JP2010046284A - Ultrasonic diagnostic apparatus and automatic diagnostic parameter measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic diagnostic apparatus capable of automatically measuring the deceleration time DCT of E waves with high reliability even when the influence of valves or chordae tendineae is mixed in a Doppler spectrum from a bloodstream. <P>SOLUTION: The ultrasonic diagnostic apparatus includes: a Doppler processing section for generating the Doppler spectrum of an endocardial bloodstream; a trace waveform generation section for generating the time-based change of the Doppler spectrum as a trace waveform; a peak waveform detection section for detecting a prescribed peak waveform from the trace waveform; an evaluation waveform generation section for removing the variation and generating a deceleration waveform for evaluation when it is determined that the waveform of the deceleration area of the peak waveform is varied due to the influence other than the bloodstream, and defining the detected waveform of the deceleration area of the peak waveform as the deceleration waveform for the evaluation in the other cases; and a deceleration time calculation section for calculating the deceleration time of the prescribed peak waveform from the deceleration waveform for the evaluation. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ultrasonic diagnostic apparatus and a diagnostic parameter automatic measurement method, and more particularly to an ultrasonic diagnostic apparatus and a diagnostic parameter automatic measurement method capable of measuring a blood flow velocity in a living body based on Doppler information.

  An ultrasonic diagnostic apparatus is an apparatus for transmitting an ultrasonic signal generated from a piezoelectric vibrator built in an ultrasonic probe into a subject and imaging a reflected signal from the subject to perform various diagnoses. is there. B-mode images and color Doppler images are widely used as diagnostic images.

  On the other hand, there is a Doppler spectrum method as a method for quantitatively and accurately measuring blood flow information in a blood vessel or heart of a subject. In the Doppler spectrum method, an ultrasonic beam is transmitted in a desired direction in a blood vessel or heart, and a signal having a desired depth is cut out from a received signal by a range gate. An operation such as FFT is performed on the cut received signal sequence to obtain a Doppler spectrum, and blood flow information such as blood flow velocity and strength of velocity component is obtained from the obtained Doppler spectrum (Doppler frequency).

  It is necessary to specify in advance which position in the heart or blood vessel the blood flow information is to be obtained, but this specification is usually performed using a B-mode image. A specific direction or range is designated on the B-mode image, and a received signal from the designated direction and range is extracted to obtain a Doppler spectrum of that part.

  The Doppler spectrum obtained by the ultrasonic diagnostic apparatus is usually imaged with time on the horizontal axis and frequency on the vertical axis, and the intensity for each frequency component is expressed as the luminance of the image. This image is called a Doppler image or Doppler waveform image.

  In addition, the maximum blood flow velocity Vp and the average flow velocity Vm of the blood flow are obtained from the Doppler spectrum, and a waveform with the horizontal axis representing time and the vertical axis representing the maximum flow velocity Vp and average flow velocity Vm is also obtained. This waveform is called a trace waveform. The trace waveform is stored in an appropriate storage unit such as a hard disk and displayed on the display unit of the ultrasonic diagnostic apparatus as necessary.

  When evaluating or diagnosing the function of the heart, the diagnostic parameters obtained from the above trace waveform are very useful.

  For example, when evaluating cardiac function, trace waveforms are obtained for the left ventricular inflow (LV-Inflow) flow rate, pulmonary venous blood flow (PV) flow rate, etc., and various diagnostic parameters are obtained from the trace waveform. .

  For the left ventricular inflow blood flow waveform, the amplitude of the E wave (expansion early wave) or A wave (atrial systolic wave) (the amplitude corresponds to the blood flow velocity), the amplitude ratio E / of the E wave and the A wave A, DCT (deceleration time of E wave), etc. are widely used as diagnostic parameters.

  In addition, for the pulmonary vein blood flow waveform, the amplitude of the S wave (systolic antegrade blood flow), D wave (diastolic antegrade blood flow), AR wave (systolic retrograde blood flow), etc. It is used as a diagnostic parameter.

  Conventionally, these diagnostic parameters have been read from the trace waveform by a manual operation by a user such as a doctor or an engineer. For example, when reading diagnostic parameters from the left ventricular inflow blood flow waveform, two time cursors are placed on the trace waveform statically displayed on the display unit, and the positions of the two time cursors are the peak of E wave and A wave. Each user matches. Then, the apparatus reads the amplitude of the E wave and the amplitude of the A wave at the positions of the two time cursors, and displays them on the display unit as diagnostic parameters. In addition, the amplitude ratio E / A is calculated from the amplitudes of the read E wave and A wave, and displayed as a diagnostic parameter.

  Further, when obtaining the deceleration time DCT, one time cursor is adjusted to the peak of the E wave, and the other time cursor is adjusted to a position where the E wave is decelerated and becomes almost zero. The device then reads the time difference between the two time cursors and displays the diagnostic parameter DCT.

  Thus, conventionally, since the diagnosis parameter is obtained by the manual operation of the user, not only the operation becomes complicated, but it takes much time to obtain the diagnosis parameter.

  Further, although the Doppler spectrum itself can be obtained almost in real time, it is practically impossible to obtain the diagnostic parameter in real time because the manual operation is involved as described above.

  In order to eliminate such an inconvenience, a technique for automatically measuring a diagnostic parameter is disclosed in Patent Document 1 and the like.

Patent Document 1 discloses a technique for obtaining a plurality of pairs of local maximum points and local minimum points from a trace waveform, and automatically determining peak times and peak values of E wave and A wave from these pairs. A technique is also disclosed in which a tangent is set with respect to a descending curve from the peak value of the E wave, and the deceleration time DCT is obtained from the interval between the time when the tangent and the baseline intersect and the peak time of the E wave.
JP 2006-102489 A

  However, the Doppler spectrum obtained by the ultrasonic diagnostic apparatus does not necessarily include only necessary information.

  For example, when trying to obtain velocity information of the left ventricular inflow blood flow, a Doppler spectrum is often acquired from the reflected signal near the left ventricular entrance, but a valve called a mitral valve is located between the left ventricle and the left atrium. There are numerous chords that support the mitral valve. For this reason, in the Doppler spectrum to be measured, in addition to the Doppler signal of the left ventricular inflow blood flow to be evaluated, Doppler signals corresponding to the movements of the mitral valve and the chord are mixed as unnecessary Doppler signals.

  For example, when the E-wave deceleration time DCT of the left ventricular inflow blood flow is to be measured, the ratio of the influence of the mitral valve and the chord to the measurement target range is about 30%. It has been broken.

  For this reason, automatic measurement of DCT by the conventional method disclosed in Patent Document 1 and the like has been a difficult situation as a practical problem.

  E-wave deceleration time DCT is one of the important diagnostic parameters for evaluating cardiac function, and highly reliable DCT automatic measurement technology is strongly demanded.

  The present invention has been made in view of the above circumstances, and even when the influence of a valve or chordae is mixed in the Doppler spectrum from the bloodstream, the deceleration time DCT of the E wave is highly reliable. An object is to provide an ultrasonic diagnostic apparatus and a diagnostic parameter automatic measurement method capable of automatic measurement.

  In order to solve the above problems, an ultrasonic diagnostic apparatus according to the present invention includes a Doppler processing unit that generates a Doppler spectrum from an ultrasonic signal reflected from a predetermined site in the heart, and a predetermined spectrum component in the Doppler spectrum. A trace waveform generation unit that generates a temporal change as a trace waveform, a peak waveform detection unit that detects a predetermined peak waveform from the generated trace waveform, and a waveform in a deceleration region of the peak waveform due to an effect other than blood flow When it is determined that there is a fluctuation, the fluctuation waveform is removed and an evaluation deceleration waveform is generated. In other cases, the detected waveform of the peak waveform in the deceleration area is used as the evaluation deceleration waveform. And a deceleration time calculation unit for calculating a deceleration time of the predetermined peak waveform from the evaluation deceleration waveform, That.

  The diagnostic parameter automatic measurement method according to the present invention generates a Doppler spectrum from an ultrasonic signal reflected from a predetermined site in the heart, and generates a temporal change of a predetermined spectrum component in the Doppler spectrum as a trace waveform. Then, when a predetermined peak waveform is detected from the generated trace waveform and it is determined that the waveform in the deceleration region of the peak waveform has a variation due to an effect other than blood flow, this variation is removed and the evaluation deceleration is performed. A waveform is generated; otherwise, the extracted peak waveform is used as the evaluation deceleration waveform, and the deceleration time of the predetermined peak waveform is calculated from the evaluation deceleration waveform. To do.

  According to the ultrasonic diagnostic apparatus and the diagnostic parameter automatic measurement method according to the present invention, the E-wave deceleration time DCT is calculated even when the influence of a valve or chordae is mixed in the Doppler spectrum from the bloodstream. Automatic measurement with high reliability.

  Embodiments of an ultrasonic diagnostic apparatus and a diagnostic parameter automatic measurement method according to the present invention will be described with reference to the accompanying drawings.

(1) Configuration FIG. 1 is a block diagram illustrating a configuration example of an ultrasonic diagnostic apparatus 1 according to the present embodiment. The ultrasonic diagnostic apparatus 1 includes an ultrasonic probe 2, a reference signal generation unit 3, a transmission / reception unit 4, a system control unit 5, an operation unit 6, a Doppler signal detection unit 7, a Doppler processing unit 8, a color Doppler data generation unit 9, B A mode data generation unit 10, a display unit 11, a storage unit 12, a blood flow evaluation unit 20, and the like are provided.

  The ultrasonic probe 2 is a device that transmits and receives ultrasonic waves by bringing a tip portion into contact with the body surface of a subject, and has a plurality of minute piezoelectric transducers arranged one-dimensionally or two-dimensionally at the tip portion. is doing. The piezoelectric vibrator is an electroacoustic transducer, which converts an electrical signal into an ultrasonic pulse during transmission, and converts an ultrasonic signal reflected from the subject into an electrical signal during reception. The ultrasonic probe 2 includes linear scanning, sector scanning, convex scanning, and the like, and is selected according to the diagnostic region. The ultrasonic probe 2 in which the piezoelectric vibrators are two-dimensionally arranged can perform so-called three-dimensional scanning. The ultrasonic probe 2 is connected to the transmission / reception unit 4 via a cable.

  The transmission / reception unit 4 has a transmission unit and a reception unit (both not shown) as its internal configuration. The transmission unit generates a rate pulse that determines the repetition period of the transmission pulse based on the reference signal (continuous wave or reference clock) supplied from the reference signal generator 3. Further, a delay time corresponding to the scanning angle (transmission scanning angle) of the ultrasonic beam is given to the rate pulse, and then the rate pulse is converted into a driving pulse by a pulser (not shown). It is supplied to each piezoelectric vibrator.

  On the other hand, the receiving unit converts the electrical signal output from each piezoelectric transducer of the ultrasonic probe 2 into a digital signal, and then applies and adds a delay amount corresponding to the scanning angle (reception scanning angle) of the ultrasonic beam. By doing so, a beamformed received signal is obtained.

  The system control unit 5 determines the parameters related to beam scanning and transmission / reception based on information set or input by the user on the operation unit 6, and sets these specifications for the transmission / reception unit 4. Yes.

  The reception signal output from the transmission / reception unit 4 is output to the B-mode data generation unit 10 and the Doppler signal detection unit 7.

  In the B-mode data generation unit, for example, amplitude detection is performed on the received signal to generate range-amplitude information data (that is, B-mode data) for each scanning angle necessary for displaying the B-mode image and temporarily store it in the storage unit 12. Is preserved. The B mode data is read from the storage unit 12 and displayed on the display unit 11 as a B mode image. Incidentally, FIG. 2 is a diagram schematically showing a B-mode image of the heart as a display example of the B-mode image.

  On the other hand, the Doppler signal detection unit 7 performs phase detection on the received signal, and supplies the phase detection signal to the color Doppler data generation unit 9 and the Doppler processing unit 8.

  The color Doppler data generation unit 9 obtains an autocorrelation value from the phase detection signal, calculates an average Doppler frequency (amount corresponding to the average blood flow velocity) and a variance value of the frequency from the autocorrelation value, and outputs these color Doppler data. The data is temporarily stored in the storage unit 12 together with the corresponding scan angle data. When color Doppler display is performed, color Doppler data is read from the storage unit 12 and a color luminance display corresponding to the average blood flow velocity is displayed on a two-dimensional image similar to the B-mode image.

  The Doppler processing unit 8 generates a Doppler spectrum by performing frequency analysis processing such as FFT on the phase detection signal in order to evaluate the blood flow velocity in detail. The Doppler spectrum is obtained from data obtained by designating a specific part in a subject by a scanning angle and a range and collecting a reflection signal from the specific part for a predetermined period.

  The Doppler spectrum is usually imaged with time on the horizontal axis and frequency on the vertical axis, and the intensity of each frequency component is expressed as the luminance of the image. This image is called a Doppler image or Doppler waveform image. The Doppler spectrum output from the Doppler processing unit 8 is stored in the storage unit 12 and displayed on the display unit 11 as a Doppler image.

  Further, a maximum blood flow velocity Vp and an average flow velocity Vm of the blood flow are obtained from the Doppler spectrum, and a waveform is also generated in which the horizontal axis represents time and the vertical axis represents the maximum flow velocity Vp and average flow velocity Vm. This waveform is called a trace waveform. The trace waveform generation unit 21 of the blood flow evaluation unit 20 reads the Doppler spectrum from the storage unit 12 and generates a trace waveform from the Doppler spectrum. The generated trace waveform is again stored in the storage unit 12 and displayed on the display unit 11 as necessary.

  The ultrasonic diagnostic apparatus 1 according to the present embodiment has a function of automatically measuring diagnostic parameters useful for diagnosis from a blood flow trace waveform, and the blood flow evaluation unit 20 realizes this automatic measurement function. ing. The blood flow evaluation unit 20 includes a peak waveform detection unit 22, an evaluation waveform generation unit 23, a deceleration time calculation unit 24, a parameter storage unit 25, an electrocardiographic waveform input unit 26 and the like in addition to the trace waveform generation unit 21 described above. Details of the functions of these units will be described later.

(2) Automatic measurement of diagnostic parameters FIG. 2 is a diagram illustrating a schematic B-mode image of the heart and a blood flow evaluation site designated on the B-mode image. FIG. 2 shows an example in which the vicinity flowing into the left ventricle from the left atrium is specified by the scanning angle and the range gate, and the left ventricular inflow blood flow is the evaluation target.

  Although the blood flow evaluation target of the ultrasonic diagnostic apparatus 1 according to the present embodiment is not limited to the left ventricular inflow blood flow, the evaluation of the left ventricular inflow blood flow is very important in evaluating cardiac function. Therefore, in the following description, the left ventricular inflow blood flow will be mainly described as an example of an evaluation target.

  The heart repeatedly contracts and dilates, but blood flows from the left atrium to the left ventricle during diastole. The Doppler spectrum obtained by observing the blood flow velocity in the vicinity of the entrance of the left ventricle is the Doppler spectrum of the left ventricular inflow blood flow. It is a waveform.

  FIG. 3 shows an example of the trace waveform of the left ventricular inflow blood flow along with signals indicating the diastole and the systole of the heart. Signals indicating the diastole and the systole can be obtained from an electrocardiogram waveform (also referred to as an ECG waveform) output from the electrocardiograph 100 (see FIG. 1) or an electrocardiogram.

  The vertical axis of the trace waveform of the left ventricular inflow blood flow (hereinafter simply referred to as the trace waveform) indicates the blood flow velocity of the left ventricular inflow blood flow obtained from the Doppler frequency (the unit shown in FIG. 3 is cm / s). The horizontal axis is time.

  As shown in FIG. 3, there are two characteristic peak waveforms of the E wave and the A wave in the trace waveform in the diastole. In the early diastole, the left ventricle expands to reduce the left ventricular pressure, and blood flows from the left atrium into the left ventricle. The waveform corresponding to the blood flow at this time is an E wave (expansion early wave). In the late phase of diastole, the left atrium contracts and pushes the blood remaining in the left atrium into the left ventricle. The waveform corresponding to the blood flow at this time is an A wave (atrial systolic wave). That is, the E wave represents the left ventricular inflow due to left ventricular dilation, and the A wave represents the left ventricular inflow due to left atrial contraction.

  Diagnostic parameters based on the diastolic left ventricular inflow waveform include E wave peak value (Ep), A wave peak value (Ap), and ratio of E wave peak value to A wave peak value (E / A). E-wave deceleration time DCT (Deceleration Time) and the like. The E wave deceleration time DCT is defined as the time from the peak of the E wave until the blood flow velocity becomes zero. Cardiac function can be evaluated by the values of these diagnostic parameters.

  By the way, as shown in FIG. 2, there is a valve called a mitral valve in the vicinity of the measurement site of the left ventricular inflow blood flow (between the left atrium and the left ventricle), and also for supporting the mitral valve. There are numerous chords. Since the mitral valve and chordae are accompanied by movement, the Doppler spectrum and trace waveform are mixed with fluctuation waveforms (unnecessary waveforms) due to the influence of the valves and chordae as influences other than blood flow.

  Of the four diastolic trace waveforms shown in FIG. 3, the three diastolic waveforms from the left are dominated by blood flow waveforms (E wave and A wave). In the deceleration period of the E wave, a noticeable unwanted waveform that is considered to be the effect of the valve and chords is observed.

  As a result of verifying a large number of actually measured data, it was found that about 30% of the diastolic trace waveforms include trace waveforms affected by valves and chords as shown at the right end of FIG. ing.

  If a diagnostic parameter is automatically measured based on a waveform affected by a valve or chordae, an incorrect diagnostic parameter is output. In particular, the error is large with respect to automatic measurement of the E-wave deceleration time DCT. In the following explanation, among the diagnostic parameters, the focus is on the automatic measurement of the E-wave deceleration time DCT, how to eliminate the influence of valves and chordae, and how to obtain a reliable deceleration time DCT. Whether to obtain by automatic measurement will be described sequentially.

  FIG. 4 is a flowchart showing an example of an automatic measurement process for evaluation parameters (particularly, E-wave deceleration time DCT) according to the present embodiment.

  In step ST1, an ultrasonic beam scanning angle and a range gate are set at a predetermined site in the heart (for example, near the left ventricular entrance), and a Doppler spectrum is generated from the ultrasonic signal reflected from the site. The Doppler spectrum is generated by the Doppler processing unit 8.

  In step ST2, a trace waveform is generated from the Doppler spectrum. Specifically, a peak of the Doppler spectrum is detected and a waveform traced in the time axis direction is generated. The trace waveform is generated by the trace waveform generation unit 21 of the blood flow evaluation unit 20.

  In step ST3, a predetermined peak waveform, that is, an E wave and an A wave is detected from the trace waveform (in this case, the trace waveform of the left ventricular inflow blood flow).

  For detection of E wave and A wave, for example, a technique disclosed in Patent Document 1 can be used. In this technique, first, 40% of the cardiac cycle is set as a reference position from the R wave of an electrocardiogram signal (ECG signal). This reference position is regarded as the transition time from the systole to the diastole. Next, the local maximum / minimum pair of the trace waveform is searched to detect two coordinates having the maximum maximum value and the second maximum maximum value, and the maximum coordinate subsequent to the reference position is determined as an E wave. A peak is selected, and the maximum coordinate following the E wave peak is selected as the A wave peak. In addition to this, Patent Document 1 discloses a method for obtaining the above reference position using a cardiac sound waveform (PCG waveform), a method for obtaining coordinates of each peak of E wave and A wave from only a trace waveform, and the like. Yes. In step ST3, the peak coordinates of the E wave and the peak coordinates of the A wave are detected using these methods. The processing of step ST3, that is, the processing of detecting the peak waveform from the race waveform and detecting the peak coordinates of the E wave and the peak coordinates of the A wave is performed by the peak waveform detection unit 22 of the blood flow evaluation unit 20. .

  In step ST4, it is determined whether or not the waveform in the deceleration region of the E wave has a variation due to an influence other than blood flow (that is, an influence of a valve or chordae). A specific method for this determination will be described later. If it is determined in step ST4 that no influence other than the blood flow exists in the waveform of the deceleration region of the E wave, the process proceeds to step ST5.

  In step ST5, a predetermined region of the E-wave deceleration waveform is extracted and used as an evaluation deceleration waveform. Specifically, an intermediate value (Ep / 2) which is smaller than the peak value (Ep) of the E wave by a predetermined ratio, for example, a half value of the peak value of the E wave, is obtained. A deceleration waveform between the intermediate values (Ep / 2) is extracted and used as an evaluation deceleration waveform.

  In step ST7, an approximate straight line of the evaluation deceleration waveform is obtained based on the evaluation deceleration waveform data obtained in step ST5 (data between the peak value (Ep) and the intermediate value (Ep / 2)). This approximate straight line is obtained by a method such as a least square method. Further, the time at which the approximate straight line crosses zero is obtained, and the difference between the time of the zero cross and the peak time of the E wave is calculated as the deceleration time DCT of the E wave. The processing of step ST4 and step ST5 described above is performed by the evaluation waveform generation unit 23, and the processing of step ST7 is performed by the deceleration time calculation unit 24.

  The explanatory diagram shown in the central part of FIG. 5 shows that the processing of step ST5 and step ST7 described above is performed on the waveform when there is no influence of the valve or chordae and the deceleration time DCT of the E wave is obtained satisfactorily. ing.

  On the other hand, in the explanatory diagram shown on the right side of FIG. 5, if the processing of step ST5 and step ST7 described above is directly performed on a waveform having an influence of a valve or chordae, a large error occurs in the deceleration time DCT. It is shown that. In this case, there is an unnecessary peak waveform due to the influence of the valve and chordae between the peak value (Ep) and the intermediate value (Ep / 2) of the E wave, and the data used for the least squares method includes This unnecessary peak waveform data is included. For this reason, the obtained approximate line is affected by the valve and chords, and the deceleration time DCT calculated from the approximate line has a large error.

  Therefore, in the ultrasonic diagnostic apparatus 1 according to the present embodiment, a method for eliminating the influence of a valve or a chord has been realized by two methods. The first exclusion method is an exclusion method that uses a parametric system identification model, and the second exclusion method is an exclusion method that uses minimum value detection.

  There are several types of parametric system identification models. In the following description, an ARX model in the parametric system identification model will be described as an example.

(3) First Exclusion Method FIG. 6 is a diagram showing a concept of a first exclusion method that eliminates the influence of valves and chordae using the ARX model.

  In this method, it is determined whether or not it is affected by a valve or chordae by the determination process based on the ARX model, and if affected, the affected area is specified (step ST4). Then, the affected area is removed from the E-wave deceleration waveform, and the removed area is further linearly interpolated or replaced with an estimated trace waveform based on the ARX model to generate an evaluation deceleration waveform (step ST6). ). Note that the evaluation waveform generation unit 23 also performs the processing of step ST4 and step ST6 in the first exclusion method. More detailed processing of step ST4 and step ST6 according to the first exclusion method will be described below.

  In the first exclusion method, as shown in FIG. 7, a plurality of electrocardiogram waveforms (ECG waveforms) u (t) and a plurality that are not affected by other than blood flow (that is, the effects of valves and chordae) The measured trace waveform Yi (t) is previously collected in synchronization with the electrocardiographic waveform u (t). The trace waveform Yi (t) that is not affected by other than blood flow can be collected by measuring blood flow at a heart site where no valve or chordal cord is present, for example. Alternatively, it can be obtained by manually removing the affected part from a trace waveform affected by a valve or chordae by an experienced doctor or engineer.

  Based on these collected trace waveforms Yi (t) and electrocardiogram waveform u (t), system identification is performed using an ARX model.

Here, the ARX model is expressed by the following (Expression 1) to (Expression 3).
[Equation 1]
A (q) * Yi (t) = B (q) * u (t-nk) + e (t) (Formula 1)
A (q) = 1 + a ₁ q ^-1 + ... a _na q ^-na (Formula 2)
B (q) = b ₁ + b ₂ q ⁻¹ +... B _nb q ^{-nb + 1} (Formula 3)

In (Expression 1) to (Expression 3), e (t) is a residual, that is, a difference between an expected value and an actual measurement value, A (q) and B (q) are irreducible polynomials of the shift operator q, nk Is a time delay with respect to the trace waveform Yi (t) which is not affected by blood flow corresponding to the electrocardiogram waveform u (t), and na and nb are integer arguments. Further, in (Expression 2) and (Expression 3), [Equation 2]
a _i = (a ₁ , a ₂ ,... a _na ) (Formula 4)
b _j = (b ₁ , b ₂ ,... b _nb ) (Formula 5)
Is an ARX model parameter when there is no influence other than blood flow.

  It is shown in (Formula 4) and (Formula 5) by the trace waveform Yi (t) which is not affected by the collected blood flow other than the blood flow, that is, the ideal trace waveform Yi (t) and the electrocardiogram waveform u (t). ARX model parameters are obtained in advance. Then, the ARX model parameters obtained in advance are stored in the parameter storage unit 25 of the blood flow evaluation unit 20.

FIG. 8 is a diagram for explaining the concept of determination in step ST4. In the determination in step ST4, the measured trace waveform of the patient obtained in real time (denoted as Yp (t)) is compared with the estimated trace waveform estimated by the ARX model (denoted as Ye (t)). To do. The estimated trace waveform Ye (t) includes an actual measured trace waveform Yp (t) of the patient obtained in real time, an measured electrocardiographic waveform u (t) obtained at the same time, and an ARX model stored in the parameter storage unit 25. From the parameters, it is obtained by the following (formula 6).
[Equation 3]
Ye (t) = − Σ { _ai * Yp (ti)} + Σ {b _j * u (tj)} (Formula 6)
The ARX model parameters used in (Equation 6) are determined by the trace waveform Yi (t) collected in an ideal state unaffected by valves and chordae, and are obtained by (Equation 6). The estimated trace waveform Ye (t) obtained is also a waveform estimated as a result of removing the influence of the valve and the chord from the measured trace waveform Yp (t).

  Therefore, the difference between the estimated trace waveform Ye (t) and the actually measured trace waveform Yp (t) is taken, and the absolute value ABS (Ye (t) −Yp (t)) of the difference is compared with a predetermined threshold value. It is possible to determine the influence of valves and chords on the trace waveform Yp (t). That is, when ABS (Ye (t) -Yp (t)) is smaller than the threshold, it is determined that the valve or chordae are not affected, and ABS (Ye (t) -Yp (t)) is smaller than the threshold. In this case, it is determined that the period is affected by the valve or chordae. The above is the process of step ST4 when the first exclusion method is used.

  Next, in step ST6, a deceleration waveform for evaluation is generated in which the influence of valves and chordae is excluded. FIG. 9 is a diagram showing the concept of the process in step ST6.

  Since the period under the influence of the valve and chordae has already been obtained in step ST4, the waveform of this period is removed from the measured trace waveform Yp (t) (center diagram in FIG. 9). Then, the waveform of the removed period is interpolated with a straight line to generate a deceleration waveform for evaluation (upper right figure in FIG. 9).

  Alternatively, an evaluation deceleration waveform may be generated by replacing the removed period with the estimated trace waveform Ye (t) of the corresponding period (the lower right diagram in FIG. 9).

  After generating the deceleration waveform for evaluation in which the influence of the valve and chordae is eliminated in this way, an approximate straight line of the deceleration period is generated by the same method as described above to calculate the deceleration time DCT (step ST7).

  In the above description, the ARX model has been described as an example. However, the present invention is not limited to this model, and a method using a parametric system identification model other than the ARX model may be used.

(4) Second Exclusion Method FIG. 10 is a diagram showing the concept of a second exclusion method that eliminates the influence of valves and chords using local minimum detection.

  When the second exclusion method is used, in the process of step ST4, the peak value Ep2 of the E wave and an intermediate value smaller than the peak value Ep2 by a predetermined ratio (for example, Ep2 / 2 which is half of the peak value Ep2) It is determined whether or not there is a local minimum value. If there is no minimum value between the peak value Ep2 and the intermediate value Ep2 / 2, it is determined that there is no influence other than the blood flow (the influence of the valve or chordae), and the process proceeds to step ST5.

  On the other hand, if there is a minimum value between the peak value Ep2 and the intermediate value Ep2 / 2, it is determined that the valve or chordae are affected, and the process proceeds to step ST6.

  The determination method of the existence of the local minimum value is not particularly limited. For example, as shown in FIG. 11, a secondary differential waveform of the trace waveform is obtained, and whether the secondary differential waveform exceeds a predetermined threshold in the determination target period. It can be determined by whether or not.

  In step ST6, as shown in FIG. 10, only the waveform between the peak value Ep2 and the minimum value is extracted from the measured trace waveform. The waveform during this period is a waveform that is not affected by the valve or chord, and this is a deceleration waveform for evaluation. It should be noted that the processing of step ST4 and step ST6 in the second exclusion method is also performed by the evaluation waveform generation unit 23.

  In step ST7, an approximate straight line is obtained by the least square method for the deceleration waveform for evaluation (the waveform between the peak value Ep2 and the minimum value), and the deceleration time DCT of the E wave is calculated from this approximate straight line.

  As described above, in any of the first exclusion method and the second exclusion method, it is determined whether or not there is an influence other than blood flow (an influence of a valve or a chordae) on the waveform of the deceleration period of the E wave. If there is an influence, a deceleration waveform for evaluation in which this is eliminated can be generated.

(5) Simplified least square method In step ST7, an operation is performed to obtain an approximate straight line from the generated deceleration waveform for evaluation using the least square method. In this embodiment, the normal least square method is simplified to reduce the number of operations. A method for obtaining an approximate straight line by quantity is adopted.

  FIG. 12 shows a method for obtaining an approximate line by a conventional method of least squares (the left figure of FIG. 12) and a method for obtaining an approximate line by a simplified least square method used in this embodiment (FIG. 12). 12 is a diagram showing the right diagram of FIG.

  As described above, when the approximate straight line is obtained from the deceleration waveform for evaluation, the least square method is applied to data from the peak value Ep of the E wave to the intermediate value Ep / 2 of the deceleration period.

In the conventional method, as shown in the left diagram of FIG.
[Equation 4]
y = a1 * x + a0 (Formula 7)
It is said. In this case, there are two unknowns to be obtained, that is, the coefficient a1 of the primary term and the constant term a0, and it is necessary to solve the following simultaneous equations.
[Equation 5]
a1 * (Σx _i ) + a0 * N = Σy _i (Formula 8)
a1 * (Σx _i ² ) + a0 * Σx _i = Σy _i * x _i (Equation 9)
Here, x _i, y _i (i = 1 to N) is data from the peak value Ep to the intermediate value Ep / 2.

In contrast, in the present embodiment, as shown in the right diagram of FIG. 12, first, the evaluation deceleration waveform is translated so that the peak position of the E wave becomes the origin (0, 0). The approximate expression obtained as a result (origin passing approximate straight line) is
[Equation 6]
y = a1 * x (Formula 10)
Thus, the unknown is only the coefficient a1 of the first-order term. The coefficient a1 can be easily obtained from the following scalar expression, and the number of product-sum operations is greatly reduced as compared with the conventional method.

[Equation 7]
a1 = (Σy _i * x _i ) / (Σx _i ² ) (Formula 11)
Here, x _i, y _i (i = 1 to N) in (Equation 11) is data from the peak value Ep to the intermediate value Ep / 2 after the evaluation deceleration waveform is translated. If the obtained origin passing approximate straight line is translated in the opposite direction, the same approximate curve as the conventional method can be obtained. In this embodiment, the parallel movement is performed twice. However, the increase in calculation load due to the parallel movement is slight, and the effect of reducing the calculation load by reducing the sum of products is much larger than that. .

  As described above, according to the ultrasonic diagnostic apparatus 1 and the diagnostic parameter automatic measurement method according to the present embodiment, even when the influence of a valve or chordae is mixed in the Doppler spectrum from the bloodstream. , E-wave deceleration time DCT can be automatically measured with high reliability.

  Note that the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, the constituent elements over different embodiments may be appropriately combined.

1 is a block diagram showing a configuration example of an ultrasonic diagnostic apparatus according to an embodiment of the present invention. The figure which shows an example of the measuring object of an ultrasonic diagnosing device. The figure which shows an example of the trace waveform of the left ventricular inflow blood flow. The flowchart which shows an example of the automatic measurement process of deceleration time DCT of E wave. The figure which compares the trace waveform which is not influenced by the valve and chordae and the trace waveform which is affected. The conceptual explanatory drawing of the 1st exclusion method which excludes the influence of a valve and a chord from a trace waveform. The conceptual explanatory drawing of the method of calculating | requiring an ARX model parameter. The conceptual explanatory drawing of the method of determining the period which has received the influence of a valve and a chord using the ARX model parameter. The conceptual explanatory view of the generation method of the deceleration waveform for evaluation in the 1st exclusion method. The conceptual explanatory drawing of the 2nd exclusion method which excludes the influence of a valve and a chord from a trace waveform. The conceptual explanatory drawing of the method of calculating | requiring the minimum value in a 2nd exclusion method. The conceptual explanatory drawing of the simplified least square method which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ultrasonic diagnostic apparatus 2 Ultrasonic probe 8 Doppler processing part 21 Trace waveform generation part 22 Peak waveform detection part 23 Evaluation waveform generation part 24 Deceleration time calculation part 25 Parameter storage part 26 Electrocardiogram waveform input part

Claims (18)

A Doppler processing unit that generates a Doppler spectrum from an ultrasonic signal reflected from a predetermined site in the heart;
A trace waveform generator for generating a temporal change of a predetermined spectrum component in the Doppler spectrum as a trace waveform;
A peak waveform detector that detects a predetermined peak waveform from the generated trace waveform;
If it is determined that the waveform of the deceleration region of the peak waveform has a variation due to an effect other than blood flow, this variation is removed to generate a deceleration waveform for evaluation. Otherwise, the detected deceleration of the peak waveform An evaluation waveform generator that uses the waveform of the region as the evaluation deceleration waveform; and
A deceleration time calculation unit for calculating a deceleration time of the predetermined peak waveform from the evaluation deceleration waveform;
An ultrasonic diagnostic apparatus comprising: The predetermined peak waveform is a waveform of an E wave during diastole, and the deceleration time is an E wave deceleration time DCT.
The ultrasonic diagnostic apparatus according to claim 1. An ECG waveform input unit for inputting an ECG waveform;
While acquiring a plurality of electrocardiogram waveforms, a peak waveform not affected by other than blood flow is acquired in synchronization with each electrocardiogram waveform, and the acquired plurality of electrocardiogram waveforms and the plurality of genuine blood flow peaks A parameter storage unit for preliminarily obtaining and storing parameters of the parametric system identification model from the waveform;
Further comprising
The evaluation waveform generator is
Generate an estimated peak waveform in real time from the electrocardiogram waveform input in real time and the parameters of the parametric system identification model stored in the parameter storage unit,
If the amplitude difference between the peak waveform obtained in real time and the estimated peak waveform exceeds a predetermined threshold, it is determined that there is a variation due to an influence other than the blood flow,
Generating the evaluation deceleration waveform by removing the waveform of the period exceeding the threshold from the peak waveform;
The ultrasonic diagnostic apparatus according to claim 1. The evaluation waveform generator is
The waveform of the period removed from the peak waveform is interpolated by the peak waveform remaining after the removal, and the deceleration waveform for evaluation is generated.
The ultrasonic diagnostic apparatus according to claim 3. The evaluation waveform generator is
Replacing the waveform of the period removed from the peak waveform with the estimated peak waveform of the corresponding period to generate the deceleration waveform for evaluation;
The ultrasonic diagnostic apparatus according to claim 3. The evaluation waveform generator is
It is determined whether or not there is a minimum value between the peak value of the extracted peak waveform and an intermediate value that is smaller than the peak value by a predetermined ratio,
When there is the minimum value, it is determined that there is a variation due to an influence other than the blood flow,
A waveform in a range from the peak value to the minimum value of the peak waveform is generated as the evaluation deceleration waveform.
The ultrasonic diagnostic apparatus according to claim 1. The deceleration time calculation unit
An approximate straight line that approximates a waveform between the peak value of the deceleration waveform for evaluation and an intermediate value that is smaller than the peak value by a predetermined ratio is obtained, and the time at which the approximate straight line crosses zero and the peak of the deceleration waveform for evaluation Calculating the deceleration time from the difference from the time corresponding to the value,
The ultrasonic diagnostic apparatus according to claim 1. The deceleration time calculation unit
Obtaining the approximate line by a least square method based on waveform data between the peak value and the intermediate value;
The ultrasonic diagnostic apparatus according to claim 7. The deceleration time calculation unit
The evaluation deceleration waveform is translated so that the peak coordinate of the evaluation deceleration waveform is the origin of time zero and amplitude zero, and the minimum based on the waveform data between the peak value and the intermediate value after the movement By the square method, an origin passing approximate straight line consisting only of the first order term is obtained, and the obtained origin passing approximate straight line is translated in reverse by the amount previously moved to obtain the approximate straight line, whereby the least square method is obtained. Reduce the amount of computation,
The ultrasonic diagnostic apparatus according to claim 8. Generate a Doppler spectrum from the ultrasound signal reflected from a given site in the heart,
A temporal change of a predetermined spectrum component in the Doppler spectrum is generated as a trace waveform,
A predetermined peak waveform is detected from the generated trace waveform,
If it is determined that the waveform of the deceleration region of the peak waveform has a variation due to an effect other than blood flow, the variation waveform is removed to generate a deceleration waveform for evaluation, otherwise the extracted peak waveform is the Deceleration waveform for evaluation,
Calculating a deceleration time of the predetermined peak waveform from the evaluation deceleration waveform;
A diagnostic parameter automatic measurement method comprising a step. The predetermined peak waveform is a waveform of an E wave during diastole, and the deceleration time is an E wave deceleration time DCT.
The diagnostic parameter automatic measurement method according to claim 10, wherein: Enter the ECG waveform
While acquiring a plurality of electrocardiogram waveforms, acquiring a peak waveform not affected by other than blood flow in synchronization with each electrocardiogram waveform, from the acquired plurality of electrocardiogram waveforms and the plurality of peak waveforms, Pre-determining and storing parameters of the parametric system identification model,
Further comprising steps,
In the step of generating the deceleration waveform for evaluation,
Generate an estimated peak waveform in real time from the electrocardiogram waveform input in real time and the parameters of the parametric system identification model,
If the amplitude difference between the peak waveform obtained in real time and the estimated peak waveform exceeds a predetermined threshold, it is determined that there is a variation due to an influence other than the blood flow,
Generating the evaluation deceleration waveform by removing the waveform of the period exceeding the threshold from the peak waveform;
The diagnostic parameter automatic measurement method according to claim 10, wherein: In the step of generating the deceleration waveform for evaluation,
The waveform of the period removed from the peak waveform is interpolated by the peak waveform remaining after the removal, and the deceleration waveform for evaluation is generated.
The diagnostic parameter automatic measurement method according to claim 12, wherein: In the step of generating the deceleration waveform for evaluation,
Replacing the waveform of the period removed from the peak waveform with the estimated peak waveform of the corresponding period to generate the deceleration waveform for evaluation;
The diagnostic parameter automatic measurement method according to claim 12, wherein: In the step of generating the deceleration waveform for evaluation,
It is determined whether or not there is a minimum value between the peak value of the extracted peak waveform and an intermediate value that is smaller than the peak value by a predetermined ratio,
When there is the minimum value, it is determined that there is a variation due to an influence other than the blood flow,
A waveform in a range from the peak value to the minimum value of the peak waveform is generated as the evaluation deceleration waveform.
The diagnostic parameter automatic measurement method according to claim 10, wherein: In the step of calculating the deceleration time,
An approximate straight line that approximates a waveform between the peak value of the deceleration waveform for evaluation and an intermediate value that is smaller than the peak value by a predetermined ratio is obtained, and the time at which the approximate straight line crosses zero and the peak of the deceleration waveform for evaluation Calculating the deceleration time from the difference from the time corresponding to the value,
The diagnostic parameter automatic measurement method according to claim 10, wherein: In the step of calculating the deceleration time,
Obtaining the approximate line by a least square method based on waveform data between the peak value and the intermediate value;
The diagnostic parameter automatic measurement method according to claim 16, wherein: In the step of calculating the deceleration time,
The evaluation deceleration waveform is translated so that the peak coordinate of the evaluation deceleration waveform is the origin of time zero and amplitude zero, and the minimum based on the waveform data between the peak value and the intermediate value after the movement By the square method, an origin passing approximate straight line consisting only of the first order term is obtained, and the obtained origin passing approximate straight line is translated in reverse by the amount previously moved to obtain the approximate straight line, whereby the least square method is obtained. Reduce the amount of computation,
The diagnostic parameter automatic measurement method according to claim 17, wherein:

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