JPS63203140A - 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] [Already Required] The present invention appropriately adjusts the polarity and amplitude of a drive pulse train supplied to a plurality of array-type transducers that transmit and receive ultrasonic waves approximately every half cycle of the transducer period. Transmission waveforms are selectively synthesized so that the transmission and reception waveforms have an envelope curve close to a Gaussian curve, for example, to obtain an ultrasonic diagnostic apparatus with good temporal resolution and azimuth resolution.

[Industrial application field]

The present invention relates to an ultrasonic diagnostic apparatus, and particularly to an improvement in a pulse train applied to an ultrasonic transducer.

[Traditional techniques]

Ultrasonic diagnostic equipment emits ultrasonic pulses in the form of a thin beam into a living body or other subject, receives reflected echoes generated at tissue interfaces intervening within the subject, and displays them on a cathode ray tube screen. , which displays the state of structures inside the body based on differences in reflection levels due to differences in acoustic properties, and attempts to detect abnormalities and abnormal positions within the subject. The emitted ultrasonic pulse has a pulse width of about several μ3 and a frequency of usually 2 to I
A frequency around OMHz is used. In addition, as a probe, several hundred narrow strip-shaped transducer elements are arranged horizontally (
For example, a linear scanning method in which ultrasonic pulses are emitted using a set of 16 transducer elements, and the next transmission is performed by scanning in a line to drive a new group of transducers by shifting one transducer element. Alternatively, a sector scanning method is known in which the deflection angle of an ultrasonic beam is changed by slightly delaying the phase (time) of a driving pulse applied to a plurality of closely arranged vibrators.

In either case, the applied pulse train is an impulse, or a pulse train consisting of one or two waves of constant amplitude pulses in the positive and negative directions is applied to the vibrating element.

[Problem that the invention seeks to solve]

According to the conventional configuration described above, the transducer element (PZT) of the probe
The driving pulse applied to is constant amplitude and half wavelength (λ/2
For example, when the pulse width is 143 μ9), the envelope curve of the impulse response (transmission/reception response) has an extremely steep rising portion (7a) as shown in envelope curve (7) in Figure 4; The descending portion (7b) becomes gradual. As a result, when an ultrasound beam is emitted to a subject, its reflected echoes are received by the same transducer element, and these are added together, the sound field level (Z-axis) does not form an ideal conical shape. However, there was a problem in that a false echo image was created by drawing a curve in the time axis direction (X-axis) and the azimuth direction (Y-axis).

The present invention has been made in view of the above-mentioned drawbacks, and its purpose is to provide an ultrasonic diagnostic apparatus in which the envelope curve of the transmitted and received waveforms becomes an optimal curve that provides good temporal resolution and azimuth resolution. The aim is to obtain the following.

[Means to solve the problem]

The ultrasonic diagnostic apparatus of the present invention appropriately selects the polarity and amplitude of the drive pulse to be supplied to each of the plurality of play-type transducers 1a to 1f that transmit and receive ultrasonic waves approximately every half cycle of the carrier period of the transducer. The ultrasonic transmitting and receiving signals of each transducer form a predetermined envelope curve.

[For production]

In the present invention, the transmission waveform is synthesized with a pulse train whose polarity and amplitude are selected approximately every half cycle of the transducer carrier period from the ultrasonic drive pulse, and the transmission and reception waveforms can form an envelope curve that is almost a Gaussian curve. , the sound field at the time of reception becomes an ideal conical shape, improving temporal and azimuth resolution, and eliminating blurring of reflected echo images.

〔Example〕

Hereinafter, the ultrasonic diagnostic apparatus of the present invention will be described in detail with reference to FIG. FIG. 1 shows a system diagram of a transmitting circuit of an ultrasonic diagnostic apparatus according to an embodiment of the present invention. For example, each drive circuit 2a is made of a piezoelectric element (PZT).

2b, 2c, ...2f makes the transducer l of the probe
a, lb, lc, ... 1f are driven. Drive J circuit 2
a, 2b, 2c, ---2f, each vibrator 1a, lb
, lc, . . . 1r, and a voltage is supplied from a variable transmission voltage generation circuit 3 for weighting each vibrator in the element direction. 6 is RO
Information on the amplitude and polarity of the impulse train (U data) is stored in 1.α means such as M or RAM. These data are read out to the next stage DigiCrew analog conversion circuit CD.
/A) 5 converts digital data into analog signal,
This analog signal is given to a transmission delay circuit group 4, and the delay circuit 4 applies a delay for focusing or scanning to a plurality of drive circuits 2a, 2b.

2 c + ...supplied to 2f. According to the calculation example using the envelope curve in FIG. 4, the drive circuit (2a).

2b, 2c, . . . 2f) are supplied with an impulse train 9 as shown in FIG. 2, an envelope diagram 10 (bold line) in FIG. 3 is obtained by these driving impulses. Note that the envelope diagram 11 (thin line) shows a Gaussian curve of the target value, and these envelope diagrams 10 are obtained by passing the received wave through a logarithmic circuit and performing full-wave rectification. In these calculation examples, it can be seen that the envelope map 10 obtained from the impulse train 9 in FIG. 2 shows a waveform that is extremely close to the envelope map 11 constructed from an ideal Gaussian curve.

Actual drive circuit (2a, 2b, 2c, ... 2f)
The waveform diagram of the output impulse train is shown in FIG. 6, and the transmitted and received signals are shown in FIG. As the drive circuit input waveform, use positive and negative half-wavelengths or pulses around half-wavelength, and select the polarity and amplitude appropriately for driving every half cycle of the transducer carrier period or every approximate value thereof at the time of rise. A rising curve of the envelope curve of the transmitted waveform is created by synthesizing the pulse trains, and even at the falling edge, the starting point is shifted from the last pulse at the rising edge by a half cycle of the transducer carrier, or by an approximate value thereof. The falling envelope curve of the transmitted wave is created by synthesizing a pulse train whose polarity and amplitude are appropriately selected, which are driven every half cycle or every approximate value thereof.

In addition, if the carriers of the received signals of the transducers 1a, lb, lc, -1f do not have exactly a constant cycle, use the approximate value to drive the carriers at a constant cycle, or change the read cycle of the memory circuit 6 in FIG. The carrier fluctuation may be absorbed by making it variable or by making a plurality of addresses in the memory circuit 6 correspond to a half period of the carrier.

According to the present invention, compared to the envelope curve 7 of the impulse response when a single half-wavelength impulse is given to the vibrator as shown in FIG. The envelope waveform (8 in FIG. 4) can have a gentler rise and steeper fall, and can also improve the time resolution. In addition, if the time waveform is shortened, m-finding in the element direction becomes ineffective, so there is a limit to waveform shortening.However, if the envelope curve of the time waveform is made into a Gaussian curve shape or a shape close to it, the time waveform becomes more detailed. (It can be done. The envelope curve 7.8 shown in FIG. 4 shows only the envelope curve of the received wave passed through a logarithmic circuit and full-wave rectified.

〔Effect of the invention〕

Since the present invention is configured as described above, it is possible to form a sound field with improved resolution in the time axis direction and azimuth resolution in the arrangement direction of the play type vibrators compared to the envelope curve of a single half-wavelength impulse response. The present invention has the advantage of providing an ultrasonic diagnostic apparatus that can prevent blurring and the like even when adding received signal echoes.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a transmission circuit showing an embodiment of the ultrasonic diagnostic device of the present invention, Fig. 2 is an input waveform diagram of the drive circuit, Fig. 3 is a comparison diagram showing a composite wave and a Gaussian wave, and Fig. 4 is a diagram showing a comparison diagram of a composite wave and a Gaussian wave. The figure is a comparison diagram of the envelope of a conventional impulse response and the composite wave of the present invention. Figure 5 is a waveform diagram of the transmission and reception signals of an actual impulse train. Figure 6 is a diagram of the output waveform of an actual drive circuit. la, lb, lc, Id, le, If... Probe transducer, 2a, 2b, 2c, 2d, 2e, 2f... Drive circuit, 3... Variable transmission voltage generation circuit, 4. ... Transmission delay circuit group, 5... Digital-to-analog conversion circuit, 6... Memory circuit.

Claims (3)

[Claims] (1) Drive pulses to be supplied to multiple array-type transducers that transmit and receive ultrasonic waves are synthesized by a pulse train whose polarity and amplitude are selected approximately every half cycle of the transducer carrier period, and the envelope curve of the transducer transmission and reception waveforms is calculated. An ultrasonic diagnostic device that is characterized by being optimized for communication. (2) At least a part of the falling slope of the envelope curve,
2. The ultrasonic diagnostic apparatus according to claim 1, wherein the pulse response is made steep due to the steepness of the rise of the pulse response of a single half wavelength. (3) At least a part of the rising slope of the envelope curve,
2. The ultrasonic diagnostic apparatus according to claim 1, wherein the amplitude of the pulse train is gradually increased so that the rising slope of the single half-wavelength impulse response is gentler than that of a single half-wavelength impulse response.