JP2824673B2 - Ultrasound diagnostic equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for real-time reduction of speckle noise in a B-mode image of an ultrasonic diagnostic apparatus.

(Prior art) A pulse-type ultrasonic diagnostic apparatus radiates an ultrasonic pulse into a subject, and utilizes the fact that the degree of attenuation and reflection of the ultrasonic wave differs depending on a tissue or a lesion thereof, and is reflected from the subject. It is a device that analyzes and diagnoses waves. However, a mottled pattern called speckle appears in the B-mode image obtained by the ultrasonic diagnostic apparatus, which is a main cause of image quality deterioration. The speckles are generated because the ultrasonic pulses incident on the living body have the same phase, and the reflected waves from a large number of scatterers inside the subject cause interference on the receiving surface of the transducer. Will wake up. As a result, the amplitude of the detected echo signal fluctuates, which appears as a mottled pattern on the B-mode image, that is, speckle.
The speckle pattern that appears in the image is a 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 a 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 above-mentioned speckle, a method of superimposing a plurality of B-mode images having a small correlation with respect to the speckle is adopted. ) Or by changing the center frequency of the incident ultrasonic pulse (frequency compound method).

In the spatial compound method, a plurality of signals having a small correlation with respect to speckles are obtained by changing the position of a receiving element of a receiving array transducer, and these signals are formed into a B-mode image, and then added and superimposed and displayed. Nozzles are reduced. in this way,
Transmission and reception by the array transducer are performed by different elements, and processing such as amplification, detection, and phasing addition is performed to produce a B-mode image. This process is repeated a required number of times (minimum two times) and added to display an image. Therefore, there is a problem that it takes time and real-time processing is difficult.
Further, in order to obtain a plurality of B-mode images having a small correlation, a plurality of images cannot be obtained from the same region, and the region in which the speckle noise is reduced corresponds to the region shown by oblique lines in FIG. There was also a problem that it narrowed. In the drawing, reference numeral 1 denotes an array transducer, which shows a beam irradiation range in a case where irradiation is performed from a plurality of elements equivalently from points A, B, and C3 in the drawing. In this case, the region in which the speckle noise is reduced is only the range of the oblique line.

The present invention has been made in view of the above points, and an object of the present invention is to provide an ultrasonic diagnostic apparatus that executes speckle reduction at high speed.

(Means for Solving the Problems) An ultrasonic diagnostic apparatus of the present invention for solving the above-mentioned problems includes a receiving unit for receiving echo signals in an ultrasonic wave from one region in a subject as a plurality of different ultrasonic beams. Amplifying means for logarithmically amplifying the plurality of received signals, calculating means for calculating absolute values of the plurality of logarithmically amplified signals, and adding means for adding a plurality of absolute values obtained by the calculation A detection unit that performs envelope detection on an output signal of the addition unit; and an image generation unit that generates an image of the subject based on the detected signal.

(Operation) A plurality of element groups of the array transducer are transmitted as main sound ray element groups. The echo signal is received by the main sound ray element group, and also the sub sound ray element group having a different position or opening from the main sound ray element group is received, amplified separately, and 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 according to one embodiment of the method of the present invention. In the figure, 1 is an array transducer having N elements in which a plurality of elements are arranged in a line, and 2 is n from the i-th element to the (i + n-1) -th element.
The main sound ray element group 3 transmitted and received by the number of elements is a reception-only sub sound ray element group composed of n elements from the (i + a) th element to the (i + a + n-1) th element. The echo signal is transmitted from the main sound ray element group 2 and received from the target of the subject. At the same time, the same echo signal is received by the sub sound ray element group 3. When this is completed, the process moves to the next element and performs transmission and reception.

FIG. 2 shows the array transducer 1 shown in FIG.
FIG. 3 is a block diagram of a circuit that processes two signals received by the control unit.
In the figure, the same parts as those in FIG. 1 are denoted by the same reference numerals. This figure shows an example in which the main sound ray element group 2 is composed of the first to n-1st elements, and the sub sound ray element group 3 is composed of the second to n-th elements. In the figure, reference numeral 11 denotes a logarithmic amplifier for logarithmically compressing and amplifying a signal from the main sound ray element group 2 (hereinafter referred to as main sound ray signal), and reference numeral 12 denotes a signal from the sub sound ray element group 3 (hereinafter referred to as sub sound ray signal). It is a logarithmic amplifier that performs logarithmic compression amplification.
13 is an absolute value calculation circuit for obtaining an amplitude value which is an absolute value of the phase information of the main sound ray signal output from the logarithmic amplifier 11, and 14 is also an absolute value calculation circuit for obtaining an amplitude value of the sub sound ray signal. It is a value calculation circuit. 15 is an adder that adds the outputs of the absolute value calculation circuits 13 and 14, 16 is an envelope detector that detects the output signal of the adder 15 and outputs its envelope signal, and 17 is an envelope detector 16. This is a signal processing circuit that performs required signal processing on the detected signal. When the data of all the elements is collected, the image is reconstructed by the image reconstruction circuit 18.

Next, the operation of the apparatus configured as described above will be described with reference to the flowchart of FIG. 3 to explain the method of the present embodiment.

Step 1 i-th to (i + n-)
1) The n-th element group is selected for transmission.

Step 2 Assuming that i = 1, the transmission element group is set to the first to n-th n elements.

Step 3 Transmission is performed from n transmission element groups.

(I to i + n-1) Step 4 Same main sound ray element group 2 as the transmission element group
(I to i + n-1). The (i + 1-i + n) -th sub sound ray element group 3 is also received.

Step 5 The main sound ray signal is logarithmically compressed and amplified by the logarithmic amplifier 11 to compress a wide dynamic range of the received signal to a level suitable for image display. The auxiliary sound ray signal is logarithmically compressed and amplified by the logarithmic amplifier 12.

Step 6 In order to eliminate the phase information from the logarithmically compressed main sound ray signal and sub sound ray signal to eliminate the difference between the signals due to the phase difference and obtain only the maximum value of the amplitude, the main sound ray signal is subjected to an absolute value calculation circuit 13. , An absolute value calculation is performed to calculate an amplitude value which is an absolute value. The absolute value calculation circuit 14 performs an absolute value calculation on the auxiliary sound ray signal to calculate an amplitude value.

Step 7 The outputs of the absolute value calculation circuit 13 and the absolute value calculation circuit 14 are added by the adder 15 to obtain the sum of the absolute values of the main sound ray signal and the sub sound ray signal.

Step 8 The output of the adder 15 is detected by the envelope detector 16.

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

Step 10 It is checked whether transmission / reception has been completed for all elements of the array transducer 1. If not, go to step 11. If so, go to step 12.

Step 11 One is added to the element number i, the next element group is selected, and the process returns to step 3.

Step 12 Interpolation is performed when all elements have been transmitted and received.
Reconstruct a mode image.

As described above, for the same transmission signal, 2
By simultaneously receiving received signals having different sets of propagation paths, a signal having a small correlation with respect to speckles can be obtained in the same region in real time. A B-mode image with reduced speckles can be obtained without reducing the area.

 The present invention is not limited to the above embodiment.

In the embodiment, the sub sound ray element group 3 is selected from the elements adjacent to the main sound ray element group 2, but may be separated by an appropriate number. However, care must be taken not to narrow the speckle reduction region because of that.

Further, in the embodiment, speckle reduction is performed by using two sound rays whose acoustic paths are changed. However, two sound rays whose opening size is changed may be used. In this case, the element group is selected as follows, for example.

Primary sound ray element group ... i + a-th to i + a + n-1 n-th auxiliary sound ray element group ... i-th to i + 2a + n-1-th n + 2a where i = 1 to N- (2a + n-1) In the embodiment, the case where the number of elements of the auxiliary sound ray is increased by the same number on both sides of the main sound ray has been described. However, it is not necessary to make the left and right increase numbers equal, and a different number may be selected.

Further, it is also possible to select a plurality of sub sound rays for one main sound ray.

(Effects of the Invention) As described in detail above, according to the present invention, speckle reduction can be performed at high speed.

[Brief description of the 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 circuit for processing 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 showing a speckle reduction region by the conventional spatial compound method. 1 Array transducer 2 Primary sound ray element group 3 Secondary sound ray element group 11,12 Logarithmic amplifier 13,14 Absolute value calculation circuit 15 Adder 16,21,22 Envelope detector 17: Signal processing circuit, 18: Image reconstruction circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) A61B 8/14 G01N 29 / 06,29 / 22

Claims (1)

(57) [Claims] A receiving means for receiving echo signals from an area of the subject as a plurality of ultrasonic beams; an amplifying means for logarithmically amplifying the received signals; and a logarithmically amplified signal. Calculating means for calculating absolute values of the plurality of signals, adding means for adding the plurality of absolute values obtained by the calculation, detecting means for performing envelope detection on an output signal of the adding means, And an image generating means for generating an image of the subject based on the received signal.