JPH0324859B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic Doppler measurement device, and particularly to an ultrasonic Doppler measurement device for accurately displaying an image of the velocity of a moving part from a Doppler received signal.

[Prior art] Images of moving parts are displayed by processing Doppler reception signals obtained from within a living body, and as is well known, the reception signals obtained by being reflected from movement reflectors are Doppler polarized. The movement of the moving part can be determined by measuring the amount of Doppler shift.

Figure 3 shows the circuit block of the receiving section in a conventional general measuring device.
After the reflected echo received at 0 is amplified by an amplifier 12, only the Doppler shift signal necessary for velocity calculation is extracted.

That is, the amplifier 12 outputs a signal of ω0 + Δω including the Doppler shift component Δω, and this signal is converted into multiple signals by the orthogonal detectors 14a and 14b, and when multiplied by sinω0 and cosω0, The quadrature detector 14a outputs a signal corresponding to the real part I, and the quadrature detector 14b outputs a signal corresponding to the imaginary part Q.

These multiple signals are then passed through a high-pass filter 16.
a, 16b, only the Doppler shift component Δω is taken out, and further low-pass filters 18a, 18b.
Excess signals are removed, and the Doppler signal output from the low-pass filter 18 is subjected to calculation of the Doppler shift amount in the signal processing section 20.

[Problems to be Solved by the Invention] Problems of the Prior Art By the way, in the conventional apparatus, the Doppler signal in the low-velocity portion may be somewhat removed by the high-pass filters 16a and 16b, but generally the The problem is that it is difficult to accurately measure low speeds.

That is, the Doppler frequency Δf indicating the amount of Doppler shift can be expressed by the following equation, where v is the velocity of the object to be measured, c is the speed of sound, and fo is the ultrasound frequency.

Δf=2v・fo/c...(1) According to equation (1), when the flow velocity v of the object to be measured, such as blood flow, is slow, or when the ultrasonic frequency fo is small, the Doppler frequency Δf becomes smaller;
In this case, speed detection is relatively difficult.

Moreover, as mentioned above, the high-pass filter 16a,
16b, some signals in the low speed portion are discarded. Therefore, it is conceivable to lower the cutoff value of the high-pass filter 16 in order to obtain low-speed Doppler signal information, but this has the disadvantage that speeds other than low speeds cannot be detected sufficiently.

OBJECT OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide an ultra-high-speed ultrasonic wave that can efficiently and accurately measure the low speed of a moving part without lowering the cut-off value of the high-pass filter. An object of the present invention is to provide a sonic Doppler measuring device.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an ultrasound system that measures and displays moving parts based on a Doppler reception signal obtained from ultrasound emitted into a living body. The Doppler measuring device includes a frequency converting means for converting the frequency of the Doppler received signal to a predetermined times, and the frequency converting means changes the conversion magnification in response to a change in the transmission frequency of the ultrasound emitted into the living body. [Operation] According to the above configuration, the frequency of the Doppler received signal obtained from within the living body is multiplied by a predetermined frequency by the frequency conversion means. That will happen. Therefore, it becomes possible to extract Doppler information of a low-speed moving part with high accuracy.

In addition, the frequency conversion means changes its conversion magnification depending on the transmission frequency and can process the Doppler received signal at a fixed fixed frequency, so for example, the reference frequency in orthogonal detection can be fixed, or It becomes possible to fix the frequency characteristics of the filter, and it becomes possible to accurately obtain Doppler information from the Doppler received signal regardless of the transmission frequency.

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

FIG. 1 shows the circuit configuration of the receiving section of the ultrasonic Doppler measuring device, and the same members as those in the conventional device are given the same reference numerals and the explanation thereof will be omitted.

A characteristic feature of the present invention is that the frequency of the Doppler received signal obtained from within the living body is multiplied by a predetermined value, and FIG. 1 shows a frequency multiplier as a frequency conversion means for increasing the frequency of the Doppler received signal. has been done.

In the figure, a frequency multiplier 22 is provided between an amplifier 12 and a quadrature detector 14, and the output signal of the amplifier 12 is multiplied by an integral number, n times in the embodiment. Therefore, the signal component output from the frequency multiplier 22 is n(ωo+Δω), and the Doppler signal that has passed through the high-pass filter 16 and the low-pass filter 18 has a signal component of nΔω, which is multiplied by n.

As a result, a low-speed signal that could not be detected in the past becomes a signal large enough to be measured, and the speed of the low-speed section, for example, a speed of about 10 cm/sec, can be detected satisfactorily using this signal.

FIG. 2 shows a configuration using a PLL system as the frequency conversion means. In correspondence with FIG. 1, the components shown in FIG. 2 are inserted into the frequency multiplier 22 shown in FIG.

In the figure, the closed loop of the PLL system includes a phase comparator 24, a filter 26, and a voltage controlled oscillator (VCO).
28 and a frequency divider 30. According to this circuit, if the input signal component of the phase comparator 24 is ωo + Δω, the output of the frequency divider 30 is controlled to be ωo + Δω.
If the frequency division ratio of 0 is 1/n, the signal processing section 28
The output of can be set to n(ωo+Δω).

Note that the frequency conversion means is not limited to the above two configurations, but may have a configuration that utilizes the nonlinear characteristics between the base and emitter of the transistor.

In addition, in the above explanation, the frequency conversion means is the amplifier 1.
2 and the orthogonal detector 14, but the present invention is not limited thereto, and it may be placed anywhere before the signal processing section 20, such as in the baseband section after demodulation.

By the way, when emitting ultrasonic waves into a living body, ultrasonic waves with different transmission frequencies may be used depending on the measurement depth. In such a case, by changing the magnification of the frequency conversion means according to the ultrasound frequency, the measurement standard for the Doppler shift amount after multiplication can be kept constant. For example, when using two types of ultrasound frequencies, 4MHz and 2MHz, 2M
In the case of Hz ultrasonic waves, the frequency is half that of 4MHz, so it is sufficient to double the frequency multiplier 22, while in the PLL system, the frequency divider 30 is set to 1/2n.
The purpose can be achieved by frequency division.

Using such different ultrasound waves is effective, for example, when determining accurate speeds both deep and shallow within a living body. speed measurement becomes possible.

[Effects of the Invention] As explained above, according to the present invention, before processing the Doppler received signal, the frequency of the Doppler received signal is multiplied by a predetermined value, and the Doppler received signal is converted to a fixed constant frequency. I decided to process it, so
This has the advantage that speed information of a low-speed moving part can be measured with high precision, and speed information of the movement can be stably and accurately obtained regardless of the transmission frequency.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram showing a preferred first embodiment of the ultrasonic Doppler measuring device according to the present invention, FIG. 2 is a circuit block diagram showing a second embodiment of the present invention, and FIG. 3 is a circuit block diagram showing a conventional device. FIG. 20... Signal processing unit, 22... Frequency multiplier as frequency expansion means, 24... Phase comparator, 2
6...Low pass filter, 28...Voltage control section, 30
...Frequency divider.

Claims (1)

[Claims] 1. An ultrasonic Doppler measuring device that measures and displays a moving part based on a Doppler received signal obtained from ultrasound emitted into a living body, which is equipped with a frequency conversion means for converting the frequency of the Doppler received signal to a predetermined time. , the frequency converting means changes its conversion magnification in response to a change in the transmission frequency of the ultrasonic waves emitted into the living body, and processes the Doppler received signal at a fixed constant frequency. Acoustic Doppler measurement device.