JPS60222040A - Continuous 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] [Technical Field of the Invention] The present invention relates to a continuous ultrasound Doppler device that obtains blood flow information, etc. of a subject using the continuous wave Doppler method, and particularly relates to a continuous ultrasound Doppler device that uses the same transducer to transmit and receive continuous ultrasound waves. Concerning what you do.

[Technical background of the invention and its problems] Doppler methods for obtaining blood flow information include a modulated wave Doppler method using modulated ultrasound waves and a continuous wave Doppler method using continuous ultrasound waves.

In the modulated wave Doppler method, the same transducer can be used for transmitting and receiving modulated ultrasound waves, but there is a theoretical limit to the blood flow velocity detection range. This is because, in principle, it is only possible to accurately detect frequency deviations up to half the repetition frequency of ultrasonic pulses. On the other hand, in the continuous wave Doppler method, in principle it is possible to detect frequency deviations up to half of the ultrasonic frequency, so in practice there is no limit to the detection range as mentioned above. It is necessary to use separate transducers for each purpose, and there are problems with the shape, operability, cost, etc. of the ultrasonic probe that houses the transducers.

In recent years, in the continuous wave Doppler method, attempts have been made to transmit and receive continuous ultrasonic waves using the same transducer, but the circuit configuration becomes complicated and it has not been possible to use Ci! , which made it extremely difficult to put it into practical use. The level ratio between the transmitted continuous ultrasound and the received continuous ultrasound is usually 60 dB or more,
This is because it has not always been easy to simplify the receiving circuit due to problems such as the occurrence of crosstalk between continuous ultrasonic waves.

[Object of the Invention] The present invention has been made in view of the above circumstances, and provides a continuous ultrasonic Doppler device that can transmit and receive continuous ultrasonic waves using the same transducer with an inexpensive and practical configuration. The purpose is to provide.

[Summary of the Invention] The outline of the present invention for achieving the above object is to provide a transducer that transmits continuous ultrasonic waves toward a subject and receives reflected waves of the continuous ultrasonic waves from the subject. , a continuous ultrasound system having a transmitting section that drives the transducer at an ultrasonic frequency, and a receiving section that receives ultrasound information of the subject via the transducer and obtains Doppler information of the subject. The sonic Doppler device is characterized in that a narrowband carrier filter whose center frequency is the ultrasonic frequency in the transmitter is provided at the first stage of the receiver.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a continuous ultrasonic Doppler apparatus according to an embodiment of the present invention. 1 is an oscillation circuit that generates a continuous rectangular wave signal (for example, constant 2.4 MHz); 2 is a bandpass filter that passes only the fundamental frequency component from among the continuous rectangular signal components generated by the oscillation circuit 1; 3 is a first amplifier that amplifies the fundamental wave signal that has passed through the bandpass filter 2; 4 is a vibrator. This transducer 4 is driven by an ultrasonic signal output from the first amplifier 3, and transmits continuous ultrasonic waves toward a subject (not shown), and also receives reflected waves of the continuous ultrasonic waves from the subject. receive waves.

Therefore, the electrodes 4a and 4b of this vibrator 4 receive an ultrasonic signal for transmission (hereinafter also referred to as "transmission carrier 7") and an ultrasonic signal (hereinafter referred to as "transmission carrier 7") resulting from received reflected waves. (also referred to as an "echo signal") will be superimposed.

Note that, including the oscillation circuit 1, bandpass filter 2, and first amplifier 3, the vibrator 4 is operated at an ultrasonic frequency (
For example, the transmitter 17 is configured to be driven at 2.4MH7).

Further, 5 is a narrow band rejection filter that attenuates the transmission carrier component in the ultrasonic signal component between the electric waves 4a and 4b of the vibrator 4, and is configured to include, for example, a crystal oscillator or ceramic.

The narrowband rejection filter 5 preferably has a high Q characteristic, such as a response of -40 dB at a center frequency of 2.4 MHz and an attenuation band of 300 Hz (-3 dB). This is to sufficiently attenuate the transmitted carrier component. Furthermore, 6 is a second amplifier (amplifier) that amplifies the output (Any1-signal) of the narrow band rejection filter 5, and 7 is a phase detector that performs phase detection. The device includes a mixer that mixes the ultrasonic signal outputted from the second amplifier with the ultrasonic signal outputted from the second amplifier. Reference numeral 8 denotes a bandpass filter, which extracts a frequency difference component between the transmission carrier and the echo signal, that is, a Doppler signal, from the output of the phase detector 7. 9
is a frequency analyzer that inputs the Doppler signal extracted by the band-pass filter 8 and performs frequency analysis to obtain Doppler information used for diagnosis, such as blood flow information of a subject (not shown).

Note that the narrow band rejection filter 5 and the second amplifier 6
includes the phase detector 7, the bandpass filter 8, and the frequency analyzer 9, and receives ultrasonic information of a subject (not shown) via the transducer 4, and A receiving unit 18 is configured to obtain Doppler information.

Next, the operation of the apparatus configured as described above will be explained. The rectangular wave signal generated by the oscillation circuit 1 passes through a bandpass filter 2 to remove components higher than the second harmonic, and is input as a sine wave signal to a first amplifier 3 where it is amplified. The transducer 4 is driven by the sine wave signal amplified by the first amplifier 3, and continuous ultrasonic waves are transmitted toward a subject (not shown). The continuous ultrasound reflected waves from the subject are received by the transducer 4, converted into electrical signals, and then input to the narrow band rejection filter 5 together with the transmission carrier. Only the echo signal component passes through the narrowband rejection filter 5, and the transmitted carrier component is blocked (largely attenuated). Strictly speaking,
What is attenuated by the narrow band rejection filter 5 includes not only the transmitted carrier component but also the echo signal component from the low-velocity reflection source (including a fixed reflection source). However, in the continuous wave Doppler method, the purpose is to know the maximum doppler radiant, and there is no particular problem even if a low Doppler shift, that is, velocity information of a low velocity reflection source cannot be obtained.

Note that the signal passed through the narrowband rejection filter 5 is amplified by the second amplifier 6, and then passed through the phase detector 7.
．． A Doppler signal is extracted by passing through a bandpass filter 8, and the extracted Doppler signal is further input to a frequency analyzer 9 and subjected to frequency analysis.

Although one embodiment of the present invention has been described above, it goes without saying that the present invention is not limited to the above embodiment, and can be modified as appropriate within the scope of the gist of the present invention. An example of this will be described below.

As the Q of the narrowband rejection filter shown in FIG. 1 is increased, the stability of the oscillation frequency of the oscillation circuit 1 is important. This is because if the oscillation frequency does not match the center frequency of the narrowband filter 5, the narrowband filter 5
This is because it becomes difficult to sufficiently attenuate the transmission carrier. Therefore, it is preferable to configure the oscillation circuit 1 so that the oscillation frequency can be finely adjusted. Figure 2 is an example of a variable frequency oscillation circuit, where 10 is a crystal oscillator, 11 is a variable capacitor, 12 is a C-MOS or T'TL gate, 13 is a resistor, 14 is a capacitor,
15 is a frequency dividing circuit. That is, stable oscillation is performed by the multivibrator 16 including the crystal oscillator 10,
The frequency is divided by a frequency dividing circuit 15. The constants of each element are determined so that the output frequency of this frequency dividing circuit 15 coincides with the center frequency of the narrow band nolter. By configuring the oscillation circuit 1 in this way, an ultrasonic signal with a stable frequency can be obtained,
And by changing the capacity of the variable capacitor 11,
Fine adjustment of the oscillation frequency becomes possible.

Furthermore, it is also possible to incorporate the apparatus according to the present invention into a so-called electronic scanning diagnostic apparatus that obtains a tomographic image of a subject using a transducer group consisting of a plurality of ultrasonic transducers arranged in an array. In this case as well, the group of transducers can be used for transmitting and receiving continuous ultrasonic waves. In this regard, the prior art required separate transducers for transmission and reception;
It was necessary to include the transducer group and at least one continuous ultrasound transducer.

In FIG. 1, the narrow band rejection filter 5 is placed before the second amplifier 6. This again blocks the transmitted carrier component in the stage before the second amplifier 6, prevents the second amplifier 6 from becoming saturated due to the mixing of the transmitted carrier, and obtains sufficient gain for the echo signal. It's for a reason.

In this sense, it is preferable that the narrowband filter 5 is placed at the first stage of the receiving section 18, particularly at the front stage of an electric circuit having an amplification function (for example, the second amplifier 6).

[Name of the Invention 1 According to the present invention described above, the following effects can be achieved.

Since the transmitting carrier component that enters the receiving section can be easily blocked by the narrowband blocking noiler placed at the first stage of the receiving section, continuous ultrasonic wave transmission and reception can be performed using the same transducer with a simple configuration. be able to. As a result,
Shape, operability, and = of the ultrasonic probe that houses the transducer
This is extremely advantageous in first strokes, etc.

Therefore, it is possible to provide a continuous ultrasonic Doppler device that can transmit and receive continuous ultrasonic waves using the same transducer with an inexpensive and practical configuration.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a continuous ultrasound Doppler device that is an embodiment of the present invention, and FIG. 2 is a circuit diagram for explaining a modification of the device shown in FIG. 1. 4... Vibrator, 5... Narrow band rejection filter, 17... Transmission unit, 18...
Receiving section.

Claims (1)

[Claims] a transducer that transmits continuous ultrasonic waves toward a subject and receives reflected waves of the continuous ultrasonic waves from the subject; a transmitter that drives the transducer at an ultrasonic frequency; In a continuous ultrasound Doppler apparatus having a receiving section that receives ultrasound information of the subject via the transducer and obtains Doppler information of the subject, the ultrasound frequency in the transmitting section is set as a center frequency. 1. A continuous ultrasound Doppler device, characterized in that a narrowband carrier filter is provided at the first stage of the receiving section.