JPH03103246A - Real time shortening method for speckle noise - Google Patents

Abstract

PURPOSE:To reduce the speckle in a real time without narrowing a speckle reducing area by receiving signals with a main sound ray element group and a sub-sound ray element group whose position and opening are different, amplifying them separately, and thereafter, deriving the respective absolute values and adding them. CONSTITUTION:From an array transducer 1, (n) pieces of i-th-(i+n-1)-th element groups are selected for transmission. By setting (i)=1, the transmission element group is constituted of (n) pieces of first - n-th elements. Transmission is executed from (n) transmission element groups. Reception is executed by a main sound ray element group 2 (i-i)+(n-1) being the same as the transmission element group. Reception is executed by an (i+1)-(i+n)-th sub-sound ray element group 3, as well. In such a manner, with respect to the same transmission signal, by receiving simultaneously two reception signals whose propagation paths are different, and superposing the signals whose correlation is small, the speckle can be reduced in a real time without decreasing an image area.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a real-time method for reducing speckle noise in B-mode images of an ultrasound diagnostic apparatus.

(Prior art) Pulse-type ultrasound diagnostic equipment emits ultrasound pulses into the subject, and uses the fact that the degree of attenuation and reflection of ultrasound waves differs depending on the tissue and its lesion to detect the reflections from the subject. This is a device that analyzes and diagnoses waves.

However, a mottled pattern called speckle appears in the B-mode image obtained by this ultrasonic diagnostic apparatus, which is the main cause of image quality deterioration. The cause of speckles is that the phases of the ultrasonic pulses that enter the living body are aligned, so the reflected waves from the many scatterers that exist inside the object interfere with each other on the receiving surface of the transducer. I'll wake you up. As a result, the amplitude of the detected echo signal fluctuates, which appears as speckles on the B-mode image. The speckle pattern that appears in the image is the result of interference of reflected waves from a large number of scatterers, and does not represent the fine structure of the tissue. Therefore,
In order to display the received signal as a B-mode image, it is necessary to reduce speckle.

(Problem to be Solved by the Invention) In order to reduce the speckles mentioned above, a method is used in which multiple B-mode images with low correlation with respect to speckles are superimposed. method), or by changing the center frequency of the incident ultrasonic pulse (frequency compound method).

In the spatial compounding method, multiple signals with low correlation with respect to speckle are obtained by changing the position of the receiving element of the receiving array transducer, and after converting these signals into a B-mode image, they are added and superimposed for display. Reduces noise. In this method, the array transducer transmits and receives signals using different elements, which are then amplified. Processing such as detection and phasing addition is performed to create a B-mode image, and this process is repeated as many times as necessary (minimum 2
The problem is that it takes time to repeatedly add and display an image, making real-time processing difficult. or,
In order to obtain multiple B-mode images with low correlation, multiple images cannot be obtained from the same area, and the area where speckle noise is reduced is narrowed to the area shown by diagonal lines in Figure 5. There was also the problem of putting it away. In the figure,
1 is an array transducer, and shows the irradiation range of the beam when it is equivalently irradiated from three points A, B, and C in the figure by a plurality of elements. In this case, the area where speckle noise is reduced is only the shaded area.

The present invention has been made in view of the above points, and its purpose is to realize a real-time speckle noise reduction method that can reduce speckles in real time without narrowing the speckle reduction area. It is in.

(Means for Solving the Problems) The present invention for solving the above-mentioned problems includes the steps of using a plurality of elements of an array transducer as a transmission element group, and creating a tonic ray element which is removed from the same element as the transmission element group. a step of receiving the sound ray element group to obtain a main sound ray signal, and a step of receiving the sound ray element group by a sub-sound ray element group having an element located at a position different from the main sound ray element group or a sub-sound ray element group having a different number of elements to obtain a sub-tone ray signal. ,
a step of separately performing processing such as logarithmic compression amplification on the main sound ray signal and the sub-sound ray signal; and a step of obtaining an absolute value signal in order to eliminate phase information from the output signal from the processing step;
This method is characterized by comprising a step of adding the absolute value signals, and a step of performing signal processing and image reconstruction after transmission and reception by all elements of the array transducer are completed.

(Operation) A plurality of element groups of the array transducer are transmitted as a tonic ray element group. The echo signal is received by the main sound ray element group, and is also received by the sub sound ray element group, which has a different position or aperture from the main sound ray element group, and after being amplified separately, the absolute value of each is calculated and added. , reduce speckle noise.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing the distribution of transmitting and receiving elements of an array transducer in one embodiment of the method of the present invention. In the figure, 1 is an array transducer having N elements arranged in a row, and 2 is nf from the i-th element to the i+n-1-th element.
The tonic ray element group transmitted and received by the element f4, 3 is n from the i+ath to the i+a+n-1th
This is a reception-only subtone ray element group consisting of elements. The echo signal is transmitted from the main sound ray element group 2 and receives the echo signal from the target of the subject. At the same time, the sub sound ray element group 3 receives the same echo signal. Once this is completed, each element moves to its adjacent element and performs transmission and reception.

FIG. 2 is a block diagram of a circuit shown in FIG. 1 that processes two signals received by the array transducer 1. In the figure, parts equivalent to those in FIG. 1 are given the same reference numerals. In this figure, the tonic ray element group 2 is the 1st to n-1th element, and the sub-tone ray element group 3 is the 2nd element.
An example is shown in which the elements are composed of elements from the th to the nth.

In the figure, 11 is a logarithmic amplifier that logarithmically compresses and amplifies the signal from the tonic ray element group 2 (hereinafter referred to as the tonic ray signal);
2 is a logarithmic amplifier that logarithmically compresses and amplifies the signal from the sub-sound ray element group 3 (hereinafter referred to as sub-sound ray signal). 13
In order to remove the phase information of the main sound ray signal output from the logarithmic amplifier 11, 14 is an absolute value calculation circuit for obtaining the amplitude value, which is the absolute value thereof, and 14 is an absolute value calculation circuit for obtaining the amplitude value of the sub sound ray signal. It is an arithmetic circuit. 15 is an absolute value calculation circuit 13
．． 16 is an envelope detector that detects the output signal of adder 15 and outputs its envelope signal; 17 converts the signal detected by envelope detector 16 into a desired signal. This is a signal processing circuit that performs processing. When the data of all the elements have been collected, the image is reconstructed by the image reconstruction circuit 18.

Next, the method of this embodiment will be explained by explaining the operation of the apparatus configured as described above with reference to the flowchart of FIG.

Step 1 From array transducer 1 to i-th (1+n-1)
Select the nth group of elements for transmission.

Step 2 As i - a l, the transmission element group is set to n elements from 1st to nth elements.

Step 3 Transmission is performed from a group of n transmission elements.

(i − i ten n − 1) Step 4 Tonic ray element group 2, which is the same as the transmission element group (
i-i ten n-1). It is also received by the (i+1 to i+n)th subtone ray element group 3.

Step 5 The main sound line signal is logarithmically compressed and amplified by the logarithmic amplifier 11 to compress the wide dynamic range of the received signal to a level suitable for image display. A logarithmic amplifier 12 performs logarithmic compression amplification on the sub-sound ray signal.

Step 6 In order to erase the phase information from the logarithmically compressed main sound line signal and subline signal to eliminate the difference between the signals due to the phase difference, and to obtain only the maximum value of the amplitude, the main sound line signal is transferred to the absolute value calculation circuit 13. Absolute value calculation is performed to calculate the amplitude value, which is the absolute value. The sub-sound ray signal is subjected to absolute value calculation in an absolute value calculation circuit 14 to calculate the amplitude value.

Step 7: Add the outputs of the absolute value/ijt calculating circuit 13 and the absolute value calculating circuit 14 using the adder 15 to obtain the sum of the absolute values of the live line signal and the sub-acoustic line signal.

Step 8 The output of the adder 15 is detected by an envelope line detector l6.

Step 9 The detected signal is subjected to signal processing such as AD conversion and storage in a storage device in the signal processing circuit 17 of an ordinary ultrasonic diagnostic apparatus.

Step 10 Check whether transmission and reception have been completed for all elements of array transducer 1. If not completed, proceed to step 11. If completed, proceed to step 12.

Step 11 Add 1 to element number i, select the next element group, and return to step 3.

Step 12: When all elements have been transmitted and received, interpolation is performed to reconstruct a B-mode image.

As explained above, by simultaneously receiving two sets of received signals with different propagation paths for the same transmitted signal, signals with low correlation regarding speckle can be detected in real time.
By superimposing signals that can be obtained in the same area and have a small correlation, a B-mode image with reduced speckles can be obtained in real time without reducing the image area.

Note that the present invention is not limited to the above embodiments.

In the embodiment, the subtone ray element group 3 is selected from the elements adjacent to the main tone ray element group 2, but they may be separated by an appropriate number of elements. However, care must be taken not to narrow the speckle reduction area because of this.

Further, in the embodiment, speckle reduction is performed using two sound rays with different acoustic paths, but it may be possible to use two sound rays with different aperture sizes. In this case, the element group is selected as follows, for example.

Tonic ray element group... n elements from i+ath to i+3+n-1 subtone element group... n+2a from ith to i+2a+n-1 where, i
=1~N- (2a+n-1) This example shows a case where the number of elements of the sub-tone ray is increased by an equal number on both sides of the main tone ray, but it is not necessary that the increased numbers on the left and right sides be equal; Feel free to choose a different number.

Furthermore, it is also possible to select a plurality of subtone lines for one tonic line.

FIG. 4 is a block diagram of a device for signal processing according to yet another embodiment. In the figure, the same parts as in FIG. 2 are given the same reference numerals. In the figure, 21 is an envelope detector that performs envelope detection of the main sound ray signal output from the logarithmic amplifier 11, and 22 is an envelope detector that performs envelope detection of the secondary sound ray signal output from the logarithmic amplifier 12. In the above embodiment, the absolute value of the signal was taken to eliminate the phase information of the signal, but in this embodiment, the signal logarithmically compressed by the logarithmic amplifier 11.12 was detected by the envelope detector 21.22. This method adds signal waveforms to reduce speckle. When envelope detection is performed in this way, its absolute value is determined, and if the detection is performed before addition, an absolute value calculation circuit is not required.

(Effects of the Invention) As described above in detail, according to the present invention, speckles can be reduced in real time without narrowing the speckle reduction area, and the practical effects are great.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a transmission/reception method according to an embodiment of the method of the present invention, Fig. 2 is a diagram showing a processing circuit for a signal obtained by the method of Fig. 1, and Fig. 3 is a flowchart of the method of the present invention. , FIG. 4 is a diagram of a signal processing circuit of another embodiment, and FIG. 5 is a diagram showing a speckle reduction area by the conventional spatial conbound method. 1... Array transducer 2... Main sound ray element group 3... Sub-tone ray element group 11.12... Logarithmic amplifiers 3, 14... Absolute value calculation circuit 5... Adder 6 , 21.22...Envelope detector

Claims (1)

[Claims] A step of using a plurality of elements of an array transducer (1) as a transmitting element group, and receiving a tonic ray signal by a tonic ray element group (2) consisting of the same elements as the transmitting element group. a step of receiving the sub-sound ray signal by a sub-sound ray element group (3) having an element located at a position different from the main sound ray element group (2) or having a different number of elements, and obtaining a sub-sound ray signal; A step of separately processing logarithmic compression amplification (11, 12) on the main sound ray signal and the sub-sound ray signal, and a step of obtaining an absolute value signal in order to eliminate phase information from the output signal from the processing step ( 13, 14, 21, 22), the step of adding the absolute value signals (15), and once the transmission and reception by all elements of the array transducer (1) are completed, signal processing (17) and image reconstruction (1) are performed.
8) A real-time speckle noise reduction method characterized by comprising the steps of: