JPH0385151A - Noise suppressor for ultrasonic diagnosis apparatus - Google Patents

Abstract

PURPOSE:To decrease noise without deteriorating an image of an tissue with movement by providing an arithmetic unit outputting an image data to be displayed by averaging a new image data and an image data of the preceding frame based on a correction factor calculated by a correction factor-calculating part. CONSTITUTION:A correction factor-calculating part 2 calculates a correction factor corresponding to a difference between an image data of the preceding frame recorded in an image recording part 1 and an input image data. As an arithmetic unit 3 outputs an image data to be displayed by averaging a new image data and an image data of the preceding frame, in a part where the difference between the image data is large, the amt. of correction from the preceding frame in the calculation of the correction factor and averaging is made small and in a part where the difference is small, the amt. of correction from the preceding frame can be made large. Therefore, it is possible to reduce noise without deteriorating an image of a tissue with movement.

Description

Detailed Description of the Invention (Summary) A noise reduction device for an ultrasound diagnostic apparatus that reduces noise in image data by averaging new image data and image data of a previous frame using a predetermined correction coefficient, The aim is to reduce noise without degrading images of moving tissues.The noise reduction device has an image recording section that records the image data of the previous frame, and an image recording section that records the image data of this image recording section and the input image. A correction coefficient calculation unit that calculates a correction coefficient according to the difference between the data and the image to be displayed by averaging the new image data and the image data of the previous frame based on the correction coefficient calculated by the correction coefficient calculation unit. The device is configured to include an arithmetic unit that outputs data.

[Industrial application field]

The present invention relates to a noise reduction device for an ultrasonic diagnostic apparatus, and particularly to an ultrasonic diagnostic apparatus that reduces noise in image data by averaging new image data and image data of a previous frame using a predetermined correction coefficient. The present invention relates to a noise reduction device.

An ultrasonic diagnostic apparatus emits ultrasonic waves from a probe to a living body, detects the reflected ultrasound waves due to discontinuities in the acoustic impedance of the living tissue, and displays a cross-sectional image of the living tissue. When such devices detect reflected ultrasonic waves, process their intensity, etc., and convert them into image signals as luminance signals, they pick up various noises that appear in the displayed image. A noise reduction device is used to reduce such noise.

(Conventional technology) Conventionally, such a noise reduction device for an ultrasonic diagnostic device is
The previously displayed image data and new image data are added together according to a predetermined correction coefficient to reduce randomly generated noise.

FIG. 4 shows such a noise reduction device.

In the figure, 11 is the digital image data of the previous frame;
That is, an image memory 12 that stores luminance information of each pixel;
is the calculation section, which processes new digital image data that is input,
That is, the image data of the previous frame is read out from the image memory in synchronization with the luminance information, and new image data is generated based on a predetermined correction constant k using two multipliers 13 and 14 and one adder 15. When the image data of the previous frame is a and b, the display data C is output as c== (1-k) ·a+ as -b-■.

According to such a noise reduction device, as shown in FIG. 5, the image data of the previous frame includes image data of several previous frames as a correction component whose magnitude has been attenuated.

Therefore, according to such a noise reduction device, randomly generated noise is reduced by being combined with the image data of the previous frame in which no noise has occurred, and the image to be observed is substantially unchanged. It is possible to obtain clear images.

(Problems to be Solved by the Invention) By the way, examples of biological tissue observed with an ultrasonic diagnostic apparatus include a moving tissue such as a heart valve. When trying to obtain images of moving tissue in this way,
When using a conventional noise reduction device, the displayed image contains previous image data as a correction component in addition to the current image data, so its outline etc. are not clearly displayed and the image is distorted. The problem is that it deteriorates.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a noise reduction device for an ultrasonic diagnostic apparatus that can reduce noise without deteriorating an image of a moving tissue.

[Means to solve the problem]

In the present invention, means for solving the above problems are as follows:
A noise reduction device for an ultrasound diagnostic apparatus that reduces noise in image data by averaging new image data and image data of the previous frame using a predetermined correction coefficient, and records the image data of the previous frame. Image recording section l
and a correction coefficient calculation unit 2 that calculates a correction coefficient according to the difference between the image data of the image recording unit 1 and the input image data, and a correction coefficient calculation unit 2 that calculates a correction coefficient according to the difference between the image data of the image recording unit 1 and the input image data. The present invention includes a calculation unit 3 that averages the image data and the image data of the previous frame and outputs the image data to be displayed.

(Operation) Generally, it can be said that where the difference between the new image data and the image data of the previous frame is large, there is a large amount of movement, and where the difference is small, there is little movement.

And since the noise level is generally small,
According to the present invention, the correction coefficient calculation unit 2
1 calculates a correction coefficient according to the difference between the image data of the previous frame recorded and the input image data, and
Since the new image data and the image data of the previous frame are averaged based on the correction coefficient calculated by the correction coefficient calculation unit 2 and the image data to be displayed is output, the correction coefficient and the averaging operation are Where there is a large difference in image data, the amount of correction from the previous frame is reduced, and when the difference is small, the amount of correction from the previous frame can be increased, eliminating noise without deteriorating images of moving tissues. can be reduced.

(Example) Embodiments according to the present invention will be described below based on the drawings.

FIG. 2 shows a first embodiment of a noise reduction device for an ultrasonic diagnostic apparatus according to the present invention. In this example,
The noise reduction device is installed at the stage immediately before the data of reflected waves of ultrasonic waves from the ultrasonic diagnostic device is processed and displayed on the CRT image, and the noise reduction is performed on pixels corresponding to the pixels of the CRT. There is. In this embodiment, the noise reduction device includes an image memory 21 as an image recording unit that stores image data of one frame before, that is, brightness data of each pixel, and the brightness data of each pixel of newly input data and the above. It consists of a correction coefficient calculation section 22 that calculates a correction coefficient by comparing the luminance data of the image memory, and a calculation section 23 that outputs image data to be displayed based on the output of the correction coefficient calculation section 22.

In this embodiment, the correction coefficient calculating unit 22 calculates the correction coefficient K as follows, where A is new image data and B is image data 17 frames ago. Kku1
).

Calculated as Here, X is a predetermined arbitrary constant and is selected depending on the characteristics of the image to be displayed.

In this embodiment, the calculation unit 23 includes two multipliers 24.
25 and one adder 26 are provided, and image data C is calculated by C=(1-K)·A+K-B...■ and output. These processes are performed for each pixel forming the image under the control of a control section (not shown).

Therefore, according to this embodiment, as the difference between A and B increases, as shown in equation (2), that is, as the movement of the image increases, the value of K decreases, and the weight of the new data (
1-K) increases, making it possible to obtain image data that is faithful to the actual movement, and as the difference between A and B becomes smaller, that is, when the image movement is small, the correction coefficient also increases. (However, K<1), noise can be effectively reduced.

Therefore, according to this embodiment, parts of the image with large movements can be corrected faithfully to the current image data, and parts of the image with small movements can be corrected using the image data of one frame before.
This effectively reduces noise, and in diagnosing a living body that includes a moving part, it is possible to reduce noise without deteriorating an image of a moving tissue.

FIG. 3 shows a second embodiment of the invention. In this embodiment, the noise reduction device is provided with an image memory 31 similar to that of the first embodiment, and an arithmetic ROM 32 that serves both as a coefficient calculation section and an arithmetic section. This operation R-O
M uses the image data A and B described above as addresses, and
A value C calculated in advance based on the formula and formula (2) is stored on a table, and the data stored using inputs A and B as address signals is output as display image data C.

According to this embodiment, a device similar to the noise reduction device described in the first embodiment can be realized with a simple configuration.

Incidentally, in each of the above embodiments, the calculation of the coefficient was based on the formula (■) and the calculation of the display data was based on the formula (2). However, the present invention is not limited to this, and other formulas, such as the formula (■) and the formula (■) are used. A similar effect can be obtained if the equations corresponding to the equations are combined to have a tendency to reduce the correction when the change in the signal is large and to increase the correction when the change in the signal is small.

Furthermore, in each of the above embodiments, the noise reduction device was described as processing image data to be displayed on a CRT.
This noise reduction device can also process the ultrasonic reflection scanning signal as it is before processing it into a signal to be displayed on a CRT, and the above embodiment can be applied as is.

(Effects of the Invention) As explained above, the noise reduction device of the ultrasonic diagnostic apparatus is used to detect the difference between the image recording section that records the image data of the previous frame and the image data of this image recording section and the input image data. a correction coefficient calculation unit that calculates a corresponding correction coefficient; and a calculation that averages the new image data and the image data of the previous frame based on the correction coefficient calculated by the correction coefficient calculation unit and outputs image data to be displayed. Since parts of the image with large movements are corrected faithfully to the current image data, and parts of the image with small movements are corrected using the image data of one frame before, noise can be effectively reduced. In diagnosing a living body that includes a moving part, noise can be reduced without deteriorating an image of a moving tissue.

[Brief explanation of drawings]

Fig. 1 is a principle diagram of the present invention, Fig. 2 is a block diagram showing a first embodiment of a noise reduction device for an ultrasonic diagnostic apparatus according to the present invention, and Fig. 3 is a block diagram showing a first embodiment of a noise reduction device for an ultrasonic diagnostic apparatus according to the present invention. A block diagram showing a second embodiment of the noise reduction device, FIG. 4 is a block diagram showing a conventional noise reduction device for a sonic diagnostic device, and FIG. 5 is a block diagram showing a noise reduction device for the sonic diagnostic device shown in FIG. 4. It is a figure showing the contents of correction. 1...Image recording section 2...Correction coefficient calculation section 3...Calculating section 3 Figure II Techniques 11 seconds later, it is difficult Figure 4 Figure 5

Claims (1)

[Scope of Claims] A noise reduction device for an ultrasound diagnostic apparatus that reduces noise in image data by averaging new image data and image data of a previous frame using a predetermined correction coefficient, the noise reduction device comprising: an image recording unit (1) that records image data of the image recording unit (1); a correction coefficient calculation unit (2) that calculates a correction coefficient according to the difference between the image data of the image recording unit (1) and the input image data; The calculation unit (3) averages the new image data and the image data of the previous frame based on the correction coefficient calculated by the correction coefficient calculation unit (2) and outputs the image data to be displayed. Features: Noise reduction device for ultrasound diagnostic equipment.