JP2003000599A - Real time three-dimensional ultrasonic imaging system and probe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively provide three-dimensional(3D) imaging at high speed without mechanically moving part and complicated delay control. SOLUTION: A probe 10 has piezoelectric elements arrayed in the form of planar grid, and piezoelectric elements 12T for transmitting and piezoelectric elements 14R for receiving are alternately arranged. The transmitting element group of each of columns and the receiving element group of each of rows are respectively switched for the unit of column and for the unit of row by a transmitting switcher 16 and a receiving switching circuit 18 and a matrix crossing part becomes a detection area. The receiving switcher 18 receives the reflected waves of ultrasonic waves for each row and inputs ultrasonic received signals to a high frequency receiving circuit 28. The received signals are amplified by the high frequency receiving circuit 28 and sent through a control circuit 26 to a sensor image processing circuit 32 later. The sensor image processing circuit 32 reproduces a 3D image from the inputted ultrasonic received signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic imaging apparatus and a probe for imaging using ultrasonic waves, and in particular, in the probe, a signal switching circuit is not provided for each piezoelectric element. TECHNICAL FIELD The present invention relates to a real-time three-dimensional ultrasonic imaging device capable of achieving three-dimensional imaging with an extremely simple configuration and a probe used for the same.

[0002]

2. Description of the Related Art In the general ultrasonic imaging field used for underwater exploration, non-destructive inspection, and medical diagnosis, the production of the probe itself in which piezoelectric elements are arranged in an array at a pitch of 1 mm or less, Due to difficulties such as supplying a high-voltage pulse to each element and manufacturing a circuit for receiving the reception signal of the element, there are few three-dimensional image devices using the two-dimensional array probe currently in practical use, and the array size is small. There are many things. Conventionally, when the method used in a one-dimensional array in which n piezoelectric elements are linearly arranged is brought into a two-dimensional state,
Since the number of elements increases from n to n ² , technical difficulty increases rapidly.

FIG. 7 shows a block diagram of a typical conventional ultrasonic diagnostic apparatus. A transmission circuit 2 for transmitting a high-voltage pulse from the array-type probe 1 to the inspection target 13 is provided, and the signal received by the probe 1 from the reflected wave 11 from the target (target) 9 is a high-frequency reception circuit. The data is input to the memory 4 via 3 and displayed on the CRT 6 by the scan conversion circuit 5. A CPU / control circuit 7 for integrally controlling each circuit is provided. The essential part of this figure is the array type probe 1 and the CPU.
/ It is a part of the control circuit 7. The CPU / control circuit 7 needs to be designed according to the structure of the array of the probe 1.

Spatial scanning / convergence of the ultrasonic beam is realized by electronic delay of the transmission / reception signals to each element of the array type probe 1. FIG. 8 shows the basic principle of electron convergence. The wavefront of the reflected wave 11 returned from the focal point (target 9) is a piezoelectric element (element) forming the array type probe 1.
After being received by 12, the delay element 8 controls the delay, and the isochronous addition results in a strong signal, but the wavefront from other than the focus is not added isochronously.

The image obtained by the above method is called B mode, and is an image of a section through which a fan-shaped beam passes. In order to obtain a cross-sectional image perpendicular to the beam called C mode and a three-dimensional solid image, a probe composed of a one-dimensional array (linear array) is moved in a direction perpendicular to the array direction. is necessary.

There is an ultrasonic sonar device as an application example of the ultrasonic device as described above. Two specific methods for obtaining a three-dimensional image in this ultrasonic sonar device are as follows. There are various methods.

In the first method, the probe is fixed to a rotary shaft and mechanically rotated. In this case, the amount of movement around the rotation axis can be measured using a rotary encoder. However, in this method, since mechanical scanning is performed, the speed of imaging is limited, and many problems such as a sealing problem occur in the mechanical structure of the sensor that moves in water.

In the second method, the probe is moved by freehand, and a special magnetic sensor is used for positioning the probe. A sensor using magnetism capable of detecting such parallel movement of three axes and rotation around the same has been put into practical use and sold.

[0009]

SUMMARY OF THE INVENTION In the above two methods,
Both require mechanical operations and compositing of three-dimensional images by complicated software. In an inspection device or the like that requires real-time processing, the long processing time is a major obstacle.

Therefore, the probe itself is formed into a two-dimensional array, a signal delay circuit is attached to each piezoelectric element, and a calculated delay amount is given to converge the light to an arbitrary point in space, thereby making a three-dimensional image at a stretch. Can be obtained. As shown in FIG. 8, this controls the delay element so that the data of a certain focus in the water is synthesized. However, in order to make this possible for all points in the three-dimensional space, very complicated control is required and the price is also high. Furthermore, there are many technical problems in designing and manufacturing the arrangement of power supply lines and signal lines around a two-dimensional array with a small pitch, and at present the development is aimed at a relatively small array (about 16 × 16 elements). Is being promoted.
Even if this probe is developed, it is next necessary to develop an electronic lens that controls the delay amount of each piezoelectric element. It is expected that an array of 128 × 128 elements will be required in the future, but in this case, 16382 delay elements are required, and a circuit for controlling the delay elements becomes very complicated.

The present invention focuses on the above-mentioned conventional problems, and there is no mechanically moving part, and without performing complicated delay control, an ultrasonic image which can realize three-dimensional imaging at high speed at low cost. It is intended to provide a device and a probe thereof.

[0012]

In order to achieve the above object, a real-time three-dimensional ultrasonic imaging apparatus according to the present invention is a piezoelectric element corresponding to each row and each column of piezoelectric elements arranged in a plane lattice pattern. Of each row or column for transmission and the other for reception 2
Forming a three-dimensional linear array, and providing a switching element for switching between the transmitting element group and the receiving element group on a row-by-row basis or a column-by-column basis, thereby forming a probe having an imaging region in front of the matrix intersection, and the switching means The processing means for reproducing the ternary image of the object to be imaged from the measurement data obtained by the receiving element group for each switching processing by

Further, the probe of the ultrasonic imaging apparatus according to the present invention has a plurality of piezoelectric elements arranged in a plane lattice shape, and piezoelectric elements forming transmitting elements and receiving elements in each matrix direction. Are alternately arranged, and the transmission switching unit that operates the transmission element group arranged in each column (or each row) as a unit and the receiving element group arranged in each row (or each column) as a unit are received. The reception switching device for switching operation is provided.

Piezoelectric elements corresponding to each row and each column of piezoelectric elements arranged in a plane lattice are coupled to each other, for example, row is transmitted and column is received. In this way, it is possible to configure a linear array of a total of 2n piezoelectric elements for transmission and reception. At this time, the signal is fed in one column, that is, n points, and the signal is received in one row, that is, n points. In this way, only 2n wiring points are required, and the circuit configuration becomes remarkably simple. The measurement data thus obtained is computer-processed by a unique algorithm to be converted into a three-dimensional image. Therefore, according to the method of the present invention, there is no mechanically moving part, yet complicated delay control is not required, and a high-speed three-dimensional ultrasonic imaging apparatus can be realized at low cost.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of a three-dimensional real-time ultrasonic imaging apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a system block diagram of an ultrasonic imaging apparatus according to an embodiment, and FIG. 2 is a diagram showing a structure of a probe of the ultrasonic imaging apparatus.

As shown in FIG. 2, the probe 10 according to this embodiment has a plurality of piezoelectric elements arranged in a plane lattice, and a piezoelectric element forming a transmitting element 12T in each matrix direction and a receiving element 1.
A transmission switching unit 16 in which the piezoelectric elements forming 4R are alternately arranged and the transmission switching operation is performed in units of the transmission element groups 12 arranged in each column, and the reception element group 1 arranged in each row
The reception switcher 18 performs the reception switching operation in units of four. In the figure, the white element is used as the transmitting element 12T and the hatching element is used as the receiving element 14R, so as to collectively transmit and receive for each column and row. As shown in FIG. 4, the plurality of transmitting piezoelectric elements 12T corresponding to each column or the plurality of piezoelectric elements 14R corresponding to each row are connected in parallel so that they operate as one block. The switching devices 16 and 18 are operated. By arranging in this way, each element becomes smaller in the case of a two-dimensional array, so the impedance of each element, which will inevitably become larger, is bundled and maintained at an appropriate value. It can solve the problem of loss of signal and signal strength at the same time. The reduction of impedance due to parallel connection, the increase of signal strength, and the restoration of directivity due to the one-dimensional array are important for realizing the device.

As described above, since the transmission and reception one-dimensional arrays are orthogonal to each other, the data at the intersection can be obtained.
By scanning the transmitting columns and the receiving rows, data can be collected at all points on the array plane. However, this is just above the transducer,
The radiated waves from the one-dimensional array spread laterally in a fan shape, forming a cylindrical wavefront. The reception is the same, and as a result, FIG.
As shown in, the region O-p1-p2- where two partial cylinders intersect
p3-p4 is the detection area. When the piezoelectric element has a square shape in a plane and a size of about a half wavelength, there is almost no directivity in the lateral direction with respect to the axis of the one-dimensional array, so that a decent image cannot be expected. Therefore, it is necessary to converge the data obtained by using the probe 10.

Now, assume that image data is obtained by the probe 10 using one of the one-dimensional array element groups parallel to the X and Y axes for transmission and the other for reception as described above. . The principle of the method of focusing the image at this time is as follows.

For example, the point Q (ξ, η,
ζ) is a point on the ultrasonic reflector (target). The distance between this point Q and the X axis is ρ ₁ , and the distance between the Y axis is ρ ₂ . Ultrasonic waves radiated in the same phase from the piezoelectric element rows arranged at equal intervals on the X axis can be represented as follows using a cylindrical coordinate system having the X axis as the rotation axis.

The amplitude of the ultrasonic wave is Φ (x, y, z, t), and Fourier transform is performed in time as in [Equation 1].

[Equation 1]

Here, ω is the angular frequency, and ω = ck. c is the speed of sound and k is the wave number.

[Equation 2]

This equation is as follows in a cylindrical coordinate system where z ₀ is the axial direction to which the piezoelectric elements are coupled, r is the distance from the axis, and θ is the rotational direction.

[Equation 3]

The solution of this equation is assumed to have the following form that does not depend on z ₀ .

[Equation 4] At this time, Q (r) satisfies the following equation.

[Equation 5]

This equation can be expressed as follows using the Hankel function.

[Equation 6]

Here, the Hankel function can be gradually expanded as follows.

[Equation 7]

[Equation 8]

The ultrasonic signal radiated from the X-axis, reflected by the object, and received by the Y-axis is expressed as follows, where ε (ξ, η, ζ) is the reflectance per unit volume in the object. Can be expressed as

[Equation 9]

Applying the equation of the gradual expansion to the above equation,

[Equation 10]

When this equation is inversely Fourier transformed with respect to the wave number k,

[Equation 11]

In [Equation 11], the phase factor exp {{ik
It can be seen that (ρ ₁ + ρ ₂ −ct)} is important for reconstructing the image. Based on this, the following procedure is used as a visualization algorithm. Surface of the probe 10 (X
It is assumed that there is a transmitting piezoelectric element array on one axis (parallel to the X axis) on the Y plane and another receiving piezoelectric element array on another axis (parallel to the Y axis).

The ultrasonic wave is emitted from the set ultrasonic wave transmission point P ₁ (ξ, y, z) and received by the receiving piezoelectric element P ₂ (x, η, z). In this case, the reflected wave from the reflection point Q (ξ, η, ζ) inside the object can be written as follows if there is no attenuation of the ultrasonic wave.

[Equation 12]

Here, r _i , t _i , and w (t) are the reflection coefficient, the round-trip time to the reflection point of the ultrasonic wave, and the ultrasonic pulse waveform, respectively. There is a time delay t _i corresponding to the distance to each reflection point in the object. Here, the reflection coefficient is ξ in FIG.
It depends on η and ζ. Such time series data is x,
Only the number corresponding to the degree of freedom of y is measured.

To reconstruct the image, in FIG.
Without P₁(Point on the axis parallel to the X axis), P₂(Axis parallel to Y-axis
Select the upper point) and the point Q. Five independent variables are included in this selection.
There are degrees of freedom corresponding to the numbers (x, y, ξ, η, ζ). So
And choose specific values for these five independent variables
Ultrasound measured as reflected waves for each pair when
Corresponding time series data ψ (t) of the waves. So super
Sound wave propagation path (P ₁→ Q → P₂) Corresponding measurement time series wave
The reflection amplitude at point Q from the shape ψ (t) is required for this propagation.
The required time is calculated and obtained and assigned to the point Q. 5 above
If you perform this operation for each independent variable of
For the reflection point Q that does not exist, the reflection amplitude cannot be obtained, and the inspection
For the reflection point Q where the object exists, the reflection amplitude can be obtained.
It Therefore, the numerical value of the reflection amplitude assigned to each point
The image can be reconstructed by adding each point between (imaging target)
Wear. Specifically, the following formula is used.

The position of the transmitting piezoelectric element is (ξ, y, z),
The position of the receiving piezoelectric element is (x, η, z), and the point Q in the medium is
Let (ξ, η, ζ) be

[Equation 13] Just ask

The three-dimensional ultrasonic imaging apparatus according to the embodiment for performing such processing is configured as follows. As shown in FIG. 2, the sensor head of the probe 10 has a multi-cross linear array piezoelectric element arrangement having a planar structure.
At this time, a characteristic is that a three-dimensional image can be obtained without moving the sensor head as shown below.

As shown in the block diagram of the entire apparatus in FIG. 1, the ultrasonic imaging apparatus according to the embodiment is a probe 1 having a multiple cross linear ray structure of the circuit configuration shown in FIG.
Has 0. The probe 10 has a plurality of piezoelectric elements arranged in a plane lattice, and piezoelectric elements forming the power transmitting elements 12T and piezoelectric elements forming the receiving element 14R are alternately arranged in each matrix direction. In the probe 10 in which a large number of piezoelectric elements are arranged in this way, a transmission switching device (pulse switching circuit) 16 for performing transmission switching operation in units of the transmission element groups 12 arranged in each column (or each row) is provided. And again
A reception switcher (reception switching circuit) 18 for performing reception switching operation in units of the reception element groups 14 arranged in each row (or each column) is provided. Further, the transmission switch 16 that switches the transmission element group 12 in column units and the reception switch 18 that switches the reception element group 14 in row units are the control circuit 26.
Each column is controlled to be switched to each column and each row is sequentially controlled so that the intersection of the selected transmission column and reception column becomes the detection target area at the time of selection. The signal line of such a probe 10 is a two-dimensional array (N
XN), there are a total of 2N transmission N lines and reception N lines, and these terminals are located on the outer periphery of the array. The signal control circuit portion of the control circuit 26 outputs signals for sequentially selecting the columns or rows to SPNT (Single).
It is sent to the transmission switch 16 and the reception switch 18, which are PortN Transfer) switches. This SPN
In the case of the switch 16 for transmission, the T switch is composed of, for example, a power FET because the power of the signal from the high-voltage pulse transmission circuit 38 is large. It can be configured with a FET switch or the like. The reception signal switched by the reception switch 18 is amplified by the high-frequency receiving circuit 28, which is a high-sensitivity amplifier, and sent to the A / D converter 30. The role of the control circuit 16 is
The switch control and the timing control for A / D converting the signal are mainly used. FIG. 6 shows an example of an actual wiring pattern in the probe 10, in which a transmission signal line pattern 22, a reception signal line pattern 24, and an earth pattern (not shown) are provided on a substrate 20 having a three-layer structure, and each piezoelectric element (12T). ,
The ground side of 14R) is a common ground.

A high voltage pulse generation circuit 38 is connected to the transmission switching device (pulse switching circuit) 16 so that ultrasonic waves are emitted as pulses from the transmission element group 12 in the selected row. An industrial high-speed, high-voltage FET may be used for the high-voltage pulse generation circuit 38, and a pulse voltage up to about 50 V and 10 MHz can be generated by controlling the gate of the FET. Further, the reflection signal detected by the receiving element group 14 in the row selected by the reception switching device (reception switching circuit) 18 is
The signal is input from the high frequency receiving circuit 28 to the control circuit 26 via the A / D converter 30.

In the three-dimensional ultrasonic imaging apparatus according to the embodiment, the control circuit 26 has a transmission switching circuit (pulse switching circuit) 1
A switching control signal is output to 6 and the reception switching circuit 18, and a control signal is output to the high voltage pulse transmission circuit 38 to generate a transmission pulse. That is, the transmission switching circuit 16
On the basis of the switching control signal from the control circuit 26, for example, the transmission piezoelectric element group 12 in the first column of the probe 10 is connected to the high-voltage pulse transmission circuit 38. Then, the control circuit 26
Supplies a control signal to the high voltage pulse transmission circuit 38 in synchronization with the switching of the transmission piezoelectric element group 12 to generate a high voltage pulse. As a result, the transmission piezoelectric element group 12 in the first column receives the pulse output from the high-voltage pulse transmission circuit 38 and radiates an ultrasonic pulse of a predetermined frequency into the air, water, or an object to be inspected. . In addition, the control circuit 2
6 outputs the ultrasonic pulse to the transmitting piezoelectric element group 12 in the first column, the probe 10 is transmitted through the reception switching circuit 18.
The receiving piezoelectric elements 14R are sequentially switched and connected to the high frequency receiving circuit 28. The switching of the receiving piezoelectric element 14R is performed for each row of the probe 10.

That is, when the transmitting piezoelectric element group 12 in the first column emits an ultrasonic pulse, the control circuit 26 causes the receiving piezoelectric element group 14 in the first row and the receiving piezoelectric element in the second row. Group 14, ..., which is sequentially switched to the receiving piezoelectric element group 14 in the Nth row and connected to the high-frequency receiving circuit 28, and which is generated by reflected waves of ultrasonic waves emitted from the transmitting piezoelectric element group 12 in the first column. The received signal is input to the high frequency receiving circuit 28. Then, when the control circuit 26 finishes switching the reception piezoelectric element group 14 from the first row to the Nth row, the transmission switching circuit 16
To the high voltage pulse transmission circuit 38 to connect the piezoelectric element group 12 for transmission on the second row to the high voltage pulse transmission circuit 38, and to transmit the piezoelectric element group 12 for transmission on the second row. Element group 1
The ultrasonic pulse is emitted from 2, and the receiving piezoelectric element group 14 is sequentially switched from the first row to the Nth row via the reception switching circuit 18 and connected to the high-frequency receiving circuit 28.

In this way, the control circuit 26 sequentially switches the piezoelectric element groups 12 for transmission from the first column to the Nth column and connects them to the high-voltage pulse transmission circuit 38 to drive them, and at the same time, receives the piezoelectric elements for reception. The element group 14 is sequentially switched from the first row to the Nth row and connected to the high frequency receiving circuit. The switching operation of the probe 10 may be reversed for the transmission piezoelectric element group 12 and the reception piezoelectric element group 14.

The signal thus received by the receiving piezoelectric element group 14 is output to the sensor image processing circuit 32 via the reception switching circuit, where the three-dimensional image processing is performed. Then, the sensor image processing circuit 3
The image data obtained by 2 is output to the display device 34 via the control circuit 26 and displayed as a three-dimensional image.

The specific processing in the sensor image processing circuit 32 is as follows. The probe 10 has a multi-cross linear array structure. As shown in FIG. 3, in the case of a single-row array, ultrasonic waves spread in the direction orthogonal to the axial direction of the array and the directivity deteriorates. Since this can be applied to both the orthogonal transmission and reception, the intersection area of the fan-shaped pillars is the simultaneous detection area as indicated by P1, P2, P3, and P4 in FIG. As can be seen from the figure, if this is left as it is, the detection area becomes large due to the spread of the beam, resulting in a blurred image.
Therefore, the processing method for correcting this image blur and reproducing it to a correct converged image is as described above.

As described above, in the present embodiment, the probe having the structure of the multiple cross linear array, the system incorporating the circuit for driving the probe, and the sensor image processing circuit from the ultrasonic wave reception signal obtained by using them. It is possible to obtain a three-dimensional image of the object by converging the blur of the image by the image reproducing algorithm installed in the.

[0043]

As described above, according to the present invention, by connecting each row and each column of piezoelectric elements arranged in a plane lattice, one of the rows or columns is used for transmission and the other is used for reception. And a transmitting element group and a receiving element group are arranged in rows,
A configuration including switching means for switching to each column, and processing means for reproducing a three-dimensional image based on an image reproduction calculation formula from an ultrasonic wave reception signal obtained by the receiving element group every switching processing by the switching means. Therefore, firstly, a real-time 3D image device that does not require mechanical scanning can be realized,
Also, the wiring of the electronic circuit is drastically reduced, so that the configuration can be made very inexpensively.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a real-time 3D image device according to an embodiment.

FIG. 2 is a layout diagram of a probe for an ultrasonic imaging apparatus according to an embodiment.

FIG. 3 is an explanatory diagram of a beam shape and a detection region of the probe according to the embodiment.

FIG. 4 is an explanatory diagram of a method of connecting piezoelectric elements forming rows or columns of the probe according to the embodiment.

FIG. 5 is a diagram illustrating the principle of three-dimensional image display.

FIG. 6 is an explanatory diagram of a wiring pattern of the probe.

FIG. 7 is a basic configuration diagram of a general ultrasonic imaging apparatus.

FIG. 8 is a principle diagram of electron focusing of a probe using a piezoelectric element.

[Explanation of symbols]

10 ... Probe, 12T ... Piezoelectric element for transmission, 14
R ......... Reception piezoelectric element, 16 ......... Transmission switch, 18
……… Reception switch, 26 ……… Control circuit, 28 ……… High frequency receiving circuit, 32 ……… Sensor image processing circuit, 34…
...... Display device, 38 ………… High voltage pulse generation circuit.

Continued front page    (72) Inventor Takayoshi Yumi             Mitsui Shipbuilding, 3-1-1 Tamama, Tamano City, Okayama Prefecture             Tamano Works Co., Ltd. F term (reference) 2F068 AA40 DD02 FF12 FF14 GG01                       KK13 KK17 KK18 LL04 PP05                       QQ42 QQ44 RR02                 2G047 AC13 BC07 CA01 EA16 GB02                       GB17 GF01 GF06 GF15 GG09                       GH07 GH08 GH09                 4C301 AA03 BB02 BB13 BB19 BB22                       EE10 EE17 GB09 HH17 KK16                 5D019 AA06 BB19

Claims (2)

[Claims] 1. A two-dimensional structure in which piezoelectric elements corresponding to each row and each column of piezoelectric elements arranged in a plane lattice are coupled so that one of the rows or columns is for transmission and the other is for reception. A linear array is provided, and a switching device that switches between the transmitting element group and the receiving element group in units of rows and columns is formed to form a probe having a video area in front of the matrix intersection, and switching processing by the switching unit is performed. A real-time three-dimensional ultrasonic imaging apparatus comprising processing means for reproducing a three-dimensional image of an object to be imaged from measurement data obtained by the receiving element group for each. 2. A plurality of piezoelectric elements are arranged in a plane lattice, and piezoelectric elements forming a transmitting element and piezoelectric elements forming a receiving element are alternately arranged in each matrix direction, and arranged in each column (or each row). And a reception switcher for performing a reception switching operation for each receiving element group arranged in each row (or each column). A probe for an ultrasonic imaging device.