U.S. patent application number 13/427723 was filed with the patent office on 2012-07-19 for reference image display method for ultrasonography and ultrasonic diagnosis apparatus.
Invention is credited to Osamu ARAI, Takao IWASAKI, Tsuyoshi MITAKE, Kiyoshi OKUMA, Koichi OSHIO, Hiroshi SHINMOTO.
Application Number | 20120184851 13/427723 |
Document ID | / |
Family ID | 33436421 |
Filed Date | 2012-07-19 |
United States Patent
Application |
20120184851 |
Kind Code |
A1 |
ARAI; Osamu ; et
al. |
July 19, 2012 |
REFERENCE IMAGE DISPLAY METHOD FOR ULTRASONOGRAPHY AND ULTRASONIC
DIAGNOSIS APPARATUS
Abstract
An ultrasonic image is captured by an ultrasonic probe. A
reference image is obtained by extracting a tomographic image
corresponding to the scan plane of the ultrasonic image from volume
image data that is pre-obtained by a diagnostic imaging apparatus
and that is stored in a volume-data storing unit. The ultrasonic
image and the reference image are displayed on the same screen. In
this case, of the reference image, a portion corresponding to the
view area of the ultrasonic image is extracted and the resulting
reference image having the same region as the ultrasonic image is
displayed as a fan-shaped image.
Inventors: |
ARAI; Osamu; (Ibaraki,
JP) ; IWASAKI; Takao; (Miyagi, JP) ; MITAKE;
Tsuyoshi; (Chiba, JP) ; OSHIO; Koichi; (Tokyo,
JP) ; OKUMA; Kiyoshi; (Tokyo, JP) ; SHINMOTO;
Hiroshi; (Tokyo, JP) |
Family ID: |
33436421 |
Appl. No.: |
13/427723 |
Filed: |
March 22, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10556032 |
Nov 8, 2005 |
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PCT/JP04/06238 |
May 10, 2004 |
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13427723 |
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Current U.S.
Class: |
600/443 |
Current CPC
Class: |
G06T 2207/30101
20130101; G06T 2207/10132 20130101; A61B 8/483 20130101; G06T
2219/028 20130101; G06T 7/33 20170101; A61B 8/466 20130101; G06T
2207/10081 20130101; G06T 2207/10088 20130101; G06T 19/00 20130101;
A61B 8/13 20130101; G06T 7/38 20170101; A61B 8/463 20130101; Y10S
128/916 20130101 |
Class at
Publication: |
600/443 |
International
Class: |
A61B 8/14 20060101
A61B008/14 |
Foreign Application Data
Date |
Code |
Application Number |
May 8, 2003 |
JP |
2003-130490 |
May 8, 2003 |
JP |
2003-130600 |
Claims
1. An ultrasonic diagnosis apparatus comprising: an ultrasonic
image generating unit for generating an ultrasonic image based on
reflection echo signals output from an ultrasonic probe; a storing
unit for storing volume image data pre-obtained by a diagnostic
imaging apparatus; a reference-image generating unit for extracting
tomographic image data corresponding to a scan plane of the
ultrasonic image from the volume image data stored in the storing
unit, and reconstructing a reference image; a displaying unit for
displaying the reference image and the ultrasonic image; and a 3D
body-mark determining unit for generating a three-dimension
visualized image of an object using the volume image data stored in
the storing unit, superimposing an image representing the scan
plane in a translucent color on the three-dimension visualized
image, and displaying the superimposed image on the displaying
unit.
2. The ultrasonic diagnosis apparatus according to claim 1, wherein
the displaying unit displays a target on the ultrasonic image and
the reference image when the target pre-set in the volume image
data enters the scan plane of the ultrasonic probe.
3. The ultrasonic diagnosis apparatus according to claim 1, wherein
the displaying unit displays a target on the ultrasonic image and
the reference image when the target pre-set in the reference image
of the volume image data enters the scan plane of the ultrasonic
probe.
4. The ultrasonic diagnosis apparatus according to claim 2, wherein
the 3D body-mark determining unit determines a positional
relationship between the scan plane and the target set in the
volume image data, and the displaying unit displays a direction and
a distance of the target relative to the scan plane.
5. The ultrasonic diagnosis apparatus according to claim 1, wherein
the displaying unit displays a portion of the reference image
corresponding to a view area of the ultrasonic image with the same
magnification as the ultrasonic image.
6. The ultrasonic diagnosis apparatus according to claim 1, wherein
the displaying unit displays a portion of the reference image out
of a view area of the ultrasonic image with reduced brightness.
7. The ultrasonic diagnosis apparatus according to claim 1, wherein
the displaying unit displays an acoustic shadow of the ultrasonic
image on the reference image in a simulated manner.
8. The ultrasonic diagnosis apparatus according to claim 1, wherein
the displaying unit displays the ultrasonic image aligned with the
reference image.
9. The ultrasonic diagnosis apparatus according to claim 1, wherein
the displaying unit displays a composite image of the ultrasonic
image and the reference image.
10. The ultrasonic diagnosis apparatus according to claim 9,
wherein the composite image is an image superimposing a
translucent-color image of the reference image on the ultrasonic
image.
11. The ultrasonic diagnosis apparatus according to claim 1,
wherein the composite image is a difference image between the
reference image and the ultrasonic image.
12. The ultrasonic diagnosis apparatus according to claim 1,
wherein the reference image generating unit changes an image size
of the reference image in accordance with a speed of movement of
the ultrasonic probe.
13. The ultrasonic diagnosis apparatus according to claim 1,
wherein the displaying unit displays a region of interest set on at
least one of the ultrasonic image, the reference image, and a
composite image of the ultrasonic image and the reference image on
the other images.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application is a Continuation of U.S.
application Ser. No. 10/556,032, filed Nov. 8, 2005, which is a
National Stage Entry of PCT/JP04/006238, filed May 10, 2004, which
claims priority from Japanese Patent Application Nos. JP
2003-130490 and JP 2003-130600, both filed on May 8, 2003, the
contents of which are hereby incorporated by reference into this
application.
TECHNICAL FIELD
[0002] The present invention relates to reference-image display
methods for ultrasonography and ultrasonic diagnosis apparatuses
using the methods. More specifically, the present invention relates
to a technology preferably used for reconstructing, using
multi-slice-image data of a patient obtained by a diagnostic
imaging apparatus, a reference image of the same cross section as
an ultrasonic scan plane in real time and for displaying the
reference image and an ultrasonic image on the same screen.
Examples of the diagnostic imaging apparatus include an ultrasonic
diagnosis apparatus, a magnetic resonance imaging (MRI) apparatus,
and an X-ray computed tomography (X-ray CT) apparatus.
BACKGROUND ART
[0003] Ultrasonic diagnosis apparatuses, which are one type of
diagnostic imaging apparatuses, are frequently used for diagnosis,
since they are easy to handle and are capable of performing
noninvasive observation of arbitrary cross sections in real time.
On the other hand, ultrasonic images captured by the ultrasonic
diagnosis apparatuses are generally inferior in image quality to
tomographic images captured by X-ray CT apparatuses or the like.
Thus, comprehensive diagnosis may be performed while performing
comparison with a tomographic image captured by another diagnostic
imaging apparatus, such as an X-ray CT apparatus or an MRI
apparatus (the tomographic image will hereinafter be referred to as
a "reference image"). For example, when hepatophyma or the like is
treated by radiofrequency ablation under the guidance of an
ultrasonic image, it is conceived that a treatment portion is
pre-located by CT diagnosis and a CT image thereof is used as a
reference image to perform the guidance with the ultrasonic
image.
[0004] However, when a CT image or MR image is merely rendered as
the reference image to recognize an association relationship
between the images is a great burden on the operator. This is
because the reference image provided by a CT image or MR image is
typically a tomographic image of a cross section perpendicular to a
body axis, whereas the ultrasonic image is a tomographic image of
an arbitrary cross section specified by the operator.
[0005] Non-patent Document 1 describes an approach to facilitate
the recognition of an association relationship between a reference
image and an ultrasonic image. In the approach, a position sensor
is attached to an ultrasonic probe to determine an ultrasonic scan
plane and a reference image of the same cross section as the
ultrasonic scan plane is reconstructed from multi-slice image data
(hereinafter referred to as "volume image data") of a CT image or
MR image and is rendered on a display screen. Similarly, Patent
Document 1 also proposes a technology in which a reference image of
the same cross section as an ultrasonic scan plane is reconstructed
from the volume image data of a CT image or MR image and the
reference image and an ultrasonic image are rendered on a display
screen in an aligned or superimposed manner or in an alternately
switched manner.
[0006] Patent Document 2 proposes a technology to aid manipulation
for introducing a puncture needle into a body. That is, an
ultrasonic scan plane is controlled so as to include the puncture
needle and a reference image corresponding to the ultrasonic scan
plane is cut out and is displayed. In the technology, two markers
are attached to a body surface at a position corresponding to a
patient's diseased area, into which the puncture needle is to be
inserted, to obtain the volume image data of a reference image.
Further, an ultrasonic probe is provided with an introducing
portion for the puncture needle, so that the position and the angle
of the puncture needle relative to the probe is fixed, and a sensor
for detecting the position and the angle of the probe is attached
to the probe to determine the ultrasonic scan plane. In this
manner, a coordinate system for the volume image data and a
coordinate system for the ultrasonic scan plane are associated with
each other and a reference image corresponding to the ultrasonic
scan plane is cut out and is displayed. [0007] Non-patent Document
1: "Radiology" RNSA issued in 1996, page 517, K. Oshio [0008]
Patent Document 1: Japanese Unexamined Patent Application
Publication No. 10-151131 [0009] Patent Document 2: Japanese
Unexamined Patent Application Publication No. 2002-112998
DISCLOSURE OF INVENTION
[0010] However, in the prior art, although a reference image of a
cross section corresponding to the scan plane of an ultrasonic
image is cut out and is displayed on the same screen, no
consideration is given to a scheme for matching display regions and
the magnifications of a reference image and an ultrasonic image
and. For example, an ultrasonic image is a fan-shaped image
obtained by capturing one part of a living body of a patient,
whereas a CT image or MR image is typically a circular image
obtained by capturing the entire body of the patient. Thus, when
the reference image and the ultrasonic image are merely displayed
in an aligned manner, there is also a problem in that it is
difficult to recognize an association relationship of portions he
or she desires to observe.
[0011] In addition, in order to obtain an ultrasonic image of a
region including a target (e.g., a diseased area) arbitrary
specified on a reference image by the operator, he or she must
manipulate the ultrasonic probe to search the region including the
target. However, in the prior art, there is a problem in that no
consideration is given to a scheme for facilitating the recognition
of the positional relationship between the current ultrasonic scan
plane and the target.
[0012] Accordingly, a first object of the present invention is to
facilitate the recognition of an association relationship between
an ultrasonic image and a reference image which are displayed on
the same screen, the reference image being obtained by another
diagnosis apparatus.
[0013] A second object of the present invention is to facilitate
the recognition of the positional relationship between a target
specified on an arbitrary reference image by an operator and the
current ultrasonic scan plane.
[0014] In order to achieve the first object, an ultrasonic
diagnosis apparatus of the present invention includes ultrasonic
image generating means for reconstructing an ultrasonic image from
reflection echo signals output from an ultrasonic probe, storing
means for storing volume image data pre-obtained by a diagnostic
imaging apparatus; reference-image generating means for extracting
tomographic image data corresponding to a scan plane of the
ultrasonic wave from the volume image data stored in the storing
means and reconstructing a reference image, controlling means for
causing the reference image and the ultrasonic image to be
displayed on a screen, and displaying means for displaying the
reference image and the ultrasonic image. In accordance with the
tomographic image data and a positional relationship between the
ultrasonic probe and a patient, the reference-image generating
means extracts tomographic image data of a portion corresponding to
a view area of the ultrasonic image to generate the reference
image.
[0015] Thus, according to the present invention, since the
reference image of the same region corresponding to the fan-shaped
view-area of the ultrasonic image is displayed as a fan-shaped
image, it is possible to easily recognize an association
relationship between both the images. In this case, it is
preferable that, of the reference image, the region corresponding
to the view area be displayed with the same magnification as the
ultrasonic image, since the recognition of an association
relationship between both the images is further facilitated. It is
also preferable that, of the reference image, brightness of a
portion out of the view area of the ultrasonic image be reduced to
perform display. With this arrangement, it is possible to perform
comparison and observation without losing information of the
reference image.
[0016] Further, displaying an acoustic shadow of the ultrasonic
image on the reference image in a simulated manner further
facilitates the recognition of an association relationship between
both the images. Also, the ultrasonic image and the reference image
can be displayed on the screen in an aligned manner, but the
configuration is not limited thereto. A composite image of the
ultrasonic image and the reference image can be displayed on the
screen. The composite image can be an image obtained by
superimposing a transparent image of the reference image on the
ultrasonic image. Also, the composite image can be a difference
image between the reference image and the ultrasonic image.
[0017] It is preferable that the reference-image generating means
change an image size of the reference image in accordance with a
speed of movement of the ultrasonic probe. This makes it possible
to display the reference image according to a quick movement of the
ultrasonic image, thus enhancing the freedom of manipulating the
probe during the comparison and observation.
[0018] In order to achieve the second object, the ultrasonic
diagnosis apparatus of the present invention includes a 3D
body-mark determining unit for determining a positional
relationship between the scan plane and a target set in the volume
image data to cause a direction and a distance of the target
relative to the scan plane to be displayed on the screen.
[0019] Additionally, the ultrasonic diagnosis apparatus of the
present invention may further includes a cine-memory for storing
the ultrasonic image reconstructed by the ultrasonic-image
generating means, a position sensor for detecting a position and an
inclination of the ultrasonic probe, scan-plane-coordinate
determining means for determining scan-plane coordinates of the
ultrasonic image in accordance with an output from the position
sensor, and scan-plane-coordinate-system storing means for storing
the determined scan-plane coordinates. The reference-image
generating means reads the scan-plane coordinates of the ultrasonic
image from the scan-plane-coordinate-system storing means, reads
the tomographic-image data corresponding to the read scan-plane
coordinates, and reconstructs the reference image. The image
processing means reads the ultrasonic image from the cine-memory
and causes the reference image corresponding to the read ultrasonic
image, the reference image being output from the reference-image
generating means, to be displayed. With this arrangement, since
ultrasonic images are sequentially read from the cine-memory and
displayed and reference images corresponding to the ultrasonic
images are sequentially cut out and displayed, comparison and
observation can be performed using moving images.
[0020] It is also preferable that the ultrasonic diagnosis further
includes at least one of a posture sensor for detecting a change in
the posture of the patient and a sensor for detecting breathing and
further has correcting means for correcting the scan-plane
coordinates in accordance with an amount of internal-organ movement
caused by a posture change or the breathing of the patient during
ultrasonic diagnosis. With this arrangement, a displacement between
the reference-image coordinate system and the ultrasonic-image
coordinate system, the displacement being resulting from
internal-organ movement caused by the breathing or a posture change
of the patient, can be corrected. Thus, the accuracy of comparison
and observation of both the images can be improved.
[0021] In addition or instead, the configuration can be such that,
after the scan plane of the ultrasonic probe is scanned and one of
an ultrasonic image and a reference image which has a distinctive
point is searched for and frozen, the ultrasonic probe is
manipulated, an image that is other than the frozen ultrasonic
image or reference image and that matches the frozen one of the
images is displayed and frozen, and a coordinate difference between
scan-plane coordinates for the frozen one of the images and the
other image is determined, so that the scan plane coordinates can
be corrected based on the determined coordinate difference.
[0022] Further, in addition to the above-described configuration,
the ultrasonic diagnosis apparatus can include: a position sensor
for detecting a position and an inclination of the ultrasonic probe
in association with a reference coordinate system;
scan-plane-coordinate determining means, for determining scan-plane
coordinates of an ultrasonic image captured by the ultrasonic probe
in association with the reference coordinate system, in accordance
with an output from the position sensor; reference-point inputting
means for setting a reference point on a reference image displayed
on the screen based on the volume image data obtained in
association with the reference coordinate system;
volume-data-coordinate determining means for determining
coordinates, of tomographic data of the volume image data
associated with the scan-plane coordinates, by determining a
coordinate relationship between the position of the ultrasonic
probe and a region that corresponds to the reference point and that
exists on an ultrasonic image obtained by bringing the ultrasonic
probe in contact with a body surface of the patient; and
volume-data-coordinate storing means for storing the
tomographic-image-data coordinates determined by the
volume-data-coordinate determining means. The reference-image
reconstructing means can read the coordinates of the tomographic
image data, associated with the scan-plane coordinates determined
by the scan-plane-coordinate determining means, from the
volume-data-coordinate storing means and can extract the reference
image. With this arrangement, the reference point for aligning the
coordinate systems can be set inside the body of the patient. Thus,
compared to the prior art in which a reference point is set on the
body surface, the freedom of setting the reference point is
increased and thus the accuracy of comparison and observation can
be further improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a block diagram of a basic diagnostic imaging
system to which an ultrasonic diagnosis apparatus of one embodiment
of the present invention is applied.
[0024] FIG. 2 is a block diagram of a specific diagnostic imaging
system to which an ultrasonic diagnosis apparatus of another
embodiment of the present invention is applied.
[0025] FIG. 3 is a flow chart showing a sequence of a drawing
procedure for an ultrasonic image and a reference image in one
embodiment of the present invention.
[0026] FIG. 4 is a view showing a display example of an ultrasonic
image, a reference image, a composite image, and a 3D body mark
according to a feature of the present invention.
[0027] FIG. 5 is a view showing a display example of an ultrasonic
image, a reference image, a composite image, and a 3D body mark
which are preferable for navigation according to a feature of the
present invention.
[0028] FIG. 6 is a block diagram of a specific diagnostic imaging
system to which an ultrasonic diagnosis apparatus of still another
embodiment of the present invention is applied.
[0029] FIG. 7 are block diagrams of a position-sensor equipped
probe in one embodiment according to the present invention.
[0030] FIG. 8 show the configuration and the processing procedure
of breathing-amount determining means according to the present
invention.
[0031] FIG. 9 is a detailed block diagram of a
scan-plane-coordinate determining unit and a scan-plane-coordinate
storing unit in the embodiment shown in FIG. 2.
[0032] FIG. 10 is a flow chart of initialization processing for
coordinate associating processing in the embodiment shown in FIG.
6.
[0033] FIG. 11 is a flow chart of embodiment of a reference-image
display processing, during ultrasonic diagnosis, in the embodiment
shown in FIG. 6.
[0034] FIG. 12 are diagrams illustrating an association
relationship between volume image data and a scan-plane coordinate
system.
[0035] FIG. 13 is a flow chart of one embodiment for correcting a
reference-coordinate-system displacement caused by breathing or the
like of a patient.
[0036] FIG. 14 shows one example of a coordinate adjustment screen
for assisting processing for correcting scan plane coordinates.
[0037] FIG. 15 is a view illustrating a method for correcting a
coordinate-system displacement resulting from internal-organ
movement caused by the breathing of the patient.
BEST MODE FOR CARRYING OUT THE INVENTION
[0038] Preferred embodiments of the present invention will be
described below with reference to the accompanying drawings.
First Embodiment
[0039] FIG. 1 is block diagram of a basic diagnostic imaging system
to which an ultrasonic diagnosis apparatus of one embodiment of the
present invention is applied. As shown, the diagnostic imaging
system includes an ultrasonic diagnosis apparatus 101 according to
one embodiment of the present invention and a medical diagnostic
imaging apparatus 102 for obtaining volume image data that provides
as a reference image. The volume image data refers to the data of
multi-slice images obtained by capturing the inside of the body of
a patient along multiple slice planes. The data of the volume
images captured by the medical diagnostic imaging apparatus 102 is
input to the ultrasonic diagnosis apparatus 101. A computed
tomography apparatus (X-ray CT apparatus) or a magnetic resonance
imaging apparatus (MRI apparatus) can be used as the medical
diagnostic imaging apparatus 102. CT images and MR images have
higher image qualities than ultrasonic images, as is known, and
thus are suitable as reference images for ultrasonic images, which
are inferior in image quality. However, when a temporal change in
tissues of a patient is diagnosed with ultrasonic waves, the volume
image data of a pre-obtained ultrasonic image can be drawn as the
reference image.
[0040] In FIG. 1, descriptions of functions commonly included in
the ultrasonic diagnosis apparatus 101 are omitted to avoid
complexity, and only the functions of major units associated with
displaying the reference image according to a feature of the
present invention are described. As shown, the ultrasonic diagnosis
apparatus 101 can broadly be divided into a section for
reconstructing an ultrasonic image and a section for reconstructing
the reference image. The former ultrasonic-image reconstructing
section has a probe 104 and an ultrasonic-image determining unit
105. The latter reference-image reconstructing section has a
volume-data storing unit 107 and a reference-image determining unit
111.
[0041] The ultrasonic-image determining unit 105 provides
ultrasonic-image generating means for reconstructing an ultrasonic
image in accordance with a reflection echo signal output from the
probe 104. The ultrasonic-image determining unit 105 is adapted to
associate signals output from a position sensor 108 with the
reconstructed ultrasonic image. On the other hand, a controlling
unit 120 is adapted to determine the scan-plane coordinates of the
probe 104 in accordance with signals output from the position
sensor 108 and to output the determined scan-plane coordinates to
the reference-image determining unit 111. The reference-image
determining unit 111 provides a reference-image generating means
for extracting tomographic image data, corresponding to the
scan-plane coordinates input from the controlling unit 120, from
the volume-data storing unit 107 and reconstructing the reference
image. Thus, the ultrasonic image reconstructed by the
ultrasonic-image determining unit 105 and the reference image
reconstructed by the reference image determining unit 111 are
adapted to be displayed on a monitor 114.
[0042] In particular, the reference-image determining unit 111 is
configured such that it extracts tomographic-image data-of a region
corresponding to the view area of an ultrasonic image, in
accordance with the scan-plane coordinates that are input from the
controlling unit 120 and that are based on the positional
relationship between the probe 114 and the patient, and generates a
reference image.
[0043] According to the present embodiment configured as described
above and shown in FIG. 1, a reference image corresponding to the
fan-shaped view area of an ultrasonic image, the reference image
and the ultrasonic image captured from the same region, is
displayed as a fan-shaped image. This makes it possible to easily
recognize an association relationship between both the images. In
this case, displaying, of the reference image, a region
corresponding to the view area of the ultrasonic image with the
same magnification as the ultrasonic image can further facilitate
the recognition of an association relationship between both the
images. Also, displaying, of the reference image, a region that is
out of the view area of the ultrasonic image, with reduced
brightness, allows comparison and observation without loosing the
information of the reference image.
Second Embodiment
[0044] FIG. 2 shows the configuration of a specific diagnostic
imaging system to which an ultrasonic diagnosis apparatus of the
present invention is applied. In the figure, means having the same
functional configurations as those in FIG. 1 are denoted with the
same reference numerals and the descriptions thereof are omitted.
In FIG. 2, a scan-plane-coordinate determining unit 109 and a
scan-plane-coordinate storing unit 110 correspond to the
configuration of the major unit of the controlling unit 120. A
cine-memory 106 stores an ultrasonic image reconstructed by the
ultrasonic-image determining unit 105. A 3D body-mark determining
unit 112 is provided in connection with the reference-image
determining unit 111. An adder 113 is configured as image
processing means for appropriately combining images generated by
the cine-memory 106, the reference-image determining unit 111, and
the 3D body-mark determining unit 112. The monitor 114 is adapted
to display images generated by the cine-memory 106, the
reference-image determining unit 111, and the 3D body-mark
determining unit 112 and the image processed by the adder 113.
[0045] The probe 104 transmits/receives ultrasonic waves to/from a
patient 103 and has built-in multiple transducers that generate
ultrasonic waves and that receive reflection echoes. The
ultrasonic-image determining unit 105 receives reflection echo
signals output from the probe 104 and converts the received signals
into digital signals to create an ultrasonic image 302, such as a
tomographic image (B-mode image) or a color flow mapping image (CFM
image), of a diagnosis region, as shown in FIG. 3 and so on. The
cine memory 106 receives ultrasonic images created by the
ultrasonic-image determining unit 105 and stores ultrasonic images
for multiple frames.
[0046] The volume-data storing unit 107 receives the volume image
data of a reference image, captured by the medical diagnostic
imaging apparatus 102, through a network or via a portable storage
(MO) medium, such as a magneto-optical disk, and stores the volume
image data in the ultrasonic diagnosis apparatus 101.
[0047] The position sensor 108 is attached to the probe 104 to
detect the three-dimensional position and inclination of the probe.
A source 116 for a coordinate system including the patient 103 is
placed in the vicinity of a bed 115 on which the patient 103 lies.
The principle of detecting the three-dimensional position and
inclination of the probe 104 is that magnetic signals generated in
a three-dimensional space by the source 116 is detected by the
position sensor 108 and the three-dimensional position and
inclination in a reference coordinate system formed by the source
116 are detected. A position sensor system constituted by the
position sensor 108 and the source 116, is not only limited to a
magnet-based system but also may employ, for example, a known
position sensor system, such as a system utilizing light.
[0048] In accordance with signals output from the position sensor
108 and the source 116, the scan-plane-coordinate determining unit
109 obtains the position and inclination information of the probe
104 in the reference coordinate system to determine scan-plane
coordinates including the position and the inclination of a
ultrasonic scan plane relative to the patient 103. The
scan-plane-coordinate determining unit 109 is also adapted to
calculate scan-plane coordinates in a reference-image coordinate
system, in accordance with the determined scan-plane coordinates.
That is, the scan-plane-coordinate determining unit 109 is adapted
to determine scan-plane coordinate data including, for example, x,
y, and z coordinate data of one corner of a scan plane and rotation
angles about x, y, and y axes of the scan plane in a
volume-image-data coordinate system. The scan-plane-coordinate data
determined by the scan-plane-coordinate determining unit 109 is
input to the scan-plane-coordinate storing unit 110 and scan plane
coordinates for multiple frames are stored therein. In this case,
it is preferable that the number of frames for scan plane
coordinates stored be substantially the same as the number of
frames of ultrasonic images captured in real time and stored in the
cine-memory 106. The reference-image determining unit 111 provides
reference-image reconstructing means, and receives scan-plane
coordinate data and reconstructs a reference image of the same
cross section as an ultrasonic scan image.
[0049] Next, a detailed configuration of the ultrasonic diagnosis
apparatus 101 according to the present embodiment will be described
in conjunction with the operation thereof. FIG. 3 is a flow chart
for rendering an ultrasonic image and a reference image of the same
cross section. The drawing processing is broadly classified into an
ultrasonic-image processing sequence 201 for rendering an
ultrasonic image and storing the scan-plane coordinates in a
storage unit and a reference-image processing sequence 202. These
two sequences 201 and 202 are executed in such a manner that starts
and freezes are synchronized.
[0050] First, when an operator starts the two sequences 201 and
202, a determination is made as to whether a freeze instruction is
input (51). When freeze is not performed, the ultrasonic-image
processing sequence 201 drives the probe 104 to transmit/receive
ultrasonic waves to/from the patient 103 (S2). The ultrasonic-image
determining unit 105 reconstructs an ultrasonic image in accordance
with the reflection echo signals output from the probe 104 (S3).
The reconstructed ultrasonic image is stored in the cine-memory 106
(S4) and is drawn on the monitor 114 (55).
[0051] At this point, the position sensor 108 obtains the position
and inclination of the probe 104 in synchronization with the
transmission/reception of the ultrasonic waves (S12). In accordance
with the position and inclination information input from the
position sensor 108, the scan-plane-coordinate determining unit 109
determines scan-plane coordinates (S13). The determined scan-plane
coordinates are sequentially written to the scan-plane-coordinate
storing unit 110 (S14). In this case', the processing of steps 51
to 55 in the ultrasonic-image processing sequence 201 and the
processing of steps S12 to S14 are executed in synchronization with
each other.
[0052] On the other hand, in the reference-image processing
sequence 202, a determination about freezing is made (S21). When
freezing is not performed, scan-plane coordinates are read from the
scan-plane-coordinate storing unit 110 (S22). Based on volume image
data, the reference-image determining unit 111 reconstructs a
reference image of the same cross section as the ultrasonic image
(S25). The reconstructed reference image is drawn on the monitor
114 (S26). The processing of steps 523 and 524 will be described
below.
[0053] Next, when the operator inputs an instruction for freezing
the processing, the ultrasonic-image processing sequence 201 and
the reference-image processing sequence 202 are adapted to execute
cine playbacks in S31 and 532, respectively, based on the
determination in steps Si and S21. The cine playback of an
ultrasonic image is executed by referring to the ultrasonic image
data stored in the cine memory 106. In contrast, the cine playback
of a reference image is executed by using the scan-plane coordinate
data stored in the scan-plane-coordinate storing unit 110 and by
reconstructing a reference image corresponding to the scan plane
based on the volume image data. The ultrasonic image data stored in
the cine-memory 106 and the scan-plane coordinate data stored in
the scan-plane-coordinate storing unit 110 are stored in
synchronization with each other, it is possible to render an
ultrasonic image and a reference image whose time phases are the
same. The cine playback of an ultrasonic image is performed by
referring to the ultrasonic-image data stored in the cine-memory
106, whereas the cine-playback of a reference image is performed by
referring to the scan-plane-coordinate data stored in the
scan-plane-coordinate storing unit 110. Thus, it is sufficient for
the memory of the scan-plane-coordinate storing unit 110 to store
only scan-plane-coordinate data, the memory capacity can be
reduced. Similarly, for storing a moving image, merely storing
scan-plane coordinates corresponding to volume image data makes it
possible to play back the moving picture while reconstructing it
from the volume image data. Thus, a moving-image file having a
small file size can be created.
[0054] Now, an image-display processing method according to a
feature of the present invention will be described with reference
to FIG. 4. First, in accordance with the enlargement factor
(magnification) of the ultrasonic image 302, the reference-image
determining unit 111 enlarges or reduces a reference image and
displays it at the same magnification, as shown in a reference
image 301 Shown in FIG. 4. The reference-image determining unit 111
also extracts an out-of-view area 312 corresponding to a fan-shaped
viewing angle 311 of the ultrasonic image 302 and reduces the
brightness of a reference image corresponding to the region 312. As
a .about.result, the reference image is displayed in the same
display format and with the same magnification as those of the
ultrasonic image 302, thus making it easy to recognize an
association relationship between the ultrasonic image 302 and the
reference image. This arrangement also makes it possible to perform
display without losing the information of a reference image in the
out-of-view area of the ultrasonic image. Also, an acoustic shadow
307, such as a bone 313 (or air), appears on the ultrasonic image
302. It is preferable that a region corresponding to the acoustic
shadow 307 be extracted based on determination, for example, using
CT values of a CT image; and the brightness of an area 308 that is
deeper than that region be reduced. Similarly, an area 310 is
extracted, using CT values, from a region where a blood vessel
exists and the region is displayed, for example, in red, like an
ultrasonic CFM (color flow mapping) image 309. This makes it
possible to display the reference image 301, which allows easy
comparison with the ultrasonic image 302.
[0055] On the other hand, the 3D body-mark determining unit 112
extracts a three-dimension visualized image, such as a 3D body mark
304 in FIG. 4, by using volume image data, superimposes a scan
plane 314 in a translucent color on the three-dimension visualized
image, and displays the resulting image. As the three-dimensional
visualized image, for example, a known method, such as volume
rendering or surface rendering, can be used. Displaying the 3D body
mark 304 allows the positional relationship between the patient 103
and the scan plane 314 to be recognized in three dimensions. The 3D
body-mark determining unit 112 may be provided with a function for
extracting a region of interest, specified by the operator, from
the volume image data and determining the distance and the
direction from the scan plane to the region of interest.
[0056] The adder 113, which provides the image processing means, is
intended to determine a composite image 303 of the reference image
301 and the ultrasonic image 302. The adder 113, for example,
converts the reference image 301 into a translucent-color image and
superimposes it on the ultrasonic image 302. Instead, a difference
image between the reference image 301 and the ultrasonic image 302
may be obtained and drawn. This can facilitate that the reference
image 301 and the ultrasonic image 302 are compared with each other
using one image. With the difference image, for example, when an
ultrasonic volume image data obtained in advance is used as the
reference image, it is useful to diagnose a temporal change in
living-body tissues of the patient.
[0057] Thus, as shown in FIG. 4, the ultrasonic image 302, the
reference image 301, the composite image 303, and the 3D body-mark
304 of the same cross section are drawn on the monitor 114. This
allows the operator to perform effective diagnosis while comparing
those images.
[0058] For example, using the medical diagnostic imaging apparatus
102 to obtain volume image data centering at a treatment region
before medical treatment, causing the ultrasonic diagnosis
apparatus 101 to capture an image of the treatment region after the
medical treatment, and displaying a reference image before the
medical treatment and an ultrasonic image after the medical
treatment, for example, in an aligned manner can facilitate
determination of the effect of the medical treatment. Also,
synthesizing an image of a difference between the reference image
before the medical treatment and the ultrasonic image after the
medical treatment and displaying the difference image further
facilitates the determination of the effect of the medical
treatment. In particular, performing display in added color
according to the degree of the difference can further facilitate
viewing.
[0059] By reducing the image size and changing the frame rate, the
reference-image determining unit 111 can increase the speed of
reconstructing a reference image in accordance with the motion of
the probe 104. That is, the reference-image determining unit 111
determines the movement speed and the rotation speed of the scan
plane, based on the scan-plane coordinate data. When the speed is
greater than a certain threshold, the reference-image determining
unit 111 reduces the image size to reconstruct the reference image
at a high speed. That is, when the movement of the probe 104 is
fast, priority is given to the frame rate over the image quality to
draw the reference image at a high speed. and when the movement of
the probe 104 is slow, priority is given to the image quality over
the frame rate to reconstruct and draw the reference image. This
makes it possible to draw the reference image so as to correspond
to the ultrasonic image that varies according to the motion of the
probe 104.
[0060] An image-display processing method with a navigation
function will further be described with reference to FIG. 5. This
ultrasonic diagnosis apparatus is adapted to allow navigation for
guiding the scan plane of the probe 104 to a target 405 that the
operator pre-set on a reference image in the volume image data. The
target 405 can be set by designating. a region with a mouse, for
example, on an axial image, sagittal image, coronal image, and
three-dimensional visualized image. The 3D body-mark determining
unit 112 calculates the distance and direction from the current
scan plane to the center of the target 405 and displays a
three-dimensional arrow image and numeric values in a display
region 407 on the screen of a 3D body mark 404. The boundary of the
region of the target 405 is also rendered in a reference image 401
and an ultrasonic image 402. This allows the operator to visually
recognize the distance from the current ultrasonic scan plane 314
to the target 405. When the target 405 enters the scan plane 314, a
boundary determined from the reference image 401 is also displayed
in the ultrasonic image 402. Consequently, it is easy to recognize
an association relationship between the reference image 401 and the
ultrasonic image 402.
[0061] Additionally, a region of interest (ROI) 406 that the
operator set on any of the ultrasonic image 402, the reference
image 401, and a composite image 403 is displayed on all the
images. This facilitates the recognition of an association
relationship of the region of interest.
Third Embodiment
[0062] FIG. 6 shows the configuration of a diagnostic imaging
system to which an ultrasonic diagnosis apparatus of another
embodiment of the present invention is applied. In FIG. 6, what are
different from the embodiment shown in FIG. 2 are that a breathing
sensor 117 for detecting the amount of breathing of the patient 103
and a posture sensor 118 for detecting the body movement are
provided and outputs of the detections are input to the
scan-plane-coordinate determining unit 109. Although processing for
associating a volume-image-data coordinate system with a scan-plane
coordinate system was omitted in the embodiment in FIG. 2, details
thereof will be described.
[0063] In the present embodiment, as shown in FIG. 7A, the position
sensor 108 is attached to one surface of the probe 104 to make it
possible to detect the position and inclination of the probe 104,
i.e., the position and inclination of the ultrasonic scan plane, in
a coordinate system formed by the source 116. In FIG. 7A,
transducers are arranged on a circular arc surface of the probe 104
and the distance between a center point 201 of the transducers and
a center point 202 of the position sensor 108 has been accurately
determined. The relationship between the probe 104 and the position
sensor 108 is not limited to what is shown in the figure and can be
configured as shown in FIG. 7B. That is, the arrangement can be
such that a bar-shaped pointer 203 is detachably attached in
association with the position sensor 108 and an end point 204 of
the pointer 203 is used as a reference point relative to the center
point 202. With this arrangement, the probe 104 of the present
embodiment can also be utilized as a pointing device.
[0064] In the same manner as the position sensor 108, the posture
sensor 118 is attached to the body surface of the patient 103 so as
to measure the position and inclination of the patient 103 in the
reference coordinate system formed by the source 116. The breathing
sensor 117 measures the amount of breathing of the patient 103. For
example, as shown in FIG. 8A, the breathing sensor 117 having a
function similar to the position sensor 108 is attached to the body
surface of the patient 103, lying on the bed 115, so as to detect
the amount of body-surface movement caused by the breathing. As
shown in FIG. 8B, the measured amount of movement can be converted
into an amount of breathing.
[0065] While the scan-plane-coordinate determining unit 109 and the
scan-plane-coordinate storing unit 110 are configured to be
essentially the same as those in the second embodiment, features
and functions according to the present embodiment will be
specifically described. The scan-plane coordinate determining unit
109 has a function for correcting scan-plane coordinates in
accordance with the posture information of the patient 103 and the
amount of breathing of the patient 103. The scan-plane coordinates
as used herein refer to the coordinates of an ultrasonic scan plane
imaged by the probe 104. As shown in FIG. 9, the
scan-plane-coordinate determining unit 109 and the
scan-plane-coordinate storing unit 110 include a scan-plane
coordinate-system storing unit 211 a volume-image-data
coordinate-system storing unit 212, a posture-change-amount
determining unit 213, an internal-organ-movement-amount determining
unit 214, a correcting unit 215, and a
corrected-scan-plane-coordinate determining unit 216. As in the
embodiment shown in FIG. 2, the reference-image determining unit
111 receives the scan-plane coordinates, extracts
same-cross-section image data corresponding to the scan-plane
coordinates from the volume-data storing unit 107, and
reconstructs. a reference image. The adder 113 then draws a
reference image, output from the reference-image determining unit
111, and an ultrasonic image, read from the cine-memory 106, on the
monitor 114. The ultrasonic image and the reference image are
typically displayed on the same screen in an aligned manner, but
instead, can be displayed in a superimposed manner. When they are
displayed in a superimposed manner, it is desired that the
reference image be translucent.
[0066] Now, processing for associating volume-image-data
coordinates with scan-plane coordinates will be described with
reference to FIGS. 10, 11, and 12. The coordinate association
processing in the present embodiment can be broadly classified into
an initialization stage shown in FIG. 10 and a diagnosis stage
shown in FIG. 11.
[0067] First, a description is given of the initialization stage
shown in FIG. 10, i.e., processing during the imaging of volume
image data. In step S101, as shown in FIG. 12B, the x axis of the
source 116 for the position sensor is oriented in the lateral
direction of the bed 115, the y axis is oriented in the
longitudinal direction of the bed 115, and the z axis is oriented
in the vertical direction of the bed 115 to thereby place the
source. Thus, the x, y. and z axes of a source coordinate system
that has the origin at, for example, a center 224 of the source 116
are aligned parallel to the x, y, and z axes of a coordinate system
having an original 225 at one corner of volume image data shown in
FIG. 12A. That is, volume data 221 shown in FIG. 12A is obtained by
typically laying the patient 103 on the bed 115 and capturing a
tomographic image perpendicular to the body axis (the y-axis
direction) of the patient 103. Placing the source 116 so as to be
aligned with the bed 115 allows the x, y, and z axes of the
reference coordinate system of the source 116 and the coordinate
system of the volume data 221 to be substantially parallel to each
other.
[0068] Next, in step S102, a reference point 223 is set in the
volume data 221. The reference point 223 is set on an operation
screen by using a pointing device, such as a mouse. The operation
screen is displayed with a reference image obtained by' imaging
volume image data. The operation screen may include an axial image,
sagittal image, coronal image, or three-dimensional visualized
image. Designating the reference point 223 on any of the images
makes it possible to set the reference point 223 on the body
surface or inside the body in the volume image data.
[0069] In contrast, in step S103, a reference point 222 in the
scan-plane coordinate system is set, for example, by locating the
probe 104 with the position sensor 108 at a position corresponding
to the reference point 223 of the volume data 221 and holding the
probe 104. For example, when the reference point 222 of the volume
data is designated on the body surface, the contact point 201 of
the probe 104 is placed at a body-surface position of the actual
patient 103, the body-surface position corresponding to the
reference point 222, to set the reference point 222 in the
scan-plane coordinate system. In this case, since the position of
the reference point 222 and the position of the reference point 223
match each other, it is possible to match the coordinate system of
the volume image data and the coordinate system of the scan plane.
In this case, the probe 104 is used as a pointing device. Here, in
order to facilitate the work of placing the probe at the
body-surface position of the actual patient, the body-surface
position being corresponding to the position of the reference point
specified in the volume image data, it is preferable that a
distinctive point (e.g., a xiphoid process or a blood vessel
branch) that can be easily found on the body surface from the
external view be selected as the reference point 223 specified in
the volume image data.
[0070] On the other hand, when the reference point in the volume
image data is specified inside the body, the probe is manipulated,
an ultrasonic image containing a region containing the in-vivo
reference image 223 is displayed, and a region corresponding to the
in-vivo reference point 223 is specified on the ultrasonic image by
using a pointing device, such as a mouse. Then, the distance
between the specified point and the center 202 or the contact point
201 of the probe 104 is determined and the coordinates of the two
reference points 222 and 223 are associated with each other. In
this case, in order to easily identify the in-vivo reference point
223 on the ultrasonic image, it is preferable that an easy-to-find
distinctive point on the ultrasonic image be selected as the
reference point specified in the volume image data, as described
above.
[0071] Next, in step S104, relationship data for associating the
scan-plane coordinate system with the reference coordinate system
of the source 116 is determined. First, the origin of the patient
103 in the real space is set at the reference point 222. The
coordinate axes of the scan plane coordinate system are set
parallel to the coordinate axes of the source coordinate system.
Then, the position (X, Y, and Z) of the reference point 222 of the
probe 104, the position being detected by the position sensor 108,
is determined, the scan-plane coordinate system and the source
coordinate system are associated with each other, and the resulting
association data is stored in the scan-plane coordinate-system
storing unit 211 shown in FIG. 9. In this manner, the
volume-image-data coordinate system and the scan-plane coordinate
system can be associated with each other via the reference
coordinate system of the source 116. In step S105, data for
associating the volume-image-data coordinate system with the
scan-plane coordinate system is created and is stored in the
volume-image-data coordinate-system storing unit 212 shown in FIG.
9.
[0072] Since the source 116 is placed in step S101 such that the
coordinate axes of the volume-image-data coordinate system are
parallel to the coordinate axes of the source coordinate system.
Setting only one reference point 223 in the volume-image-data
coordinate system can facilitate that those two coordinate systems
are associated. That is, placing the source 116 in an appropriate
direction according to the direction of the body axis of the
patient can readily align the coordinate systems. However, in the
present invention, three reference points 223 can also be set. In
this case, the accuracy of associating the coordinate systems can
be improved. For example, when the coordinate systems are
determined with three reference points, one of the three points is
designated as the origin of the coordinate system, vectors from the
origin to the remaining two points are designated as an X axis and
a Y axis, and an axis perpendicular to the x and y axes is
designated as a Z axis to thereby achieve the alignment. This makes
it possible to associate the coordinate systems without caring
about the direction of the placed source 116. The remaining two
points can be automatically set on the screen by causing a
measurement tool for performing measurement on image data to
perform the above-described processing.
[0073] The association data between the volume-image-data
coordinate system and the scan-plate coordinate system, the
association data being created as described above, is used during
ultrasonic diagnosis to determine scan-plane coordinates according
to a procedure shown in FIG. 11. The scan-plane-coordinate
determining unit 109 determines the scan plane coordinates, in
accordance with the position and inclination of the probe 104 which
are detected by the position sensor 108 attached to the probe 104
(step S106). Next, the reference-image determining unit 111 cuts a
reference image, corresponding to the scan-plane coordinates, out
from the volume image data and causes the reference image to be
displayed on the monitor 114 via the adder 113 (step S107). This
allows the operator to draw a reference image that matches an
ultrasonic image corresponding to an arbitrary set position and
direction of the probe, thereby improving the accuracy of
diagnosis.
[0074] Next, a feature and a function of the present embodiment for
correcting the scan plane coordinates in accordance with a change
in the posture and so on will be described. That is, as diagnosis
proceeds, a displacement may occur between the coordinate systems
of the volume image data and the scan plane, due to factors, such
as a change in the posture of the patient and internal-organ
movement caused by the breathing of the patient. Such a
displacement may make it impossible to draw a reference image that
matches the ultrasonic scan plane. Accordingly, in the present
embodiment, in a diagnosis stage, the scan plane-coordinate
determining unit 109 is adapted to correct a displacement in the
scan-plane coordinate system.
[0075] Correction for a change in the posture of the patient will
be described first. The posture of the patient can be detected with
the posture sensor 118 shown in FIG. 6. Thus, a difference between
the posture during initialization and the posture during diagnosis
is determined by the posture-change-amount determining unit 213,
and in accordance with difference, the scan-plane coordinate system
is shifted and rotated to perform correction.
[0076] Next, means for correcting a coordinate-system displacement
due to internal-organ movement caused by the breathing of the
patient will be described with reference to FIG. 13. The operator
performs this correction processing, while viewing a rendered
reference image and ultrasonic image. The operator first pays
attention to the reference image. The operator displays, for
example, a distinctive cross section, including the patient blood
vessel such as a portal vein or superior mesenteric artery, and
performs freezing, while manipulating the probe 104 (step S201).
Next, the operator pays attention to the ultrasonic image, and
renders the same cross section as the frozen image of the reference
image and performs adjustment, while performing visual comparison
with the frozen image (step S202). Here, a difference (the amount
of change) between the scan-plane coordinates during the freezing
and the scan plane-coordinates during the adjustment corresponds to
the amount of internal-organ movement. Thus, the scan-plane
coordinate determining unit 109 determines a difference (the amount
of change) between the scan-plane coordinates during the freezing
and the scan-plane coordinates during the adjustment (step S203).
The scan-plane coordinate system is shifted and rotated by an
amount corresponding to the difference to thereby perform
correction (step S204). Consequently, even when the depth of
breathing of the patient differs from that in the initialization
stage, the scan-plane coordinates and the volume-image-date
coordinate system can be correctly associated with each other.
[0077] During the correction processing in FIG. 13, a coordinate
adjustment screen 231 shown in FIG. 14 is displayed so as to allow
a freeze key 232 and an adjust key 234 to be operated on the
screen. Also, the amount of movement and the amount of rotation
which are related to the correction can also be displayed in
parameter edit boxes 232. The operator can perform correction by
directly inputting numeric values to the edit boxes 232.
[0078] In addition, an input amount of breathing is measured by the
breathing sensor 117, the correction is repeated at multiple depths
of breathing, and the correlation between the amount of breathing
and the amount of internal-organ movement is determined. With this
approach, a displacement caused by internal-organ movement can be
automatically corrected in accordance with an input from the
breathing sensor.
[0079] Hereinabove, a volume-image-data reference image having a
distinctive point is frozen and an ultrasonic scan plate
corresponding to the reference image has been determined.
Conversely, the arrangement may also be such that an ultrasonic
scan plane having a distinctive point is frozen and image
processing is performed to automatically determine a reference
image corresponding to the ultrasonic scan plane. Specifically, an
ultrasonic scan plane displaying a distinctive point of the patient
is frozen and the ultrasonic scan plane is recorded in a storage
medium, such as the cine-memory 106. By using a known pattern
matching method, the reference-image determining unit 111 extracts
a reference image corresponding to the distinctive point of the
frozen ultrasonic scan plane from the volume image data stored in
the volume-data storing unit 107. The reference image extracted as
a result of matching is displayed on the monitor 114. In the
reference-image matching processing, there is no need to search all
the volume image data. Thus, only data regarding the scan-plane
side, viewed in the scan direction of the ultrasonic probe 104, may
be extracted to match distinctive regions. Magnification may also
be adjusted such that a distinctive point on the ultrasonic scan
plane and a distinctive point on the reference image have the same
magnification. In this manner, extracting a reference image from
image information having a distinctive point can enhance the
accuracy of aligning the ultrasonic scan plane and the reference
image.
[0080] In addition, another example of the means for correcting a
coordinate-system displacement due to internal-organ movement
caused by the breathing of the patient will be described with
reference to FIG. 15. As in the case of FIG. 13, the operator
performs this correction processing while viewing a rendered
reference image and an ultrasonic image. First, the probe 104 is
placed on the patient so that cross sections perpendicular to a
direction in which the internal organs move due to breathing are
displayed. The direction in which the internal organs move due to
breathing is typically the body axis direction of the patient. The
probe 104 placed on the patient is then moved in the internal-organ
movement direction, and distinctive ultrasonic tomographic images,
including a blood vessel such a portal vein or superior mesenteric
artery, are rendered. At this point, due to the occurrence of a
displacement between the volume-image-data coordinate system and
the scan-plate coordinate system, a cross-section displacement in
the body axis direction occurs between the ultrasonic image and the
reference image. In this state, the ultrasonic image and the
reference image are frozen, cine playback is performed, and the
operator specifies a corresponding combination of a reference image
and an ultrasonic image. For example, in the example shown in FIG.
15, since blood vessels can be most clearly rendered on a reference
image 1 displayed at time t1 and an ultrasonic image 2 displayed at
time t2, it is determined that they are corresponding images. It
can be understood from this that, although the reference image 1
corresponding to the ultrasonic image 2 is supposed to be displayed
at the position of time t2, the corresponding reference image is
displayed at time t1. At this point, a difference (the amount of
change) between scan-plane coordinates 1 and scan-plane coordinates
2 which are stored in the scan-plane coordinate storing unit 110
corresponds to the amount of internal-organ movement. Accordingly,
determining the difference between the scan-plane coordinates 1 and
the scan-plane coordinates 2 and correcting the scan plane
coordinates makes it possible to correct a coordinate-system
displacement caused by the internal-organ movement.
* * * * *