U.S. patent application number 14/871252 was filed with the patent office on 2016-01-21 for medical image processing apparatus, x-ray diagnostic apparatus, medical image processing method and x-ray diagnostic method.
This patent application is currently assigned to Kabushiki Kaisha Toshiba. The applicant listed for this patent is Kabushiki Kaisha Toshiba, Toshiba Medical Systems Corporation. Invention is credited to Satoru OHISHI.
Application Number | 20160015348 14/871252 |
Document ID | / |
Family ID | 51658229 |
Filed Date | 2016-01-21 |
United States Patent
Application |
20160015348 |
Kind Code |
A1 |
OHISHI; Satoru |
January 21, 2016 |
MEDICAL IMAGE PROCESSING APPARATUS, X-RAY DIAGNOSTIC APPARATUS,
MEDICAL IMAGE PROCESSING METHOD AND X-RAY DIAGNOSTIC METHOD
Abstract
According to one embodiment, a medical image processing
apparatus includes processing circuitry. The processing circuitry
is configured to obtain time changes of concentrations of a
contrast agent, based on at least X-ray contrast image data;
generate a gray scale or a color scale by assigning a change in
pixel value for at least one period, to a period shorter than a
period from an initial time to an ending time of the time changes
of the concentrations of the contrast agent; and generate blood
vessel image data according to the gray scale or the color scale.
The blood vessel image data have pixel values corresponding to
times at which the concentrations of the contrast agent become a
specific condition.
Inventors: |
OHISHI; Satoru; (Otawara,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kabushiki Kaisha Toshiba
Toshiba Medical Systems Corporation |
Minato-ku
Otawara-shi |
|
JP
JP |
|
|
Assignee: |
Kabushiki Kaisha Toshiba
Minato-ku
JP
Toshiba Medical Systems Corporation
Otawara-shi
JP
|
Family ID: |
51658229 |
Appl. No.: |
14/871252 |
Filed: |
September 30, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/JP2014/058369 |
Mar 25, 2014 |
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14871252 |
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Current U.S.
Class: |
600/431 |
Current CPC
Class: |
A61B 6/4441 20130101;
A61B 6/5217 20130101; A61B 6/40 20130101; A61B 6/52 20130101; A61B
6/461 20130101; A61B 6/481 20130101; A61B 6/42 20130101; A61B
6/4225 20130101; A61B 6/504 20130101 |
International
Class: |
A61B 6/00 20060101
A61B006/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 1, 2013 |
JP |
2013-076471 |
Claims
1. A medical image processing apparatus comprising: processing
circuitry configured to obtain time changes of concentrations of a
contrast agent, based on at least X-ray contrast image data;
generate a gray scale or a color scale by assigning a change in
pixel value for at least one period, to a period shorter than a
period from an initial time to an ending time of the time changes
of the concentrations of the contrast agent; and generate blood
vessel image data according to the gray scale or the color scale,
the blood vessel image data having pixel values corresponding to
times at which the concentrations of the contrast agent become a
specific condition.
2. A medical image processing apparatus of claim 1, wherein the
processing circuitry is configured to generate the gray scale or
the color scale by assigning a change in pixel value, longer than
the change in the pixel value for the one period, to the period
from the initial time to the ending time of the time changes of the
concentrations of the contrast agent.
3. A medical image processing apparatus of claim 1, wherein the
processing circuitry is configured to generate the gray scale or
the color scale by assigning the change in the pixel value for the
one period multiple times, to the period from the initial time to
the ending time of the time changes of the concentrations of the
contrast agent.
4. A medical image processing apparatus of claim 1, wherein the
processing circuitry is configured to generate plural gray scales
or plural color scales by shifting the gray scale or the color
scale in a direction of the change in the pixel value.
5. A medical image processing apparatus of claim 1, wherein the
processing circuitry is configured to generate plural gray scales
or plural color scales by changing at least one of a phase and a
period of the change in the pixel value for the at least one
period, and generate the blood vessel image data as a moving image,
according to the gray scales or the color scales.
6. A medical image processing apparatus of claim 4, wherein the
processing circuitry is configured to generate the blood vessel
image data using the gray scales or the color scales, the blood
vessel image data being generated as a moving image in which
changes of pixel values different from each other are assigned to
the period shorter than the period from the initial time to the
ending time of the time changes of the concentrations of the
contrast agent.
7. A medical image processing apparatus of claim 4, wherein the
processing circuitry is configured to generate the blood vessel
image data using the gray scales or the color scales, the blood
vessel image data being generated as a moving image of which a
frame interval is different from a frame interval of the X-ray
contrast image data.
8. A medical image processing apparatus of claim 1, wherein the
processing circuitry is configured to generate the gray scale or
the color scale by assigning the change in the pixel value for the
at least one period, to a designated period.
9. A medical image processing apparatus of claim 3, wherein the
processing circuitry is configured to generate a gray scale or a
color scale in which the change of the pixel value for the one
period, having a designated initial pixel value, is repeated in a
designated period.
10. A medical image processing apparatus of claim 1, wherein the
processing circuitry is configured to generate blood vessel image
data, having brightness values according to concentrations of the
contrast agent at the specific condition.
11. A medical image processing apparatus of claim 1, wherein the
specific condition is maximum values, a predetermined ratio of the
maximum values, or a threshold value.
12. A medical image processing apparatus of claim 1, wherein the
processing circuitry is configured to generate the blood vessel
image data based on time changes, of the concentrations of the
contrast agent, having a data interval shorter than a sampling
interval of the concentrations of the contrast agent.
13. A medical image processing apparatus of claim 12, wherein the
processing circuitry is configured to obtain the time changes, of
the concentrations of the contrast agent, having the data interval
shorter than the sampling interval of the concentrations of the
contrast agent, by interpolation processing, curve fitting
processing, or gravity center calculation processing.
14. A medical image processing apparatus of claim 1, wherein the
processing circuitry is configured to generate the blood vessel
image data based on time changes, of the concentrations of the
contrast agent, after running average processing in at least one of
a time direction and spatial directions.
15. A medical image processing apparatus of claim 1, wherein the
processing circuitry is configured to generate the blood vessel
image data based on time changes, of the concentrations of the
contrast agent, after low-pass filtering processing in at least one
of a time direction and spatial directions.
16. A medical image processing apparatus of claim 8, wherein the
processing circuitry is configured to generate the gray scale or
the color scale by assigning a pixel value, different from the
change in the pixel value, to a period other than the designated
period.
17. A medical image processing apparatus of claim 8, wherein the
processing circuitry is configured to generate the gray scale or
the color scale by assigning a transmittance, different from a
transmittance in the designated period, to a period other than the
designated period.
18. A medical image processing apparatus of claim 1, wherein the
processing circuitry is configured to generate the gray scale or
the color scale by assigning a continuous change in color phase, a
continuous change in at least one color brightness value or a
continuous change in gray brightness value, as the change in the
pixel value.
19. A medical image processing apparatus comprising: processing
circuitry configured to obtain time changes in pixel value
corresponding to a blood vessel, based on blood vessel image data
acquired by an image diagnostic apparatus; generate a gray scale or
a color scale by assigning a change in pixel value for at least one
period, to a period shorter than a period from an initial time to
an ending time of the time changes in the pixel value corresponding
to the blood vessel; and generate blood vessel image data according
to the gray scale or the color scale, the blood vessel image data
having pixel values corresponding to times at which pixel values
corresponding to the blood vessel become a specific condition.
20. An X-ray diagnostic apparatus comprising: an X-ray tube and an
X-ray detector for acquiring at least X-ray contrast image data
from an object; and processing circuitry configured to obtain time
changes of concentrations of a contrast agent, based on the at
least X-ray contrast image data; generate a gray scale or a color
scale by assigning a change in pixel value for at least one period,
to a period shorter than a period from an initial time to an ending
time of the time changes of the concentrations of the contrast
agent; and generate blood vessel image data according to the gray
scale or the color scale, the blood vessel image data having pixel
values corresponding to times at which the concentrations of the
contrast agent become a specific condition.
21. A medical image processing method comprising: obtaining time
changes of concentrations of a contrast agent, based on at least
X-ray contrast image data; generating a gray scale or a color scale
by assigning a change in pixel value for at least one period, to a
period shorter than a period from an initial time to an ending time
of the time changes of the concentrations of the contrast agent;
and generating blood vessel image data according to the gray scale
or the color scale, the blood vessel image data having pixel values
corresponding to times at which the concentrations of the contrast
agent become a specific condition.
22. An X-ray diagnostic method comprising: acquiring at least X-ray
contrast image data from an object; obtaining time changes of
concentrations of a contrast agent, based on the at least X-ray
contrast image data; generating a gray scale or a color scale by
assigning a change in pixel value for at least one period, to a
period shorter than a period from an initial time to an ending time
of the time changes of the concentrations of the contrast agent;
and generating blood vessel image data according to the gray scale
or the color scale, the blood vessel image data having pixel values
corresponding to times at which the concentrations of the contrast
agent become a specific condition.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] This is a continuation of Application PCT/JP2014/58369,
filed on Mar. 25, 2014.
[0002] This application is based upon and claims the benefit of
priority from Japanese Patent Application No. 2013-076471 filed on
Apr. 1, 2013; the entire contents of which are incorporated herein
by reference.
FIELD
[0003] Embodiments described herein relate generally to a medical
image processing apparatus, an X-ray diagnostic apparatus, a
medical image processing method and an X-ray diagnostic method.
BACKGROUND
[0004] DSA (Digital Subtraction Angiography) is known as one of
imaging methods for blood vessels in an X-ray diagnostic apparatus.
DSA is the technology to generate subtraction image data between
frames of X-ray image data before and after injecting a contrast
agent into an object, for diagnosis. That is, X-ray image data are
acquired before injecting a contrast agent as a mask image data for
generating subtraction image data. On the other hand, X-ray
contrast image data is acquired by injecting the contrast agent.
Then, DSA image data is generated for diagnosis by subtraction
processing between the X-ray contrast image data and the mask image
data.
[0005] Such DSA image data can be generated as image data in which
unnecessary anatomies in observation of a blood vessel are removed.
That is, diagnostic image data in which blood vessels enhanced by a
contrast agent are depicted selectively can be obtained.
Consequently, images useful for diagnosis of a blood vessel can be
displayed.
PRIOR TECHNICAL LITERATURE
[0006] [Patent literature 1] U.S. Pat. No. 8,050,474 B2
[0007] Even in the case of acquiring DSA images which are typical
as blood vessel images acquired by an X-ray diagnostic apparatus,
precise blood vessel structures for a diagnosis may not be
determined when a cerebral arteriovenous malformation, a dural
arteriovenous fistula or the like is diagnosed. Specifically, it is
often difficult to specify and distinguish blood vessels through
which a contrast agent flows into a diseased part.
[0008] Thus, an object of the present invention is to provide a
medical image processing apparatus, an X-ray diagnostic apparatus,
a medical image processing method and an X-ray diagnostic method
which can obtain precise blood vessel structures allowing blood
vessels, through which a contrast agent flows into a diseased part,
to be identified more clearly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] In the accompanying drawings:
[0010] FIG. 1 is a configuration diagram of an X-ray diagnostic
apparatus and a medical image processing apparatus according to an
embodiment of the present invention;
[0011] FIG. 2 shows a graph for explaining a method of identifying
an inflow time or an arrival time of a contrast agent to a blood
vessel based on a concentration profile of the contrast agent;
[0012] FIG. 3 shows the first example of color scale assigned to
time phases corresponding to the maximum values of concentration
profiles of a contrast agent;
[0013] FIG. 4 shows an example of color scheme in the color scale
shown in (C) of FIG. 3;
[0014] FIG. 5 shows the second example of color scale assigned to
time phases corresponding to the maximum values of concentration
profiles of a contrast agent;
[0015] FIG. 6 shows an example of color scheme in the color scale
shown in (C) of FIG. 5;
[0016] FIG. 7 shows an example of color scales generated for
dynamically changing the color scale shown in (C) of FIG. 3;
[0017] FIG. 8 shows an example of color scales generated for
dynamically changing the color scale shown in (C) of FIG. 5;
[0018] FIG. 9 shows an example of parametric image generated in the
parametric image generation part shown in FIG. 1; and
[0019] FIG. 10 is a flow chart which shows an operation of the
X-ray diagnostic apparatus 1 shown in FIG. 1 and processing in the
medical image processing apparatus 12 shown in FIG. 1.
DETAILED DESCRIPTION
[0020] In general, according to one embodiment, a medical image
processing apparatus includes processing circuitry. The processing
circuitry is configured to obtain time changes of concentrations of
a contrast agent, based on at least X-ray contrast image data;
generate a gray scale or a color scale by assigning a change in
pixel value for at least one period, to a period shorter than a
period from an initial time to an ending time of the time changes
of the concentrations of the contrast agent; and generate blood
vessel image data according to the gray scale or the color scale.
The blood vessel image data have pixel values corresponding to
times at which the concentrations of the contrast agent become a
specific condition.
[0021] Further, according to one embodiment, a medical image
processing apparatus includes processing circuitry. The processing
circuitry is configured to obtain time changes in pixel value
corresponding to a blood vessel, based on blood vessel image data
acquired by an image diagnostic apparatus; generate a gray scale or
a color scale by assigning a change in pixel value for at least one
period, to a period shorter than a period from an initial time to
an ending time of the time changes in the pixel value corresponding
to the blood vessel; and generate blood vessel image data according
to the gray scale or the color scale. The blood vessel image data
have pixel values corresponding to times at which pixel values
corresponding to the blood vessel become a specific condition.
[0022] Further, according to one embodiment, an X-ray diagnostic
apparatus includes an X-ray tube, an X-ray detector and processing
circuitry. The X-ray tube and the X-ray detector acquire at least
X-ray contrast image data from an object. The processing circuitry
is configured to obtain time changes of concentrations of a
contrast agent, based on the at least X-ray contrast image data;
generate a gray scale or a color scale by assigning a change in
pixel value for at least one period, to a period shorter than a
period from an initial time to an ending time of the time changes
of the concentrations of the contrast agent; and generate blood
vessel image data according to the gray scale or the color scale.
The blood vessel image data have pixel values corresponding to
times at which the concentrations of the contrast agent become a
specific condition.
[0023] Further, according to one embodiment, a medical image
processing method includes: obtaining time changes of
concentrations of a contrast agent, based on at least X-ray
contrast image data; generating a gray scale or a color scale by
assigning a change in pixel value for at least one period, to a
period shorter than a period from an initial time to an ending time
of the time changes of the concentrations of the contrast agent;
and generating blood vessel image data according to the gray scale
or the color scale. The blood vessel image data have pixel values
corresponding to times at which the concentrations of the contrast
agent become a specific condition.
[0024] Further, according to one embodiment, an X-ray diagnostic
method includes: acquiring at least X-ray contrast image data from
an object; obtaining time changes of concentrations of a contrast
agent, based on the at least X-ray contrast image data; generating
a gray scale or a color scale by assigning a change in pixel value
for at least one period, to a period shorter than a period from an
initial time to an ending time of the time changes of the
concentrations of the contrast agent; and generating blood vessel
image data according to the gray scale or the color scale. The
blood vessel image data have pixel values corresponding to times at
which the concentrations of the contrast agent become a specific
condition.
[0025] A medical image processing apparatus, an X-ray diagnostic
apparatus, a medical image processing method and an X-ray
diagnostic method according to embodiments of the present invention
will be described with reference to the accompanying drawings.
[0026] FIG. 1 is a configuration diagram of an X-ray diagnostic
apparatus and a medical image processing apparatus according to an
embodiment of the present invention.
[0027] An X-ray diagnostic apparatus 1 includes an imaging system
2, a control system 3, a data processing system 4 and a console 5.
The imaging system 2 has an X-ray tube 6, an X-ray detector 7, a
C-shaped arm 8, a base 9 and a bed 10. In addition, the data
processing system 4 has an A/D (analog to digital) converter 11, a
medical image processing apparatus 12, a D/A (digital to analog)
converter 13, and a display 14. Note that, the A/D converter 11 may
be integrated with the X-ray detector 7.
[0028] The X-ray tube 6 and the X-ray detector 7 are settled at
both ends of the C-shaped arm 8 so as to be mutually opposed at
both sides of the interjacent bed 10. The C-shaped arm 8 is
supported by the base 9. The base 9 has a motor 9A and a rotation
mechanism 9B. The motor 9A and the rotation mechanism 9B drive so
as to rotate the X-ray tube 6 and the X-ray detector 7 fast into a
desired position together with the C-shaped arm 8 like a
propeller.
[0029] As the X-ray detector 7, a FPD (flat panel detector) or
I.I.-TV (image intensifier TV) can be used. Furthermore, the output
side of the X-ray detector 7 is connected with the A/D converter 11
of the data processing system 4.
[0030] The control system 3 drives and controls the imaging system
2 by outputting control signals to the respective elements
consisting of the imaging system 2. The control system 3 is
connected with the console 5 as an input circuit. Therefore,
instruction of imaging conditions and the like to the control
system 3 can be input from the console 5.
[0031] Then, the imaging system 2 is configured to expose X-rays
toward an object O set on the bed 10 at mutually different angles
sequentially from the rotatable X-ray tube 6 under control by the
control system 3. In addition, the imaging system 2 is configured
to acquire X-rays transmitting the object O from the plural
directions sequentially as X-ray projection data by the X-ray
detector 7. The X-ray projection data acquired by the X-ray
detector 7 are output to the A/D converter 11 as X-ray image
data.
[0032] Furthermore, a contrast agent injector 15 is provided in the
vicinity of the object O set on the bed 10 in order to inject a
contrast agent into the object O. Thus, X-ray contrast imaging of
an object O can be performed by injecting a contrast agent from the
contrast agent injector 15 into the object O. The contrast agent
injector 15 can be also controlled by the control system 3.
[0033] Next, configurations and functions of the medical image
processing apparatus 12 will be described.
[0034] The input side of the medical image processing apparatus 12
is connected with the output side of the A/D converter 11.
Meanwhile, the display 14 is connected to the output side of the
medical image processing apparatus 12 through the D/A converter 13.
Moreover, the medical image processing apparatus 12 is connected
with the console 5. Then, direction information required for data
processing can be input into the medical image processing apparatus
12 by operation of the console 5.
[0035] Note that, aside from the medical image processing apparatus
12 built in the X-ray diagnostic apparatus 1 as illustrated in FIG.
1, a similar medical image processing apparatus as an independent
system may be connected with the X-ray diagnostic apparatus 1
through a network.
[0036] The medical image processing apparatus 12 includes an image
memory 16, a subtraction part 17, a filtering part 18, an affine
transformation part 19, a gradation conversion part 20, and a
parametric image generation part 21. The parametric image
generation part 21 has a time phase specifying part 22, a color
coding part 23, and a color scale adjustment part 24.
[0037] The medical image processing apparatus 12 having such
functions can be configured by a computer reading a medical image
processing program. That is, processing circuitry may be used to
configure the medical image processing apparatus 12.
[0038] The image memory 16 is a storage circuit for storing X-ray
image data acquired by the imaging system 2. Therefore, when
non-contrast X-ray imaging has been performed, non-contrast X-ray
image data is stored in the image memory 16. Meanwhile, when X-ray
imaging has been performed with injecting a contrast agent into an
object O, X-ray contrast image data is stored in the image memory
16.
[0039] The subtraction part 17 has a function to generate time
series DSA image data, depicting contrast-enhanced blood vessels,
by subtraction processing between non-contrast X-ray image data
read from the image memory 16 and time series X-ray contrast image
data.
[0040] The filtering part 18 has a function to perform desired
filter processing, such as a high-pass filtering, a low-pass
filtering, or a smoothing filtering, of arbitrary data.
[0041] The affine transformation part 19 has a function to perform
affine transformation processing, such as a scaling, a rotation
movement, and a parallel translation, of X-ray image data,
according to direction information input from the console 5.
[0042] The gradation conversion part 20 has a function to perform
gradation conversion of X-ray image data by referring to an LUT
(Look Up Table).
[0043] The parametric image generation part 21 has a function to
acquire time changes in concentration of a contrast agent based on
time series DSA image data or time series X-ray contrast image data
and a function to generate parametric image data, having pixel
values corresponding to times at which the concentrations of the
contrast agent become a specific condition, as blood vessel image
data.
[0044] For that purpose, the time phase specifying part 22 has a
function to specify time phases, at which concentrations of the
contrast agent become a specific condition, based on profiles
indicating time changes in the concentrations of the contrast
agent. Moreover, the color coding part 23 has a function to assign
colors corresponding to time phases specified by the time phase
specifying part 22. The color scale adjustment part 24 has a
function to determine a color scale used for color coding in the
color coding part 23.
[0045] The specific condition for assigning colors can be
determined, according to diagnostic purposes, to concentrations of
a contrast agent corresponding to time points when the contrast
agent has flowed in or arrived at a focused blood vessel,
concentrations of a contrast agent corresponding to time points
when the contrast agent has flowed out from a focused blood vessel
contrarily, or the like. For example, a time defining the specific
condition can be a time when a concentration of a contrast agent
becomes the maximum value, a predetermined ratio of the maximum
value, or a threshold value.
[0046] FIG. 2 shows a graph for explaining a method of identifying
an inflow time or an arrival time of a contrast agent to a blood
vessel based on a concentration profile of the contrast agent.
[0047] In FIG. 2, the horizontal axis shows the time phase
direction while the vertical axis shows intensities of image
signals, of DSA image data or contrast image data, representing
concentrations of a contrast agent. As shown in FIG. 2, a profile
in concentration change of the contrast agent can be obtained as a
curve, showing signal intensities changing in time, by focusing a
pixel corresponding to a blood vessel region of the time series DSA
image data or contrast image data.
[0048] A typical concentration change profile becomes a curve of
which the value increases gradually with the inflow of a contrast
agent and decreases gradually with the outflow of the contrast
agent. Therefore, when a threshold value TH for detecting a rising
up of the curve is set for values of the concentration change
profile, it becomes possible to identify a time phase at a start of
contrast agent inflow into a focused blood vessel as a time phase
Tth when the concentration of the contrast agent has reached the
threshold value TH.
[0049] However, in a case that noises are large, the time phase at
the start of a contrast agent inflow may be identified incorrectly.
For this reason, a predetermined ratio within the range of 5% to
10% of the maximum value in a concentration profile of a contrast
agent may be used for the threshold value so that influences of
noises can be suppressed. Alternatively, a time phase Tmax at which
a concentration of a contrast agent has reached the maximum value
MAX or a time phase T.sub.max/2 at which a concentration of a
contrast agent has reached 50% of the maximum value MAX may be
detected, from a concentration profile, as a time phase when the
contrast agent has arrived at a blood vessel, as shown in FIG. 2.
Hereinafter, an example case that an arrival time phase of a
contrast agent is identified will be mainly described.
[0050] When the specification of a time phase, based on a
concentration profile of a contrast agent, as shown in FIG. 2, is
performed to each required pixel, and colors according to the
specified time phases are assigned, parametric image data in which
each blood vessel has been depicted in colors according to arrival
times of the contrast agent or the like can be generated.
[0051] Note that, a time change in concentration of a contrast
agent at each pixel representative of several pixels may be
obtained by running average processing. That is, a matrix size of
image data whose concentration changes of a contrast agent should
be obtained can be minified with smoothing processing. Moreover,
concentration changes of a contrast agent may be obtained based on
image data whose noises have been removed by low-pass filter
processing. These processing also can be said as running average
processing or low-pass filtering processing of concentration
profiles of a contrast agent in a spatial direction.
[0052] The running average processing or the low-pass filtering
processing can also be performed not only in spatial directions but
also in a time direction. In the case that the running average
processing or the low-pass filtering processing is performed in the
time direction, the processing is performed to concentration
profiles of a contrast agent in the time direction.
[0053] Therefore, parametric image data can be generated based on
time changes in concentration of a contrast agent after noise
suppression processing in at least one of the time direction and
spatial directions. Moreover, parametric image data can be
generated based on time changes in concentration of a contrast
agent after low-pass filtering processing in at least one of the
time direction and spatial directions. Thereby, smooth parametric
image data from which the noises have been dramatically suppressed
can be generated.
[0054] Moreover, parametric image data can also be generated based
on time changes, in concentration of a contrast agent, each having
a data interval shorter than a sampling interval of the
concentrations of the contrast agent corresponding to an imaging
interval of X-ray contrast image data. A time change, in a
concentration of a contrast agent, which has a data interval
shorter than a sampling interval of the concentration of the
contrast agent, can be obtained by arbitrary processing, such as
interpolation processing, curve fitting processing using a specific
function, or gravity center calculation processing. Thereby, it
becomes possible to identify an arrival time of a contrast agent or
the like at each pixel with a higher precision. In particular, it
is more effective in a case that at least one of running average
processing and low-pass filtering processing is performed.
[0055] FIG. 3 shows the first example of color scale assigned to
time phases corresponding to the maximum values of concentration
profiles of a contrast agent.
[0056] (A) of FIG. 3 shows concentration profiles of a contrast
agent at two dimensional positions (xi, yj) (i=1, 2, 3, . . . , m;
j=1, 2, 3, . . . , n) and arrival time phases Tmax (xi, yj) of the
contrast agent specified based on the maximum values MAXs of the
concentration profiles. The contrast agent arrives at a position,
which is close to an injection position of the contrast agent,
relatively early. Therefore, specified time phases are also
relatively early. On the other hand, the contrast agent arrives at
a position, which is away from the injection position of the
contrast agent, relatively late. Therefore, specified time phases
are also relatively late.
[0057] (B) of FIG. 3 shows an example of color scale assigned to
the specified time phases as shown in (A) of FIG. 3. As shown in
(B) of FIG. 3, a color scale can be generated by assigning a change
in color pixel value for one period, consisting of R value, B value
and G value, to a period Tall from the initial time to the ending
time of time changes in concentrations of a contrast agent obtained
as the concentration profiles. That is, a color scale can be
generated by assigning a continuous color phase change for one
period to the period Tall from the initial time to the ending time
of time change in concentration of a contrast agent.
[0058] According to the color scale as shown in (B) of FIG. 3, a
two dimensional time phase map showing arrival time phases of a
contrast agent can be color coded. Then, parametric image data in
which blood vessels have been depicted by different colors
according to arrival time phases of a contrast agent can be
generated.
[0059] However, when a difference in the arrival time phases Tmax
(xi, yj) of a contrast agent between the pixel positions (xi, yj)
is small relatively to a range of the color scale, as shown in (A)
of FIG. 3, a difference in color between the pixel positions (xi,
yj) becomes also small. Therefore, it may become difficult to
distinguish small difference of time by the difference in
color.
[0060] In particular, when X-ray imaging is performed for the
purpose of diagnosing a dural arteriovenous fistula or a cerebral
arteriovenous malformation, it is important to observe blood flows
between arteries and veins. Therefore, it is often necessary to
distinguish blood vessels having small differences in arrival times
of a contrast agent.
[0061] Thus, a color scale can be changed in the color scale
adjustment part 24 so that even blood vessels between which
differences in arrival times of a contrast agent are small can be
distinguished as differences in color. (C) of FIG. 3 shows an
example of generating a color scale by assigning the continuous
color phase change for one period multiple times to the period
Tall, from the initial time to the ending time of time changes in
concentrations of a contrast agent, as changes in pixel values.
That is, a color scale in which a continuous color phase change is
repeated periodically can be generated.
[0062] Such a color scale generated as described above can assign a
change in pixel value, longer than the change in pixel value for
one period, to the period Tall from the initial time to the ending
time of time changes in concentrations of a contrast agent. Note
that, although the example of generating a color scale by assigning
the change in pixel value for one period multiple times has been
shown in (C) of FIG. 3, a color scale in which the whole change in
pixel value is not an integral multiple of the change in pixel
value for one period may also be generated.
[0063] The color scale as shown in (C) of FIG. 3 can be generated
by designating a pixel value corresponding to the initial time
phase of concentration profiles, a period Tscale of a change in
pixel value, and the initial pixel value in the period Tscale, with
an operation of the console 5. Thereby, it is possible to generate
a color scale in which the change in pixel value for one period is
repeated according to the designated initial pixel value and the
designated period Tscale. Then, the colors can be arranged in each
period Tscale similarly to the color scheme as shown in (B) of FIG.
3. Specifically, a color scale in which a color phase showing the
maximum value changes among red, green and blue in one period
Tscale can be generated.
[0064] FIG. 4 shows an example of color scheme in the color scale
shown in (C) of FIG. 3.
[0065] The three orthogonal axes in FIG. 4 represent R values, G
values, and B values, respectively. The R value, G value, and B
value corresponding to each time phase in the period Tscale can be
determined along the sides of the color triangle, whose vertexes
are the maximum value of the R values, the maximum value of the G
values, and the maximum value of the B values, as shown in FIG. 4.
Specifically, the colors can be arranged so that the G value and
the B value become zero and the R value becomes the maximum value
when the relative time is zero or Tscale, the R value and the B
value become zero and the G value becomes the maximum value when
the relative time is Tscale/3, and the R value and the G value
become zero and the B value becomes the maximum value when the
relative time is 2Tscale/3.
[0066] When such a color scheme is performed, parametric image data
can be generated so that the color changes from red to blue through
green, and then returns to red again according to the time phase.
Note that, the colors between red, green, and blue can be assigned
to time phases so that the R value, the G value, and the B value
change linearly, for example. Alternatively, the R values, the G
values, and the B values may also be assigned to time phases so
that the angle of a line segment, which connects the center of the
color triangle with a point on the sides, changes linearly.
[0067] When parametric image data are generated according to a
color scale generated by such a color scheme, blood vessels can be
distinguished as a difference in colors even when differences in
arrival times of a contrast agent are small. That is, arrival times
of a contrast agent can be understood in detail.
[0068] Note that, the most visible color is red. Therefore, as
exemplified in FIG. 4, setting the color of an initial time phase,
which corresponds to the earliest arrival time of a contrast agent,
to red leads to an improvement of visibility. That is, it is
effective to set a color value, corresponding to the initial time
phase of a color scale, to the maximum value of the R value.
Moreover, as another example, it is also useful to adjust the
initial time phase so that a focused time phase becomes red.
[0069] FIG. 5 shows the second example of color scale assigned to
time phases corresponding to the maximum values of concentration
profiles of a contrast agent.
[0070] (A) of FIG. 5 shows concentration profiles of a contrast
agent at two dimensional positions (xi, yj) (i=1, 2, 3, . . . , m;
j=1, 2, 3, . . . , n) and arrival time phases Tmax (xi, yj) of the
contrast agent specified based on the maximum values MAXs of the
concentration profiles, similarly to (A) of FIG. 3.
[0071] Then, the color scale as shown in (B) of FIG. 5, in which a
change in color pixel value is assigned to the period Tall from the
initial time to the ending time of time changes in concentrations
of a contrast agent, can be changed into the color scale shown in
(C) of FIG. 5. The color scale shown in (C) of FIG. 5 is generated
by assigning the continuous color phase change for one period, as a
change in pixel value, to a designated period. The period to which
the change in pixel value is assigned can be determined by
designating a starting time phase T1 and an ending time phase T2.
The starting time phase T1 and the ending time phase T2 can be
designated by selecting corresponding images respectively from time
series X-ray contrast images or time series DSA images.
[0072] Note that, a color scale can also be generated by assigning
a change in pixel value, such as a change in pixel value for
multiple periods as shown in (C) of FIG. 3, longer than one period,
to the designated period as shown in (C) of FIG. 5. That is, a
color scale can be generated by assigning a change in pixel value
for at least one period, to a designated period.
[0073] FIG. 6 shows an example of color scheme in the color scale
shown in (C) of FIG. 5.
[0074] The three orthogonal axes in FIG. 6 represent R values, G
values and B values, respectively. Similarly to FIG. 4, the R
value, G value and B value corresponding to each time phase within
a designated period can be determined along the sides of the color
triangle. Specifically, the colors can be arranged so that the G
value and the B value become zero and the R value becomes the
maximum value at the starting time phase T1, the R value and the B
value become zero and the G value becomes the maximum value at the
middle time phase between the starting time phase T1 and the ending
time phase T2, and the R value and the G value become zero and the
B value becomes the maximum value at the ending time phase T2,
similarly to an example shown in FIG. 4.
[0075] When the colors are arranged as shown in FIG. 6, a color
scale in which a color phase showing the maximum value changes
among red, green and blue between the starting time phase T1 and
the ending time phase T2 can be generated. That is, a color scale
whose color changes from red to blue through green within a
designated period can be generated.
[0076] With regard to time phase other than a designated period, a
pixel value pattern different from a change in pixel value in the
designated period can be assigned. For example, color phases may be
changed between the inside and the outside of the designated
period. As a more specific example, a color scale can be generated
so that the color phase changes from white to red at the time
phases before the starting time phase T1 while the color phase
changes from blue to white at the time phases after the ending time
phase T2.
[0077] Furthermore, a transmittance different from that in a
designated period can also be assigned to time phase other than the
designated period. As a specific example, a color scale can be
generated so that the transmittance changes from the maximum value
to zero at the time phases before the starting time phase T1 while
the transmittance changes from zero to the maximum value at the
time phases after the ending time phase T2. That is, the
transmittance may be changed in a predetermined range, in time
phases outside the designated period. In this case, it is not
necessary to change color values, such as R value and B value,
outside the designated period.
[0078] As described above, at least one of pixel values, including
R value, G value and B value, and the transmittance, in the time
phase ranges outside the designated period can be changed from
those within the designated period.
[0079] Each color scale after the change as shown in (C) of FIG. 3
and (C) of FIG. 5 can also be changed dynamically. Specifically,
plural color scales can be generated by changing at least one of a
phase and a period of change in pixel value of a color scale as
shown in (C) of FIG. 3 or (C) of FIG. 5. Changing a phase of change
in pixel value corresponds to shifting a color scale in the time
phase direction. Meanwhile, changing a period of change in pixel
value corresponds to expanding or contracting a color scale in the
time phase direction.
[0080] FIG. 7 shows an example of color scales generated for
dynamically changing the color scale shown in (C) of FIG. 3, and
FIG. 8 shows an example of color scales generated for dynamically
changing the color scale shown in (C) of FIG. 5.
[0081] Each of (A) of FIG. 7 and (A) of FIG. 8 shows concentration
profiles of a contrast agent at two dimensional positions (xi, yj)
(i=1, 2, 3, . . . , m; j=1, 2, 3, . . . , n) and arrival time
phases Tmax(xi, yj) of the contrast agent specified based on the
maximum values MAXs of the concentration profiles. Therefore, in
each graph shown in (A) of FIG. 7 and (A) of FIG. 8, the horizontal
axis shows time phases and the vertical axis shows relative signal
intensities corresponding to concentrations of the contrast
agent.
[0082] When a color scale, in which the change in pixel value for
one period is assigned multiple times as shown in (C) of FIG. 3, is
changed dynamically, what is necessary is to generate plural color
scales by shifting the color scale shown in (C) of FIG. 3 in the
change direction of the pixel value, as shown in (B) of FIG. 7.
Similarly, when a color scale, in which the change in the pixel
value for one period is assigned to the designated period as shown
in (C) of FIG. 5, is changed dynamically, what is necessary is to
generate plural color scales by shifting the color scale shown in
(C) of FIG. 5 in the change direction of the pixel value, as shown
in (B) of FIG. 8.
[0083] When the color coding of parametric image data is performed
using color scales having different color schemes as described
above, frames of parametric image data corresponding to the color
scales are generated. Thus, it becomes possible to display the
frames of generated parametric image data in the color scale
direction as a moving image.
[0084] For example, in the example shown in (B) of FIG. 8,
parametric image data can be generated, using the plural color
scales, as a moving image in which changes in pixel values
different from each other have been assigned to a period shorter
than the period from the initial time to the ending time of time
changes in concentrations of a contrast agent. Furthermore, plural
color scales may be generated by changing not only a phase of
change in pixel value but also a period of the change in pixel
value, as described above.
[0085] As described above, blood vessel image data can be generated
as a moving image according to plural color scales generated by
changing at least one of a phase and a period of change in pixel
value for at least one period. When parametric image data as blood
vessel image data are displayed as a moving image, blood and a
contrast agent can be displayed in color as if they flowed.
[0086] Note that, parametric image data can be generated, using the
color scales, as a moving image having a frame interval different
from that of X-ray contrast image data. That is, a frame interval
for switching a color scale to a different color scale can be set
to a desirable interval appropriate for a diagnosis, independently
of the frame interval of the X-ray contrast image data. Therefore,
a moving speed of the colors which simulate blood flows can be set
to a desired speed.
[0087] Therefore, it becomes possible to understand flows of a
contrast agent and blood more easily. In particular, human eyes
have high visibility to red. Therefore, generating a moving image
in which red moves during a focused period from the starting time
phase T1 to the ending time phase T2 allows easy understanding of a
blood flow dynamic state in a focused region.
[0088] As a specific example, when colors are changed in the
designated period as shown in (B) of FIG. 8, a color corresponding
to each time phase can be changed in time. In this case, a color
changes among red, green and blue even at a same time phase. With
regard to the outside of the designated period, colors at the
starting time phase T1 and the ending time phase T2 can be
gradually changed into white respectively, or the transmittances of
colors can be changed.
[0089] Meanwhile, in the case of the color scale in which color
values have been changed periodically as shown in (B) of FIG. 7,
plural color scales can be generated by gradually changing the
initial color value in each period, as mentioned above.
[0090] The color values including the R value, the G value and the
B value can also be changed into values other than the maximum
values. Specifically, when parametric image data are generated by
the above-mentioned color scale, a brightness value at each pixel,
at which a value of a concentration profile of a contrast agent has
not become zero by low-pass filtering processing or the like,
becomes the maximum value. That is, a brightness value at each
pixel at which a contrast agent arrived becomes the maximum value,
regardless of a concentration of the contrast agent.
[0091] Thus, brightness values of parametric image data can be
changed so that concentrations of a contrast agent can be
understood. In other words, parametric image data having brightness
values according to concentrations of a contrast agent at a
specific condition, such as the maximum values, can be generated as
blood vessel image data.
[0092] Specifically, when the maximum R value, G value and B value
before the change in brightness values are R.sub.0, G.sub.0 and
B.sub.0, respectively, the R value, G value and B value after the
change in brightness values can be determined by multiplying each
of the values R.sub.0, G.sub.0 and B.sub.0 by a coefficient k, as
shown in expression (1).
(R,G,B)=(kR.sub.0,kG.sub.0,kB.sub.0) (1)
[0093] In expression (1), the coefficient k is set to a value not
less than zero and not more than one, corresponding to a
concentration of a contrast agent. For example, the coefficient k
can be determined by expression (2).
k=P(x,y)/P.sub.0 (2)
[0094] wherein P(x, y) represents a value, corresponding to a
specific condition such as the maximum value, of a concentration
profile of a contrast agent at a position (x, y), obtained as an
image signal value of X-ray contrast image data or DSA image data,
and P.sub.0 represents a constant.
[0095] When the coefficient k is set by expression (2), the
coefficient k becomes a value proportional to the value P(x, y) of
a concentration profile of a contrast agent. Therefore, the
brightness values (R, G, B) of parametric image data can also be
brightness values each proportional to the value P(x, y) of a
concentration profile of a contrast agent. Furthermore, brightness
values at a pixel where a concentration of a contrast agent is a
noise level and brightness values at a pixel where noises have
actually occurred can be made small enough.
[0096] The constant P.sub.0 can be set to the maximum value of the
value P(x, y) of a concentration profile of a contrast agent in
spatial directions, or an arbitrary value which has been determined
empirically. Note that, when the constant P.sub.0 is set to a value
smaller than the maximum value of the value P(x, y) of a
concentration profile of a contrast agent, the coefficient k may
become a value larger than one, by the calculation of expression
(2). In such a case, the coefficient k has only to be set to
one.
[0097] Then, when a pixel value adjusted by expression (1) is
assigned to each pixel position (x, y), parametric image data in
which blood vessels have been depicted in colors and brightness
according to arrival time phases and concentrations of a contrast
agent can be generated. Note that, the adjustment of brightness
values shown in expression (1) can be performed at the time of the
color coding in the color coding part 23.
[0098] The parametric image data generated in the parametric image
generation part 21 as described above can be displayed on the
display 14, similarly to X-ray contrast image data or DSA image
data. Furthermore, the parametric image data can be stored in the
image memory 16 as necessary.
[0099] FIG. 9 shows an example of parametric image generated in the
parametric image generation part 21 shown in FIG. 1.
[0100] In a parametric image, blood vessels into which a contrast
agent has been injected are displayed in color while brightness
values become zero in regions without the contrast agent, as shown
in FIG. 9. Furthermore, the blood vessels are depicted as a region
or regions where colors change according to arrival times of the
contrast agent. Therefore, how blood and the contrast agent flow
can be observed by colors.
[0101] In the X-ray diagnostic apparatus 1 and the medical image
processing apparatus 12 having the functions and configurations as
described above, the imaging system 2 and the control system 3
cooperating with each other function as an image acquisition system
configured to acquire at least X-ray contrast image data from the
object O. Furthermore, the time phase specifying part 22 and the
color coding part 23, cooperating with each other, of the
parametric image generation part 21 function as a blood vessel
image generation part configured to obtain time changes in
concentrations of a contrast agent based on at least X-ray contrast
image data, and generate blood vessel image data, having pixel
values corresponding to times at which the concentrations of the
contrast agent become a specific condition, according to a color
scale. In addition, the color scale adjustment part 24 of the
parametric image generation part 21 functions as a pixel value
scale generation part configured to generate a color scale by
assigning a change in pixel value for at least one period, to a
period shorter than the period from the initial time to the ending
time of the time changes in the concentrations of the contrast
agent.
[0102] Note that, the X-ray diagnostic apparatus 1 and the medical
image processing apparatus 12 may be configured by other elements
so long as similar functions as the image acquisition system, the
blood vessel image generation part and the pixel value scale
generation part are provided in the X-ray diagnostic apparatus 1
and the medical image processing apparatus 12. For example, the
medical image processing apparatus 12 may be configured by
installing a medical image processing program, which makes a
computer function as the blood vessel image generation part and the
pixel value scale generation part, to the computer. In that case,
the medical image processing program can be recorded in an
information recording medium to be distributed as a program product
so that a general purpose computer can be used as the medical image
processing apparatus 12.
[0103] Next, an operation and an action of the X-ray diagnostic
apparatus 1 and the medical image processing apparatus 12 will be
described.
[0104] FIG. 10 is a flow chart which shows an operation of the
X-ray diagnostic apparatus 1 shown in FIG. 1 and processing in the
medical image processing apparatus 12 shown in FIG. 1.
[0105] First, in step S1, X-ray image data are acquired without a
contrast agent. Specifically, the imaging system 2 moves to a
predetermined position and an X-ray is exposed from the X-ray tube
6 towards an object O set on the bed 10, under control by the
control system 3. Then, the X-ray which has transmitted the object
O is acquired as X-ray projection data by the X-ray detector 7. The
X-ray projection data acquired by the X-ray detector 7 are output
as X-ray image data to the medical image processing apparatus 12
through the A/D converter 11.
[0106] The X-ray image data may be acquired for one frame or
multiple frames. When multiple frames of the X-ray image data are
acquired and the addition average of the multiple frames of the
X-ray image data is calculated in the filtering part 18, one frame
of non-contrast X-ray image data whose noises have been reduced can
be generated. Subsequently, the non-contrast X-ray image data
acquired as mentioned above are stored in the image memory 16.
[0107] Next, in step S2, X-ray contrast image data are acquired
continuously. For that purpose, the contrast agent injector 15
operates under a control by the control system 3, and a contrast
agent is injected into the object O. Subsequently, after a preset
time has passed from the start time of the contrast agent
injection, the acquisition of the X-ray contrast image data starts.
Then, the acquisition of the X-ray contrast image data is performed
continuously in a predetermined period. Thereby, the time series
X-ray contrast image data are stored sequentially in the image
memory 16. The flow of acquiring the X-ray contrast image data is
similar to the flow of acquiring non-contrast X-ray image data.
[0108] Next, in step S3, the DSA image data are generated by the
subtraction part 17. More specifically, the time series DSA image
data are generated sequentially by subtraction processing of the
time series X-ray contrast image data using the non-contrast X-ray
image data as mask image data. The generated time series DSA image
data are stored sequentially in the image memory 16.
[0109] The time series X-ray contrast images or the time series DSA
images can be displayed as live images in real time on the display
14. Furthermore, the time series X-ray contrast images or the time
series DSA images can be also displayed on the display 14 after the
X-ray imaging. When the DSA images are displayed afterward, the DSA
image data can be generated by performing subtraction processing
for only a time phase period designated by an operation of the
console 5.
[0110] Next, in step S4, time changes in concentrations of the
contrast agent are generated by the time phase specifying part 22.
Specifically, the time series X-ray contrast image data or the time
series DSA image data in a time phase period designated by
operations of the console 5 are taken into the time phase
specifying part 22. Then, a concentration profile showing a time
change in concentration of the contrast agent as shown in (A) of
FIG. 3 or (A) of FIG. 5 is generated for every pixel position in
the time phase specifying part 22.
[0111] Note that, the filtering part 18 can perform one or both of
low-pass filtering processing and running average processing in one
or both of spatial directions and the time direction, as
preprocessing or postprocessing of the generation of the
concentration profiles of the contrast agent. Thereby, smooth
concentration profiles, of the contrast agent, having less noises
can be generated. In addition, concentration profiles of the
contrast agent whose data intervals are shorter than sampling
intervals can also be generated by interpolation processing,
gravity center calculation, or curve fitting in the time phase
specifying part 22.
[0112] Next, in step S5, arrival time phases of the contrast agent
at the respective pixel positions are identified, by the time phase
specifying part 22, based on the concentration profiles of the
contrast agent. Specifically, the arrival time phase of the
contrast agent can be identified for every pixel position by data
processing, such as peak detection processing or threshold value
processing, of the concentration profiles of the contrast
agent.
[0113] Note that, after the time phases have been specified by the
data processing such as peak detection processing or threshold
value processing, continuous concentration profiles only in periods
close to the specified time phases may be calculated by
interpolation processing, gravity center calculation, or curve
fitting. In that case, the true arrival time phases of the contrast
agent are detected by data processing, such as peak detection
processing or threshold value processing, of the acquired
continuous concentration profiles, for the second time.
[0114] Next, in step S6, the color scale adjustment part 24
generates a color scale for color coding of a two dimensional map
of the arrival time phases of the contrast agent acquired by the
time phase specifying part 22. The color scale adjustment part 24
can generate not only a general color scale whose color phase
changes continuously from the initial time phase to the last time
phase at a constant rate of change as shown in (B) of FIG. 3 or (B)
of FIG. 5 but also a color scale as shown in (C) of FIG. 3 or (C)
of FIG. 5 by increasing a change rate in color phase of a normal
color scale.
[0115] In a case of generating a color scale whose color phase
changes continuously and periodically as shown in (C) of FIG. 3,
the color scale can be generated by specifying the period Tscale,
in which the color phase changes, and changing the color phase in
each period Tscale, by an operation of the console 5.
Alternatively, these necessary conditions may be previously set as
default values. A color phase at the starting time phase in each
period Tscale can be designated arbitrarily. Furthermore, when a
color phase at the initial time phase of concentration changes of a
contrast agent is not set to a color phase at the starting time
phase in each period Tscale, the color phase at the initial time
phase needs to be designated.
[0116] Meanwhile, in a case of generating a color scale having a
continuous color phase change, within a designated time phase
period, different from that outside the designated time phase
period, as shown in (C) of FIG. 5, the color scale can be generated
by designating the starting time phase T1 and the ending time phase
T2 of the time phase period, to which the continuous color phase
change is assigned, by operation of the console 5. The starting
time phase T1 and the ending time phase T2 can be designated by
selecting an image from the time series X-ray contrast images or
the time series DSA images displayed on the display 14 by operation
of the console 5.
[0117] Next, in step S7, the color coding part 23 performs color
coding, of the two dimensional map of the arrival time phases of
the contrast agent, based on the color scale generated by the color
scale adjustment part 24. Specifically, an R value, a G value, and
a B value corresponding to an arrival time phase of the contrast
agent are assigned to each pixel, as pixel values, according to the
color scale. Thereby, parametric image data are generated.
[0118] At this time, it is desirable to multiply each of the R
value, the G value and the B value by a coefficient corresponding
to a concentration of the contrast agent at the arrival time phase
of the contrast agent. Thereby, parametric image data can be
generated so that a brightness value at a pixel, at which a
concentration of the contrast agent at the arrival time phase of
the contrast agent is relatively high, is relatively high while a
brightness value at a pixel, at which a concentration of the
contrast agent at the arrival time phase of the contrast agent is
relatively low, is relatively low.
[0119] Then, the parametric image generated as described above can
be displayed on the display 14. The parametric image can also be
displayed as a moving image by shifting, and/or expanding or
contracting the color scale in the time phase direction.
Consequently, observing the parametric image allows a user to
recognize blood vessels into which a contrast agent flows. In
particular, a color phase change in the color scale has been
assigned to a short time phase period, and therefore, blood vessels
in which arrival time phases of a contrast agent are near to each
other can be easily distinguished by a difference in color.
[0120] That is, the X-ray diagnostic apparatus 1 and the medical
image processing apparatus 12 as described above are configured to
generate blood flow image data in color by color coding of specific
time phases, such as arrival time phases, of a contrast agent with
a color scale according to time phases and contract a continuous
color phase change of the color scale in the time phase direction
in order to improve time phase identification ability by color.
[0121] Therefore, according to the X-ray diagnostic apparatus 1 and
the medical image processing apparatus 12, adjacent blood vessels
can be easily distinguished as a difference in color phase even
when a difference in inflow time phase, arrival time phase or
outflow time phase of a contrast agent is small among the blood
vessels.
[0122] In particular, it is important to observe a blood flow into
a disease part between arteries and veins, in a diagnosis of a
cerebral arteriovenous malformation or a dural arteriovenous
fistula. Therefore, it is necessary to distinguish blood vessels
into which a contrast agent flows. However, DSA images are
displayed with a gray scale, and therefore, distinguishing
contrast-enhanced blood vessels is difficult.
[0123] In contrast, the X-ray diagnostic apparatus 1 and the
medical image processing apparatus 12 are configured to be able to
set a period of a color phase change in a color scale to be short,
according to a time phase difference which should be identified.
Accordingly, colors change for every blood vessel even when a
contrast agent flows into focused blood vessels almost
simultaneously. Therefore, the blood vessels can be easily
distinguished.
[0124] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the novel
methods and systems described herein may be embodied in a variety
of other forms; furthermore, various omissions, substitutions and
changes in the form of the methods and systems described herein may
be made without departing from the spirit of the inventions. The
accompanying claims and their equivalents are intended to cover
such forms or modifications as would fall within the scope and
spirit of the inventions.
[0125] For example, an example case of generating blood vessel
image data as color parametric image data, using a color scale, has
been described in the embodiment described above. Alternatively,
blood vessel image data may also be generated using a gray scale.
Specifically, blood vessel image data having pixel values
corresponding to times when concentrations of a contrast agent
become a specific condition can be generated according to a gray
scale or a color scale. Furthermore, a gray scale or a color scale
can be generated by assigning a change in pixel value to a period
shorter than the period from the initial time to the ending time of
time changes in concentrations of a contrast agent.
[0126] When blood flow image data are generated using a gray scale,
a continuous change in brightness value instead of a color phase
change is to be assigned, as a change in pixel value, to a period
shorter than the period from the initial time to the ending time of
time changes in concentrations of a contrast agent. In that case,
each brightness value can also be set to a value according to a
concentration of the contrast agent by multiplying the brightness
value by a coefficient k according to the concentration of the
contrast agent.
[0127] Similarly, when blood flow image data are generated using a
color scale, not only a continuous color phase change but a
continuous change in brightness value can also be assigned as a
change in pixel value as described above. In that case, each
brightness value can also be set to a value according to a
concentration of a contrast agent by multiplying the brightness
value by a coefficient k according to the concentration of the
contrast agent.
[0128] As described above, a change in pixel value assigned to a
period shorter than the period from the initial time to the ending
time of time changes in concentrations of a contrast agent may be a
continuous color phase change, a continuous change in color
brightness value, or a continuous change in gray brightness
value.
[0129] In addition, the X-ray diagnostic apparatus 1 of which the
X-ray tube 6 and the X-ray detector 7 have been fixed to the both
ends of the C-shaped arm 8 has been exemplified in the embodiment
described above. Similarly, an X-ray diagnostic apparatus having
another structure can also generate parametric image data. Examples
of an X-ray diagnostic apparatus having another structure include
an X-ray diagnostic apparatus of which each of the X-ray tube 6 and
the X-ray detector 7 is fixed to an independent arm, besides an
X-ray diagnostic apparatus having multiple arms or an X-ray
diagnostic apparatus including movement structures for moving
arbitrary arms along axes in arbitrary directions, such as an arc
axis or a straight axis. When each of the X-ray tube 6 and the
X-ray detector 7 is fixed to an independent arm, it is practical to
install driving structures, such as an expansion and contraction
structure, a rotating structure, a joint structure and a link
mechanism, on each of the first arm holding the X-ray tube 6 and
the second arm holding the X-ray detector 7.
[0130] Further, an example case of generating parametric image
data, which are blood vessel image data having pixel values
corresponding to times at which concentrations of a contrast agent
become a specific condition, based on X-ray contrast image data
acquired by the X-ray diagnostic apparatus 1 has been described in
the embodiment described above. However, parametric image data may
also be generated based on blood vessel image data acquired by
another image diagnostic apparatus (modality).
[0131] For example, in a case of using an MRI (magnetic resonance
imaging) apparatus, MRA (magnetic resonance angiography) image data
or non-contrast MRA image data can be acquired as contrast imaging
or non-contrast imaging. In a case of acquiring contrast MRA image
data, blood flow dynamic state information can be obtained as time
changes in concentrations of a contrast agent. Meanwhile, in a case
of acquiring non-contrast MRA image data, blood flow dynamic state
information can be obtained as changes in image values enhanced by
applying a spin labeling pulse, such as an ASL (arterial spin
labeling) pulse, or an imaging method, such as a TOF (time of
flight) method.
[0132] On the other hand, in a case of acquiring 4D (four
dimensional) X-ray CT (computed tomography) contrast image data
using an X-ray CT apparatus, blood flow dynamic state information
can be obtained as time changes in concentrations of a contrast
agent. Alternatively, an ultrasonic contrast scan using an
ultrasonic diagnostic apparatus can also obtain blood flow dynamic
state information as time changes in concentrations of a contrast
agent.
[0133] Whether contrast blood vessel image data have been acquired
by an image diagnostic apparatus or non-contrast blood vessel image
data have been acquired, blood flows can be observed as time
changes in pixel values corresponding to blood vessels.
[0134] Therefore, in a case of generating parametric image data
based on blood vessel image data acquired by an arbitrary image
diagnostic apparatus, a medical image processing apparatus has a
blood vessel image generation part which is configured to obtain
time changes in pixel values corresponding to blood vessels, based
on the blood vessel image data acquired by the image diagnostic
apparatus, and generate blood vessel image data, having pixel
values corresponding to times at which the pixel values
corresponding to the blood vessels become a specific condition,
according to a gray scale or a color scale. Furthermore, the
medical image processing apparatus has a pixel value scale
generation part which is configured to generate the gray scale or
the color scale, by assigning a change in pixel value for at least
one period, to a period shorter than the period from the initial
time to the ending time of the time changes in the pixel values
corresponding to the blood vessels.
* * * * *