JP2010193944A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic diagnostic apparatus, which enables accurate real-time measurement of a subject's body in depth and facilitates the diagnosis of subject's tissues with close acoustic impedances without the influences of an operator's probe pressurizing way. <P>SOLUTION: The first ultrasonic signal is transmitted to a subject and the second ultrasonic signal reflecting from the subject's interior is received by a receiver to form electric signals. A signal processing part calculates nonlinear parameter distributions within the subject's body based on the n-degree frequency component strength ratio (n: a natural number) of the electric signals. An image processor generates image data, and a display visualizes the image data to plot it. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention transmits a first ultrasonic signal into a subject, receives a second ultrasonic signal generated by reflection of the first ultrasonic signal in the subject, and receives the second ultrasonic signal. The present invention relates to an ultrasonic diagnostic apparatus for forming an image in the subject based on a signal.

  Ultrasound generally refers to sound waves of 16000 Hz or higher and can be examined non-destructively, harmlessly and in real time, and thus is applied to various fields such as defect inspection and disease diagnosis. One of them is ultrasonic diagnosis that scans the inside of the subject with ultrasound and images the internal state of the subject based on the received signal generated from the reflected wave (echo) of the ultrasound coming from inside the subject. There is a device. This ultrasonic diagnostic apparatus is smaller and less expensive for medical use than other medical imaging apparatuses, has no radiation exposure such as X-rays, is highly safe, and has a blood flow utilizing the Doppler effect. It has various features such as display capability. For this reason, an ultrasonic diagnostic apparatus includes a circulatory system (for example, coronary artery of the heart), a digestive system (for example, gastrointestinal), an internal system (for example, liver, pancreas and spleen), and a urinary system (for example, kidney and bladder). Widely used in obstetrics and gynecology.

  An ultrasonic probe that transmits and receives an ultrasonic wave (ultrasonic signal) to a subject is used in the ultrasonic diagnostic apparatus. An ultrasonic probe uses a piezoelectric phenomenon to generate an ultrasonic wave (ultrasonic wave signal) by mechanical vibration based on an electric signal transmitted, and an ultrasonic wave generated due to mismatch of acoustic impedance inside a subject. A plurality of piezoelectric elements that receive a reflected wave of (ultrasonic signal) and generate a received electrical signal are provided. The plurality of piezoelectric elements are configured to be two-dimensionally arranged in an array, for example (see, for example, Patent Document 1).

  In addition to the above techniques, several ultrasonic diagnostic apparatuses have been proposed. For example, a technique has been proposed in which the amount of movement due to pressurization is measured from tomographic images during pressurization and non-pressurization, and the tissue properties are measured by detecting the difference in elastic modulus within the subject (Patent Document). 2).

  In addition, for example, an ultrasonic diagnostic apparatus that obtains an ultrasonic beam with less side lobes than the fundamental wave by using harmonics generated by a nonlinear response of the sound pressure of the subject and obtains a high-quality ultrasonic image has been proposed. (For example, refer to Patent Document 3).

  As an ultrasonic diagnostic apparatus using a non-linear response, an ultrasonic diagnostic apparatus for measuring a non-linear parameter based on a non-linear response and imaging it has been proposed (for example, see Patent Document 4).

JP 2004-088056 A JP-A-5-317313 JP-A-10-179589 Japanese Patent Laid-Open No. 10-199845

  The technique described in Patent Document 2 is affected by the way of the operator's pressurization operation, and there are cases where accurate measurement may not be possible, and the depth of the subject that is not affected by pressurization cannot be measured. is there.

  Although the technique described in Patent Document 3 uses harmonics resulting from nonlinear response, it uses a conventional method of measuring mismatched portions of acoustic impedance inside the subject, and the difference in acoustic impedance is There is a drawback that it is difficult to diagnose the inside of the tissue, which is a small and uniform structure with no reflected wave.

  Although the technique described in Patent Document 4 uses harmonics resulting from a non-linear response, it is necessary to perform transmission / reception of parameters depending on the drive voltage with a plurality of voltages, which increases the frame rate. Therefore, there is a disadvantage that it is not suitable for real-time measurement.

  The present invention provides an ultrasonic diagnostic apparatus capable of accurately measuring a deep part of a subject without being affected by an operator's method of pressurizing operation, easily diagnosing a tissue with close acoustic impedance, and capable of measuring in real time. The purpose is to do.

  The above object is achieved by the invention described below.

1. A plurality of transmitting elements for transmitting the first ultrasonic signal to a specific tissue in the subject;
A transmission unit for driving the transmission element;
A plurality of receiving elements that receive a second ultrasonic signal that is a reflected wave generated by reflecting the first ultrasonic signal in the subject and generate an electrical signal;
A receiver for receiving and amplifying the electrical signal;
A signal processing unit that calculates a nonlinear parameter in the subject based on an intensity ratio of an n-order frequency component (n is a natural number) of the electrical signal output by the receiving unit;
A display unit for displaying information of the nonlinear parameter;
An ultrasonic diagnostic apparatus comprising:

  2. 2. The ultrasonic diagnostic apparatus according to 1 above, wherein the transmitting element is also used as the receiving element.

  3. 3. The ultrasonic diagnostic apparatus according to 1 or 2, wherein the specific tissue is a low echo area.

4). An image processing unit for generating B-mode image information in the subject based on the electrical signal output by the receiving unit, and generating image data combined with the nonlinear parameter distribution information;
The ultrasonic diagnostic apparatus according to any one of claims 1 to 3, wherein the display unit displays the image data.

  5. 5. The ultrasonic diagnostic apparatus according to claim 1, wherein the signal processing unit calculates a non-linear parameter distribution of a tissue that is near an interface of the specific tissue and surrounds the specific tissue. .

  6). 6. The ultrasonic diagnostic apparatus according to any one of 1 to 5, wherein information of third-order or higher harmonics is used for calculation of the nonlinear parameter.

  7). The ultrasonic diagnostic apparatus according to any one of 1 to 6, wherein the specific tissue is a region surrounded by a boundary having a signal amplitude of the electrical signal equal to or greater than a predetermined value.

8). Edge detection means for performing edge detection processing for clarifying edges in the image with respect to the image data;
The ultrasonic diagnostic apparatus according to any one of 1 to 7, wherein the display unit displays the image data subjected to edge detection processing by the edge detection unit.

  9. 5. The non-linear parameter information obtained from a sound ray having a longest low echo area among non-linear parameter information obtained from continuous low echo areas is displayed. Ultrasound diagnostic equipment.

  Accurate measurement up to the depth of the subject without being affected by how the operator pressurizes, and easily diagnoses tissue properties with a uniform structure with little difference in acoustic impedance and no reflected waves. An ultrasonic diagnostic apparatus capable of measuring in real time can be provided.

1 is a diagram showing an external configuration of an ultrasonic diagnostic apparatus S. FIG. 2 is a block diagram showing an electrical configuration of an ultrasonic diagnostic apparatus S. FIG. 2 is a diagram showing the structure of an ultrasonic probe 2. FIG. It is a figure which shows the flow of an ultrasonic diagnosis. It is a schematic diagram showing the low echo area | region in a test object, the high echo area | region surrounding this low echo area | region, and the 1st ultrasound signal and the 2nd ultrasound signal which propagate each area | region. It is a schematic diagram which shows the time waveform example of a 2nd ultrasonic signal. It is a schematic diagram showing the frequency spectrum of a 2nd ultrasonic signal. FIG. 4 is a schematic diagram showing a state in which a low-echo area 33, which is a specific tissue, transmits a first ultrasonic signal to a position at the shortest distance as viewed from the ultrasonic probe 2. It is an example of a lookup table.

  Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to the embodiments described below. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted. Further, in this specification, as appropriate, a generic reference is used to indicate a reference numeral without a suffix, and an individual configuration is indicated by a reference numeral with a suffix.

  FIG. 1 is a diagram showing an external configuration of the ultrasonic diagnostic apparatus S in the embodiment, and FIG. 2 is a block diagram showing an electrical configuration of the ultrasonic diagnostic apparatus S in the embodiment. As shown in FIGS. 1 and 2, the ultrasonic diagnostic apparatus S transmits ultrasonic waves (first ultrasonic signals) having a narrow band of frequencies and a plurality of wave numbers to a subject such as a living body (not shown). At the same time, the ultrasonic probe 2 that receives the reflected wave (echo, second ultrasonic signal) of the ultrasonic wave reflected by the subject is connected to the ultrasonic probe 2 via the cable 3, By transmitting a transmission signal of an electrical signal to the acoustic probe 2 through the cable 3, the ultrasonic probe 2 transmits the first ultrasonic signal to the subject, and the ultrasonic probe 2 The ultrasonic diagnostic apparatus main body 1 is configured to image the internal state of the subject as an ultrasonic image based on the received second ultrasonic signal that is a reflected wave from the subject.

  FIG. 3 is a diagram showing the structure of the ultrasonic probe 2. The ultrasonic probe 2 is a device that transmits a first ultrasonic signal into a subject and receives a second ultrasonic signal that is a reflected wave from the subject with respect to the first ultrasonic signal. As the configuration of the ultrasonic probe 2, for example, as shown in FIG. 3A, a plurality of signals that can mutually convert signals between an electric signal and an ultrasonic signal by using a piezoelectric phenomenon. The piezoelectric element 22 is provided. That is, in the case of transmitting the first ultrasonic signal into the subject, the plurality of piezoelectric elements 22 convert the electrical signal transmitted via the cable 3 from the transmitting unit 12 of the ultrasonic diagnostic apparatus body 1 into the piezoelectric. In the case where the first ultrasonic signal is converted into the first ultrasonic signal by using the phenomenon, the first ultrasonic signal is transmitted into the subject, and the second ultrasonic signal is received from within the subject, the piezoelectric phenomenon is changed. By using this, the received second ultrasonic signal is converted into an electric signal, and the received signal is output to the receiving unit 13 of the ultrasonic diagnostic apparatus body 1 via the cable 3.

  The plurality of piezoelectric elements 22 combine the function as a transmitting element that transmits the first ultrasonic signal into the subject and the function of the receiving element that receives the second ultrasonic signal from within the subject. Yes.

  By applying the ultrasonic probe 2 to the subject, the first ultrasonic signal generated by the piezoelectric element 22 is transmitted into the subject, and the second ultrasonic signal from within the subject is transmitted by the piezoelectric element 22. Received.

  More specifically, for example, as shown in FIG. 3B, each of the plurality of piezoelectric elements 22 includes a signal electrode layer 222 made of a conductive material connected to the signal line 24 of the conductive line, and a signal electrode layer. The piezoelectric layer 221 is formed on the piezoelectric layer 221 and made of a piezoelectric material, and the ground electrode layer 223 is formed on the piezoelectric layer 221 and made of a conductive material. That is, each of the plurality of piezoelectric elements 22 includes a pair of first and second electrodes facing each other, and a piezoelectric portion made of a piezoelectric material is formed between the first and second electrodes.

  In the present specification, as described above, when referring generically, it is indicated by a reference symbol without a suffix, and when referring to an individual configuration, it is indicated by a reference symbol with a suffix. Further, the left subscript of the subscripts indicates the row number, and the right subscript indicates the column number. For example, the piezoelectric element 22-23 is the piezoelectric element 22 with row number 2 and column number 3.

  The plurality of piezoelectric elements 22 are disposed on one main surface of the flat plate-like acoustic braking member 21, and the acoustic matching layer 23 is laminated on the plurality of piezoelectric elements 22. The plurality of piezoelectric elements 22 are arranged on the acoustic braking member 21 with a predetermined gap (groove, gap, gap) between them in order to reduce mutual interference such as crosstalk. In order to further reduce the mutual interference, it is preferable to fill the gap with an ultrasonic absorber that absorbs ultrasonic waves. For example, a thermosetting resin such as a polyimide resin or an epoxy resin is used as the ultrasonic absorbing material.

  The acoustic braking member 21 is made of a material that absorbs ultrasonic waves, and absorbs ultrasonic waves radiated from the plurality of piezoelectric elements 22 toward the acoustic braking member 21. The acoustic braking member 21 is generally called a damper or a backing layer. A plurality of signal lines 24 (signal lines 24-11 to 24-46 in FIG. 3A) connected to the respective piezoelectric elements 22 penetrate the acoustic braking member 21. A plurality of ground wires (ground wires) connected to each of the piezoelectric elements 22 are omitted from the upper surface of each piezoelectric element 22 although illustration is omitted.

  The acoustic matching layer 23 is a member that matches the acoustic impedance of the piezoelectric element 22 and the acoustic impedance of the subject. Accordingly, the acoustic matching layer 23 is set so that the difference between the acoustic impedance of the piezoelectric element 22 and the acoustic impedance of the subject is minimized. The acoustic matching layer 23 may be composed of a single layer or may be composed of a plurality of layers. In addition, illustration of this acoustic matching layer 23 is abbreviate | omitted in FIG. 3 (A). Moreover, the acoustic matching layer 23 has a shape bulging in an arc shape, and may also function as an acoustic lens that converges ultrasonic waves transmitted toward the subject. It may be laminated on the acoustic matching layer 23.

  For example, as illustrated in FIG. 2, the ultrasonic diagnostic apparatus main body 1 includes an operation input unit 11, a transmission unit 12, a reception unit 13, an image processing unit 14, a display unit 15, a control unit 16, and a signal. A processing unit 17 and a storage unit 18 are provided.

  The operation input unit 11 accepts input of data such as a command instructing the start of diagnosis and personal information of the subject, for example, and is, for example, an operation panel or a keyboard provided with a plurality of input switches.

  The transmission unit 12 is a circuit that supplies a transmission signal of an electrical signal to the ultrasonic probe 2 via the cable 3 under the control of the control unit 16 and causes the ultrasonic probe 2 to generate a first ultrasonic signal. is there. The transmission unit 12 includes, for example, a transmission beam former circuit (not shown) that forms a transmission beam according to a transmission signal from the control unit 16.

  The receiving unit 13 is a circuit that receives a reception signal of an electrical signal from the ultrasound probe 2 via the cable 3 under the control of the control unit 16, and outputs the reception signal to the signal processing unit 17. The receiving unit 13 includes, for example, an amplifier that amplifies the received signal with a predetermined amplification factor set in advance.

  The image processing unit 14 is a circuit that generates an image (ultrasonic image) of the internal state in the subject based on the extracted reception signal of higher harmonics in the signal processing unit 17 under the control of the control unit 16. is there.

  The display unit 15 is a device that displays an ultrasonic image of the subject generated by the image processing unit 14 under the control of the control unit 16. The display unit 15 is, for example, a display device such as a CRT display, LCD, organic EL display, or plasma display, or a printing device such as a printer.

  The signal processing unit 17 has a function of signal processing the output from the receiving unit. Details will be described later.

  The storage unit 18 is configured by a RAM, a hard disk, and the like, and stores a result of signal processing by the signal processing unit 17 and an image obtained by performing image processing by the image processing unit 14.

  The control unit 16 includes, for example, a microprocessor, a storage element, and peripheral circuits thereof. The operation input unit 11, the transmission unit 12, the reception unit 13, the signal processing unit 17, the image processing unit 14, and the display unit 15 are included. Is a circuit that performs overall control of the ultrasonic diagnostic apparatus S by controlling each according to the function.

  In the ultrasonic diagnostic apparatus S having such a configuration, for example, when an instruction to start diagnosis is input from the operation input unit 11, a transmission signal of an electrical signal is generated by the transmission unit 12 under the control of the control unit 16. The generated electrical signal transmission signal is supplied to the ultrasonic probe 2 via the cable 3. More specifically, the transmission signal of this electric signal is supplied to the piezoelectric element 22 in the ultrasonic probe 2, and the piezoelectric element 22 expands and contracts in the thickness direction and ultrasonically vibrates. Due to this ultrasonic vibration, the piezoelectric element 22 emits a first ultrasonic signal. The first ultrasonic signal radiated from the piezoelectric element 22 toward the acoustic braking member 21 is absorbed by the acoustic braking member 21. The first ultrasonic signal radiated from the piezoelectric element 22 toward the acoustic matching layer 23 is radiated through the acoustic matching layer 23. For example, when the ultrasonic probe 2 is in contact with the subject, the first ultrasonic signal is transmitted from the ultrasonic probe 2 to the subject.

  Note that the ultrasound probe 2 may be used in contact with the surface of the subject, or may be used by being inserted into the subject, for example, being inserted into a body cavity of a living body. .

  Ultrasonic waves are sequentially transmitted from the piezoelectric elements 22 toward the subject, and the second ultrasonic signals generated by reflection from the subject are received by the plurality of piezoelectric elements 22 and converted into electrical signals.

  The electrical signal of the second ultrasonic signal extracted by the piezoelectric element 22 is received by the receiving unit 13 controlled by the control unit 16 via the cable 3. The reception unit 13 performs reception processing on the input reception signal, and the received electrical signal is output to the signal processing unit 17.

  The signal processing in the signal processing unit 17 will be described. An output signal from each piezoelectric element 22 processed by the receiving unit 13 and converted into an electrical signal is input to the signal processing unit 17.

The operator brings the ultrasonic probe 2 into contact with the subject and propagates the first ultrasonic signal into the subject so as to enter a specific region where the ultrasonic diagnosis is desired. As the first ultrasonic signal propagates through the subject, a reflected wave is generated at each location in the propagation path. The reflected waves generated at each location are superimposed to form a second ultrasonic signal, which is received by the plurality of piezoelectric elements 22. The sound pressure P of the reflected wave generated at each location is expressed by the following equation (1).
_{P = A (ρ 1 / ρ} 0) + B (ρ 1 / ρ 0) 2/2 (1)
Here, ρ ₁ is the density of the tissue at each location, and ρ ₀ is the density of the atmosphere. A represents a linear term of the relationship between P and [rho _1, B represents a nonlinear term. The coefficient ratio B / A has a value of a tissue-specific nonlinear parameter. For example, although it depends on the temperature, the value is about 5 for water and 8 to 11 for alcohol and oil.

  Since the reflected wave generated at each location generates high-order harmonics according to the nonlinearity derived from the tissue at each location in this way, the frequency characteristics of the reflected waves generated from each location are detected, and the coefficient If the ratio B / A can be determined, the tissue properties at each location can be diagnosed.

  A method for calculating the coefficient ratio B / A will be described. Since the relationship between the tissue density and the sound pressure is nonlinear as in the above equation (1), the reflected wave also has a nonlinear response. Specifically, the amplitude of the second ultrasonic signal is nonlinearly deformed with respect to the first ultrasonic signal, and a higher-order frequency is superimposed on the second ultrasonic signal together with the fundamental frequency of the first ultrasonic signal. Is done. That is, the nth order (n is a natural number) frequency is superimposed on the second ultrasonic signal. Since the coefficient ratio B / A between the coefficient A and the coefficient B found in the equation (1) depends on each tissue, the amplitude value of each n-th order frequency also has a value depending on each tissue. Therefore, by analyzing the frequency spectrum of the reflected wave received by the receiving unit 13, it is possible to perform a tissue property diagnosis that identifies what the tissue is.

  Since the frequency spectrum of the second ultrasonic signal that is the reflected wave has a shape in which the nonlinear response of each tissue is superimposed on the frequency spectrum of the first ultrasonic signal that is the incident wave, the frequency spectrum of the second ultrasonic signal is strictly The analysis is based on analyzing what nonlinear response is superimposed based on the frequency spectrum of the first ultrasonic signal. However, the frequency spectrum of the actual first ultrasonic signal has a finite driving time or a non-linear response to the piezoelectric element 22 itself even when the piezoelectric element 22 is driven using an electric signal having a single frequency. For example, the wave has a plurality of wave numbers, that is, a wave having a broad frequency. Therefore, it is not easy to analyze the nonlinear response of the second ultrasonic signal. On the other hand, the coefficient ratio B / A and the ratio of the peak value of each nth-order frequency in the frequency spectrum of the second ultrasonic signal correspond to each other one to one. Therefore, in the present embodiment, the peak value of each n-th order frequency in the frequency spectrum of the second ultrasonic signal is regarded as a feature value and compared to provide for tissue property diagnosis.

  The first ultrasound signal and the second ultrasound signal are affected by the tissue of the subject as they propagate through the subject. For example, the propagating ultrasonic signal is attenuated due to the influence of the attenuation rate depending on the tissue of the subject. Therefore, in order to perform a tissue property diagnosis, an analysis that also considers the attenuation rate is performed together with the frequency spectrum analysis of the second ultrasonic signal received by the receiving unit 13.

  The tissue property diagnosis using the coefficient ratio B / A is more useful for the specific diagnosis of the tissue having a small acoustic impedance mismatch than the conventional tissue property diagnosis for detecting the mismatch of the acoustic impedance. In this embodiment, a tissue characterization of a specific tissue with a small acoustic impedance mismatch is performed.

  Hereinafter, the flow of ultrasonic diagnosis in the present embodiment will be described with reference to FIG. The following operations are mainly performed when the control unit 16 receives an operation instruction from the operator.

  In the present embodiment, the tissue properties of a specific tissue (hereinafter also referred to as a low echo region) having a small acoustic impedance mismatch that exists in a tissue (hereinafter referred to as a high echo region) having a large acoustic impedance mismatch. Make a diagnosis. The method for performing the tissue characterization diagnosis of the low echo area is, first of all, a low echo area is first detected by using a technique for detecting an acoustic impedance mismatch as in the prior art. A diagnostic method for obtaining the ratio B / A or the like is employed.

  First, in step S1, the operator abuts the ultrasonic probe 2 on a place where the subject is desired to be diagnosed, and an instruction to transmit the first ultrasonic signal from the operation input unit 11 in the ultrasonic diagnostic apparatus main body 1. Enter. The operation input unit 11 receives the operator's input and transmits the operator's instruction content to the control unit 16. In response to this, the control unit 16 transmits the first ultrasonic signal into the subject.

  Next, in step S2, the second ultrasonic signal formed by integrating the reflected waves generated in the tissues at each location in the subject reaches the piezoelectric element 22 of the ultrasonic probe 2 and is piezoelectric. The receiving unit 13 receives the electrical output generated in the element 22 according to an instruction from the control unit 16 and converts it into an electrical signal.

  Next, in step S3, the received electrical signal is transmitted to the signal processing unit 17, the amplitude of the electrical signal transmitted in the signal processing unit 17 is analyzed in time series, and the amplitude of the second ultrasonic signal is relatively small. A low echo area which is an area is detected. Hereinafter, a description will be given with reference to FIGS.

  FIG. 5 is a schematic diagram showing a low echo area 33 in the subject, a high echo area 32 surrounding the low echo area 33, and a first ultrasonic signal and a second ultrasonic signal propagating through each area. It is.

  FIG. 6 is a schematic diagram illustrating a time waveform example of the second ultrasonic signal. The horizontal axis represents the time of the second ultrasonic signal, and the vertical axis represents the amplitude of the second ultrasonic signal.

  In FIG. 5, the first ultrasonic signal 31 transmitted from the ultrasonic probe 2 propagates through the high echo area 32 in the subject from the right side in the figure, and is a specific area to be subjected to ultrasonic diagnosis. It enters the echo area 33 and again enters the high echo area 32 and propagates. As the first ultrasonic signal 31 propagates through each region, a reflected wave is generated at an acoustic impedance mismatching portion existing in the region. The integration of the generated reflected waves becomes the second ultrasonic signal 34 and propagates to the right side in the figure and is received by the ultrasonic probe 2.

  The time waveform of the reflected wave from the low echo area 33 and the high echo area 32 in the second ultrasonic signal received by the ultrasonic probe 2 is a time having characteristics of the high echo area 32 as shown in FIG. The time waveform having the characteristics of the waveform, the low echo area 33, and the time waveform having the characteristic of reflection from the boundary between the high echo area 32 and the low echo area 33 is obtained.

  Here, the high echo region 32 refers to a region where the value of the predetermined average line 43 of the absolute value of the time waveform of the reflected wave exceeds the predetermined value 40, and the low echo region 33 refers to the absolute value of the time waveform of the reflected wave. A region where the value of the predetermined average line 43 is a predetermined value 40 or less.

  In the high echo region 32, the amplitude of the time waveform increases because the acoustic impedance mismatch is large, and in the low echo region 33, the signal amplitude of the time waveform decreases because the acoustic impedance mismatch is small. Using this difference, a low echo area 33 is detected by extracting an area having an amplitude equal to or smaller than a predetermined value. This predetermined value may be selected and adjusted by the surgeon so as to match the region to be extracted, or may be automatically set according to the average amplitude of the sound ray data for one screen.

  When the first ultrasonic signal passes through the low echo area 33, the boundary closer to the ultrasonic probe 2 among the two boundaries of the low echo area 33 and the high echo area 32 is the start point 41, and the far side Is called the end point 42.

  Thereafter, a non-linear parameter is calculated by performing frequency analysis of the portion of the high echo region 32 surrounding the extracted low echo region 33, that is, in the vicinity of the interface of the specific tissue which is the low echo region 33 and surrounding the specific tissue. I will do it.

  Next, in step S4, the signal processing unit 17 uses the position immediately before the first ultrasonic signal enters the specific tissue as the time waveform data in the vicinity of the interface of the specific tissue which is the low echo region 33, that is, the start point 41. The data of the time waveform (also referred to as the immediately preceding waveform) before a predetermined time is acquired from the data, and frequency analysis is performed by applying a filter such as FFT (Fast Fourier transform) or FIR (Finite impulse response). I do. In the frequency analysis, the signal amplitude is calculated for each frequency included in the second ultrasonic signal, and for example, an analysis result as shown in FIG. 7A can be obtained. FIG. 7A is a schematic diagram showing the frequency spectrum of the second ultrasonic signal.

  In FIG. 7A, the existence of a fundamental frequency f1 having a signal amplitude value p1, a second harmonic frequency f2 having a signal amplitude value p2, and a third harmonic frequency f3 having a signal amplitude value p3 is confirmed.

  The smaller the range of the space from which the time waveform for performing frequency analysis is acquired, the higher the spatial resolution for performing tissue property diagnosis. On the other hand, the larger the space range, the more accurate frequency analysis can be performed. Accordingly, since there is an appropriate range in the space for acquiring the time waveform for performing frequency analysis, the second ultrasonic signal is reflected from the appropriate range for a predetermined time for obtaining the immediately preceding waveform. This corresponds to time, for example, 2 μs. When performing frequency analysis by FFT, the target data is selected such that the number of time waveform data is the factorial of two.

  Next, in step S5, the signal processing unit 17 calculates a ratio (also referred to as a harmonic ratio) between the obtained signal amplitude of the fundamental wave and the signal amplitude of a predetermined nth-order harmonic. For example, the signal amplitude ratio between the fundamental wave and the third harmonic is calculated to obtain p3 / p1. By using the third harmonic having a higher order than the second harmonic, separation from the fundamental wave component is facilitated, and the coefficient ratio B / A, which is a nonlinear parameter, can be calculated with higher accuracy.

  Next, in step S6, the signal processing unit 17 outputs the first ultrasonic signal from the specific tissue as time waveform data in the vicinity of the interface of the specific tissue, which is the low echo region 33, as in step S4. Data of a time waveform immediately after a predetermined time from the end point 42, that is, a time waveform (also referred to as a waveform immediately after) is acquired, and a frequency analysis is performed by applying a filter such as FFT or FIR. For example, an analysis result as shown in FIG. 7B can be obtained. FIG. 7B is a schematic diagram showing the frequency spectrum of the second ultrasonic signal. In FIG. 7B, the presence of the fundamental frequency f1 having the signal amplitude value q1, the second harmonic frequency f2 having the signal amplitude value q2, and the third harmonic frequency f3 having the signal amplitude value q3 is confirmed.

  The predetermined time for obtaining the waveform immediately after is, for example, 2 μs for the same reason as described above. In this case as well, when performing frequency analysis by FFT, the target data is selected so that the number of time waveform data is a factorial of two.

  As shown in FIG. 5, the non-linear parameter is calculated at the position of the first ultrasonic wave so that the first ultrasonic signal 31 is before and after the line 50 having the longest acoustic ray propagating through the low echo region 33. A sound ray used for calculation is selected so as to select a position immediately before the signal 31 is incident on the specific tissue and a position immediately after the first ultrasonic signal 31 is emitted from the low echo area 33 which is the specific tissue. It is preferable. This is because the coefficient ratio B / A, which is a non-linear parameter, can be calculated more accurately than in the case where the length of the sound ray in which the first ultrasonic signal 31 propagates through the low echo area 33 is short as in the lines 51 and 52. is there. Specifically, the position where the time width of the low echo area 33 of the second ultrasonic signal 34 shown in FIG. 6 is the longest is selected.

  As shown in FIG. 8, the non-linear parameter is calculated by selecting the line having the longest sound ray propagating through the low echo region 33 even when the low echo region 33 as a specific tissue has a flat shape. It is preferable to do. For the same reason as described above, the coefficient ratio B / A, which is a nonlinear parameter, can be calculated with high accuracy.

  The sound ray used for the analysis may be arbitrarily selected by the operator according to the guide displayed on the screen, but the device compares the length of the low echo area in the sound ray with the nearby sound ray, Preferably, it is automatically selected.

  Next, in step S7, the signal processing unit 17 calculates a harmonic ratio between the obtained signal amplitude of the fundamental wave and the signal amplitude of a predetermined n-order harmonic. For example, the signal amplitude ratio between the fundamental wave and the third harmonic is calculated to obtain q3 / q1.

  Next, in step S <b> 8, the signal processing unit 17 propagates only the high-echo region 32 and propagates both the low-echo region 33 and the high-echo region 32 and the harmonic ratio of the immediately preceding waveform received by the receiving unit 13. Then, the ratio of the harmonic ratio of the waveform immediately after being received by the receiving unit 13 is calculated, and the rate of increase of the harmonic ratio (p3 · q1) / (p1 · q3) is calculated.

  Next, in step S9, the signal processing unit 17 calculates the coefficient ratio B / A of the low echo area 33 from the position of the start point 41, the position of the end point 42, and the rate of increase of the harmonic ratio. The coefficient ratio B / A can be calculated by performing a piezoelectric wave analysis using the finite element method. However, the time for executing the analysis of the finite element method using a computer is actually in the field of ultrasonic diagnosis. In some embodiments, a lookup table is used because it may not be as fast as real time. Specifically, the control unit 16 instructs the signal processing unit 17 to set the coefficient ratio B / A for each combination of the position of the start point 41, the position of the end point 42, and the increase rate of the harmonic ratio in advance. The calculation result is stored in the storage unit 18 in advance.

  FIG. 9 shows an example of a lookup table. The horizontal axis of the lookup table represents the distance from the ultrasound probe 2 to the start point position, and the vertical axis represents the distance from the ultrasound probe 2 to the end point position. In this look-up table, when the coefficient ratio B / A and the attenuation rate are predetermined values, the rate of increase of the harmonic ratio is 30 mm when the distance to the start point position is 30 mm and the distance to the end point position is 40 mm. The value is 3.0. If the combination of the coefficient ratio B / A and the attenuation rate is different, the rate of increase of the harmonic ratio also becomes a different value. In this way, the control unit 16 uses the lookup table in which the distance to the start point position, the distance to the end point position, and the value of the increase rate of the harmonic ratio are the same values as those obtained in step S8. Is obtained by searching the storage unit 18.

  Next, in step S10, the signal processing unit 17 obtains the coefficient ratio B / A and the attenuation rate of the low echo area 33 in the corresponding sound ray from the look-up table obtained by the search.

  As described above, since the ultrasound probe 2 has the piezoelectric element 22 two-dimensionally, the first ultrasound signal can be obtained by forming sound rays from a plurality of directions with respect to the same echo area. The coefficient ratio B / A and the attenuation rate are calculated for the different start points 41 and end points 42 in the same manner as described above, and information on the three-dimensional distribution of the low echo area 33 is obtained from the coefficient ratio B / A. It is done.

  Next, in step S11, the image processing unit 14 generates B-mode image information from the amplitude information of the second ultrasonic signal obtained in step S3, as in the conventional technique. Then, the image processing unit 14 synthesizes the obtained B-mode image information and the information on the distribution of the coefficient ratio B / A, which is the nonlinear parameter of the low echo area 33 obtained in step S10, to obtain the image data. Generate. In this case, it is preferable that the B / A distribution information is generated as color information, such as color Doppler display, and is combined with black and white B-mode image information.

  Next, in step S12, in order to clarify the boundary between the low echo area 33 and the high echo area 32 using the edge detection means from the information of the obtained coefficient ratio B / A which is a nonlinear parameter, image data An edge detection process for detecting the edge of the boundary is performed, and the detected edge is added to the image data to obtain ultrasonic image data.

  Edge detection is performed using edge detection software employing a known snake or region growing method.

  Next, in step S <b> 13, the control unit 16 displays on the display unit 15 an ultrasonic image in the subject whose edge has been clarified.

  Note that the B / A information display method may be a method in which B / A distribution information as described above is imaged and combined with B-mode image information, but only information on coefficient ratio B / A, which is a non-linear parameter. But you can. In this case, the information on the coefficient ratio B / A, which is a nonlinear parameter that is information on the three-dimensional distribution of the low echo area 33 generated by the signal processing unit 17, is not the image information of the distribution but the selected numerical value itself. Is preferably displayed. As described above, it is preferable to use a numerical value obtained by analyzing a sound ray that has the longest propagation length in the low echo area. Further, information on the coefficient ratio B / A, which is a nonlinear parameter, is displayed on the display unit 15 without going through the image processing unit 14.

  As described above, according to the present embodiment, the second ultrasonic signal is received by the receiving unit, an electric signal is generated, and based on the intensity ratio of the nth-order frequency component (n is a natural number) of the electric signal. The signal processing unit calculates the distribution of nonlinear parameters in the subject, the image processing unit generates image data, and the display unit images and displays the image data, so the conventional acoustic impedance mismatch is used. Tissue with a uniform structure that can accurately measure to the deep part of the subject without being affected by how the operator presses the ultrasound diagnostic device, and has a small difference in acoustic impedance and no reflected waves It is possible to provide an ultrasonic diagnostic apparatus that can easily perform a property diagnosis of a (low echo area) and can measure in real time.

  In addition, according to the present embodiment, since the region where the signal amplitude of the electric signal has a value equal to or smaller than a predetermined value is the specific tissue, the region is clarified using the conventional method of detecting acoustic impedance mismatch. Can be specified.

  Further, according to the present embodiment, the image data that has the edge detection unit that performs the edge detection process for clarifying the edge in the image with respect to the image data, and the display unit receives the image data that has been subjected to the edge detection process by the edge detection unit. Is displayed, the surgeon can clearly recognize the specific tissue on the display unit.

  Further, according to the present embodiment, the third harmonic having a higher order than the second harmonic is used for calculating the coefficient ratio B / A, which is a linear parameter, so that the separation from the fundamental wave component is facilitated. Nonlinear parameters can be calculated with high accuracy.

  Further, according to the present embodiment, the non-linear parameter is selected by selecting the sound ray used for the calculation so that the length of the sound ray propagating the first ultrasonic signal 31 through the low echo region 33 is the longest. The coefficient ratio B / A can be calculated with high accuracy.

DESCRIPTION OF SYMBOLS 1 Ultrasonic diagnostic apparatus main body 2 Ultrasonic probe 3 Cable 11 Operation input part 12 Transmission part 13 Reception part 14 Image processing part 15 Display part 16 Control part 17 Signal processing part 18 Memory | storage part 21 Acoustic braking member 22 Piezoelectric element 23 Acoustics Matching layer 24 Signal line 31 First ultrasonic signal 32 High echo area 33 Low echo area 34 Second ultrasonic signal 41 Start point 42 End point 222 Signal electrode layer 223 Ground electrode layer S Ultrasonic diagnostic apparatus

Claims (9)

A plurality of transmitting elements for transmitting the first ultrasonic signal to a specific tissue in the subject;
A transmission unit for driving the transmission element;
A plurality of receiving elements that receive a second ultrasonic signal that is a reflected wave generated by reflecting the first ultrasonic signal in the subject and generate an electrical signal;
A receiver for receiving and amplifying the electrical signal;
A signal processing unit that calculates a nonlinear parameter in the subject based on an intensity ratio of an n-order frequency component (n is a natural number) of the electrical signal output by the receiving unit;
A display unit for displaying information of the nonlinear parameter;
An ultrasonic diagnostic apparatus comprising:   The ultrasonic diagnostic apparatus according to claim 1, wherein the transmitting element is also used as the receiving element.   The ultrasonic diagnostic apparatus according to claim 1, wherein the specific tissue is a low echo area. An image processing unit for generating B-mode image information in the subject based on the electrical signal output by the receiving unit, and generating image data combined with the nonlinear parameter distribution information;
The ultrasonic diagnostic apparatus according to claim 1, wherein the display unit displays the image data.   5. The ultrasonic diagnosis according to claim 1, wherein the signal processing unit calculates a non-linear parameter distribution of a tissue that is in the vicinity of an interface of the specific tissue and surrounds the specific tissue. 6. apparatus.   The ultrasonic diagnostic apparatus according to claim 1, wherein third-order or higher harmonic information is used to calculate the nonlinear parameter.   The ultrasonic diagnostic apparatus according to claim 1, wherein the specific tissue is a region surrounded by a boundary in which a signal amplitude of the electrical signal has a value greater than or equal to a predetermined value. Edge detection means for performing edge detection processing for clarifying edges in the image with respect to the image data;
The ultrasonic diagnostic apparatus according to claim 1, wherein the display unit displays the image data subjected to edge detection processing by the edge detection unit.   5. The non-linear parameter information obtained from a sound ray having a longest low echo area among non-linear parameter information obtained from continuous low echo areas is displayed. The ultrasonic diagnostic apparatus as described.

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