JP2000300557A - Ultrasonic diagnostic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily compare an image obtained at present with a reference image in the past by an ultrasonic diagnostic device. SOLUTION: Display attributes such as hues and the like of a tomographic image in the past stored in a storing part 32 are converted by an image data processing part 36. For example, the colored reference image is superimposed with a monochrome image of interest presently obtained from a probe 16 at DSC 24 to be displayed on a display part 40 as an overlay image integrated into one image. Moreover, a correlation index calculation part 30 calculates a correlation coefficient of data between the image of interest and the reference image. If a comparator part 34 detects that the correlation coefficient has exceeded a threshold, the image of interest in the overlay image is kept at a standstill at an image similar to the reference image, and the image of interest at this time is stored in a storage part 32.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus, and more particularly, to an ultrasonic diagnostic apparatus capable of comparing with past observation results.

[0002]

2. Description of the Related Art In a diagnosis based on an ultrasonic image, the same site is compared between different patients, and a time-dependent change in disease of the same patient is examined. In these cases, it is necessary to obtain ultrasound images on the same tomographic plane in order to be able to make useful comparisons. The tomographic plane scanned by the ultrasonic wave depends not only on the position where the ultrasonic probe is applied, but also on the direction of the transmitted and received ultrasonic waves.

[0003] It is a difficult task and requires a skill to perform an inspection with the same degree of freedom of the probe every time. As a measure to solve this difficulty, an ultrasonic tomographic image (reference tomographic image) obtained by a past inspection is displayed as a still image on a display screen of an ultrasonic diagnostic apparatus, and is arranged alongside the ultrasonic tomographic image currently being inspected. A method for displaying a tomographic image of interest, which is an image, can be considered. According to this method, an inspector who is a user of the diagnostic apparatus changes a contact position and an orientation of the ultrasonic probe while comparing two tomographic images on a screen, and searches for a condition for obtaining a desired tomographic image. become. According to this method, it is possible for the inspector to determine whether the current condition of the ultrasonic probe is satisfactory or not.

[0004]

However, in the above-described method of comparing two images displayed side by side, the judgment of the degree of coincidence between the two images largely depends on the qualitative judgment of the inspector, and also requires skill. In this respect, there is a problem that the load on the inspector is large.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide an ultrasonic diagnostic apparatus which performs a diagnosis based on comparison with a reference tomographic image, a tomographic slice which is valuable as a comparison object. It is to make it easier to obtain an image.

[0006]

An ultrasonic diagnostic apparatus according to the present invention comprises: a reference image storage means for storing a reference image based on past echo data obtained by transmitting and receiving ultrasonic waves;
An image generating unit that generates an image of interest based on currently obtained echo data; an overlay image generating unit that generates an overlay image in which the reference image and the image of interest are superimposed on each other so that they can be identified; Display means for displaying.

According to the present invention, the target image to be diagnosed is displayed while being superimposed on the reference image obtained in the past diagnosis. The reference image is an image to be compared with the target image. The target image and the reference image are not limited as long as they are the same type of image. That is, for example, they may be a three-dimensional image, an M-mode image, or the like, in addition to a tomographic image. In addition, the target image is usually generated based on the latest echo data at the time of diagnosis, but is generally not limited to that case. In other words, the "current" of the "currently obtained echo data" relating to the image of interest here means a time point to be a diagnosis target, and means a diagnosis time point different from the echo data of the reference image. According to the overlay image in which the reference image and the image of interest are superimposed, both images are presented to the inspector in a unified manner, and the inspector can easily grasp the presence or absence and the degree of the difference between the two images.

In a preferred aspect of the present invention, the overlay image generating means makes it possible to distinguish the superimposed reference image and the target image from each other by using a hue. It is. According to another preferred aspect of the present invention, the overlay image generation unit makes it possible to distinguish the superimposed reference image and the target image from each other by using luminance. Device.

In a preferred aspect of the present invention, there is provided a contour emphasizing means for emphasizing a contour of the reference image, and the overlay image generating means superimposes the contour-enhanced reference image on the target image. An ultrasonic diagnostic apparatus characterized in that: By emphasizing the outline, the reference image can be identified from the target image.

[0010] In another ultrasonic diagnostic apparatus according to the present invention, the reference image storage means stores the binarized reference image. The reference image is referred to for determining the contact position and the direction of the ultrasonic probe for acquiring the echo data for generating the image of interest. Basically, it is only necessary to specify the general shape of the image appearing in the reference image. According to the present invention, the data amount of the reference image stored in the reference image storage unit is suppressed while the features of the image are represented by binarizing the reference image.

An ultrasonic diagnostic apparatus according to the present invention comprises: a reference image storage means for storing a reference image based on past echo data obtained by transmission and reception of ultrasonic waves; and a target image based on currently obtained echo data. The image processing apparatus includes a target image generating unit that generates the target image, and a correlation evaluation unit that calculates a correlation index between the reference image and the target image.

According to the present invention, the difference between the reference image and the target image is quantitatively presented as a correlation index. The inspector determines the contact position of the ultrasonic probe so that the correlation index is reduced,
The direction can be adjusted. As the correlation index, for example, a correlation coefficient can be used, but it is not necessarily limited thereto.

In an ultrasonic diagnostic apparatus according to a preferred aspect of the present invention, the ultrasonic diagnostic apparatus further includes a binarizing unit for binarizing the reference image and the target image, and the correlation evaluating unit includes the binarizing unit. The correlation index between the reference image and the binarized image of interest is calculated. In addition to the correlation coefficient, for example, a value obtained by integrating the value of the exclusive OR for each pixel of both images in the image area can be used as the correlation index in this embodiment.

In a preferred aspect of the present invention, there is provided a contour extracting means for extracting a contour from each of the reference image and the image of interest, and the correlation evaluating means comprises a means for extracting each of the contours from the reference image and the image of interest. An ultrasonic diagnostic apparatus that calculates the correlation index based on a comparison between the contours.

Another ultrasonic diagnostic apparatus according to the present invention comprises:
An index display means for displaying the correlation index is provided. According to the present invention, the correlation index is presented to an inspector using the apparatus, and the inspector can use the correlation index based on the correlation index.
The degree of similarity between the target image and the reference image can be determined. For example, the correlation index can be numerically displayed on the image display device together with the image of interest, or can be displayed by an indicator displayed on the CRT.

The ultrasonic diagnostic apparatus according to the present invention is characterized in that it has an image storage means for detecting that the correlation index has exceeded a predetermined threshold value and storing the image of interest in a storage means. According to the present invention, a target image having a correlation index equal to or larger than a predetermined threshold, that is, a target image determined to be similar to the reference image is automatically recorded. The examiner can read the recorded image of interest from the storage unit and make a diagnosis based on comparison with the reference image and the like.

[0017] The ultrasonic diagnostic apparatus according to the present invention has an image freezing means for detecting that the correlation index has exceeded a predetermined threshold value, and freezing the noted image displayed on the display device as a moving image. I do. According to the present invention, when a target image having a correlation index equal to or greater than a predetermined threshold, that is, a target image determined to be similar to the reference image is obtained, the target image is displayed as a still image on the display device. You. The examiner can make a diagnosis by comparing the target image and the reference image, both of which are still images.

[0018]

FIG. 1 is a schematic block diagram of an ultrasonic diagnostic apparatus according to a preferred embodiment of the present invention. The present apparatus can generate a B-mode tomographic image, for example.
When a timing signal is output from the timing signal generator 10, the scanning controller 12 outputs a scanning control signal to the transceiver 14. As a result, a driving pulse is supplied from the transceiver 14 to the probe 16 at a predetermined transmission repetition cycle. An ultrasonic pulse is emitted from the probe 16 into the living body by the driving pulse, and the ultrasonic wave reflected in the living body is received by the probe 16. The probe 16 includes a vibrator array, and a received signal output from each vibrator is sent to the amplifier 17 via the transceiver 14 for each channel. After a predetermined amplification is performed by the amplifier 17, the received signal is converted into a digital signal by an A / D (analog to digital) converter 18, and the received signal for each channel is received and adjusted by a beamformer 19. By combining by phase processing, a reception beam is formed. The received signal output from the beamformer 19 is detected by a detector 20. Then, it is sent to a DSC (digital scan converter) 24 as tomographic image information. This DSC
Reference numeral 24 has an image synthesis function, an image interpolation function, and the like. On the other hand, the received signal output from the amplitude calculator 22 is branched and input to the correlation index calculator 30. That is, the data of the tomographic image of interest based on the echo data currently obtained in real time using the probe 16 is a DSC
24 and the correlation index calculation unit 30.

On the other hand, the storage section 32 stores tomographic images obtained by past diagnosis and the like. The tomographic image (reference tomographic image) read from the storage unit 32 is input to the correlation index calculating unit 30 together with the target tomographic image.

The correlation index calculator 30 calculates a correlation index that quantitatively indicates the degree of similarity between the tomographic image of interest and the reference tomographic image. The calculated correlation index is input to the comparison determination unit 34. The threshold for the correlation index is set in the comparison determination unit 34. When the correlation index is equal to or larger than the threshold, the comparison determination unit 34 determines that the two images are sufficiently similar. The determination result is used in the DSC 24 and the storage unit 32 as described later.

The reference tomographic image read out from the storage unit 32 is subjected to processing selected by the user among processings such as hue change and contour enhancement in the image data processing unit 36, and then input to the DSC 24. The DSC 24 generates an overlay image in which the reference tomographic image and the target tomographic image input from the amplitude calculator 22 are superimposed.
The digital image data output from the DSC 24 is
The signal is converted into an analog signal by an / A converter (digital-to-analog) converter 38 and displayed on the display unit 40.

FIG. 2 is a schematic diagram for explaining the structure of a B-mode tomographic image obtained by the present apparatus. The figure shows a fan-shaped image area obtained by sector electronic scanning. Each point in this image area has an index j (0 ≦ j ≦ M) indicating the distance (depth) from the ultrasonic probe and a line number i (0 ≦ i ≦ N) indicating the direction of electronic scanning. Is specified as a set.

Both the tomographic image of interest and the reference tomographic image superimposed according to the present invention have the image areas shown in FIG. Each pixel on each of the tomographic image of interest and the reference tomographic image is designated by an index (i, j). here,
The luminance information of the pixel specified by the set of indexes (i, j) on the tomographic image of interest is data [i] [j], and the luminance information of the pixel specified by the set of indexes (i, j) on the reference tomographic image. The luminance information is represented by a symbol data '[i] [j]. The color information of each of the target tomographic image and the reference tomographic image is also specified for each index set (i, j).

In the present apparatus, the tomographic image of interest and the reference tomographic image are superimposed by the DSC 24. Here, “overlapping both images” means displaying pixels having the same index set at the same screen point in the tomographic image of interest and the reference tomographic image. That is, the DSC 24
An overlay image is generated by adding pixel data having the same index set to the target tomographic image having the sector shape and the reference tomographic image having the same sector shape. This addition process is performed for each of the luminance information and the color information.

In general, the tomographic image output from the amplitude calculator 22 is represented by a black and white image. The reference tomographic image is also stored in the storage unit 32 as a monochrome image having only luminance information. If the target tomographic image and the reference tomographic image are superimposed and displayed on the same area as the black-and-white image initially obtained, the user may not be able to identify both images from the displayed image. Therefore, in the present apparatus, the image data processing unit 36 performs predetermined image data processing on the reference tomographic image, and distinguishes between the image derived from the tomographic image of interest and the image derived from the reference tomographic image represented in the overlay image. It is possible.

One of the image data processing processes that can be performed by the image data processing unit 36 is to change the hue. That is, a color is given to the black-and-white reference tomographic image read from the storage unit 32. Other processing includes changes in the brightness of the entire image, contour enhancement for changing the brightness of the edges of the image, and processing for binarizing the brightness based on a predetermined threshold. These processes can be selected by the user. It is also possible to select a plurality of those processes. For example, a combination of changing both the hue and the luminance, changing the hue and enhancing the contour, and changing the hue and binarizing can be selected.

Incidentally, the image required for diagnosis is the tomographic image of interest, while the reference tomographic image is used exclusively for positioning the tomographic image of interest. In other words, for the reference tomographic image, it is sufficient if the rough structure of the image is known. Therefore, it is sufficient to simplify the image by binarization processing. On the contrary, it is possible to reduce the amount of information and reduce the processing load associated therewith. There is also an advantage that it can be.

The reference tomographic image processed by the image data processing unit 36 and the target tomographic image from the amplitude calculator 22 are superimposed by the DSC 24. The reference tomographic image is a still image, and the tomographic image of interest is basically a moving image. In addition to the data processing by the image data processing unit 36 described above,
The difference regarding the presence or absence of the time change also has the effect of facilitating the discrimination between the two images.

Although the binarization process of the reference tomographic image is performed in the image data processing unit 36 here, it may be performed before storing it in the storage unit 32. In such a configuration, the binarized reference tomographic image is stored in the storage unit 32, and the capacity of the reference tomographic image in the storage unit 32 can be reduced.

Next, the calculation and use of the correlation index between the target tomographic image and the reference tomographic image in the present apparatus will be described. In this apparatus, a correlation coefficient R relating to luminance information is calculated as a correlation index. This correlation coefficient R is calculated by the following equation.

[0031]

(Equation 1) Note that the luminance information data [i] [j], data '[i] of each image
Instead of [j], the correlation coefficient R may be calculated using data obtained by binarizing them with a predetermined threshold.

Another example of the index that can be used as the correlation index is to use the exclusive OR of each pixel of the binarized tomographic image and the binarized reference tomographic image. In this method, a value obtained by integrating the exclusive OR of each pixel for the entire image can be used as a correlation index. Because, as the degree of coincidence between the two images increases, the inverted image of one image becomes complementary to the other,
This is because the integrated value of the exclusive OR in the image increases accordingly.

In addition, matching between the two images may be evaluated based on known image processing. For example, there is a method of extracting image outlines from both images and comparing the outlines to perform image matching. There is also a method of performing texture analysis on both images, extracting feature amounts of both images, and comparing them.

When the correlation index is calculated in this manner,
Based on this, the comparison determination unit 34 determines whether the two images match (or are similar within an allowable range). A threshold corresponding to the adopted correlation index is set in the comparison determination unit 34. The range of the correlation coefficient R employed here is -1 ≦ R ≦ 1, and the threshold value is set to a positive value, for example, 0.8.

When R exceeds the threshold value, the comparison / determination section 34 outputs a signal such as a pulse. DSC24
Freezes the overlay image when detecting the output pulse from the comparison / determination unit 34. That is,
Until then, the image of the tomographic image of interest, which was displayed as a moving image, is stopped in the overlay image. This means that the tomographic image of interest sequentially input from the amplitude calculator 22 is not superimposed on the reference tomographic image, but the tomographic image of interest and the reference tomographic image corresponding to the point in time when the pulse from the comparison / determination unit 34 is detected. This is realized by repeatedly displaying the composite image on the display unit 40.

When receiving the pulse from the comparison / determination unit 34, the storage unit 32 captures and records the tomographic image of interest output from the amplitude calculator 22 at the corresponding time.

The freeze function and the image capturing function reduce the load on the user for detecting the matching state between the tomographic image of interest and the reference tomographic image, and are useful for shortening the diagnosis time. While the user attempts to match the tomographic image of interest with the reference tomographic image and variously changes the direction and contact position of the probe 16 by trial and error, a target state where both screens coincide may occur. is there. However, in such a case, when the user recognizes the match, the probe 16 often has already moved from the target state to another state, and it is difficult to reproduce the state of the match. In such a case, the above functions are effective, and when a match occurs, the apparatus automatically determines the match and continuously displays the overlay image at that time on the display unit 40. Is captured in the storage unit 32 and recorded. The user can make a diagnosis based on the image maintained on the display unit 40 or the tomographic image of interest stored in the storage unit 32. As a result, the user does not need to judge the coincidence state by himself and does not have to overlook the coincidence state, so that the probe 16 can be operated quickly, the time until the coincidence state is found is reduced, and the time required for diagnosis is reduced. Will be done.

The correlation index calculated by the correlation index calculating section 30 may be displayed on the display section 40 by numerical values. In such a configuration, the user can move the probe 16 to a position or an orientation at which it increases while referring to the numerical value displayed together with the overlay image, so that the user can efficiently search for the target state. Can be. In addition, a separate unit other than the display unit 40 may be used as a display unit of the correlation index. For example, it is also possible to display with an indicator on a CRT in which the number of displays changes according to the magnitude of the correlation index. With this configuration, the user can intuitively grasp the degree of coincidence of the tomographic image of interest obtained from the current state of the probe 16.

The storage section 32 can use various data storage means such as a frame memory, a magnetic disk device, and a VTR. Further, the correlation index calculation unit 30, the comparison determination unit 34, and the image data processing unit 36 can be configured using hardware or can be configured using software.

The processing of generating the overlay image and calculating the correlation index is performed in synchronization with a control signal (not shown) from the timing signal generator 10.

[0041]

As described above, according to the present invention,
The target image and the reference image are superimposed and displayed as one overlay image, or the degree of coincidence between the target image and the reference image is indicated as an objective correlation index, so that the target image and the reference image can be compared. The effect that comparison becomes easy is obtained. Thereby, an effect is obtained in which it is easy to operate the ultrasonic probe so as to obtain an image from a cross section or a viewpoint that matches the past reference image. In addition, it is easy to accurately grasp changes over time, such as a medical condition of a diagnostic site, by comparing the cross-sections obtained in this way, or matching the viewpoints, or comparing both similar images, and a highly reliable ultrasonic diagnosis can be performed. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of an ultrasonic diagnostic apparatus according to a preferred embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a structure of a B-mode tomographic image obtained by the present apparatus.

[Explanation of symbols]

10 timing signal generator, 12 scan controller, 14
Transceiver, 16 probes, 24 DSC, 30 correlation index calculation unit, 32 storage unit, 34 comparison and determination unit, 36
Image data processing unit, 40 display unit.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4C301 CC02 EE13 JB27 JB28 JC08 KK01 KK12 LL11 5B057 AA07 BA05 CA02 CB01 CB06 CC01 CC03 CE11 CE12 CE17

Claims (12)

[Claims] 1. Reference image storage means for storing a reference image based on past echo data obtained by transmission and reception of ultrasonic waves; attention image generation means for generating a notice image based on currently obtained echo data; An ultrasonic diagnostic apparatus comprising: an overlay image generating unit configured to generate an overlay image in which the reference image and the target image are superimposed on each other so as to be identifiable; and a display unit configured to display the overlay image. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the overlay image generating means is capable of distinguishing the superimposed reference image and the target image from each other by using a hue. Ultrasonic diagnostic equipment. 3. The ultrasonic diagnostic apparatus according to claim 1, wherein the overlay image generating means is capable of distinguishing the superimposed reference image and the target image from each other by using luminance. Ultrasonic diagnostic equipment. 4. The ultrasonic diagnostic apparatus according to claim 1, further comprising an outline emphasis unit for emphasizing an outline of the reference image, wherein the overlay image generation unit converts the reference image with the outline emphasized into the image of interest. An ultrasonic diagnostic apparatus comprising: 5. The ultrasonic diagnostic apparatus according to claim 1, wherein said reference image storage means stores the binarized reference image. 6. A reference image storing means for storing a reference image based on past echo data obtained by transmission and reception of ultrasonic waves, a target image generating means for generating a target image based on currently obtained echo data, An ultrasonic diagnostic apparatus comprising: a correlation evaluation unit that calculates a correlation index between the reference image and the image of interest. 7. The ultrasonic diagnostic apparatus according to claim 6, further comprising: a binarizing unit that binarizes the reference image and the image of interest, wherein the correlation evaluation unit includes the binarized reference. Calculating the correlation index between the image and the binarized image of interest. 8. The ultrasonic diagnostic apparatus according to claim 6, further comprising: a contour extraction unit configured to extract a contour from each of the reference image and the image of interest, wherein the correlation evaluation unit compares the reference image with the image of interest. Calculating the correlation index based on the comparison between the contours extracted from the ultrasonic diagnostic apparatus. 9. The ultrasonic diagnostic apparatus according to claim 6, further comprising an index display unit for displaying the correlation index. 10. The ultrasonic diagnostic apparatus according to claim 6, wherein the correlation index is detected to exceed a predetermined threshold, and the target image is stored in a storage unit. An ultrasonic diagnostic apparatus comprising: 11. The ultrasonic diagnostic apparatus according to claim 6, wherein the target image displayed as a moving image on a display device is detected by detecting that the correlation index has exceeded a predetermined threshold value. An ultrasonic diagnostic apparatus comprising an image freezing means for freezing. 12. The ultrasonic diagnostic apparatus according to claim 1, wherein: a correlation evaluation unit that calculates a correlation index between the reference image and the image of interest; An ultrasonic diagnostic apparatus comprising: an image freeze unit that freezes the target image displayed as a moving image on a display device by detecting that the image has exceeded the target image.