the subject with a computed tomographic scanner and
generating a series of planar images from the mapping data.
7. The method as set forth in claim 1 wherein the step of generating a two
dimensional calibration reference image includes examining the subject
with a digital radiographic imaging apparatus wherein the two dimensional
calibration reference image is a calibration reference shadowgraphic
projection image and wherein the configuring step includes configuring an
analogous projection image from the diagnostic mapping data.
8. The method as set forth in claim 7 wherein the comparing step includes
superimposing the calibration reference shadow graphic projection and the
analogous diagnostic data projection images in a common display.
9. A clinical method in which an internal region of a subject is precisely
located in advance of an invasive procedure, the method comprising:
imaging a volume of the subject at a first location and producing
three-dimensional diagnostic mapping data indicative thereof;
at a second location in which the invasive procedure is to be performed,
imaging the subject to generate a two dimensional calibration reference
image through a region of interest prior to instituting the invasive
procedure, the step of generating a two dimensional calibration reference
image including examining the subject with a digital radiographic imaging
apparatus such that the two dimensional calibration reference image is a
calibration reference shadowgraphic projection image;
projecting a projection image from the three-dimensional diagnostic mapping
data which projection image is analogous to the two dimensional
calibration reference image;
comparing the calibration reference image and the analogous projection
image; and,
adjusting spatial position and angular orientation through which the
mapping data is projected into the analogous projection image until a
selected portion of the analogous projection image most accurately matches
a corresponding selected portion of the calibration reference image,
whereby the mapping data is brought into at least partial registration
with the actual, current position of the subject.
10. In a clinical procedure wherein an internal region of the subject is
subjected to an invasive procedure, precisely locating and mapping said
internal region in advance of the procedure comprising the steps of:
conducting a series of planar scans of the subject and obtaining
three-dimensional electronic mapping data indicative of internal structure
of at least said internal region of the subject from the scans;
generating man-readable images from the mapping data and identifying the
internal region to be treated by the invasive procedure from the
man-readable images;
selecting a point of entry into the subject and a path through the subject
from the man-readable images;
fixing the position of the subject relative to a clinical station where the
invasive procedure is to be performed;
performing a non-invasive imaging of the patient to produce a first
calibration reference image representing a two dimensional shadowgraph of
a least a portion of the subject along a first direction which includes
said internal region;
generating analogous shadowgraphic projection image from the
three-dimensional electronic mapping data which analogous shadowgraphic
projection image represents a projection through the three-dimensional
electronic mapping data along a calibration direction that substantially
matches the first direction;
comparing the calibration reference and three-dimensional electronic
mapping shadowgraphic images to obtain an indication of the location of
said internal region in relation to the clinical station;
positioning an invasive instrument guide to aim a surgical instrument to
enter the subject at the selected point of entry and follow the selected
path; and,
producing a second calibration reference image of the guide and the subject
to check to guide positioning.
11. An apparatus for performing an invasive surgical procedure on a
subject, the apparatus comprising:
scanning means for scanning at least a selected region of the subject and
generating an electronic mapping data representing a three dimensional
region of the subject;
an image memory means for storing the mapping data;
a display means for displaying man-readable diagnostic images reconstructed
from the mapping data in the image memory, which diagnostic images
represent slices through the region of interest;
an imaging means for generating and storing electronic data representative
of a two dimensional reference image through the region of interest, the
imaging means being operatively connected with the display means for
displaying a man-readable two dimensional reference image from the stored
data;
a reformatting means for reformatting the mapping data from the image
memory into a reformatted diagnostic image of the format of the reference
image from the imaging means;
an adjusting means for adjusting spatial position and angular orientation
with which the reformatting means reformats the mapping data such that the
reformatted image more closely matches the reference image; and,
a surgical instrument positioning means for positioning a surgical
instrument relative to the patient to direct the surgical instrument to
penetrate the patient at an entrance point selected from the diagnostic
images, after generation of the images, and proceed along a path selected
from the diagnostic images.
12. The apparatus as set forth in claim 11 further including a portable
electronic data storage means which is operatively connected with the
image memory means for receiving and storing the mapping data therefrom
and which means is transportable to another image memory for transferring
the mapping data thereto.
13. The apparatus as set forth in claim 11 wherein the imaging means is a
digital radiographic imaging means and the reference image is a
shadowgraphic projection image.
14. The apparatus as set forth in claim 13 wherein the reformatting means
includes means for reformatting a shadowgraphic projection from the
mapping data which is analogous to the reference shadowgraphic projection
images of the digital radiographic imaging means such that the reformatted
image represents a shadowgraphic projection and wherein the adjusting
means adjusts the spatial position and angular orientation with which the
projections are reformatted, whereby the orientation and position of the
reformatted shadowgraphic image is adjustable until it most accurately
matches the reference shadowgraphic image.
15. The apparatus as set forth in claim 14 further including a
superimposing means for combining the reformatted and reference
shadowgraphic images to facilitate comparison thereof.
16. The apparatus as set forth in claim 11 wherein the scanning means is a
computerized tomographic scanner.
17. The apparatus as set forth in claim 11 wherein the surgical instrument
positioning means includes an arm arrangement and a control means for
robotically controlling the arm arrangement. |
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Description |
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BACKGROUND OF THE INVENTION
The present invention relates to the art of non-invasive examination and
internal imaging. It finds particular application in combination with
stereotactic surgical procedures and will be described with particular
reference thereto. However, it is to be appreciated that the present
invention may find other applications in which it is advantageous to
orient a patient or examined object relative to images or other
representations from previously collected data.
Heretofore, computed tomography scanning has been utilized to assist in
various invasive clinical procedures, such as biopsies, the drainage of
abscesses, placement of radiation implants, orthopedic pin placement,
contrast injections, and the like. In one prior art procedure, the patient
was tightly strapped to a patient table mounted on a position control
structure for controlledly indexing the patient table through the imaging
region of a CT scanner. Based on the reconstructed images from a plurality
of planar CT scans, a path for insertion of the needle or probe was
determined. Without moving the patient relative to the patient table, the
patient table was shifted a preselected precise distance from the imaging
region of the CT scanner. The shifting was necessary to provide ready
surgical access to the patient without interference from the scanner
structure. This shifting of the patient table caused a precisely known
offset between the image data and the region of interest of the patient. A
guide structure was positioned relative to the patient at the appropriate
position and angle to direct a needle or probe through a selected point of
entry and along the selected path.
After positioning the needle in the guide, the patient table was shifted
such that the region of the patient of interest, the guide, and the needle
were repositioned in the examination zone of the CT scanner. More CT scans
were made to check the accuracy of the needle positioning relative to the
selected path. If necessary, the position or angular orientation of the
needle could be adjusted and additional scans taken until an acceptable
alignment was achieved. Thereafter, the needle was inserted manually into
the patient.
One of the drawbacks of this procedure is that it consumed excessive
amounts of expensive, computed tomography scanner time. Because the
patient had to be kept at precisely known distances relative to the
scanner, the surgery was performed on the scanner associated patient table
in the CT scanner room. During the surgery, the scanner was unavailable
for performing scanning functions on other patients.
To increase the efficiency of CT scanner utilization, stereotactic fixtures
have been developed for performing head and brain surgery remote from the
CT scanner. The fixture was rigidly attached to the patient skull prior to
the CT scan such that a fixed orientation between the fixture and the
skull was maintained even as the patient moved. Reference marks on the
fixture provided corresponding reference marks on the resultant images
which indicated the relative position and orientation of the fixture and
the images.
Thereafter, the patient, with the stereotactic device remaining attached to
the skull, was removed to a separate surgical facility freeing the CT
scanner for use by other patients. By studying the various images, the
doctor planned and calculated an appropriate entry point and path for the
needle or probe to follow. Because the relative position of the fixture
and the interior head tissue remained fixed, probe guides and distance
limiting structures could be selectively positioned on the stereotactic
fixture such that the probe or needle would follow the calculated path.
See for example U.S. Pat. No. 4,341,220, issued July 27, 1982 to Perry.
One of the drawbacks of the stereotactic fixtures is that their use was
limited to areas of the body in which the fixture could be rigidly
attached to bone tissue, e.g. the skull. Another drawback to stereotactic
fixtures is that they must remain attached between the CT scan and the
surgery. The stereotactic fixture could not be reattached with sufficient
accuracy to assure the safety of most surgical procedures. For on-going
surgical treatment, it was necessary that the fixture be reattached and a
new CT scan conducted before each surgical procedure. The repetitive CT
scans not only used large amounts of scanner time, but also subjected the
patient to numerous doses of radiation.
The present invention provides a new and improved method and apparatus
which enables the CT scan data to be realigned with the patient at a
subsequent time and a remote location.
SUMMARY OF THE INVENTION
In accordance with a first aspect of the present invention, a method is
provided for precisely locating an internal region of interest in advance
of a clinical procedure. At a first site, a series of planar scans are
conducted and a map of the internal structure of the subject is obtained
therefrom. The patient is moved to a second site at which the invasive
procedure is to be performed. At the second site, the patient is again
examined but with a different, second non-invasive imaging technique to
generate an image with a known spatial relationship to the patient. An
image most nearly corresponding to the second technique image is generated
from the internal structure map. The two images are compared to obtain an
indication of the relative spatial orientation and position between the
patient and the map. In this manner, the map of at least a portion of the
internal structure of interest may be realigned with the actual spatial
position and orientation of the corresponding internal structure of the
patient.
In accordance with a more limited aspect of the invention, the image
generated by the second imaging technique is a two-dimensional
shadowgraph.
In accordance with another aspect of the present invention, an apparatus is
provided for imaging a region of interest in advance of an invasive
procedure. A scanning means is provided for scanning a series of planes of
the subject and generating a map or image data indicative thereof. At
least one image generating means is provided for generating a selected
image from the mapping. At least one display means is provided for
displaying the selected image. In this manner, a doctor can examine
selected planes through a region of interest to select a path through the
patient for a biopsy needle or the like. A different imaging means is
provided for generating at least one two-dimensional reference image of a
patient through the region of interest such that the two-dimensional image
and the patient have a known spatial position and orientation relationship
relative to each other. Means are provided for generating an analogous
two-dimensional image from the map such that the spatial position and
orientation of the map can be coordinated and aligned with a reference
image, hence the patient. In this manner, the entry points and surgical
paths selected on the images displayed on the display means can be
coordinated with corresponding physical locations and orientations of the
patient.
One advantage of the present invention is that it improves the efficiency
of the utilization of CT scanners, magnetic resonance imaging, and other
multi-planar imaging equipment.
Another advantage of the present invention is that it enables multi-planar
image data to be utilized at subsequent times to assist in surgical
procedures.
Yet another advantage of the present invention is that it facilitates the
registration of multi-planar and other image data with the current spatial
position and orientation of the patient.
Still further advantages of the present invention will become apparent to
those of ordinary skill in the art upon reading and understanding the
following detailed description of the preferred embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention may take form in various steps and arrangements of steps and
various components and arrangements of components. The drawings are only
for purposes of illustrating a preferred embodiment of the invention and
are not to be construed as limiting it. Wherein the figures show:
FIG. 1 is a diagrammatic view of a multi-planar slice imaging station;
FIG. 2 is a diagrammatic view of an apparatus at a surgical station for
bringing the multi-planar slice image data into registration with the
patient's current spatial position and orientation.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A detailed non-invasive examination of the patient or subject is made,
preferably with a multi-slice imager A at an examination station or room,
FIG. 1. Commonly, the examination results in electronic mapping data which
represents a series of planar slices through the patient, a three
dimensional region of the patient, or the like. Although the embodiment of
FIG. 1 illustrates a computed tomography or CT scanner, it is to be
appreciated that magnetic resonance and other non-invasive images may also
be utilized.
The mapping data is transferred to a second site, specifically a surgical
operating theater or station, FIG. 2. At the second site, the patient is
examined with a second imaging device B, preferably an imaging device
which generates an electronic data representing a two dimensional
shadowgraphic projection at selectable angles through the patient.
Analogous shadowgraphic projections or other images are synthesized or
reconstructed from the mapping data from the first imager A which are
compared with reference image representations from the second imager B.
The shadowgraphic image synthesized from the mapping data of the first
imager is adjusted until it is brought into registration with the
reference images. Stereotactic surgical equipment or guides C are mounted
at selectable positions and angular orientations relative to the second
imager. The stereotactic surgical equipment is readily positioned relative
to the patient to direct invasive surgical devices along paths selected
from the mapping or first imager data.
With particular reference to FIG. 1, the first multi-slice imager A of the
preferred embodiment includes an X-ray source 10 which directs a fan beam
of penetrating radiation through a scan circle 12 before impinging upon an
arc of radiation detectors 14. A rotating means 16 rotates at least the
source of radiation 10 around the scan circle to irradiate a patient
positioned therein from a plurality of directions. Magnetic resonance and
other imagers are also contemplated.
A patient table or couch 20 is mounted in association with the scanner for
selectively disposing a patient within the scan circle. A top 22 of the
patient table and the patient thereon are selectively moved or indexed
along a path transverse to the fan beam by a patient moving or indexing
means 24.
As the radiation source 10 rotates around the scan circle, an image
reconstruction means 30 reconstructs the data collected by each of a
plurality of detectors 14 into mapping data representative of planar
slices of the patient positioned within the scan circle. The slice data is
stored in a three dimensional or multi-slice memory 32. The indexing means
24 then indexes the patient an incremental distance and mapping data
representing additional planar slices through the patient are generated,
reconstructed, and stored in the multi-slice memory 32. This process is
repeated until a plurality or series of slices have been examined and the
corresponding mapping data stored in the multi-slice memory 32.
Conceptually, the multi-slice memory can be pictured as a three
dimensional array of cubic cells, each cell storing a number which
designates the relative gray scale of a corresponding pixel of a
reconstructed image. Each slice corresponds to one plane of cells and
adjoins the plane of cells corresponding to the slice taken to either side
thereof. It is to be appreciated, however, that the resolution within each
plane may differ from the interplanar spacing, i.e. the cells may, in some
scanners, need to be conceptualized as being more of a rectangular prism
than a cube.
A physician or operator panel includes a plane and angle selection means 34
on which any one of the available planes may be selected for display. As
is conventional in the art, a plane at any angle or orientation through
the multi-sliced diagnostic image data may be selected. An image
formatting or slice select means 36 performs the appropriate geometrical
calculations to determine which cubes or rectangular data prisms are
intersected by the selected plane. The image format means then addresses
the appropriate memory addresses of the image memory 32 to extract the
appropriate mapping data or gray scale numbers to format an image for
display by a display means 38. Where appropriate, the image format means
may perform a weighted averaging or interpolation of data form adjacent
cells where the selected plane passes between adjacent cells or off center
through one of the cells.
The data from the image memory is transferred to a residual storage means
40. The residual storage means may be a central data processing area of
the hospital facility, a multi-hospital computer network, or a readily
transportable memory medium such as a disk or tape. The readily
transported tape or disc may be recorded at the patient site or at central
processing. The physician may view the various imaged planes at the
examination site or may call up the data at a remote viewing site, such as
the physician's office or a viewing room, to make a more detailed
examination of the data while freeing up the imaging apparatus. The remote
viewing site includes at least a multi-slice memory which is loaded from
the tape or disc, plane and angle selection means, an image formatting
means, one or more video display means, and electronic image enhancement
circuitry.
With reference to FIG. 2, the second imaging apparatus B in one preferred
embodiment is a digital radiographic imaging system. Optionally, other
imagers which are lower cost, faster, or more readily accessible than the
first imager A may also be utilized, e.g. ultrasound, conventional x-ray,
obsolete, low resolution, or single plane CT scanners, or the like. An
X-ray source 50 projects a three dimensional swath of radiation onto an
X-ray detecting array 52. The array 52 in the illustrated embodiment is a
rectangular array of CCD devices or other electronic components which
convert radiation intensity into corresponding electronic signals. A
patient table 54 supports and fixes the region of the patient which had
been examined by the first imaging means A between the X-ray source and
detector array. Optionally, belts or straps may be utilized to fix the
position of the patient relative to the patient table and second imager
more securely. In this manner, electronic data representing a
shadowgraphic calibration reference image of the region of interest is
generated. It is to be appreciated, that the radiation which generates the
shadowgraphic image originates at essentially a point source in the X-ray
tube 50 and passes along diverging rays between the X-ray source and each
element of the detector array 52. Thus, the shadowgraphic image represents
shadowgraphic projections along diverging rays through the region of
interest. The exact path followed by each ray is readily calculated from
the geometry of the second imager apparatus B. In particular, from the
distance between the X-ray source 50 and the patient, the distance between
the X-ray source 50 and the detector arrays 52, and the dimensions of the
detector array, the path which generates each element of the shadowgraphic
image is readily calculated.
A shadowgraphic or calibration reference image memory 60 stores the
shadowgraphic image data from the detector array 52. A calibration
reference image format means 62 formats the data appropriately to produce
a man-readable display on a display means 64.
The multi-slice diagnostic image data from the residual storage means 40 is
transferred to a three dimensional or multi-slice image memory 32' of
substantially the same configuration as the three dimensional or
multi-slice image memory of the first imager A. An image format means 36'
selects and formats the appropriate data from the image memory to produce
a man-readable display on the display means 64 representing the plane and
angular orientation selected on a plane and angular orientation selection
means 34'. These means function analogously with the correspondingly
numbered elements of the first imager.
A projection format means 70 selects the appropriate data from the
multi-slice memory 32' to synthesize a shadowgraphic image analogous to
the image generated from the data in the shadowgraphic image memory 60. In
particular, the projection format means 70 selects data in accordance with
the geometry of the second imager B. The selection may be conceptualized
by projecting imaginary rays originating at a point the same distance from
the three dimensional array of cubic image cells as the X-ray tube 50 is
from the patient and which diverge at the same angles as the rays of the
second scanner. The data in each of the cells through which one of these
rays passes is summed to generate one pixel representing a shadowgraphic
projection image from the multi-slice diagnostic data. The plane and
orientation selection means 34' is interconnected with the projection
format means such that the origin of the rays may be selectively rotated
and shifted.
A superimposing means 72 superimposes the shadowgraphic projection
diagnostic and calibration reference projection images from the projection
format means and from the shadowgraphic image format means 62. The image
from the projection format means 70 is adjusted in orientation and
position by the plane and angle selection means 34' until at least a
region of interest within the images is most accurately superimposed and
coincident. If appropriate, a scale adjusting means 74 may adjust the
dimensional scale of the image from the projection format means 70. The
scale adjustment may be made by linearly adjusting one or more dimensions
or by shifting the origin of the converging rays closer or further away
from the region of interest. The scale adjusting means and the plane and
angle selection means include a scale, position, and angle offset memory
76 for storing the scale, position, and angle selected data at which
calibration is completed. Where appropriate, the memory may sum scale,
position, and angle data received from other sources. After the
calibration is completed, the scale, position, and angle data are fixed in
the memory such that the position and orientation selection means may be
utilized for calibrations along another axis or to select the orientation
of diagnostic images for viewing.
Optionally, an automatic alignment means 78 may be utilized to bring the
two images into coincidence. The automatic alignment means may utilize
conventional automatic picture focuses techniques or map reading and
identification techniques for iteratively adjusting the selected
orientation, position, and scale of the diagnostic data projection image
until a best match of the images or a selected portion thereof is
achieved.
Preferably, the radiation source 50 and detector array 52 of the second
imaging means B are rotatable such that a second calibration reference
shadowgraphic image is generated through the patient from another angular
orientation. For simplicity of mathematical calculation, the calibration
reference images are preferably taken through the patient along the
orthogonal x and y coordinate axes, such as vertical and horizontal. An
angle resolver 80 detects the exact angular position of the X-ray source
and detector array which angular position is stored in a memory means 82.
The angle memory means 82 is interconnected with the scale, position, and
angle offset means to provide a reference orientation of the shadowgraphic
calibration reference image from the second imager to define the axis
relative to which the position and orientation offset data is relative.
With the X-ray source and detector array in the second position, the two
superimposed shadowgraphic images are again brought into alignment. If the
X-ray source and detector ray are positioned vertically for the first
adjustment, the first adjustment provides the appropriate spatial position
and angular orientation offsets relative to the vertical axis. If the
X-ray sources and detector array are positioned along a horizontal axis
for the second calibration, the second scale, origin, and angular
adjustment will provide the appropriate spatial position and angular
orientation offsets to adjust the data in the image memory 32' relative to
the horizontal axis.
After the calibration adjustment, planes and orientations called up on the
plane and orientation selection means 34' have the appropriate angular and
spatial offset added thereto by the offset memory 76 such that the image
format means 36' selects the planes and orientations in the coordinate
system in which the patient is currently disposed. A coordinate
superimposing means 84 superimposes dimensions or other coordinate
position data on images generated by the diagnostic images.
In one embodiment, the stereostatic surgery means C includes a guide or
tube 90 which is mounted on a carriage 92 which may be selectively
positioned along the longitudi | | |
