JP3048691B2 - Ultrasound diagnostic equipment - Google Patents

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,
In particular, the present invention relates to an ultrasonic diagnostic apparatus which prevents generation of noise in a color Doppler mode.

[0002]

2. Description of the Related Art An ultrasonic diagnostic apparatus irradiates an ultrasonic signal into an object from an ultrasonic probe and receives signals reflected from a tissue or a lesion in the object with the ultrasonic probe. This is a device for displaying a tomographic image formed by a wave and its reflected signal on a CRT for use in diagnosis.

When an ultrasonic wave is applied to a living body, the ultrasonic wave is absorbed or scattered or reflected at various places. The scattered reflected wave contains information on the difference in acoustic impedance at the boundary and information on the moving speed of the scatterer. The scattering intensity reflects the difference in acoustic impedance, and the amount of frequency shift due to the Doppler effect reflects the speed of movement.

FIG. 3 shows a block diagram of a data processing unit from the beamformer of the conventional ultrasonic diagnostic apparatus having a color flow mapping function applied to Doppler until obtaining the average velocity and velocity dispersion of blood flow. The signal subjected to phasing and addition by the beamformer 1 is subjected to quadrature detection by the mixer 2 and separated into an in-phase (i) signal and a quadrature (q) signal and output.

The i signal is a programmable gain amplifier A3
And is converted into a digital signal by the AD converter A5. The q signal is likewise programmable gain amplifier B4
And is converted into a digital signal by the AD converter B6. These programmable gain amplifiers A3 and B4
Manually adjusts the gain so that the input signal levels to the A / D converters A5 and B6 are at appropriate levels for A / D conversion.

The output digital signal of the AD converter A5 is M
It is input to TIA9. Since the MTI has the characteristics of a high-pass filter, data from a slow reflector other than the blood flow is deleted, and only the data of the moving target is output.

[0007] The q signal is similarly processed, and the data of the moving target is output from the MTIB 10. MTIA9 and MTI
The output signal of B10 is input to the autocorrelator 11. Autocorrelator 11 performs a correlation operation on i signal and q signal input, and outputs the rate of dispersion within the averaging time and the mean value of the shift frequency f _d by the Doppler effect. Based on this output, the direction, average velocity and velocity dispersion of the blood flow are displayed in color on the B-mode image.

[0008]

In this apparatus, the input ranges of the AD converters A5 and B6 are finite. Therefore, when a clutter signal having an amplitude larger than the maximum allowable input range of the AD converter is input to the AD converter, the output of the portion having the amplitude larger than the maximum allowable input range is clipped.

FIG. 4 is a diagram showing the relationship between the clutter signal input to the AD converter and the output of the AD converter. The output is a digital value, but is shown as an analog signal for convenience of explanation. (A) is a diagram showing a clutter signal input to the AD converter. The upper diagram shows the relationship between the maximum input range of the AD converter and the clutter signal 12 which is an input signal having a frequency of f _e , and the lower diagram shows Indicates the spectrum of the frequency.

FIG. 2B shows the output of the AD converter.
You can see that the part exceeding the maximum allowable input range is clipped. For this reason, the output spectrum contains many odd harmonics as shown in the figure below. This signal is MT
When input to the processing unit after IA9 and MTIB10, the harmonic components are regarded as blood flow components and processed. In color flow mapping, there is no blood flow, but there is a strong echo object and the color is displayed as moving.

Therefore, as described above, the programmable gain amplifiers A3 and B3 are controlled so that the amplitude of the clutter signal falls within the maximum allowable input range of the AD converters A5 and B6.
Although the gain of 4 is adjusted, if the ratio of the amplitude of the clutter signal to the amplitude of the signal due to blood flow is large, the signal due to the required blood flow becomes too small and the error in the average velocity and velocity dispersion becomes large. Would.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object the purpose of obtaining noise due to color Doppler when obtaining a signal due to a blood flow at a level necessary for detection even when a large-amplitude clutter signal is input. It is an object of the present invention to realize an ultrasonic diagnostic apparatus having a color Doppler function which does not generate an image and does not color an image by an echo from a fixed target.

[0013]

According to the present invention, there is provided an ultrasonic diagnostic apparatus having a color Doppler function, which is provided at a stage subsequent to a beamformer for phasing and adding a received signal, and which is included in the received signal. A programmable level limiter for clipping the level clutter signal at a constant level, a filter for removing at least a harmonic component provided at a stage subsequent to a mixer for quadrature detection of the received signal, and a level of an output signal of the filter. A programmable gain amplifier for amplifying the signal to a level not exceeding the maximum allowable input level of the AD converter, and a controller for setting a clip level of the programmable level limiter and a gain of the programmable gain amplifier. Things.

[0014]

The received signal input from the beamformer is clipped by a programmable level limiter at a level determined by a controller, and quadrature detection is performed by a mixer. The frequency components of the sum of the harmonics and the carrier frequency included in the two signals obtained are removed by filters, respectively, and controlled by a controller in a programmable gain amplifier to amplify to an amplitude not exceeding the maximum allowable input level of the AD converter. Input to the AD converter.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention. In the figure, the same parts as those in FIG. 3 are denoted by the same reference numerals. In the figure, reference numeral 21 denotes a programmable level limiter which clips the amplitude of an input signal output from the beam former 1 at a certain amplitude. The amplitude value to be clipped is set by a signal from the controller 22. Clipping is performed as shown in FIG. 4A is a waveform diagram of a clutter signal 12 as an input signal, and FIG. 4B is a waveform diagram of an output signal of the programmable level limiter 21 clipped at a clip level 23 set by the programmable level limiter 21. is there.

Reference numeral 24 denotes a low-pass filter (hereinafter, referred to as LPF) A for removing higher harmonic components having a clipped waveform shown in FIG. This may be a bandpass filter that passes the frequency _fe shown in FIG.

Reference numerals 25 and 26 denote mixers which perform quadrature detection based on output signals of a carrier oscillator 27 and a 90 ° phase shifter 28 in the same manner as the mixer 2 shown in FIG. 3, and reference numeral 25 denotes a mixer A which outputs an i signal; A mixer B that outputs a signal.

Reference numeral 29 denotes an LPFB that removes high-frequency components from the output of the mixer A25, and reference numeral 30 denotes an LPFC that removes high-frequency components from the output of the mixer B26. The controller 22 sets the clip level of the programmable level limiter 21 and the gains of the programmable gain amplifiers A3 and B4.

Next, the operation of the embodiment will be described. The received signal subjected to the phasing addition by the beamformer 1 is input to a programmable level limiter 21 and clips the amplitude equal to or higher than the level set by the controller 22 as shown in FIG. The harmonic generated by clipping is LPFA2
Removed at 4.

The output of the LPFA 24 is mixed with the carrier of the output of the carrier oscillator 27 in the mixer A 25, detected and output as an i signal. The output of the LPFA 24 is the 90 ° of the output of the 90 ° phase shifter 28 in the mixer B25.
It is mixed with the phase-shifted carrier wave, detected, and output as a q signal.

The LPFB 29 removes the high frequency component of the i signal and outputs it. The LPFC 30 removes the high frequency component of the q signal and outputs the result. The output signal of the LPFB 29 is amplified by the programmable gain amplifier A3, and the gain is controlled by the controller 22 so as to be within the maximum allowable input level of the next-stage AD converter A5.
The output signal of the LPFC 30 is amplified by the gain under the control of the controller 22 in the programmable gain amplifier B4, similarly to the programmable gain amplifier A.

The output signal of the programmable gain amplifier A3 is converted into a digital signal by an AD converter A5, and the output signal of the programmable gain amplifier B4 is converted to a digital signal by an AD converter B5.
At step 6, it is converted to a digital signal.

The setting of the gain will be described using numerical values. The gain of the portion surrounded by the broken line in FIG. The input range of the AD converter is 1 Vpp. At this time, the clip level of the programmable level limiter 21 is set to 1 Vp
When set to p, the gain of the programmable gain amplifier 3 is set to 1. Also, a programmable level limiter 2
When the clip level of 1 is set to 0.5 Vpp, the gain of the programmable level limiter 21 is set to 2.
As described above, the controller 22 sets the clip level of the programmable level limiter 21 and the gains of the programmable gain amplifiers A3 and B4.

The outputs of the AD converters 5 and 6 are subjected to an autocorrelation operation in an autocorrelator as shown in FIG. 3, and the average shift frequency and the variance of the speed are output and displayed in color. You.

As described above, according to the present embodiment, the clutter signal of the input received signal is clipped to remove the higher harmonics, so that the higher harmonic components due to the clutter signal generated in the conventional AD converter can be removed. It is no longer mistaken for a style.

The present invention is not limited to the above embodiment. The function of the LPFA 24 downstream of the programmable level limiter 21 may be included in the LPFB 29 and LPFC 30 downstream of the mixers A25 and B26.

[0027]

As described above in detail, according to the present invention, even if a clutter signal having a large amplitude is input, noise to the color Doppler is obtained when a signal due to a blood flow at a level required for detection is obtained. This does not occur and the image is not colored, and the practical effect is great.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram of clipping by a programmable level limiter. FIG. 2A is a waveform diagram of an input signal, and FIG. 2B is a waveform diagram of a clipped output signal.

FIG. 3 is a block diagram of a data processing unit for obtaining a mean velocity and a velocity dispersion of a blood flow after a beamformer of the conventional ultrasonic diagnostic apparatus.

FIG. 4 is an explanatory diagram of harmonics generated by a clutter signal in a conventional ultrasonic diagnostic apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Beamformer 3, 4 Programmable gain amplifier 5, 6 A / D converter 21 Programmable level limiter 22 Controller 24, 29, 30 LPF

Continuation of the front page (56) References JP-A-60-179047 (JP, A) JP-A-2-291847 (JP, A) JP-A-1-198535 (JP, A) JP-A-49-107772 (JP) JP-A-52-131679 (JP, A) JP-A-3-133434 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) A61B 8/00-8/15 G01P 5/00

Claims (1)

(57) [Claims] In an ultrasonic diagnostic apparatus having a color Doppler function, a high-level clutter signal included in a received signal, which is provided at a stage subsequent to a beamformer (1) for phasing and adding a received signal, is clipped at a predetermined level. Level limiter (21) for performing a quadrature detection of at least a received signal (25, 2)
6) A filter (29, 30) provided at the subsequent stage for removing harmonic components, and a level of an output signal of the filter (29, 30) is set to a maximum allowable input level of the AD converter (5, 6). Programmable gain amplifier (3, 3)
4) and a controller (22) for setting a clip level of the programmable level limiter (21) and a gain of the programmable gain amplifiers (3, 4).