JPS59105444A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to a technology for an ultrasonic diagnostic device that obtains biological information by emitting ultrasonic waves into a living body and detecting reflected signals of the ultrasonic waves from inside the living body. Belongs to a field.

[Technical background of the invention and its problems]

Conventionally, in ultrasonic diagnostic equipment that displays the entire tomographic image of a living body using an LD based on the reflected signals obtained by scanning the inside of a living body with an ultrasound beam, when the number of scanning lines is increased to improve image quality, the number of frames decreases and real-time As a proposal to solve the problem of lack of quality, there is an invention described in Japanese Patent Publication No. 20017 of 1981.

The invention provides, for example, #1 to #6 as shown in FIG.
For the ultrasonic beam T1 emitted by exciting the micro ultrasonic transducers 1 #1 to #5 of the micro ultrasonic transducers 1 up to By simultaneously receiving the reflected echoes with #1 to #6 micro ultrasonic transducers 1 whose receiving directivity is R2, ultrasonic waves from two different directions whose total transmitting and receiving directivity is TR1 direction and TR2 direction are detected. Assume that the sound wave reflection signals can be obtained simultaneously.

However, in the above invention, consideration is not given to the difference in beam sensitivity and the half-width (width of the ultrasonic beam at -6 dB) in parallel reception.
The peak sensitivity difference causes a striped pattern on the tomographic image, degrading the image quality. Conversely, when the sensitivity difference is corrected, the background noise level causes the striped pattern. FIG. 2 shows specific calculation results of the sound field characteristics in the invention. The calculation conditions are: a linear scanning ultrasonic diagnostic device, the pitch of the micro-oscillator is i, 5 m, and the frequency is 6.5.
1! az, the focal point is 50H1, the number of transmitting oscillators is 8, and the number of receiving oscillators is 8 and 9. In Figure 2,
5 is the transmission directional characteristic due to eight oscillators,
The receiving directivity characteristics of the same eight transducers are also similar to this. On the other hand, 6 shows the receiving directivity characteristic of two transducers, which are eight transmitting transducers plus one adjacent transducer, and the sensitivity at the peak is only 0.8 dB compared to the eight transducers. thicker than the peak sensitivity. When the same eight transducers are used for transmission and reception, the overall directivity characteristics for transmission and reception are broken [7
In addition, when there are eight transducers for transmitting and nine transducers for receiving, the overall directivity characteristic of transmitting and receiving is indicated by broken a8. As is clear from Figure 2, the peak sensitivity difference is 4.5
With dB-C, the difference in half width is 1, 2-1l vs. 0.86M
There is a difference of approximately 30%.

By the way, human vision is extremely sensitive, and normally, in order to make the difference in gradation on the display unrecognizable, it is necessary to suppress it to one gradation among 62 gradations or less.

In a normal ultrasonic diagnostic apparatus, the dynamic range is set to 50 to 40 dE, and this is displayed at f:62 gradation level. Therefore, in order to make the gradation difference unrecognizable, the peak sensitivity difference' for a dynamic range of 50 dB K
1.64B or less, dynamic range 4 Q dB
However, it is necessary to suppress the peak sensitivity difference to t1.34B or less. Then, 4. as shown in Figure 2.
A peak sensitivity difference of 5 dB is clearly recognized and experimentally confirmed as a striped pattern on a tomographic image.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and is aimed at improving the peak sensitivity difference and half-width in an ultrasound diagnostic apparatus that employs a simultaneous parallel reception method that increases the number of scanning lines of ultrasound beams without impairing real-time performance. It is an object of the present invention to provide an ultrasonic diagnostic apparatus that displays high-quality images by completely reducing differences.

[Summary of the invention]

The outline of the present invention for achieving the above object is to arrange a plurality of ultrasonic transducers in an array, and sequentially switch and select the ultrasonic transducers to be used as one set in the array. In ultrasonic diagnostic equipment that scans acoustic beams electronically, a transmitting/receiving system that simultaneously receives signals from two directions by having two sets of receiving systems that make the receiving directivity symmetrical with respect to the central axis of the transmitted ultrasonic beam. It is characterized by reducing the difference in peak sensitivity and the difference in half-width of the directional characteristics.

Embodiment An embodiment of the present invention will be described with reference to the drawings.

FIG. 6 is a block diagram showing a linear scanning ultrasonic diagnostic apparatus which is an embodiment of the present invention.

In the figure, a transmission delay circuit 20 is a drive circuit that outputs N signals having a predetermined delay time to drive N balsers 21. The transducer selection switch @ path 22 selects N+2 of the M ultrasonic transducers 26 arranged in an array.
N pieces of ultrasonic transducers 2 that are adjacent to each other are selected, and in order to emit an ultrasonic beam, N pieces of ultrasonic transducers 2 excluding the ultrasonic transducers 26 at both ends of the selected ultrasonic transducers 26 are selected.
6 and N pulsers 21, and the selected N+2 ultrasonic transducers 23 and N+2 preamplifiers 24 are coupled in order to receive reflected signals. The reception delay circuit 25 inputs N+1 output p signals from 0 to Nth among the output signals amplified by the N+2 preamplifiers 24, and adds them after giving a predetermined delay time. and outputs a signal Sl corresponding to the scanning line. Further, the reception delay circuit 26 inputs N+1 output signals from the first to N+1 output signals amplified by the N+2 preamplifiers 24, and adds them after giving a predetermined delay time. , outputs a signal S2 corresponding to the scanning line. The result is the remaining ultrasonic transducer group obtained by removing one ultrasonic transducer from the selected ultrasonic transducers, and the remaining ultrasonic transducers obtained by removing the other ultrasonic transducer from the selected ultrasonic transducers. Two reception ultrasonic transducer groups are formed with the acoustic wave transducer group. Note that the output signals S1 and R2 are input to a display device (not shown) via a known processing circuit, and are used for displaying a tomographic image.

Next, the operation of the above configuration will be described. For convenience of explanation, a case where N is 5 will be described.

First, as shown in the fourth factor, the transducer selection switching circuit 22 selects seven ultrasonic transducers 26 #0 to #6, among which five ultrasonic transducers #1 to #5. 23 and five balsers 21 are connected, and the excitation pulse signal output from the balsers 21 is applied to the ultrasonic transducers 23 #1 to #5 with a predetermined delay time.

Ultrasonic beams are emitted from the ultrasonic transducers 26 #1 to #5 in the direction of the axis To of the central ultrasonic transducer #3. After the emission, the transducer selection switching circuit 22 sends each of the six ultrasonic transducers 23 #0 to #5 and #1 to #6 through the preamplifier 24 to delay reception, as shown in the fourth factor. circuit 25
and another reception delay circuit 26. Then #
The reflected echo signals received by the ultrasonic transducers 23 of 0 to #5 are amplified by the preamplifier 24 and then input to the reception delay circuit 25, where they are given a predetermined delay time and added together, corresponding to the scanning line. The signal S1 is output from the reception delay circuit 25. Similarly, the reflected signals received by the ultrasonic transducers 23 #1 to #6 are output from the reception delay circuit 26 via the preamplifier 24 as a signal S2 corresponding to the scanning line. In this case, since the receiving directivity R1 and R2 are symmetrical with respect to the transmitting directivity To, the total transmitting and receiving directivity TR1 and TR2 can be made to have essentially the same beat sensitivity and half width. .

The above-mentioned total transmitting and receiving directivity TR1 and TR2 can also be confirmed from the following calculation results of sound field characteristics. The calculation conditions are for a linear scanning ultrasound diagnostic device.
The pitch of the vibrator is 1.5 m, the frequency is 3.51 kfH
z, the focal point is 50u1, the number of ultrasonic transducers for transmission is 8,
The receiving ultrasonic transducers are two sets of nine ultrasonic transducers, each consisting of the transmitting ultrasonic transducers plus one at each end in the arrangement direction. As for the sound field characteristics at the focal point 50, as shown in FIG.
6 and 14, the peak sensitivity and half-width (0,8
6-1) can be made completely equal. Therefore, even if reflected signals from one ultrasound beam are simultaneously received from two different directions, a striped pattern due to the difference in peak sensitivity and the difference in half-value width can be prevented from appearing in the tomographic image.

Although the above embodiments of this invention have been described in detail, this invention is not limited to the above embodiments, and it goes without saying that it can be implemented with appropriate modifications within the scope of the gist of this invention. Nor.

Next, a second embodiment of the invention will be described.

FIG. 6 is an explanatory diagram showing ultrasonic wave transmission and reception by an ultrasonic transducer in a sector scanning type ultrasonic diagnostic apparatus.

In the case of sector scanning, the transducer selection switching circuit 22 selects N mutually adjacent ultrasonic transducers 26 from among the N ultrasonic transducers 26 arranged in a play shape, and The vibrator 26 and N balsas 21 are connected, and
N ultrasonic transducers 26 and N preamplifiers 24 are connected. The N outputs from the N preamplifiers 24 are:
The signals are input to two sets of reception delay circuits, each consisting of a reception delay circuit 25 and a reception delay circuit 26.

In transmission, as shown in FIG. 6, an ultrasonic beam having a directivity To in the direction of angle θ0 is transmitted under the control of the transmission delay circuit 20. In receiving the reflected signal of the ultrasonic beam, the angle θ is adjusted by controlling two sets of reception delay paths 25 and 26 installed in parallel. −Δθ and θ. Reception directivity R1 and R2 are obtained in the direction of +Δθ. Therefore, the total transmitting and receiving directivity TR1 and TR2 have their respective peak values approximately in the directions of angles θo−−Δθ and θo−−.

It is almost symmetrical with respect to the transmission directivity ToK. therefore,
In sector and scanning, the peak sensitivity difference and the half-width difference in the overall directivity of transmitting and receiving can be made extremely small, and it is possible to prevent a striped pattern from appearing in a tomographic image.

The fact that the beater sensitivity difference and the half-width difference can be reduced even in sector scanning can be confirmed from the following calculation results of the sound field characteristics. The calculation conditions are that the pitch of the vibrator is 1.5-MHz, the frequency is 3.5 MHz, and the focal point is 50. ,,The direction of the emitted ultrasonic beam is diagonal at 60° from the central axis, and the receiving directivity is 29° from the central axis.
and the oblique direction of 31° and the sound field observation point are the focusing points. As for the sound field characteristics, as shown in FIG. 7, the two types of receiving directivity 60 and 61 are not completely symmetrical with respect to the transmitting directivity 62, so the two types of combined transmitting and receiving directivity 66 and 34 are completely symmetrical. will not be the same. However, the beam width (half width) at -6 dB is equal to 1.6111, and the peak sensitivity difference is Q, 3 dB, which can be made extremely small.

〔Effect of the invention〕

According to this invention, in an ultrasonic diagnostic apparatus adopting a simultaneous parallel reception method that increases the scanning line Wf degree without reducing the number of frames per unit time, in a linear scanning type ultrasonic diagnostic apparatus, peak sensitivity difference and The difference in value width can be completely eliminated, and in sector-scanning ultrasonic diagnostic equipment, the difference in peak sensitivity and difference in half-value width can be reduced to a completely non-problematic level.As a result, real-time performance and high image quality can be achieved. It is possible to provide an ultrasonic diagnostic apparatus capable of displaying a tomographic image having the following characteristics.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the transmission and reception of ultrasonic waves by an ultrasonic transducer in the conventional simultaneous parallel reception system, and Fig. 2 is a characteristic diagram showing the calculation results of sound field characteristics in the conventional simultaneous parallel reception system. Fig. 6 is a block diagram showing an embodiment of the present invention, Fig. 4 is an explanatory diagram showing transmission and reception of ultrasonic waves in the case of linear scanning in this invention, and Fig. 5 is a calculation result of sound field characteristics in the linear scanning. FIG. 6 is an explanatory diagram showing transmission and reception of ultrasonic waves in the case of sector scanning in the present invention, and FIG. 7 is a characteristic diagram showing calculation results of sound field characteristics in the sector scanning. 23... Ultrasonic transducer, 25.26... Reception delay circuit. Agent Patent Attorney Masayoshi Misawa 23 0.5mm/div

Claims (3)

[Claims] (1) By arranging a plurality of ultrasonic transducers in an array, and sequentially switching and selecting the ultrasonic transducers to be used as one set in this array, scanning of the ultrasonic beam is performed electronically. In the ultrasonic diagnostic equipment that performs 1. To reduce the peak sensitivity difference and half-width difference in the overall directivity characteristics of transmitting and receiving signals simultaneously received from two directions by having two sets of receiving systems that make the receiving directivity symmetrical with respect to the central axis of the transmitted ultrasound beam. An ultrasonic diagnostic device featuring: (2) The receiving system has a larger number of receiving ultrasonic transducers than the number of ultrasonic transducers that emit ultrasonic beams for linear scanning, and is symmetrical with respect to the transmitting ultrasonic transducer group. The ultrasonic diagnostic apparatus according to claim 1, characterized in that it has two sets of receiving ultrasonic transducer groups arranged in the following manner. (3) The receiving system receives two sets of reflected echoes of an ultrasound beam transmitted from a group of ultrasound transducers capable of sector scanning, with directivity substantially symmetrical with respect to the transmitted ultrasound beam. The ultrasonic diagnostic apparatus according to claim 1, further comprising a reception delay circuit.