U.S. patent application number 13/632916 was filed with the patent office on 2013-01-31 for three dimensional co-registration for intravascular diagnosis and therapy.
This patent application is currently assigned to VOLCANO CORPORATION. The applicant listed for this patent is VOLCANO CORPORATION. Invention is credited to VINCENT J. BURGESS, RANDALL KENT HANSON, RICHARD SCOTT HUENNEKENS, JON D. KLINGENSMITH, MARJA PAULIINA MARGOLIS, NANCY PERRY POOL, BLAIR D. WALKER.
Application Number | 20130030295 13/632916 |
Document ID | / |
Family ID | 37595986 |
Filed Date | 2013-01-31 |
United States Patent
Application |
20130030295 |
Kind Code |
A1 |
HUENNEKENS; RICHARD SCOTT ;
et al. |
January 31, 2013 |
Three Dimensional Co-Registration for Intravascular Diagnosis and
Therapy
Abstract
A method and system are disclosed for creating, in a coordinated
manner, graphical images of a body including vascular features from
a combination of image data sources. The method includes initially
creating an angiographic image of a vessel segment. The
angiographic image is, for example, either a two or three
dimensional image representation. Next, a vessel image data set is
acquired that is distinct from the angiographic image data. The
vessel image data set comprises information acquired at a series of
positions along the vessel segment. An example of such vessel image
data is a set of intravascular ultrasound frames corresponding to
circumferential cross-section slices taken at various positions
along the vessel segment. The angiographic image and the vessel
image data set are correlated by comparing a characteristic
rendered independently from both the angiographic image and the
vessel image data at positions along the vessel segment.
Inventors: |
HUENNEKENS; RICHARD SCOTT;
(SAN DIEGO, CA) ; BURGESS; VINCENT J.; (SAN DIEGO,
CA) ; MARGOLIS; MARJA PAULIINA; (CORAL GABLES,
FL) ; WALKER; BLAIR D.; (MISSION VIEJO, CA) ;
KLINGENSMITH; JON D.; (EL DORADO HILLS, CA) ; POOL;
NANCY PERRY; (EL DORADO HILLS, CA) ; HANSON; RANDALL
KENT; (SACRAMENTO, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
VOLCANO CORPORATION; |
SAN DIEGO |
CA |
US |
|
|
Assignee: |
VOLCANO CORPORATION
SAN DIEGO
CA
|
Family ID: |
37595986 |
Appl. No.: |
13/632916 |
Filed: |
October 1, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11473974 |
Jun 23, 2006 |
8298147 |
|
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13632916 |
|
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60694014 |
Jun 24, 2005 |
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Current U.S.
Class: |
600/440 |
Current CPC
Class: |
A61B 8/12 20130101; A61B
6/504 20130101; A61B 8/5238 20130101; A61B 6/5247 20130101 |
Class at
Publication: |
600/440 |
International
Class: |
A61B 8/12 20060101
A61B008/12; A61B 6/00 20060101 A61B006/00 |
Claims
1-22. (canceled)
23. A method, comprising: obtaining angiographic image data of a
vessel segment from an imaging device positioned external to the
vessel segment; creating a three-dimensional image of the vessel
segment based upon the obtained angiographic image data; obtaining
intravascular ultrasound (IVUS) image data of the vessel segment
from an imaging device positioned within the vessel segment,
wherein the IVUS image data comprises a series of intravascular
images acquired as the imaging device positioned within the vessel
segment is moved through and along the vessel segment; correlating
the IVUS image data to the three-dimensional image of the vessel
such that each of the images of the series of intravascular images
of the IVUS image data is correlated to a portion of the
three-dimensional image of the vessel created based upon the
obtained angiographic image data, wherein correlating the IVUS
image data to the three-dimensional image of the vessel includes
aligning the images of the series of intravascular images of the
IVUS image data both axially and circumferentially to the
corresponding portions of the three-dimensional image of the
vessel; and rendering simultaneously on a display an image of the
series of intravascular images of the IVUS image data and at least
the correlated portion of the three-dimensional image of the vessel
as determined by the correlating step.
24. The method of claim 23, wherein time vectors of the series of
intravascular images and a pullback speed of the imaging device are
utilized to axially align the images of the series of intravascular
images of the IVUS image data with the three-dimensional image of
the vessel.
25. The method of claim 23, wherein the lumen measurement is a
cross-sectional area.
26. The method of claim 25, wherein determining the best fit
between the cross-sectional area of the vessel segment as depicted
in the images of the series of intravascular images of the IVUS
image data and the cross-sectional area of the vessel segment as
depicted in the three-dimensional image of the vessel segment based
on the obtained angiographic image data comprises determining a
minimum of the sum of the squared differences between the
cross-sectional area of the vessel segment as depicted in the
images of the series of intravascular images of the IVUS image data
and the cross-sectional area of the vessel segment as depicted in
the three-dimensional image of the vessel segment based on the
obtained angiographic image data.
27. The method of claim 25, wherein determining the best fit
between the cross-sectional area of the vessel segment as depicted
in the images of the series of intravascular images of the IVUS
image data and the cross-sectional area of the vessel segment as
depicted in the three-dimensional image of the vessel segment based
on the obtained angiographic image data comprises determining a
minimum of n = 1 N ( A IVUS - A Angio ) 2 , ##EQU00002## where
A.sub.IVUS is the cross-sectional area of the vessel as depicted in
images 1 to N of the series of intravascular images of the IVUS
image data and A.sub.Angio is the cross-sectional area of the
vessel as depicted in the three-dimensional image of the vessel
segment based on the obtained angiographic image.
28. The method of claim 23, wherein the images of the series of
intravascular images of the IVUS image data are axially aligned
with the three-dimensional image of the vessel by applying a
skewing displacement.
29. The method of claim 23, wherein the images of the series of
intravascular images of the IVUS image data are axially aligned
with the three-dimensional image of the vessel by applying a
warping displacement.
30. The method of claim 31, wherein the images of the series of
intravascular images of the IVUS image data are circumferentially
aligned with the three-dimensional image of the vessel based on a
best angular fit.
31. The method of claim 30, wherein the best angular fit is
determined for a plurality of the images of the series of
intravascular images of the IVUS image data.
32. The method of claim 30, wherein the best angular fit is
determined for each of the images of the series of intravascular
images of the IVUS image data.
33. The method of claim 30, wherein a degree of rotation between
adjacent images of the series of intravascular images of the IVUS
image data is limited.
34. The method of claim 33, wherein the degree of rotation between
adjacent images of the series of intravascular images of the IVUS
image data is limited by a spline fit.
35. The method of claim 33, wherein the degree of rotation between
adjacent images of the series of intravascular images of the IVUS
image data is limited by a cubic polynomial fit.
36. The method of claim 23, wherein each of the images of the
series of intravascular images of the IVUS image data is correlated
to a portion of the three-dimensional image of the vessel created
based upon the obtained angiographic image data in a live mode.
37. The method of claim 36, wherein the angiographic image data and
the IVUS image data are obtained simultaneously.
38. The method of claim 23, wherein each of the images of the
series of intravascular images of the IVUS image data is correlated
to a portion of the three-dimensional image of the vessel created
based upon the obtained angiographic image data in a playback
mode.
39. The method of claim 23, wherein the angiographic image data and
the IVUS image data are obtained simultaneously.
40. The method of claim 39, further comprising aligning the imaging
device positioned external to the vessel segment with the imaging
device positioned within the vessel segment using at least one
fiduciary point.
41. The method of claim 40, wherein the at least one fiduciary
point is a marker associated with the imaging device positioned
within the vessel segment.
42. A system, comprising: a processing system configured to: obtain
angiographic image data of a vessel segment generated from an
imaging device positioned external to the vessel segment; create a
three-dimensional image of the vessel segment based upon the
obtained angiographic image data; obtain intravascular ultrasound
(IVUS) image data of the vessel segment generated from an imaging
device positioned within the vessel segment, wherein the IVUS image
data comprises a series of intravascular images acquired as the
imaging device positioned within the vessel segment is moved
through and along the vessel segment; correlate the IVUS image data
to the three-dimensional image of the vessel such that each of the
images of the series of intravascular images of the IVUS image data
is correlated to a portion of the three-dimensional image of the
vessel created based upon the obtained angiographic image data,
wherein correlating the IVUS image data to the three-dimensional
image of the vessel includes aligning the images of the series of
intravascular images of the IVUS image data both axially and
circumferentially to the corresponding portions of the
three-dimensional image of the vessel; and outputting a signal to a
display in communication with the processing system to render
simultaneously on the display an image of the series of
intravascular images of the IVUS image data and at least the
correlated portion of the three-dimensional image of the vessel as
determined by the correlating step.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority of Walker et al. U.S.
provisional application Ser. No. 60/694,014 filed on Jun. 24, 2005,
entitled "Three-Dimensional Co-Registration for Intravascular
Diagnosis and Therapy", the contents of which are expressly
incorporated herein by reference in their entirety including the
contents and teachings of any references contained therein.
AREA OF THE INVENTION
[0002] The present invention generally relates to imaging blood
vessels. More particularly, the present invention is directed to
methods and systems for generating composite displays generally
including at least a first graphical image rendered from a first
type of data and a second graphical image rendered from a second
type of data. A particular example of such composite graphical
display comprises a graphically displayed three dimensional
angiogram that is displayed in combination with a second graphical
image created from IVUS information.
BACKGROUND OF THE INVENTION
[0003] Atherosclerosis is treated in arteries of the heart, head,
neck and peripheral portions of the body using many different
methods. The most popular methods, such as angioplasty, bare metal
stenting, drug eluting stenting (permanently implantable and
biodegradable), various types of energy delivery and rotational
atherectomy, all treat an artery equally around the circumference
of a target length of the arterial lumen. These devices are
generally circumferentially symmetric, and cannot selectively treat
one circumferential sector of the targeted length of the artery any
different from another. Almost always, the targeted length of the
artery identified for treatment is determined using angiography,
which graphically depicts a vessel lumen, or intravascular
ultrasound (IVUS), which graphically depicts the atherosclerotic
plaque itself. With IVUS, the thickness of the atherosclerotic
plaque can be determined along the length of the diseased area and
at specific radial positions around its circumference. More often
than not, the plaque is eccentric and thus varies in thickness at
particular positions of a circumferential cross-sectional of the
vessel. Treatment of plaque using the aforementioned
circumferentially symmetric methods can sometimes cause undesired
results. For example, drug eluting stents deliver drugs that
inhibit neo-intimal proliferation (known as restenosis). In the
section of artery where the stent is expanded, any normal
(non-diseased) portion of vessel may not benefit from getting the
same dosage of drug as the diseased portion.
[0004] Some methods for treating atherosclerosis, such as
directional athrectomy, needle aided drug injection or certain
types of brachytherapy (radiation), can actually vary the treatment
along different circumferential sectors of the artery. The
catheters used for these treatment methods are typically
circumferentially asymmetric and have at least a portion that is
torquable (rotatable), and thus able to be steered into a desired
circumferential orientation. However, effective use of the
asymmetric treatments is difficult because of certain
characteristics of current imaging methods. For example, because
angiography only shows an image of the lumen of the blood vessel,
it is impossible to identify exactly where, in a particular
circumferential cross-section, the atherosclerotic plaque is
located and the plaque's thickness. IVUS does make it possible to
view the circumferential location and thickness of atherosclerotic
plaque in a length of a vessel, but unless the ultrasonic
transducer is attached to the actual treatment device, it is
difficult to use the IVUS image to direct the treatment catheter
with precision. This is especially difficult in coronary arteries,
where heart motion adds error. Attempts to include transducers on
the treatment catheter have been moderately successful (U.S. Pat.
No. 6,375,615 to Flaherty) but the additional components make it
more difficult to build a small catheter, which is flexible and can
track easily in the artery. Some other catheters have been
developed (U.S. Pat. Nos. 4,821,731 and 5,592,939, both to
Martinelli) which can combine IVUS imaging with tip positioning
technology. This enables displaying a three dimensional graphical
representation of the plaque, including any tortuosity inherent in
the artery. However, additional capital equipment is required in
the procedure room to perform this type of imaging and adds cost to
performing the procedure.
[0005] Most of the methods described above are predominantly used
to improve blood flow in stenosed areas of the artery, thus
allowing for better delivery of blood to downstream tissue.
Recently, more attention has been paid to vulnerable plaque--plaque
that is prone to rupture, even though it may not actually be a
stenotic lesion that limits flow prior to rupture. This is
especially critical in coronary arteries, where a lesion rupture,
combined with thrombosis, can cause a serious or even fatal
myocardial infarction (heart attack). The lesion rupture can
actually cause material, such as tissue factor, to dump out of the
plaque, into the bloodstream, forcing the blood into a
hypercoagulable state. Currently, angiography is of limited value
in identifying vulnerable plaque, because this plaque is often
non-stenotic, and looks similar to the normal vessel on an
angiogram. New tissue characterization methods associated with IVUS
(U.S. Pat. No. 6,200,268 to Vince and U.S. Pat. No. 6,381,350 to
Klingensmith, as well as U.S. patent application Ser. Nos.
10/647,977, 10/649,473 and 10/647,971) show promise for identifying
vulnerable plaque, and a patient having a significant amount of
vulnerable plaque. There are currently no standard methods to treat
patients having vulnerable plaque once such patients are
identified.
SUMMARY OF THE INVENTION
[0006] Creating, in a coordinated manner, graphical images of a
body including vascular features from a combination of image data
sources, in accordance with the present invention, comprises
initially creating an angiographic image of a vessel segment. The
angiographic image is, for example, either a two or three
dimensional image representation. Next, a vessel image data set is
acquired that is distinct from the angiographic image data. The
vessel image data set comprises information acquired at a series of
positions along the vessel segment. An example of such vessel image
data is a set of intravascular ultrasound frames corresponding to
circumferential cross-section slices taken at various positions
along the vessel segment. The angiographic image and the vessel
image data set are correlated by comparing a characteristic
rendered independently from both the angiographic image and the
vessel image data at positions along the vessel segment.
[0007] The aforementioned steps are performed in a variety of
imaging environments/modalities to render a broad variety of
graphical displays of three-dimensional image data for carrying out
a variety of diagnostic and treatment regimens including, for
example, balloon angioplasty and atherectomy procedures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] While the claims set forth the features of the present
invention with particularity, the invention, together with its
objects and advantages, may be best understood from the following
detailed description taken in conjunction with the accompanying
drawing of which:
[0009] FIG. 1 is a graphical illustration of a three dimensional
length of artery, including a highly diseased segment;
[0010] FIG. 2 is a graphical illustration of a portion of the
artery depicted in FIG. 1 with a longitudinal section removed along
lines 2 to illustratively depict different elements of
atherosclerotic plaque;
[0011] FIG. 3 is a graphical illustration of the artery from FIGS.
1 and 2 wherein an imaging catheter has been inserted in the
artery;
[0012] FIG. 4 is detailed view of a section of the artery depicted
in FIG. 3 including an imaging catheter in the artery;
[0013] FIGS. 5a and 5b show graphical display interfaces rendered
by a tissue characterization system for use with intravascular
ultrasound (IVUS);
[0014] FIG. 6a is a set of graphical images depicting a
three-dimensional reconstruction method using two two-dimensional
angiographic images;
[0015] FIG. 6b is a flowchart depicting a set of exemplary steps
for creating a co-registered three-dimensional graphical
display;
[0016] FIG. 7 illustratively depicts a vessel reconstruction
graphical image based on image creation techniques embodied in a
system and method incorporating the present invention;
[0017] FIGS. 8a, 8b and 8c illustratively depict the use of a
directional atherectomy catheter according to guidance provided
from the vessel reconstruction;
[0018] FIG. 9 illustratively depicts a series of custom, single
link stents which have been crimped onto a dilatation balloon for
placement in a diseased blood vessel;
[0019] FIG. 10 illustratively depicts a graphical display image
including an overlay of the reconstruction over a live
two-dimensional angiographic image;
[0020] FIG. 11 illustratively depicts a first graphic display in
relation with a graphical representation of a three-dimensional or
two-dimensional image;
[0021] FIG. 12 illustratively depicts a second graphic display in
relation with a graphical representation of a three-dimensional or
two dimensional image;
[0022] FIG. 13 illustratively depicts a third graphic display in
relation with a graphical representation of a three-dimensional or
two-dimensional image;
[0023] FIG. 14 illustratively depicts a graph including two
separate sequences of values corresponding to lumen area, in
relation to image frame number and linear displacement along an
imaged vessel, prior to axial registration adjustment;
[0024] FIG. 15 illustratively depicts a graph including twp
separate sequences of values corresponding to lumen area, in
relation to image frame number and linear displacement along an
imaged vessel, after axial registration adjustment;
[0025] FIG. 16 illustratively depicts a graphical display of
angiography and vessel (e.g., IVUS) images on a single graphical
display prior to axial registration adjustment;
[0026] FIG. 17 illustratively depicts a graphical display of
angiography and vessel (e.g., IVUS) images superimposed on a single
graphical display after axial registration adjustment;
[0027] FIG. 18 illustratively depicts the process of
circumferential registration of angiography and vessel (e.g., IVUS)
image sets;
[0028] FIG. 19 illustratively depicts angular image displacement in
relation to circumferential registration of angiography and vessel
(e.g., IVUS) image sets; and
[0029] FIG. 20 illustratively depicts a graph of actual and best
fit rotational angle corrections displayed in relation to image
frame number.
DETAILED DESCRIPTION OF THE DRAWINGS
[0030] In FIG. 1, a diseased artery 5 with a lumen 10 is shown.
Blood flows through the artery 5 in a direction indicated by arrow
15 from proximal end 25 to distal end 30. A stenotic area 20 is
seen in the artery 5. FIG. 2 shows a sectioned portion of the
stenotic area 20 of the artery 5. An artery wall 35 consists of
three layers, an intima 40, a media 45 and an adventitia 55. An
external elastic lamina (EEL) 50 is the division between the media
45 and the adventitia 55. A stenosis 60 is located in the artery 5
and limits blood flow through the artery. A flap 65 is shown at a
high stress area 70 of the artery 5. Proximal to the stenosis 60 is
an area of vulnerability 75, including a necrotic core 80. A
rupture commonly occurs in an area such as the area of
vulnerability 75.
[0031] FIG. 3 illustratively depicts an imaging catheter 85 having
a distal end 95 that is inserted into the stenotic area 20 of the
artery 5. The imaging catheter 85 is inserted over a guidewire 90,
which allows the imaging catheter 85 to be steered to the desired
location in the artery 5. As depicted in FIG. 4, the imaging
catheter 85 includes an imaging element 100 for imaging the
diseased portions and normal portions of the artery 5. The imaging
element 100 is, for example, a rotating ultrasound transducer, an
array of ultrasound transducer elements such as phased array/cMUT,
an optical coherence tomography element, infrared, near infrared,
Raman spectroscopy, magnetic resonance (MRI), angioscopy or other
type of imaging technology. Distal to the imaging element 100 is a
tapered tip 105 which allows the imaging catheter 85 to easily
track over the guidewire 90, especially in challenging tortuous,
stenotic or occluded vessels. The imaging catheter 85 can be pulled
back or inserted over a desired length of the vessel, obtaining
imaging information along this desired length, and thereafter
creating a volumetric model of the vessel wall, including the
diseased and normal portions, from a set of circumferential
cross-section images obtained from the imaging information. Some
technologies, such as IVUS, allow for the imaging of flowing blood
and thrombus.
[0032] FIGS. 5a and 5b illustratively depict, by way of example,
features of a vascular tissue characterization system marketed by
Volcano Corporation. As graphically depicted in angiogram 130, a
two dimensional image of an artery lumen 135 on its own does not
provide visual information about atherosclerotic plaque that is
attached to walls of an artery containing the lumen 135. Instead
the angiogram 130 only depicts information about a diameter/size of
the lumen 135 through which blood flows. A Gray scale IVUS
cross-sectional image 115 demonstrates a cross-sectional view of
the lumen 135 and atherosclerotic plaque that surrounds the lumen.
Known automatic border detection algorithms executed by an IVUS
image data processing system facilitate identifying a luminal
boundary 125 and an EEL 110. Plaque components are identified from
information derived from IVUS radiofrequency backscatter and are
color coded. The various characterized and graphically depicted
plaque components potentially consist, by way of example, fibrous,
fibro-lipidic (fibro fatty), necrotic core, calcified (dense
calcium), blood, fresh thrombus, and mature thrombus. The RF
backscatter can also give information to identify and color code
stent materials such as metallic or polymeric stents. The
distribution of components in a cross-section or in the entire
volume of the vessel analyzed is displayed by way of example
through various graphics depicted in a bracketed portion 145 of an
exemplary graphical display depicted in FIG. 5b. In addition to the
cross-sectional display images rendered in portion 145, a
longitudinal display region 140 is also included in the
illustrative graphical display in FIG. 5b that depicts information
obtained from portions of a set of circumferential cross-sectional
slides.
[0033] FIG. 6a illustratively depicts the general concept behind a
prior art three-dimensional reconstruction analysis system. A first
two-dimensional angiographic image 150 taken in a first view plane
and a second two-dimensional angiographic image 155, taken in a
second view plane differing from the first view plane are combined
and analyzed to create a graphical representation of a
three-dimensional image depicted on a graphical display 160. The
image displayed on the graphical display 160 provides a much more
realistic graphical representation of a lumen of an actual artery
(or other blood vessel) than the typical two-dimensional
angiography images.
[0034] In accordance with an aspect of an imaging system embodying
the present invention, IVUS images are co-registered with the
three-dimensional image depicted on the graphical display 160.
Fiduciary points are selected when the imaging catheter is at one
or more locations, and by combining this information with pullback
speed information, a location vs. time (or circumferential
cross-sectional image slice) path is determined for the imaging
probe mounted upon the catheter. Co-registering cross-sectional
IVUS with three-dimensional images of the type depicted in FIG. 6a
allows for a three-dimensional volumetric map of either gray scale
images or colorized tissue characterization (tissue composition)
images.
[0035] Turning to FIG. 6b, a set of steps are depicted for creating
a volumetric map. The particular order of the steps differs in
alternative embodiments. During step 162, the imaging catheter is
pulled back either manually or automatically through a blood vessel
segment, and a sequence of circumferential cross-sectional IVUS
image frames is acquired/created. During step 163 an angiographic
image is formed of the blood vessel segment. The image is, for
example, a two-dimensional image or, alternatively a
three-dimensional image created from two or more angiographic
views. During step 164, at least one fiduciary point is designated
on the angiographic image, either by the user, or automatically by
the imaging system. During step 166, the angiographic image and the
information obtained from the imaging catheter during the pullback
are aligned/correlated using the fiduciary point locating
information. Thereafter, during step 168 the cross-sectional IVUS
images are displayed on a graphical display in association with a
two- or three-dimensional graphical representation of the imaged
vessel. The graphical representation of the imaged vessel is based
at least in-part upon the angiographic image information. By way of
example, in an exemplary embodiment, the angiographic image itself
is displayed. In an alternative embodiment, information from an
angiographic image is only used to guide piece-wise reconstruction
of the imaged vessel from the sequence of IVUS image slices by
determining the linear displacement and orientation of adjacent
sections of the reconstructed vessel using the angiographic image
of the vessel.
[0036] Turning to FIG. 7, by combining or overlaying the
three-dimensional map of imaging information over the
three-dimensional image 160 of the vessel lumen, or over one or
more two-dimensional views of the angiogram, a reconstruction 165
that more realistically represents the actual vessel is obtained,
which is correct in its portrayal of vessel tortuosity, plaque
composition and associated location and distribution in three
dimensions. For example, a necrotic core which is located in the
vessel in the sector between 30.degree. to 90.degree., also having
a certain amount of longitudinal depth, will appear on the
reconstruction 165 with the same geometry. An augmented overall
vessel diameter, due to thickened plaque, will also appear this way
in the reconstruction 165. The additional information from the
non-angiography imaging data makes displaying such vessel images
possible. The steps of the procedure summarized in FIG. 6a
facilitate co-registration of the IVUS information over a live
two-dimensional angiographic image, giving the operator the ability
to view a projection of the volume of plaque over a two-dimensional
image of the lumen. The co-registered displayed graphical image
allows an operator to make a more informed diagnosis, and also
allows the operator to proceed with therapeutic intervention with
the additional information provided by the co-registered displayed
image guiding the intervention.
[0037] In the case of live two-dimensional or three-dimensional
co-registration, one or more fiduciary points are selected first,
followed by alignment by the system, and then simultaneous pullback
and angiography or fluoroscopy. Note that in both co-registration
in playback mode and co-registration in "live" mode, the
information used by the system includes both the specific pullback
speed being used (for example 0.5 millimeters per second) and the
time vector of the individual image frames (for example IVUS image
frames). This information tells the system where exactly the
imaging element is located longitudinally when the image frame is
(or was) acquired, and allows for the creation of an accurate
longitudinal map.
[0038] Automatic fiduciary points are used, for example, and are
automatically selected by the system in any one of multiple
potential methods. A radiopaque marker on the catheter,
approximating the location of the imaging element, for example is
identified by the angiography system, creating the fiduciary point.
Alternatively, the catheter has an electrode, which is identified
by three orthogonal pairs of external sensors whose relative
locations are known. By measuring field strength of an electrical
field generated by the probe, the location of the electrode is
"triangulated".
[0039] FIG. 7 graphically depicts a reconstruction produced using
the techniques discussed above. Three necrotic cores 80a, 80b and
80c have been identified. First necrotic core 80a is located at
twelve o'clock circumferentially in the vessel and is identified as
being located in the stenosis 60, and deep beneath a thickened cap.
The location of the necrotic core 80a beneath the thickened cap
suggests that this necrotic core is more stable than the other two
necrotic cores--core 80b which is very close to the surface, and
80c which is also close to the surface. As shown in this
reconstruction, and in relation to the first necrotic core 80a, the
second necrotic core 80b is located at nine o'clock and the third
necrotic core 80c is circumferentially located at four o'clock.
This circumferential information is employed, for example, to
localize application of appropriate treatment. The graphically
depicted information provided by the imaging catheter and
reconstruction allows delivery of the therapeutic catheter to the
precise treatment location, with the desired catheter orientation.
Alternatively, the imaging catheter itself is a combination imaging
and therapy catheter, and the treatment simultaneously coincides
with the imaging. One possible treatment scenario involves placing
a drug eluting stent at the portion of the depicted vessel near the
stenosis 60 and treating the second and third necrotic cores 80b
and 80c by a needle-based drug, cell (i.e. stem cell) or gene
delivery catheter (U.S. Pat. No. 6,860,867 to Seward), or by
removing the necrotic core material by a needle and vacuum
catheter. If using a tissue removal technique, such as atherectomy,
ultrasonic therapeutics, or a plaque modification technique such as
photodynamic therapy, drug delivery, radiation, cryoplasty,
radiofrequency heating, microwave heating or other types of
heating, the knowledge of the location of the EEL 50 is important.
This assures that the adventitia is not disturbed, and that vessel
perforation does not occur. The reconstruction 165 is graphically
displayed in a manner that clearly demonstrates the location of the
EEL 50 from all viewing angles. It can be seen that the thickness
170 between the luminal boundary and the EEL 50 at the stenosis 60
is much larger than the thickness 175 between the luminal boundary
and the EEL 50 proximal to the stenosis 60. The circumferential
(azimuthal) and radial (depth) orientation of the plaque components
has been discussed herein above, but the axial (longitudinal)
orientation/positioning--the distances separating diseased sections
along a vessel's length--is important also. First necrotic core 80a
is further distal than second necrotic core 80b, and second
necrotic core 80b is further distal than third necrotic core 80c.
The axial arrangement (lengthwise positioning) of diseased sections
is important when choosing a particular length of a stent to use,
or where to place the distal-most or proximal-most portion of the
stent. It is also important when determining the order or operation
in the treatment sequence. In addition, very proximally located
vulnerable plaques are generally of greater concern than distally
located vulnerable plaques, because they supply blood to a larger
volume of myocardium.
[0040] Arteries also have side branches which can be identified
with imaging techniques such as standard IVUS imaging, or IVUS flow
imaging (which identifies the dynamic element of blood). The side
branches are potentially used as fiduciary points for axial,
circumferential and even radial orientation of the IVUS
information, with respect to an angiographic base image, which also
contains side branch information.
[0041] Turning to FIGS. 14-20, an exemplary technique is
illustrated for obtaining accurate axial and circumferential
co-registration of IVUS information (or other image information
obtained via a probe inserted within a body) with the
three-dimensional image 160. Turning initially to FIG. 14 and FIG.
15, the illustrations are intended to represent the internal
representation of information created/processed by the
imaging/display system. However, in an illustrative embodiment,
such information is presented as well as graphical displays
rendered by the system, in the manner depicted in FIGS. 14 and 15
as a visual aid to users in a semi-automated environment. For
example, a user can manually move the relative positioning of a
sequence of IVUS frames with regard to linear displacement of a
vessel as depicted in corresponding data values generated from an
angiographic image.
[0042] Furthermore, as those skilled in the art will readily
appreciate, the line graphs in FIGS. 14 and 15 corresponding to
IVUS frames comprise a sequentially ordered set of discrete values
corresponding to a sequence of "N" frames of interest. Similarly,
values generated from angiographic image data are also taken at
discrete points along a length of a vessel of interest. Thus, while
depicted as continuous lines in the drawing figures, the values
calculated from angiographic and IVUS information correspond to
discrete points along the length of the vessel.
[0043] FIG. 14 includes a graph 320 depicting calculated/estimated
lumen area as a function of IVUS image frame number for both
angiography and IVUS. The graph depicted in FIG. 14 shows the
effect of inaccurate co-registration between two imaging methods
and associated measured parameters (e.g., lumen cross-section
size). A line graph 330 representing lumen area calculated from
IVUS information and a line graph 325 representing lumen area
calculated from angiography information are shown in an exemplary
case wherein the measurements are misaligned along a portion of a
vessel.
[0044] FIG. 14 corresponds to a graphically displayed composite
image depicted in FIG. 16 that includes a graphical representation
of a three-dimensional angiographic image 335 and a graphical
representation of corresponding IVUS information 340 where the two
graphical representations are shifted by a distance ("D") in a
composite displayed image. The misalignment is especially evident
because minimum luminal circumferential cross-section regions
(i.e., the portion of the vessel having the smallest cross-section)
in the images graphically rendered from each of the two data sets
do not line up. The minimal lumen area calculated from the IVUS
information at point 345 in FIG. 14 corresponds to the IVUS minimal
lumen position 360 in FIG. 16. The lumen area calculated from the
angiography information at point 350 in FIG. 14 corresponds to the
angiography minimal lumen position 355 in FIG. 16. Note that in the
illustrative example, thickness of the vessel wall is depicted as
substantially uniform on IVUS. Thus, an IVUS image frame where the
minimal lumen area occurs is also where the minimum vessel diameter
exists. This image feature differs from restricted flow due to a
blockage within a diseased artery such as the one depicted in FIG.
2.
[0045] A lumen border 380 is also shown in FIG. 16. In order to
achieve axial alignment between the graphical representation of the
three-dimensional angiographic image 335 and the graphical
representation of corresponding IVUS information 340, an axial
translation algorithm is obtained based upon a "best-fit" approach
that minimizes the sum of the squared differences between luminal
areas calculated using the angiographic and the IVUS image
data.
[0046] The best axial fit for establishing co-registration between
angiogram and IVUS data is obtained where the following function is
a minimum.
n = 1 N ( A Lumen - A Angio ) 2 ; ##EQU00001##
with A.sub.Lumen=IVUS lumen area for frames n=1, N and A.sub.Angio
angiography area for "frames" n=1, N (sections 1-N along the length
of an angiographic image of a blood vessel). By modifying how
particular portions of the angiographic image are selected, the
best fit algorithm can perform both "skewing" (shifting all slices
a same distance) and "warping" (modifying distances between
adjacent samples).
[0047] Using the axial alignment of frames where the summation
function is a minimum, a desired best fit is obtained. FIGS. 15 and
17 depict a result achieved by realignment of line graphs and
corresponding graphical representations generated from the
angiographic and IVUS data, depicted in a pre-aligned state in
FIGS. 14 and 16, based upon application of a "best fit" operation
on frames of IVUS image data and segments of a corresponding
angiographic image,
[0048] FIG. 18 illustratively depicts a graphical representation of
a three-dimensional lumen border 365 rendered from a sequence of
IVUS image slices after axially aligning a three-dimensional
angiographic data-based image with a graphical image generated from
IVUS information for a particular image slice. The displayed
graphical representation of a three dimensional image corresponds
to the lumen border 380 shown in FIG. 17. The lumen border 380 is
shown projected over a three-dimensional center line 385 obtained
from the angiographic information. FIG. 18 also depicts a first
angiography image plane 370 and a second angiography image plane
375 that are used to construct the three dimensional center line
385 and three-dimensional angiographic image 335. Such
three-dimensional reconstruction is accomplished in any one of a
variety of currently known methods. In order to optimize the
circumferential orientation of each IVUS frame, an IVUS frame 400
depicting a luminal border is projected against the first
angiography plane 370, where it is compared to a first
two-dimensional angiographic projection 390. In addition, or
alternatively, the IVUS frame 400 is projected against the second
angiography image plane 375, where it is compared to the second
two-dimensional angiographic projection 395 for fit. Such
comparisons are carried out in any of a variety of ways including:
human observation as well as automated methods for comparing lumen
cross section images (e.g., maximizing overlap between IVUS and
angiogram-based cross-sections of a vessel's lumen).
[0049] Positioning an IVUS frame on a proper segment of a graphical
representation of a three-dimensional angiographic image also
involves ensuring proper circumferential (rotational) alignment of
IVUS slices and corresponding sections of an angiographic image.
Turning to FIG. 19, after determining a best axial alignment
between an IVUS image frame, such as frame 400, and a corresponding
section of a three-dimensional angiographic image, the IVUS frame
400 is then rotated in the model by an angular displacement 405
(for example 1.degree.), and the fit against the angiographic
projections is recalculated. As mentioned above, either human or
automated comparisons are potentially used to determine the angular
displacement. After this has been done over a range of angular
orientations, the best fit angular rotation is determined.
[0050] FIG. 20 depicts a graph 410 of best angle fit and frame
number. During the pullback of the IVUS catheter, there may be some
slight rotation of the catheter, in relation to the centerline of
the blood vessel, and so, calculating the best angular fit for one
IVUS frame does not necessarily calculate the best fit for all
frames. The best angular fit is done for several or all frames in
order to create the graph 410 including actual line 412 and fit
line 414. The actual line 412 comprises a set of raw angular
rotation values when comparing IVUS and angiographic
circumferential cross-section images. The fit line 414 is rendered
by applying a limit on the amount of angular rotation differences
between adjacent frame slices (taking into consideration the
physical constraints of the catheter upon which the IVUS imaging
probe is mounted). By way of example, when generating the fit line
414, the amount of twisting between frames is constrained by
fitting a spline or a cubic polynomial to the plot on the actual
line 412 in graph 410.
[0051] Having described an illustrative way to co-register
angiographic and IVUS images for graphically representing a
three-dimensional image of a vessel, attention is directed to FIGS.
8a, 8b and 8c that demonstrate the use of a directional atherectomy
catheter 180 using guidance from the reconstruction 165. The
directional atherectomy catheter 180 has a tapered receptacle tip
190 and a cutter window 185. In use, the catheter is manipulated,
using a balloon or an articulation, to force the cutter window 185
against the atherosclerotic plaque so that the plaque protrudes
into the cutter window 185. The plaque is then sliced off by a
cutter (not shown) and collected in the tapered receptacle tip 190.
In order to debulk the artery as much as possible (remove the
plaque) it is desirable to cut away the plaque up to, but not past
the EEL 50. The reconstruction 165 is used as a guide to track the
directional atherectomy catheter 180 into a desired axial location
along the length of the vessel. Thereafter, the catheter 180 is
"torqued" (rotated at least partially) until the cutter window 185
is in the desired circumferential orientation. One in position the
balloon or articulation is activated until the cutter window 185 is
set up to allow the cutting of desired plaque but not adventitial
tissue. In other words, only tissue within the EEL 50 boundary is
excised.
[0052] With continued reference to FIG. 8a, using the reconstructed
co-registered angiographic and IVUS images as a guide for the
procedure, the directional atherectomy catheter 180 is tracked into
place and torqued opposite an upper portion 60a of the stenosis. In
FIG. 8b, an appropriate catheter mechanism, such as a balloon (not
shown) is activated to force the cutting window 185 against an
upper portion 60a of the stenosis. The upper portion 60a of the
stenosis is then excised. During this cutting operation, the
reconstruction procedure that achieves co-registration of the
angiographic and IVUS images on a graphical three-dimensional
rendering of a vessel allows the user to be fully aware of the
location of the EEL 50, and thus the user knows when to stop
articulating and cutting. FIG. 8c shows a directional atherectomy
catheter 180 being tracked, torqued and articulated so that it can
cut a lower portion 60b of the stenosis, again using a
co-registered IVUS cross-sectional image to avoid cutting past the
EEL 50 and into the adventitia 55 [Blair, need to add 55 to the
drawing 8c. This is especially useful in debulking areas of large
plaque volume, such as in the arteries of the leg (femoral,
popliteal). The debulking is performed using the vessel
visualization apparatus and methods described herein that are based
upon use of both angiographic and IVUS image data. Debulking or
other therapies may also be done using this smart visualization,
and in combination with automated or semi-automated robotic or
magnetic catheter manipulation systems.
[0053] Turning to FIG. 9, a dilatation balloon catheter 195 is
prepared based on information derived from the reconstruction 165
of FIG. 7. A first stent 200a, second stent 200b and third stent
200c are crimped onto the dilatation balloon catheter 195 or
attached by other methods known in the art. The first stent 200a is
configured to correspond with stenosis 60. The stent is made from a
mesh that has a higher metal to artery ratio than the other stents,
to prevent distal embolization from unorganized thrombus which may
occur near the flap 65. The stent may or may not be drug eluting.
For example, if the artery is 3.5 mm or larger, a drug eluting
stent is not always necessary to prevent restenosis. However, most
fiberatheromas will necessitate a drug eluting stent to prevent
in-stent restenosis. Because the first necrotic core 80a is deep
within the stenosis, the stent serves more as a mechanical support
for the entire dilated stenosis, rather than protection against
rupture of this portion of the blood vessel. In contrast, necrotic
cores 80b and 80c are closer to the lumen of the vessel and need to
be treated in a more urgent manner. Second stent 200b is configured
to be expanded over the second necrotic core 80b. A biodegradable
stent (such as magnesium or a polymeric material) may be chosen,
because it will be expanded in an area that does not require a high
radial force to keep the artery open (this is already a
non-stenotic area). The stent is designed to elute a statin, and
the statin is more heavily dosed at the nine o'clock portion (not
shown in FIG. 9) that corresponds with the second necrotic core
80b. The third stent 200c is the same as the second stent, 200b,
except that it is oriented on the catheter with the more heavily
dosed area 230 at four o'clock, in order to correspond with the
third necrotic core 80c. By more properly dosing the drugs on the
stents, there is less risk of wasted drug from high doses, being
leaked systemically into a patient's body, and potentially causing
harmful side effects. Not shown in this figure is another stent
configuration that has a side hole that allows the stent to be
placed over a sidebranch without obstructing flow of blood to the
sidebranch. The image co-registration reconstruction method and
apparatus described herein is also capable of identifying the size,
location and orientation of sidebranches, and can be used to orient
(circumferentially, axially) a sidehole stent of this design.
[0054] The catheter in FIG. 9 has four radiopaque markers
205a-205d, which delineate the positions of the three different
short stents 200a, 200b and 200c. The catheter also has radiopaque
markings or stripes that allow its circumferential orientation to
be visible on X-ray. For example, a radiopaque marker band that
does not completely encircle the catheter, so that visible portions
and non-visible portions can be identified around the circumference
of the marker.
[0055] FIG. 10 shows an overlay 235 of the reconstruction 165
placed over the live anigiography image 240. As a catheter is
tracked through the vessel, the atherosclerotic plaque 225 and the
EEL 220 is identified. In combination with tissue characterization
and colorization, structures of concern 245 are easily identified
in relation to the live image 240. Sidebranches 250 are used, for
example, to align and co-register the two different images.
Combining the three-dimensional reconstruction with tissue
characterization information and a live two-dimensional angiography
image, facilitate tracking and manipulating a therapeutic catheter
(not shown) to areas that are of primary concern. It also allows
for a more informed awareness of the state of vulnerability of
various regions of the vessel. In the stenosis, target plaque 255
is viewed against a live two-dimensional angiography image to
better aid plaque removal techniques, such as directional
atherectomy.
[0056] FIGS. 11, 12 and 13 illustratively depict three different
graphic displays for graphically representing information relating
to plaque size and composition. A vessel lumen trace 260 is, for
example, either a three-dimensional rendering of the vessel lumen
(for example derived from two two-dimensional angiography images)
or a two-dimensional projection of the three dimensional rendering.
Alternatively, vessel lumen trace 260 is represented by a live
angiographic image. In all of the aforementioned alternative
angiographic imaging modes, it is possible to overlay images of the
atherosclerotic plaque, however, it is difficult to appreciate the
thickness, contours and composition of the plaque at all points
extending circumferentially around the vessel by simply looking at
a single projection.
[0057] FIG. 11 is a graphical image representation that embodies a
technique that utilizes information calculated from IVUS imaging
(or other imaging) and places a maximum thickness line 265 and a
minimum thickness line 270 above and below the trace. Though not
specific of where, circumferentially, the thickest portion of
plaque occurs, the maximum thickness line 265 shows the exact
maximum thickness of the plaque at each longitudinal position along
the artery. In other words, a curving, continuous central axis
parameter 275 follows the centerline of the artery and represents
the axial location of the plaque, while a perpendicular axis
parameter 280 represents the maximum thickness of the plaque by its
distance from the edge of the vessel lumen trace 260. In a similar
manner, the minimum thickness line 270 represents the minimum
thickness of the plaque in the negative direction. It can be
appreciated immediately while viewing the image/graphic combination
depicted in FIG. 11 that the plaque is eccentric at various
sections, even though there is no information present in this
image/graphic combination to identify the exact circumferential
angle where the maximum plaque thickness occurs. By viewing this
image/graphic combination, the operator can immediately focus on
the areas where the plaque is more eccentric, and the operator can
also get a measurement of the minimum and maximum plaque
thickness.
[0058] FIG. 12 illustratively depicts a graphical technique similar
to that of FIG. 11, but with more specific information, namely the
volume of plaque composition over a chosen length of vessel. A bar
graph 285 is placed along-side the vessel lumen trace 260, and
represents the volume of the different plaque components over a
length of vessel. The user picks the proximal and distal point on
the vessel which define a region of interest (for example a
possible area of vulnerability), and the data obtained in this area
is displayed with the bar graph 285. The bar graph 285 in this case
represents four plaque components, fibrous 290, fibro-fatty 295,
necrotic core 300, and dense calcium 305. The thickness (height in
the radial direction) of each individual bar is proportional to the
volume of that plaque component measured in a visually
designated/indicated length of vessel. Each bar is color coded with
a characteristic color to allow easier visual identification. For
example, fibrous-dark green, fibrofatty-light green, necrotic
core-red, dense calcium-white.
[0059] FIG. 13 illustratively depicts a graphical technique that is
very similar to the one described in FIG. 11; however, instead of
describing maximum and minimum plaque thickness at each axial
location, the actual plaque thickness at each of the two sides is
graphed. When the vessel lumen trace 260 is displayed in a
two-dimensional mode, the upper thickness line 310 and the lower
thickness line 315 graph the thickness of the plaque at points
180.degree. from each other (for example at twelve o'clock and six
o'clock), depending on the orientation chosen for the vessel lumen
trace 260.
[0060] The invention described herein is not limited to
intravascular applications or even intraluminal applications.
Tissue characterization is also possible in cancer diagnostics, and
it is conceivable that a probe that images for cancer can also be
used in conjunction with a three-dimensional map to create a
similar reconstruction as that described above. This can be used to
guide biopsy or removal techniques. Such cancers include, but are
not limited to: prostate, ovarian, lung, colon and breast. In the
intravascular applications, both arterial and venous imaging is
conceived. Arteries of interest include, by way of example:
coronaries, carotids, superficial femoral, common femoral, iliac,
renal, cerebral and other peripheral and non-peripheral
arteries.
[0061] The intravascular ultrasound methods described can also be
expected to be applicable for other ultrasound applications, such
as intracardiac echocardiography (ICE) or transesophageal
echocardiography (TEE). Therapeutic techniques that are guided by
these techniques include, but are not limited to, patent foramen
ovale closure, atrial septal defect closure, ventricular septal
defect closure, left atrial appendage occlusion, cardiac biopsy,
valvuloplasty, percutaneous valve placement, trans-septal puncture,
atrial fibrillation ablation (of pulmonary veins or left atrium,
for example) and TIPS (transjugular intrahepatic portosystemic
shunt for pulmonary hypertension).
[0062] Similar to the selective use of directional atherectomy and
stenting/drugs in the circumferential, radial and axial
orientations, the other energy delivery methods can also be
manipulated as such. For example, in a thicker plaque, a higher
power can be used in a cryogenic cooling catheter, etc. In
addition, image guided automatic feedback can be used to
automatically determine when to apply energy and when to stop
applying energy, based on the information in the reconstruction.
This is particularly of use in radiofrequency ablation of pulmonary
veins for treatment of atrial fibrillation.
[0063] All of the image guided therapy described in this invention,
can be conceived to be a combination of imaging and therapy on the
same catheter, or to be two or more different catheters, each
specialized in its use.
[0064] All of the techniques described here can also be used in
conjunction with external imaging technologies such as MRI, CT,
X-ray/angiography and ultrasound. Three dimensional
reconstructions, for example from CT or MRI, can be co-registered
with the imaging information in the same way as angiography.
[0065] The three-dimensional mapping of imaging information can
also be combined with a three dimensional mapping of the electrical
activity of the heart, for example, from information obtained from
catheter-based electrodes. This is of use in a patient that has had
an acute myocardial infarction.
[0066] It is also conceivable to include three-dimensional fluid
mechanics analysis in the reconstruction so that points of high
stress are identified.
[0067] The structures, techniques, and benefits discussed above,
for illustrative systems embodying the present invention, are
exemplary. In view of the many possible embodiments to which the
principles of this invention may be applied, it should be
recognized that the embodiments described herein with respect to
the drawing figures are meant to be illustrative only and should
not be taken as limiting the scope of the invention. Therefore, the
invention as described herein contemplates all such embodiments as
may come within the scope of the following claims and equivalents
thereof.
* * * * *