JPH06105841A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

PURPOSE:To eliminate accumulation of a detecting error generated by successive addition of the phase difference of an echo signal received in each element and to make it possible to detect the phase aberration without decrease in accuracy by providing a constitution wherein the phase difference between a const. reference signal is detected by a phase difference detecting circuit and a discontinuous point is added by means of an adder. CONSTITUTION:A phase difference between an echo signal treated by a delay treatment and a reference signal S is detected by means of a phase difference detecting circuit 11 and is converted to a digital signal. During this output, the phase difference detecting result between output signals each other from adjoining elements is compared by means of a comparator 12. If there exists a discontinuous point, in accordance with the condition, '1' and '-1' are output to an offset formation circuit 13 and an up-down-counter 14 operates addition and subtraction to data kept in accordance with the input. In addition, at 360 deg., 360 deg. is multiplied to the counted value and the output of the offset formation circuit 13 is added to each output of the phase difference detecting circuit 11 by means of an adder 16 and is output as a corrected data.

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,
More specifically, it relates to an ultrasonic diagnostic apparatus having means for correcting the phase aberration of an ultrasonic echo signal.

[0002]

2. Description of the Related Art An ultrasonic diagnostic apparatus irradiates an ultrasonic signal from an ultrasonic probe into a subject and receives the signal reflected from a tissue or a lesion in the subject with the ultrasonic probe. It is a device for displaying a tomographic image formed by the reflected signal on the CRT and using it for diagnosis. By the way, in the process in which the ultrasonic signal propagates in the subject, is reflected by the reflector, is propagated again in the body, and is received by the ultrasonic probe, each tissue in the body, which is a medium for propagation, is not homogeneous. Therefore, a phase difference is generated between the sound waves at the stage of reaching the ultrasonic probe, and a phenomenon called a phase cancellation effect occurs in which an image due to the received ultrasonic waves is distorted. Due to this effect, the delay distribution of the reflected wave in the opening surface of the ultrasonic probe does not follow the theory. Therefore, even if the aperture is increased to improve the resolution and improve the image quality, the resolution is not improved.

In order to solve this problem, there is a method of performing phase conjugate transmission / reception. Phase conjugate transmission / reception is generally based on the phase distribution of the incident wavefront on the receiving aperture surface.
It refers to transmission and reception that performs phasing addition processing so that the directivity is automatically oriented in the direction of arrival of the incident wave.Here, the property is that the phase distribution of the incident wave front on the receiving aperture surface is It is used to correctly focus on the target wave source (echo source) even when the sound is distorted due to the sound velocity distribution in the path. That is, 2 out of the received signals given by the receiving array
Select one of the received signals, find the phase difference between the channels,
The non-ideal component contained therein is determined to determine the phase correction amount, and the phase of the received signal is corrected by the phase correction amount.
This method is called PAC (Phase Aberration Correction).

Conventionally, in the phase aberration correction, in the phased array type ultrasonic diagnostic apparatus, the phase difference (or time difference) between two elements adjacent to each other on the aperture of the ultrasonic probe is converted into a digital signal after converting the echo signal into a digital signal. The cross-correlation or the complex cross-correlation is used to obtain it, and the phase aberration occurring on the aperture is obtained and corrected by integrating it over the entire aperture.

A conventional method for detecting this phase aberration is shown in FIG.
Will be described. In the figure, 1 is a reflection point at which the ultrasonic wave emitted from the ultrasonic probe 2 is reflected. The reflected ultrasonic wave is incident on the ultrasonic probe 2 with a wavefront such as the wavefront 3 having no aberration shown by the broken line.

This echo signal is received by each element # 0, # 1, ..., # N-1, #N of the ultrasonic probe 2, and the output signal from each element is sent to the corresponding delay line 5. Each element is corrected so that the spherical wavefront becomes a flat wavefront, and the data having the same phase as the phase plane 6 of the data with the wavefront having no aberration is obtained.

[0007]

However, in reality, as described above, due to the nonuniformity of the propagating medium, the echo signal returns with a distorted wavefront as shown by the wavefront 4 having aberrations, and the ultrasonic probe is used. Since the light is incident on the tentacle 2, the output data of the delay line 5 becomes the output data 7 indicated by the waveform of the element of each delay line 5, and the wavefront formed by all the output data 7 is the real wavefront indicated by the chain line. The phase plane 8 of the data is shown in FIG.

The output data 7 is subjected to cross-correlation calculation in the correlator 9 as follows.

# 0 and # 1 of the output data 7 correspond to # of the correlator 9.
0 is input to perform cross-correlation calculation and phase difference data Δ
φ ₀₁ is output.

# 1 and # 2 of the output data 7 are # of the correlator 9.
1 is input to perform cross-correlation calculation, and the phase difference Δφ ₁₂ is obtained.

Similarly, Δφ ₂₃ , Δφ ₃₄ , ... Δφ
_N-2 , _N-1 , and Δφ _{N-1, N} are output. These phase difference data are based on the phase difference generated between the adjacent elements. Table 1 shows the phase aberration with reference to the element # 0.

[0012]

[Table 1]

In Table 1, each phase difference data has a detection error. Therefore, with respect to the phase aberration obtained by this method, the detection error is accumulated as the number of integration increases, and the accuracy of the calculation of the phase aberration decreases.

The present invention has been made in view of the above points, and an object thereof is to eliminate the accumulation of detection errors caused by successively adding the phase differences of the echo signals received by the respective elements, thereby lowering the accuracy. It is to realize an ultrasonic diagnostic apparatus capable of detecting phase aberration that does not occur.

[0015]

SUMMARY OF THE INVENTION The present invention for solving the above-mentioned problems is to provide an ultrasonic diagnostic apparatus for correcting the phase aberration of a received signal from each element of the ultrasonic probe using a constant signal as a reference signal. A phase difference detection circuit that detects a phase difference between signals and a phase difference signal from each adjacent circuit of the phase difference detection circuit are compared, a discontinuity point is detected, and -1, -1 depending on the discontinuity state. Of the data output from the comparator, an up / down counter that adjusts the held data according to the output data of each element from the comparator, and 360 ° to the output data of the up / down counter. 360 ° to multiply
An addition including an offset generation circuit configured by a multiplier, output data of the phase difference detection circuit, and output data of the offset generation circuit corresponding thereto, and the same number of configuration circuits as the comparator that outputs the added data. And a container.

[0016]

The phase difference between the echo signal received by each element of the ultrasonic probe and the constant reference signal is detected by the phase difference detection circuit. The comparator compares the phase difference outputs of the adjacent phase difference detecting circuits and, if there is a discontinuity point, outputs the data of 1 or -1 according to the state. In the offset generation circuit, the up / down counter adjusts the held data according to the input, and the 360 ° multiplier gives 360 °.
Multiplies by. The output is added to the output of the phase difference detection circuit by an adder and output as correction data having no discontinuous state.

[0017]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention. In the figure, the same parts as those in FIG. 5 are designated by the same reference numerals. In the figure, reference numeral 11 denotes a phase difference detection circuit for detecting the phase difference between the echo signal delayed by the delay line 5 and the reference signal S and converting it into a digital signal, and N + 1 elements of the ultrasonic probe 2 are provided. Is composed of N + 1 circuits corresponding to. Reference numeral 12 is a comparator for comparing the phase difference detection results of the output signals from the adjacent elements among the outputs of the respective constituent circuits of the phase difference detection circuit 11. When the difference obtained by comparing the phase difference detection results is D, when D <−180 °, “1” is
When -180 ° <D <180 °, set “0” to D> 180 °
In this case, "-1" is output to the offset generation circuit 13 (however, when the phase difference detection range is -180 ° to 180 °, in this case, when D <-180 ° and D> 180 °, the data is Discontinuity). The offset generation circuit 13 is composed of an up / down counter 14 and a 360 ° multiplier 15, and the up / down counter 14 counts up by 1 when the input from the comparator 12 is "1". When the input from the comparator 12 is "-1", it counts down by one. When the input is 0, the current value is retained.
The output of the up / down counter 14 is multiplied by 360 ° in a 360 ° multiplier 15 and output.

Reference numeral 16 denotes the output of the offset generation circuit 13 as outputs of the phase difference detection circuit 11 Δφ ₁ , Δφ ₂ , ..., Δ.
φ _k, ..., an adder of N to be added to the [Delta] [phi _N. The output is Δφ ₁ ′, Δφ ₂ ′, ..., Δφ _k ′,
..., [Delta] [phi _N is represented by a 'becomes, [Delta] [phi _n marked with dashes against [Delta] [phi _n input signals'. With respect to the signal of # 0, Δφ ₀ is output as it is.

Next, the operation of the apparatus of the embodiment constructed as described above will be explained.

Prior to the explanation of the operation, the principle of the operation which the apparatus of this embodiment is going to perform will be explained with reference to FIG. In the figure, (a) shows the element number of the ultrasonic probe on the horizontal axis,
A phase difference detection circuit 1 in which the phase difference from the reference signal S is plotted on the vertical axis and the phase difference between the signal of each element and the reference signal S is plotted.
2 is a graph of output data of No. 1; Phase difference detection circuit 11
Is -180 ° to 180 ° or 1 in the detection of the phase difference.
The phase difference can be detected only within the range of 0 ° to 360 °. In this embodiment, data is taken in the range of -180 ° to 180 °.

In the figure (b), the phase difference data is -180 ° to 1
It is a graph in which what was made into the data in the range of 80 ° is converted into the original phase difference data. In the figure (a), there is a discontinuity point from the positive value to the negative value between the # 3 element and the # 4 element, and the (b) figure shows the data of the # 4 element (-135 °).
It is a graph that is plotted by adding 360 ° to 225 °. Similarly, 360 ° is added at the discontinuity point from positive to negative and 360 ° is subtracted at the discontinuity point from negative to positive to make the discontinuity curve a continuous curve. In the present embodiment, the offset calculation is performed because the phase difference between adjacent elements is obtained by the conventional method, so the value of the phase difference does not become a large value, but the reference signal does not change in the present embodiment. Therefore, the phase difference sometimes exceeds the detection range.

Next, the operation of the apparatus of the embodiment constructed as described above will be explained with reference to the flow chart of FIG.

The echo signal reflected and returned from the reflection point is converted into an electric signal by each element (# 0 to #N) of the ultrasonic probe 2, and the wavefront of the reception signal of each element is converted in the delay line 5. It is delayed so that it becomes a parallel wavefront with respect to the receiving surface.

Output signals from the respective elements of the delay line 5 and # 0 to #N are inputted to the respective constituent circuits # 0 to #N of the phase difference detection circuit 11. Hereinafter, description will be made with reference to the flowchart of FIG.

Step 1 The phase difference detection circuit 11 detects the output signal of the delay line 5 input to each of the constituent circuits # 0 to #N and the reference signal S input to each of the constituent circuits # 0 to #N. The phase difference is detected and each phase difference is converted into a digital signal. Phase difference detection circuit 1
The phase difference signal of the output of 1 is Δφ _k (the phase difference of the _0th element is Δφ ₀ , the phase difference of the _kth element is Δφ _k ).

Step 2 Set _k of Δφ k to 1. Also, the up / down counter 14 is set to zero.

Step 3 The comparator 12 inputs Δφ _k and Δφ _{k-1 of the} two adjacent signals inputted.
The phase difference is calculated and the data shown in the following equation is output.

When Δφ _k −Δφ _k-1 <−180 ° → 1 When Δφ _k −Δφ _k-1 > 180 ° → −1 180 °> Δφ _k −Δφ _k-1 > −180 ° → Step 4 The output of the comparator 12 is input to the offset generation circuit 13, and the up / down counter 14 is operated. The operation of the up / down counter is as follows.

Input 1: Counter 1 up Input-1: Counter 1 down Input 0: Counter does not change Step 5 The output of the up / down counter 14 is input to the 360 ° multiplier 15 and multiplied by 360 ° to obtain the offset. It is output as a value.

Step 6 The offset value is input to the adder 16, and the adder 16 adds the offset value to the phase difference data Δφ _k input from the phase difference detection circuit 11. Output data after addition Δφ _k ′
Is as follows.

Δφ _k ′ = Δφ _k + offset value Step 7 Check if k is less than N. If it is smaller, go to step 8. If not smaller, that is, if they are equal, the process ends.

Step 8: Add 1 to k, and return to step 3. This repetition is k
Continue until = N.

The mechanism of generating the correction value will be described with reference to FIG. In the figure, the same parts as those in FIG. 1 are designated by the same reference numerals. The detection value of the output of the kth phase difference detection circuit 11 and the detection value of the output of the k−1th phase difference detection circuit 11 are input to the kth comparator 12, and the phase difference Δφ
_The following data is output by comparing _k with Δφ _k-1 .

Δφ _k −Δφ _k-1 <− 180 ° → 1 Δφ _k −Δφ _k-1 > 180 ° → −1−180 ° <Δφ _k −Δφ _k-1 <180 ° → 0 Up / down counter 14 is the input data is 1
When it is, it goes up by 1, and when it is -1, it goes down by 1. When it is 0, the current value is held. This value is 3 in 360 ° multiplier 15.
It is multiplied by 60 ° and input to the adder 16. Adder 1
6 is the output signal of the #k element detection circuit
The output data of the 0 ° multiplier 15 is added, and the correction value Δ
Output φ _k ′.

As described above, according to the present embodiment, the accumulation of the phase difference detection error can be eliminated by detecting the phase difference between the signals of the respective elements using the same signal as the reference signal.

Further, by paying attention to the continuity of the phase aberration that may occur in the living body, and detecting the phase difference with the same reference signal as a reference, there are cases where the phase difference detection range is exceeded.
It becomes possible to detect the aliasing that occurs at that time as a discontinuous point, adjust the offset value, and grasp it as a continuous value, so that it is possible to accurately detect a wide range of phase aberrations.

The present invention is not limited to the above embodiment. FIG. 6 is a block diagram of another embodiment of the present invention.
In this embodiment, the circuit is simplified by using one phase detection circuit 11. In the figure, the same parts as those in FIG. 1 are designated by the same reference numerals. In the figure, 17 is a switch for sequentially switching and inputting the output of the delay line 5 connected to each element of the ultrasonic probe 2 to one phase difference detection circuit 11 for each transmission, and 18 is It is a latch that temporarily holds the phase difference output detected by the phase difference detection circuit 11.

Reference numeral 19 is a memory for storing the output of the adder 16.

Next, the operation of the embodiment configured as described above will be described. # 0 of the ultrasonic probe 2 during the first transmission
The signal of the element is input to the phase difference detection circuit 11 via the # 0 delay line 5 and the # 0 contact of the switch 17, and the phase difference Δφ ₀ is detected. The latch 18 outputs 0 at the first transmission. Δφ ₀ is compared with the output 0 of the latch 18 in the comparator 12, Δφ ₀ is output, and stored in the memory 19 via the adder 16. After this latch 1
The clock is sent to 8 and the latch 18 latches Δφ ₀ .

During the second transmission, the phase difference Δφ of the # 1 element
₁ is detected and input to the comparator 12. Comparator 12
Δφ ₀ latched in the latch 18 is input to and is compared, and a corrected signal Δφ ₁ ′ is output. The operations of the comparator 12, the offset generation circuit 13, and the adder 16 are the same as those in the embodiment shown in FIG. Output signal Δ
After φ ₁ ′ is stored in the memory 19, a clock is sent to the latch 18 and the phase difference signal Δφ ₁ is latched.

At the time of the third wave transmission, the comparator 12 has Δφ.
₂ and Δφ ₁ from the latch 18 are input and compared, and Δφ ₁
φ ₂ ′ is stored in the memory 19.

Thereafter, the same operation is repeated up to #N element,
The measurement data Δφ ₁ , Δφ ₁ ′, Δφ ₂ ′, ..., Δφ _N ′ from the # 0 element to the #N element are stored in the memory 19, and when the stored data are all output from the memory 19. It

As described above, in this embodiment, only one latch 18 and one memory 19 are added, and only the switch of N + 1 contacts is provided, and the phase difference detection circuit 11 and the comparator 1 are provided.
2. Only one adder 16 is required. However, the time becomes N + 1 times.

If k sets of circuits are prepared, Δ
Outputs up to φ _k ′ are obtained. In this case, if the reference signal S and the clock are synchronized, the phase relationship between the echo and the reference signal S does not change regardless of how many times the waves are transmitted, and a correct phase difference can be obtained.

[0046]

As described above in detail, according to the present invention, the phase aberration can be obtained without accumulating the detection error generated by adding the echo signals received by the respective elements, and the accuracy can be improved. It becomes possible to detect the phase aberration that does not decrease, and the practical effect is great.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of correction of data by offset.

FIG. 3 is a flowchart of the operation of the embodiment of the present invention.

FIG. 4 is an explanatory diagram of a circuit for generating a correction value.

FIG. 5 is an explanatory diagram of a phase aberration detecting method of a conventional ultrasonic diagnostic apparatus.

FIG. 6 is a block diagram of an apparatus according to another embodiment of the present invention.

[Explanation of symbols]

 2 Ultrasonic probe 11 Phase difference detection circuit 12 Comparator 13 Offset generation circuit 14 Up / down counter 15 360 ° multiplier 16 Adder

Claims (1)

[Claims] 1. An ultrasonic diagnostic apparatus for correcting phase aberration of a received signal, wherein a phase difference detection circuit for detecting a phase difference between signals from respective elements of the ultrasonic probe (2) using a constant signal as a reference signal. (1
1) and the phase difference signal from each adjacent circuit of the phase difference detection circuit (11) are compared, the discontinuity point is detected, and the data of 1 and -1 is output according to the discontinuity state. (12), an up / down counter (14) for adjusting the data to be held according to the output data of each element from the comparator (12), and the up / down counter (14) 360 ° multiplier (1 that multiplies the output data of
5) The offset generation circuit (13), the output data of the phase difference detection circuit (11), and the corresponding output data of the offset generation circuit (13) are added and output. An ultrasonic diagnostic apparatus, comprising: an adder (16) having the same number of constituent circuits as that of the adder (12).