JPH06105850A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

PURPOSE:To keep always an optimum contrast by setting automatically the contrast of an ultrasonic tomographic image. CONSTITUTION:A histogram wherein the number of picture elements on each brightness value is made into a graph on an ultrasonic image is prepd. in histogram circuit 28. A width value retrieving circuit 44 obtains a specified width value at a const. height or the prepd. histogram. A circuit 62 for judging rate of increase in width compares the obtd. width value with a specified standard value alpha and the differential increment is output. The circuit 62 for judging rate of increase in width determines the rate of increase in width of contrast based on the obtd. differential increment. The contrast is automatically adjusted thereby in a contrast circuit.

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 that automatically adjusts contrast by utilizing the characteristics of ultrasonic images.

[0002]

2. Description of the Related Art An ultrasonic diagnostic apparatus transmits an ultrasonic wave into a living body, receives an echo from the inside of the body, and displays a tomographic image or the like based on the received signal.

Although ultrasonic waves are transmitted and received by an ultrasonic probe, the received signal output from the ultrasonic probe is extremely weak and therefore converted into an image signal through some amplifiers. . Therefore, the amplification degree adjustment and the contrast adjustment of the received signal are important processes for determining the quality of the ultrasonic image.

FIG. 4 shows a partial configuration of a conventional ultrasonic diagnostic apparatus. FIG. 4 shows an amplifier circuit for a received signal. In FIG. 4, the received signal from the ultrasonic probe 10 is first input to the gain circuit 12. The gain circuit 12 uniformly amplifies the received signal regardless of the depth, and is adjusted by the gain signal 100 created by manual dial setting, for example. Note that Japanese Patent Application No. 4-50503, which was previously filed, discloses a configuration in which a gain signal is automatically created by utilizing a property peculiar to an ultrasonic image.

Now, the received signal from the gain circuit 12 is
STC (Sensitivity Time Controller)
ol) is input to the circuit 14. This STC circuit 14 is
The received signal is amplified with an individual amplification degree for each depth of the ultrasonic beam in the depth direction. Therefore, the STC signal 102 is given for each depth, and the amplification degree is increased or decreased in units of depth depending on the level of each STC signal 102.

The received signal is logarithmically amplified by a logarithmic amplifier 16 for mainly amplifying a weak signal, and the received signal is input to a contrast circuit 18. The contrast circuit 18 serves to make the slope of the peak of the histogram steep or moderate when the histogram of one image is taken. That is, when the shape of the histogram is made steep, the brightness of each pixel concentrates on a constant brightness, resulting in a blurred image with uniform brightness. Conversely, when the shape of the histogram is made flat, the brightness of each pixel is Since it is dispersed, the image has a remarkable difference in shade. In the conventional ultrasonic diagnostic apparatus, the level of the contrast signal 104 was adjusted by manual dial adjustment.

[0007]

Therefore, in order to obtain the optimum contrast, the operator must operate the dial or the like by trial and error, which is complicated and requires skill. there were. In particular, the sharpness of an ultrasonic image affects the accuracy of disease diagnosis, and there has been a demand for an apparatus that can always automatically set an optimum contrast.

The present invention has been made in view of the above conventional problems, and an object thereof is to provide an ultrasonic diagnostic apparatus capable of automatically performing contrast adjustment.

[0009]

In order to achieve the above object, the present invention scans an ultrasonic beam to form a scanning surface, and makes the size of captured echo data correspond to a luminance level. In an ultrasonic diagnostic apparatus that displays an ultrasonic image, a histogram creation circuit that creates a histogram that graphs the number of pixels for each brightness value for the ultrasonic image, and a predetermined width value at a fixed height of the created histogram. A width value calculation circuit that determines the contrast amplification degree, a contrast amplification degree determination circuit that determines the contrast amplification degree by comparing the width value with a predetermined reference value, and the contrast adjustment of the received signal is performed according to the determined contrast amplification degree. And a contrast circuit.

[0010]

First, the principle of the present invention will be described. FIG. 2 shows a histogram 100 of a general ultrasonic image. This histogram is a graph of the number of pixels of each luminance value (grayscale value).

As shown in the figure, when the contrast is increased, the peaks of the histogram become flat and the density becomes clear. On the contrary, when the contrast is decreased, the peak becomes high and sharp and the image becomes blurred.

It has been confirmed by experiments that histograms are created for various ultrasonic tomographic images and the shapes thereof have a Gaussian distribution.

Therefore, in the present invention, the contrast is automatically adjusted by utilizing the characteristic peculiar to the ultrasonic image.

Specifically, as shown in FIG. 3, in the present invention, the width value W is used as the index value of the spread of the histogram. Here, the width value W is 1 of the so-called half-value width D.
/ 2. Of course, the full width at half maximum D itself can be used as an index value for the spread, but if a large number of ultrasonic image histograms are analyzed on the left side (low brightness side) of the histogram peaks, small peaks will be superimposed. If
Since a small number can be seen, the width value W on the high luminance side is used to improve the determination accuracy. The overlapping of the small mountains appears in, for example, an ultrasonic image of a fetus in amniotic fluid.

Then, when the optimum contrast width value α (for example, α = 35 in the brightness value range 0 to 255) is compared with the actual width value W, the contrast is changed to some extent from the difference amount between the two. The amount of contrast adjustment indicating whether or not to perform is obtained.

Therefore, according to the above configuration, the histogram creating circuit creates the histogram, and the width value calculating circuit calculates the index value indicating the spread of the histogram such as the width value W. Then, the contrast amplification degree determination circuit compares the width value with a reference value to calculate the contrast amplification degree. Thus, the contrast circuit automatically executes the contrast adjustment.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below.

FIG. 1 shows the configuration of the essential parts of an ultrasonic diagnostic apparatus according to the present invention.

In FIG. 1, the A / D converter 20 is shown in FIG.
This is equivalent to the conventional A / D converter 20 shown in FIG. 1, and the signal 106 output from the contrast circuit 18 is input, converted into a digital signal 108, and then written into the frame memory 22. The signal 108 is also output to an image memory (not shown) and is output to the display device via the image memory.

Here, echo data of one ultrasonic tomographic image is written in the frame memory 22. Then, each echo data read from the frame memory 22 is output to the address terminal of the histogram RAM 30 provided in the histogram forming circuit 28 via the selector 24.

The histogram 100 shown in FIG. 2 is created in the histogram RAM 30. Specifically, the echo data read from the frame memory 22 is stored in the address terminal of the histogram RAM 30. When input, the frequency data in the cell designated by the address is read out, and the increment circuit 32
After 1 is added at 1, the data is written again in the cell of the same address via the latch circuit 34. That is, a histogram is created in the histogram RAM 30 by counting up each frequency data.

After the histogram is created as described above, the histogram read counter 26 is activated, and at the same time, the selector 24 causes the histogram read counter 2 to operate.
Select 6 side. The histogram read counter 26
Addresses are sequentially generated from 0, and the addresses are input to the address terminal of the histogram RAM 30 via the selector 24. As a result, the histogram RAM 30
From, the frequency data of each luminance (density value) is sequentially read. The read frequency data is output to the width value search circuit 44 via the histogram smoothing circuit 36.

The histogram smoothing circuit 36 is, for example, 7
The shift register 38 includes a number of register elements, an adder 40 that adds outputs from the register elements, and a latch circuit 42. That is, the created histogram may include a noise component, and a predetermined number of frequency data are arranged in parallel in the shift register 38 in order to smooth the noise component and perform an accurate width value search. It has been added. It should be noted that when taking the average value after addition, it is necessary to divide by the above-mentioned predetermined number, but since the added value and the value divided by the predetermined number are physically the same content, to speed up the calculation. No division is done.

In the width value search circuit 44, the frequency data held in the latch circuit 42 is input to one input terminal of the comparator 46, and the other input terminal of the comparator 46 is latched in the latch circuit 48. The frequency data having the largest value up to the previous time is input. Then, the comparator 46 outputs the latch signal 300 if the current frequency data output from the latch circuit 42 is larger. As a result, the maximum frequency data held in the latch circuit 48 is updated.

On the other hand, the output of the latch circuit 48 is an arithmetic unit 49.
Is output to the one input terminal of the comparator 56. The frequency data output from the histogram forming circuit 28 is input to the other input terminal of the comparator 56, and when the frequency data output from the histogram forming circuit 28 is larger than the halved frequency, the latch signal 301
Is output.

On the other hand, the address signal 201 output from the histogram read counter 26 is output to the latch circuit 52 and the latch circuit 58, the latch signal 300 is input to the latch circuit 52, and the latch signal is input to the latch circuit 58. 301 has been entered.

Therefore, with the above configuration, the frequency data are sequentially compared by the comparator 46 and the comparator 56, so that finally the latch circuit 52 holds the luminance value (address) having a peak in the histogram. On the other hand, the latch circuit 58 holds the luminance value (address) at a time point 1/2 from the peak on the high luminance side of the histogram. That is, the luminance value A shown in FIG. 3 is held in the latch circuit 52, and the luminance value B is held in the latch circuit 58. Then, the subtractor 60 obtains the difference between the brightness value A and the brightness value B, and the difference data is output to the amplification degree determination circuit 62.

In the amplification degree judging circuit 62, the subtracter 64 subtracts the reference value α from the difference data. That is,
An index value indicating how much the histogram formed by the histogram RAM 30 deviates from the optimum histogram is obtained. The subtracted value output from the subtractor 64 is multiplied by a predetermined weight β in the multiplier 66 and output to the adder 68. In the adder 68, the contrast adjustment amount data in which the weight β is multiplied is added to the previous contrast amplification degree data held in the latch circuit 70. That is, the weight β (β ≦
By multiplying by 1), it becomes possible to gradually bring the contrast closer to the ideal one.

Then, the contrast amplification degree signal output from the amplification degree judgment circuit 62 is converted into an analog signal by the D / A converter 72 and supplied as the contrast signal 104 to the contrast circuit 18 shown in FIG.

As a result, the contrast circuit 18 adjusts the contrast as shown in FIG. Therefore, according to the ultrasonic diagnostic apparatus of the present embodiment, it is possible to automatically perform the optimum contrast adjustment, and it is possible to always display the ultrasonic image with the optimum contrast.

In this embodiment, one histogram is created for the entire ultrasonic image, but ultrasonic image data of a specific area may be extracted and a histogram may be created for that.

[0032]

As described above, according to the present invention,
It becomes possible to automatically set the optimum contrast by automating the contrast adjustment which has been complicated in the past.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main configuration of an ultrasonic diagnostic apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing contrast adjustment and histogram change.

FIG. 3 is an explanatory diagram showing a width value W.

FIG. 4 is a block diagram showing a configuration of a conventional amplifier circuit.

[Explanation of symbols]

 22 frame memory 28 histogram making circuit 36 histogram smoothing circuit 44 width value search circuit 62 amplification degree judging circuit

Claims (1)

[Claims] 1. An ultrasonic diagnostic apparatus for displaying an ultrasonic image by scanning an ultrasonic beam to form a scanning surface, and making the size of captured echo data correspond to a brightness level. A histogram creation circuit for creating a histogram in which the number of pixels for each brightness value is graphed, a width value calculation circuit for finding a predetermined width value at a constant height of the created histogram, the width value and a predetermined reference value An ultrasonic diagnostic apparatus comprising: a contrast amplification degree determination circuit that determines the contrast amplification degree by comparing with the above; and a contrast circuit that adjusts the contrast of the received signal according to the determined contrast amplification degree.