U.S. patent application number 09/732614 was filed with the patent office on 2002-06-13 for analysis of cardiac performance using ultrasonic diagnostic images.
Invention is credited to Chenal, Cedric, Criton, Aline Laure, Roundhill, David N..
Application Number | 20020072672 09/732614 |
Document ID | / |
Family ID | 24944268 |
Filed Date | 2002-06-13 |
United States Patent
Application |
20020072672 |
Kind Code |
A1 |
Roundhill, David N. ; et
al. |
June 13, 2002 |
Analysis of cardiac performance using ultrasonic diagnostic
images
Abstract
Ultrasonic cardiac image information is acquired and segmented
by automatic border detection. The segmented ultrasonic information
is used to display regional wall motion over time. The segmented
information may be presented in a color-coded representation, or
entered automatically as qualitative or quantitative measures on a
scorecard of cardiac performance. The inventive technique is
applicable to both two dimensional and three dimensional ultrasonic
image information.
Inventors: |
Roundhill, David N.;
(Woodinville, WA) ; Chenal, Cedric; (Kirkland,
WA) ; Criton, Aline Laure; (Seattle, WA) |
Correspondence
Address: |
ATL ULTRASOUND
P.O. BOX 3003
22100 BOTHELL EVERETT HIGHWAY
BOTHELL
WA
98041-3003
US
|
Family ID: |
24944268 |
Appl. No.: |
09/732614 |
Filed: |
December 7, 2000 |
Current U.S.
Class: |
600/450 ;
600/454 |
Current CPC
Class: |
A61B 8/0891 20130101;
A61B 8/0858 20130101; A61B 8/485 20130101; A61B 8/0883 20130101;
A61B 8/483 20130101 |
Class at
Publication: |
600/450 ;
600/454 |
International
Class: |
A61B 008/02; A61B
008/12 |
Claims
What is claimed is:
1. A method for displaying information derived by automatic border
detection in cardiac ultrasound images comprising: acquiring a
sequence of cardiac ultrasound images; automatically tracing a
border of moving tissue in each of the images; computing motion
along each of the traced borders; and displaying the computed
motion along the traced borders as a function of time and
location.
2. The method of claim 1, wherein the border tracings are
nonlinear, and wherein the computed motion along each traced border
is displayed linearly.
3. The method of claim 1, wherein the computed motion is displayed
in colors corresponding to velocity.
4. The method of claim 1, wherein the border traced is the
endocardium.
5. The method of claim 1, wherein the border traced is the
epicardium.
6. The method of claim 1, wherein the tracing is offset from the
endocardium in the direction of the epicardium.
7. The method of claim 1, further comprising: automatically
tracking corresponding anatomical points on each of the borders
from image to image; and displaying the motion of the corresponding
anatomical points in spatial correspondence on a display.
8. The method of claim 7, wherein automatically tracking comprises
tracking the speckle patterns of anatomical points along borders of
the images.
9. The method of claim 7, wherein automatically tracking comprises
tracking the tissue patterns of anatomical points along borders of
the images.
10. The method of claim 1, further comprising manually adjusting
one or more of the automatically traced borders.
11. The method of claim 1, wherein time is shown along one axis and
location on the border is shown along the other axis.
12. A method for analyzing cardiac performance by automatic border
detection in cardiac ultrasound images comprising: acquiring a
sequence of cardiac ultrasound images; automatically tracing a
border of the heart in one or more images; segmenting the
myocardium along each of the traced borders; and analyzing the
ultrasound information of one or more myocardial segments.
13. The method of claim 12, wherein analyzing comprises quantifying
wall motion for the myocardial segments, wherein quantified wall
motion is displayed in the myocardial segments by colors indicating
regional wall motion.
14. The method of claim 12, wherein analyzing comprises computing
scores for the myocardial segments; and further comprising:
automatically entering the scores on a scorecard having entries
relating to the myocardial segments.
15. The method of claim 14, wherein the scorecard comprises an
electronic scorecard.
16. The method of claim 15, wherein the scorecard comprises a
bullet scorecard having entries corresponding to segments of the
heart wall.
17. The method of claim 15, wherein the scorecard comprises an
anatomical representation of the myocardium.
18. The method of claim 15, wherein the entries comprise
alphanumeric entries.
19. The method of claim 15, wherein the entries comprise colored or
shaded entries.
20. The method of claim 12, wherein acquiring comprises acquiring a
three dimensional image of the heart; and wherein automatically
tracing comprises automatically delineating the heart wall in a
three dimensional image.
21. The method of claim 20, wherein analyzing comprises quantifying
wall motion for myocardial segments of the three dimensional image,
wherein quantified wall motion is displayed in the three
dimensional image by colors indicating wall motion.
22. The method of claim 20, wherein analyzing comprises computing
scores for myocardial segments of the three dimensional image; and
further comprising: automatically entering scores on a scorecard
having entries relating to the myocardial segments.
23. The method of claim 22, wherein the scorecard comprises an
electronic scorecard having areas corresponding to areas of the
heart wall delineated in the three dimensional image.
24. A method for analyzing cardiac performance by automatic border
detection in cardiac ultrasound images comprising: acquiring two or
more images in different image planes which intersect a chamber of
the heart; automatically tracing a border of the heart in each of
the images; and analyzing cardiac performance in regions of the
heart delineated by the automatically traced borders.
25. The method of claim 24, wherein acquiring further comprises
acquiring ultrasonic signals by gated acquisition.
26. The method of claim 25, wherein acquiring further comprises
acquiring ultrasonic signals by electronic beam steering.
27. The method of claim 25, wherein acquiring further comprises
acquiring ultrasonic signals by mechanical beam steering.
28. The method of claim 24, wherein analyzing comprises computing
and displaying regional wall motion along each of the automatically
traced borders.
29. The method of claim 24, wherein analyzing comprises computing
scores for delineated regions of the heart wall; and further
comprising: automatically entering scores on a scorecard having
entries relating to the heart wall regions.
30. The method of claim 29, wherein the scorecard comprises an
electronic scorecard having entries corresponding to regions of the
heart wall.
31. A method for displaying measures of cardiac performance by
automatic border detection in cardiac ultrasound images comprising:
acquiring three dimensional ultrasonic image data of a chamber of
the heart; automatically tracing a border of the heart in the three
dimensional ultrasonic data; and displaying in three dimensions a
region of the heart delineated by the border.
32. The method of claim 31, wherein acquiring further comprises
acquiring three dimensional motion data of the heart chamber; and
wherein displaying comprises displaying motional data of a region
of the heart delineated by the border.
33. The method of claim 32, wherein the region of the heart
comprises the heart wall.
34. The method of claim 31, wherein displaying further comprises
displaying in two dimensions the region of the heart delineated by
the border.
35. The method of claim 34, wherein displaying further comprises
displaying in two dimensions motional ultrasonic information of the
region of the heart delineated by the border.
36. The method of claim 31, further comprising delineating a region
of interest on the displayed region of the heart.
37. A method for displaying information derived by automatic border
detection in cardiac ultrasound images comprising: acquiring a
sequence of cardiac ultrasound images; automatically tracing a
border of moving tissue in each of the images; computing motion
along each of the traced borders utilizing harmonic signal
information corresponding to the traced borders; and displaying the
computed motion along the traced borders as a function of time and
location.
38. The method of claim 37, wherein computing comprises computing
motion along the traced borders by Doppler processing harmonic
signal information from moving tissue.
39. A method for analyzing cardiac performance by automatic border
detection in cardiac ultrasound images comprising: acquiring a
sequence of cardiac ultrasound images; automatically tracing a
border of the heart in the cardiac images; segmenting the
myocardium along each of the traced borders; computing scores for
the myocardial segments; and automatically entering the scores on
scorecards having entries relating to the myocardial segments.
40. The method of claim 39, further comprising displaying the
scorecards on a display in rapid time succession.
41. The method of claim 40, wherein rapid time succession is one of
faster than, slower than, or equal to the real time display rate of
the cardiac ultrasound images.
Description
[0001] This invention relates to ultrasonic diagnostic imaging
systems and, in particular, to ultrasonic diagnostic imaging
systems which automatically assist in the assessment of cardiac
performance and deficiencies.
[0002] Many ultrasonic diagnostic procedures in which bodily
functions and structures are quantified rely upon clear delineation
and definition of the body structures and organs which are being
measured. When the quantification or measurement procedure uses
static images or a small set of measurements, the delineation of
the bodily structure being measured can be done manually. An
example of such a procedure is the obstetrical measurements of a
developing fetus. Static images of the developing fetus can be
acquired during periods when fetal activity is low. Once an image
is acquired, only a few circumference or length measurements are
usually required to compute development characteristics such as
gestational age and anticipated delivery date. These measurements
can readily be made manually on the fetal images. Other diagnostic
procedures, particularly those involving measurements of the heart
and its functioning, present a further set of difficulties. The
heart is always beating and hence is always in motion. As it moves,
the contours of the heart constantly move and change as the organ
contracts and expands. To fully assess many characteristics of
cardiac function it is necessary to evaluate many and at times all
of the images acquired during the heart cycle (one heartbeat),
which can amount to thirty to one hundred and fifty or more images.
The structure of interest such as the endocardium, epicardium or
valves must then be delineated in each of these images, a
painstaking, time-consuming task. Since these structures are
constantly in motion, they appear slightly different in each image
acquired during the cardiac cycle, and can also vary significantly
from one patient to another. While applications such as obstetrical
procedures would benefit from a processor which automatically
delineates specific anatomy in an ultrasonic image, cardiac
diagnosis would benefit even more so.
[0003] Once anatomy can automatically be delineated in cardiac
images, it then becomes desirable how to make the best diagnostic
use of the delineated image information. It is desirable, for
instance, to convey a sense of regional wall motion but in a format
which enables the user to specifically diagnose particular
locations of the heart wall and to be able to do so over the full
cardiac cycle. Furthermore, it is desirable to give the user a
visual, automated assessment of regional cardiac performance,
enabling the user to quickly pinpoint and thereafter examine
potentially deficient regions of the heart.
[0004] In accordance with the principles of the present invention,
ultrasonic cardiac image information is acquired and segmented by
automatic border detection. The segmented ultrasonic information is
used to display regional wall motion over time. The segmented
information may be presented in a color-coded representation, or
entered automatically as qualitative or quantitative measures on a
scorecard of cardiac performance. The inventive technique is
applicable to both two dimensional and three dimensional ultrasonic
image information.
[0005] In the drawings:
[0006] FIG. 1 is a four chamber ultrasound image of the heart;
[0007] FIG. 2 illustrates an ultrasound display of both end
diastole and end systole cardiac images;
[0008] FIGS. 3a and 3b illustrate the step of locating the medial
mitral annulus (MMA) and the lateral mitral annulus (LMA) in an
ultrasound image of the left ventricle (LV);
[0009] FIG. 4 illustrates the step of locating the apex of the
LV;
[0010] FIGS. 5a-5c illustrate standard border shapes for the
LV;
[0011] FIGS. 6a-6b illustrate geometric templates used to locate
the MMA and LMA;
[0012] FIGS. 7a-7c illustrate a technique for fitting a standard
border shape to the endocardial boundary of the LV;
[0013] FIG. 8 illustrates an end diastole and end systole display
with endocardial borders drawn automatically in accordance with the
principles of the present invention;
[0014] FIG. 9 illustrates the rubber-banding technique for
adjusting an automatically drawn border;
[0015] FIG. 10 illustrates the selection of a cardiac cycle by
viewing automatically drawn borders;
[0016] FIG. 11 illustrates a tissue Doppler map of endocardial
motion over a plurality of cardiac cycles;
[0017] FIGS. 12 illustrates the use of automated border detection
to segment an image of the heart wall;
[0018] FIGS. 13a and 13b illustrate scorecards for scoring segments
of the heart wall;
[0019] FIGS. 14a and 14b illustrate techniques for making strain
rate measurements as a function of tissue motion;
[0020] FIGS. 15a-15c illustrate 3D techniques for evaluating
cardiac performance;
[0021] FIG. 15d illustrates a scorecard for scoring a three
dimensional image of the heart; and
[0022] FIG. 16 illustrates in block diagram form an ultrasonic
diagnostic imaging system constructed in accordance with the
principles of the present invention.
[0023] Referring first to FIG. 1, an ultrasound system display is
shown during the acquisition of cardiac images. The ultrasound
image 10 is a four-chamber view of the heart which is acquired by a
phased array transducer probe to produce the illustrated
sector-shaped image. The image shown is one of a sequence of
real-time images acquired by placement of the probe for an apical
4-chamber view of the heart, in which the probe is oriented to view
the heart from the proximity of its apex 11. The largest chamber in
the image, in the central and upper right portion of the image, is
the left ventricle (LV). As the real-time ultrasound image sequence
is acquired an ECG trace 12 of the heart cycle is simultaneously
acquired and displayed at the bottom of the display, with a
triangular marker 14 denoting the point or phase of the cardiac
cycle at which the currently-displayed image was acquired. A
typical duration of the heart cycle when the body is at rest is
about one second, during which time approximately 30-90 image
frames of the heart are acquired and displayed in rapid succession.
A sequence of image frames for a heart cycle is referred to herein
as a "loop" of images, as a clinician will often acquire and save
the sequence of images of a heart cycle and then replay them in a
continuous "loop" which repetitively displays the selected cardiac
cycle. As the clinician views the display of FIG. 1, the heart is
seen beating in real time in the ultrasound display as the ECG
waveform 12 scrolls beneath the ultrasound images 10, with the
instantaneously displayed heart phase indicated by the marker
14.
[0024] In one mode of acquisition in accordance with the present
invention, the clinician observes the beating heart in real time
while manipulating the transducer probe so that the LV is being
viewed distinctly in maximal cross-section. When the four chamber
view is being acquired continuously and clearly, the clinician
depresses the "freeze" button to retain the images of the current
heart cycle in the image frame or Cineloop.RTM. memory of the
ultrasound system. The Cineloop memory will retain all of the
images in the memory at the time the freeze button is depressed
which, depending upon the size of the memory, may include the loop
being viewed at the time the button was depressed as well as images
of a previous or subsequent loop. A typical Cineloop memory may
hold 400 image frames, or images from about eight to ten heart
cycles. The clinician can then scan through the stored images with
a trackball, arrow key, or similar control to select the loop with
the images best suited for analysis. When the clinician settles on
a particular loop, the "ABD" protocol is actuated to start the
border drawing process.
[0025] When the ABD protocol is actuated the display changes to a
dual display of the end diastole image 16 and the end systole image
18 displayed side-by-side as shown in FIG. 2. The ultrasound system
identifies all of the images comprising the selected loop by the
duration of the ECG waveform associated with the selected loop. The
ultrasound system also recognizes the end diastole and end systole
points of the cardiac cycle in relation to the R-wave of the ECG
waveform 12 and thus uses the ECG waveform R-wave to identify and
display the ultrasound images at these two phases of the heart
cycle. The dual display of FIG. 2 shows the ECG waveform 12 for the
selected heart cycle beneath each ultrasound image, with the marker
14 indicating the end diastole and end systole phases at which the
two displayed images were acquired.
[0026] Since the Cineloop memory retains all of the images of the
cardiac cycle, the user has the option to review all of the images
in the loop, including those preceding and succeeding those shown
in the dual display. For instance, the clinician can "click" on
either of the images to select it, then can manipulate the
trackball or other control to sequentially review the images which
precede or succeed the one selected by the ultrasound system. Thus,
the clinician can select an earlier or later end diastole or end
systole image from those selected by the ultrasound system. When
the clinician is satisfied with the displayed images 16 and 18, the
ABD processor is actuated to automatically delineate the LV borders
on the two displayed images as well as the intervening undisplayed
images between end diastole and end systole.
[0027] In this example the ABD processor begins by drawing the
endocardial border of the LV in the end systole image 18. The first
step in drawing the border of the LV is to locate three key
landmarks in the image, the medial mitral annulus (MMA), the
lateral mitral annulus (LMA), and the endocardial apex. This
process begins by defining a search area for the MMA as shown in
FIG. 3a, in which the ultrasound image grayscale is reversed from
white to black for ease of illustration. Since the ABD processor is
preconditioned in this example to analyze four-chamber views of the
heart with the transducer 20 viewing the heart from its apex, the
processor expects the brightest vertical nearfield structure in the
center of the image to be the septum which separates the left and
right ventricles. This means that the column of pixels in the image
with the greatest total brightness value should define the septum.
With these cues the ABD processor locates the septum 22, and then
defines an area in which the MMA should be identified. This area is
defined from empirical knowledge of the approximate depth of the
mitral valve from the transducer in an apical view of the heart. A
search area such as that enclosed by the box 24 in FIG. 3a is
defined in this manner.
[0028] A filter template defining the anticipated shape of the MMA
is then cross correlated to the pixels in the MMA search area.
While this template may be created from expert knowledge of the
appearance of the MMA in other four-chamber images as used by
Wilson et al. in their paper "Automated analysis of
echocardiographic apical 4-chamber images," Proc. of SPIE, August,
2000, the present inventors prefer to use a geometric corner
template. While a right-angle corner template may be employed, in a
constructed embodiment the present inventors use an octagon corner
template 28 (the lower left corner of an octagon) as their search
template for the MMA, as shown at the right side of FIG. 6a. In
practice, the octagon template is represented by the binary matrix
shown at the left side of FIG. 6a. The ABD processor performs
template matching by cross correlating different sizes of this
template with the pixel data in different translations and
rotations until a maximum correlation coefficient above a
predetermined threshold is found. To speed up the correlation
process, the template matching may initially be performed on a
reduced resolution form of the image, which highlights major
structures and may be produced by decimating the original image
resolution. When an initial match of the template is found, the
resolution may be progressively restored to its original quality
and the location of the MMA progressively refined by template
matching at each resolution level.
[0029] Once the MMA has been located a similar search is made for
the location of the LMA, as shown in FIG. 3b. The small box 26
marks the location established for the MMA in the image 18, and a
search area to the right of the MMA is defined as indicated by the
box 34. A right corner geometric template, preferably a right
octagon corner template 38 as shown in FIG. 6b, is matched by
cross-correlation to the pixel values in the search area of box 34.
Again, the image resolution may be decimated to speed the
computational process and different template sizes may be used. The
maximal correlation coefficient exceeding a predetermined threshold
defines the location of the LMA.
[0030] With the MMA 26 and the LMA 36 found, the next step in the
process is to determine the position of the endocardial apex, which
may be determined as shown in FIG. 4. The pixel values of the upper
half of the septum 22 are analyzed to identify the nominal angle of
the upper half of the septum, as indicated by the broken line 43.
The pixel values of the lateral wall 42 of the LV are analyzed to
identify the nominal angle of the upper half of the lateral wall
42, as shown by the broken line 45. If the lateral wall angle
cannot be found with confidence, the angle of the scanlines on the
right side of the sector is used. The angle between the broken
lines 43, 45 is bisected by a line 48, and the apex is initially
assumed to be located at some point on this line. With the
horizontal coordinate of the apex defined by line 48, a search is
made of the slope of pixel intensity changes along the line 48 to
determine the vertical coordinate of the apex. This search is made
over a portion of line 48 which is at least a minimum depth and not
greater than a maximum depth from the transducer probe,
approximately the upper one-quarter of the length of line 48 above
the mitral valve plane between the MMA 26 and the LMA 36. Lines of
pixels along the line 48 and parallel thereto are examined to find
the maximum positive brightness gradient from the LV chamber (where
there are substantially no specular reflectors) to the heart wall
(where many reflectors are located). A preferred technique for
finding this gradient is illustrated in FIG. 7. FIG. 7a shows a
portion of an ultrasound image including a section of the heart
wall 50 represented by the brighter pixels in the image. Drawn
normal to the heart wall 50 is a line 48 which, from right to left,
extends from the chamber of the LV into and through the heart wall
50. If the pixel values along line 48 are plotted graphically, they
would appear as shown by curve 52 in FIG. 7b, in which brighter
pixels have greater pixel values. The location of the endocardium
is not the peak of the curve 52, which is in the vicinity of the
center of the heart wall, but relates to the sense of the slope of
the curve. The slope of the curve 52 is therefore analyzed by
computing the differential of the curve 52 as shown by the curve 58
in FIG. 7c. This differential curve has a peak 56 which is the
maximal negative slope at the outside of the heart wall (the
epicardium). The peak 54, which is the first major peak encountered
when proceeding from right to left along curve 58, is the maximal
positive slope which is the approximate location of the
endocardium. The pixels along and parallel to line 48 in FIG. 4 are
analyzed in this manner to find the endocardial wall and hence the
location of the endocardial apex, marked by the small box 46 in
FIG. 4.
[0031] Once these three major landmarks of the LV have been
located, one of a number of predetermined standard shapes for the
LV is fitted to the three landmarks and the endocardial wall. Three
such standard shapes are shown in FIGS. 5a, 5b, and 5c. The first
shape, border 62, is seen to be relatively tall and curved to the
left. The second shape, border 64, is seen to be relatively short
and rounded. The third shape, border 66, is more triangular. Each
of these standard shapes is scaled appropriately to fit the three
landmarks 26, 36, 46. After an appropriately scaled standard shape
is fit to the three landmarks, an analysis is made of the degree to
which the shape fits the border in the echo data. This may be done,
for example, by measuring the distances between the shape and the
heart wall at points along the shape. Such measurements are made
along paths orthogonal to the shape and extending from points along
the shape. The heart wall may be detected using the operation
discussed in FIGS. 7a-7c, for instance. The shape which is assessed
as having the closest fit to the border to be traced, by an average
of the distance measurements, for instance, is chosen as the shape
used in the continuation of the protocol.
[0032] The chosen shape is then fitted to the border to be traced
by "stretching" the shape, in this example, to the endocardial
wall. The stretching is done by analyzing 48 lines of pixels evenly
spaced around the border and approximately normal to heart wall.
The pixels along each of the 48 lines are analyzed as shown in
FIGS. 7a-7c to find the adjacent endocardial wall and the chosen
shape is stretched to fit the endocardial wall. The baseline
between points 26 and 36 is not fit to the shape but is left as a
straight line, as this is the nominal plane of the mitral valve.
When the shape has been fit to points along the heart wall, the
border tracing is smoothed and displayed over the end systole image
as shown in the image 78 on the right side of the dual display of
FIG. 8. The display includes five control points shown as X's along
the border between the MMA landmark and the apex, and five control
points also shown as X's along the border between the apex landmark
and the LMA landmark. In this example the portion of line 48
between the apex and the mitral valve plane is also shown, as
adjusted by the stretching operation.
[0033] With the end systole border drawn in this manner the ABD
processor now proceeds to determine the end diastole border. It
does so, not by repeating this operation on the end diastole image
16, but by finding a border on each intervening image in sequence
between end systole and end diastole. In a given image sequence
this may comprise 2030 image frames. Since this is the reverse of
the sequence in which the images were acquired, there will only be
incremental changes in the endocardial border location from one
image to the next. It is therefore to be expected that there will
be a relatively high correlation between successive images. Hence,
the end systole border is used as the starting location to find the
border for the previous image, the border thus found for the
previous image is used as the starting location to find the border
for the next previous image, and so forth. In a constructed
embodiment this is done by saving a small portion of the end
systole image around the MMA and the LMA and using this image
portion as a template to correlate and match with the immediately
previous image to find the MMA and the LMA locations in the
immediately previous image. The apex is located as before, by
bisecting the angle between the upper portions of the septum and
lateral LV wall, then locating the endocardium by the maximum slope
of the brightness gradient. Since the LV is expanding when
proceeding from systole to diastole, confidence measures include
the displacement of the landmark points in an outward direction
from frame to frame. When the three landmark points are found in a
frame, the appropriately scaled standard shape is fit to the three
points. Another confidence measure is distention of the standard
shapes; if a drawn LV border departs too far from a standard shape,
the process is aborted.
[0034] Border delineation continues in this manner until the end
diastole image is processed and its endocardial border defined. The
dual display then appears as shown in FIG. 8, with endocardial
borders drawn on both the end diastole and end systole images 76,
78.
[0035] As FIG. 8 shows, the endocardial borders of both the end
diastole and end systole images have small boxes denoting the three
major landmarks and control points marked by X's on the septal and
lateral borders. The clinician chooses the default number of
control point which will be displayed initially; on the border 80
shown in FIG. 9 there are three control points shown on the septal
wall and four control points shown on the lateral wall. The
clinician can review the end diastole and systole images, as well
as all of the intervening images of the loop if desired, and
manually adjust the positions of the landmark boxes and control
point X's if it is seen that the automated process placed a border
in an incorrect position. The clinician can slide a box or X along
the border to a new position, and can add more control points or
delete control points from the border. The process by which the
clinician relocates a box or X laterally is known as rubberbanding.
Suppose that the ABD processor had initially located the control
point and border at the position shown by circle 82 and dashed line
84, which the clinician observes is incorrect. The clinician can
relocate the control point laterally by dragging the X with a
screen pointing device to the new location as shown by 86. As the X
is dragged, the border moves or stretches along with the X, thereby
defining a new border as shown by the solid line border 88. In this
manner the clinician can manually correct and adjust the borders
drawn by the ABD processor. As the clinician laterally relocates a
control point X, the ABD processor responds by automatically
recalculating the positions of the adjoining border and adjacent
control points if necessary so that the border remains smoothly
continuous. The recalculation will not adjust the position of a
control point or landmark box which has been previously manually
repositioned by the clinician, thereby preserving this expert input
into the border drawing process. If the clinician relocates a
landmark box, the ABD processor recalculates and refits the entire
border to the landmarks and heart wall. Since the adjustment of one
border in the image sequence can affect the borders of temporally
adjacent images in the sequence, the ABD processor will also
respond to a manual adjustment by correlating the adjusted border
with temporally adjacent borders so that the manual adjustment is
properly continuously represented in some or all of the images in
the loop.
[0036] Another way to interactively adjust the drawn borders is to
assemble only the border tracings in a "stack" in time sequence
from ED to ES or later to form a surface defined by the borders
which is viewed in three dimensions such as in a kinetic parallax
display. The continuous surface formed by the borders can be
assessed and adjusted as desired by a rubberbanding technique know
as active surface adjustment. If the clinician sees a point on the
surface formed by the borders which is out of alignment with
temporally adjacent tracings or the desired border, the clinician
can pull or push on the surface with a pointing device. The active
surface adjustment then conforms the adjacent borders and the
surface defined thereby to the adjustment made by the clinician,
much as a balloon conforms when depressed at a point on its
surface. The clinician can thus observe the effect of an adjustment
made to one border on the temporally surrounding borders of the
cardiac cycle.
[0037] In a preferred embodiment the control points are not simply
distributed at uniform intervals around the drawn border, but their
positions correspond to constant anatomical locations from frame to
frame over the heart cycle. This may be done by referencing the
control points of the image to those of a reference image through
speckle tracking, feature tracking, or any kind of vector velocity
or displacement processing. Since points in anatomy shown in an
ultrasound image will exhibit a substantially constant pattern of
speckle from frame to frame, the control points in other images can
be located at points on their respective drawn borders which
correspond to their characteristic speckle locations on the
reference image. When the control points are located at constant
anatomical positions they will appear to move closer together and
then further apart through the heart cycle as the heart wall
contracts and expands. When a control point X is relocated on a
border by the clinician, the corresponding control point X's on the
other images are correspondingly relocated automatically to the new
speckle-tracked locations on each image. Such constant anatomical
locations for the control points are important when assessing local
heart wall motion as discussed below.
[0038] Since each of the images shown in FIG. 8 is one image in the
cardiac loop of images, the clinician can further verify the
accuracy of the borders of the end diastole and end systole images
76, 78 by playing the cardiac loop of images behind the borders
drawn on the display of FIG. 8. This is done by selecting one of
the images of FIG. 8, then selecting "Play" from the system menu to
repetitively play the cardiac loop in real time or at a selected
frame rate of display behind the border. In the end diastole image
76 the endocardium is at its maximum expansion; hence, the
endocardium in the loop should appear to move inward from and then
back to the endocardial border drawn on the end diastole image. In
the end systole image 78 the endocardium is fully contracted;
hence, the endocardium in the loop should appear to move outward
and then back to the border in this image. If the endocardium does
not move in this manner and, for example, is seen to pass through
the border, a different image may need to be chosen for end
diastole or end systole, or manual adjustment of a drawn border may
be necessary. Of course, the loop and its drawn borders over the
complete cardiac cycle can be replayed, enabling the clinician to
view to endocardial tracing as it changes with the heart motion in
real time.
[0039] As the ABD processor is identifying the key landmarks and
fitting borders to the sequence of images, it is periodically
making confidence measurements to gauge the likelihood that the
image borders are being accurately located and traced. For
instance, if the septum is not clearly contrasted from the blood
pool in the LV chamber, the automated process will stop. If the
various correlation coefficients do not exceed predetermined
thresholds the process will stop. Both spatial and temporal
confidence measurements are employed. For instance, if the computed
border of an image varies too much from a standard shape in either
size or shape, the process will abort. This can arise if the
landmarks are located in unusual positions in relation to each
other, for example. If the change in the computed border from one
image in the sequence to another is too great, the process will
likewise abort. When the process stops, a message is displayed
notifying the clinician of the reason for stopping the process, and
gives the clinician the option to continue the automated process,
to continue the automated process with or after clinician input, or
for the clinician to acquire a new loop of images or manually trace
the current images.
[0040] In the illustrated example of FIG. 8 the automatically drawn
borders of the end diastole and end systole images are used to
compute the heart's ejection fraction. This is done by an automatic
modified Simpson's rule process which divides the delineated heart
chamber at each phase into a stack of virtual disks. The diameter
of each disk is used with the disk height to compute an effective
volume of each disk, and these volumes are summed to compute the
heart chamber volume at both end diastole and end systole. The
difference between the two yields the ejection fraction, the volume
or percentage of the heart volume which is expelled as pumped blood
during each heart cycle. The ejection fraction calculation is shown
in the measurement box at the lower left hand corner of FIG. 8 and
is constantly updated. Thus, if the clinician should adjust a drawn
border by the rubberbanding technique, the computed volume of the
heart during that phase will change, affecting the ejection
fraction calculation, and the new calculation immediately appears
in the measurement box. As the clinician adjusts the drawn borders
he instantaneously sees the effects of these changes on the
calculation of the ejection fraction.
[0041] In the previous example the clinician began by acquiring a
cardiac loop on which to automatically trace borders. FIG. 10 shows
an ultrasound image display in which a loop is acquired based upon
the ability of the ABD processor to automatically draw borders on
the images. In the illustrated display the real time ultrasound
image 10 is continuously viewed as in FIG. 1 as the clinician
manipulates the transducer probe to acquire the desired four
chamber view of the heart. As the clinician manipulates the probe
the ABD processor is operative to attempt to draw borders on at
least one of the images of each cardiac cycle. Using the R-wave
timing of the ECG trace 12, the ultrasound system automatically
selects the image or images to be traced from each loop. The
selected image could be the first image of a cardiac cycle, the end
diastole image, or the end systole image, for instance. As the ABD
processor attempts to draw borders on the fly on the selected
images of the real time loops, the results of the ABD process for
an image of each loop is shown as a small "thumbnail" image 92-98
below the real time image 10. In the illustrated example four
thumbnail images are shown for four consecutive loops. Each time a
new thumbnail is processed by the ABD processor it appears at the
right side of the row of thumbnail images, the oldest thumbnail
image disappears, and the row slides to the left. Initially the
clinician may not be acquiring the heart in an orientation which is
acceptable for the ABD process, at which time the progression of
thumbnail images will show no borders as the ABD processor is
unable to successfully draw borders on the images. But as the
clinician manipulates the probe to acquire the necessary viewing
plane for successful ABD performance and the images are acquired
with better clarity and definition, borders will appear on the
progression of thumbnail images as shown in the drawing figure.
When the clinician is holding the probe at the necessary angulation
relative to the heart so that the ABD process is continuously
successful, the progression of thumbnail images will continuously
show successfully drawn borders. The clinician will then freeze the
acquisition to capture one or more of the successfully traced loops
in the Cineloop memory, and will then select one of the loops for
full ABD processing and display as described above. Thus, the ABD
processor is used to assist the clinician in manipulating the probe
for successful image acquisition and in acquiring loops which can
be successfully processed for border definition by the ABD
processor.
[0042] Another way to indicate to the clinician that acceptable
images for ABD processing are being acquired is by means of a
graphical ABD success indicator. Such an indicator may be
qualitative, quantitative, or both, as is the example shown in FIG.
10. At the right of the display of FIG. 10 is a gauge 110 which is
quantified from zero to 100%. When the clinician is acquiring
images which are unsuitable for ABD processing, the gauge 110 is
empty. But as suitable images begin to be acquired, a color bar 112
begins to rise from the bottom of the gauge. The quantization of
the gauge indicates either the percentage of borders which were
attempted and successfully drawn, or the changes in overall
confidence measures as discussed above. In the drawing a green bar
is at the 80% level, indicating that the ABD processor was able to
successfully process 80% of the images attempted over a recent
interval such as the last few heart cycles, or that the borders
drawn achieved an 80% confidence level of accuracy.
[0043] A third way to indicate ABD success to the clinician is to
present drawn borders in real time on the real time images 10. The
ABD processor can attempt to draw a border on a single image for
each heart cycle, such as the end systole image, and the
successfully drawn border is displayed over the real time image for
the duration of that heart cycle until the time of the next end
systole image. Alternatively, if sufficient processing speed is
available, borders are calculated and displayed for every image in
the heart cycle. In either case, the drawn border will not appear
or will flicker on and off when unsuitable or marginal cardiac
images are being acquired, but will constantly appear when a
succession of suitable images is being acquired, at which time the
clinician knows that the probe is oriented to acquire good four
chamber views for ABD processing.
[0044] In addition to the LV of four chamber views, the ABD
processor of the present invention can also define borders in other
types of ultrasound images. Short axis views can be processed for
automatic border definition, in which case the landmarks used can
be the annulus or the outflow track. Alternatively, the center of
the heart chamber can be found from its contrast with the
surrounding heart wall, then the desired border located by radial
extension and fitting of a circular standard shape. The walls of
blood vessels such as the carotid artery can similarly be traced by
identifying the center line of the vessel, then extending straight
line shapes out from opposite sides of the center line to fit small
line segments to the endothelial wall. Fetal anatomy such as the
fetal cranium can also be automatically traced by use of an
elliptical shape.
[0045] With the ability to automatically draw borders of structures
of the heart such as the endocardium on a complete loop of images,
a number of diagnostic techniques become practical. For instance,
FIG. 11 illustrates a technique for assessing regional wall motion
using automated border detection. The drawing of FIG. 11 represents
an ultrasound display in which the continuous motion of the
endocardium or myocardium is shown over several complete heart
cycles. The ABD processor is operated as described above to draw a
trace along the endocardial border or continuously through the
myocardium of the images of one or more loops. The latter is
performed by tracing the endocardial border as described above,
then drawing a curve parallel to and slightly larger than the
endocardial border curve. Such a curve will reliably pass
continuously through the heart muscle. The border 100 for one such
image is shown at the left side of the drawing, with the landmark
points and control points numbered from one to eight in sequence
around the border. For analysis of wall motion the image points
beneath the border are Doppler processed to determine the velocity,
Doppler power or variance along the defined border. Thus, a tissue
Doppler image line is computed along the endocardium or myocardium
at locations defined by the automatically drawn border. This
Doppler processing is performed for the defined border of each
image in the loop or loops. The Doppler processed information from
the moving tissue may be fundamental frequency signals or harmonic
frequency signals which can be processed as described in U.S. Pat.
No. 6,036,643. The lines of Doppler values for all of the images
are displayed in straight vertical lines as shown at the right side
of FIG. 11 as indicated by the vertical sequence of numbers 1-8.
The lines are arrayed sequentially adjacent to each other in the
time sequence of the images. The Doppler values are preferably
displayed in color, thus forming a color M-mode display area 102.
The display in area 102 may be referred to as an ABD-TDI (ABD with
tissue Doppler imaging) display. In the illustrated display the
color Doppler lines for the first loop are arrayed across the area
indicated by bracket L1, the color Doppler lines for the next loop
are arrayed across the area indicated by bracket L2, and the color
Doppler lines for the third loop are arrayed across the area
indicated by bracket L3, and so on. As the arrow at the bottom of
the display area 102 indicates, the Doppler lines progress in time
in the horizontal direction. This display 102 thus shows in a
continuum over the heart cycle the motion of the LV myocardium.
This display enables the clinician to follow the motion of one
point or region of the heart wall over a full cardiac cycle by
observing a horizontal row of the display. For instance, the heart
wall at the apex of the heart is marked by 5 at the left of the
area 102, corresponding to the apex landmark 5 on the border 100.
By viewing the Doppler data (colors) to the right of 5 in area 102
the clinician is able to see the velocity or change in velocity or
intensity of motion of the heart wall at the apex of the heart as
it varies over the complete heart cycle or cycles. If a region of
the wall is not moving due to infarction or some other defect, it
can be spotted by a change or difference in color at a particular
horizontal elevation in the ABD-TDI display.
[0046] It will be appreciated that, since the LV heart wall is
constantly expanding and contracting as the heart beats, the length
of the line 100 from the MMA, around the apex, and back to the LMA
is constantly changing in correspondence. If the control points are
simply delineated in even spacings around the line 100, they may
not continuously correspond to the same points of the heart wall
through the full heart cycle. This is overcome by tracking the
anatomy from a baseline of control points over the heart cycle, as
by speckle tracking each local point of the heart wall along the
ABD trace from frame to frame, as described above. The different
length lines are rescaled or normalized to a common length so that
a horizontal line extended to the right from each number at the
left of the display 102 will relate to the same point or region of
the heart wall over the continuum of tissue Doppler lines.
[0047] An ABD-TDI display may also be formed from short axis images
of the heart. In short axis views the heart wall exhibits a ring
shape. As described previously, the endocardium can be traced
automatically for each frame of the cardiac cycle and a parallel,
slightly larger circle than the tracing can be drawn through the
myocardial muscle in the images. Doppler values are acquired around
each of these circles, which are displayed in a continuum of lines
in the format shown in area 102 of FIG. 11. Thus, the display
format 102 may be used for either short or long axis views of the
heart.
[0048] Another application for automatically drawn cardiac borders
is shown in FIG. 12. In this illustration the border 300 represents
the endocardial border defined by automated border detection as
described above, with a line 306 for the mitral valve plane at the
bottom. A second, slightly larger border 302 is drawn around the
first border 300. This second border may be an ABD-produced border
of the epicardium, or it may be a trace spaced by a predetermined
lateral distance d normal to the endocardial border 300. In this
latter case, the trace 302 can pass continuously through the
myocardium. Thus, Doppler values along the trace 302 would yield
motional measures taken in a central portion of the heart muscle.
The space between the two traces can be divided into small areas
304 and the Doppler values within each area integrated to produce a
measure of regional wall motion at a particular location on the LV
wall. These measures are made using ABD processing of many or all
of the images of the cardiac loop to quickly and accurately provide
quantified measures of cardiac performance over most or all of the
cardiac cycle.
[0049] The measurements made from the areas 304 can be used to
automatically fill out an anatomically corresponding scorecard for
cardiac performance. For example, FIG. 13a shows a graphical
representation 310 of the LV in a 4-chamber view, with the
myocardium divided into numbered areas. The region numbered 6 on
the anatomical scorecard 310 corresponds to the small areas
304a-304d which were defined by automatically drawn borders. The
measurements taken in these areas 304a-304d can be aggregated and
used to automatically place a score on the scorecard 310 for region
6, which may be numerical or qualitative, for example, a coded
color. The score can be a peak or average value measured for one
phase of the heart cycle or taken over all the frames of the full
heart cycle. FIG. 13b illustrates a similar anatomical scorecard
312 for a short axis view of the heart, which may be used to score
images with automatically drawn borders acquired from that view. A
scorecard may be filled in for just a single image frame, for a
group of image frames taken together, or a scorecard may be
completed for each frame of a cardiac sequence. In the latter case,
color coded scorecards can be played in rapid succession in a real
time (or slower or faster) loop of images of the scorecards,
enabling the clinician to view the time variation of a region of
the heart in a segment of the scorecard which is stationary on the
display screen from frame to frame.
[0050] Automatically drawn cardiac borders may also be used to
define the myocardial area in contrast-enhanced images or loops.
The addition of a contrast agent to the cardiac imaging exam allows
the physician to assess how well the heart muscle is being perfused
with blood. Automatically computed borders may be used as input
into a variety of perfusion quantification algorithms.
Automatically drawn cardiac borders and perfusion information
presented simultaneously in an image or loop is a powerful
combination since the clinician can assess wall motion, thickening,
and perfusion simultaneously. Given that the borders are known, the
thickness of the myocardial walls between the endocardial and
epicardial edges can be determined on a segment-by-segment basis as
shown in FIG. 12. Perfusion information quantified by an
independent algorithm may also be displayed side-by-side with the
quantitative wall thickening information. Quantitative perfusion
information and wall thickening may also be parametrically combined
and presented on a segment-by-segment basis in a color coded
display for Doppler and wall motion integration.
[0051] Another diagnostic technique made practical by automatic
border detection is strain rate analysis of cardiac performance.
The strain rate is a measurement computed as the axial derivative
of the velocity of the tissue, and can lead to a representation of
the relative deformation of the tissue during contraction or
expansion. The conventional way to compute strain rate in an
ultrasound image is to find Doppler velocity values along the
ultrasound beams, then to compute the spatial gradient as a
derivative using successive velocity values along the beam. This
spatial gradient of velocity is thus strongly dependent upon the
variable relationship between the beam directions and the anatomy
in the image, which means that the strain rate values can change as
the probe is moved. The present inventors prefer to use a strain
rate calculation which is dependent upon the direction of tissue
motion rather than an arbitrary beam direction. Accordingly the
present inventors calculate strain rate in the direction of the
velocity vector of tissue motion. In order to do this it is
necessary to have not only velocity values for the tissue pixels in
an image but also the direction or vectorial component of the
motion, which can be obtained by known vector Doppler techniques.
The differential between adjacent pixels in the direction of motion
is then computed as the strain rate. The strain rate can be
computed from fundamental frequency echo information, or from
harmonic frequency signals which can be more clutter-free than the
fundamental frequency signals.
[0052] FIG. 14a shows two traces which have been automatically
drawn over the borders of a 4-chamber view of the LV. The border
250 is drawn to define the endocardium and the border 252 has been
drawn to define the epicardium of the LV. A third trace 260 is
automatically drawn between the endocardial and epicardial borders.
This third trace 260 will reliably pass continuously through the
myocardium. These traces enable the strain rate to be computed for
the two major components of motion of the LV. One of these
components is the contraction and expansion of adjoining cells in
the heart muscle. This motion is generally along the direction of
the trace 260. A strain rate representation of this cellular motion
can be found by differentiating the velocity values of successive
points A-A' along trace 260 as shown in the drawing. The overall
motion of the heart chamber as the muscle cells contract and expand
is 248 toward and away from the center of the heart chamber. A
strain rate representation of this second motional component is
computed by differentiating velocities in a direction normal to the
drawn borders such as at points B-B' across the heart muscle. The
strain rate so calculated along the myocardium is preferably
displayed in a color-coded representation. A similar set of strain
rate measurements can be made using borders 270 (endocardium) 272
(epicardium) and trace 280 (myocardium) drawn on short axis views
of the heart such as that shown in FIG. 14b. In that drawing muscle
cell contraction and expansion is used to compute strain rate in
the circumferential direction such as would be computed from the
velocities at points A-A' in the image. Radial components of
expansion and contraction are represented in a strain rate display
by differentiating in the radial direction such as by using the
velocities at points B-B', C-C', and D-D'. The strain rate over the
full cardiac cycle can be displayed by computing the strain rate
around the entire border for each frame in the cardiac cycle, then
displaying the strain for each frame as a vertical line in a time
sequence of lines as shown by display 102 in FIG. 11.
[0053] FIGS. 15a and 15b illustrate the use of automated border
detection in three dimensional imaging. The previous examples have
shown how borders can be automatically drawn on two dimensional
cardiac images. The technique described above is effective for
defining the borders of three dimensional cardiac images also. If a
three dimensional cardiac image is produced by acquiring a series
of spatially adjacent 2D image planes of the heart, the ABD process
described above can be performed on each component frame to define
a series of boundaries which together define a surface of the heart
such as the endocardial surface. If the three dimensional cardiac
image is produced from ultrasonic beams steered in three dimensions
to scan the heart three dimensionally in real time as described in
U.S. patent application Ser. No. 09/645,872 entitled "ULTRASONIC
DIAGNOSTIC IMAGING OF THE CORONARY ARTERIES," the resulting three
dimensional data set can be divided into a series of parallel
planes which are processed as described above to define a series of
planar borders which can be assembled to provide a boundary such as
the heart wall. Preferably the three dimensional data set is
processed three dimensionally, in which case advantage is taken of
the contiguous nature of the heart wall in three dimensions in the
data set to more reliably define the three dimensional border In
either case, the resultant three dimensional border of the LV
endocardium may appear as shown in FIG. 15a, a somewhat elongated
pouch-like surface which is closed at the apex end A and open at
the mitral valve plane A'. FIG. 15a represents the three
dimensional endocardial surface traced at one phase of the heart
cycle. In each 3D image of a 3D cardiac loop the endocardial
surface will be slightly different as the LV continuously contracts
and expands during the heart cycle. Thus a different border surface
200 can be computed for each three dimensional image in the loop.
Since the speed of sound may not enable the ultrasonic data for a
full 3D image to be acquired at the desired 3D frame rate, the 3D
images may be built up over time by using a heart gate triggered
from the ECG waveform to acquire the data for a portion of a 3D
image at specific phases of the heart over numerous cardiac cycles
until the full data set necessary to produce 3D images of the
desired temporal spacing over the entire heart cycle is
acquired.
[0054] The 3D image of the endocardium in FIG. 15a can be produced
by Doppler processing, thereby revealing the velocity, variance, or
Doppler power at each point on the LV wall by rotating and
examining the endocardial tissue Doppler surface 200. Another way
to view the Doppler information for the entire endocardium is to
"unwrap" the tissue Doppler surface 200 to a two dimensional form
as shown in FIG. 15b. In this illustration the apex is located at A
and the mitral valve plane extends along the bottom edge between A'
and A'. In this display the clinician can examine the motion of the
entire endocardium in one view. Such a display shows motion at only
one phase of the heart cycle, the phase indicated by cursor 14
below the ECG waveform 12 of the display, and thus it is desirable
to unwrap all of the endocardial surfaces from all of the 3D images
of the heart cycle and arrange them in a "stack" so that the
clinician can view them sequentially in any order. If the clinician
spots a motional abnormality on one of the unwrapped images, such
as in the area denoted by box 202, she can focus in on this cardiac
wall location where the abnormality is seen. She can then scan
through the stack of images in the box 202 in either temporal order
to examine the abnormality in greater detail over the full heart
cycle. Alternately, the clinician can draw a line through the
abnormality in box 202, then display the tissue Doppler values
along that line from all the images in the sequence in an ABD-TDI
display 102 as described above.
[0055] If real time 3D imaging capability is not available, a 3D
diagnosis can still be performed by acquiring multiple image planes
of a chamber of the heart at different orientations, which are then
processed by automatic border detection. An ultrasound system which
acquires ultrasound information from only selected planes of an
organ of the body is described in U.S. patent [application Ser. No.
9/641,306], entitled "METHOD OF CREATING MULTIPLANAR ULTRASONIC
IMAGES OF A THREE DIMENSIONAL OBJECT." FIG. 15c is an illustration
of the endocardial border 200 viewed from the apex A in the center
of the drawing, which is how the heart may be viewed by a
transducer probe placed for an apical view as described above. With
the probe so located, ultrasound information is acquired from three
planes which pass through the heart chamber, labeled 204, 206 and
208 in the drawing. In this drawing the planes are viewed edge-on,
and in this example the three planes intersect in the vicinity of
the apex of the LV. The ultrasound information from the three
planes may be acquired at a particular phase of the heart cycle
chosen by and ECG heart gate, or over the full cardiac cycle which
may also be assisted by ECG gated acquisition over a number of
cardiac cycles. The LV endocardial borders in the images of the
three planes are automatically drawn as described above and
analyzed.
[0056] A quick method for identifying a region of the heart where
more detailed study is required is to score cardiac performance on
a symbolic representation of the heart. One such symbolic
representation is the bullet scorecard 210 shown in FIG. 15d. The
scorecard 210 represents the heart muscle of a chamber of the heart
as if the myocardium were spread out in a single plane with the
apex at the center of the scorecard and the juncture of the
myocardium and the mitral valve plane located around the perimeter
of the scorecard. Each sector of the scorecard 210 extending from
the center to the perimeter represents a different section of the
heart muscle extending from the apex to the mitral valve plane. The
areas in the scorecard are numbered to refer to specific areas of
the heart wall. For instance the image plane 204 of FIG. 15c would
intersect areas 1, 7, the center of the scorecard, and areas 10 and
4. The image plane 206 of FIG. 15c would intersect areas 6, 12, 16,
14, 9 and 3 of the scorecard, and the image plane 208 of FIG. 15c
would intersect areas 5, 11, 15, 13, 8 and 2 of the scorecard. The
Doppler-detected motion on an automatically drawn border in one or
more image frames in the image planes is used to enter data in the
scorecard 210. The scorecard is filled in automatically using the
motion information from the automatically drawn borders to indicate
areas of the heart where detailed diagnosis is warranted. For
instance, if cardiac behavior in the plane 204 of the LV is normal,
areas 1, 7, 10, and 4 can be displayed in green on the ultrasound
system display. If an unusual characteristic such as abnormal
motion is sensed in the vicinity of the juncture of the myocardium
and the mitral valve plane, area 1 may be displayed in yellow (for
mild irregularity) or red (for a serious irregularity), to caution
the clinician to look more closely at this area. Numerical scores
may be used in addition to or alternatively to color-coding. A
preferred four-tiered scoring system for cardiac performance is to
score regions of the heart muscle as being either normal,
hypokinetic, dyskinetic, or akinetic. Thus the displayed bullet
scorecard with its color-coded or numerically scored areas will
point the clinician to regions of the heart where more detailed
diagnosis should be performed.
[0057] It is preferable, of course, to use a complete 3D data set
to fill in the scorecard 210. For instance, the defined heart wall
200 of FIG. 15a can be "flattened," and spread in a circle about
the apex so that each area of the myocardium in the data set
corresponds to an area of the scorecard. The motional data over a
section of the flattened heart wall 200 can be averaged to fill in
a corresponding section of the bullet scorecard 210. For example,
the motional data over section 212 of the endocardial data 200 can
be averaged to automatically compute a score (either quantitative
or qualitative) for corresponding area 5 of the scorecard 210. The
scores for section 212 from a plurality of endocardial data sets
taken over the full heart cycle can also be averaged or outlying
values detected to produce a scorecard of averages of cardiac
performance or greatest degrees of abnormal performance.
[0058] FIG. 16 illustrates an ultrasound system constructed in
accordance with the present invention. A probe or scanhead 410
which includes a 1D or 2D array transducer 412 transmits ultrasonic
waves and received ultrasonic echo signals. This transmission and
reception is performed under control of a beamformer 420 which
processes in received echo signals to form coherent beams of echo
signals from the anatomy being scanned. The echo information is
Doppler processed by a Doppler processor 430 when ABD-TDI
information or strain rate information is to be presented, and the
processed Doppler information is coupled to an image processor 440
which forms 2D or 3D grayscale or Doppler images. The images pass
through a Cineloop memory 460 from which they may be coupled
directly to a video processor 470 for display on an image display
480. The images may also be applied to an ABD processor which
operates on the 2D or 3D images as described above to define the
anatomical borders and boundaries in the images. The defined
borders are overlaid on the images which are coupled to the video
processor 470 for display. The system may operate to define and
display borders on loops of images saved in the Cineloop memory
460, or to display borders drawn on real time images produced
during live scanning of a patient.
* * * * *