JPS62117535A - Ultrasonic doppler apparatus - Google Patents

Abstract

(57) [Summary] 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 relates to an ultrasonic Doppler device, particularly an ultrasonic Doppler device that can accurately display not only shape (shaped) tomographic images but also the velocity of moving parts within a living body. Related to sonic Doppler equipment.

[Prior Art] In order to obtain various information inside a living body, it is necessary not only to display (imaging) a tomographic image of a diagnostic region in B mode, but also to display the velocity of blood flow in a moving object such as the heart or blood vessels, and its velocity status. The Doppler received signal subjected to the Doppler effect is analyzed and displayed as an image.

Conventionally, the ultrasound waves used in this type of Doppler device include pulsed waves (PW) that are emitted at a constant repetition frequency.
Waves) or continuously emitted continuous waves (CW waves) are used, and the speed of a moving object is detected from the frequency shift of the received signal.

However, although it is possible to override the position determination of the moving i@J object using the pulse wave, there is a problem in that there is a limit to the detection speed. In other words, the detection speed depends on the pulse repetition frequency, and the lower the repetition frequency, the lower the detection speed.At a constant repetition frequency used to display the tomographic image as a B'U needle, the blood jet in the heart It has been difficult to measure high-velocity flows such as currents.

Conventionally, measurement using continuous waves has been carried out to eliminate such speed limitations.This method eliminates the detection speed limitations and allows accurate determination of the speed of a moving object. In some cases, it is impossible to determine the position of a moving object, and there are drawbacks such as echoes reflected from objects other than the moving object being measured are captured at the same time. In addition, many problems remain, such as the need for two transducers because transmission and reception are always performed, and it is difficult to realize a device using continuous waves.

Therefore, in order to make it possible to measure high-speed flows, pulses with a high repetition frequency (tight pulse repetition frequency) are used.
It has been proposed to use on[requency) waves, but according to this HP RF wave, the limit of G-speed is expanded by the repetition frequency which is higher than 2F)W waves, and high-velocity moving objects can be The image can be displayed well
，! Ru.

[Problem to be solved by the invention 1 However, in the above-mentioned FIPRF wave, in order to increase the repetition frequency for transmitting pulse waves, a second pulse wave is transmitted before the first pulse wave is returned. If this is done, multiple pulse wave reflections will be received in a mixed state, making it difficult to determine whether or not it is an anti-φ1 D- from a predetermined position, that is, from a predetermined depth distance. bawl.

This is generally referred to as Ambigi 7. It is said that the reflected echo from a certain depth distance cannot be identified, and 1f! There was a problem in that the longer the transmission/reception distance of a single multiplexed wave, the greater the angularity.

Purpose of the Invention The present invention has been made in view of the above-mentioned problems, and its purpose is to eliminate ambiguity, accurately detect the speed of a moving object using PRF waves, and detect high-velocity moving objects. An object of the present invention is to provide an ultrasonic Doppler device that can display images.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an ultrasonic system that transmits and receives pulsed ultrasonic waves and detects the speed of a moving object from the frequency shift of a reflected echo signal subjected to the Doppler effect. In a Doppler device, a high repetition pulse wave generator that generates a pulse wave with a high repetition frequency, a code wave generator that identifies pulse waves in the order of transmission and generates multiple code waves with low correlation to each other, and a pulse wave generator that generates a pulse wave with a high repetition frequency. A code wave is placed on the pulse wave for identification (if phase modulator and demodulation that demodulates the Doppler reception signal obtained by emitting identification coded ultrasound into the living body with the code wave used at the time of transmission) It is characterized by having a vessel and a .

[Operation] According to the above configuration, the I-I wave having a higher repetition frequency than the PW wave used to obtain a tomographic image for a B-mode image
P RF wave ultrasound is generated, and this HPRl: wave is
For example, ultrasonic waves transmitted in the same direction are phase-modulated by code waves in the transmission order, so! ! 1. An ultrasonic wave with an identification code attached to each return cycle is emitted. I will do it. and,
Identification-coded ultrasonic reflector] - By demodulating the signal with the same code wave used during transmission,
Only Doppler received signals at a predetermined depth distance are extracted.

In other words, if a plurality of signals are not mixed in the Doppler received signal, the signal will be affected by frequency shift. - Only signals from a given depth distance are easily filtered. On the other hand, when the Doppler received signal contains signals from different depths, the code wave uses a waveform that has little relation to phase n, for example, a waveform with different positive and negative amplitudes. Only the necessary<f signal from the depth is demodulated, and other signals are converted into signals with weak amplitude by the code wave when demodulating.

[Embodiment 1] Hereinafter, a preferred embodiment of the present invention will be described based on the drawings.

FIG. 1 shows the circuit configuration of the ultrasonic Doppler apparatus according to the present invention, in which the oscillation signal (
1-1 is supplied to the 1-I P R1 generator 12
+1P R with high repetition frequency in t”RF light generator 12
Generates F waves. This HPRF wave is a pulse wave that is repeatedly transmitted at a time cycle faster than the time at which the ultrasound waves transmitted from the ultrasound probe are reflected and returned, and is a pulse wave that forms a tomographic image in B-mode image display. It is a pulse wave with a higher repetition frequency than the wave.

The characteristic feature of the present invention is that this HPRF wave is converted into an identification code using the -F wave, which has a low correlation, and the code wave generator 14 generates the code wave for identification.
is provided, and a code wave is set in response to the output of the HPRF generator 12.

In addition, a phase modulator 1 that adds a Co-F wave to the HP RF wave
6 is provided and occurs at high repetition frequency)-
+ P In order to identify RF waves in the order in which they occur, phase modulation is performed using different code waves. Therefore, the HF'-) RF wave supplied to the probe 20 via the driver 18 is converted into a 1t, and this phase-modulated tc11P RF wave Ultrasonic waves will be emitted into the living body.

This = 1-F wave is expressed as ]-do A < 1-
=11 l-1-1-1) and code B (-1-11~
111-1> is used, and each "-F wave is made up of waveforms with as weak a correlation as possible. In this way, signals having other codes are not completely demodulated, and only the signal having the identification code to be detected is completely demodulated and extracted.

Therefore, the device of the present invention is provided with a demodulator 24 for demodulating the modulated transmission waves, and the beams reflected from within the living body are
The Doppler reception signal received by the coper 20 is supplied to the demodulator 24 via the preamplifier 22, and the Doppler reception signal (3 signals) is demodulated with the code wave used at the time of transmission.

, J'-), the code wave used for demodulation is obtained by delaying the output of the code wave generator 14 for a predetermined time using a delay device 26.

The present invention basically has the above configuration, but in order to extract only the necessary Doppler signals and perform frequency analysis, the Doppler received signal is quadrature detected and then integrated, and the integrated signal is sampled and held. There is. For this purpose, in the embodiment, a multiplier 28, 30 and a π/4 phase shifter 32 for orthogonal detection, low-pass filters (LPF) 34, 36,
Integrators 38, 40, sample and hold devices 42, 44, and further bypass filters (HPF) 46, 48,
A low pass filter (LPF) 50.52 is provided, L
The output of PF50.52 is supplied to spectrum analyzer 54.

The present invention has the above structure, and its operation will be explained based on FIGS. 2 to 5.

FIG. 2 shows signal processing in the case of phase modulation, in which (a) is an HPRF wave, and (b) is a two-cycle code wave, that is, code Δ and code B code waves.

This l(P RF wave and the code waves of -dos A and B) are phase modulated by the phase modulator 16, and as shown in (C), in the case of +1, it becomes a pulse wave as it is, and in the case of -1 In this case, it is output as an inverted pulse wave.In the example (
, 1, and 2 types of codes are used for transmission and reception, and as shown in (d), modulated waves are output from the 1st modulation depth 16 in the order of △, B, and A. be done.

FIG. 3 shows the signal processing when demodulating Doppler received signals from inside the living body. When the reflectors] - are received alternately, the frequency-shifted Doppler received signal becomes a signal as shown in (b). Then, as shown in (C), the ultrasonic Doppler received signal modulated with the code wave of code A is further multiplied by the demodulator 24 with the same code wave of code A that was used during transmission. In addition, the code wave of code B is applied to the ultrasonic Doppler reception signal modulated by code B.

As a result, the output of the demodulator 24 is a signal from which the code wave has been removed, as shown in (d), and when it is transmitted, it is "-1".
If the code wave of +1 is measured, the code wave of +1 is 1
1) If a code wave of -1 is multiplied by G, then another code wave of -1 is added and the modulation returns to a state where the modulation is canceled.

In this way, the transmitted ultrasonic wave phase-modulated by the code wave can be demodulated by further multiplying the received ultrasonic signal by the same code wave. In this case, a slight phase shift occurs during demodulation between the HPRF wave before modulation and the received wave subjected to the Doppler effect, but the ultrasonic frequency f
. is approximately 2 MHz to 10 MHz, and the Doppler frequency to be detected is 1 kHz to 20 kHz)-1 z, so this phase shift is approximately 1/100 of the Doppler frequency deviation and does not pose a problem.

Next, Fig. 4 shows the processing when two reflected echoes overlap. For example, when detecting a moving object at a deep distance, reflected echoes from a shallow distance may be mixed in. be.

In this case, when demodulating with the code wave of code A, the Doppler received signal identified by code A will be demodulated in a clean form, and the Doppler received signal identified by code B will be demodulated in a clean form. The signal modulated by the code wave of code A is further multiplied by the code wave of code A, and the code wave of code A and 8 are combined.
Since the correlation between the two code waves is weak, the multiplier output does not become an accurate demodulated wave, and is attenuated by the LPF and integration circuit at the subsequent stage.

In this way, the reflected echo signals obtained from other moving objects are reduced, and only the Doppler received signals selected by the identification code are extracted, and the pulse waves are identified in the order of transmission and have a small correlation with each other. By using code waves, only Doppler received signals at a predetermined depth and distance can be effectively extracted from mixed Doppler received signals.

Furthermore, in the embodiment, in order to more efficiently remove Doppler received signals from other moving objects, the Doppler received signals obtained from the demodulator 24 are orthogonally detected and integrated. However, in order to extract only the Doppler received signal from the target moving object, it is also possible to pass this Doppler received signal through a filter of a predetermined band.
The Doppler received signal is orthogonally detected and integrated using a reference wave, and further sampled and held to obtain a Doppler signal corresponding to the frequency shift.

In FIG. 5, the signal demodulated by the code wave of code A is shown in (a), and the Doppler received signal A1 of code A and the Doppler received signal B1 of code B are orthogonally detected,
The detected signals A and B2 as shown in (b) are loud. Then, the orthogonal detection signals A and B are integrated by 38.4
When integrated at 0, as shown in (C), the Doppler received signal for the code becomes a dead and large pulse output A3, and the Doppler received signal for the code B becomes an extremely small pulse output B3 that can be ignored. .

FIG. 6 shows the processed waveform from such orthogonal detection to obtaining a Doppler frequency shift signal, and the multiplier 2
8.30, Doppler received signal 100, reference wave signal 10
When it is multiplied by 1 and passes through the LPF 34° 36, the detected output signal 102 is folded, and this signal 102 becomes an output signal corresponding to the frequency shift which is the Doppler effect.

Therefore, by integrating this detection output signal 102, an integrated output signal 103 is obtained, and by further sampling and holding this, an S/]'' output signal 104 can be obtained. This S/('' output becomes a signal with unevenness as shown in the figure, so in order to facilitate frequency analysis, )(PF
46, 48 and l-P F2O, 52, and is converted into a smooth filter output signal 105.

This filter output signal 105 is indicative of changes in Doppler frequency deviation, which makes it possible to detect changes in the velocity of a moving object.

[Effects of the Invention] As explained above, the present invention converts pulsed ultrasound into an identification code using a plurality of code waves having a small mutual relationship.
It is possible to accurately identify only Doppler received signals from a predetermined depth distance, and it is possible to reduce ambiguity caused by transmission and reception of HP RF waves.

As a result, it is possible to eliminate the limitations of speed detection of a moving object and accurately detect and display images of high-speed waves, such as jet streams in the cardiac flow, thereby providing extremely useful information for image diagnosis.

[Brief explanation of drawings]

Fig. 1 is a circuit block diagram showing a preferred embodiment of the ultrasonic Doppler device according to the present invention, Fig. 2 is a waveform diagram illustrating phase modulation of HPRF waves, and Fig. 3 is Doppler reception obtained from within a living body. A waveform diagram explaining signal demodulation, Figure 4 is an explanatory diagram showing the processing state when two types of Doppler received signals coexist, and Figure 5 is a waveform diagram showing signal processing from quadrature detection to integration. FIG. 6 is a waveform diagram illustrating the operation from obtaining the frequency shift from the demodulated Doppler received signal. 10 ... Oscillator 12 ... HP RF wave generator 14 ... Code wave generation humidifier 16 ... Phase modulator 20 ... Probe 24 ... Demodulator 28.30 ... Multiplier 32 ... π/4 phase shifter 38.40 ... Integrator.

Claims (2)

[Claims] (1) A high-repetition pulse wave generator that generates pulse waves with a high repetition frequency in an ultrasonic Doppler device that transmits and receives pulsed ultrasound and detects the speed of a moving object from the frequency shift of a reflected echo signal subjected to the Doppler effect. a code wave generator that identifies the pulse waves in the order of transmission and generates a plurality of code waves with low correlation to each other; a phase modulator that places a code wave on the pulse wave to identify the pulse waves; and an identification code. 1. An ultrasound Doppler device comprising: a demodulator that demodulates a Doppler reception signal obtained by emitting converted ultrasound waves into a living body using a code wave used during transmission. (2) The apparatus according to claim (1), comprising: a quadrature detector that performs orthogonal detection of the Doppler received signal output from the demodulator; and an integrator that integrates the output of the quadrature detector; An ultrasonic Doppler apparatus characterized in that a Doppler received signal having an arbitrary identification code is separated from a Doppler received signal having other identification codes and extracted from the output signal thereof.