JP2001137240A - Apparatus and method for measuring ultrasonic wave - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide new measuring and diagnostic techniques using ultrasonic waves. SOLUTION: An ultrasonic pulse beam is transmitted from a probe 10 and its echo is detected. An RF received signal obtained through simple conversion of the echo into an electric signal, or a brightness signal obtained through envelope detection of the RF signal, or a Doppler signal obtained through orthogonal detection of the RF signal, is embedded into an m-dimensional phase space by an attractor constructing portion 42 to construct an attractor. A feature value such as a correlation degree is extracted by a feature extracting portion 44 from the attractor and displayed on a display device 36, together with a conventional diagnostic image such as a B-mode image. The use of a gate such as a brightness signal gate 20 or an RF signal gate 30 enables a signal of a desired depth to be taken out of one beam signal and put to chaos analysis. Hence, a specific part can be selected from within a wide range and put to the chaos analysis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring a state inside a living body or another object to be measured by using ultrasonic waves.

[0002]

2. Description of the Related Art An ultrasonic diagnostic apparatus used in the medical field transmits an ultrasonic beam into a living body, detects an echo from the living body, and forms an image of the echo. 2. Description of the Related Art Devices for displaying a tomographic image in real time by an electronic scanning method or the like are widely used, and are exerting great power for noninvasive diagnosis of a body.

[0003] Widely used ultrasonic diagnostic apparatuses include B
There are two types, one is to image the intensity of the echo by brightness modulation and the like like mode and M mode, and the other is to image the Doppler shift component of the echo due to the movement of the reflector like color Doppler. A device having both functions is also often used.

[0004] Ultrasound diagnostic apparatuses are making progress in various aspects, such as improving the quality of real-time images, calculating blood flow from the images, and developing other application software.

[0005]

As described above, although the progress of the ultrasonic diagnostic apparatus is continuing, the direction of development has been determined to some extent, and there is also the aspect that it is nearing technical maturity. There is a need for a breakthrough for the development of future ultrasonic diagnostic apparatuses.

Moreover, the structure and movement of the living body are very complicated and delicate, and it is difficult to determine whether such complexity has been sufficiently analyzed as an object of evaluation and diagnosis by a conventional ultrasonic diagnostic apparatus. Has doubts. For example, it is often difficult to judge a change in motion when a slight abnormality occurs in the heart by looking at a real-time image, and it may not be detected even if an attempt is made to evaluate it with a macro measured amount such as blood flow. There is a need for a measurement technique that can accurately analyze such complicated and delicate properties.

The problem has been described above by taking an ultrasonic diagnostic apparatus used in the medical field as an example. However, even when measuring the behavior of a machine using ultrasonic waves, it is very important to solve such a problem. it makes sense.

[0008] The present invention has been made in view of such a viewpoint, and a new measurement / measurement using an ultrasonic wave which has not existed in the past.
An object is to provide a device for analysis.

[0009]

Means for Solving the Problems The inventors of the present invention have performed analysis by applying a chaos analysis method to a received signal when an object to be diagnosed, such as a heart, is diagnosed by an ultrasonic diagnostic apparatus. We discovered that the sequence was chaotic. Then, it was confirmed that the chaotic features of the received signal, for example, attractor, correlation dimension (fractal dimension), Lyapunov exponent, etc., change according to the state change of the diagnosis target. The present invention has been made based on such knowledge, and by performing chaos analysis processing on a received signal obtained by an ultrasonic measurement device, a chaotic characteristic of a diagnosis target is obtained, and this is used for diagnosis. As information.

An ultrasonic measuring apparatus according to the present invention transmits and receives an ultrasonic wave into an object to be measured and receives an ultrasonic wave transmitted through the object to be measured or an ultrasonic wave reflected in the object to be measured. Means, a chaos analysis means for performing a chaos analysis process on a reception signal of the transmission / reception means, and an output means for outputting an analysis result of the chaos analysis means.

The chaos analysis process performed by the chaos analysis means includes, for example, a process of constructing an attractor by embedding a signal in a phase space and a process of obtaining a feature quantity such as a correlation dimension (fractal) and a Lyapunov exponent from the attractor. . The reception signal of the transmission / reception means to be analyzed includes, for example, a high-frequency (RF) reception signal in the case of an ultrasonic diagnostic apparatus. In addition, the concept of the received signal to be analyzed includes a signal obtained by performing signal processing such as envelope detection and quadrature detection on the RF reception signal, and a pixel value of an image generated from the detection result. The result of the chaos analysis processing is output by screen display or another method and provided to the user.

In a preferred embodiment, reference information such as a normal value such as an attractor and its characteristic amount is registered in the present apparatus in advance, and the attractor obtained by actual measurement is compared with the reference information to perform measurement. The target can be determined to be abnormal.

In another preferred embodiment, the chaos analysis processing is sequentially performed with time, for example, at regular time intervals, and a change over time of the analysis result is displayed in a list, or an evaluation showing characteristics of the change over time is performed. A value (for example, a gradient of a change in the correlation dimension) is obtained, and a time-dependent change analysis is performed. According to this aspect, it is possible to analyze, for example, a change in the measured object after applying a load or other influence from the viewpoint of chaos. Note that the analysis result list display includes, for example, a list display of attractors at each time point, a graph representing a change in the value of the correlation dimension at each time point, and the like.

Further, the ultrasonic measuring apparatus according to the present invention comprises: a transmitting / receiving means for transmitting an ultrasonic pulse into an object to be measured and receiving an echo from within the object to be measured; Signal extraction means for extracting a signal corresponding to a preset range from a time series of signals; chaos analysis means for performing chaos analysis processing on signals in the range extracted by the signal extraction means; Output means for outputting the analysis result of the analysis means.

In this configuration, an ultrasonic pulse is transmitted into the object to be measured, and its echo is detected. By using a pulse wave as the transmission wave, a distance resolution can be obtained. That is,
From the speed of sound in the object to be measured (this is known from the material of the object to be measured), the time it takes for the ultrasonic wave to reach the target depth (distance from the transmitting and receiving means) and to reflect and return there Therefore, the received signal can be extracted only before and after the time by the signal extracting means such as the gate circuit. By performing the chaos analysis processing on the extracted signal in the desired depth range, the chaos feature of the diagnostic site in the range can be obtained. As described above, according to this configuration, it is possible to obtain a chaotic feature of a portion in a desired range. It should be noted that the range of the signal extraction may be one point as the smallest case. When the range of signal extraction per pulse is small, signals in that range obtained for each pulse transmission are concatenated and regarded as one time-series signal, and chaos analysis processing can be applied. Thereby, chaos analysis can be performed on a signal having a sufficient length.

According to a preferred aspect of the present invention, there is provided a measurement image display means for generating and displaying a measurement image representing an ultrasonic reflection characteristic of each portion in the object to be measured using the reception signal, Range setting means for receiving the designation of the range to be extracted by the signal extracting means and setting the range in the signal extracting means.

The ultrasonic reflection characteristics include not only the intensity of the reflection (echo intensity) but also the Doppler shift due to the blood flow and the speed of the moving body. In this aspect, since a part to be analyzed can be specified on a measurement image such as a B-mode tomographic image in the ultrasonic diagnostic apparatus, a range to be analyzed can be specified accurately.

By superimposing and displaying the chaos analysis result for the specified range in the corresponding position of the measurement image in this way, it is possible to understand at a glance which site is the analysis result.

The signal extraction means extracts signals for a plurality of ranges, performs chaos analysis on each of them, and superimposes and displays the results on a measurement image. Can be displayed.

In the ultrasonic measuring method according to the present invention, an ultrasonic pulse is transmitted / received to / from an object to be measured by a probe, and an ultrasonic reflection characteristic of each part in the object to be measured is determined from a received signal at this time. Generating and displaying a measurement image to be represented, and receiving a designation of a target range for chaos analysis on the measurement image; and receiving the probe from a received signal for the range including the specified target range to the target range. Extracting a corresponding signal; and performing a chaos analysis process on the extracted signal in the target range.

According to this method, chaos analysis can be performed for a specified range on the measurement image, and the result can be obtained.

The present invention can be applied not only to the medical field, but also to the measurement and diagnosis of general objects to be measured whose inside can be detected by ultrasonic waves.

[0023]

Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

Hereinafter, an embodiment in which the present invention is applied to an ultrasonic diagnostic apparatus used in the medical field will be described. FIG. 1 is a functional block diagram showing a configuration example of the ultrasonic diagnostic apparatus of the present embodiment. In this configuration, the probe 10
Is an apparatus for transmitting and receiving ultrasonic waves to and from a subject, and includes an array of ultrasonic transducers. The transmission beamformer 12 supplies a drive pulse with an appropriate delay amount to each transducer of the probe 10,
The transmitted ultrasonic pulse emitted from the transducer array of the probe 10 is converted into a directional beam. Each transducer of the probe 10 receives an echo from the inside of the subject with respect to the ultrasonic pulse beam and converts the echo into an electrical reception signal.
Each reception signal of each transducer is subjected to phasing and addition by the reception beam former 14, and becomes one reception signal corresponding to the reception beam. The controller 50 is for comprehensively controlling each section of the ultrasonic diagnostic apparatus, and the transmission beamformer 12 and the reception beamformer 14 execute the above processing according to the control from the controller 50. Transmit beamformer 1
2 and the receive beamformer 14 by controlling
A transmission beam and a reception beam are formed, and these beams are two-dimensionally scanned, for example, along a predetermined plane.

The reception signal output from the reception beamformer 14 includes an envelope detector 16, a quadrature detector 18, and an RF
The signal is supplied to the signal gate 30. The envelope detector 16 performs logarithmic compression on the received signal and then performs envelope detection. The output of the envelope detector 16 indicates the intensity of the received echo, and is used as a luminance signal for displaying a B mode, an M mode, or the like. The B / M mode signal processing circuit 26 generates a B mode tomographic image or an M mode image based on the luminance signal,
The image data is written into a DSC (digital scan converter) 34.

The quadrature detector 18 receives the beamformer 1
4 is applied to two mixers, and the phases are mutually equal at the same frequency as the transmission frequency of the probe 10.
° Mix with two different reference frequencies. The quadrature detection output includes information on the Doppler shift of the echo. The color Doppler signal operation processing unit 28 performs a known color Doppler operation such as filtering and autocorrelation operation on the quadrature detection output, and inputs the result to the DSC 34.

The output of the quadrature detector 18 is subjected to spectral Doppler processing to obtain a blood flow spectrum at a specific sample point in addition to the above-described color Doppler operation processing. In this spectral Doppler processing, first, the I and Q outputs of the quadrature detector 18 are passed through sample gates 22a and 22b, respectively.
In the sample gates 22a and 22b, it is set in advance which signal of which beam in one frame of the tomographic image is to be extracted in which depth range. Sample gate 22a, 2
2b extracts only the signal in the set range from the input quadrature detection output. Each sample gate 22
The user can set the gate ranges of the a and 22b from the operation panel 52.
The controller 50 supplies a gate signal to the sample gates 22a and 22b according to the setting, and each sample gate gates the input signal according to the gate signal. The signals extracted by the sample gates 22a and 22b are passed through band-pass filters 24a and 24b, respectively, whereby the components of the reflected signal at a low speed portion such as a blood vessel wall are removed. Spectral Doppler signal processing unit 32
Performs a fast Fourier transform on this filter output, and writes an image of a blood flow power spectrum as a frequency analysis result in the DSC 34.

The DSC 34 reads out the written B-mode image, M-mode image, color Doppler image and power spectrum image in synchronization with the display scanning of the display device 36, performs D / A conversion, and supplies it to the display device 36. . Thereby, a diagnostic image such as a B-mode tomographic image or a color Doppler image is displayed on the display device 36.

The configuration for forming a diagnostic image such as a B-mode image and a color Doppler image described above can be the same as a conventionally known general configuration.

Next, a configuration for chaos analysis which is a feature of the present embodiment will be described. The device of the present embodiment is:
High frequency (RF) output from the reception beam former 14
Has a function of performing a chaos analysis process on the received signal, the luminance signal used for the BM mode image formation, and the Doppler signal used for the spectrum Doppler process. Which signal is subjected to the chaos analysis processing can be switched by the switch 40. Which signal is to be analyzed may be selected, for example, according to the characteristics of the target site / tissue to be analyzed. For example, when it is desired to perform a chaos analysis on a blood flow, a Doppler signal may be selected. Even in the same part,
If the signal to be used is switched, there is a possibility that property information from a different point of view for the site is obtained.

Further, in the present embodiment, a mechanism for extracting only a signal of a desired part from among the signals to be analyzed and performing a chaos analysis is provided. The RF signal gate 30 and the luminance signal gate 20 are mechanisms for that purpose. In the gates 30 and 20, as with the sample gates 22a and 22b for spectral Doppler processing, it is set in advance which signal of which beam and which depth range should be extracted from the signal of one frame of the tomographic image. . Therefore, RF
The signal gate 30 gates the RF reception signal output from the reception beam former 14, and the luminance signal gate 20 gates the luminance signal output from the envelope detector 16, respectively.
Only signals within a preset range are extracted and output to the subsequent stage. The gate ranges of the RF signal gate 30 and the luminance signal gate 20, like the sample gates 22a and 22b, are set in the controller 50 in response to a user input from the operation panel 52, and the controller 50 sets the gate 20 in accordance with this setting. Or 3
Control 0.

As described above, by providing a mechanism for extracting only a signal in a predetermined range and transferring the signal to a subsequent chaos analysis process, a chaotic feature of a desired portion can be obtained. It is to be noted that, even if a chaos analysis is performed on the entire signal for one beam or the entire signal for one frame (screen) without providing such a gate, it is also possible to obtain some chaotic features for the entire range. Of course, it is possible. In addition, by providing a gate to limit the chaos analysis target site as in the present embodiment, the chaos characteristics of the site can be discriminated and analyzed more precisely.

As described above, a gate for extracting a signal in a desired range is provided for an RF reception signal and a luminance signal. However, for a Doppler signal which is another object of chaos analysis, a sample gate for spectral Doppler processing is provided. Since signals in a predetermined range have already been extracted at 22a and 22b, it is not necessary to newly provide a gate means. That is, an ultrasonic diagnostic apparatus often has a spectral Doppler processing function, and with such an ultrasonic diagnostic apparatus, a gate for spectral Doppler processing can also be used as a gate for chaos analysis. . The switch 40 receives only the components that have passed through the band-pass filters 24a and 24b, not the outputs of the sample gates 22a and 22b. This is for performing chaos analysis on the signal component relating to the blood flow of interest. If the passbands of the bandpass filters 24a and 24b are switched to a lower band, chaos analysis can be performed on the movement of the body tissue at a low speed.

As described above, the switch 40 to which the RF reception signal, the luminance signal, and the Doppler signal extracted only from the range of interest by the gate processing are input, and one of the three signals designated by the user as the analysis target is selected. And pass it to the chaos analysis mechanism at the later stage. The specification of the signal to be analyzed is performed from the operation panel 52, and the controller 50 switches the connection of the switch 40 according to the specified content.

The chaos analysis processing mechanism at the subsequent stage of the switch 40 is roughly divided into an attractor construction section 42 and a feature extraction section 4.
4 The attractor construction unit 42 constructs an attractor from the input signal. The attractor can be reconfigured, for example, by embedding the input signal in the phase space using the Takens method. As is well known, the Turkens method uses a time-series signal x
From (t) (where t is time), a set of m variables {x (t), x (t + τ), x (t + 2τ),
.., X (t + (m−1) τ)}, and the attractor is reconstructed by plotting this in an m-dimensional space (phase space). The attractor constructing unit 42 constructs an attractor by embedding an input signal time series in an m-dimensional phase space using, for example, the Turkens method. The attractor constructed in this manner can be said to be a trajectory (trajectory) of the target signal in the phase space.

As a specific signal processing, for example, a process of sequentially storing the values of input signals in a memory and sequentially reading out m pieces of data at intervals of τ from the memory at different times t. There is a way. According to this method, the attractor can be dynamically constructed from the signal data at each time point stored in the memory. This method can be easily implemented as hardware.

Since the Doppler signal is a complex signal (I, Q), when constructing an attractor from this, for example, considering that I and Q are each independent, a 2m-dimensional phase space ｛I
(T), I (t + τ),... I (t + (m−1) τ), Q
(T), Q (t + (m-1) τ)}.
Alternatively, one of I and Q may be selected to draw the attractor.

The time delay τ when using the Turkens method must be appropriately determined in order to obtain a significant trajectory. The time delay τ is preferably determined according to signal characteristics such as a frequency band of a given analysis target signal. For example, when chaos analysis is performed on an RF reception signal, the frequency of the transmission ultrasonic wave greatly affects the signal waveform. Therefore, an appropriate time delay τ may be determined depending on the frequency band of the transmission ultrasonic wave. An appropriate time delay τ for a certain frequency band may be obtained in advance by an experiment or the like and set in the attractor construction unit 42. It is also preferable that the time delay τ can be finely adjusted from the operation panel 52. In the case of an ultrasonic diagnostic apparatus capable of using a plurality of transmission frequencies, an appropriate time delay τ is registered for each frequency band, and the time delay τ is automatically selected in conjunction with the selection of the transmission frequency band. It is also suitable to keep it in this way. When chaos analysis is performed on a luminance signal or a Doppler signal, a method of obtaining a frequency band of the signal and selecting a time delay τ according to the frequency band can be considered. Also in this case, how much time delay is appropriate for a certain frequency band may be determined by an experiment or the like, and the relationship may be registered in the attractor construction unit 42 in advance.

In this embodiment, the gates 20, 22a, 2a
According to 2b or 30, only one signal among a large number of scanning lines for forming a tomographic image, and more specifically, a signal in a specific depth range is extracted as an analysis target, so that the signal is obtained during one frame of the image. There may be a case where an attractor having a length sufficient for the analysis process cannot be obtained only with the signal to be analyzed (having only a length corresponding to the depth range). In such a case, the signal extracted for each frame may be connected over a plurality of frames until an attractor of a sufficient length is obtained, and the attractor may be obtained from the connected signal. In other words, in this method, as shown in FIG. 2, a gate 100 (such as the luminance signal gate 20) obtains a reception signal (or a detection result thereof) for each ultrasonic pulse beam 110 sequentially transmitted in the same direction. Only signals in the same depth range specified in advance are extracted. Then, the attractor constructing unit 42 connects them in chronological order and regards them as one time-series signal 120, and constructs an attractor from this time-series signal 120.

The method of constructing the attractor is not limited to the method of Turns. If the properties of the input signal are good, it is also possible to obtain a first-order, second-order,..., (M-1) -order derivative from the input signal, and to plot the respective differential values as coordinate components in a phase space.

Since the appropriate dimension m of the phase space when constructing the attractor may vary depending on the characteristics of the diagnostic object and the diagnostic apparatus, it is desirable to determine the dimension m in advance through experiments and the like. For example, in an experiment on a human heart, which will be described later, it was confirmed that the correlation dimension (fractal dimension) may be regarded as substantially converging at about m = 10. When analyzing, 1
It can be seen that the attractor should be constructed in the zero-dimensional phase space.

The feature extracting unit 44 obtains the correlation dimension (fractal dimension), Lyapunov exponent, Poincare section, or a return map on the Poincare section of the attractor from the information of the attractor. The features of these attractors need not be all sought,
In some cases, useful information can be obtained. In particular, the correlation dimension and Lyapunov exponent are easy to handle because they are one numerical value. The inventors have confirmed through experiments that the correlation dimension and the Lyapunov exponent change according to changes in the state of the heart. The method of obtaining the above characteristics is described in various documents relating to chaos, and thus description thereof is omitted here. The feature extraction unit 44 can be realized by implementing such a known algorithm, for example, as software.

The feature extracting section 44 has a function of analyzing a temporal change of the above-mentioned various features. For example, after applying an exercise load to the heart, the state of the heart changes momentarily before returning to a normal state.According to experiments performed by the inventors, the change indicates that the change in the chaos, such as the correlation dimension and the Lyapunov exponent, occurs. It turned out to appear in the features. For example, in an exercise load experiment for healthy persons, it has been confirmed that the correlation dimension recovers almost linearly toward the value before exercise. The feature extracting unit 44 calculates a correlation dimension and a Lyapunov exponent at appropriate time intervals, and graphs the time change, or calculates an evaluation value such as a gradient of the change (in the case of a linear change). Although the “slope” of the change has been described as an example of the evaluation value representing the time change, the appropriate evaluation value may vary depending on the characteristics of the diagnosis target or the like. Therefore, it is desirable to perform an experiment for each diagnosis object, obtain a function approximating the change in the chaotic feature, and take measures such as using a parameter specifying the function as an evaluation value. In the feature extraction unit 44, the evaluation value calculation algorithm for each diagnosis target obtained in advance as described above may be registered so that the user can switch and use it as appropriate.

Which one of the above various characteristics is required is
It is also preferable that the user can select from the operation panel 52 or the like.

For the processing of the feature extraction unit 44,
Attractors need not be explicitly required.
That is, the Turkens method described above as an example of an attractor construction method plots m (in the case of m-dimensional) values that differ by a time delay τ from a time series of signal values as a set. If there is time-series information, it can be created dynamically. Therefore, it is also possible to perform a process of calculating the above-mentioned feature value while sequentially reading out a set of m values from the signal value time series in the feature extraction unit 44.

The various chaotic features obtained by the feature extracting section 44 are displayed on the display device 36.

As a display form, for example, there is a method in which a display frame different from a normal tomographic image or the like is provided and displayed therein. This method may be suitable for a Poincare section, a return map, a graph of the time change of the correlation dimension, and the like. Since the correlation dimension and the Lyapunov exponent are obtained as one numerical value, such a numerical value itself can be displayed in a dedicated display area, but it is also preferable to superimpose the numerical value on a tomographic image. That is, in the apparatus of FIG.
Since the range of chaos analysis processing is limited by 0, 22a, 22b or 30, the numerical value of the characteristic is displayed at the position of the range on the tomographic image, or the value of the characteristic is displayed in color or brightness. It is also preferred to do so. It is also preferable that the attractor itself obtained by the attractor constructing unit 42 is displayed on the display device 36 and used for diagnosis.

Next, referring to FIG. 3, an example of a processing procedure by the apparatus of the present embodiment will be described. First, the probe 10 is brought into contact with a diagnostic site to transmit and receive ultrasonic waves,
A conventional ultrasonic image such as a mode and color Doppler is displayed on the display device 36 (S10). When viewed from the purpose of chaos analysis, this ultrasonic image display is used for positioning a chaos analysis target site. Further, the user selects the type of the signal to be analyzed (in the example of FIG. 1, RF, luminance, or Doppler) on the operation panel 52 (S1).
2). In response to this selection, the controller 50 switches the connection of the switch 40 so that a signal of the selected type can be input to the attractor construction unit 42.

Either of steps S10 and S12 may be performed.

Next, the user designates the range of the chaos analysis target (ie, the signal extraction range by the gate) on the ultrasonic image (S14). An example of an operation procedure for specifying the range will be described with reference to FIG. In this example, an ultrasonic image 200 of B mode (or B mode + color Doppler) is displayed on the screen of the display device 36. The user determines the target range 250 of the chaos analysis while looking at the image 200 which changes every moment, and specifies the range on the screen using a pointing device such as a mouse or a trackball attached to the apparatus. The area of interest 250 is typically a range from one depth to a certain depth along one scan line 210 of the ultrasound beam. Therefore,
For example, when the user designates a start point and an end point of the range on the ultrasonic image 200, the controller 50 selects a scan line 210 near the start point and the end point, and on the scan line 210, the designated start point and an end point near the end point. Select a point as the start and end point of the target area. The controller 50 determines that the range from the start point to the end point is 1
Which period of which scanning line in the ultrasonic beam scanning of the frame is obtained, and this is stored as a gate range.

Although the example of the procedure for designating the chaos analysis target range on the tomographic image in the B mode or the like has been described above, the target range can of course be specified on the M mode image. In the case of an ultrasonic diagnostic apparatus capable of simultaneously displaying the B and M modes, since the M mode image is already formed by selecting one existing scanning line, by specifying a depth range on the M mode image, That defines both the scan line and the depth range. Therefore, for example, a scanning line for M-mode display is selected while viewing the B-mode tomographic image,
It is also possible to narrow down the depth range of the chaos analysis target by looking at the mode display.

In the above example, a certain depth range in one scanning line is selected as the analysis target range. However, as in the M mode, the entire one scanning line can be designated as the analysis target range. This is also expected to provide useful diagnostic information.

In step S12, the type of the signal to be analyzed is selected.
When the analysis target range is specified in S14, the controller 50
Are the gates 20 and (22) of the selected signal types.
a, 22b), or 30 starts supplying a gate signal for extracting a signal in a specified range. As a result, of the signals of the selected signal type, portions extracted by the gate are sequentially supplied to the attractor constructing unit 42, and an attractor is constructed (S16). Then, the feature extraction unit 44 obtains chaos feature information such as a correlation dimension and a Poincare section from the attractor, and displays it on the display device 36 (S18).

When analyzing a time change such as a correlation dimension,
Attractors are obtained at appropriate time intervals, and correlation dimensions and the like are obtained from the attractors and stored. Then, when the calculation results such as the correlation dimension for a predetermined time are accumulated,
What is necessary is just to perform evaluation value calculation, such as a graph display and inclination.

The apparatus according to the present embodiment and an example of the processing procedure using the apparatus have been described above. Next, results of experiments performed on the device according to the present embodiment will be exemplified. In this experiment, the state of the left ventricle of the heart after applying a predetermined exercise load to a healthy person was analyzed from a chaotic viewpoint. As an object signal for the chaos analysis, an RF attracting signal of the ultrasonic diagnostic apparatus was used, one attractor was constructed from the received signals for several times transmitted ultrasonic pulses, and a correlation dimension was obtained. The range of signals used for the analysis was the entirety of one scanning line. This process of attractor construction and correlation dimension calculation is performed before exercise load,
The treatment was performed immediately after the exercise load and at each time point every three minutes thereafter.

FIG. 5 is a diagram showing the trajectory (attractor) of the received signal at each time point. For convenience of display, a trajectory in a case where a received signal is embedded in a three-dimensional phase space will be described as an example. According to this figure, the trajectory before exercise is a relatively clean chaos attractor, but the messengers are increasing immediately after exercise, and as time goes on, the trajectory close to the trajectory before exercise gradually returns. You can see it going.

The attractor correlation dimension D ₂ was obtained according to the following equation.

[0058]

(Equation 1) Here, R represents the radius of scaling, and C (R) is the correlation integral shown in the following equation.

[0059]

(Equation 2) Here, σ is a Heavisite function, N _dat is the total number of attractor data points included in the m-dimensional phase space, N _ref
Is the number of data points of a sufficiently large reference signal. x _i, x
_j is a point on the attractor. This calculation formula itself is publicly known, and for details, refer to a book regarding chaos. Note that the calculation method of the correlation dimension is only an example.

In the experiment, the received signal at one time was m = 3 to 1
Eight attractors were constructed by embedding them in the phase space of each dimension of 0, and the correlation dimension was calculated for each of the attractors using the above formula. FIG. 6 is a log-logarithmic graph in which the horizontal axis represents the scaling radius R and the vertical axis represents the correlation integral C (R). For each embedding dimension of m = 3 to 10, (l
ogR, logC (R)).
The limit of the inclination of the graphs 300 and 310 for each dimension m is
A correlation dimension D ₂ of the attractor in the embedding dimension m. A graph 320 is a diagram illustrating a change in the inclination (that is, the correlation dimension) of the graph 300 and the like when the embedding dimension m is increased. As can be seen from this figure, in the received signal relating to the left ventricle, the correlation dimension rapidly converges as the embedding dimension m increases, and it is seen that the correlation dimension is almost constant at about m = 8-10. The final correlation dimension of the received signal (fractal dimension) D ₂ is the convergence value. Based on this result, m = 10 was adopted as the embedding dimension in the chaos analysis of the heart.

FIG. 7 shows an embedding dimension m = 10 at each time point.
Is a graph showing the time variation of the correlation dimension D ₂ of attractors in. According to this graph, except the value at the time immediately after the end of exercise (time 0), correlation dimension D _2, it is seen that substantially linearly restored to the value before the movement.
The slope of this graph is considered to indicate the resilience of the heart after loading, and can be used as one evaluation value for evaluating cardiac function.

FIG. 8 shows an example of the Poincare section obtained in this experiment. The illustrated example is a Poincare section showing a point of the attractor (shown by a black dot in the drawing) on the surface when the attractor is cut at a certain point 12 minutes after the end of the exercise load. Such Poincare sections are also expected to be used for diagnosis. It is also preferable that the Poincare sections on a plurality of different planes are obtained for the attractor at one time and displayed in parallel. In addition, if Poincare sections on the same plane are obtained from the attractors at each point in time and are displayed in parallel, it is expected that the analysis of changes over time can be performed.

FIG. 9 is an example of a return map obtained from a certain Poincare section 12 minutes after the end of the exercise load. If the transition pattern of the attractor trajectory is known from such a return map, it is expected to be useful diagnostic information.

The experimental example has been described above. The apparatus according to the present embodiment includes a change over time of the attractor as shown in FIG.
And a function of obtaining and displaying a temporal change in the correlation dimension or a temporal change in the Poincare section. Further, the apparatus of the present embodiment has a function of obtaining and displaying an evaluation value such as its inclination from the temporal change of the correlation dimension. Such a function of analyzing and displaying changes over time can be applied to other than the exercise load test described above. An example of the application is, for example, diagnosis of a drug effect. That is, the apparatus of the present embodiment periodically obtains a chaotic feature (for example, a correlation dimension) of the target organ / tissue after the drug administration is started, and presents a temporal change of the feature. The diagnostician
From this change, it is possible to judge the degree of the medication effect, and to predict when healing will occur.

It is needless to say that the chaos feature obtained at one point in time is useful for diagnosis as well as such a change over time. The diagnostician will be able to determine the state of the diagnosis target site, the presence or absence of a lesion, and the like from the shape of the attractor and the value of the correlation dimension. In addition, by examining attractors, correlation dimensions, and the like for a large number of healthy individuals and determining their representative values, and registering the representative values in this device as reference information, abnormalities in the actual chaos analysis results of the subject can be obtained. It is also possible to automatically determine whether or not there is, and the degree of abnormality.

The preferred embodiment of the present invention has been described above. As described above, according to the present embodiment, it is possible to obtain new diagnostic information that has not been available in the past using ultrasonic waves. For example, if the analysis is performed on the heart, it is possible to evaluate differences in the properties of the heart as differences in attractors and values of the correlation dimension.

In the above description, the case where the signal portion to be extracted as the object of chaos analysis is one is described as an example.
It is also possible to extract a plurality of ranges on one scanning line or one image frame by a gate, and perform the above-described chaos analysis in parallel for each range. In this case, if the correlation dimensions and the like of each range are superimposed and displayed on a tomographic image or the like (for example, color display), the distribution of chaotic features of each unit can be grasped at a glance.

In the above description, chaos analysis was performed using a received signal for one scanning line of ultrasonic beam scanning for displaying a tomographic image. It is also preferable to control the beam scanning so that the ultrasonic pulse beam is repeatedly transmitted and received only in that direction. According to this, the temporal continuity of the received signal is improved, and a more accurate analysis result can be obtained.

In the above, an example of the case of an ultrasonic diagnostic apparatus of a type in which a two-dimensional tomographic plane is formed by scanning a beam has been described, but the application of the present invention is not limited to this. For example, the present invention is also applicable to an ultrasonic diagnostic apparatus of a type that obtains three-dimensional information by scanning a beam in two directions. Also,
The present invention is naturally applicable to the case where the beam is transmitted and received only in one direction without scanning the beam.

In the above example, the R of the ultrasonic diagnostic apparatus
Although chaos analysis is performed on a signal at a stage closer to the reception side, such as the F reception signal or its detection result, a similar chaos analysis can be performed on a signal closer to the diagnostic image. For example, as shown in FIG. 10, the same pixel (point of interest 41
It is also conceivable to consider the change of the pixel value of 0) over a plurality of frames as a time-series signal and perform the above-described chaos analysis on this time-series signal. In this case, in principle, such an analysis can be performed for each pixel of the tomographic image, so that the value of the chaotic feature such as the correlation dimension can be obtained for each pixel, and the distribution of the value can be expressed in the tomographic image in color, for example. Display such as superimposed display can be performed.

In the above example, a case where a pulse wave is used as an ultrasonic wave for analysis has been described. However, a continuous wave may be used. In the case of a continuous wave, a distance resolution similar to that of a pulse wave cannot be obtained, but it is possible to analyze a chaotic feature of the entire ultrasonic wave propagation path. In the above, the case where the received signal of the echo of the pulse wave is analyzed has been described as an example. However, not only the received signal of the echo (reflected wave) but also the received signal of the transmitted wave transmitted through the subject is analyzed. It is also possible to perform a similar chaos analysis.

In the above example, the result of the chaos analysis is displayed on the display device as an image. However, it is naturally possible to store the result in a storage device for further analysis.

In the above example, the application of the present invention to the ultrasonic diagnostic apparatus in the medical field has been described, but the application of the present invention is not limited to this. If a received signal with a sufficient SN ratio can be obtained, it can be applied to measurement and diagnosis of the internal state of a machine or the like.

[0074]

As described above, according to the present invention,
An unprecedented new method for ultrasonic measurement / diagnosis by transmitting ultrasonic waves into the object to be measured, receiving ultrasonic signals from the object to be measured, and performing chaos analysis was gotten. In particular, by using the echo of the ultrasonic pulse, a distance resolution can be obtained, and it becomes possible to obtain a chaotic feature of a specific portion in the measured object.

[Brief description of the drawings]

FIG. 1 is a functional block diagram illustrating a configuration example of an ultrasonic diagnostic apparatus to which the present invention has been applied.

FIG. 2 is a diagram for explaining generation of a time-series signal of a chaos analysis target using a gate.

FIG. 3 is a diagram showing an example of a processing procedure in the apparatus of FIG.

FIG. 4 is a diagram illustrating an example of an operation of designating an analysis target range.

FIG. 5 is a diagram showing the state of the attractor at each time point obtained from the echo reception signal of the left ventricle in the exercise load test.

FIG. 6 is a diagram for explaining how to obtain a correlation dimension.

FIG. 7 is a diagram showing a change in a correlation dimension over time after an exercise load.

FIG. 8 is a diagram showing an example of a Poincare section.

FIG. 9 is a diagram illustrating an example of a return map.

FIG. 10 is a diagram for describing an example in which a change in the pixel value of a target pixel of a tomographic image is set as a chaos analysis target.

[Explanation of symbols]

Reference Signs List 10 probe, 12 transmission beamformer, 14 reception beamformer, 16 envelope detector, 18 quadrature detector, 20 luminance signal gate, 22a, 22b sample gate, 24a, 24b bandpass filter, 26B
-M mode signal processing circuit, 28 color Doppler signal operation processing unit, 30 RF signal gate, 32 spectrum Doppler signal operation processing unit, 34 DSC, 36 display device, 40
Switcher, 42 attractor construction unit, 44 feature extraction unit.

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[Procedure amendment]

[Submission Date] November 26, 1999 (1999.11.
26)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Harumitsu Harada 6-22-1, Mure, Mitaka City, Tokyo Aloka Inc. (72) Inventor Takashi Ito 6-22-1, Mure, Mitaka City, Tokyo Aloka Stock In-house F term (reference) 4C301 DD02 EE20 JB07 JB28 JB50 KK12 KK27 5J083 AA02 AD13 BA01 BC01 BE18 BE60 EA12 EA14 EA16 EA35

Claims (17)

[Claims] A transmitting / receiving means for transmitting an ultrasonic wave into an object to be measured and receiving an ultrasonic wave transmitted through the object to be measured or an ultrasonic wave reflected in the object to be measured; Chaos analysis means for performing chaos analysis processing on a received signal; output means for outputting an analysis result of the chaos analysis means;
Ultrasonic measurement device having 2. The ultrasonic measuring apparatus according to claim 1, wherein said chaos analyzing means includes an attractor constructing means for constructing an attractor from the received signal. 3. The apparatus according to claim 2, wherein said chaos analyzing means has a feature calculating means for calculating a feature amount representing a chaotic feature of the received signal from the attractor constructed by the attractor constructing means. Ultrasonic measuring device. 4. The apparatus according to claim 1, further comprising: means for comparing an analysis result of the chaos analysis means with a reference analysis result when the measured object is normal, and performing abnormality determination of the measured object based on the comparison. The ultrasonic measuring device according to any one of claims 1 to 3, wherein 5. The apparatus according to claim 1, further comprising: means for displaying a list of analysis results of the chaos analysis means at each time point, which change in accordance with the temporal change of the object to be measured. The ultrasonic measurement device according to any one of the above. 6. An ultrasonic wave according to claim 3, further comprising: means for obtaining a temporal change of a feature amount of said characteristic calculating means, and calculating an evaluation value of said measured object from said temporal change. Measuring device. 7. A transmitting and receiving means for transmitting an ultrasonic pulse into an object to be measured and receiving an echo from within the object to be measured, and a preset time-series from a time series of a signal received by the transmitting and receiving means. Signal extraction means for extracting a signal corresponding to the extracted range, chaos analysis means for performing chaos analysis processing on the signal in the range extracted by the signal extraction means, and output means for outputting an analysis result of the chaos analysis means An ultrasonic measurement device comprising: 8. A measurement image display unit that generates and displays a measurement image representing an ultrasonic reflection characteristic of each part in the object to be measured using the reception signal, and a measurement image display unit that associates the measurement image with the measurement image. The ultrasonic measurement apparatus according to claim 7, further comprising: a range setting unit that receives designation of a range to be extracted and sets the range in the signal extraction unit. 9. The transmission / reception unit scans the inside of the object to be measured with a beam of an ultrasonic pulse, and the range setting unit determines which scan line in the beam scan has the range specified on the measurement image. 9. The ultrasonic measuring apparatus according to claim 8, wherein a depth range corresponding to the depth range is determined and set in the signal extracting unit. 10. The ultrasonic measurement apparatus according to claim 8, wherein said output means superimposes and displays the analysis result of said chaos analysis means at a position corresponding to the range of said extraction target on said measurement image. . 11. A signal extracting means for extracting signals in a plurality of ranges, performing a chaos analysis process on each of the extracted signals, and superimposing and displaying an analysis result of each range on a corresponding position on the measurement image. The ultrasonic measuring device according to claim 8, wherein 12. The apparatus according to claim 1, wherein the chaos analyzing means concatenates the signals sequentially extracted by the signal extracting means to obtain a series of time-series signals, and performs chaos analysis processing on the time-series signals. The ultrasonic measuring device according to any one of claims 7 to 11. 13. The apparatus according to claim 7, wherein said chaos analyzing means includes an attractor constructing means for constructing an attractor from a time-series signal obtained by connecting the signals extracted by said signal extracting means. The ultrasonic measuring device according to any one of the above. 14. The apparatus according to claim 13, wherein said chaos analyzing means has a characteristic calculating means for calculating a characteristic amount representing a chaotic characteristic of the received signal from the attractor constructed by the attractor constructing means. Ultrasonic measuring device. 15. A step of transmitting and receiving an ultrasonic pulse to and from an object to be measured by a probe, and generating and displaying a measurement image representing an ultrasonic reflection characteristic of each part in the object to be measured from a received signal at this time. Receiving a designation of a target range for chaos analysis on the measurement image; and extracting a signal corresponding to the target range from a received signal of the probe for a range including the specified target range; Performing a chaos analysis process on the signal of the target range thus obtained. 16. The ultrasonic wave according to claim 15, wherein the step of performing the chaos analysis processing includes a step of obtaining at least one of an attractor, a correlation dimension, and a Lyapunov exponent from the signal of the target range. Measurement method. 17. An evaluation value indicating a characteristic of a temporal change of a chaotic feature of the target range of the measured object from an analysis result of the chaotic analysis processing sequentially obtained according to a temporal change of the measured object. The ultrasonic measurement method according to claim 15, further comprising the step of: