JPH0568258B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic diagnostic apparatus, and particularly to a pulser circuit that supplies drive pulses to an ultrasonic transducer.

[Conventional technology]

Generally, in an ultrasound diagnostic device, an ultrasonic transducer such as a piezoelectric element is brought close to the subject, a high-frequency AC voltage in the MHz band is applied to the transducer for a very short period of time, and the transducer emits pulsed ultrasonic waves. I'm letting you do it. Here, if the object to be examined is a homogeneous medium, propagating straight through it, and after a given time, if there is a tissue interface with different acoustic impedances, then
Some of it is reflected and some of it is transmitted. This reflected wave is received by the transducer, and the distance from the transducer to the boundary surface is measured based on the speed of the ultrasonic waves and the ultrasonic pulses that reciprocate and return.

In a radial scanning type diagnostic device, the vibrator is rotated within the cross section of the subject. By transmitting and receiving ultrasonic pulses by the transducer n times every time the transducer rotates once, a scanning line is obtained by dividing a circle centered on the transducer into n equal parts in the angular direction, and an image of the subject is thus obtained. It will be done.

[Problem that the invention seeks to solve]

Here, conventionally, the probe equipped with the ultrasonic transducer and the electric circuit part that applies a drive pulse (high-frequency AC voltage) to the ultrasonic transducer and forms an image from the reflected ultrasound signal obtained from the transducer are separate. It's familiar to my body. Further, the types of ultrasonic transducers differ depending on the subject. For example, there are resonant frequencies, and the optimal pulse width of the driving pulse of the ultrasonic transducer differs depending on the resonant frequency.

However, the electrical circuit part can be expensive,
Conventionally, the same probe is used for all probes. For this reason, depending on the type of probe connected, it may not be possible to supply a drive pulse with an optimal pulse width to the ultrasonic transducer. When an ultrasonic transducer is driven with a drive pulse having a pulse width that does not correspond to the resonance frequency, there is a drawback that vibrations in modes other than thickness vibration are also generated.

This invention was made to address the above-mentioned circumstances, and its purpose is to provide an ultrasonic diagnostic device that can always drive an ultrasonic transducer with a drive pulse of an optimal pulse width even if the resonance frequency of the ultrasonic transducer differs. The goal is to provide the following.

[Means for solving problems]

An ultrasound diagnostic apparatus according to the present invention includes a rotating means for rotating an ultrasound transducer, and a signal processing means for processing a received signal of ultrasound transmitted from the ultrasound transducer and reflected by a subject. In the ultrasound diagnostic apparatus, a synchronization signal generating means generates a synchronization signal synchronized with the rotation of the ultrasound transducer, and outputs a drive signal having a pulse width suitable for driving each of a plurality of ultrasound transducers having different resonance frequencies. a plurality of drive signal output means, and a switching means for selectively inputting a synchronization signal output from the synchronization signal generation means to any of the plurality of drive signal output means, the drive signal output means A drive signal is generated in synchronization with the synchronization signal.

[Effect]

According to the ultrasonic diagnostic apparatus according to the present invention, a plurality of drive signal generating means for generating drive signals of various pulse widths are provided, and one of the drive signal generating means for generating drive signals of various pulse widths is selected depending on the resonance frequency of the ultrasonic transducer used. A signal generation means is selected, a synchronization signal is supplied only to the selected drive signal generation means, and only this drive signal generation means drives the ultrasonic transducer in synchronization with the synchronization signal. Therefore, it is possible to provide an ultrasonic diagnostic apparatus that can always drive the ultrasonic transducer with a drive pulse having an optimal pulse width even if the resonance frequency of the ultrasonic transducer changes.

〔Example〕

An embodiment of the ultrasonic diagnostic apparatus according to the present invention will be described below with reference to the drawings. Here, instead of changing the ultrasonic transducer by replacing the probe with the ultrasonic transducer, we provide multiple ultrasonic transducers that are integrally scanned within the probe and electrically transmit the ultrasonic waves. Suppose we want to switch the vibrator. This has the advantage that the ultrasonic transducer can be changed depending on the subject without changing the probe each time. Of course, it is also possible to provide a plurality of probes each having an ultrasound transducer with a different resonance frequency, and to switch the ultrasound transducer by replacing the probes depending on the subject. As an example, an ultrasonic endoscope apparatus will be described in which a plurality of ultrasonic transducers that are integrally scanned are built into the distal end of an insertion section of an endoscope (fiberscope).

FIG. 1 is a schematic diagram showing the configuration of the first embodiment. Two ultrasonic transducers (piezoelectric elements) 12 and 14 having different resonance frequencies are fixed to a transducer fixing member 16. The transducer fixing member 16 is the ultrasonic transducer 1
It is rotated by a motor 18 at the end opposite to the end where 2 and 14 are fixed. As a result, the ultrasonic transducers 12 and 14 are rotated together. The transducer fixing member 16 is inserted into the insertion section of the endoscope,
Radial scan the object. Ultrasonic transducer 12,
14 are fixed at different locations in the circumferential direction of the transducer fixing member 16, so that the ultrasonic transducers 12, 1
4 is rotated with a predetermined phase difference (for example, 180° C.).

A rotary encoder 20 is connected to the motor 18 , and the output of the rotary encoder 20 is supplied to an encoder control circuit 22 . The rotary encoder 20 outputs pulses in synchronization with the rotation of the motor 18.
For example, 256 synchronization pulses are generated for each rotation.
The rotation speed of the motor 18 is determined by the encoder control circuit 22.
controlled by The encoder control circuit 22 generates pulses (512 pulses during one rotation) at the rising and falling edges of the synchronization pulses supplied from the rotary encoder 20, and uses these pulses as timing signals to vibrate the vibrator in the observation device. 24
supply to. The encoder control circuit 22 also supplies a positioning pulse to the observation device 24 for determining the writing start position on the screen.

The observation device 24 sends a drive pulse synchronized with the timing signal to a pulser circuit 28 via a switch 26.
supply to. The switch 26 is manually switched, and the drive pulse from the observation device 24 is sent to the pulser circuit 28 through either the first or second output terminal.
supply to. The pulser circuit 28 boosts this pulse and supplies it to either the ultrasonic transducer 12 or 14 depending on which side the switch 26 is switched to.

Ultrasonic pulses transmitted from the ultrasound transducer, reflected at the interface between tissues with different acoustic impedances, and received by the ultrasound transducer again are converted into received signals, which are sent to the observation device 24 via the amplifier 30.
is input. The observation device 24 brightness-modulates the received signal and displays a tomographic image of the subject on a monitor.

Here, when the switch 26 is switched, the positioning pulse for starting writing on the screen is moved by the encoder control circuit 22. As a result, observation device 2
Even if the starting position of the screen of the monitor No. 4 changes, the ultrasonic transducer is switched, and the rotational phase changes, the positional relationship of the subject to the transducer on the monitor does not change.

The pulser circuit 28 adjusts the pulse width to match the resonance frequency of each ultrasonic transducer 12, 14 before outputting the drive pulse supplied from the observation device 24 to the ultrasonic transducers 12, 14 via the switch 26. Set the pulse width to an appropriate value.

Therefore, in the first embodiment, a CR differentiator circuit as shown in FIG. 2a is used. By adjusting the value of the time constant CR, the pulse width of the output pulse Vout can be adjusted. That is, the ultrasonic transducer 12,
A differentiating circuit having a time constant CR capable of obtaining a pulse width suitable for the resonance frequency of 14 is connected to each of the ultrasonic transducers 12 and 14, and the first and second outputs of the switch 30 are supplied to the differentiating circuit, respectively. Ru.
That is, by selecting the switch 26, one of the differentiating circuits is selected, and the pulse width of the drive pulse is converted to a pulse width corresponding to the resonance frequency. Actually, as shown in FIG. 2b, the drive pulse is supplied to the differentiating circuit via the transformer 32.

In this way, by making the pulse width of the drive pulse correspond to the resonance frequency of the ultrasonic transducer, vibrations in modes other than the required thickness vibration mode are reduced.

Additionally, in general, it takes time for the voltage of an ultrasonic transducer to subside its mechanical vibration (see Figure 4 a, b), but at the resonant frequency (see Figure 3), electrical energy is efficiently converted into mechanical energy. Because of this, vibrations are well suppressed. Therefore, when displaying an image using an observation device, the voltage of the oscillator quickly drops to 0, and the potential reaches 0 before the next drive pulse is input.
This means that there is no influence from other pulses, and the resolution in displaying images of the object is improved.

As explained above, according to the first embodiment, when the ultrasonic transducer is switched, the pulse width of the drive pulse output from the observation device 24 is changed by switching the time constant of the differential circuit. It is possible to convert the driving pulse width to the optimum driving pulse width corresponding to the resonance frequency, thereby reducing pulse signal loss, improving the resolution of the observation device, and driving the ultrasonic transducer efficiently.

Next, another embodiment of this invention will be described. Fifth
The figure is a circuit diagram of the pulser circuit portion of the second embodiment. The second embodiment is the same as the first embodiment except for the pulser circuit, so only the pulser circuit will be described.

In the second embodiment, a one-shot multivibrator 50 is used as the pulse width conversion means. The one-shot multivibrator 50 changes the pulse width of the output pulse by changing the resistance value of an external variable resistor R'. This also provides a driving pulse with a pulse width corresponding to the resonance frequency of the ultrasonic transducer, and provides the same effect as in the first embodiment.

FIG. 6 is a circuit diagram of the pulser circuit portion of the third embodiment. In the third embodiment, a plurality of probes each having an ultrasonic transducer having a different resonance frequency are provided, and the ultrasonic transducer is switched by replacing the probe. A drive pulse from the observation device is supplied to the input terminal Vin of the PROM 60. A switch 62 is connected to PROM60,
By switching this switch 62, the drive pulse is output from either output terminal. PROM60
A plurality of one-shot multivibrators 64 having different time constants are connected to each output terminal. The output of the one-shot multivibrator 64 is supplied to the ultrasonic transducer via an open collector transistor 66. In other words, switch 6
2 converts the drive pulse into a pulse with a different pulse width, so even if the probe is replaced and the resonance frequency of the ultrasonic transducer changes, the one-shot multivibrator 64 can be selected by switching the switch 62. This can be handled by Also,
PROM60 is set by the switch as in the first embodiment.
If the signal to be supplied to the one-shot multivibrator 64 is selected from among a plurality of signals,
It can also be applied when driving multiple vibrators with different resonance frequencies.

[Effects of the Invention] As explained above, according to the present invention, the pulse width of the driving pulse is converted into a pulse width corresponding to the resonant frequency of the ultrasonic transducer and then supplied to the transducer, so the driving efficiency is increased. , pulse signal loss during signal transmission is reduced, mechanical vibrations are suppressed well, and an ultrasonic transducer with high resolution can be provided. Note that the present invention is not limited to the above-described embodiments, and can be modified in various ways without departing from the spirit thereof. For example, it is not limited to an ultrasound endoscope, nor is there any limitation to the operation of an observation device.

[Brief explanation of the drawing]

FIG. 1 shows a first diagram of an ultrasonic diagnostic apparatus according to the present invention.
Schematic diagram showing the outline of the embodiment, Figures 2a and b are the first
Figure 3 shows the special impedance of a general ultrasonic transducer; Figure 4 a and b show the input/output characteristics of a general ultrasonic transducer. FIG. 5 is a diagram showing a one-shot multivibrator used in the pulser circuit of the second embodiment, and FIG. 6 is a diagram showing the pulser circuit of the third embodiment. 12, 14... Ultrasonic transducer, 18... Motor, 20... Rotary encoder, 22... Encoder control circuit, 24... Observation device, 28... Pulsar circuit.

Claims (1)

[Scope of Claims] 1. An ultrasonic wave device comprising: a rotating means for rotating an ultrasonic transducer; and a signal processing means for processing a received signal of the ultrasonic wave transmitted from the ultrasonic transducer and reflected by a subject. In the diagnostic apparatus, a synchronization signal generating means generates a synchronization signal synchronized with the rotation of the ultrasonic transducer, and outputs a drive signal having a pulse width suitable for driving each of the plurality of ultrasonic transducers having different resonance frequencies. a plurality of drive signal output means; and a switching means for selectively inputting a synchronization signal outputted from the synchronization signal generation means to any of the plurality of drive signal output means, the drive signal output means comprising: An ultrasonic diagnostic device characterized by generating a drive signal in synchronization with a synchronization signal. 2. Claim 1, comprising an ultrasonic probe that has a plurality of ultrasonic transducers with different resonance frequencies and is built into an insertion section of an endoscope.
The ultrasonic diagnostic device described in section. 3. Claim 2, wherein the plurality of ultrasonic transducers are integrally radially scanned.
The ultrasonic diagnostic device described in section. 4. Any one of claims 1 to 3, wherein each of the drive signal output means comprises a differentiating circuit that can change the pulse width of the output pulse by adjusting a time constant. The ultrasonic diagnostic device described in . 5. The drive signal output means is a one-shot multivibrator that can change the pulse width of the output pulse by adjusting an external resistance value. The ultrasonic diagnostic device according to item 1.