JPH09299366A - Region extract device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extract a region with high accuracy by changing a threshold value used in outline extraction to again extract an outline if a difference between the time series data and the smoothed data exceeds a threshold value. SOLUTION: Image data is read from an image memory 21 and input to an extract means 22 to extract the outline of the left ventricle of the heart shown on a tomographic image of the heart which image data bears. The time series data is obtained from the data showing the extracted outline of the left ventricle by an arithmetic means 23, and the time series data is input to a smoothing means 24. The time series data is smoothed by the smoothing means 24 to obtain the smoothed data, and a determining means 25 determines whether a difference between the time series data and the smoothed data of each tomographic image exceeds a second threshold value or not. The determination result is feedbacked to the extracting means 22, and in the extracting means 22, if it is determined by the determining means 25 that the difference exceeds the second threshold, a first threshold value used in outline extraction is changed to again extract the outline.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organ region or a tissue in an organ based on image data representing a tomographic image of an organ of a subject (mainly a human body) obtained by an ultrasonic diagnostic apparatus, MRI or the like. The present invention relates to a region extraction device that extracts a region of.

[0002]

2. Description of the Related Art Conventionally, an ultrasonic wave is transmitted to an object, particularly a human body, and the ultrasonic wave reflected and returned by the tissue in the object is received to obtain a reception signal. An ultrasonic diagnostic apparatus is used for diagnosing diseases such as internal organs by displaying a tomographic image in a specimen.In recent years, in order to make diagnosis of the disease easier, the left side that appears in the tomographic image of the heart is used. It is required to extract and display the region of the ventricle, or to display the area of the left ventricle, the volume of the left ventricle estimated from the size of the left ventricle, or their temporal changes.

FIG. 11 is a diagram showing a display example of a tomographic image of the heart by the ultrasonic diagnostic apparatus. As shown in FIG. 11, the average value of the data values of the image data greatly differs between the myocardial portion and the blood flow portion, and therefore, as a basic process, the image data is binarized using a predetermined threshold value. Thus, the myocardial portion and the blood flow portion can be separated, and the region of the left ventricle that is a part of the blood flow portion can be obtained.

When obtaining the region of the left ventricle appearing on the tomographic image based on the image data representing one tomographic image as shown in FIG. 11, in order to obtain the region with higher accuracy, it is simply a binary value. In addition to the chemical treatment, various ideas have been proposed (see, for example, Japanese Patent Application Nos. 6-297071 and 7-285053).

[0005]

12 and 13 are diagrams showing the contour of the left ventricle obtained by the process including the binarization process using the threshold value. When the region of the left ventricle is extracted by comparing the image data with the threshold value, if the threshold value is not appropriate, the region of the right ventricle is regarded as the region of the left ventricle as shown in FIG. It may end up. Further, as shown in FIG. 13, it may be recognized as a smaller area than originally.

In view of the above circumstances, it is an object of the present invention to provide an area extracting device which can extract an area with high accuracy by using an appropriate threshold value.

[0007]

The area extracting apparatus of the present invention which achieves the above object is an image carrying a tomographic image of a subject including a desired organ or tissue, which is sequentially obtained at predetermined frame time intervals. Based on the data, the region of the organ or tissue appearing on the tomographic image is extracted, and in the region extraction device for obtaining the time change of the area of the region or the volume of the organ or tissue estimated from the region, the image data By performing a process including a threshold process using a predetermined first threshold value on the tomographic image to extract a contour of a desired organ or tissue appearing on a tomographic image carried by the image data, and an extracting unit. And a calculation means for obtaining time-series data representing the temporal change of the area of the region surrounded by the contours or the volume of the organ or tissue estimated from the region. Smoothing means for obtaining smoothed data by smoothing the time-series data obtained by the computing means, and determining whether the difference between the time-series data and the smoothed data exceeds a second threshold value. A determining unit, and the extracting unit re-extracts the contour by changing the first threshold when the determining unit determines that the difference exceeds the second threshold. Is characterized by.

Here, in the area extracting apparatus of the present invention, the judging means exceeds which of the second thresholds of the difference and the second thresholds of a plurality of stages, or which of the second thresholds. To determine whether or not
The extraction means may re-extract the contour using the first threshold value in accordance with a second threshold value that exceeds the difference among a plurality of second threshold values.

In the region extracting apparatus of the present invention, the size of the region of the desired organ or tissue appearing on the tomographic images obtained at the neighboring times among the tomographic images sequentially obtained in time series is approximately the same. The difference is compared with the second threshold value, and when the difference exceeds the second threshold value, that is, the area or volume of the region on the adjacent tomographic image is extremely different. When the area or volume is obtained, the first threshold for obtaining the contour of the region is changed and the contour is obtained again, so that finally,
It is prevented that the area is recognized as an excessively large area or an excessively small area, and an area having an appropriate width is extracted by an appropriate first threshold value.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 is a block diagram showing the configuration of an embodiment of the area extraction device of the present invention. For example, in an ultrasonic diagnostic apparatus or a diagnostic apparatus 10 such as MRI, image data carrying a tomographic image of the heart including the entire tomographic plane of the left ventricle inside is obtained at desired frame time intervals, and the obtained image data But,
It is input to the area extraction device 20 as one embodiment of the present invention and temporarily stored in the image memory 21.

The image data once stored in the image memory 21 is read from the image memory 21 and input to the extraction means 22. The extraction means 22 extracts the contour of the left ventricle that appears on the tomographic image of the heart carried by the sent image data. This contour extraction is basically performed by binarizing the sent image data with a predetermined first threshold value. However, not only the binarization processing but also the above-mentioned proposal, for example, is adopted. However, it is desirable to extract the left ventricle as accurately as possible.

The data representing the contour of the left ventricle extracted by the extracting means 1 is input to the calculating means 23. The calculation means 23 obtains data representing the area of the region surrounded by the contour of the left ventricle, or the volume of the rotating body determined by rotating the region around a predetermined central axis, for example. The data representing this area or volume is
Time-series data that is obtained corresponding to each image data that is sequentially obtained by the diagnostic device 10 at desired frame time intervals and that represents the temporal change of the area or volume as a whole is obtained.

The time series data obtained by the calculating means 23 is input to the smoothing means 24. The smoothing means 24 smoothes the input time series data by, for example, a moving average method, and thereby obtains smoothed data. Time-series data obtained by the calculating means 23 and the smoothing means 24
The smoothed data obtained in step 3 is input to the determination means 25. The determination means 25 determines whether or not the difference between the tomographic images of the time-series data and the smoothed data exceeds a predetermined second threshold value. This determination result is fed back to the extraction means 22, and in the extraction means 22, when the determination means 25 determines that the difference exceeds the second threshold, the first threshold is changed and changed. The re-extraction of the contour of the left ventricle is performed using the first threshold value.

Here, in the judging means 25, the difference is compared with each of the plurality of second threshold values, and in the extracting means, the second threshold value out of the plurality of second threshold values is exceeded. The contour of the left ventricle may be re-extracted using the corresponding first threshold value. The image data once stored in the image memory 21, the data representing the contour of the left ventricle extracted by the extracting means 22, the time series data obtained by the computing means 23, the smoothed data obtained by the smoothing means 24, and The result of the determination made by the determination means 25 is sent to the display device 30 as necessary and displayed on a display screen (not shown) of the display device 30.

The extracting means 22, the calculating means 23, the smoothing means 24 and the judging means 25 may be composed of hardware which satisfies their respective functions, or
The area extraction device 20 may be equipped with a CPU, and one or more or all of these means 22 to 25 may be configured by software executed by the CPU.

Each specific embodiment will be described below. 2 and 3 show the left ventricular contour of the first embodiment of the first embodiment of the present invention when the left ventricle contour is first extracted and when it is extracted again, respectively.
It is a figure which shows the time series change (a) of a tomographic image, and the time series change (b) of the area of a contour area.

In FIG. 2 showing the state at the time when the left ventricle contour part is first extracted, as shown in FIG. 2 (a), as the first threshold value for extracting the left ventricle contour by the extraction means 22, The threshold value a is adopted for all the tomographic images arranged in series. The area of the in-contour region obtained from each of these tomographic images in the extracting means 23 shown in FIG. 1 is as shown in the graph of the instantaneous data (time-series data in the present invention) of FIG. 2B, for example. Become.

The smoothing means 24 smoothes this instantaneous data using the following moving average method to obtain the data shown in FIG.
The smoothed data shown in (b) is obtained. y (t) at time t
Is the data representing the area of the in-contour region obtained for each tomographic image, and the smoothed data is y '(t), which is the moving average method.

[0019]

[Equation 1]

However, k _i (i = 0, 1, ..., 2n) is a constant. Thus, smoothed data is obtained. As shown in FIG. 2B, the determination means 25 adopts a threshold difference ± α as the second threshold, and determines whether the difference between the instantaneous data and the smoothed data exceeds the range of ± α. To be done.

The threshold value a adopted as the first threshold value by the extracting means 22 is not an appropriate threshold value, but instantaneous data taken up into the contour up to the right ventricle is obtained, and the instantaneous data exceeds the range of ± α. Therefore, the judgment means 25 transmits the judgment result that the range of ± α is exceeded to the extraction means 22, and the extraction means 22 receives the judgment result, and FIG.
As shown in (a), the first threshold is changed to the threshold b, and the left ventricle contour is re-extracted for all tomographic images.
As a result, as shown in FIG. 3B, for all the tomographic images, data in which the difference between the instantaneous data and the smoothed data falls within the range of ± α is obtained.

FIGS. 3 and 4 are views similar to FIGS. 1 and 2, respectively, in a second embodiment of the concrete embodiment of the present invention. In the second embodiment, as shown in FIG. 5A, only the tomographic image when the difference between the instantaneous data and the smoothed data deviates from the region of ± α is extracted by the extracting means 22 for contour extraction. The threshold value of 1 is changed to the threshold value c. In this way, the contours may be re-extracted by changing the threshold value only for the tomographic image for which the contours that are too large or too small are obtained.

FIGS. 6 and 7 are views similar to FIGS. 2 and 3, respectively, in the third embodiment of the concrete embodiment of the present invention. In the third embodiment, the determination means 25 uses two-step threshold values α and β as the second threshold value as shown in FIG. 6B, and the instantaneous data for a certain tomographic image is Only the threshold value α is exceeded, and the instantaneous data for another tomographic image exceeds the threshold value β.

Therefore, the extracting means 22 sets the threshold value for contour extraction to the threshold value a for the tomographic image which exceeds only the threshold value α.
Is changed to a threshold value b having a slightly different value, and a tomographic image exceeding the threshold value β is changed from the threshold value α to a threshold value c having a larger value, and the contours of these tomographic images are re-extracted. As described above, the determination unit 25 may adopt a plurality of threshold values and change the threshold value for contour extraction according to which threshold value is exceeded.

8 to 10 are respectively the first contour extraction time point, the second contour extraction time point, and the third contour extraction time in the fourth embodiment of the present invention. It is a figure which shows the time series change (a) of a tomographic image (contour) at the time, and the time series change (b) of the area of an area | region in a contour.
At the time of the first contour extraction, the determination means 25 is set as shown in FIG.
As shown in (b), a large threshold value β is used. At this time, for one tomographic image, the difference between the instantaneous data and the smoothed data exceeds the threshold β.

Then, next, in the extraction means 22, the process shown in FIG.
As shown in (a), for a tomographic image that exceeds the threshold β, the contour extraction threshold is changed to a threshold b corresponding to the threshold β, and contour extraction is performed.
As shown in FIG. 9B, the threshold value α is smaller than the threshold value β.
Is used to make the determination. This time, another tomographic image is the threshold α
Since it has exceeded the limit, this time, in the extracting means 22,
As shown in (a), for a tomographic image that exceeds the threshold value α,
The threshold value for contour extraction is changed to the threshold value c corresponding to the threshold value α, and contour extraction is performed. In this way, the determination means 25 may make the determination using only one threshold value at a time, and repeat the determination while changing the threshold value. In this case, it is preferable to set an upper limit of the number of repetitions in order to prevent infinite repetition.

In the above description, the case where the area surrounded by the extracted contours is too large has been described as an example, but the present invention can be similarly applied to the case where the area is too small. Further, in the above, the case where the area of the region surrounded by the contour is obtained has been described. However, instead of the area, for example, a rotating body having a cross section of the region surrounded by the contour is assumed and the volume of the rotating body is obtained. Good.

Further, in the above description, a tomographic image of the heart obtained by the ultrasonic diagnostic apparatus is assumed, but the present invention is applicable to a tomographic image other than the ultrasonic diagnostic apparatus, for example, obtained by MRI. It can be applied to other organs other than the heart.

[0029]

As described above, according to the present invention,
It is possible to prevent the desired organ or tissue from which the contour is to be extracted from being extracted excessively or excessively smallly, and realize highly accurate extraction.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a region extraction device of the present invention.

FIG. 2 is a time-series change (a) of a tomographic image and a time-series change of the area of the in-contour region when the left ventricle contour is first extracted in the first embodiment of the specific embodiments of the present invention. It is a figure which shows (b).

FIG. 3 is a time-series change (a) of a tomographic image and a time-series change of the area of the in-contour region when the left ventricle contour is re-extracted in the first embodiment of the specific embodiments of the present invention. (B)
FIG.

FIG. 4 is a time-series change (a) of a tomographic image and a time-series change of the area of the in-contour region when the left ventricle contour is first extracted in the second embodiment of the specific embodiments of the present invention. It is a figure which shows (b).

FIG. 5 is a time-series change (a) of the tomographic image and a time-series change of the area of the in-contour region at the time point when the contour of the left ventricle is re-extracted in the second embodiment of the concrete embodiments of the present invention. (B)
FIG.

FIG. 6 is a time-series change (a) of a tomographic image and a time-series change of the area of the in-contour region when the left ventricle contour is first extracted in the third embodiment of the concrete embodiments of the present invention. It is a figure which shows (b).

FIG. 7 is a time-series change (a) of a tomographic image and a time-series change of the area of the in-contour region at the time of re-extracting the contour of the left ventricle in the third embodiment of the concrete embodiments of the present invention. (B)
FIG.

FIG. 8 is a time-series change (a) of the tomographic image (contour) and a time-series change of the area of the contour area at the time of the first contour extraction in the fourth embodiment of the specific embodiments of the present invention. It is a figure which shows (b).

FIG. 9 is a time-series change (a) of the tomographic image (contour) and a time-series change of the area of the in-contour region at the time of the second contour extraction in the fourth embodiment of the concrete embodiments of the present invention. It is a figure which shows (b).

FIG. 10 is a time-series change (a) of the tomographic image (contour) and a time-series change of the area of the contour area at the time of the third contour extraction in the fourth embodiment of the concrete embodiments of the present invention. It is a figure which shows (b).

FIG. 11 is a diagram showing a display example of a tomographic image of the heart by the ultrasonic diagnostic apparatus.

FIG. 12 is a diagram showing a contour of a left ventricle obtained by a process including a binarization process.

FIG. 13 is a diagram showing a contour of a left ventricle obtained by a process including a binarization process.

[Explanation of symbols]

 10 Diagnostic Device 20 Region Extraction Device 21 Image Memory 22 Extraction Means 23 Computing Means 24 Smoothing Means 25 Judging Means 30 Display Device

Claims (2)

[Claims] 1. Based on image data carrying a tomographic image of a subject including a desired organ or tissue, which is sequentially obtained at predetermined frame time intervals, the organ or tissue appearing on the tomographic image is displayed. In a region extraction device that extracts a region and obtains a temporal change in the area of the region or the volume of the organ or tissue estimated from the region, a process including a threshold process using a predetermined first threshold for the image data. By extracting the contour of the organ or tissue appearing on the tomographic image carried by the image data, and the area of the region surrounded by the contour extracted by the extracting unit or from the region Calculating means for obtaining time-series data representing estimated temporal changes in the volume of the organ or tissue, and smoothing the time-series data obtained by the calculating means. Smoothing means for obtaining smoothed data by determining the difference between the time-series data and the smoothed data, and a determining means for determining whether or not the difference between the time-series data and the smoothed data exceeds a second threshold value. A region extracting apparatus, wherein when the determination unit determines that the difference exceeds the second threshold value, the first threshold value is changed and the contour is extracted again. 2. The determining means determines whether the difference exceeds a second threshold value of the plurality of second threshold values or does not exceed any of the second threshold values. The extraction means re-extracts the contour using the first threshold value corresponding to the second threshold value that the difference exceeds among the plurality of second threshold values. The area extraction device according to item 1.