JP2013000352A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic diagnostic apparatus enabling a user to recognize the presence/absence and degree of the generation of apparatus-derived harmonic components or automatically reducing them when displaying a harmonic image.SOLUTION: An amplitude measuring section 46 refers to a plurality of analog receive signals and compares them with a threshold to measure the generated amount of excessive amplitude. Actually, the frequency of generation is measured as a count value. When the count value exceeds a specified value, a state determining section 48 determines the appearance of the apparatus-derived harmonic component on the image and determines its degree. The determined result is output as a state signal to a display processing section 40. The display processing section 40 displays the generation fact and degree of an apparatus-derived harmonic signal as indicators based on the state signal. A beam deflection angle may be automatically adjusted based on the state signal.

Description

  The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to an ultrasonic diagnostic apparatus that displays a harmonic image.

  An ultrasonic diagnostic apparatus is an apparatus that forms an ultrasonic image by transmitting and receiving ultrasonic waves to and from a living body. In an ultrasonic diagnostic apparatus having a harmonic component display function, reflected waves from a living body are received by a plurality of vibration elements, thereby generating a plurality of received signals. Beam data is formed by phasing addition processing for a plurality of received signals. Harmonic components included in the beam data are extracted, thereby generating a harmonic image. When the harmonic component generated at the time of reflection in the living tissue is imaged, and when the harmonic component generated by reflection or destruction of the contrast agent injected into the living body is imaged, There is. The former is tissue-harmonic imaging and the latter is contrast harmonic imaging. As a method for extracting harmonic components, a filter method, a pulse modulation method, a pulse inversion method, and the like are known.

  Since the level of the harmonic component contained in the received signal is generally about several tens of dB lower than the level of the fundamental component, it is necessary to significantly increase the gain of the entire received signal in order to form a harmonic image. is there. However, when a reflected wave from a strong reflector such as an organ surface in a living body is received, the amplitude of the received signal is locally excessive and the amplitude of the received signal is saturated, that is, the received signal is distorted. For example, if the amplitude of the amplified received signal exceeds the input range of the A / D converter or exceeds the linear operating range of the amplifier, the received signal is distorted there, and a harmonic component is generated in the apparatus. Such a harmonic component is an extra harmonic component that should be distinguished from a biologically derived harmonic component generated in a tissue in a living body or a contrast medium, and can be referred to as a device-derived harmonic component.

  When the device-derived harmonic component is generated, the device-derived harmonic component is also reflected on the harmonic image together with the living body-derived harmonic component, thereby causing misidentification and the like. For example, when imaging a contrast agent, it is desirable that the biological tissue is not imaged or highlighted, but if there is a strong reflection site such as a tissue boundary, it will appear on the harmonic image, Or there is a problem that it is highlighted. As a result, there is a possibility that a contrast agent is present there. In the receiving unit, since a plurality of received signals are phased and added, harmonic components generated in individual channels are also added and appear as artifacts on the harmonic image. In order to prevent this, if the gain in each channel is kept low, the biologically derived harmonic components cannot be imaged sufficiently.

  The above problem is particularly problematic when displaying a harmonic image. However, even when displaying a normal ultrasonic image (fundamental wave component image), saturation of the received signal in the apparatus should be avoided. When the received signal is saturated, each mountain waveform is clipped, and the received signal approaches a rectangular wave. If this is seen on the frequency axis, it can be regarded as an increase in odd harmonic components.

JP 2004-135705 A Japanese Patent No. 4557579

  Patent Document 1 discloses an ultrasonic diagnostic apparatus that calculates a ratio between a fundamental wave component and a harmonic component included in a received signal and adjusts a gain based on the ratio. This apparatus does not generate a harmonic image, and the ratio between the fundamental wave component and the harmonic component is used to reduce side lobes. Patent Document 2 discloses a technique for attenuating a received signal by attenuating a fundamental wave component by providing a filter (HPF) for reducing a low frequency component in an upstream stage of an amplifier in an ultrasonic diagnostic apparatus. ing. None of the documents describes a concept of detecting information indicating the possibility of generation of in-device harmonic components and utilizing it.

  An object of the present invention is to allow a user to perceive a harmonic component other than the harmonic component generated in a living body in a harmonic image, or to suppress it so that the harmonic component is suppressed. The purpose is to enable accurate diagnosis of images.

  An ultrasonic diagnostic apparatus according to the present invention includes an amplifier that amplifies an analog reception signal obtained by transmitting and receiving ultrasonic waves, a converter that converts an analog reception signal output from the amplifier into a digital reception signal, and the digital A harmonic image forming unit that forms a harmonic image based on the harmonic component included in the received signal, and the analog received signal in the stage before being input to the converter, State signal generating means for generating a state signal indicating whether or not there is a possibility that a device-derived harmonic component generated in the ultrasonic diagnostic apparatus is included in addition to the living-body-derived harmonic component generated in the living body. And the status signal is used in at least one of display processing and beam scanning control.

  According to the above configuration, whether or not there is a possibility of occurrence of signal distortion (harmonic) caused by excessive input to the reception signal processing circuit, particularly the analog reception signal processing circuit, by referring to the analog reception signal, preferably by referring to the amplitude thereof Alternatively, it is possible to evaluate the degree and use a state signal representing it in display control or beam scanning control. A user operation method and an automatic beam scanning method are examples of methods for preventing the generation of harmonics in the apparatus. In the former case, it is desirable to inform the user of the fact or degree of occurrence of an excessive signal, and in the latter case, the apparatus operating conditions are changed so that the excessive signal is reduced or eliminated. It is also possible to manually change the beam deflection angle, and it is also possible to automatically change it according to the status signal. When steering scanning (deflection scanning) is performed, it is possible to scan almost the same scanning area while changing the reflection conditions.

  Among a plurality of analog reception signals corresponding to a plurality of reception channels, one analog reception signal may be referred to, but more or all analog reception signals may be referred to. The state can be evaluated in units of a specific beam, a specific depth, a frame, and the like. Although it is desirable to obtain the frequency (number of times) that the amplitude exceeds the threshold as the generation amount of the excessive signal, other measurement may be performed. If the frequency is used, it is possible to evaluate the degree of obstruction (occurrence area) on the image. If an analog beamformer is provided, the analog reception signal after phasing addition may be referred to. When a digital beamformer is used, the reception signal reference point may be the pre-stage or the post-stage of the preamplifier, the pre-stage or the post-stage of the variable gain amplifier, or the like. It is desirable to refer to the amplitude just before the dynamic range (or its upper limit) is narrowed.

  Preferably, the state signal generation means includes detection means for detecting an amount of occurrence of an excessive amplitude value with respect to the analog reception signal, and means for generating the state signal based on the amount of occurrence of the excess amplitude value. Including. Preferably, the amplifier includes a first stage amplifier circuit, and a variable gain amplifier circuit provided at a subsequent stage and having a gain variably set according to a reception point depth, and the detection means includes the variable gain amplifier circuit and Reference is made to an analog received signal taken from between the converters. The reception point is a reception focus point when reception dynamic focus is applied.

  Preferably, display processing means for displaying an indicator visually indicating the presence or absence of the possibility that the device-derived harmonic component is included based on the state signal. Preferably, the indicator is displayed on the display screen together with the harmonic image, and the display content of the indicator dynamically changes with the dynamic change of the harmonic image. The indicator may be a character display, a graph display, or the like.

  Preferably, the input unit is operated by a user who looks at the indicator, and includes an input unit that changes a deflection angle of an ultrasonic beam scanned electronically.

  Preferably, it includes a scanning control means for variably setting the deflection angle of the ultrasonic beam that is electronically scanned based on the state signal. Preferably, the scanning control unit includes a determining unit that determines a best deflection angle based on a change in the state signal when the deflection angle is changed on a trial basis, and the ultrasonic wave after the trial variable of the deflection angle. Setting means for setting the best deflection angle as the deflection angle of the beam. Desirably, there is provided means for synthesizing the harmonic image acquired with the setting of the first deflection angle and the ultrasonic image acquired with the setting of the second deflection angle to generate a synthesized harmonic image, A synthesized harmonic image is displayed.

  When referring to the received signal, its harmonic (particularly third harmonic) component may be referenced. The received signal may be referred to only within the region of interest. Incidentally, when a plurality of sections are set in the depth direction, a reference value or threshold value for generating a state signal may be individually set for each section. Instead of or in addition to the beam scanning control, means for adaptively controlling the gain of the analog reception signal based on the status signal may be provided. In this case, the gain (gain curve in the depth axis direction) of the variable gain amplifier circuit may be changed. Further, when such gain adjustment is performed, it is possible to compensate the gain in the subsequent stage.

  According to the present invention, when a harmonic component other than the harmonic component generated in the living body is reflected in the harmonic image, the user perceives it or suppresses it so that the harmonic component is suppressed. Diagnose images accurately.

It is explanatory drawing for demonstrating the principle of embodiment which concerns on this invention. 1 is a block diagram showing a first embodiment of an ultrasonic diagnostic apparatus according to the present invention. It is a figure which shows the example of a display in 1st Embodiment. It is a block diagram which shows 2nd Embodiment of the ultrasonic diagnosing device which concerns on this invention. It is a figure which shows the relationship between the interface of a structure | tissue, and an ultrasonic beam. It is a figure which shows basic linear scanning and deflection | deviation linear scanning. It is a figure for demonstrating the setting of a region of interest.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

  FIG. 1 conceptually shows the principle of an embodiment according to the present invention. In FIG. 1, reference numeral 10 represents a received signal. This received signal is obtained by scanning the living body with ultrasonic waves and receiving a reflected wave from within the living body. The received signal contains harmonic components (biologically derived harmonic components). Specifically, the harmonic component is generated at the time of reflection of the ultrasonic wave in the living tissue, or is generated at the time of reflection by the ultrasonic contrast agent placed in the living body or at the time of destruction. is there. Analog signal processing is applied to the received signal as indicated by reference numeral 12. In this case, if the amplitude of the received signal becomes excessive and exceeds the signal processing range or the input range of each circuit, the signal is distorted on each circuit, that is, a harmonic component derived from the device is generated. . Therefore, the received signal that has undergone the analog signal processing may include a device-derived harmonic component in addition to the biological-derived harmonic component. A digital signal conversion process is applied to such a received signal, and various digital signal processes are applied.

  A harmonic component is extracted from the digital received signal that has undergone the signal processing as described above, as indicated by reference numeral 14. For example, a harmonic component such as a second harmonic component is extracted using a band pass filter. Recently, harmonic components have been extracted by the pulse modulation method and the pulse inversion method, and such a technique can of course be used. Based on the extracted harmonic components, an ultrasonic image (B-mode tomographic image) is formed as indicated by reference numeral 16 and displayed on the screen.

  The extracted harmonic image may contain device-derived harmonic components in addition to the above-mentioned biological-derived harmonic components, which may be an obstacle in image diagnosis or cause misidentification. There is sex. Therefore, in the present embodiment, it is detected that a signal having an excessive amplitude is generated in the analog signal processing circuit, and a signal indicating the fact of the possibility of occurrence of the apparatus-derived harmonic component and the degree thereof is generated. ing. Hereinafter, this is referred to as a status signal.

  As indicated by reference numeral 18, it is possible to display a state on the display screen based on such a state signal. In other words, the generation and degree of apparatus-derived harmonic components are quantitatively displayed to the user. With reference to such a display, it is possible to recognize that the harmonic image contains a harmonic component that is not a harmonic component that should be originally evaluated. In this embodiment, as indicated by reference numeral 20, the data acquisition condition is changed based on the status signal. Specifically, the beam deflection angle is changed, so-called linear deflection scanning is performed, and the angle formed between the living tissue boundary surface and the ultrasonic beam is varied. As will be described later, since the strongest reflection is obtained when the ultrasonic beam is orthogonal to the boundary surface, it is possible to apply a weakening operation to an excessively strong amplitude if the beam angle is deflected. Become. In this case, it is possible to automatically find the optimum deflection angle by adjusting the beam deflection angle while referring to the status signal. However, the beam deflection angle can be variably set manually by the user based on the status display.

  FIG. 2 shows a block diagram of the ultrasonic diagnostic apparatus according to the first embodiment. This ultrasonic diagnostic apparatus performs ultrasonic diagnosis of a living body and is installed in a medical institution such as a hospital. In the present embodiment, as described above, a harmonic image of a living tissue or an in-vivo contrast agent is generated.

  The array transducer 22 is disposed in an ultrasonic probe (not shown). The array transducer 22 includes a plurality of vibration elements 24 arranged linearly in the present embodiment. In the present embodiment, electronic linear scanning is applied, and the ultrasonic beam formed by the array transducer 22 is electronically linearly scanned. Thereby, a two-dimensional data capturing area (beam scanning surface) is formed. Of course, in this embodiment, an ultrasonic beam may be scanned in a three-dimensional space. Also, other electronic scanning methods may be applied.

  The transmission unit 26 is a transmission beam former, and supplies a plurality of transmission signals subjected to delay processing to the plurality of vibration elements 24. As a result, a transmission beam is formed, a reflection signal (echo) is generated from each depth in the living body, and is received by the plurality of vibration elements 24 again. Thereby, a plurality of reception signals (analog reception signals) are generated.

  The reception unit 28 is a reception beam former, and performs phasing addition processing on a plurality of reception signals. Specifically, the reception unit 28 includes a plurality of reception channel processing circuits 30. Each reception channel processing circuit 30 includes a preamplifier (first stage amplifier) 30A, a variable gain amplifier (TGC amplifier) 30B, a filter (high cut filter) 30C, an A / D converter 30D, a delay unit 30E, and the like provided from upstream to downstream. It has. Here, the filter 30C is provided as necessary, and other circuits may be provided. The A / D converter 30D is a circuit that converts an analog reception signal into a digital reception signal, which may be provided in front of the filter 30C. The delay device 30E is configured by a FIFO memory. The configuration of such a reception channel circuit is general. The adder 32 is a circuit that adds a plurality of digital reception signals after delay processing, and thereby obtains beam data as digital signals. The beam data is output to the signal processing unit 34. The variable gain amplifier 30B is an amplifier whose gain can be varied according to the reception point depth.

  The signal processing unit 34 includes various signal processing circuits such as a detector, a gain adjuster, and a logarithmic converter. The beam data after the signal processing is output to the harmonic extraction unit 36. The harmonic extraction unit 36 is constituted by, for example, a bandpass filter that extracts harmonic components. When the pulse modulation method or the pulse inversion method is applied, a predetermined calculation is executed between a plurality of beam data acquired by time division, and thereby harmonic components are extracted. The extracted harmonic components (which may also be said to be received signals) are input to a digital scan converter (DSC) 38, where the harmonic components on each beam are mapped, and a B-mode image (harmonic image). ) Is generated. The image data is sent to the display unit 42 via the display processing unit 40. A harmonic image is displayed on the display unit 42.

  In the present embodiment, a state signal generation unit 44 is provided. The state signal generation unit 44 includes an amplitude measurement unit 46 and a state determination unit 48 in the present embodiment.

  The amplitude measurement unit 46 is a module that measures excessive amplitude based on a plurality of analog reception signals extracted from the plurality of reception channel processing circuits 30. In this embodiment, analog reception signals are extracted from all reception channels, but one analog reception signal or several analog reception signals may be referred to. In this embodiment, the analog reception signal is extracted from between the variable gain amplifier 30B and the filter 30C. However, the analog reception signal is extracted from between the preamplifier 30A and the variable gain amplifier 34 or from other locations. It may be.

  The amplitude measuring unit 46 evaluates the amplitude based on a plurality of analog reception signals. In the present embodiment, each analog reception signal is compared with a predetermined threshold value, and when the threshold value is exceeded, a pulse is output to the state determination unit 48 at the subsequent stage. In this case, amplitude measurement, that is, excessive signal counting may be performed for only a predetermined beam, or such measurement may be performed for only a certain depth. Alternatively, such measurement may be performed on a specific frame. Furthermore, as described later, only the partial region (region of interest ROI) set on the scanning plane may be evaluated.

  The state determination unit 48 compares the value (count value) representing the excessive signal occurrence frequency output from the amplitude measurement unit 46 with a predetermined value, and if the count value becomes larger than the predetermined value, the state determination unit 48 It is determined that a harmonic component is likely to be generated. Specifically, the degree of the unnecessary harmonic component generation state is determined according to a level exceeding a predetermined value. The signal indicating the presence / absence and the degree of the state is the state signal described above. If the count value is compared with the predetermined value, if an excessive amplitude occurs instantaneously, it can be ignored.

  In the present embodiment, the status signal is output to the display processing unit 40. The display processing unit 40 is a processing unit that performs display as shown in FIG. That is, the ultrasonic image and the graphic image are combined and the combined image is output to the display unit 40.

  The operation of the display processing unit will be described with reference to FIG. In the display screen 100, a harmonic image 102 as an ultrasonic image is displayed. Incidentally, reference numeral 104 represents an ultrasonic beam. In this embodiment, since electronic linear scanning is applied, the ultrasonic beam 104 is scanned in parallel translation in FIG. In the example shown in FIG. 3, the harmonic image 102 is, for example, an image representing one of the blood vessels (such as the carotid artery) 105, in which the front wall boundary 106 </ b> A and the rear wall boundary 106 </ b> B for the blood vessel 105 appear. ing. Incidentally, the front wall is displayed with higher brightness here. Therefore, there is a high possibility that an excessive amplitude has occurred.

  The display processing unit displays an indicator based on the state signal along with the ultrasonic image 102 on the display screen 100. In the present embodiment, the indicator is composed of a graph 110 and a character display 108, where the character display 108 is composed of characters representing the generation of device-derived harmonic components. When the above-described count value exceeds a certain value, such character display 108 is performed. In such a state, the level exceeding the predetermined value, that is, the degree, is displayed as the graph 110. It corresponds to a bar graph, and an excessive state is expressed as the number of light emitting cells.

  Therefore, the user refers to the indicator as shown in FIG. 3, and when observing the harmonic image, the harmonic component derived from the original tissue or the harmonic component derived from the other device is mixed. If it is, or if it is mixed, it is possible to intuitively understand the degree and use it for image diagnosis.

  Incidentally, in FIG. 2, a control unit 50 is a control unit that controls the operation of each component shown in FIG. 2, and is configured by a CPU and an operation program. An input unit 52 configured by an operation panel or the like is connected to the control unit 50. The user can adjust the beam deflection angle by adjusting the beam deflection angle while observing the indicator, that is, the over-amplitude on the indicator is minimized or disappears by using the input unit 52. It is. Further, other parameters may be operated. By changing the contact position and the contact angle of the ultrasonic probe, it is possible to eliminate or reduce the state in which the excessive amplitude is generated.

  In any case, if the display indicating the status signal as described above is performed, it is quantitatively recognized whether the signal is an original harmonic or a harmonic due to other factors, and the convenience of the user is achieved. It becomes possible.

  FIG. 4 shows a block diagram of an ultrasonic diagnostic apparatus according to the second embodiment. The same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  In the configuration example shown in FIG. 4, the state signal output from the state determination unit 48 is output to the steering control unit 54. The steering control unit 54 performs linear deflection scanning, and in particular sets the deflection angle.

  Specifically, when the possibility of generating unnecessary harmonic components is detected, the steering control unit 54 performs control to change the beam deflection angle. At the same time, the best deflection angle when the trial beam deflection angle is varied is automatically determined. That is, the deflection angle at which the excessive amplitude does not occur or the excessive amplitude is minimized is automatically found, and the deflection angle is set as the deflection angle when actually performing the ultrasonic diagnosis. FIG. 5A illustrates a state in which a transmission wave 58 is perpendicularly incident on the boundary surface 56 in the living body, and a reflected wave 60 is generated in the vertical direction. On the other hand, FIG. 5B illustrates a state in which the transmission wave 62 is incident on the boundary surface obliquely, and the reflected wave 64 is generated in the oblique direction. Due to the nature of ultrasonic waves, generally, a strong reflected wave is generated when the boundary surface and the ultrasonic beam axis are orthogonal to each other. That is, when the reflected wave 60 and the reflected wave 64 are compared, the reflected wave 60 is stronger even if other conditions are the same. Using this property, excessive amplitude can be suppressed. In this case, frames having different beam deflection angles may be generated in order by selecting a plurality of deflection angles and setting them in order. Then, a synthesized harmonic image may be generated by synthesizing the harmonic images formed for each frame. This is illustrated in FIG.

  In FIG. 6, reference numeral 102 represents basic scanning performed without tilting the ultrasonic beam. Reference numerals 114 and 116 denote deflection scanning in which scanning is performed by tilting the ultrasonic beam. Each scan constitutes one frame, that is, a harmonic image is generated for each scan. A synthesized ultrasonic image is created by combining them. In this case, it is desirable to set the best deflection angle at which the excessive amplitude does not occur or becomes the minimum as the beam deflection angle as described above. Although three frames are synthesized in FIG. 6, it is desirable that at least two frames are synthesized.

  FIG. 7 shows the setting of the region of interest (ROI) 118. In the example shown in FIG. 7, a region of interest 118 is set as a region included in any of a plurality of frames, and the degree of occurrence of excessive amplitude is evaluated there. That is, the evaluation is not performed on the excessive amplitude over the entire frame but on a partial region. In displaying an image, only the portion of the region of interest may be enlarged and displayed.

  22 array transducers, 28 reception unit, 30 reception channel processing circuit, 32 adder, 34 signal processing unit, 36 harmonic extraction unit, 40 display processing unit, 44 state signal generation unit, 46 amplitude measurement unit, 48 state determination unit .

Claims (9)

An amplifier for amplifying an analog reception signal obtained by ultrasonic transmission / reception;
A converter for converting an analog reception signal output from the amplifier into a digital reception signal;
A harmonic image forming unit that forms a harmonic image based on a harmonic component included in the digital reception signal;
By referring to the analog reception signal at the stage before being input to the converter, it is derived from the device generated in the ultrasonic diagnostic apparatus in addition to the living body-derived harmonic component generated in the living body in the harmonic image. State signal generating means for generating a state signal indicating the presence or absence or degree of possibility of including harmonic components;
Including
The ultrasonic diagnostic apparatus, wherein the status signal is used in at least one of display processing and beam scanning control. The apparatus of claim 1.
The state signal generating means includes
Detecting means for detecting an amount of occurrence of an excessive amplitude value with respect to the analog reception signal;
Means for generating the state signal based on the amount of occurrence of the excess amplitude value;
An ultrasonic diagnostic apparatus. The apparatus of claim 2.
The amplifier includes a first stage amplifier circuit, and a variable gain amplifier circuit that is provided at a subsequent stage and the gain is variably set according to the reception point depth,
The ultrasonic diagnostic apparatus, wherein the detection means refers to an analog reception signal taken out between the variable gain amplifier circuit and the converter. The apparatus of claim 1.
An ultrasonic diagnostic apparatus comprising: display processing means for displaying an indicator visually indicating whether or not the apparatus-derived harmonic component may be included based on the state signal. The apparatus of claim 4.
The ultrasonic diagnostic apparatus, wherein the indicator is displayed on a display screen together with the harmonic image, and the display content of the indicator dynamically changes in accordance with a dynamic change of the harmonic image. The apparatus of claim 5.
An ultrasonic diagnostic apparatus comprising: an input unit that is operated by a user viewing the indicator and changes an deflection angle of an ultrasonic beam that is electronically scanned; The apparatus of claim 1.
An ultrasonic diagnostic apparatus comprising: scanning control means for variably setting a deflection angle of an ultrasonic beam that is electronically scanned based on the state signal. The apparatus of claim 7.
The scanning control means includes
Determining means for determining a best deflection angle based on a change in the state signal when the deflection angle is changed on a trial basis;
Setting means for setting the best deflection angle as a deflection angle of the ultrasonic beam after the trial variable of the deflection angle;
The ultrasonic diagnostic apparatus characterized by performing. The apparatus of claim 7.
Means for synthesizing the harmonic image acquired at the setting of the first deflection angle and the ultrasonic image acquired at the setting of the second deflection angle to generate a synthesized harmonic image;
The ultrasonic diagnostic apparatus, wherein the synthesized harmonic image is displayed.

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