JPH05176923A - Ultrasonic diagnostic system - Google Patents

Abstract

PURPOSE:To always obtain satisfactory fidelity and S/N in the course of receiving a reflected echo signal by allowing even a high-frequency component and even a low-frequency component of the reflected echo signal to pass through by prescribed frequency band width. CONSTITUTION:By a filter means 3' constituted of a local oscillator 14 for generating a carrier wave which can vary continuously a frequency, a mixer 15 for applying a reflected echo signal from an ultrasonic transmitting/receiving part 2 and a carrier wave from the local oscillator 14 and executing a frequency conversion of its reflected echo signal, and a band pass filter 16 having a fixed frequency band for filtering an output signal from this mixer 15, a filter operation for eliminating a noise of the outside of a signal band is executed with regard to the signal outputted from the ultrasonic transmitting/receiving part 2. In such a way, even a high-frequency component and even a low-frequency component of the reflected echo signal can be allowed to pass through by prescribed frequency band width.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus for obtaining a tomographic image of a diagnostic region of a subject using ultrasonic waves, and particularly to a constant frequency band for both high and low frequency components of a reflected echo signal. The present invention relates to an ultrasonic diagnostic apparatus that passes a width and always obtains good fidelity and S / N ratio while receiving a reflected echo signal.

[0002]

2. Description of the Related Art A conventional ultrasonic diagnostic apparatus, as shown in FIG. 5, is a probe 1 which transmits and receives ultrasonic waves, and a probe 1 which drives the probe 1 to generate and receive ultrasonic waves. An ultrasonic wave transmitting / receiving unit 2 for amplifying a signal of a reflected echo, a bandpass filter 3 as a filter means for removing noise outside a signal band of a signal output from the ultrasonic wave transmitting / receiving unit 2, and this bandpass filter 3, an amplifier 4 for amplifying a signal from the amplifier 3, a detector 5 for inputting and detecting an output signal from the amplifier 4, and an image processing unit for inputting the signal from the detector 5 and processing the image for display. 6
And an image display unit 7 for inputting an output signal from the image processing unit 6 and displaying an ultrasonic tomographic image.
The ultrasonic wave transmitter / receiver 2 includes a pulser 8 that sends a drive pulse to the probe 1, and a preamplifier 9 that amplifies the reflected echo signal received by the probe 1. Further, reference numeral 10 indicates a control unit that controls the operation of each of the above components.

Here, the ultrasonic waves transmitted into the subject are
Since the higher the frequency, the greater the attenuation,
The echo signal reflected from a deeper portion has a lower signal frequency band. In such a state, if the pass band of the band pass filter 3 is gradually changed to a low band during the reception of the reflected echo signal, the pass frequency band of the echo signal returning early (reflection from a shallow portion) becomes high. However, for the echo signal returning later (reflection from a deep portion), the pass frequency band can be made lower, and S
The / N ratio can be improved. From such a thing,
In a conventional ultrasonic diagnostic apparatus, as described in Japanese Patent Publication No. 62-24094, the band pass filter 3 is a so-called dynamic that changes the pass band according to the depth during reception of a reflected echo signal. A filter was used.

As the dynamic filter, as shown in FIG. 6, a circuit in which the cathodes of the variable capacitance diodes VC ₁ and VC ₂ are commonly connected and a circuit utilizing resonance with the coil L are used. Then, while the reflected echo signal from the input terminal 11 is being received, the bias voltage to the variable capacitance diodes VC ₁ and VC ₂ is continuously changed (lowered) by the control signal from the control terminal 13 so that the variable capacitance diode can be changed. The capacitances of VC ₁ and VC ₂ were changed (increased), and the center frequency of the pass band was continuously changed (decreased).

[0005]

However, in the bandpass filter 3 including the dynamic filter as described above, the Q value indicating the sharpness of resonance changes (large) simultaneously with the change of the center frequency of the passband. The frequency pass band width also changed. That is, at a low frequency, the pass band width becomes narrow, so that a band for a required signal cannot be obtained and information is lost, and at a high frequency, the band width becomes wider than necessary, resulting in an S / N ratio.
The ratio deteriorated. Therefore, in the ultrasonic diagnostic apparatus, good fidelity and S / N ratio may not be obtained during reception of the reflected echo signal.

Therefore, the present invention addresses such a problem and allows both the high frequency component and the low frequency component of the reflected echo signal to pass with a constant frequency bandwidth so that the reflected echo signal always has good fidelity. It is an object of the present invention to provide an ultrasonic diagnostic apparatus capable of obtaining the S / N ratio with.

[0007]

In order to achieve the above object, an ultrasonic diagnostic apparatus according to the present invention includes a probe for transmitting and receiving ultrasonic waves, and driving the probe to generate ultrasonic waves. And an ultrasonic wave transmitting / receiving unit for amplifying the received reflected echo signal, a filter unit for removing noise outside the signal band of the signal output from this ultrasonic wave transmitting / receiving unit, and a signal from this filter unit are input. And an image processing unit for processing for image display, and an image display unit for displaying an ultrasonic tomographic image by inputting an output signal from the image processing unit. The means adds a local oscillator that generates a carrier wave whose frequency can be continuously changed, a reflected echo signal from the ultrasonic transmitter / receiver unit, and a carrier wave from the local oscillator to the reflected echo signal. A mixer for wavenumber conversion, which is constituted by a band-pass filter having a frequency band fixed for filtering the output signal from the mixer.

[0008]

The ultrasonic diagnostic apparatus configured as described above adds a local oscillator that generates a carrier wave whose frequency can be continuously changed, a reflected echo signal from the ultrasonic wave transmitting / receiving section, and a carrier wave from the local oscillator. Output from the ultrasonic transmitter / receiver by a filter means composed of a mixer for converting the frequency of the reflected echo signal and a bandpass filter having a fixed frequency band for filtering the output signal from the mixer. Performs a filtering operation on the signal to remove noise outside the signal band. As a result, both the high frequency component and the low frequency component of the reflected echo signal can be passed with a constant frequency bandwidth.

[0009]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention. This ultrasonic diagnostic apparatus obtains a tomographic image of a diagnostic region of a subject using ultrasonic waves, and as shown in the figure, a probe 1, an ultrasonic wave transmitting / receiving unit 2, and a filter means 3 '. , An amplifier 4, a detector 5, an image processing unit 6, and an image display unit 7.

The probe 1 is for mechanically or electronically performing linear scanning, sector scanning or the like to transmit and receive ultrasonic waves, and although not shown in the figure, it is a source of ultrasonic waves. There is also a built-in transducer that receives the reflected echo. The ultrasonic wave transmission / reception unit 2 drives the probe 1 to generate ultrasonic waves and amplifies the signal of the reflected echo received. The ultrasonic wave transmission / reception unit 2 sends a drive pulse to the probe 1 and the prober 8. A preamplifier 9 for amplifying the reflected echo signal received by the tentacle 1 is provided. Filter means 3 '
Is for removing noise outside the signal band of the signal output from the ultrasonic transmission / reception unit 2. The amplifier 4 is
The signal from the filter means 3'is amplified, and the detector 5 receives the output signal from the amplifier 4 and detects it. Further, the image processing unit 6 receives the signal from the detector 5 and performs various processes for displaying an image. Further, the image display unit 7 inputs an output signal from the image processing unit 6 and displays an ultrasonic tomographic image, and is composed of, for example, a television monitor. In FIG. 1, reference numeral 10 indicates a control unit that controls the operation of each of the above components.

In the present invention, the filter means 3'includes a local oscillator 14 for generating a carrier wave whose frequency can be continuously changed, a reflection echo signal from the ultrasonic wave transmitting / receiving section 2, and the local oscillator 14 described above. Mixer 15 for converting the frequency of the reflected echo signal by adding the carrier wave from
And a bandpass filter 16 having a fixed frequency band for filtering the output signal from the mixer 15.

An example of the concrete structure is shown in FIG.
The circuit diagram is as shown in. That is, the local oscillator 14 includes a coil 17 provided therein and variable capacitance diodes 18a and 18b whose cathodes are commonly connected.
And oscillates at a frequency determined by the voltage of the frequency control signal applied to the control terminal 13. The carrier wave signal S ₂ output from the local oscillator 14 is input to a mixer 15 using a multiplier 19, for example. Then, in the mixer 15, the sum (or difference) of the reflected echo signal S ₁ from the ultrasonic transmission / reception unit 2 input from the input terminal 11 and the signal S ₂ of the carrier wave from the local oscillator 14 is calculated, and frequency conversion is performed. The output signal S ₃ is output. This output signal S ₃ is a bandpass filter 16 having a fixed frequency band that follows.
Is input to and filtered, and a part of the frequency components of the sum component of the signals S ₁ and S ₂ is taken out as a signal S ₄ and output terminal 1
It is supposed to be output from 2.

Next, the operation of the filter means 3'constructed as described above will be described with reference to FIGS. First, as shown in FIG. 3A, the reflected echo signal S ₁ output from the ultrasonic wave transmitting / receiving unit 2 shown in FIG.
For example, the center frequency is 7.5 MHz and the frequency bandwidth is 5 to 10 MHz.
Let z. Further, the local oscillator 14 uses a voltage controlled oscillator, and its oscillation frequency range is, for example, 20 to 22.5.
Set to MHZ. Further, the bandpass filter 16 has, for example, a center frequency of 28.7 as shown in FIG.
The frequency bandwidth is 2.5 MHz at 5 MHz (passing frequency is 27.5 to 30
It is assumed that a filter fixed to (MHz) is used.

In this state, when the reflected echo of the ultrasonic wave from a relatively close portion inside the subject is received, the frequency of the carrier wave generated by the local oscillator 14 is set to 20 MHz, for example, as shown in FIG. 3 (b). .. At this time, the reflected echo signal S ₁ having a frequency band of 5 to 10 MHz as shown in FIG. 3 (a) has a frequency of 25 to 30 MHz as shown in FIG. 3 (c) by the mixer 15. Will be converted.
By inputting the frequency-converted signal S ₃ into the bandpass filter 16 having the passband shown in FIG. 3D, as shown in FIG. 3E, the output signal in the frequency band of 27.5 to 30 MHz. S ₄ is obtained. This is the above 5
The same result is obtained as the information included in the upper half of the frequency band of 7.5 to 10 MHz of the reflected echo signal S ₁ having the frequency band of to 10 MHz.

Next, when receiving the reflected echo of the ultrasonic wave from a relatively deep portion in the subject, as shown in FIG. 4B, the frequency of the carrier wave generated by the local oscillator 14 is set to a high value, for example, 22.5 MHz. To do. At this time, the reflected echo signal S ₁ having a frequency band of 5 to 7.5 MHz for deep areas as shown in FIG.
As shown in (c), the frequency is converted to the band of 27.5 to 30 MHz. This frequency-converted signal S ₃ is
By inputting into the band pass filter 16 having the pass band shown in FIG. 4 (d) (the same as the case of FIG. 3 (d)), as shown in FIG. 4 (e), the output in the frequency band of 27.5 to 30 MHz is output. The signal S ₄ is obtained. This time, 5 to 7.5 MHz above
The same result is obtained as when the information contained in the entire range of the reflected echo signal S ₁ having the frequency band of is obtained.

That is, in both cases of FIG. 3 and FIG. 4, it is possible to pass a signal with a constant frequency bandwidth of, for example, 2.5 MHz. The frequency of the carrier wave generated by the local oscillator 14 shown in FIG.
_By continuously changing ₁ during reception, the reflected echo signal S ₁ can be processed in an appropriate frequency band according to each depth of the object measurement.

[0017]

Since the present invention is constructed as described above,
A local oscillator 14 that generates a carrier wave whose frequency can be continuously changed, and a reflected echo signal S ₁ from the ultrasonic wave transmitting / receiving unit 2
A mixer 15 for adding the carrier wave (S ₂ ) from the local oscillator 14 and converting the frequency of the reflected echo signal S _1.
And a bandpass filter 16 having a fixed frequency band for filtering the output signal S ₃ from the mixer 15, by means of a filter means 3 ′. External noise can be removed. As a result, both high frequency components and low frequency components of the reflected echo signal S ₁ can be passed with a constant frequency bandwidth. As a result, good fidelity and S / N ratio can always be obtained during reception of the reflected echo signal S ₁ .

[Brief description of drawings]

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

FIG. 2 is a circuit diagram showing an example of a specific configuration of filter means,

FIG. 3 is a graph of a frequency spectrum for each signal for explaining the operation of the filter means.

FIG. 4 is a graph of a frequency spectrum of each signal for explaining the operation of the filter means,

FIG. 5 is a block diagram showing a conventional ultrasonic diagnostic apparatus,

FIG. 6 is a circuit diagram showing an internal configuration of a dynamic filter used as a bandpass filter in a conventional device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Probe, 2 ... Ultrasonic wave transmission / reception part, 3 '... Filter means, 4 ... Amplifier, 5 ... Detector, 6 ... Image processing part, 7 ... Image display part, 14 ... Local oscillator, 15 ...
Mixer, 16 ... Band pass filter, S ₁ ... Reflected echo signal, S ₂ ... Carrier signal, S ₃ ... Frequency converted signal, S ₄ ... Output signal.

Claims (1)

[Claims] 1. A probe for transmitting and receiving ultrasonic waves, an ultrasonic wave transmitting / receiving unit for driving the probe to generate ultrasonic waves and amplifying a signal of a reflected echo received, and the ultrasonic wave transmitting / receiving unit. Filter unit for removing noise outside the signal band of the signal output from the unit, an image processing unit that inputs the signal from the filter unit and processes it for image display, and an output from the image processing unit In an ultrasonic diagnostic apparatus comprising an image display unit for inputting a signal to display an ultrasonic tomographic image, the filter means is a local oscillator that generates a carrier wave whose frequency can be continuously changed,
A mixer for adding a reflected echo signal from the ultrasonic wave transmitting / receiving unit and a carrier wave from the local oscillator to convert the frequency of the reflected echo signal, and a fixed frequency band for filtering an output signal from the mixer An ultrasonic diagnostic apparatus comprising a bandpass filter.