JPS6246173B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasound imaging device with an image memory.

FIG. 1 is a block diagram of a conventional ultrasound imaging device using the pulse echo method, in which 11 is a target to be imaged, 12 is a wave transmitting/receiving section, 13 is a signal processing section, 1
4 is an image memory, and 15 is a display device. The wave transmitting/receiving unit 12 is a part that transmits pulsed ultrasonic waves toward the target 11 and receives the reflected waves, and the signal processing unit 13 analyzes the reflected waves and converts images of the target into two-dimensional array data. The image memory 14 stores this image data, and the display 15 displays it on a CRT screen using a method such as brightness modulation. In such an ultrasound imaging device, one frame of image reproduced by one transmission and reception causes deterioration of the signal-to-noise ratio due to the randomness of reflected waves and other disturbance factors. .

Therefore, an object of the present invention is to provide an ultrasonic imaging device with improved image quality, and its features include a wave transmitting/receiving unit that transmits pulsed ultrasonic waves to a target and receives the reflected waves; Analyze the waves and get the target image 2
a signal processing section for reproducing as dimensional array data; an image memory for storing image data; a display for displaying the contents of the image memory; and a subtracter for providing a difference between the output of the signal processing section and the output of the image memory; a digit shifter that shifts the output of the subtracter by a number of digits corresponding to a predetermined digit shift amount; an adder that inputs the sum of the output of the digit shifter and the output of the image memory to the image memory; and a digit movement amount indicator for indicating the digit movement amount. The principle of this configuration is to successively collect multiple frames of the same target image and integrate them over time to suppress noise and improve the signal-to-noise ratio. Examples will be described below with reference to the drawings.

FIG. 2 shows an embodiment of the display unit according to the present invention, and 21 is an image data input terminal, which corresponds to the output of the signal processing unit 13 in FIG. 22 is a subtracter, 23 is a digit mover whose digit shift amount is variable, 24 is a digit shift amount indicator, 25 is an adder, 26 is an image memory, and 27 is a display. This is image memory 26
A primary filter consisting of 22 to 25 is added to the input stage of . 1 input from terminal 21
The image data of the frame is subjected to subtraction, digit shift, and addition operations as shown in the figure with the image data already stored in the image memory 26, and the results are used as new image data to be stored in the image memory 26. On the other hand, the image memory 26 is always read out and displayed on the display 27. The above filter operation means that exactly the same operation is performed independently and time-divisionally on each pixel that makes up the image, but here we will use an image data matrix to explain the operation contents. do. Assuming that the image data matrix input from the terminal 21 at time n is X _o and the image data matrix Y _o that has already been stored in the image memory 26 and is being displayed, the subtracter 22 calculates X _o −Y _o and divides the digits into The mover 23 arithmetically shifts this by k bits to the lower order to obtain X _o -Y _o / ^2k . Here, the digit shift amount k is 0 or a positive integer, and can be arbitrarily indicated by the digit shift amount indicator 24. Adder 2
Step 5 calculates a new image Y _o+1 by adding Y _o to the above X _o −Y _o /2 ^k .

Y _o+1 = X _o /2 ^k + (1-1/2 ^k ) Y _o ... (1) Y _o+1 is the internal division value of X _o and _Yo , and is the digit shift amount k
determines the division ratio. Solving equation (1) and expressing Y _o+1 using the past input image sequence X _i results in the following.

Y _o+1 = 1/2 ^k {X _o + ^KX _{o- 1} +K ² X _o- 2 + ^K ₃ Since K<1, the weight of the power of K is attenuated with a time constant of 2 ^k as n progresses.
Assuming that the target is stationary and the sequentially reproduced image sequence X _{i is} weighted with random noise images N _i in addition to reproducible _images S of the target, the following equation can be obtained. The resulting image is Y _o+1 = S + 1/2 ^k {N _o + KN _o-1 + K ² N _o-2 + K ³ N _o-3 +...}... (3), and past noise is added to the image S of the target object. Image sequence N _i
The weighted average value of k is added to the latter, and the larger k is, the lower the value can be, so the signal-to-noise ratio can be increased.

The advantage of the screen integration method according to the present invention is that its configuration is extremely simple, and an adder with the same number of digits as the image data,
It can be easily configured by adding a subtracter and a digit shifter, and control is also easy because the adder and subtracter do not overflow. Second, as is clear from equation (3), an image with the same high signal-to-noise ratio is observed at any time n. Third, when the target is moving, setting the time ^constant 2 ^k to a small value allows you to see the movement of the target without disturbing the image of the target. Even if it is large enough to cause disturbance, the past image sequence of the moving target is weighted by a power of K as shown in equation (2) and displayed as a weight, so the time constant 2 ^k
An image with an afterimage that disappears at a certain point is obtained. In this way, by appropriately selecting the time constant 2 ^k depending on the moving speed of the target object, it is possible to observe an image unique to the present invention.

As described above, the present invention can improve the signal-to-noise ratio of a reproduced image screen, and is therefore effective for imaging devices using ultrasound.

[Brief explanation of the drawing]

Figure 1 shows an example of the configuration of a conventional ultrasound imaging device;
The figure shows an example of the configuration of an ultrasound imaging device according to the present invention. 11; target object, 12; wave transmitting/receiving unit, 13; signal processing unit, 14; image memory, 15; display device, 21;
Input terminal, 22; Subtractor, 23; Digit shifter, 2
4; digit movement amount indicator, 25; adder, 26; image memory, 27; display.

Claims (1)

[Claims] 1. A wave transmitting/receiving unit that transmits pulsed ultrasonic waves to the target and receives the reflected waves, a signal processing unit that analyzes the reflected waves and reproduces the image of the target as two-dimensional array data, and an image memory to be stored, a display for displaying the contents of the image memory, a subtracter for providing the difference between the output of the signal processing section and the output of the image memory, and an output of the subtracter corresponding to a predetermined digit shift amount. A digit mover that moves the digit by the number of digits, an adder that inputs the sum of the output of the digit mover and the output of the image memory to the image memory, and a digit shift amount indicator that indicates the amount of digit shift. An ultrasound imaging device comprising: