JPS6395037A - Ultrasonic pulse doppler apparatus - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is an ultrasonic pulsed Doppler device, in particular, analyzes Doppler received signals subjected to the Doppler effect from an in-vivo moving part, and displays an image of the state of movement inside the subject. This invention relates to an ultrasonic pulsed Doppler device.

[Prior art] By transmitting an ultrasonic pulse beam into a subject and measuring the Doppler shift information of the reflected echo from a moving part within the subject, it is possible to detect the movement of a reflecting body of a moving part, such as the heart. Doppler devices that measure velocity are well known.

In this device, the received Doppler signal is time gated so that only information at a predetermined distance (in the depth direction) within the subject is extracted. This conventional gating method is performed as follows.

In other words, an ultrasonic pulse beam is transmitted into the subject, and an ultrasound signal that undergoes a Doppler shift due to a moving target within the subject, that is, a moving reflector, is received.This signal is demodulated and subjected to the Doppler shift. Only the frequency is extracted and then fed to the gating circuit.

In this gate circuit, the gate opens only for several microseconds at a time phase corresponding to a set depth (distance), and only the Doppler reception signal passing through the gate at this time is taken in. in this case,
Since the repetition period of the gate is very long compared to the gate length, the power of the signal taken in per unit time is very small, and the Doppler received signal has a poor S/N ratio. Therefore, in order to prevent such deterioration of the S/C ratio, a hold circuit is used, and the hold circuit holds the held signal component only while the gate is open.

However, simply applying a hold to the Doppler received signal only emphasizes the signal at the moment when the hold is applied, and signals in other areas within the gate are almost ignored.

Therefore, conventionally, in order to solve the above phenomenon and obtain accurate signal information, a method has been used in which the signal within the gate is integrated and held at the time phase at the end of the gate.

[Problems to be Solved by the Invention] However, an analog integrator using a resistor, a capacitor, an operational amplifier, etc. is used as an integrator that integrates the signal in the gate, and such an analog integrator According to the integrator, since there is a time constant (especially the rise time constant), the signal level existing in the gate is partially transformed and integrated, and all information (level) of the signal in the gate is There was a problem that it could not be imported as is.

For example, if the time constant is made larger than the gate length, information in front of the gate in the signal will be emphasized and information behind the gate will be weakened. On the other hand, if the time constant is made smaller than the gate length, the information of ILi'l in the gate in the signal tends to be emphasized, and the information before and after the gate tends to be weakened.

Purpose of the Invention The present invention has been made in view of the above-mentioned conventional problems.
The purpose is to provide an ultrasonic pulsed Doppler device that can extract all the information in the gate as is, regardless of the time constant of the integrator.

[Means for Solving the Problems] In order to achieve the above object, the present invention transmits an ultrasonic pulse into a subject, receives a reflected echo, demodulates the received signal, and then applies a time gate. In an ultrasonic pulse Doppler apparatus that displays the motion state of a subject by manually generating a Doppler shift signal over a predetermined distance using a gate circuit, the gate circuit has analog-to-digital conversion means for converting a received signal into a digital signal, It is characterized by adding the digital signals in the gates output from the digital conversion means.

The present invention is characterized by using analog-to-digital conversion means for converting the amplitude of the Doppler signal from the target site into a pulse number proportional to the amplitude of the Doppler signal from the target region, in place of the conventional analog integrator.

[Operation] According to the above configuration, the amplitude of the received signal supplied to the gate circuit is instantaneously converted into the number of pulses and added. Since this continues while the gate is open, all the information within the gate is taken in as is, making it possible to accurately analyze the movement speed distribution of the moving parts within the subject.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 shows a circuit configuration of a first embodiment of the present invention, in which a transmitter/receiver 12 is connected to an ultrasonic transducer 10, and the transmitter/receiver 12 receives ultrasonic waves obtained here. A demodulator 14 for demodulating the signal is connected, and this demodulator 14
Then, a Doppler received signal is extracted based on the carrier signal supplied from the carrier generator 16.

The characteristic feature of the present invention is that the Doppler reception signal output from the demodulator 14 is converted into a digital signal and taken in as it is. In the first embodiment, a high-speed analog/digital (hereinafter referred to as A/ A converter (referred to as D) is provided.

That is, the gate circuit 20 includes a high-speed A/D converter 22 that performs digital conversion at high speed, an integrator (accumulator) 24 that integrates the output of this high-speed A/D converter 22, and holds the output of this integrator 24. Latch 26 and this latch 2
and a D/A converter 28 that converts the output of 6 into an analog signal. Note that the high-speed A/D converter 22. Integrator 24° latch 26. A synchronizing signal from the synchronizing signal generator 18 is supplied to the D/A converter 28 .

A filter circuit 30 for removing noise signals, a frequency analysis section 32, and a display section 34 for displaying images such as ultrasonic tomographic images are connected to the gate circuit section 20.

The present invention has the above configuration, and its operation will be explained below.

The output from the carrier generator 16 is supplied to a synchronization signal generation section 18, and the synchronization signal generation section 18 generates a transmission trigger,
Generate gate signals, etc. and supply them to the corresponding circuits. Then, the output of the carrier generator 16 is transmitted to the transceiver 1
The transmission signals are sequentially supplied to the ultrasonic transducer 10 by a drive circuit built into the transceiver 12, and by exciting the ultrasonic transducer 10, an ultrasonic pulse beam is generated. Waves are transmitted into the subject.

The ultrasonic waves emitted into the subject in this way are reflected from within the subject, and in particular, signals subjected to a Doppler frequency shift are also converted into electrical signals by the ultrasound transducer 10. Then, after receiving a predetermined amplification at the transceiver 12,
The signal is extracted by the demodulator 14 as a signal having only the Doppler shift frequency, and is supplied to a gate circuit 20 for extracting a signal of a specific region within the subject.

This gate circuit 20 takes in data by opening the gate at a time phase that lags behind the transmission trigger by the reciprocating propagation time within the subject of the ultrasonic wave corresponding to the set measurement depth. That is, the amplitude information of the Doppler reception signal supplied to the gate circuit 20 is first instantaneously digitized by the high-speed A/D converter 22, and then all the data during the period when the gate is open is digitized by the integrator 24. Accumulated. and,
This accumulated value is latched by the latch 26 in the phase when the gate is closed. The output of this latch 26 is sent to the D/A converter 2.
At step 8, the signal is converted to analog again.

Therefore, the Doppler received signal is returned to the original analog signal, but it is also possible to perform subsequent signal processing as a digital signal.

The Doppler received signal at a predetermined distance obtained in this way does not become an integrated signal of deformation information like that obtained with a conventional analog integrator, but is a signal as it is without input variation at each point within the gate. becomes. Therefore, regardless of whether the gate width is wide or narrow, signals can be taken in in a uniform input state, and it is possible to obtain a Doppler received signal with no variation in sensitivity within the gate and a good S/N ratio.

The output signal of this gate circuit section 20 is filtered by a filter circuit 30 to remove unnecessary high and low frequency components, and then sent to a frequency analysis section 32.
An analysis of the amount of Doppler shift is performed, and the state of movement within the subject is displayed on the display unit 34.

Next, a second embodiment of the present invention will be described based on FIG. 2.

A characteristic feature of the second embodiment is that the analog-to-digital conversion means consists of a voltage-frequency converter (V-F converter), and in the figure, the gate circuit 20 converts the signal voltage into a frequency. -F converter 36, a counter 38 that counts frequencies, a latch 26, and a D/A converter 28.

Therefore, the amplitude information of the Doppler reception signal supplied to the gate circuit 20 is converted into frequency information by the V-F converter 36, and the frequency information while the gate is open is integrated by the next stage counter 38. Ru.

Then, in the phase when the gate is closed, the latch 26 is latched, thereby converting the Doppler reception signal, which was an analog signal, into a digital signal.

Note that, as described above, it is also possible to directly supply the digital signal that is the output of the latch 26 to the filter circuit 30. In this case, the filter circuit 30 may be configured with a digital circuit, and thereby the D/ A converter 28
can be omitted, and all signal processing after the demodulator 14 can be digitally processed.

[Effects of the Invention] As explained above, according to the present invention, the analog-to-digital conversion means is provided in the gate circuit section to digitize and process the Doppler received signal, so that any period during which the gate is open is There is no input variation in the signal at the point , the signal to be frequency analyzed can be accurately integrated as it is, and a highly accurate Doppler signal with an improved SIN ratio can be obtained. As a result, it is possible to accurately display an image of the moving state of the moving part within the subject, and it is possible to provide information useful for image diagnosis.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a circuit configuration of a first preferred embodiment of the present invention, and FIG. 2 is a block diagram showing a circuit configuration of a second embodiment. 10... Ultrasonic transducer 12...
Transmitter/receiver 14...Demodulator 20...Gate circuit 22...High speed A/D converter 24...Integrator 26...Latch 28...D/A converter 36...V- F converter 38... Counter.

Claims (3)

[Claims] (1) Transmit an ultrasound pulse into the subject, receive the reflected echo, demodulate the received signal, and then apply a time gate to input a Doppler shift signal over a predetermined distance using a gate circuit to generate movement within the subject. In the ultrasonic pulsed Doppler device that displays a state, the gate circuit has an analog-to-digital conversion means for converting a received signal into a digital signal, and adds the digital signals in the gate output from the analog-to-digital conversion means. Ultrasonic pulsed Doppler device. (2) The apparatus according to claim (1), characterized in that the analog-to-digital conversion means comprises a high-speed analog-to-digital converter, and the outputs of the analog-to-digital converter are added together by an integrator. Device. (3) In the device according to claim (1), the analog-to-digital conversion means comprises a voltage-frequency converter,
An ultrasonic pulse Doppler apparatus characterized in that the outputs of this voltage-frequency converter are added by a digital counter.