JPH04347144A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

PURPOSE:To achieve a simplification of a phasing section which performs a phase matching in transmission and reception with a structure of a three- dimensional scanning along with a reduction in the number of signal lines and moreover, a handy acquisition of a three-dimensional image with the possibility of a three-dimensional photography by arranging a probe to perform a three- dimensional scanning of an ultrasonic beam without use of a two-dimensional array probe in an ultrasonic diagnostic apparatus. CONSTITUTION:This apparatus includes an ultrasonic probe in which a transmitter/receiver 17 is arranged in a strip and transmits a sound wave in the direction corresponding to a frequency used to receive the reflected wave thereof and a delay means (transmission pulse generator 13 or transmission delay circuit 12) for performing a sector scanning and a focusing in the direction of the strip array. Then, a sector scanning is performed changing center frequency in a way orthogonal to the direction of the strip array. This enables the performing of a three-dimensional beam scanning using a one-dimensional array in electric pole thereby suppressing increase in the number of signal lines and in the sizes of circuits.

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 an imaging method capable of three-dimensional scanning and a probe used for three-dimensional imaging.

0002

2. Description of the Related Art Conventionally, a method of scanning a beam in three dimensions uses two-dimensional array probes arranged in the x and y directions, as described in Japanese Patent Application Laid-Open No. 62-4988. There is a configuration in which a signal line is drawn out from each element and a delay line is provided in almost all the transducers in order to form a beam in either the x direction or the y direction. In addition, a typical two-dimensional array probe is described in ``Basic Study of Matrix Array Transducer, Proceedings of the 47th Japanese Society of Ultrasonics in Medicine (November 1985)''. There are probes made of divided PZT. This is two-dimensionally divided by a matrix of grooves. In addition, as described in "High-speed two-dimensional imaging device, Proceedings of the 36th Japanese Society of Ultrasonics in Medicine (November 1970)," the applicants have proposed a wave transmitter that sends out sound waves in a direction corresponding to the driving frequency. In this transmitter, as shown in FIG. 2(a), ultrasonic waves are emitted in a direction according to the frequency by driving an array vibrator with reverse polarization by frequency sweeping. Further, the relationship between the angle Θ of emitting ultrasonic waves and the drive frequency f is shown in (b). Note that the radiation angle Θ is given by the following equation, where d is the recoil polarization pitch of the vibrator, f is the driving frequency, and λ is the wavelength.

##EQU00001## Further, the far-field sound field directivity characteristic R(Θ) at that time is given by the following equation.

[Math 2] This relationship is used to scan the beam.

0003

[Problem to be solved by the invention] In the above conventional technology, two
When using a dimensional array, for example, an n×n matrix, n×n signal lines are required, and as the number of signal lines increases, the phasing section also increases. For this reason, there was a problem in increasing the scale when realizing the device. Furthermore, there is no mention of a two-dimensional array of transmitters that transmit sound waves in a direction corresponding to the driving frequency, and no method of three-dimensional beam scanning is presented. The purpose of the present invention is to improve such problems,
By constructing a probe that scans the ultrasound beam three-dimensionally without using a two-dimensional array probe, the number of signal lines of the probe is reduced, and the phasing section that adjusts the phase of transmission and reception is simplified. The purpose of the present invention is to provide an ultrasonic diagnostic device that can perform Also, 3
An object of the present invention is to provide an ultrasonic diagnostic method capable of performing dimensional imaging and easily obtaining a three-dimensional image.

0004

[Means for Solving the Problems] In order to achieve the above object, the ultrasonic diagnostic apparatus of the present invention includes a transducer that transmits ultrasonic waves in a direction corresponding to the frequency used and receives reflected waves from a subject. an ultrasonic probe configured by arranging them in a rectangular shape, and means for electronic scanning and focusing in the direction of the rectangular array (wave transmission pulse generator, wave transmission delay circuit, etc.), It is characterized by electronic scanning by changing the center frequency in the direction of scanning. In addition, the above-mentioned ultrasonic probe has a means for achieving acoustic matching with the subject on the front surface of the transducer (acoustic matching layer), a means for supporting the transducer on the rear surface (backing material), and means for absorbing ultrasonic waves (ultrasonic absorber) other than the ultrasonic wave absorber, and the transducer/receiver is arranged so that the surface of the transducer is inclined in a direction perpendicular to the direction in which the rectangular strips are arranged, with respect to the ultrasonic emission surface, A distinctive feature is that the transducer is constructed from an array of regularly spaced polarization-inverted array transducers. Further, in the ultrasound diagnostic method of the present invention, images of a subject are captured from two directions using the ultrasound probe that performs three-dimensional scanning using an ultrasound beam, and each probe is displayed on a display screen corresponding to those directions. The feature is that it displays an emmeber image obtained from the front view. Further, the three-dimensional imaging device of the present invention is characterized in that it is equipped with the above-mentioned probe and performs software processing on the three-dimensional data obtained by the above-described method to display pixels and shadows.

[0005]

[Operation] In the present invention, an ultrasonic probe is used, which is constructed by arranging transducers in a strip shape that transmit sound waves in the direction corresponding to the frequency used and receive the reflected waves. In the direction orthogonal to the direction, sector scanning is performed by changing the center frequency, and the frequency is swept before and after the center frequency. This allows the number of delay lines to be reduced compared to the conventional method. Furthermore, by mixing drive signals having phase information, it is possible to form the same beam as the transmitted wave. Furthermore, by displaying stereoscopic images viewed from two directions, a three-dimensional image due to parallax can be easily obtained.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 3 is a perspective view showing the general appearance of the probe in the first embodiment of the present invention, FIG. 4 is a configuration diagram of the probe in the first embodiment of the present invention, and FIG. FIG. 3 is an explanatory diagram of the beam scanning direction in the embodiment. First, the configuration of the probe and beam scanning used in the ultrasonic diagnostic apparatus of this embodiment will be described. In FIG. 3, 17 is a rectangular transducer;
32 is a signal line, and the arrow inside the element of the transducer 17 indicates the polarization direction. Further, in FIG. 4, 41 is a probe, 42 is an ultrasonic absorber, 43 is a ground wire, and 44 is a backing material. The probe 41 of this embodiment has a structure in which rectangular transducers 17 are arranged side by side. Therefore, the signal line 32
The signal electrode for connecting is cut into strips,
The opposite surface is commonly connected to a ground line 43. The upper surface of the probe 41 is an ultrasonic wave transmission surface, and the transducer 17 is installed at 45 degrees with respect to the radiation surface. Also,
The transducer 17 is supported by a backing material 44, the signal line 32 is guided by a flexible cable, etc., and the ground line 4
3 is derived in the same way. Furthermore, the ultrasonic absorber 42 is for absorbing unnecessary ultrasonic waves emitted to the object across the ultrasonic irradiation direction and the normal line to the transducer 17. In this embodiment, the ultrasonic absorber 42 has a straight line, but it is also conceivable to configure it as a curved surface to prevent ultrasonic waves from entering the transducer 17 in unnecessary directions. Further, the installation angle of the transducer 17 is not limited to 45°. Furthermore, several acoustic matching layers may be provided on the front surface of the transducer 17. Further, as a method of manufacturing the probe 41, there is a method of arranging piezoelectric bodies so that the polarization directions are different. Furthermore, if a highly anisotropic material (for example, lead titanate) is used, polarization inversion can be formed without cutting the electrode pattern. In addition, polarization inversion can be formed by the pattern of electrodes in the polymer piezoelectric material. Furthermore, an array of ferroelectric films constructed by sputtering technology and composite piezoelectric materials can also be used. With such a configuration, the beam can be scanned to any point as shown in FIG. Note that FIG. 5 shows a beam scanning shape, and 51 is a scanning plane. In this embodiment, when one transducer 17 is driven with pulse waves of a plurality of wave numbers having a driving frequency f, ultrasonic waves are emitted at an angle in the y direction corresponding to the frequency. For example, as shown in FIG. 4, the transducer 17 is installed at an angle of 45° in the y direction with respect to the radiation surface, and the polarization inversion pitch of the transducer 17 is set to 0.43 mm in a medium with a sound velocity of 1500 m/s. , drive frequency 3.5M
When the frequency is Hz to 2.0 MHz, the probe surface is scanned by approximately ±15° in the y direction. Furthermore, by shifting the phase of the drive wave between each element, beam scanning in the x direction can be performed. Furthermore, by applying a delay between the elements in the x direction and matching the phases, it is possible to scan the beam at a desired angle in the x direction and focus it on a desired point.

Next, the transmission/reception processing section will be described. Figure 1
6 is a block diagram showing a transmission/reception processing section of an ultrasonic diagnostic apparatus according to a first embodiment of the present invention, and FIG. 6 is an explanatory diagram of a transmitted pulse in the x direction according to the first embodiment of the present invention. In FIG. 1, 11 is a transmission pulse generator, 12 is a transmission delay circuit,
13 is a drive circuit, 14 is an adder circuit, 15 is a reception delay circuit, 16 is a transmission/reception separation circuit, and 17 is a transceiver, and these constitute a transmission/reception processing section. In this embodiment, the transmission pulse generator 11 outputs pulses of a plurality of wave numbers at a frequency that determines the scanning angle in the y direction, the transmission delay circuit 12 gives a phase in the x direction, and the drive circuit 13 transmits and receives pulses. The wave device 17 is driven to emit ultrasonic waves. The reflected echoes from the object are received by the same transmitter/receiver 17, guided by the transmitter/receiver separation circuit 16 to the reception delay circuit 15 for phase matching, and added by the adder circuit 14.
This becomes a raster signal corresponding to one scanning direction. Note that a preamplifier may be provided before the reception delay circuit 15. Further, for all raster signals, good images can be obtained by setting the band characteristics of the reception processing unit including the transducer in the frequency range used so that the same intensity is obtained in the depth direction for the same reflector. With this configuration, signals arranged in the x direction applied to the transducer 17 are shown in FIG. That is, the transmission pulse 61 is transmitted through the transmission delay circuit 12.
The beam is delayed by and applied to the transducer 17 to scan and focus the beam in a desired direction. This transmission pulse 61 is a pulse with a plurality of wave numbers (n/2),
Scanning in the y direction is performed by changing this frequency. In addition to the method of keeping the frequency constant in the same pulse,
There is also a method of focusing in the y direction by using this pulse as a chirp signal. Furthermore, by using pulse compression technology, the S/N and distance resolution can be improved. this is,
This can be achieved by providing a distributed delay line after addition. In addition to the method of performing reception processing as an analog signal,
There is also a method of performing /D conversion and digital signal processing. Furthermore, the received digital signal is digitally phase-aligned,
It can also be processed by frequency analysis.

Next, another embodiment of the transmission/reception processing section in the ultrasonic diagnostic apparatus will be described. Note that the configuration of the probe of this embodiment is the same as that of the first embodiment. FIG. 7 is a block diagram of a transmission/reception processing section in a second embodiment of the present invention, FIG. 8 is a block diagram of a transmission pulse generation section in a second embodiment of the present invention, and FIG. 9 is a block diagram of a transmission/reception processing section in a second embodiment of the present invention. FIG. 10 is a block diagram of the reception processing unit in the second embodiment of the present invention, and FIG. 11 is a block diagram of the transmission pulse generator in the embodiment. FIG. 5 is a timing chart showing reading. In FIG. 7, 71 is a transmission pulse generator, 72 is a reference signal generator, and 73 is a mixer. In this example, a transmission pulse is output from the transmission pulse generator 71, and the drive circuit 13 outputs the transmission pulse to the transducer 17.
is driven, and ultrasonic waves are emitted. Then, the echo from the subject is guided to the reception processing section by the transmission/reception separation circuit 16, and mixed with the reference signal from the reference signal generator 72 by the mixer 73. This reference signal is a continuous repetition of the transmission pulses that drove each vibrator. Furthermore, since the reference signal has a phase for each channel, the frequency is shifted and the phase is matched, forming a beam at the same point as the transmitted wave. Further, the transmission pulse generation section 71 includes a transmission pulse generator 81 and a multiplexer 82, as shown in FIG. Thereby, the pulses stored in advance are read out by the transmission pulse generator 81, and the desired transmission pulses are applied to each vibrator by the multiplexer 82. Furthermore, as shown in FIG. 9, the transmission pulse generator 81 includes a storage element 91, a D/A converter 92, a filter 9
3, and a control section 94. In this example,
When generating a transmission pulse, various transmission pulse patterns (including frequency and phase) are stored in the storage element 91, and the control unit 94 generates a transmission pattern according to the beam scanning direction and focus point. Read according to the instructions of D/
An analog transmission pattern is obtained by the A converter 92 and filter 93. Therefore, this circuit will be lined up in the largest diameter channel. Alternatively, it is also possible to use the memory element 91 in common for each transducer and switch to each channel using the multiplexer 82. Further, the detailed configuration of the reception processing section of this embodiment is shown in FIG. In FIG. 10, 101
is an A/D converter, and 102 is a storage element. In this embodiment, for example, when the transmission signal for focusing in the y direction is a chirp signal, the signal received from the transducer 17 is received by the transmission/reception separation circuit 16 as shown in FIGS. 10 and 11. A memory element 102 guided into the circuit and digitized by an A/D converter 101 at a sampling period Ts.
are stored sequentially. In this case, the transmission pulse width is m×Ts
Then, m storage elements are required. Further, readout is performed at Tr=Ts/m, where readout time Tr is taken, and analog conversion is performed by the D/A converter 92 and filter 93. On the other hand, the transmission signal is similarly compressed by 1/m by the reference signal generator 72 and repeated at the sampling period. These signals are mixed by a mixer 73 to perform frequency shifting and phase matching. Note that in the memory element 102, Ts is also a data shift period between memory elements. Describing this data flow, the received signal is Ts
The sampled data is stored as digital data at address 1 of the storage element 102. And 1 at 2Ts
The data at address is transferred to address 2, and new data is stored at address 1. This operation is repeated sequentially, and when m×Ts,
Data is collected from addresses 1 to m. Here, data is read from m to 1 at a cycle of Ts/m, and the data is further shifted to store new data at (m+1)Ts at address 1. At this point, a signal obtained by compressing the transmission signal to 1/m is obtained, so the reference signal to be mixed is also compressed to 1/m and mixed. Repeat this action. In this embodiment, the storage element is a digital element and the mixing operation is performed using an analog signal, but the mixing operation may be performed entirely digitally or vice versa. Alternatively, by using a RAM or the like as a storage element, it is also possible to perform only address designation without shift scanning. Furthermore, in this embodiment, when generating a transmission pulse, the transmission pulse generator 81 reads out a pulse stored in advance, but the transmission pulse generator 81 generates a transmission pulse with each phase. It is also possible to do this.

Next, a three-dimensional imaging method using the ultrasonic diagnostic apparatus of the above embodiment will be described. This is the 3rd part of the test subject.
After obtaining dimensional data, voxel display, shading display, wire frame display, etc. are performed by software processing. FIG. 12 is an explanatory diagram of a three-dimensional imaging method in the third embodiment of the present invention. In FIG. 12, 17a and 17b are transducers, 120 is a subject, 121a and 121b are reception processing units, 122a and 122b are displays, and 123 is an operator, viewed from the y direction in which the ultrasound beam is scanned by frequency sweep. It is something that Moreover, the transducer 17a, 1
7b and the reception processing units 121a and 121b have the same configuration as in the first or second embodiment. In this embodiment, two transducers are arranged, and the object 120 is scanned.
Display images for each probe 122a, 122
b while maintaining the left-right relationship. When the operator 123 views this image with both eyes, it appears three-dimensional due to the parallax. Further, the displays 122a and 122b display the y-direction of the probe in the horizontal direction, the x-direction in the vertical direction, and display a front view. Further, as data, the integral value of each raster is used, or alternatively, a normal tomographic image is displayed first, Roy is set, and the integral value of the raster is used. Alternatively, the surface of the subject 120 may be detected and displayed. Note that although the probes shown in FIGS. 3 and 4 were used in this embodiment, three-dimensional imaging can also be achieved using a normal two-dimensional array probe. Further, this embodiment can also be applied to a system that moves in diameter. Furthermore, although the present embodiment uses an equally spaced inverted polarization array, a coded probe such as M-sequence or Barker code may also be used. Furthermore, according to the present embodiment, since the frequency is swept, it is also possible to analyze the attenuation characteristics of the subject at different frequencies.

0010

According to the present invention, the beam can be scanned three-dimensionally with the same number of signal lines without changing the beam scanning method of the conventional electronically scanned array. This has the effect of suppressing an increase in the number of signal lines to be driven and an increase in circuit scale. Furthermore, a three-dimensional image can be easily obtained by displaying stereoscopic images from two directions.

[0011]

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a transmission/reception processing section of an ultrasonic diagnostic apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the principle of a conventional ultrasonic diagnostic transmitter.

FIG. 3 is a perspective view showing the general appearance of a probe in the first embodiment of the present invention.

FIG. 4 is a configuration diagram of a probe in the first embodiment of the present invention.

FIG. 5 is an explanatory diagram of the beam scanning direction in the first embodiment of the present invention.

FIG. 6 is an explanatory diagram of a transmission pulse in the x direction in the first embodiment of the present invention.

FIG. 7 is a configuration diagram of a transmission/reception processing section in a second embodiment of the present invention.

FIG. 8 is a configuration diagram of a transmission pulse generation section in a second embodiment of the present invention.

FIG. 9 is a configuration diagram of a transmission pulse generator in a second embodiment of the present invention.

FIG. 10 is a configuration diagram of a reception processing section in a second embodiment of the present invention.

FIG. 11 is a timing chart showing writing and reading of a memory element during reception in a second embodiment of the present invention.

FIG. 12 is an explanatory diagram of a three-dimensional imaging method in a third embodiment of the present invention.

[Explanation of symbols]

11 Transmission pulse generator 12 Transmission delay circuit 13 Drive circuit 14 Adder circuit 15 Reception delay circuit 16 Transmission/reception separation circuit 17 Transducer/receiver 17a Transducer/receiver 17b Transducer/receiver 32 Signal line 41 Probe 42 Ultrasonic absorber 43 Ground line 44 Backing material 61 Transmission pulse 71 Transmission pulse generation section 72 Reference signal generation section 73 Mixer 81 Transmission pulse generator 82 Multiplexer 91 Memory element 92 D/A converter 93 Filter 94 Control section 101 A/D converter 102 Memory element 120 Subject 121a Reception processing unit 121b Reception processing unit 122a Display 122b Display 123 Operator

Claims (6)

[Claims] Claim 1: An ultrasonic diagnostic device that transmits ultrasonic waves and receives and displays reflected waves from a subject. An ultrasonic probe characterized by receiving transducers arranged in a strip shape. 2. The ultrasonic probe according to claim 1, wherein the transducer is composed of an equally spaced polarization-inverted array transducer. 3. Means for achieving acoustic matching with the subject on the front surface of the transducer, means for supporting the transducer on the rear surface of the transducer, and means for absorbing ultrasonic waves in directions other than the target direction. 2. The ultrasonic probe according to claim 1, wherein the transducer is arranged so that the surface of the transducer is inclined with respect to the ultrasonic emission surface in a direction perpendicular to the direction in which the strips are arranged. . 4. An ultrasonic diagnostic device that transmits ultrasonic waves and receives and displays reflected waves from a subject, in which the ultrasonic waves are transmitted in a direction corresponding to the frequency used and the reflected waves from the subject are detected. It is equipped with an ultrasonic probe configured by arranging receiving transducers in a rectangular shape, and a means for electronic scanning and focusing in the direction in which the rectangular array is arranged, and a center frequency in a direction perpendicular to the rectangular direction. An ultrasonic diagnostic device characterized by electronic scanning. 5. A three-dimensional imaging device comprising the probe according to claim 1. 6. An ultrasonic diagnostic method for transmitting ultrasonic waves and receiving and displaying reflected waves from a subject, comprising an ultrasonic probe that performs three-dimensional scanning with an ultrasonic beam; An ultrasonic diagnostic method comprising: imaging a subject from two directions using a probe, and displaying normal images obtained from the probe on display screens corresponding to both directions.