JPH10328178A - Ultrasound diagnostic equipment - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide an ultrasonic apparatus capable of improving the quality of a measurement image. SOLUTION: A probe composed of a plurality of vibrating elements for transmitting and receiving ultrasonic signals, a plurality of delay means for giving a predetermined delay to the ultrasonic signals received by the vibrating elements, the vibrating element and the delay Reconnecting means for reconnecting with means,
Adding means for adding the ultrasonic signal after the delay,
In an ultrasonic diagnostic apparatus that constructs and displays an ultrasonic image instructed by the examiner from the ultrasonic signal after the delay, in the vibration element that receives the ultrasonic signal used for the addition,
Correlation value measurement means for measuring a correlation value between adjacent delay means from the delay means connected to the vibration element on one end side arranged on the outermost side to the delay means connected to the vibration element on the other end side, A delay amount correcting unit that corrects a delay amount of the delay unit based on the correlation value.

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 a technique which is effective when applied to correction of a delay time distribution of a probe received signal due to a non-uniform medium in a subject. Things.

[0002]

2. Description of the Related Art A conventional ultrasonic diagnostic apparatus transmits ultrasonic waves from a plurality of ultrasonic transducers (hereinafter abbreviated as "vibrators") and reflects reflected waves from inside a subject. Received by the ultrasonic transducer, amplify the received signal, in order to electrically focus the received signal from each transducer, perform a delay process by a wavefront from a desired position to be a focus, The signals after the delay processing are added to form an ultrasonic beam. At this time, the focal point, that is, the reception focus point is changed with time in a multi-stage manner or dynamically.

[0006] First, FIG. 6 is a diagram for explaining a schematic configuration of a conventional ultrasonic diagnostic apparatus, and the conventional ultrasonic diagnostic apparatus will be described. 6A is a diagram for explaining a schematic configuration of a sector scanning type ultrasonic diagnostic apparatus, and FIG. 6B is a view for explaining a schematic configuration of a linear scanning type ultrasonic diagnostic apparatus. FIG.

First, a sector scanning type ultrasonic diagnostic apparatus will be described with reference to FIG. In the following description, for simplicity, the total number of transducers of the probe is 4, the number of transducers used for one ultrasonic transmission / reception is 4, and the number of ultrasonic beams is 3
And

Generally, in sector scanning, the transducer for transmitting and receiving ultrasonic waves is common to all ultrasonic beams, and the beam is scanned in a fan shape by controlling the transmission timing and reception delay time of each transducer. I was That is, FIG.
In all of the ultrasonic beams 50 to 52 shown in FIG.
The transducers 40 to 43 have been used as the ultrasonic transmitting and receiving elements. Therefore, one delay line can be fixedly connected to one vibrator. In the sector type ultrasonic diagnostic apparatus shown in FIG. 6A, the transducer 40 is connected to the delay line 60,
The vibrator 41 is connected to a delay line 61, and the vibrator 42 is connected to a delay line 62.
In addition, the vibrator 43 is connected to the delay line 63, and the delay amount of the delay lines 60 to 63 is changed for each ultrasonic beam.

Next, a linear scanning type ultrasonic diagnostic apparatus will be described with reference to FIG. In the following description, for simplicity, the total number of transducers of the probe is 6, the number of transducers used for one ultrasonic transmission / reception is 4, and the number of ultrasonic beams is 3
And

[0007] In general, in linear scanning, beams are scanned in parallel by sequentially switching (scanning) transducers for transmitting and receiving ultrasonic waves for each ultrasonic beam. In other words, the beams 50 to 43 shown in FIG.
And the beams 51 by the vibrators 41 to 44 and the vibrators 42 to 4
5, the beam 52 was formed. Therefore, the number of delay lines required for one ultrasonic transmission / reception was small compared to the total number of transducers.

For this reason, in the conventional linear scanning type ultrasonic diagnostic apparatus, the rotary switch 70 is provided between the transducer and the delay line.
And, for each of the transmitted and received waves of each beam, as shown in FIG.
The oscillator connected to the delay line was changed. That is,
In the beam 50, as shown in FIG.
And the delay line 60, the vibrator 41 and the delay line 61, the vibrator 42 and the delay line 62, and the vibrator 43 and the delay line 63, respectively. In the beam 51, the vibrator 41 and the delay line 60, the vibrator 42 and the delay line 61,
The vibrator 43 and the delay line 63 are connected to the vibrator 44 and the delay line 63.
And were connected respectively. Further, in the beam 52, the oscillator 42 and the delay line 60 are connected, the oscillator 43 and the delay line 61 are connected, the oscillator 44 and the delay line 62 are connected, and the oscillator 45 and the delay line 63 are connected. Was. Therefore, it is possible to switch the connection between the vibrator and the delay line without changing the arrangement order of the vibrators 40 to 45 and the arrangement order of the delay lines 60 to 63. For details of the electronic operation method of the ultrasonic beam, refer to, for example, “Medical Ultrasonic Equipment Handbook, pp. 129-152, edited by Japan Electronics Machinery Association, Corona Co., Ltd.” in Document 3.

As apparent from FIG. 6 (b), in particular, in a linear scanning type ultrasonic diagnostic apparatus, a large number of transducers are required in order to photograph a predetermined area. A number of delay means and changeover switches are prepared, and at the time of scanning, the connection between the vibrator and the delay means is switched by the changeover switch in synchronization with the scanning of the ultrasonic wave.

In recent years, ultrasonic diagnostic apparatuses have been improved in resolution with the digitization of transducer materials, delay means and digital processing technology of received signals, and radiation such as other X-ray apparatuses. Since the soft tissue can be easily and clearly described without exposure and without using a contrast agent or the like, it is an indispensable diagnostic device in a wide range. However, the resolution of an ultrasonic diagnostic apparatus is still lower than that of an X-ray apparatus or the like, and further improvement in resolution is expected. As a technique for improving the resolution of the ultrasonic diagnostic apparatus, for example, a technique of correcting the phase of a reflected pulse received by each transducer, which is out of phase due to a non-uniform medium in a subject, and then adding the corrected pulses. There is.

First, FIG. 8 is a view for explaining a delay time distribution for forming a high-resolution ultrasonic beam in a human body which is a non-uniform medium, and a correction of a pulse wavefront in a non-uniform medium will be described. . However, in the following description, only the operation at the time of receiving waves will be described for simplicity.

When the medium has a known sound velocity and is uniform, the reflected pulse wavefront (received signal wavefront) from the reflector 31 reaches the transducers 21 to 25 as an ideal wavefront 32. At this time, the vibrator 2 depends on the positional relationship between the reflector 31 and the vibrators 21 to 25.
3 is the earliest, and the reflected pulse reaches the oscillators 21 and 25 latest. Therefore, in order to make the arrival times of all the reflected pulses uniform, the pulses received by the oscillators 22 to 24 are given an appropriate delay. In this way, the arrival times of the total reflection pulses are adjusted and then added to amplify only the reception pulses from the target direction, thereby forming a high-resolution tomographic image. Here, in the case of a uniform medium with a known sound velocity, the delay to be given could be obtained analytically as shown below.

The distance between the vibrators 21 to 25 and the reflector 31 is Li (where 1 ≦ i ≦ 5), the set sound velocity of the ultrasonic diagnostic apparatus is c, and the delay time given to the signals received by the vibrators 21 to 25 is c. Τi (where 1 ≦ i ≦ 5), Li (where 1 ≦ i
If Lmax is the largest one among ≦ 5), τi can be expressed by the following equation 1.

[0014]

Τi = (Lmax−Li) / c (1) However, in practice, the vibrators 21 to 25 and the reflector 31 are actually used.
Since the non-uniform medium 34 exists between the pulse wavefront and the distorted wavefront 33, the pulse wavefront becomes as shown in FIG. Therefore, τi is optimal as the initial delay time given to each transducer received signal, but in order to obtain a high-resolution tomographic image, the delay time in consideration of the distorted wavefront 33 is further added to the initial delay time. Needs to be given.

As a technique for measuring the correction amount, for example, “IEEE Transactionson Ultrasonic, Ferro”
electrics, and Frequency Control, Vol.39 No.6 pp.700
-707 (1992) ”or“ IEEE 1991 Ultras
onics Symposium Proceeding pp. 1189-1193 (1991) ". The technology described in this document is based on the case where an object having a different sound velocity exists between a transducer that transmits and receives ultrasonic waves and a reflector that reflects the ultrasonic waves (hereinafter, referred to as an “inhomogeneous medium”). The present invention relates to a technique for correcting the influence of a non-uniform medium on a pulse wavefront. According to this correction technique, first, the phase shift of the reflected pulse accompanying the shift of the propagation speed of the ultrasonic wave due to the non-uniform medium is calculated by the correlation operation between all the adjacent transducers. Next, based on the calculation result, by correcting the delay time of the delay means, the distortion of the pulse wavefront due to the propagation of the ultrasonic wave in the non-uniform medium is corrected, and the resolution of the ultrasonic image is improved. Met.

For this phase shift, for example, as shown in FIG. 9, outputs of adjacent delay lines among delay lines 60 to 63 are detected by correlators 80 to 82, respectively.

[0017]

SUMMARY OF THE INVENTION As a result of studying the above prior art, the present inventor has found the following problems.

However, in the correction technique described in the above-mentioned document, the delay time between the received signals is detected by a correlator based on the output of an adjacent delay means, and the pulse wavefront by an inhomogeneous medium is detected based on the detected time. , That is, the distortion wavefront was corrected.

For this reason, a sector scanning type ultrasonic diagnostic apparatus in which a transducer and a delay line are connected one-to-one, or a linear scanning type ultrasonic diagnostic apparatus in which a transducer and a delay line are connected by a rotary switch. This is effective when the order of arrangement of the vibrator and the delay line is the same as in an ultrasonic diagnostic apparatus.

On the other hand, in recent years, in a linear scanning type ultrasonic diagnostic apparatus, in order to improve image quality and reduce the size of the diagnostic apparatus main body, switching noise at the time of switching of a switch connecting a vibrator and a delay line is changed. , And the circuit scale of the changeover switch, that is, downsizing is desired. For this reason, in the recent linear scanning type ultrasonic diagnostic apparatus, the scanning of the ultrasonic beam is not performed at the same time as the ultrasonic beam scanning, instead of switching all the connection points between the transducer and the delay line using the rotary switch. Along with the above, the switching operation of disconnecting the unnecessary transducer from the delay line to which the transducer was connected and connecting the disconnected delay line to the transducer required for scanning is repeated, And the delay line. In addition,
In the following description, a switch that performs such switching is referred to as a “selection switch”.

However, in the ultrasonic diagnostic apparatus using this selection switch, the order of the transducers does not match the order of the delay lines, and the delay time set for the delay lines is set for each scan. The pulse wavefront of the received signal was aligned. For this reason, when the correction technique described in the above-mentioned Document 1 or 2 is applied to such a linear scanning type ultrasonic diagnostic apparatus, it is necessary to obtain a correction time between transducers that should be adjacent to each other. There was a problem that the correction could not be performed.

Furthermore, since the non-adjacent transducers are originally assumed to be adjacent to each other and the delay time is corrected, the displacement of the pulse wavefront, that is, the distortion is increased in some cases. However, there is a problem that the quality of the image is deteriorated more than the influence of the non-uniform medium.

An object of the present invention is to provide an ultrasonic apparatus capable of improving the quality of a measured image.

Another object of the present invention is to provide a technique capable of calculating a correlation between adjacent transducers even when the arrangement order of the transducers and the delay means do not match. To provide.

Another object of the present invention is to provide an ultrasonic diagnostic apparatus capable of correcting a delay time in consideration of a non-uniform medium even in linear scanning without using a rotary switch.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0027]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

(1) A probe comprising a plurality of vibrating elements for transmitting and receiving an ultrasonic signal, a plurality of delay means for giving a predetermined delay to the ultrasonic signal received by the vibrating element, and the probe And a delay unit provided between the delay unit, the connection unit for switching the connection between the vibration element and the delay unit, and an addition unit for adding the ultrasonic signal after the delay, In an ultrasonic diagnostic apparatus that constructs and displays an ultrasonic image instructed by an examiner from an ultrasonic signal, an outermost end of a vibration element that receives the ultrasonic signal used for the addition is disposed. From the delay means connected to the vibrating element on the side, a correlation value measuring means for measuring a correlation value between adjacent delay means to the delay means connected to the vibrating element on the other end side, based on the correlation value, Delay amount correcting means for correcting the delay amount of the delay means Comprising the door.

(2) In the ultrasonic diagnostic apparatus according to claim 1, the number of the correlation value measuring means is equal to the number of the delay means.

(3) The ultrasonic diagnostic apparatus according to claim 1 or 2, wherein the vibrating element, which is unnecessary by controlling the connection changing means, is connected for each transmission / reception. And a linear scanning control means for connecting a vibrating element required for the next transmission / reception wave.

(4) In the ultrasonic diagnostic apparatus according to any one of claims 1 to 3, the number of the delay means is:
Less than the number of the vibrating elements.

According to the above-mentioned means (1), (3) and (4), for example, in a linear scanning type ultrasonic diagnostic apparatus, by using the correlation value measuring means, the measurement has not been conventionally performed. It is possible to measure the correlation value between the outermost one end delay means, ie, the first delay means, and the other end delay means, ie, the last delay means, and to correct the correlation value. However, since only the correlation value between the adjacent vibration elements is used to correct the delay time of the delay means, even when the arrangement order of the vibration elements does not match the arrangement order of the delay means, In addition, it is possible to correct the delay time between the adjacent vibration elements, that is, to correct the distortion of the pulse wavefront due to the non-uniform medium.

Therefore, the resolution of the measurement image, that is, the display image can be improved. Therefore, the image quality of the display image is improved.

According to the above-mentioned means (2), for example, in addition to the correlation value measuring means for measuring the correlation value between the delay means between the adjacent delay means among the delay means, the outermost one is disposed. Since the correlation value measuring means for measuring the correlation value between the delay means on one side and the delay means on the other side can be arranged, the arrangement order of the vibrating elements and the arrangement order of the delay means are the same. Even if they do not match, the delay time between adjacent vibrating elements can always be corrected.

Therefore, the resolution of the measurement image, that is, the display image can be improved, that is, the image quality of the display image can be improved.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings together with embodiments (examples) of the invention.

In all the drawings for describing the embodiments of the present invention, those having the same functions are denoted by the same reference numerals, and their repeated description will be omitted.

FIG. 1 is a block diagram showing a schematic configuration of an ultrasonic diagnostic apparatus according to an embodiment of the present invention, wherein 1 is a probe, 2 is a switching unit (connection changing means), 3 is a delay unit,
Reference numeral 4 denotes an adder (adder), 5 denotes a selector, 41 to 46 vibrators, 61 to 64, delay lines, and 81 to 84, correlators (correlation value measuring means). Note that the ultrasonic diagnostic apparatus according to the present embodiment uses ultrasonic waves (ultrasonic beams) transmitted from the probe 1.
Is a linear scanning type ultrasonic diagnostic apparatus that scans in a direction in which the transducers 41 to 46 are arranged.

In FIG. 1, a probe 1 is a known probe having first to sixth transducers 41 to 46, and each transducer 41 to 46 is connected to the switching unit 2.

The switching section 2 outputs four transducers necessary for linear scanning from among the first to sixth transducers 41 to 46 based on the output of a scanning control means (not shown).
Are selection switches for connecting to the respective delay lines 61 to 64. The details will be described later.

The delay unit 3 includes first to fourth delay lines 61 to 6
In the present embodiment, each received signal output from the switching unit 2 is converted into a digital signal, and then the received digital signal is converted into a delay time control unit (not shown) and a selecting unit 5. Is performed, and the signal after the delay processing is added to the adder 4 and the first to fourth signals.
Are output to the correlators 81 to 84. The details of the delay unit 3 will be described later.

The adder 4 comprises a well-known adder. In the present embodiment, the adder 4 adds the received digital signal subjected to the delay time processing output from the delay 3 and then uses the added value for display control (not shown). Output to the means.

The selection unit 5 selects one of the first to fourth correlators 80 to 84 based on the output of a scanning control unit (not shown).
Means for selecting the outputs of the correlators 81 to 84 for calculating the correlation values between the delay lines connected to the adjacent transducers and outputting the output values to the delay unit 3; Based on the first to fourth correlators 81 to 84
This is realized by using three well-known four-input one-output switches that output only one of them.

The first to sixth transducers 41 to 46 are well-known transducers, and in this embodiment, the number of transducers of the probe 1 is assumed to be six for simplicity of description. . Further, for the same reason, in the present embodiment, the number of transducers used for one ultrasonic transmission / reception is set to four, so that the number of delay lines and correlators is also set to four.

The first to fourth delay lines 61 to 64 are provided with A / D conversion means for converting an analog signal into a digital signal, and a reception signal (received digital signal) converted into the digital signal for a predetermined time. And a delay means for giving a delay of.

The first to fourth correlators 81 to 84 have two inputs and one
The output of the first correlator 81 is an output of the first delay line 61 and the output of the second delay line 62, and the input of the second correlator 82 is an output correlator. The output of the third delay line 63 and the input of the third correlator 83 are connected to the output of the third delay line 63 and the output of the fourth delay line 64, respectively.
4 inputs are connected to the outputs of the fourth delay line 64 and the first delay line 61, respectively. The details of the first to fourth correlators 81 to 84 will be described later.

Next, FIG. 2 is a diagram for explaining a schematic configuration of the delay unit of the present embodiment, and the configuration and operation of the delay unit 3 will be described below with reference to FIG. As shown in FIG. 2, each of the delay lines 61 to 64 includes an ADC 201, a delay unit 202, and a delay control unit (delay amount correction unit) 203.
It is composed of

In FIG. 2, the ADC 201 is a well-known A /
A D converter, and in the present embodiment, based on an output (sampling output) of a scanning control unit (not shown)
After converting the analog received signal input from the switching unit 2 into a digital signal (digital information), each of the delay units 2
02 is output.

The delay unit 202 is a well-known digital delay unit such as an SRAM, for example, and delays a predetermined time by controlling the read address of the received digital signal stored in the SRAM by the delay control unit 203. .

The delay control means 203 is adapted to control the delay means 20 of the first to fourth delay lines 61 to 64 based on the delay time control means (not shown) and the delay time inputted from the selector 5.
This is a means for setting a read address of the second information, and is realized by, for example, a program operating on a known information processing device.

Next, the operation of the ultrasonic diagnostic apparatus of the present embodiment at the time of receiving a wave will be described with reference to FIGS. In the description of the operation, first, the ultrasonic waves (first ultrasonic beams) transmitted from the first to fourth transducers 41 to 44 are used.
Is received by the four transducers 41 to 44, and then the second
After the ultrasonic waves (second ultrasonic beams) transmitted from the fifth to fourth transducers 42 to 45 are received by the four transducers 42 to 45, the third to sixth transducers are further received. The case where the ultrasonic waves (third ultrasonic beam) transmitted from 43 to 46 are received by these four transducers 43 to 46 will be described.

First, the ultrasonic waves received by the first to fourth transducers 41 to 44 are converted into reception signals, that is, analog electric signals by the first to sixth transducers 41 to 46. Then, it is output to the switching unit 2.

The received signal input to the switching unit 2 is input to the first to fourth delay lines 61 to 64 connected to the first to fourth transducers 41 to 44, respectively, as described above. That is, it is input to the ADC 201 of each of the delay lines 61 to 64.

The ADC 201 converts the received analog received signal into a digital received digital signal at the sampling output timing of the scanning control means (not shown), and outputs the digital received digital signal to the delay means 202 connected to each ADC 201. As a result, the received digital signal is written into each delay means 202 in order.

The received digital signal written or stored in each of the delay means 202 is supplied with the instruction of the delay control means 203 after a predetermined time elapses.
Reading from all the delay units 202 is started. However, the read start address at this time is an address value determined by the delay control unit 203 based on the correlation value output from the delay time control unit (not shown) and the selection unit 5. In this embodiment, the read address at this time is based on, for example, the second vibrator 42, which is the vibrator closest to the center of the wave transmitted by the delay control unit 203.

Therefore, in the present embodiment, the third vibrator 43 closest to the center of the transmission / reception wave, that is, the second vibrator 42 closest to the center of the transmission / reception wave, and the second vibrator 43 closest to the center of the transmission / reception wave are used. First, based on the correlation value with the oscillator 42,
The delay control means 203 determines the delay means 202 to be read first. Next, the delay control means 203 calculates a read address difference corresponding to a time difference based on the correlation value and a delay time control means (not shown) for the read address of the delay line, and then outputs the data of each read address from each delay means 202. That is, by reading out the received wave digital signal, it is possible to read out data necessary for the received wave focus.

The adder 4 adds the data read out according to the above-described procedure, performs phase phasing, performs various types of filter processing by well-known signal processing means (not shown), and outputs the data to a display device for display.

Next, FIG. 3 is a block diagram for explaining a schematic configuration of the switching unit of the present embodiment, and FIG. 4 is a block diagram for explaining a schematic configuration of the selection unit of the present embodiment. Hereinafter, the configurations of the switching unit 2 and the selection unit 5 according to the present embodiment will be described with reference to FIGS.

As described above, in the ultrasonic diagnostic apparatus according to the present embodiment, since the number of transducers is six and the number of delay lines is four, the number of transducer switching during scanning is two. Therefore, in the present embodiment, as shown in FIG. 3, by switching only the input of the first delay line 61 and the input of the second delay line 62, linear scanning can be realized.

In FIG. 3, a first switching means 71 and a second switching means 72 are both well-known two-input and one-output switching means having a control input. The input signal of the b input terminal is output to the c output terminal. Therefore, in the present embodiment, in order to switch the input of the first and second delay lines 61 and 62, the first oscillator 41 is connected to the a input terminal of the first switching means, and the b input is The fifth oscillator 45 is connected to the terminal, and the first delay line 61 is connected to the c output terminal. The second oscillator 42 is connected to the a input terminal of the second switching means, and the sixth oscillator 4 is connected to the b input terminal.
6 and a second delay line 62 are connected to the c output terminal, respectively.

On the other hand, as described above, the selection unit 4
This can be realized by selecting only the correlator output actually connected to the adjacent vibrator from the fourth to fourth correlators 81 to 84. Therefore, as shown in FIG. 4, the selector 4 of the present embodiment includes two 2-input / 1-output selectors 91 and 92.

In FIG. 4, first and second selecting means 91,
Reference numeral 92 denotes a well-known two-input / one-output switching means for outputting an input signal from the a input terminal or the b input terminal to the c output terminal based on a control input (not shown), similarly to the above-described switching means. Also, the first and second selection means 9
1 and 92 select a signal to be output from the c output from the a input and the b input based on the control output of a scanning control unit (not shown). Therefore, in the present embodiment, the first selecting means 91 has the a input terminal connected to the first correlator 81,
The b input terminal is connected to the fourth correlator 84, and the c output terminal is connected to the delay unit 3. Also, the second selecting means 92
Has an input terminal a connected to the second correlator 82, an input terminal b connected to the fourth correlator 84, and an output terminal c connected to the delay unit 3.

Next, FIG. 5 is a diagram for explaining the connection of the transducer, the delay line and the correlator in the ultrasonic diagnostic apparatus according to the present embodiment. Hereinafter, based on FIG. The operation of the selection unit 5 will be described. In FIG.
5A shows a case where a wave is transmitted from the first to fourth transducers 41 to 44, and FIG. 5B shows a case where a wave is transmitted from the second to fifth transducers 42 to 45. ) Are the third to sixth transducers 43
26 shows connections with a vibrator, a delay line, and a correlator when transmitting waves from # 46 to # 46.

First, in the wave receiving operation at the time of the first wave transmission and reception, as shown in FIG. 5A, the reflected ultrasonic waves are received by the first to fourth transducers 41 to 44. Scanning control means (not shown) comprises first and second switching means 71 and 72.
Further, control is performed such that the a input terminal is selected by the first and second selecting means 91 and 92. Therefore, the first vibrator 41
The received signal detected by the second oscillator 42 is sent to the first delay line 61, the received signal detected by the second oscillator 42 is sent to the second delay line 62,
The received signal detected by the third transducer 43 is supplied to the third delay line 63, and the received signal detected by the fourth transducer 44 is supplied to the fourth delay line 63.
, Respectively. In the correlator, the outputs of the first to third correlators 81 to 83 are output to the delay unit 3, respectively.

In the next operation at the time of second transmission / reception, FIG.
As shown in (b), the reflected ultrasonic waves are transmitted to the second to fifth ultrasonic waves.
The oscillators 42 to 45 receive the wave, so that the scanning control means (not shown) uses the b input terminal for the first switching means 71,
The second switching means 72 has an a input terminal, the first selection means 91 has a b input terminal, and the second selection means 92 has an a input terminal.
Control to select input terminal. Therefore, the second
The received signal detected by the oscillator 42 of the second delay line 62
The received signal detected by the third vibrator 43 is supplied to the third delay line 63, the received signal detected by the fourth vibrator 44 is supplied to the fourth delay line 64, and the fifth vibration The received signals detected by the terminals 45 are input to the first delay lines 61, respectively. Also,
In the correlator, since the first selecting means 91 selects the b input terminal, the first correlator 81 for measuring the correlation value of the non-adjacent oscillators, that is, the fifth oscillator 45 is connected. Instead of the output of the first correlator 81 that measures the correlation value between the first delay line 61 and the second delay line 62 to which the second oscillator 42 is connected, the fourth oscillator 44 Output of a fourth correlator 84 for measuring a correlation value between the first delay line 61 to which the adjacent fifth oscillator 45 is connected and the fourth delay line 64 to which the fourth oscillator 44 is connected Is output to the delay unit 3. On the other hand, the outputs of the second and third correlators 82 and 83 are the same as in the first transmission / reception operation.

At the time of the third transmission / reception, that is, the last transmission / reception of one scan, as shown in FIG.
Since the reflected ultrasonic waves are received by the third to sixth transducers 43 to 46, the scanning control means (not shown) uses the b input terminal for the first and second switching means 71 and 72, and the first input means for the first and second switching means 71 and 72. The selection means 91 has an a input terminal, and the second selection means 92 has a b terminal.
Control to select input terminal. Therefore, the third
The received signal detected by the vibrator 43 is the third delay line 63
The received signal detected by the fourth vibrator 44 is supplied to the fourth delay line 64, the received signal detected by the fifth vibrator 45 is supplied to the first delay line 61, and the sixth vibration The received signals detected by the daughters 46 are input to the second delay lines 62, respectively. Also,
In the correlator, since the second selecting means 92 selects the b input terminal, the second correlator 82 for measuring the correlation value of non-adjacent oscillators, that is, the sixth oscillator 46 is connected. Instead of the output of the second correlator 82 for measuring the correlation value between the second delay line 62 and the third delay line 63 to which the third oscillator 43 is connected, the fourth oscillator 44 Output of a fourth correlator 84 for measuring a correlation value between the first delay line 61 to which the adjacent fifth oscillator 45 is connected and the fourth delay line 64 to which the fourth oscillator 44 is connected Is output to the delay unit 3. Further, since the first selecting means selects the a input terminal, the first delay line 61 to which the fifth vibrator 45 is connected and the second delay to which the sixth vibrator 46 is connected are connected. Line 62
The output of the correlator 81 for measuring the correlation value with the signal is output to the delay unit 3 in the same manner as the above-described first transmission / reception wave. On the other hand, the output of the third correlator 83 is the same as the first and second transmission / reception operations.

At this time, in the delay unit 3, as described above, the output of the scanning control means (not shown) and the correlators 81 to 81 are used.
Based on 84, a delay time control unit (not shown) sets a read address corresponding to a change in sound speed due to a non-uniform medium, that is, a correlation value, from the correlation value input from the selection unit 5. At this time, the relationship between the correlation value and the read address and the relationship between the control input and the transducer, the delay line, and the correlator input from the scanning control means are stored as table data in storage means (not shown), for example. Every
The delay time control means can determine the read address in a short time by referring to the table data based on the input value.

Next, a procedure for obtaining a delay time correction amount for determining a read address from a correlation value, that is, a time difference between input signals, by the correlator according to the present embodiment will be described.

First, the received signal after the initial delay time is given is represented by the following equation (2).

[0070]

Cos (ω (t + τ1)) (Equation 2) cos (ω (t + τ2)) (Equation 3) Here, the time difference τ1-τ2 of Equations 2 and 3 can be obtained. If possible, replace Equation 3 with cos (ω (t + τ2 + τ1-τ
2)) = cos (ω (t + τ1)) and can be made equal to Equation 2.

Therefore, here, a method of obtaining τ1−τ2 from the phase difference between two signals after performing a complex conversion on Expressions 2 and 3 will be described.

When Expression 2 is represented by a complex expression, Expression 4 of the following Expression 3 is obtained.
When Expression 3 is displayed in a complex form, Expression 5 of Expression 3 below is obtained.

[0073]

(Equation 3)

Here, θ1 = ωτ1 and θ2 = ωτ2.

Equations 4 and 5 are multiplied by the following equation 6.

[0076]

(Equation 4)

This is called complex mixing. The result of the multiplication is as shown in Equations 7 and 8 below.

[0078]

(Equation 5)

When the high-frequency components are removed by applying low-pass filter processing to Equations 7 and 8 of Equation 5, Equations 7 and 8 become Equations 9 and 10, respectively.

[0080]

(Equation 6)

When the complex conjugate of the equation (9) is multiplied by the equation (10), the following equation (11) is obtained.

[0082]

(Equation 7)

Next, when the arc tangent operation of the real part and the imaginary part of the equation (11) is calculated, the following equation (12) is obtained.

[0084]

(Equation 8)

Therefore, θ1−θ2 is obtained from the equation (12). Here, as shown in Equation 13 below, Equation 1
By dividing 2 by ω, the correction amount τ1−τ
2 can be obtained.

[0086]

(Equation 9)

However, a method of performing complex mixing on a received signal to form an ultrasonic beam in a low frequency region is as follows.
Generally, it is called baseband signal processing. In this baseband signal processing, the calculation (processing) shown in Expressions 9 and 10 is required for the ultrasonic beam formation regardless of whether or not the phase difference between signals between adjacent transducers is obtained.
Therefore, for example, in the baseband signal processing, a correlator can be used as a means for performing the processing of Expressions 11 to 13. That is, in the ultrasonic diagnostic apparatus using the baseband signal processing, the configuration of the correlator can be simplified.

As described above, in the ultrasonic diagnostic apparatus according to the present embodiment, the correlation value between adjacent ones of the first to fourth delay lines 61 to 64 is measured. In addition to the first to third correlators 81 to 83, a fourth correlator 84 for measuring a correlation value between the outermost first delay line 61 and the fourth delay line 64 is provided. And the first
To sixth oscillators 41 to 46 and first and second delay lines 61 to 61
Based on the control signal of the scanning control means for controlling the switching unit 2 for reconnecting with the 64, only the output of the correlator which measures the correlation value between the delay lines to which the adjacent transducers are connected is selected by the selection unit 5 Is output to the delay unit 3, and the delay control unit 203 of the delay unit 3 corrects the delay time based on the output of the correlator, so that the arrangement order of the transducers and the arrangement order of the delay units match. Even if not, the delay unit 3 always
It is possible to correct the delay time based on the correlation value of the received digital signal after delay of the adjacent probe, that is, to correct the distortion of the pulse wavefront due to the non-uniform medium.

Therefore, in the ultrasonic diagnostic apparatus according to the present embodiment, the resolution of a display image as a measurement image can be improved. That is, the image quality of the display image can be improved.

In this embodiment, the case where the number of vibrators is 6 and the number of delay lines is 4 has been described. However, the present invention is also applicable to the case where the number of vibrators and the number of delay lines are larger than this. Not even.

In this embodiment, the operation has been described particularly when the present invention is applied to a linear scanning type ultrasonic diagnostic apparatus using a selection switch. However, the present invention is not limited to this. It is needless to say that the present invention can be applied to an ultrasonic diagnostic apparatus of a type, an ultrasonic diagnostic apparatus having both a sector type and a linear type and an ultrasonic diagnostic apparatus of a linear type using a rotary switch. In particular, in the sector scanning type ultrasonic diagnostic apparatus, the switching unit 2 is unnecessary because the number of transducers of the probe is equal to the number of transducers used for one ultrasonic transmission / reception.

As described above, the invention made by the present inventor is:
Although specifically described based on the embodiments of the present invention, the present invention is not limited to the embodiments of the present invention, and it is needless to say that various modifications can be made without departing from the gist of the present invention. .

[0093]

The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows.

(1) The quality of a measured image can be improved.

(2) Even if the arrangement order of the transducers does not match the arrangement order of the delay means, the correlation between adjacent transducers can be calculated.

(3) Even in linear scanning without using a rotary switch, the delay time can be corrected in consideration of a non-uniform medium.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating a schematic configuration of a delay unit according to the present embodiment.

FIG. 3 is a block diagram illustrating a schematic configuration of a switching unit according to the present embodiment.

FIG. 4 is a block diagram illustrating a schematic configuration of a selection unit according to the present embodiment.

FIG. 5 is a diagram for explaining connection of a transducer, a delay line, and a correlator in the ultrasonic diagnostic apparatus of the present embodiment.

FIG. 6 is a diagram for explaining a schematic configuration of a conventional ultrasonic diagnostic apparatus.

FIG. 7 is a diagram for explaining connection between a transducer and a delay line in a conventional linear scanning type ultrasonic diagnostic apparatus.

FIG. 8 is a diagram for explaining a delay time distribution for forming a high-resolution ultrasonic beam in a human body that is a non-uniform medium.

FIG. 9 is a diagram for explaining connection between a delay line and a correlator in a conventional ultrasonic diagnostic apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Probe, 2 ... Switching part, 3 ... Delay part, 4 ... Addition part, 5 ... Selection part, 21-25, 40-46 ... Vibrator, 3
1 ... reflector, 32 ... ideal wavefront, 33 ... distorted wavefront, 34 ...
Non-uniform medium, 60-64 delay line, 70 rotation switch, 71, 72 switching means, 80-84 correlator,
91, 92: selection means, 201: ADC, 202: delay means, 203: delay control means.

Claims (4)

[Claims] 1. A probe comprising a plurality of vibrating elements for transmitting and receiving an ultrasonic signal, a plurality of delay means for giving a predetermined delay to an ultrasonic signal received by the vibrating element, and the probe A delay unit configured to switch between the vibrating element and the delay unit; and an addition unit configured to add the delayed ultrasonic signal. In an ultrasonic diagnostic apparatus that constructs and displays an ultrasonic image instructed by an examiner from a sound wave signal, of the vibration elements that have received the ultrasonic signal used for the addition, one end arranged at the outermost side From the delay unit connected to the vibrating element, a correlation value measuring unit that measures a correlation value between adjacent delay units up to the delay unit connected to the vibrating element on the other end, based on the correlation value, Delay amount correcting means for correcting the delay amount of the delay means; Ultrasonic diagnostic apparatus characterized by comprising. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein said correlation value measuring means has the same number as said delay means. 3. The ultrasonic diagnostic apparatus according to claim 1, wherein the control unit controls the reconnecting unit for each transmission and reception, and the delay unit connected to the unnecessary vibration element. An ultrasonic diagnostic apparatus comprising a linear scanning control means for connecting a vibrating element required for the next transmitted / received wave. 4. The ultrasonic diagnostic apparatus according to claim 1, wherein the number of said delay means is smaller than the number of said vibrating elements.