JPH06114056A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

PURPOSE:To enable the obtaining of a clear tomographic image from shallow parts to deep parts in an ultrasonic diagnostic apparatus by upgrading real time performance of an image display in employing a multi-stage focus system. CONSTITUTION:Ultrasonic waves with focuses varying according to the depth of a specimen while being varied in frequency according to the respective focuses are emitted simultaneously from a probe 4 with a drive signal generation circuit 12 and a synthesization circuit 14 transmitting composing a transmitting section 8 and a vibrator selection circuit 16. Then, echo signals to be obtained based on the reflection of the ultrasonic waves are delayed with an echo signal processing circuit 22 of the receiving section 10 by a time the same as that as required when they are transmitted once selected in terms of frequency according to the focuses. After amplified the individual echo signals are synthesized with a synthesization circuit 24 for receiving.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-stage focus type ultrasonic diagnostic apparatus.

[0002]

2. Description of the Related Art Some conventional ultrasonic diagnostic apparatuses employ a so-called multi-stage focusing method.

In this multi-stage focusing system, the ultrasonic beam is
Focus points F that converge the beam₁, F₂, F ₃Is, for example, F₁Is
Short distance, F₂Is a medium distance, F₃Is a long distance, depth
The ultrasonic waves are transmitted and received differently according to the
The echo signal based on the generated ultrasonic wave is applied to each focus F₁, F₂, F₃
One scan line data is obtained by splicing each according to
It is something.

As described above, the divergence of the ultrasonic beam is suppressed by changing the focal length at which the ultrasonic beam converges in accordance with the depth within the object. It is possible to obtain an image with good resolution over the entire area.

[0005]

However, according to the conventional multi-stage focusing method, when n focal points are provided, it is necessary to transmit and receive waves n times in order to obtain one scanning line data. Frame rate required for screen formation is about 1 / n
become. Therefore, as the number n of the focal points is increased in order to improve the resolution, the real-time property is lost, and a necessary tomographic image cannot be obtained for an organ that moves fast.

Moreover, in the conventional multi-stage focusing method, although the focus is changed according to the depth, the ultrasonic wave transmission frequencies are all the same.

Therefore, for example, if the transmission frequency of ultrasonic waves is set high in order to increase the distance resolution, ultrasonic echoes from a long distance are attenuated, the S / N ratio deteriorates, and the image quality deteriorates. There is a problem of deterioration.

The present invention has been made to solve the above-mentioned problems, and in the multi-stage focus system,
It is an object to improve the real-time property of image display and to obtain a clear tomographic image from a shallow portion to a deep portion.

[0009]

In order to solve the above-mentioned problems, the present invention comprises a probe having a plurality of transducers arranged in an array, and ultrasonic waves emitted from the probe to a subject are detected. The following configuration is adopted in an ultrasonic diagnostic apparatus of a multi-stage focus system in which a focus is changed in a plurality of stages according to a depth position of a subject to perform transmission / reception.

That is, according to the present invention, a wave transmitter for driving the probe to emit an ultrasonic wave and a wave receiver for processing an echo signal based on the ultrasonic echo received by the probe are provided. The wave portion is a drive signal generation circuit that delays and outputs a drive signal having a drive voltage and a drive frequency different from each other according to each focus by a time corresponding to each focus, and each drive from this drive signal generation circuit. A wave-transmitting synthesis circuit that synthesizes signals and a transducer selection circuit that applies the drive signal synthesized by this synthesis circuit to a predetermined number of transducers are provided, while the receiving unit is selected by the transducer selection circuit. And an echo signal processing circuit that sorts the echo signals obtained based on the ultrasonic waves transmitted and received by each transducer according to the frequency, delays and amplifies each sorted echo signal by the delay time, and , This And configured to include a reception for synthesis circuit for synthesizing each echo signal passed through an echo signal processing circuit.

[0011]

In the above structure, the drive signal generating circuit of the wave transmitting unit delays and outputs the drive signals having the drive voltages and the drive frequencies different from each other according to each focus. These drive signals are combined by the wave-transmitting combining circuit, and then applied to a predetermined number of vibrators selected by the vibrator selecting circuit. As a result, the selected transducer simultaneously emits ultrasonic waves having different focal lengths at which the ultrasonic beams converge according to the depth within the subject and different frequencies for each focus.

The echo signal processing circuit of the wave receiving unit sorts the echo signals obtained based on the ultrasonic waves transmitted and received by each transducer selected by the transducer selection circuit according to the frequency and The echo signal is delayed, amplified, and output by the same delay time as in the case of transmission. Then, the echo signals that have passed through the echo signal processing circuit are combined by the receiving wave combining circuit.

As described above, according to the present invention, when performing multi-stage focusing, it is not necessary to time-divisionally transmit and receive ultrasonic waves as in the prior art, and ultrasonic waves having different focal points are simultaneously transmitted and Since the sound wave has an appropriate frequency according to each focus, the real-time property is not impaired, and an image with good resolution and S / N ratio can be obtained.

[0014]

1 is a block diagram of an ultrasonic diagnostic apparatus according to an embodiment of the present invention.

In the figure, reference numeral 1 indicates the whole of a multi-stage focus type ultrasonic diagnostic apparatus, 2 is a subject, and 4 is a probe for transmitting and receiving ultrasonic waves to and from the subject 2. It is a linear scanning type in which the vibrators 6 are arranged in an array.

Reference numeral 8 is a wave transmitter for driving the probe 4 to emit ultrasonic waves, and 10 is a wave receiver for processing an echo signal based on the ultrasonic echo received by the probe 4.

Then, the wave transmitter 8 is provided with the drive signal generating circuit 1
2, composed of a wave transmission synthesis circuit 14 and a transducer selection circuit 16.

The drive signal generating circuit 12 outputs drive signals having different drive voltages and drive frequencies according to the respective focal points of the ultrasonic waves emitted from the probe 4 toward the subject for the time corresponding to the respective focal points. The output is delayed, and in this example, the focal points F ₁ , F ₂ , and F ₃ (in this example, F 1
Three delay circuits 18 ₁ , in which individual delay amounts for each transducer 6 are set in advance in order to converge the ultrasonic wave to ₁ (short distance, F ₂ is medium distance, F ₃ is long distance) 18 ₂ and 18 ₃ ,
In response to a trigger signal given a predetermined delay time in each of the delay circuits 18 ₁ , 18 ₂ and 18 ₃ , different driving voltages and driving frequencies v ₁ (f ₁ ), v ₂ (f ₂ ), v ₃ It is composed of pulser circuits 20 ₁ , 20 ₂ and 20 ₃ which output a drive signal having (f ₃ ).

The wave-transmitting synthesizing circuit 14 synthesizes the drive signals from the drive signal generating circuit 12, and in this example, the resistors R _{1 to} R ₃ for level adjustment, the feedback resistor R ₄ , and the calculation. It is composed of an amplifier Amp ₁ , an amplifier Amp ₂ , and a diode D for blocking an echo signal (received wave) backflow.

The oscillator selection circuit 16 is a transmission wave synthesis circuit 1.
The drive signal combined in 4 is applied to a predetermined number of vibrators 6, and in this example, it is composed of a multiplexer.

On the other hand, the wave receiving unit 10 comprises an echo signal processing circuit 22, a wave receiving synthesis circuit 24, and an amplifier 26.

The echo signal processing circuit 22 sorts the echo signals obtained based on the ultrasonic waves transmitted and received by each transducer 6 selected by the transducer selection circuit 16 according to the frequency, and also sorts the selected echoes. The signal is delayed by the delay time, amplified, and output. In this example, different drive voltages and frequencies v ₁ (f ₁ ), v ₂ (f ₂ ) from the drive signal generation circuit 12 _Three bands that select the ultrasonic echo signals of different frequencies f ₁ , f ₂ , f ₃ generated based on the drive signal having v ₃ (f ₃ ) for each frequency f ₁ , f ₂ , f ₃ The echo signals that have passed through the pass filters 28 ₁ , 28 ₂ , 28 ₃ and the band pass filters 28 ₁ , 28 ₂ , 28 ₃ are set in the delay circuits 18 ₁ , 18 ₂ , 18 ₃ of the transmitting unit 8. Delay circuit 3 to delay with the same delay amount
0 ₁ , 30 ₂ , and 30 ₃ .

The wave receiving / synthesizing circuit 24 synthesizes the echo signals passed through the echo signal processing circuit 22, and in the present example, is composed of a changeover switch.

Reference numeral 32 is a digital scan converter.
(Hereinafter referred to as DSC).

In the above structure, the delay circuits 18 ₁ , 18 ₂ , 18 _{3 of the} drive signal generating circuit 12 are controlled by the control circuit (not shown).
When a trigger signal is applied to each delay circuit 18 ₁ , 1
8 ₂ and 18 ₃ output this trigger signal by giving an individual delay amount set for each transducer 6 in order to converge the ultrasonic waves to the focal points F ₁ , F ₂ , and F _3. To do. And
Each delay trigger signal each subsequent stage of each pulser circuit 20 ₁ with, 20 _2, 20 when applied to the _3, from the pulser circuit 20 _1, 20 _2, 20 _3, different driving voltages and the driving frequency v ₁ together A drive signal having (f ₁ ), v ₂ (f ₂ ) and v ₃ (f ₃ ) is output.

Then, each drive signal is transmitted to the wave synthesizer circuit 1.
After being synthesized in 4, the oscillators are applied to a predetermined number of oscillators 6 selected by the oscillator selection circuit 16.

For example, as shown in FIG. 2, when the number of transducers 6 in one block for transmitting and receiving ultrasonic waves is 32 and linear scanning is performed, the focus F ₁ for short range is 1 block. In the center, the transducers 6 to 9 are numbered 24, the focal point F ₂ for medium distance is the transducer 6 to numbers 4 to 29, and the focal point F ₃ for long distances is numbered 1 to 32. Each of the vibrators 6 is formed. Therefore, drive signals having drive voltages v ₁ (f ₁ ), v ₂ (f ₂ ), and v ₃ (f ₃ ) are applied to the transducers 3 to 9 to 24, respectively. Drive signals having drive voltages of v ₂ (f ₂ ) and v ₃ (f ₃ ) are applied to the oscillators 3 to 29,
Further, a drive signal having a drive voltage of v ₃ (f ₃ ) is applied to the vibrators 6 of Nos. 1 to 3 and Nos. 30 to 32, respectively. Moreover, of the drive voltages v ₁ (f ₁ ), v ₂ (f ₂ ), and v ₃ (f ₃ ) applied to the transducer 6 having numbers 9 to 24, the focus F ₁ is set at v ₁ (f ₁ ).
Delay amount converges, v delay amount converges on the focal point F ₂ to _2, v ₃ delay amount to converge to the focal point F ₃ in (f ₃₎ is, so that each is given separately. Further, the drive voltages v ₂ (f ₂ ) and v ₃ applied to the vibrators 6 to 8 and numbers 25 to 29 are given.
Of (f ₃ ), v ₂ (f ₂ ) has a delay amount v that converges on the focus F _2.
A delay amount that converges on the focal point F ₃ is individually given to ₃ (f ₃ ). Further, the drive voltage v ₃ (f ₃ ) applied to the vibrator 6 of Nos. 1 to 3 and Nos. 30 to 32 is given a delay amount that converges on the focus F ₃ .

As a result, from the selected vibrator 3,
The focal lengths F ₁ , F ₂ and F _{3 at} which the ultrasonic beams converge are different according to the depth within the subject 2, and the frequencies f ₁ , f ₂ and F ₃ are different for each of the focal points F ₁ , F ₂ and F ₃ . Ultrasonic waves with different f ₃ are emitted almost simultaneously. Here, for example, a frequency f ₁ corresponding to the focus F ₁ of the short-distance is 7.5 MHz, the frequency f ₂ corresponding to the focus M ₂ intermediate- is 5 MHz, the frequency corresponding to the focus F ₃ for long range f _{If 3} is set to 3.5 MHz, that is, the frequency is relatively high in the case of a short distance, and becomes lower in the case of a long distance, the influence of absorption and attenuation of ultrasonic waves in the subject 2 is reduced. can do.

In this way, the ultrasonic wave reflected by each part in the subject 2 is transmitted to each transducer 6 selected by the transducer selection circuit 16.
When transmitted and received with (32 in this example), from each transducer 6,
Since the echo signal based on the received ultrasonic wave is output,
This echo signal is input to each band pass filter 28 ₁ , 28 ₂ , 28 ₃ via the transducer selection circuit 16. As a result, the echoes of the frequencies f ₁ , f ₂ , f ₃ corresponding to the drive signals having the drive voltages v ₁ , v ₂ , v ₃ are output from the bandpass filters 28 ₁ , 28 ₂ , 28 ₃ , respectively. The signal is picked up. The echo signals of the respective frequencies f ₁ , f ₂ , f ₃ are delayed by the delay circuits 30 ₁ , 30 ₂ , 30 _{3 in} the next stage by the same delay amount as in the case of transmission and output. Then, the echo signals that have passed through the echo signal processing circuit 22 are synthesized by the wave receiving synthesis circuit 24, amplified by the amplifier 26, and then digitized by the DSC 32 to be captured as an image signal.

In the above embodiment, the bandpass filter 28 ₁ for signal selection of the echo signal processing circuit 22 is used.
Although 28 ₂ and 28 ₃ are used, it is also possible to apply a dynamic band pass filter.

[0031]

According to the present invention, when performing multi-stage focusing, it is not necessary to transmit and receive ultrasonic waves in a time-division manner as in the conventional case, and ultrasonic waves having different focal lengths are simultaneously transmitted, and Since the ultrasonic wave has an appropriate frequency according to each focal length, real-time performance is not impaired, and the resolution and S /
A tomographic image with a good N ratio can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of an ultrasonic diagnostic apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the relationship between the selection of each transducer of the probe and the focal length when performing multi-stage focusing.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ultrasonic diagnostic apparatus, 2 ... Subject, 4 ... Probe, 6 ...
Oscillator, 8 ... Wave sending unit, 10 ... Wave receiving unit, 12 ... Drive signal generating circuit, 14 ... Wave sending combining circuit, 16 ... Oscillator selecting circuit, 22 ... Echo signal processing circuit, 24 ... Wave receiving combining circuit.

Claims (1)

[Claims] 1. A probe having a plurality of transducers arranged in an array is provided, and the focus of ultrasonic waves emitted from the probe to a subject is changed in a plurality of stages according to the depth position of the subject to transmit and receive. A multi-stage focus type ultrasonic diagnostic apparatus for performing a wave, comprising: a transmitter for driving the probe to emit an ultrasonic wave; and a receiver for processing an echo signal based on an ultrasonic echo received by the probe. A wave section, the wave transmitting section delays a drive signal having a drive voltage and a drive frequency different from each other according to each focus by a time corresponding to each focus, and outputs the drive signal generation circuit; The wave receiving section includes a wave-transmitting synthesis circuit that synthesizes the drive signals from the drive signal generation circuit and a transducer selection circuit that applies the drive signal synthesized by the synthesis circuit to a predetermined number of transducers. Is the oscillator selection The echo signals obtained based on the ultrasonic waves transmitted and received by each transducer selected by the selection circuit are sorted according to the frequency, and each sorted echo signal is delayed and amplified by the delay time and output. An ultrasonic diagnostic apparatus comprising: an echo signal processing circuit; and a receiving wave combining circuit that combines the echo signals that have passed through the echo signal processing circuit.