JP6793077B2 - Ultrasonic diagnostic equipment and waveform processing method - Google Patents

Description

The present invention relates to an ultrasonic diagnostic apparatus and a waveform processing method, and more particularly to processing a trace line generated by tracing a Doppler waveform.

An ultrasonic diagnostic device is a medical device that forms and displays an ultrasonic image by transmitting and receiving ultrasonic waves to a living body. The ultrasonic diagnostic apparatus generally includes a Doppler mode (D mode) as an operation mode or a diagnostic mode. As the Doppler mode, PW mode and CW mode are known.

In Doppler mode, frequency analysis is applied to the Doppler signal components contained in the received signal. The power spectrum is obtained as a result of frequency analysis. The image showing the power spectrum acquired at each time is the Doppler waveform. The horizontal axis of the Doppler waveform is the time axis, and the vertical axis represents the velocity (Doppler shift frequency). In the Doppler waveform, the power of each velocity component is represented by the brightness.

An ultrasonic diagnostic device having an auto trace function is also known. The auto trace function traces the Doppler waveform. For example, a peak at each time in the Doppler waveform or a point that is a predetermined level below the peak is specified as a trace point, and is traced as a curve passing through a plurality of specified trace points. A line is generated. It is possible to obtain the heart rate and the like by analyzing the trace line. The Doppler waveform may be traced manually.

Patent Document 1 discloses an ultrasonic diagnostic apparatus that detects a plurality of peaks from a trace line generated by an auto trace function. Patent Document 1 does not disclose the classification of trace lines in heartbeat units and the use of templates. Patent Document 2 discloses an apparatus that generates a template from a signal obtained by transmitting and receiving electromagnetic waves to a living body and calculates a correlation value between the template and the signal. In the apparatus, a waveform portion within a predetermined period before and after each peak included in the target waveform is cut out, and a template is generated by adding and averaging a plurality of cut out waveform parts. If the template generation method is applied to a bimodal waveform, it may not be possible to generate a correct template.

JP-A-7-241290 JP-A-2010-286268

When analyzing a periodically fluctuating waveform (typically the trace line), each unit waveform (part corresponding to one cycle) or each unit period (period corresponding to one cycle) in the waveform is accurately specified. Need to be separated or separated. In particular, when the unit waveform has two peaks (that is, in a bimodal waveform), it is required to correctly specify each unit waveform or each unit period. The template matching method is known as a method for that purpose. In that method, the quality of the template affects the discrimination accuracy. It is required to generate an appropriate template in relation to the waveform to be analyzed.

An object of the present invention is to make it possible to generate a template suitable for a waveform when analyzing a waveform that fluctuates periodically by using template matching. Alternatively, an object of the present invention is to make it possible to generate a template suitable for a trace line having bimodality (Dopla waveform trace line) when using template matching.

(1) The ultrasonic diagnostic apparatus according to the embodiment is a signal processing means that generates a waveform that fluctuates periodically based on a received signal obtained by transmitting and receiving ultrasonic waves to a subject, and based on the waveform. The generation means including a generation means for generating a template and an analysis means for analyzing the waveform using the template, the generation means includes an identification means for identifying at least one reference time phase by morphological analysis of the waveform. An acquisition means for acquiring a periodic sample by periodic analysis of the waveform, cutting out at least one waveform portion from the waveform based on the at least one reference time phase and the periodic sample, and the said based on the at least one waveform portion. Includes waveform processing means for generating templates.

According to the above configuration, at least one reference time phase (for example, the beginning of a heartbeat period) is identified by morphological analysis of the waveform, and a periodic sample (for example, the time length of a certain heartbeat period) is obtained by periodic analysis of the waveform. .. In morphological analysis, a characteristic morphology in the waveform is searched. For example, a maximum value and a minimum value immediately before the maximum value are specified as two points representing the rising portion. In the periodic analysis, for example, the time length (unit period) of a specific one or a plurality of unit waveforms in the waveform is analyzed as a periodic sample by autocorrelation or other methods. A waveform portion is cut out from the waveform using the reference time phase and periodic samples obtained in this way. For example, a cutout section is set for the waveform, starting from the reference time phase and having a time length corresponding to or shorter than that of the periodic sample, and a portion within the cutout section is cut out. A template is generated based on the cut out part. A template may be generated based on a plurality of cut out parts.

In the above configuration, it is not required to individually identify the reference time phase for all the unit waveforms constituting the waveform, and one or several criteria that are likely to be true from the viewpoint of template generation. It suffices if the time phase is identified. Similarly, in the above configuration, it is not required to individually specify the period for all the unit waveforms in the waveform, and from the viewpoint of template generation, the period for one or several typical unit waveforms is set. It suffices to be specified as a sample period.

According to the above configuration, after the waveform is analyzed from the morphological plane and the periodic plane, the cutout portion for the template is specified based on the analysis result, so that the identification accuracy of the cutout portion can be improved, and by extension, the template. The quality of the template can be improved. In the embodiment, the morphological analysis and the periodic analysis are configured as independent processes, and there is an advantage that one analysis result does not depend on the other analysis result.

In the embodiment, the waveform processing means sets a cutting period for the waveform based on the periodic sample while using the reference time phase as a reference, and the waveform portion from the waveform. Includes a cutting means for cutting out a portion within the cutting period. The cutting period is set based on the periodic sample, and preferably, the cutting period is set as a period equal to or less than the periodic sample.

According to this configuration, a part of the waveform part is used as the basis of the template, not the whole waveform part in the unit waveform. Therefore, it is possible to generate a template in which the characteristic part is dominant. By using such a template, the analysis accuracy can be improved, especially when a bimodal waveform is to be analyzed.

In the embodiment, the identification means includes a maximum value detecting means for detecting a plurality of maximum values included in the waveform, and a immediately preceding minimum value for detecting a plurality of immediately preceding minimum values existing immediately before the plurality of maximum values. One or a plurality of reference time phases are determined by selecting one or a plurality of excellent extremum pairs from the detection means and a plurality of extremum pairs composed of the plurality of immediately preceding minimum values and the plurality of maximum values. Includes specific means to identify.

According to this configuration, the reference time phase is identified by searching for a predetermined rising portion. Since one or a plurality of excellent extremum pairs are selected from a plurality of extremum pairs, it is possible to identify a reference time phase that is likely to be true. For example, the above configuration is effective when two peaks are recognized in the unit waveform and the valley immediately before the previous peak is deeper (lower the lowest level) than the valley immediately before the later peak. Function.

In the embodiment, the specific means is based on an evaluation value calculation unit that calculates an evaluation value indicating the degree of inclination for each extreme value pair and a plurality of evaluation values calculated for the plurality of extreme value pairs. Includes a selection unit that selects one or more extremum pairs. As the evaluation value, a gradient, a difference between extreme values, and the like can be used.

In the embodiment, the acquisition means sequentially sets a time window pair consisting of two time windows having the same window size and a predetermined positional relationship with respect to the waveform while changing the window size. , A means of comparing two parts in the sequentially set time window pair with each other and identifying the periodic sample as the window size at the time the two parts fit together. According to this configuration, it is possible to obtain a periodic sample by a simple method.

In the embodiment, the time window pair is composed of two time windows connected in the time axis direction. When the window size changes, any part of the two time windows may be fixed, but the time window pair works without such fixing. In an embodiment, the waveform is a trace line generated by tracing a Doppler waveform representing Doppler information obtained from a foetation.

(2) The waveform processing method according to the embodiment includes a generation step of generating a template based on the waveform and an analysis step of analyzing the waveform using the template, and the generation step includes the waveform. On the other hand, a step of identifying at least one reference time phase by applying a morphological analysis for identifying an extreme value pair consisting of a maximum value and a minimum value existing immediately before the maximum value, and the at least one reference time phase are used. A step of cutting out at least one waveform portion from the waveform based on the above and generating the template based on the at least one waveform portion is included.

According to the above configuration, the reference time phase is specified by specifying the extreme value pair (a pair consisting of the maximum value and the minimum value immediately before it) included in the waveform, that is, by specifying the rising portion included in the waveform. Is identified. Based on the reference time phase, a part for template generation is cut out from the waveform. As the cutout section, a certain section starting from the reference time phase may be set, a certain period including the reference time phase may be set, or a certain period not including the reference time phase may be set. May be good. In that case, it is desirable to adaptively determine a certain time width by periodic analysis of the waveform. It is also conceivable to set a fixed time width or a fixed time width according to other conditions. The reference time phase is a time phase specified from a characteristic waveform portion.

The above method can be realized as a function of hardware or as a function of software. In the latter case, a program for implementing the waveform processing method is installed in the ultrasonic diagnostic apparatus or information processing apparatus via a portable storage medium or network.

According to the present invention, when analyzing a waveform that fluctuates periodically by using template matching, it is possible to generate a template that matches the waveform. Alternatively, according to the present invention, when analyzing a trace line having bimodality by using template matching, a template suitable for the trace line can be generated.

It is a block diagram of the ultrasonic diagnostic apparatus which concerns on embodiment. It is a figure which shows the trace line generated by the trace of a Doppler waveform. It is a block diagram which shows the structural example of the trace line analysis part. It is a block diagram which shows the configuration example of the template generation part. It is a figure which shows the example of the preprocessing applied to a trace line. It is a figure which shows another example of the preprocessing applied to a trace line. It is a figure which shows the action of the time window pair. It is a figure which shows the calculation method of a periodic sample. It is a figure which shows the identification method of the extremum pair. It is a figure which shows the selection result. It is a figure which shows the template generation method. It is a figure which shows the example of waveform analysis using a template.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of the ultrasonic diagnostic apparatus according to the embodiment as a block diagram. This ultrasonic diagnostic device is installed in a medical institution such as a hospital and forms an ultrasonic image by transmitting and receiving ultrasonic waves to a subject. As ultrasonic images, tomographic images (B-mode images), Doppler waveforms (D-mode images), color flow mapping (CFM) images, and the like are known. PW mode and CW mode are known as Doppler modes. In the following, Doppler information processing will be described on the premise of the PW mode. In this embodiment, Doppler information is acquired from the fetal vein (particularly the venous duct connected to the umbilical cord). Of course, other Doppler information may be processed.

In FIG. 1, the probe 10 is composed of a probe head, a cable, and a connector. The connector is detachably attached to the main body of the ultrasonic diagnostic equipment. The probe head is abutted, for example, on the abdominal surface of a pregnant woman. The probe head has an array vibrator composed of a plurality of vibrating elements arranged one-dimensionally. The array oscillators form an ultrasonic beam that is electron scanned. As the electronic scanning method, an electronic sector scanning method, an electronic linear method, and the like are known. The beam scanning surface S is formed by electron scanning.

When the Doppler mode is executed, ultrasonic waves are transmitted and received to the observation direction M. A sample gate SG is set on the observation direction M. The sample gate SG corresponds to a section for extracting Doppler information. Generally, the observation direction M and the sample gate SG are set by the user while observing the tomographic image. Instead of the 1D array oscillator, a 2D array oscillator may be provided to obtain volume data from the three-dimensional space in the living body.

The transmission / reception circuit 12 is an electronic circuit that functions as a transmission beam former and a reception beam former. At the time of transmission, a plurality of transmission signals are supplied in parallel from the transmission / reception circuit 12 to the array oscillator. This forms a transmitting beam. At the time of reception, the reflected wave from the living body is received by the array oscillator. As a result, a plurality of received signals are output in parallel from the array oscillator to the transmission / reception circuit 12. The transmission / reception circuit 12 includes a plurality of amplifiers, a plurality of A / D converters, a plurality of delay circuits, an addition circuit, and the like. In the transmission / reception circuit 12, a plurality of received signals are phasing-added (delayed addition) to form beam data corresponding to the received beam. Received frame data is composed of a plurality of beam data arranged in the electron scanning direction. Each beam data is composed of a plurality of echo data arranged in the depth direction.

The tomographic image forming unit 14 is an electronic circuit that generates tomographic image data based on received frame data. The electronic circuit includes one or more processors. The tomographic image forming unit 14 includes, for example, a detection circuit, a logarithmic conversion circuit, a frame correlation circuit, a digital scan converter (DSC), and the like. The tomographic image data is sent from the tomographic image forming unit 14 to the display 26 via the display processing unit 18.

The Doppler waveform generation unit 16 operates in the Doppler mode (specifically, the PW mode). The Doppler waveform generator 16 includes an orthogonal detection circuit, a complex FFT calculator, a Doppler waveform generator, and the like. Each of them is an electronic circuit. More specifically, the Doppler waveform generation unit 16 takes out Doppler information (Doppler component) contained in the received signal and performs frequency analysis thereof to generate a power spectrum. Then, a Doppler waveform is generated based on the power spectrum calculated at each time. In the Doppler waveform, the power of each frequency component constituting the power spectrum is expressed by the brightness. Data representing the Doppler waveform is sent to the display 26 via the display processing unit 18. The data is also sent to the Doppler waveform processing unit 20.

The Doppler waveform processing unit 20 is configured as an electronic circuit including one or a plurality of processors. Specifically, the Doppler waveform processing unit 20 includes a trace unit 22 that functions as a trace means and a trace line analysis unit 24 that functions as an analysis means. The trace unit 22 and the trace line analysis unit 24 may be realized as software functions. The functions of the trace unit 22 and the trace line analysis unit 24 may be realized by the CPU and the operation program constituting the control unit 28.

The trace unit 22 executes an auto trace on the Doppler waveform, thereby generating a trace line. Specifically, in the Doppler waveform, the peak at each time is specified, and the peak or a point determined based on the peak is defined as a trace point. A trace line is generated by connecting multiple trace points. Trace lines may be generated by other methods. Trace lines may be generated by manual tracing. The trace line data is sent to the display processing unit 18 and the trace line analysis unit 24.

The Doppler waveform generation unit 16 and the trace unit 22 function as signal processing means. That is, they generate waveforms (trace lines) to be analyzed. The trace line fluctuates cyclically in synchronization with the fetal heartbeat.

The trace line analysis unit 24 executes analysis on the trace line. Specifically, a template is generated from the trace line itself, and the trace line is analyzed using the template. This specifically identifies the individual heart rate period. Then, if necessary, peak detection, calculation using the peak, and the like are executed for each heartbeat period.

The display processing unit 18 is composed of an electronic circuit including one or a plurality of processors. The display processing unit 18 has an image composition function, a color calculation function, and the like. The display 26 is composed of an LCD, an organic EL device, or the like. A tomographic image, a Doppler waveform, a trace line, and the like are displayed on the screen of the display 26.

The control unit 28 functions as a control means for controlling each configuration shown in FIG. 1, and is composed of a CPU and an operation program. An operation panel 30 is connected to the control unit 28. The operation panel 30 has input devices such as a trackball, a switch, and a keyboard.

Hereinafter, the operation or operation of each configuration will be described with reference to the respective drawings after FIG.

FIG. 2 shows the action of the trace unit. Specifically, the trace line 33 generated by the auto-trace process on the Doppler waveform 32 is shown. In FIG. 2, the horizontal axis represents the time axis, and the vertical axis represents the velocity (Doppler shift frequency). The Doppler waveform 32 fluctuates periodically according to the heartbeat. Along with this, the trace line 33 also changes periodically.

FIG. 3 shows a configuration example of the trace line analysis unit 24. In the illustrated configuration example, the trace line analysis unit 24 includes a buffer memory 34, a template generation unit 35, a matching processing unit 36, and a waveform measurement unit 37. The template generation unit 35 functions as a template generation means, and it generates a template based on the trace line data stored in the buffer memory 34. When generating the template, morphological analysis and periodic analysis for the trace line are executed. In morphological analysis, extremum pairs are searched and evaluated. Time window pairs are used in periodic analysis. These will be described in detail later.

The matching processing unit 36 and the waveform measurement unit 37 function as analysis means. In particular. The matching processing unit 36 repeatedly executes the correlation calculation between the templates while moving the template relative to the trace line, and specifies each heartbeat period on the trace line based on the correlation calculation result or the trace line. Is divided by heartbeat period. Then, the waveform measurement unit 37 executes a process for identifying a peak, a measurement based on the peak, and the like for each heartbeat period on the trace line. In this way, the measured values required for fetal diagnosis are calculated. The measurement result or the calculation result is sent to the display processing unit. The measurement result or the calculation result is displayed on the screen of the display.

FIG. 4 shows a configuration example of the template generation unit 35 shown in FIG. Trace line data 38 is input to the template generation unit 35. If necessary, the trace line data 38 is preprocessed. The preprocessing will be described later. The template generation unit 35 includes a periodic sample acquisition unit 40 that functions as an acquisition means, a reference time phase identification unit 42 that functions as an identification means, and a waveform processing unit that functions as a waveform processing means (setting means, cutting means, and synthesis means). Has 44. The periodic sample acquisition unit 40 and the reference time phase identification unit 42 perform processing in parallel independently of each other. In other words, one does not depend on the other.

The periodic sample acquisition unit 40 is a module that acquires the period included in the trace line as a periodic sample. Specifically, the periodic sample acquisition unit 40 includes a time window pair setting unit 46, an autocorrelation unit 48, and a periodic sample calculation unit 50. As will be described in detail later, the time window pair setting unit 46 repeatedly sets the time window pair with respect to the trace line while changing the window size. A time window pair is composed of two time windows connected in the time axis direction, and their window sizes are always the same. The minimum value of the window size is specified by τ-min. τ-min is determined, for example, based on the maximum heart rate of a healthy foetation. Two waveform parts are cut out from the two set time windows, and the autocorrelation unit 48 applies a correlation calculation (autocorrelation calculation) to them. As a result of repeatedly executing the correlation calculation as the window size increases, a correlation value curve showing the change in the correlation value is generated. As the correlation value, for example, a normalized correlation value can be obtained by dividing SAD (Sum of Absolute Difference) by an addition number.

The periodic sample calculation unit 50 calculates a periodic sample based on the correlation value curve obtained as the window size is increased. In the present embodiment, the cycle sample is a cycle (or an average value of several cycles) for one or more heartbeat periods included in the trace line, not an average value of the cycles of the entire trace line. As will be described later, at this stage, it is not necessary to perform a strict periodic calculation. Numerical information indicating the calculated periodic sample is sent to the waveform processing unit 44. As long as the period information can be obtained, a method other than the autocorrelation method may be used. For example, the basic period may be calculated by frequency analysis of the trace line.

The reference time phase identification unit 42 identifies one or a plurality of reference time phases on the trace line. In the present embodiment, the reference time phase is the time phase in which the starting point of the first rising portion recognized in each heartbeat period exists, and is the beginning of each heartbeat period. It is the time phase in which there is a local minimum that exists just before the first local maximum, which is also called point a. Another time phase may be used as the reference time phase. For example, the time phase in which the first maximum value (also called the S point) exists may be used as the reference time phase.

More specifically, the reference time phase identification unit 42 includes a maximum value detection unit 52 that functions as a maximum value detection means, a immediately preceding minimum value detection unit 54 that functions as a immediately preceding minimum value detecting means, and a gradient calculation unit that functions as an evaluation value calculation means. It has 56 and a selection unit 58 that functions as a selection means. The gradient calculation unit 56 and the selection unit 58 function as specific means as a whole.

The maximum value detection unit 52 detects a maximum value satisfying the maximum value condition on the trace line. Specifically, in the present embodiment, only the maximum value exceeding the first threshold value is detected. The first threshold value is a value obtained by multiplying the maximum value in the trace line by the coefficient α1 (≦ 1.0). Examples of α1 include numerical values such as 0.70, 0.75, and 0.80.

The immediately preceding minimum value detection unit 54 detects a minimum value that satisfies the immediately preceding minimum value condition. Specifically, in the present embodiment, only the minimum value existing immediately before the maximum value and smaller than the second threshold value is detected as the immediately preceding minimum value. The second threshold value is a value obtained by multiplying the maximum value in the trace line by the coefficient α2 (≦ 1.0). Examples of α2 include numerical values such as 0.20, 0.25, and 0.30. When the immediately preceding minimum value is detected, the immediately preceding minimum value and the subsequent maximum value form an extremum pair. The extremum pair defines both ends of the first rising part of the heart rate period. Other features within the heartbeat period may be identified.

The gradient calculation unit 56 is a module that calculates a gradient as an evaluation value for each extreme value pair (that is, a rising portion). In that case, the extreme value pairs to be calculated for the gradient may be narrowed down according to the exclusion condition. Instead of the gradient, the difference on the vertical axis between the immediately preceding minimum value and the maximum value, the straight line distance, the route length, the time difference, and the like may be used as evaluation values. The selection unit 58 has a sorting function for sorting a plurality of calculated gradients (gradient columns) in descending order. From the sorted gradient sequence, a plurality of gradients having a higher constant ratio k1 are extracted. The constant ratio k1 is, for example, 10%, 20%, or 30%. A plurality of extremum pairs (which can be called excellent extremum pairs) corresponding to the plurality of extracted gradients (which can be said to be excellent gradients) are identified. By adopting the selection method in this way, only the extreme value pairs that are likely to be true are narrowed down. Since each extremum pair identifies the reference time phase (the beginning of the heartbeat period), this selection means narrowing down a plurality of influential reference time phases. Information that identifies a plurality of narrowed-down reference time phases is sent to the waveform processing unit 44.

The waveform processing unit 44 sets a plurality of cutout sections for the trace line based on the selected reference time phase and the calculated periodic sample, and cuts out the waveform portion from them. In addition, a trace waveform is generated by synthesizing a plurality of cut out waveform portions. The time length of each cutout section is determined by multiplying the periodic sample by a coefficient k2 (≦ 1.0). For example, the coefficient k2 is selected in the range of 0.2 to 0.8. For example, 0.5 is selected. When focusing on the individual heartbeat periods in the trace line, a characteristic waveform portion is recognized in the first half of the trace line. Therefore, in the present embodiment, the waveform portion substantially corresponding to the first half of the heartbeat period to be cut out is cut out. A modified example in which the size of the cut-out section is determined by the number of fetal weeks and the like, a modified example in which the size of the cut-out section is fixed to a constant value, and the like can be considered. In any case, assuming a trace line, it is desirable to define the cutout section as a section of less than one heartbeat cycle starting from the beginning of the reference time phase. The cut out plurality of corrugated portions basically have a common or similar morphology. The form is a form that appears repeatedly on the trace line. When synthesizing a plurality of waveform parts, processing such as addition averaging is executed. Smoothing processing or the like may be applied to the waveform after synthesis.

Analysis of the trace line is executed using the template generated as described above. The analysis includes the process of dividing the trace line by heart rate period. According to this embodiment, since a high-quality template that reflects the periodic form included in the trace line can be generated, the analysis accuracy of the trace line can be improved.

Next, the generation of the template and the like will be described more specifically with reference to FIGS. 5 to 12.

FIG. 5 shows an example of preprocessing. The preprocessing is a process performed on the trace line 62 before the template is generated, and is performed as needed. FIG. 5 shows the baseline shift 70 as the preprocessing. Specifically, the minimum value 64 is specified in the trace line 62, and the baseline 66 is moved in parallel upward or downward so as to match the minimum value 64. FIG. 5 shows the baseline 68 after the shift. The baseline 68 defines the 0 level on the vertical axis in the processing of the trace line 62. This makes it easy to perform various calculations. It is also possible to perform various calculations without performing such a baseline shift.

Further, at this stage, a part of the trace line 62 may be manually or automatically specified as a processing target, or a part of the trace line 62 (for example, a range indicated by reference numeral 71) may be processed. It may be configured so that it can be specified to be excluded from the target.

FIG. 6 shows another example of pretreatment. In the illustrated example, the trace line 62A occurs on the negative side of the baseline. In such a case, the trace line 62A may be inverted around the baseline as shown by reference numeral 72, and the inverted trace line may be processed.

FIG. 7 shows the action of the time window pair. The upper part (A) shows the state at the start of processing, and the lower part (B) shows the state during processing (during expansion). The same trace line 74 is drawn for both. At the start of processing, the minimum window size τ-min is set. The time window pair includes a first time window W1 and a second time window W2. They are connected in the time axis direction and each have a minimum window size τ-min in the initial state. Line L0 indicates the position of one end of the first time window W1, line L1 indicates the position of the other end of the first time window W1 and the position of one end of the second time window W2, and line L2 indicates the position of one end of the second time window W2. The position of the other end of the window W2 is shown. In the present embodiment, one end position (that is, line L0) of the first time window W1 is fixed. As the window size increases, the position of the other end of the first time window W1 and the position of one end of the second time window W2 (that is, the line L1) move to the right of the paper surface. At the same time, the position of the other end of the second time window W2 (that is, the line L2) moves to the right of the paper surface by twice the amount of movement. For each movement of the time window pair, the line L1 moves by the increment Δτ, and the line L2 moves by 2 × Δτ. In (B), a state in which a waveform portion corresponding to one cycle is included in each of the time windows W1 and W2 is shown. Three lines L0, L1', and L2'that specify the time windows W1 and W2 are represented.

For each window size, a correlation calculation is executed between the waveform portion included in the time window W1 and the waveform portion included in the time window W2. Specifically, as described above, the normalized SAD is calculated as the correlation value. Other correlation values may be calculated. In the state shown in (B), the correlation value becomes the best (in the case of SAD, it becomes the minimum value and approaches 0). Although the line L0 was fixed, other lines may be fixed, or if necessary, the entire time window pair may be moved as long as the connection condition is satisfied. In any case, as the window size changes, a periodic change in the correlation value described below can be obtained.

FIG. 8 shows the change in the correlation value. The horizontal axis represents the window size τ. The vertical axis shows the standardized SAD. The curve 80 represents the change in the correlation value when the window size τ is gradually increased. A plurality of valleys are recognized on the curve 80, and the lowest point (lower peak) of each valley is specified. A periodic sample is calculated by averaging the widths (time lengths) T1, T2, and T3 between adjacent ones at a plurality of lowest points. Periodic samples may be taken as a single width or as twice a single full width at half maximum. For example, a periodic sample may be specified from τ at the time when the minimum value is first reached. A cycle sample showing a cycle other than one cycle (1/2 cycle, etc.) may be acquired. Here, it is sufficient if a period as a guide can be obtained as a period sample. Curve 82 is a curve 80 that has been smoothed. Periodic samples may be calculated based on curve 82. The starting point of the curve 82 corresponds to the minimum window size τ-min.

FIG. 9 shows a method of detecting an extreme value pair. The trace line 84 is configured as a series of a plurality of unit waveforms corresponding to a plurality of heartbeat periods, and each unit waveform has approximately two large peaks (bimodal). There is a deep valley in front of the first mountain, and a relatively shallow valley between the two mountains. A plurality of small peaks can be seen at the bottom of the trace line 84.

Prior to the extremum search, the maximum value 86 is specified in the trace line 84 (in the illustrated example, the maximum value 90a is the maximum value and is specified), and the first threshold value 87 is set based on that. Set. Specifically, the first threshold value 87 is calculated by multiplying the maximum value 86 by a coefficient α1 (for example, 0.75). As a result, the maximum value detection range 88 is defined as the range from the maximum value 86 to the first threshold value 87. Similarly, the second threshold value 100 is determined by multiplying the maximum value 86 by a coefficient α2 (for example, 0.25). As a result, the immediately preceding minimum value detection range 102 is defined as the range from the minimum value (0 corresponding to the baseline fitted to the minimum value 89) to the second threshold value 100.

On the premise of the above, first, the maximum values 90a, 90b, 90c, 90d, 90e, 90f, 90g exceeding the first threshold value 87 are detected on the trace line 84. The maximum value 92 that does not exceed the first threshold value 87 is excluded from the detection target. Normally, the peak of the second mountain (maximum value) is lower than the peak of the first mountain (maximum value), so that the possibility that the peak of the second mountain is excluded from the detection target can be increased. However, as shown in the figure, when the first threshold value is set relatively low or in a disease example, the peak of the second mountain can also be detected as a maximum value satisfying the condition. By setting the threshold value, the fine peaks existing at the bottom of the trace line are excluded from the detection target.

After the maximum value is detected, or in parallel with it, the immediately preceding minimum value detection is executed. Specifically, the minimum value immediately before the maximum value and smaller than the second threshold value 100 is specified as the immediately preceding minimum value 94a, 94b, 94c, 94d. The minimum values 96a, 96b, 96c, 96d are excluded from the detection target because they are equal to or higher than the second threshold value 100. As a result, it is possible to reduce the possibility that the rising portion on the front side of the second mountain will be the detection target. A plurality of extreme value pairs are formed by pairing between the immediately preceding minimum values 94a, 94b, 94c, 94d and the corresponding maximum values 90a, 90b, 90c, 90d, 90e, 90f, 90g. Will be done. Specifically, in the present embodiment, for example, an extremum pair (90a-94a), an extremum pair (90e-94a), an extremum pair (90b-94b), an extremum pair (90f-94b), an extremum value. A pair (90c-94c), an extremum pair (90d-94d), and an extremum pair (90g-94d) are composed. At this stage, in addition to the adjacent extreme value pairs such as the extreme value pair (90a-94a), the non-adjacent extreme value pair such as (90e-94a) can be identified. However, at this stage, by applying an exclusion condition such as the inclusion of another maximum value between the immediately preceding minimum value and the maximum value that became the extreme value pair candidate, the adjacent pairs that are in a non-adjacent relationship are excluded. You may.

Subsequently, the gradients 104a and 104b are calculated for each extreme value pair. The slopes 104a and 104b are the slopes of the lines passing through the immediately preceding minimum value and the maximum value forming the extreme value pair. After multiple gradients have been calculated, they are sorted in descending order. That is, it is sorted. A plurality of excellent extreme value pairs (or a plurality of excellent immediately preceding local minimum values) included in the high-order k2 (for example, 20%) after rearrangement are specified. The reason for selecting only the top predetermined numbers is to identify only those that are likely to be true. Normally, the slope of the first rise is steeper than the slope of the second rise, so according to the above selection, the possibility that the one corresponding to the second rise will be selected is small. it can. From the above, it is possible to specify a plurality of start periods as a plurality of reference time phases. The beginning is not specified for all heart rate periods, only those that are likely to be true will be selected.

FIG. 10 shows some selected gradients (extreme pairs) 110, 112, 114 with respect to the trace line 106. The individual heartbeat periods 116A, 116B, 116C are specified as periods having a time length specified in the periodic sample, starting from each start point (immediately preceding minimum value). They are a guide, that is, they are the basis for the calculation of the cutout section. Actually, the time lengths of the cutout sections 118A, 118B, 118C are determined by multiplying the time lengths of the heartbeat periods 116A, 116B, 116C by the coefficient k2. These cutout sections 118A, 118B, 118C are periods starting from the beginning of the heartbeat periods 116A, 116B, 116C, and roughly correspond to the first half. In the illustrated example, there are approximately two peaks within each period. It is also possible to set the section so that only one mountain is included.

FIG. 11 shows a heartbeat period 122 and a cutout section 124 as a guideline set for the trace line 120. As shown by reference numeral 126, the waveform portion 128a is cut out from the cutout section 124. A plurality of waveform portions 128b and 128c are cut out from a plurality of other cutout sections. The template 130 is generated by adding and averaging the waveform portions 128a, 128b, and 128c. Template 130 is a standard waveform recognized in a plurality of cutout sections, and reflects a characteristic morphology that repeatedly appears on the trace line. A smoothing process may be applied to the composited template.

FIG. 12 shows the trace line analysis process. Specifically, the trace line 132 is shown in the upper part of FIG. 12, and the curve 134 showing the change in the correlation value is shown in the lower part of FIG. A curve 134 is drawn by performing a correlation calculation between the trace line 132 and the template 135 at each movement position while moving the template 135 generated as described above in the time axis direction. By the way, in the illustrated example, the correlation value is plotted at the position corresponding to the beginning of the template that is sequentially set.

Curve 134 includes several steep valleys 136. The lowest point (lower peak) of each valley 136 corresponds to the best correlation value. Each of the plurality of lower peaks separates the heartbeat period, and the trace line 132 is divided by the heartbeat period. Lines t1-t9 indicate the beginning or break of the heartbeat period, respectively. In addition, it may be configured so that the division of each heartbeat period can be manually corrected.

After each heart rate period is individually identified, measurements are made on the trace line as needed. For example, the time length T4 is measured for a particular heart rate period. Alternatively, the time length is measured for each heart rate period. From those measurement results, the instantaneous heart rate or the average heart rate is calculated. If necessary, the first peak point is detected as the S point, the second peak point is detected as the D point, and the a point is detected as the subsequent minimum value in a specific heartbeat period or all heartbeat periods. To. The point S detected in a certain heartbeat period and the point a detected in the previous heartbeat period are bearing targets. Of course, the maximum value and the immediately preceding minimum value that have already been specified may be used. Other measurements may be calculated based on those points.

According to the above embodiment, when analyzing a waveform that fluctuates periodically by using template matching, it is possible to generate a template that matches the waveform. In particular, when analyzing a trace line having bimodality, a template suitable for the trace line can be generated. The above-mentioned extremum pair search method and cycle acquisition method can be adopted independently, and each can be used in combination with other techniques.

Each of the processes described above is merely an example, and can be appropriately modified according to the actual device configuration. In the above embodiment, when it is desired to apply the matching process using the template to the end of the trace line, for example, the size of the template in the time axis direction may be reduced. Alternatively, the trace line may be apparently extended. Waveforms other than the trace line may be analyzed. For example, another waveform that changes periodically on the time axis or a waveform that changes periodically on the space axis may be analyzed.

20 Doppler waveform processing unit, 22 trace unit, 24 trace line analysis unit, 35 template generation unit, 36 matching processing unit, 37 waveform measurement unit, 40 cycle sample acquisition unit, 42 reference time phase identification unit, 44 waveform processing unit.

Claims (8)

A signal processing means that generates a waveform that fluctuates periodically based on the received signal obtained by transmitting and receiving ultrasonic waves to the subject.
A generation means for generating a template based on the waveform and
And means for analyzing the waveform by using a template matching method, correlation calculation obtained by repeatedly performing a correlation operation between the said waveform while moving the template in the time axis direction Template An analysis means that divides the waveform into heartbeat period units based on the results ,
Including
The generation means
An identification means for identifying at least one reference time phase by morphological analysis of the waveform,
An acquisition means for acquiring a periodic sample by periodic analysis of the waveform, and
A waveform processing means for cutting out at least one waveform portion from the waveform based on the at least one reference time phase and the periodic sample and generating the template based on the at least one waveform portion.
An ultrasonic diagnostic apparatus characterized by including. In the apparatus according to claim 1,
The waveform processing means
With respect to the waveform, a setting means for setting a cutting period based on the periodic sample while using the reference time phase as a reference, and
A cutting means for cutting out a portion within the cutting period as the waveform portion from the waveform.
An ultrasonic diagnostic apparatus characterized by including. In the apparatus according to claim 1,
The identification means
A maximum value detecting means for detecting a plurality of maximum values included in the waveform, and
Immediately preceding local minimum value detecting means for detecting a plurality of immediately preceding local minimum values existing immediately before the plurality of maximum values, and
A specific means for identifying one or a plurality of reference time phases by selecting one or a plurality of excellent extremum pairs from a plurality of extremum pairs composed of the plurality of immediately preceding minimum values and the plurality of maximum values. When,
An ultrasonic diagnostic apparatus characterized by including. In the apparatus according to claim 3,
The specific means
An evaluation value calculation unit that calculates an evaluation value indicating the degree of inclination for each extreme value pair,
A selection unit that selects the one or a plurality of excellent extremum pairs based on a plurality of evaluation values calculated for the plurality of extremum pairs.
An ultrasonic diagnostic apparatus characterized by including. In the apparatus according to claim 1,
The acquisition means
A means for sequentially setting a time window pair consisting of two time windows having the same window size and a predetermined positional relationship with respect to the waveform while changing the window size.
A means for comparing two parts in the sequentially set time window pair with each other and specifying the periodic sample as the window size at the time when the two parts are matched.
An ultrasonic diagnostic apparatus characterized by including. In the apparatus according to claim 5,
The time window pair is composed of two time windows connected in the time axis direction.
An ultrasonic diagnostic device characterized by this. In the apparatus according to claim 1,
The waveform is a trace line generated by tracing the Doppler waveform representing Doppler information obtained from the foetation.
An ultrasonic diagnostic device characterized by this. In a method of processing a waveform obtained by transmitting and receiving ultrasonic waves to a subject,
A generation step of generating a template based on the waveform and
A step of analyzing the waveform by using a template matching method, correlation calculation obtained by repeatedly performing a correlation operation between the said waveform while moving the template in the time axis direction Template An analysis process that divides the waveform into heartbeat period units based on the results ,
Including
The production step is
Identifying to the waveform, and applies the morphological analysis to identify a plurality of extreme value pair consisting of a plurality of local minimum values present just before the plurality of maximum values and its these, thereby a plurality of reference time phase Process and
A step of cutting out a plurality of waveform portions from the waveform based on the plurality of reference time phases and generating the template by synthesizing the plurality of waveform portions.
A waveform processing method comprising.