JP2001258882A - Ultrasonograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable diagnosis with low noise by eliminating frequency components other than higher harmonic components necessary for the formation of an image during harmonic use to prevent the generation of higher harmonics caused by the saturation of unnecessary frequency components. SOLUTION: Low cut-off filters 18, 18' for eliminating basic wave components are connected to the output of phase delay adding circuits 14, 14' respectively provided at a plurality of signal processing systems to adjust and add the phases of a plurality of input signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ultrasonic diagnostic apparatus which detects harmonic components of an ultrasonic reception signal to form an image.

[0002]

2. Description of the Related Art In recent years, in an ultrasonic diagnostic apparatus, a harmonic mode in which a harmonic component is extracted from an ultrasonic reception signal, an image is formed using the harmonic component, and displayed is widely used. The image configured in the harmonic mode has characteristics such as high resolution and low artifact compared to an image configured using the fundamental wave component. It is known that the harmonic component is generated in the body of a subject by using a contrast agent or by increasing the amplitude of an ultrasonic pulse to be transmitted. The harmonic component generated in the body of the subject is received by the ultrasonic probe as an ultrasonic reception signal together with the fundamental wave component. In addition, in an ultrasonic diagnostic apparatus, a received signal is generally amplified by an amplifier in order to improve reception sensitivity.

However, since the harmonic component generally has a smaller amplitude than the fundamental component,
If the received signal is amplified to a certain value or more by an amplifier without removing the fundamental component, a second harmonic is generated due to the saturation of the fundamental component, and is mixed with the second harmonic signal used in the harmonic mode. Will occur. Therefore, when performing diagnosis in the harmonic mode, it is necessary to remove the fundamental wave component before the amplified fundamental wave component is saturated and a second harmonic is generated.

Here, a block diagram of signal processing in a conventional example is shown in FIG. In FIG. 7, the transmission signal generation circuit group 92
An ultrasonic signal is generated by the ultrasonic probe 91 connected to the
It is transmitted into the body of the subject. The transmitted signal generates a reflected wave according to the condition of an organ or the like, the reflected wave is received by the ultrasonic probe 91, and the received signal is received by the preamplifier circuit group 9
Amplify by 3. The amplified signal passes through two addition circuits 94 and 94 ′, is converted into one signal again by the switch 95, and then subjected to signal processing by the reception signal processing circuit 96. The control circuit unit 17 includes a preamplifier circuit group 93,
It is connected to each device of the addition circuits 94 and 94 ', the switch 95, and the reception signal processing circuit 96, and controls each device. Further, a bandpass filter is provided at a stage preceding the reception signal processing circuit 96. The band filter is a filter used for finely adjusting the frequency band of the fundamental wave component to be extracted. For example, in the body of a subject, a signal at a higher frequency is attenuated at a deeper position, so that in order to perform a diagnosis at a deeper position, a signal at a lower frequency must be extracted as a larger signal. In this case, The pass band of the bandpass filter is shifted slightly to the lower frequency side.

In the conventional example, as a method of extracting the second harmonic component from the fundamental wave component, a method of passing the band of the second harmonic component by controlling the filter characteristics of the band filter has been used.

[0006]

However, as described above, since the bandpass filter is not originally provided for removing the fundamental wave component, the bandpass filter can reduce the fundamental wave component without lowering the gain of the harmonic wave component. Fundamental wave components that cannot be completely removed and could not be removed cause noise. Also, if the band is adjusted so that the fundamental wave component is completely removed, the gain of the harmonic component is reduced, so that it is necessary to amplify the harmonic component again, which also causes noise. I will.

In the above description, the relationship between the fundamental wave component and the harmonic wave component is used. When the harmonic wave components, for example, the third harmonic wave are used as a signal for forming an image, the second harmonic wave and the third harmonic wave are used. The same can be considered for the relation of the second harmonic. The present invention solves the above-described problems, and does not lower the gain of a harmonic component that becomes a signal constituting an ultrasonic image, and, in the case of a fundamental component, or a harmonic component, a lower-order harmonic component. It is an object of the present invention to provide an ultrasonic diagnostic apparatus capable of performing a diagnosis in a harmonic mode with less noise by completely removing the noise.

[0008]

According to a first aspect of the present invention, there is provided a transmitting means for transmitting an ultrasonic signal and a reflection of the ultrasonic signal transmitted by the transmitting means. Receiving means for receiving an ultrasonic reflected signal having a plurality of frequency components, and removing at least one frequency component of the received signal having a plurality of frequency components received by the receiving means, the receiving means being connected to the receiving means. A frequency component removing means, a band pass means connected to the frequency component removing means, for passing a signal of at least a part of the frequency of the output signal of the frequency component removing means, Signal processing means for forming a sound image. The present invention, by the above configuration, removes a frequency component that is not necessary for forming an ultrasonic image, thereby suppressing generation of a harmonic component due to saturation of a frequency component unnecessary for forming the ultrasonic image. Can be.

The invention described in claim 2 is the first invention.
The frequency component removing unit according to the present invention is a unit that removes a fundamental component that is a frequency component transmitted by the transmitting unit, and the band-pass unit is a unit that passes at least a harmonic component with respect to the fundamental component. It is characterized by. According to the present invention, in addition to the effect of the first aspect, generation of harmonics due to the saturation of the fundamental wave component can be suppressed.

[0010] Further, the invention described in claim 3 is based on claim 2.
The band pass means described above is means for passing a second harmonic component having a frequency twice as high as the fundamental wave component. According to the present invention, in addition to the effect of the second aspect, an image can be formed by using the signal of the second harmonic, in particular, in addition to the operation of the second aspect.

The invention described in claim 4 is the first invention.
The frequency component removing means according to any one of the first to third aspects is a low cut filter for removing low frequency components. According to the present invention, in addition to the function of any one of claims 1 to 3, the low frequency filter is used as the frequency component removing means to remove low frequency components, and to reduce harmonic components from an ultrasonic reception signal. Only the components can be taken out.

The invention described in claim 5 is the first invention.
5. An output of the receiving means according to any one of the first to fourth aspects, wherein a first amplifying means for amplifying a signal received by the receiving means is provided. According to the present invention, in addition to the function of any one of the first to fourth aspects, a signal having an appropriate magnitude can be generated by the first amplifying means.

The invention according to claim 6 is the first invention.
6. The transmitting means and the receiving means according to any one of claims 5 to 5, wherein the transmitting means and the receiving means are an ultrasonic probe having a plurality of ultrasonic transducers, and the plurality of ultrasonic waves are provided between the ultrasonic probe and the frequency component removing means. Phase adjusting and adding means for adjusting and adding the phase of the received signal received by each of the transducers is provided. According to the above configuration, the present invention can be applied to an ultrasonic diagnostic apparatus using a plurality of ultrasonic transducers and a phase adjusting and adding unit as a method for determining the focus of the diagnostic unit.

The invention described in claim 7 is the same as the claim 6.
A plurality of phase adjustment and addition means and the frequency component removal means, and a reception signal received by the plurality of ultrasonic transducers is connected to the plurality of phase adjustment and addition means and frequency component removal means; Switching input means for switching and outputting the output of each of the frequency component removing means is provided at the input. According to the above configuration, the present invention can be applied to an ultrasonic diagnostic apparatus having a plurality of focal points in addition to the function of claim 6.

The invention described in claim 8 is the first invention.
A second amplifying means for amplifying a signal is provided at an output of the frequency component removing means according to any one of the first to seventh aspects. According to the present invention, in addition to the function of any one of the first to seventh aspects, a signal having an appropriate magnitude can be generated by the second amplifying means.

The invention according to claim 9 is the invention according to claim 6.
Or a plurality of frequency component removing means provided at the output of each of the phase adjusting and adding means, and any of the plurality of frequency component removing means may be provided at the input, output, or both input and output sides of the plurality of frequency component removing means. Selecting means for selecting and using the frequency component removing means. According to the present invention, in addition to the function of the sixth or seventh aspect, even when the frequency to be used is different, such as the B mode and the color mode, an appropriate frequency component removing means can be selected by the selecting means.

According to a tenth aspect of the present invention, there is provided a third aspect of the present invention, comprising the steps of: amplifying a signal to each output of a plurality of frequency component removing means provided at an output of each phase adjusting and adding means; Amplifying means is provided.
According to the present invention, an appropriate frequency component removing means can be selected by the selecting means by the above configuration, and at the same time, a plurality of frequency component removing means are provided with the third amplifying means, respectively, thereby being suitable for each frequency component removing means. Amplification can be performed.

According to an eleventh aspect of the present invention, a fourth amplifying means for amplifying a signal is provided at the output of the selecting means according to the ninth aspect, and an amplification factor of the fourth amplifying means is set to an arbitrary value. Is settable. According to the present invention, since the appropriate frequency component removing means can be selected by the selecting means at the same time, the amplification factor of the fourth amplifying means is variable.
It is not necessary to provide the amplifying means, and the number of amplifying means can be reduced.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment according to the present invention will be described in detail with reference to the drawings. FIG.
FIG. 3 is a block diagram according to the first embodiment. FIG.
As shown in FIG. 1, the first embodiment is composed of a transmission signal generation circuit group 12, a transducer group 11, an amplification circuit group 13, phase delay addition circuits 14 and 14 ', low cut filters 18 and 18', a signal amplification circuit 19, 19 ', switch 15,
It comprises a signal processing circuit 16 and a control circuit section 17.

The transmission pulse transmitted from the transmission signal generation circuit group 12 is applied to the N vibrator groups 11 to transmit ultrasonic waves into the body of the subject. In the body of the subject, the transmitted ultrasonic wave is reflected by a certain value according to the type of the organ and the like, and the reflected signal is received again by the transducer group 11 and converted into an electric signal. The N received signals received by the transducer group 11 are amplified by the amplifier circuit group 13 to such an extent that the fundamental wave components are not saturated, and then output to two signal processing systems.
Each of the signal processing systems is provided with phase delay addition circuits 14 and 14 ′. The N signals are shifted in phase by delay processing to determine the focus in the depth direction inside the body of the subject, and the addition is performed. Do. The added signals are subjected to low-cut filters 18 and 18 'connected to the outputs of the phase-delay addition circuits 14 and 14', respectively, to remove the fundamental wave component, and the signal amplifications connected to the outputs of the low-cut filters 18 and 18 ', respectively. The second harmonic components are amplified by the circuits 19 and 19 '. Outputs of the signal amplification circuits 19 and 19 'are connected to a switch 15, and the signal amplification circuits 19 and 19'
By switching the output of 9 ′ at an arbitrary timing, it is output as one signal. This is for focusing in the depth direction into the body of the subject within a range delimited by a certain interval.
(Dynamic Variable Aperture and Focus) technology. The output of the switch 15 passes through a signal processing circuit 16,
An image is displayed by image display means (not shown) based on the processed signal.

In the present embodiment, the signal processing system is
However, as shown in FIG. 6, the present invention can be applied to a case where only one signal processing system is used. The control circuit unit 17 is connected to the amplifier circuit group 13, the phase delay addition circuits 14 and 14 ', and the switch 15, and controls the amplification factor and the phase difference, and controls the switching timing.

The signal processing circuit 16 is provided with a band filter 20, and the resolution can be optimized by adjusting the pass band of the band filter 20.

Here, FIG. 2C shows the frequency gain characteristics of the output of the low-cut filter and the band-pass filter 20 in the first embodiment. 2, F is a fundamental wave component, H is a second harmonic component, f1 is a center frequency of the fundamental wave component, and f2 is a center frequency of the second harmonic component. B indicates a pass band of the band-pass filter, W indicates a pass band of the low-cut filter 18 or 18 ', and a portion where the fundamental wave component and the second harmonic component pass is indicated by oblique lines. Here, the pass band W of the low-cut filter 18 or 18 ′ has a band and a gain that allow the second harmonic component H to pass while removing the fundamental component F completely.

FIGS. 2A and 2B show frequency gain characteristics in the related art. FIG. 2A shows a case where the center frequency passing through the band-pass filter matches the center frequency of the second harmonic component. FIG. 2B shows the relationship between the frequency and the gain when the fundamental wave component is completely removed by the bandpass filter. As shown in FIG.
When the center frequency passing through the bandpass filter matches the center frequency f2 of the second harmonic component, a part of the fundamental wave component F overlaps with the pass band B of the bandpass filter, and a part of the fundamental wave component F is removed. In addition, as shown in FIG. 2B, when the pass band B of the band-pass filter is shifted to a higher frequency side so that the fundamental wave component F can be removed, one of the second harmonic components H There is a problem that the portion is removed by the bandpass filter, and the gain of the second harmonic component H decreases.

In the first embodiment, as shown in FIG. 2C, unlike the conventional example of FIG. 2A, the fundamental wave component F is completely removed by the pass region W of the low-cut filter. Also, unlike FIG. 2B, which is a conventional example, the gain of the second harmonic component H does not decrease. In the first embodiment, the case where the second-order harmonic component H is used is shown. However, the second-order harmonic component is not limited to the second-order harmonic component. good. In this case, the pass band B of the bandpass filter and the pass band W of the low-cut filter may be adjusted.

Switching noise is generated when the switching unit 15 is switched. The switching noise will be described.
FIGS. 3A and 3B respectively show the waveform of the switch control signal, and FIG.
(B) shows the output waveforms of the phase delay addition circuits 94 and 94 'in the conventional example, (c) shows the output waveform of the switch 95 in the conventional example, (d) shows the output waveform of the bandpass filter in the conventional example, and (e). Shows the output waveform of the switch 15 in the first embodiment, and (f) shows the output waveform of the bandpass filter in the first embodiment. FIG. 3A, which is the output of the phase delay addition circuit 94, when FIG. 3S is off when the switch control signal controlled by the control circuit unit is off, and FIG. 3B, which is sometimes the output of the phase delay addition circuit 94 ', is switched by the switch 95, and the output of the switch 95 has the waveform shown in FIG. 3C.

However, there is a phase shift between FIGS. 3 (a) and 3 (b), which are the outputs of the phase delay addition circuits 94 and 94 '. As shown, when the switch 95 is switched on and off, a discontinuous waveform portion occurs. This discontinuous waveform portion causes switching noise existing in a higher frequency range than the fundamental wave component F. This switching noise is indicated as N in FIG.

In the case of an image configuration using the fundamental wave component F, since the center frequency of the bandpass filter is set near the center frequency f1 of the fundamental wave component F, the switching noise N higher than the fundamental wave component F is reduced. Although almost eliminated, when performing a diagnosis using a harmonic component, the center frequency of the bandpass filter needs to be set near the center frequency f2 of the harmonic component H, and thus is shown in FIG. As described above, the switching noise N cannot be removed, and appears as a bright line on the ultrasonic image.

Therefore, if the fundamental signal F is removed from the input signal of the switch 15 in advance by a low-cut filter as in the first embodiment, the output of the switch 15 becomes as shown in FIG. As a result, the switching noise N generated due to the phase shift of the fundamental wave component F can be reduced, and the occurrence of the bright line can be suppressed. As is apparent from a comparison between FIG. 3D, which is the output waveform of the bandpass filter in the conventional example, and FIG. 3F, which is the output waveform of the bandpass filter in the first embodiment, switching in the output waveform of the bandpass filter is apparent. It can be seen that the noise N is small. In the first embodiment, the second harmonic component H
Can be removed without lowering the gain, and the gain of the reduced second harmonic component H can be amplified, and noise due to insufficient removal of the fundamental wave component F can be reduced. At the same time, when the DVAF technique is used, the noise generated at the time of switching can be reduced by removing the fundamental wave component F before the input to the switch 15.

Next, a first modification of the first embodiment is shown in FIG. FIG. 4 is a modification of the part shown by the dotted line in FIG.
Only one is shown. In the first embodiment, one low-cut filter 18 and one signal amplification circuit 19 are used between the phase delay addition circuit 14 and the switch 15 for each signal processing system. In the figure, three low-cut filters 48 are provided in parallel for each signal processing system, and a signal amplifier circuit 49 is connected to the output of each of the low-cut filters 48.

A signal switching device 41 is connected to the input of the low-cut filter 18, and a signal switching device 42 is provided at the output of the signal amplifying circuit 49. By the signal switching devices 41 and 42, a low cut filter and a signal amplifier circuit to be used can be arbitrarily selected and used.

The number of low cut filters 48 and signal amplifier circuits 49 is not limited to three as long as the number is plural. For example, the low cut filter 4 to be used
In the case where 8 is the top stage in FIG. 4, both the signal switching unit 41 connected to the input of the low cut filter 48 and the signal switching unit 42 connected to the output of the signal amplification circuit 49 are the top stage. As described above, the control circuit unit 17
Each signal switching device 41 using the control signal from
42. It should be noted that the signal switching devices 41 and 42
By using one of these, the signal can be switched reliably, but either one of the switching devices may be used.

Here, by setting the low cut filters to different cutoff frequencies, the low cut filters can be selected and used according to different modes such as B mode, M mode, and color mode. When different modes such as the B mode and the color mode are displayed at the same time, for example, one signal processing system sets a low-cut filter used for displaying the B mode, and the other signal processing system sets a color cut filter. By setting the low cut filter used for displaying the mode, the resolution depends on the setting of the color mode.
In the mode, the resolution can be improved.

The low-cut filter may be selected not for different modes but for each frequency of the ultrasonic probe to be connected. When the low cut filter is selected for each frequency, the fundamental component of the received signal can be optimally removed, and the resolution of the second harmonic component is improved. Further, by selecting a low cut filter for each signal processing system, and in the first embodiment, for each of the two signal processing systems after the amplifier circuit group 13, the image resolution in the depth direction inside the subject is improved. Can be improved.

In this modification, in addition to the effects of the first embodiment as described above, a low-cut filter corresponding to a different mode or the like can be arbitrarily selected.

Next, FIG. 5 shows a second modification of the first embodiment. In the second modified example, unlike the first modified example shown in FIG. 4, the signal amplifying circuit 49 is not connected to each output of the low-cut filter, and the signal switching device 4
2 is connected to a variable amplifier circuit 51. Further, the variable amplification circuit 51 can change the amplification factor by a control signal from the control circuit unit 17. However, the variable amplification circuit 51 may control the amplification factor by control means other than the control circuit unit 17. In this modified example, in addition to the effects of the first embodiment and the first modified example, by using the variable amplifier circuit 51, the number of signal amplifiers required by the number of low cut filters can be reduced by the number of signal switching devices. Can only be reduced.

[0037]

As described in detail above, according to the present invention, the low-cut filter removes the frequency components lower than the harmonic components that generate an image, thereby reducing the frequencies existing in the low frequencies. Prevents the generation of harmonics due to the saturation of components, and can extract only the necessary harmonic components,
Ultrasonic diagnosis can be performed in a harmonic mode with less noise.

[Brief description of the drawings]

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

FIG. 2 is a frequency-gain characteristic diagram according to the first embodiment of the present invention and a conventional example.

FIG. 3 is a signal waveform diagram of each unit according to the first embodiment of the present invention and a conventional example.

FIG. 4 is a block diagram in a first modification of the first embodiment according to the present invention.

FIG. 5 is a block diagram of a second modification of the first embodiment according to the present invention.

FIG. 6 is a block diagram according to the first embodiment of the present invention.

FIG. 7 is a block diagram in a conventional example.

[Explanation of symbols]

 Reference Signs List 11 oscillator group 12 transmission signal generation circuit group 13 amplification circuit group 14 phase delay addition circuit 14 'phase delay addition circuit 15 switch 16 signal processing circuit 17 control circuit section 18 low cut filter 18' low cut filter 19 signal amplification circuit 19 'signal Amplifier circuit 20 Band filter 41 Signal switching device 42 Signal switching device 48 Low cut filter 49 Signal amplification circuit 51 Variable amplifier circuit B Pass band of band filter F Fundamental wave component H Second harmonic component W Pass band of low cut filter f1 Fundamental wave component Center frequency of f2 center frequency of second harmonic component

Continued on the front page (72) Inventor Naoto Wakabayashi 1385, Shimoishigami, Otawara-shi, Tochigi Pref. 2G047 BA03 EA04 EA07 GG17 4C301 CC02 DD01 DD04 EE04 EE07 JB38

Claims (11)

[Claims] A transmitting means for transmitting an ultrasonic signal; a receiving means for receiving an ultrasonic reflected signal which is a reflection of the ultrasonic signal transmitted by the transmitting means and has a plurality of frequency components; and the receiving means. And a frequency component removing unit that removes at least one frequency component of the received signal having a plurality of frequency components received by the receiving unit, and that is connected to the frequency component removing unit, An ultrasonic diagnostic apparatus comprising: band-pass means for passing a signal of at least a part of the frequency of the output signal; and signal processing means for forming an ultrasonic image from the signal passing through the band-pass means. . 2. The apparatus according to claim 1, wherein said frequency component removing means is means for removing a fundamental component which is a frequency component transmitted by said transmitting means, and said band pass means is configured to remove at least one harmonic component from said fundamental component. 2. An ultrasonic diagnostic apparatus according to claim 1, wherein said ultrasonic diagnostic apparatus is a means for passing said ultrasonic wave. 3. An ultrasonic diagnostic apparatus according to claim 2, wherein said band pass means is means for passing a second harmonic component having a frequency twice as high as said fundamental wave component. 4. The ultrasonic diagnostic apparatus according to claim 1, wherein said frequency component removing means is a low cut filter for removing low frequency components. 5. An ultrasonic diagnostic apparatus according to claim 1, wherein a first amplifying means for amplifying a signal received by said receiving means is provided at an output of said receiving means. . 6. An ultrasonic probe having a plurality of ultrasonic transducers as said transmitting means and receiving means, wherein said plurality of ultrasonic transducers are provided between said ultrasonic probe and said frequency component removing means. The ultrasonic diagnostic apparatus according to any one of claims 1 to 5, further comprising a phase adjusting and adding unit that adjusts and adds the phases of the received signals received by each of the steps (a) to (d). 7. A plurality of phase adjusting and adding means and a plurality of frequency component removing means are provided, and a reception signal received by the plurality of ultrasonic transducers is input to each of the plurality of phase adjusting and adding means and frequency component removing means. 7. The ultrasonic diagnostic apparatus according to claim 6, further comprising a switching output unit that switches and outputs an output of each of the frequency component removing units to an input of the band-pass unit. 8. The ultrasonic diagnostic apparatus according to claim 1, wherein a second amplifying means for amplifying a signal is provided at an output of said frequency component removing means. 9. A plurality of said frequency component removing means are provided at an output of each of said phase adjusting and adding means, and an input or an output of said plurality of frequency component removing means or an input / output of said plurality of frequency component removing means. 8. The ultrasonic diagnostic apparatus according to claim 6, further comprising a selection unit that can select and use an arbitrary frequency component removing unit from the list. 10. The apparatus according to claim 9, wherein a third amplifying means for amplifying a signal is provided at each output of the plurality of frequency component removing means provided at the output of each of the phase adjusting and adding means. An ultrasonic diagnostic apparatus as described in the above. 11. The apparatus according to claim 9, wherein a fourth amplifying means for amplifying a signal is provided at an output of said selecting means, and an amplification factor of said fourth amplifying means can be set to an arbitrary value.
An ultrasonic diagnostic apparatus as described in the above.