JP2001095798A - Ultrasonic picture taking procedure and ultrasonic wave diagnosis apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the ultrasonic picture taking procedure and the ultrasonic diagnostic apparatus which the special circuit to calculate mutual correlation is unnecessary, and can improve both sensitivity and resolution by simple procedure. SOLUTION: The transmitting signal generator 3 generates the frequency modulated signal such as chirp signal. The transmitting part 2 amplifies frequency modulated transmitting signal made by the transmitting signal generator 3, and drives the probe 1. The probe 1 converts electric signal from the transmitting part 2 to the ultrasonic signal, and transmits into the living body, and receive the echo signal reflected by the living body and converts to electric signal. The signal receiving part 4 amplifies receiving signal converted from ultrasonic signal to electric signal by the probe 1. The band pass-filter part 5 filters the receiving signal by the filter which its band pass range is varied by the reflecting depth of the receiving signal. The filtered signal is detection treated by the detecting part 6, and after converted to the image information by the DSC (scanning conversion) part, and displayed by the monitor 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic imaging method and an ultrasonic diagnostic apparatus, and more particularly, to a medical ultrasonic diagnostic apparatus that encodes a transmission waveform without requiring a special circuit for calculating a cross-correlation. It is configured to improve both sensitivity and resolution.

[0002]

2. Description of the Related Art Conventionally, in an ultrasonic diagnostic apparatus, an attempt to improve sensitivity and resolution has been to reduce the width of a transmission pulse and increase the amplitude. However, this method has reached its limit due to limitations such as the circuit size and the withstand voltage of the probe.

[0003] The pulse compression method has been considered. In this method, the sensitivity and resolution can be improved by encoding and transmitting a transmission waveform and processing the received echo signal.

As a typical pulse compression method, there is a method in which a chirp wave is used as a transmission signal and a correlation operation between the reception signal and the transmission signal is performed to improve sensitivity and resolution. FIG. 10 shows a block diagram of a conventional ultrasonic diagnostic apparatus using the coded transmission method.

[0005]

However, the conventional method shown in FIG. 10 has a problem that a circuit for calculating a cross-correlation between a received echo signal and a transmission signal is required separately.

Therefore, the present invention solves the above-mentioned conventional problems, and does not require a special circuit for calculating a cross-correlation, and an ultrasonic imaging method and an ultrasonic diagnosis which improve both sensitivity and resolution by a simple method. It is intended to provide a device.

[0007]

According to the first aspect of the present invention, a frequency-modulated ultrasonic signal is transmitted to a living body, an echo signal thereof is received, and the received signal has a deeper reception depth. , The image is filtered using a high-frequency component only at a short distance, and an image is formed using only a low-frequency component at a long distance.

According to a second aspect of the present invention, in the first aspect, the frequency-modulated ultrasonic signal is an up-chirp signal in which the instantaneous frequency change rate increases as the instantaneous frequency increases. Alternatively, the down-chirp signal is such that the instantaneous frequency change rate decreases as the instantaneous frequency decreases, so that energy can be concentrated on low frequency components.

According to a third aspect of the present invention, in the first or second aspect, the frequency-modulated ultrasonic signal is an amplitude-modulated chirp signal, and the energy is changed according to the instantaneous frequency. It can be changed freely.

According to a fourth aspect of the present invention, there is provided the up-chirp signal according to any one of the first to third aspects, wherein the frequency-modulated ultrasonic signal has a smaller amplitude as the instantaneous frequency increases. Or a down-chirp signal in which the amplitude increases as the instantaneous frequency decreases, and a large energy can be given to the low-frequency component.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the frequency-modulated ultrasonic signal is a binary or ternary rectangular chirp signal. Therefore, the transmission circuit can be simplified.

According to a sixth aspect of the present invention, there is provided a probe for transmitting and receiving an ultrasonic wave, a transmission signal generator for generating a frequency-modulated probe drive signal, and amplifying the probe drive signal. A transmitting unit that drives the probe, a receiving unit that amplifies a received signal, and a band-pass filter unit that changes a pass frequency band according to the receiving depth, transmits a frequency-modulated ultrasonic signal to a living body. The received echo signal is received, and the received signal is filtered by a band-pass filter whose passing frequency band decreases as the receiving depth increases.At short distances, an image is formed using only high-frequency components. At a long distance, an image can be formed using only low frequency components.

According to a seventh aspect of the present invention, in the sixth aspect, the frequency-modulated ultrasonic signal is an up-chirp signal in which the instantaneous frequency change rate increases as the instantaneous frequency increases. Alternatively, the down-chirp signal is such that the instantaneous frequency change rate decreases as the instantaneous frequency decreases, so that energy can be concentrated on low frequency components.

According to an eighth aspect of the present invention, in the sixth or seventh aspect, the frequency-modulated ultrasonic signal is an amplitude-modulated chirp signal, and the energy is changed according to the instantaneous frequency. It can be changed freely.

According to a ninth aspect of the present invention, in any one of the sixth to eighth aspects, a resistor is inserted in series with a power supply line for supplying power to the transmission section, and a capacitor is inserted in parallel with the power supply line. The frequency-modulated ultrasonic signal is an up-chirp signal in which the amplitude decreases as the instantaneous frequency increases, and a large energy can be given to the low-frequency component.

According to a tenth aspect of the present invention, in any one of the sixth to ninth aspects, the frequency-modulated ultrasonic signal is a binary or ternary rectangular chirp signal. Therefore, the transmission circuit can be simplified.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a block diagram showing a configuration of an ultrasonic diagnostic apparatus according to a first embodiment of the present invention. In FIG. 1, a transmission signal generator 3 generates a frequency-modulated signal such as a chirp signal. The transmitter 2 amplifies the frequency-modulated transmission signal generated by the transmission signal generator 3 and drives the probe 1.

The probe 1 converts the electric signal sent from the transmission unit 2 into an ultrasonic signal and transmits the ultrasonic signal to the inside of a living body, receives the echo signal reflected by the living body, and converts it into an electric signal.

The receiving section 4 amplifies the received signal converted from the ultrasonic wave into the electric signal by the probe 1. The band-pass filter unit 5 filters the received signal with a filter whose band changes according to the reflection depth of the received signal. The filtered signal is subjected to detection processing by the detection unit 6, and then the DSC
The image data is converted into image information by a (scan conversion) unit 7 and displayed on a monitor 8.

The operation of the ultrasonic diagnostic apparatus configured as described above will be described in more detail with reference to FIG.

The transmission signal generator 3 generates a chirp signal as shown in FIG. This is transmitted from the probe 1 into the living body, and the signal reflected by the living body is received. At this time, in the living body, the higher the frequency component, the larger the attenuation factor, and the farther the distance, the greater the attenuation factor. Therefore, the received signal reflected at a short distance has a waveform similar to the transmission waveform as shown in FIG. The received signal reflected by the above becomes more attenuated as the high frequency component becomes, and becomes a signal as shown in FIG.

Therefore, the band-pass filter unit 5 uses a band-pass filter having a relatively high frequency for a signal reflected at a short distance and a band-pass filter having a relatively low frequency for a signal reflected at a long distance. Filter.

As shown in FIG. 2D, a high-resolution image can be obtained using a high-frequency component having a short wavelength at a short distance as shown in FIG. 2D, and little attenuation at a long distance as shown in FIG. 2E. Sensitivity can be improved using low frequency components.

The waveform generated by the transmission signal generator 3 is not limited to a linear up-chirp signal as shown in FIG. 2, but any frequency-modulated signal can be used.

In particular, a nonlinear up-chirp signal whose instantaneous frequency change rate increases as the instantaneous frequency increases as shown in FIG. 3, and a nonlinear down-chirp signal whose instantaneous frequency change rate decreases as the instantaneous frequency decreases as shown in FIG. The signal is preferable in that the energy can be concentrated on the low-frequency component, so that the sensitivity in a long-distance region can be further increased.

A binary rectangular chirp signal as shown in FIG. 5 and a ternary rectangular chirp signal as shown in FIG. 6 can simplify the circuit configuration of the transmission signal generator 3 and the transmitter 2. It is preferred in that respect.

It is preferable to freely change the amplitude of the transmission signal in that the energy can be changed for each instantaneous frequency.

(Second Embodiment) FIG. 7 shows a configuration around a transmission section 2 of an ultrasonic diagnostic apparatus according to a second embodiment of the present invention. The overall configuration block diagram of the ultrasonic diagnostic apparatus is the same as that of FIG. 1, and the parts having the same functions and operations as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 7 shows a power supply line for supplying power to the transmission unit 2.
As shown in FIG. 7, a resistor 11 is inserted in series and a capacitor 12 is inserted in parallel. The internal circuit of the transmission unit 2 is, for example, a circuit as shown in FIG.
The circuit configuration is such that power is consumed only when the probe 1 is driven.

The operation of the ultrasonic diagnostic apparatus configured as described above will be described in more detail with reference to FIG.

The transmission signal generator 3 generates a rectangular up-chirp signal as shown in FIG. When this is input to the transmission unit 2, the output transmission waveform becomes as shown in FIG. 9B from the relationship between the input impedance of the resistor 11 and the capacitor 12 inserted into the power supply line and the probe as a load.

Such a waveform is transmitted from the probe 1 into a living body, and a signal reflected at a short distance is subjected to a bandpass filter having a relatively high frequency at a long distance as in the first embodiment. The reflected signal is filtered using a relatively low bandpass filter for imaging.

At this time, since echoes from a long distance have a large attenuation, large energy is required to obtain sufficient sensitivity. However, echoes from a short distance have a small attenuation, so that a high-frequency region with a small energy is used. Even when used, sufficient sensitivity can be obtained.

Therefore, by using the driving waveform as shown in FIG. 9B, a good image can be efficiently obtained from a short distance to a long distance.

The waveform generated by the transmission signal generator 3 is not limited to a rectangular up-chirp signal as shown in FIG. 9, but may be any frequency-modulated signal.

Further, when the power supply capability of the power supply is low, the same effect can be obtained without the resistor 11.

[0038]

As described above, the present invention transmits a frequency-modulated ultrasonic signal to a living body, receives the echo signal,
The received signal is filtered by a band-pass filter whose passing frequency band becomes lower as the receiving depth becomes deeper, so that a special circuit for calculating a cross-correlation is not required, so that a short-range signal can be obtained. Therefore, it is possible to obtain an ultrasonic diagnostic apparatus which has high resolution and good sensitivity at a long distance, and can improve both sensitivity and resolution.

[Brief description of the drawings]

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

FIG. 2 is a diagram for explaining the operation of the ultrasonic diagnostic apparatus according to the first embodiment of the present invention;

FIG. 3 is a diagram showing a waveform of a non-linear up-chirp signal generated by a transmission signal generator according to the first embodiment of the present invention;

FIG. 4 is a diagram showing a waveform of a nonlinear down-chirp signal generated by a transmission signal generator according to the first embodiment of the present invention;

FIG. 5 is a diagram showing a waveform of a binary rectangular chirp signal generated by a transmission signal generation unit according to the first embodiment of the present invention;

FIG. 6 is a diagram showing a waveform of a ternary rectangular chirp signal generated by a transmission signal generation unit according to the first embodiment of the present invention;

FIG. 7 is a diagram illustrating a configuration of a peripheral part of a transmission unit of an ultrasonic diagnostic apparatus according to a second embodiment of the present invention;

FIG. 8 is a diagram showing a configuration of a transmission unit when generating a ternary signal of the ultrasonic diagnostic apparatus according to the second embodiment of the present invention;

FIG. 9 is a diagram illustrating a waveform of a ternary rectangular chirp signal generated by a transmission signal generation unit according to the second embodiment of the present invention;

FIG. 10 is a block diagram showing a configuration of a conventional ultrasonic diagnostic apparatus using an encoded transmission method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 probe 2 transmission unit 3 transmission signal generation unit 4 reception unit 5 BPF unit 6 detection unit 7 DSC (scan conversion) unit 8 monitor 9 control unit 10 correlation operation unit 11 resistor 12 capacitor

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nao Hagiwara 4-3-1 Tsunashima Higashi, Kohoku-ku, Yokohama-shi, Kanagawa Prefecture F-term in Matsushita Communication Industrial Co., Ltd. 4C301 EE06 EE15 HH01 HH43

Claims (10)

[Claims] 1. A method of transmitting a frequency-modulated ultrasonic signal to a living body, receiving an echo signal of the ultrasonic signal, and filtering the received signal with a band-pass filter having a lower passing frequency band as a receiving depth becomes deeper. A featured ultrasonic imaging method. 2. The frequency-modulated ultrasonic signal is an up-chirp signal in which the instantaneous frequency change rate increases as the instantaneous frequency increases, or the instantaneous frequency change rate decreases as the instantaneous frequency decreases. The ultrasonic imaging method according to claim 1, wherein the signal is a down-chirp signal. 3. The frequency-modulated ultrasonic signal is an amplitude-modulated chirp signal.
Or the ultrasonic imaging method according to 2. 4. The frequency-modulated ultrasonic signal is an up-chirp signal whose amplitude decreases as the instantaneous frequency increases, or a down-chirp signal whose amplitude increases as the instantaneous frequency decreases. 4. The ultrasonic imaging method according to claim 1, wherein: 5. The ultrasonic imaging method according to claim 1, wherein the frequency-modulated ultrasonic signal is a binary or ternary rectangular chirp signal. 6. A probe for transmitting and receiving ultrasonic waves, a transmission signal generator for generating a frequency-modulated probe drive signal, and a transmitter for amplifying the probe drive signal and driving the probe. A receiving unit that amplifies the received signal, and a band-pass filter unit that changes the pass frequency band according to the reception depth, transmits the frequency-modulated ultrasonic signal to the living body, receives the echo signal, and receives An ultrasonic diagnostic apparatus characterized in that a signal is filtered by a band-pass filter whose passing frequency band becomes lower as the receiving depth becomes deeper. 7. The frequency-modulated ultrasonic signal is an up-chirp signal in which the instantaneous frequency change rate increases as the instantaneous frequency increases, or the instantaneous frequency change rate decreases as the instantaneous frequency decreases. The ultrasonic diagnostic apparatus according to claim 6, wherein the signal is a down-chirp signal. 8. The frequency-modulated ultrasonic signal is an amplitude-modulated chirp signal.
Or the ultrasonic diagnostic apparatus according to 7. 9. A resistor is inserted in series with a power supply line for supplying power to the transmission unit, and a capacitor is inserted in parallel. The amplitude of the frequency-modulated ultrasonic signal decreases as the instantaneous frequency increases. 9. The ultrasonic diagnostic apparatus according to claim 6, wherein the signal is an up-chirp signal. 10. The frequency-modulated ultrasonic signal is 2
The ultrasonic diagnostic apparatus according to any one of claims 6 to 9, wherein the ultrasonic diagnostic apparatus is a value or a ternary rectangular chirp signal.