JP2018192117A - Ultrasound observation apparatus, method for operating ultrasound observation apparatus, and program for operating ultrasound observation apparatus - Google Patents

Abstract

To provide an ultrasound observation apparatus, a method for operating the ultrasound observation apparatus, and a program for operating the ultrasound observation apparatus which are able to generate an ultrasound image distinguishable between a blood vessel and a tumor thereon in such a manner that the frame rate is prevented from being decreased.SOLUTION: An ultrasound observation apparatus according to the present invention comprises: a frequency analysis unit for analyzing the frequency of a signal generated based on an ultrasound signal to calculate a plurality of frequency spectra; a feature amount calculation unit for calculating a frequency feature amount based on the frequency spectra calculated by the frequency analysis unit; a comparison unit for comparing the frequency feature amount with a threshold value preset for the frequency feature amount; a sound ray setting unit for setting a sound ray with which Doppler scan is performed based on a comparison result by the comparison unit; and a feature amount image data generation unit for generating feature amount image data indicative of the frequency feature amount based on a blood flow detection result by Doppler scan.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ultrasonic observation apparatus that observes a tissue to be observed using ultrasonic waves, an operation method of the ultrasonic observation apparatus, and an operation program of the ultrasonic observation apparatus.

  Ultrasound may be applied to observe the characteristics of the biological tissue or material that is the object of observation. Specifically, ultrasonic waves are transmitted to the observation target, and predetermined signal processing is performed on the ultrasonic echoes reflected by the observation target, thereby acquiring information related to the characteristics of the observation target.

  An ultrasonic endoscope in which an ultrasonic transducer is provided at the distal end of an insertion portion is used for diagnosis of a living tissue in the body to which ultrasonic waves are applied. An operator such as a doctor operates the operation unit at hand after inserting the insertion unit into the body. By this operation, the ultrasonic transducer acquires an ultrasonic echo, and information (ultrasonic image) based on the ultrasonic echo is generated. The surgeon makes a diagnosis based on the ultrasonic image displayed on the monitor.

  An ultrasonic diagnostic system that displays an ultrasonic image on a monitor using an ultrasonic endoscope as described above is used for more detailed diagnosis or when it is desired to improve the accuracy of results comprehensively from diagnosis from another viewpoint. Ultrasonic images are displayed in various operation modes such as a flow mode, an elast mode, and a contrast agent mode. Specifically, a region of interest is set on a basic B-mode image, and additional information obtained by performing a process such as a calculation corresponding to the set operation mode on the region of interest is two-dimensional. Is generated, superimposed on the B-mode image, and displayed on the monitor.

  Among the modes described above, the flow mode is a mode in which blood is detected by performing Doppler scanning and analyzing Doppler shift, and two-dimensional information in which the presence / absence of blood flow and the direction of blood flow are color-coded is superimposed. In the flow mode, blood flow information is generated based on the amount of change in amplitude or intensity at each depth by performing scan scanning a plurality of times in the same depth direction (for example, see Patent Document 1). In Patent Document 1, a combined image is generated by combining a blood flow image, an elastic image, and a B-mode image in order to improve blood drawing accuracy. According to Patent Document 1, it is possible to distinguish a blood vessel and a tumor in a composite image.

Japanese Patent No. 5938822

  However, in the technique disclosed in Patent Document 1, it is necessary to generate a blood flow image, an elasticity image, and a B-mode image, and this has caused a decrease in the frame rate when generating a composite image.

  The present invention has been made in view of the above, and an ultrasonic observation apparatus and an ultrasonic observation apparatus capable of generating an ultrasonic image capable of distinguishing a blood vessel and a tumor while suppressing a decrease in frame rate It is an object of the present invention to provide an operation method of the above and an operation program of an ultrasonic observation apparatus.

  In order to solve the above-described problems and achieve the object, an ultrasonic observation apparatus according to the present invention includes an ultrasonic transducer that transmits ultrasonic waves to an observation target and receives ultrasonic waves reflected by the observation target. An ultrasonic observation apparatus that generates ultrasonic image data based on an ultrasonic signal acquired by an ultrasonic probe provided, wherein a plurality of frequencies are analyzed by analyzing the frequency of the signal generated based on the ultrasonic signal A frequency analysis unit that calculates a spectrum, a feature amount calculation unit that calculates a frequency feature amount based on the frequency spectrum calculated by the frequency analysis unit, the frequency feature amount, and the frequency feature amount are preset. A comparison unit that compares the first threshold value, a sound ray setting unit that sets a sound ray for performing Doppler scanning based on a comparison result by the comparison unit, and a blood flow detection result by the Doppler scan Based on, characterized in that it comprises a characteristic quantity image data generating unit that generates a characteristic quantity image data indicating the frequency characteristic quantity.

  In the ultrasonic observation apparatus according to the present invention, in the above invention, the feature image data generation unit has a display specification that is different from a display specification of a region in which the blood flow is not detected. The feature amount image data is generated.

  In the ultrasonic observation apparatus according to the present invention, in the above invention, the sound ray setting unit is configured such that the number of pixels corresponding to a feature amount group including frequency feature amounts whose positions are adjacent to each other in the feature amount image data is the number of pixels. Is smaller than a preset second threshold value, the sound ray including the region corresponding to the feature amount group is excluded from the sound ray for executing the Doppler scan.

  In the ultrasonic observation apparatus according to the present invention as set forth in the invention described above, the feature amount image data generation unit generates superimposed image data in which the feature amount image data is superimposed on the ultrasound image data.

  An operation method of an ultrasonic observation apparatus according to the present invention is an ultrasonic signal acquired by an ultrasonic probe including an ultrasonic transducer that transmits ultrasonic waves to an observation target and receives ultrasonic waves reflected by the observation target. A method for operating an ultrasonic observation apparatus that generates ultrasonic image data based on a frequency analysis unit that calculates a plurality of frequency spectra by analyzing a frequency of a signal generated based on the ultrasonic signal A frequency analysis step, a feature amount calculation unit calculates a frequency feature amount based on the frequency spectrum calculated in the frequency analysis step, and a comparison unit calculates the frequency feature amount and the frequency feature amount. A comparison step for comparing with a first threshold set in advance, and a sound ray in which the sound ray setting unit performs Doppler scanning based on the comparison result of the comparison step A sound ray setting step for setting, and a feature amount image data generation unit for generating feature amount image data indicating the frequency feature amount based on a blood flow detection result by the Doppler scanning; It is characterized by including.

  The operation program of the ultrasonic observation apparatus according to the present invention is an ultrasonic signal acquired by an ultrasonic probe including an ultrasonic transducer that transmits ultrasonic waves to an observation target and receives ultrasonic waves reflected by the observation target. Is an operation program for an ultrasonic observation apparatus that generates ultrasonic image data based on the frequency, and the frequency analysis unit calculates a plurality of frequency spectra by analyzing the frequency of the signal generated based on the ultrasonic signal A frequency analysis procedure, a feature quantity calculation unit calculates a frequency feature quantity based on the frequency spectrum calculated in the frequency analysis procedure, and a comparison unit calculates the frequency feature quantity and the frequency feature quantity. The comparison procedure for comparing the first threshold value set in advance with the sound ray setting unit sets the sound ray for performing Doppler scanning based on the comparison result of the comparison procedure. A sound ray setting procedure, and a feature amount image data generation unit that generates feature amount image data indicating the frequency feature amount based on a detection result of blood flow by the Doppler scanning. It is characterized by being executed by an ultrasonic observation apparatus.

  According to the present invention, there is an effect that an ultrasonic image capable of distinguishing a blood vessel and a tumor can be generated while suppressing a decrease in frame rate.

FIG. 1 is a block diagram showing a configuration of an ultrasonic observation system including an ultrasonic observation apparatus according to Embodiment 1 of the present invention. FIG. 2 is a diagram showing the relationship between the reception depth and the amplification factor in the amplification processing performed by the signal amplification unit of the ultrasonic observation apparatus according to Embodiment 1 of the present invention. FIG. 3 is a diagram showing the relationship between the reception depth and the amplification factor in the amplification correction process performed by the amplification correction unit of the ultrasound observation apparatus according to Embodiment 1 of the present invention. FIG. 4 is a diagram schematically showing a data array in one sound ray of the ultrasonic signal. FIG. 5 is a diagram illustrating an example of a frequency spectrum calculated by the frequency analysis unit of the ultrasonic observation apparatus according to Embodiment 1 of the present invention. FIG. 6 is a diagram showing a straight line having as a parameter the correction feature amount corrected by the attenuation correction unit of the ultrasonic observation apparatus according to Embodiment 1 of the present invention. FIG. 7 is a diagram for explaining processing executed by the sound ray setting unit of the ultrasonic observation apparatus according to Embodiment 1 of the present invention. FIG. 8 is a diagram illustrating processing executed by the sound ray setting unit of the ultrasonic observation apparatus according to Embodiment 1 of the present invention. FIG. 9 is a diagram illustrating an example of an image generated by the image processing unit of the ultrasound observation apparatus according to Embodiment 1 of the present invention. FIG. 10 is a flowchart showing an outline of processing performed by the ultrasound observation apparatus according to Embodiment 1 of the present invention. FIG. 11 is a flowchart showing an outline of processing executed by the frequency analysis unit of the ultrasonic observation apparatus according to Embodiment 1 of the present invention. FIG. 12 is a flowchart showing an overview of display specification setting processing executed by the calculation unit of the ultrasonic observation apparatus according to Embodiment 1 of the present invention. FIG. 13 is a diagram illustrating processing executed by the sound ray setting unit of the ultrasonic observation apparatus according to Embodiment 2 of the present invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as “embodiments”) will be described with reference to the accompanying drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of an ultrasound observation system 1 including an ultrasound observation apparatus 3 according to Embodiment 1 of the present invention. An ultrasonic observation system 1 shown in FIG. 1 transmits an ultrasonic wave to a subject to be observed and receives an ultrasonic wave reflected by the subject, an ultrasonic endoscope 2 (ultrasonic probe), An ultrasonic observation device 3 that generates an ultrasonic image based on an ultrasonic signal acquired by the sonic endoscope 2 and a display device 4 that displays the ultrasonic image generated by the ultrasonic observation device 3 are provided.

  The ultrasonic endoscope 2 converts an electrical pulse signal received from the ultrasonic observation device 3 into an ultrasonic pulse (acoustic pulse) and irradiates the subject at the tip thereof, and is reflected by the subject. The ultrasonic transducer 21 converts the ultrasonic echo into an electrical echo signal expressed by a voltage change and outputs it. The ultrasonic transducer 21 may be a convex transducer, a linear transducer, or a radial transducer. The ultrasonic endoscope 2 may be one that mechanically scans the ultrasonic transducer 21, or a plurality of elements are provided in an array as the ultrasonic transducer 21, and the elements involved in transmission and reception are electronically arranged. Electronic scanning may be performed by switching or delaying transmission / reception of each element.

  The ultrasonic endoscope 2 usually has an imaging optical system and an imaging device, and is inserted into the digestive tract (esophagus, stomach, duodenum, large intestine) or respiratory organ (trachea, bronchi) of the subject for digestion. It is possible to image a tube, respiratory organ, and surrounding organs (pancreas, gallbladder, bile duct, biliary tract, lymph node, mediastinal organ, blood vessel, etc.). The ultrasonic endoscope 2 has a light guide that guides illumination light to be irradiated onto the subject during imaging. The light guide has a distal end portion that reaches the distal end of the insertion portion of the ultrasonic endoscope 2 into the subject, and a proximal end portion that is connected to a light source device that generates illumination light. In addition, not only the ultrasonic endoscope 2 but an ultrasonic probe that does not include an imaging optical system and an imaging element may be used.

  The ultrasonic observation device 3 is electrically connected to the ultrasonic endoscope 2 and transmits a transmission signal (pulse signal) including a high voltage pulse to the ultrasonic transducer 21 based on a predetermined waveform and transmission timing. A transmission / reception unit 31 that receives an echo signal as an electrical reception signal from the ultrasonic transducer 21 and generates and outputs digital radio frequency (RF) data (hereinafter referred to as RF data); A signal processing unit 32 that generates digital B-mode reception data based on the RF data received from the unit 31; a calculation unit 33 that performs predetermined calculations on the RF data received from the transmission / reception unit 31; An image processing unit 34 that generates data and an input unit 35 that is implemented using a user interface such as a keyboard, a mouse, and a touch panel, and receives input of various types of information. And a control unit 36 that controls the entire ultrasound observation system 1 and a storage unit 37 that stores various types of information necessary for the operation of the ultrasound observation apparatus 3.

The transmission / reception unit 31 includes a signal amplification unit 311 that amplifies the echo signal. The signal amplification unit 311 performs STC (Sensitivity Time Control) correction in which an echo signal having a larger reception depth is amplified with a higher amplification factor. FIG. 2 is a diagram illustrating the relationship between the reception depth and the amplification factor in the amplification process performed by the signal amplification unit 311. The reception depth z shown in FIG. 2 is an amount calculated based on the elapsed time from the reception start point of the ultrasonic wave. As shown in FIG. 2, when the reception depth z is smaller than the threshold z _th , the amplification factor β (dB) increases linearly from β ₀ to β _th (> β ₀ ) as the reception depth z increases. Further, the amplification factor β takes a constant value β _th when the reception depth z is equal to or greater than the threshold value z _th . The value of the threshold value z _th is such a value that the ultrasonic signal received from the observation target is almost attenuated and the noise becomes dominant. More generally, when the reception depth z is smaller than the threshold value z _th , the amplification factor β may increase monotonously as the reception depth z increases. The relationship shown in FIG. 2 is stored in the storage unit 37 in advance.

  The transmission / reception unit 31 performs processing such as filtering on the echo signal amplified by the signal amplification unit 311 and then performs A / D conversion to generate time domain RF data, and the signal processing unit 32 and the calculation unit To 33. When the ultrasonic endoscope 2 has a configuration that electronically scans the ultrasonic transducer 21 in which a plurality of elements are arranged in an array, the transmission / reception unit 31 includes a plurality of beams for beam synthesis corresponding to the plurality of elements. A channel circuit is included.

  The frequency band of the pulse signal transmitted by the transmission / reception unit 31 may be a wide band that substantially covers the linear response frequency band of the electroacoustic conversion of the pulse signal to the ultrasonic pulse in the ultrasonic transducer 21. In addition, the various processing frequency bands of the echo signal in the signal amplifying unit 311 may be a wide band that substantially covers the linear response frequency band of the acoustoelectric conversion of the ultrasonic transducer 21 into the echo signal of the ultrasonic echo. Accordingly, it is possible to perform accurate approximation when performing frequency spectrum approximation processing, which will be described later.

  The transmission / reception unit 31 transmits various control signals output from the control unit 36 to the ultrasonic endoscope 2 and receives various types of information including an identification ID from the ultrasonic endoscope 2 and receives the control unit 36. It also has a function to transmit to.

The signal processing unit 32 performs known processing such as band-pass filter, envelope detection, and logarithmic conversion on the RF data to generate digital B-mode reception data. In logarithmic conversion, the common logarithm of the amount obtained by dividing the RF data by the reference voltage V _c is taken and expressed as a decibel value. The signal processing unit 32 outputs the generated B-mode reception data to the image processing unit 34. The signal processing unit 32 is realized using a CPU (Central Processing Unit), various arithmetic circuits, and the like.

  The calculation unit 33 performs amplification correction on the RF data generated by the transmission / reception unit 31 so as to make the amplification factor β constant regardless of the reception depth z, and fast Fourier transform on the RF data subjected to the amplification correction. Based on the frequency spectrum calculated by the frequency analysis unit 332 and the frequency analysis unit 332 that calculates the frequency spectrum by performing frequency analysis by performing transformation (FFT: Fast Fourier Transform), the feature amount of the frequency spectrum is calculated. The Doppler scan is executed based on the feature amount calculation unit 333 to be calculated, the comparison unit 334 that compares the feature amount calculated by the feature amount calculation unit 333 and the set threshold value, and the comparison result by the comparison unit 334. A sound ray setting unit 335 that sets a sound ray (hereinafter referred to as a Doppler scan execution sound ray) and a blood flow detection that detects a blood flow based on a scan result by Doppler scan Has a 336, based on the detection result by the blood flow detecting section 336, a display specification setting unit 337 for setting the display specifications of the feature amount of the display target to be displayed on the display device 4, a. The calculation unit 33 is realized using a CPU, various calculation circuits, and the like.

FIG. 3 is a diagram illustrating a relationship between the reception depth and the amplification factor in the amplification correction process performed by the amplification correction unit 331. As shown in FIG. 3, the amplification rate β (dB) in the amplification correction processing performed by the amplification correction unit 331 takes the maximum value β _th −β ₀ when the reception depth z is zero, and the reception depth z is zero to the threshold value z. It decreases linearly until it reaches _th , and is zero when the reception depth z is greater than or equal to the threshold value z _th . The amplification correction unit 331 amplifies and corrects the RF data with the amplification factor β determined in this way, thereby canceling the influence of the STC correction in the signal processing unit 32 and outputting a signal with a constant amplification factor β _th. . Needless to say, the relationship between the reception depth z and the amplification factor β performed by the amplification correction unit 331 differs depending on the relationship between the reception depth and the amplification factor in the signal processing unit 32.

  The reason for performing such amplification correction will be described. STC correction is a correction process that eliminates the influence of attenuation from the amplitude of the analog signal waveform by amplifying the amplitude of the analog signal waveform uniformly over the entire frequency band and with a gain that monotonously increases with respect to the depth. is there. For this reason, when generating a B-mode image to be displayed by converting the amplitude of the echo signal into luminance, and when scanning a uniform tissue, the luminance value is constant regardless of the depth by performing STC correction. become. That is, an effect of eliminating the influence of attenuation from the luminance value of the B-mode image can be obtained.

  On the other hand, when using the result of calculating and analyzing the frequency spectrum of the ultrasonic wave as in the present embodiment, the STC correction cannot accurately eliminate the influence of attenuation accompanying the propagation of the ultrasonic wave. This is because, although the attenuation amount generally varies depending on the frequency (see Equation (1) described later), the STC correction amplification factor changes only according to the distance and has no frequency dependence.

  To solve the above-described problem, that is, when the result of calculating and analyzing the frequency spectrum of the ultrasonic wave is used, the effect of attenuation due to the propagation of the ultrasonic wave cannot be accurately eliminated even by the STC correction. Outputs a reception signal subjected to STC correction when generating a B-mode image, while generating a new transmission different from the transmission for generating the B-mode image when generating an image based on the frequency spectrum. It is conceivable to output a reception signal that has not been subjected to STC correction. However, in this case, there is a problem that the frame rate of the image data generated based on the received signal is lowered.

  Therefore, in the present embodiment, in order to eliminate the influence of the STC correction on the signal subjected to the STC correction for the B-mode image while maintaining the frame rate of the generated image data, the amplification correction unit 331 Correct the gain.

  The frequency analysis unit 332 samples the RF data (line data) of each sound ray amplified and corrected by the amplification correction unit 331 at predetermined time intervals to generate sample data. The frequency analysis unit 332 calculates a frequency spectrum at a plurality of locations (data positions) on the RF data by performing FFT processing on the sample data group. Here, the “frequency spectrum” means “frequency distribution of intensity at a certain reception depth z” obtained by performing FFT processing on a sample data group. In addition, “intensity” as used herein refers to parameters such as the voltage of the echo signal, the power of the echo signal, the sound pressure of the ultrasonic echo, the acoustic energy of the ultrasonic echo, the amplitude and time integral value of these parameters, and combinations thereof. Points to either.

  Generally, when the observation target is a living tissue, the frequency spectrum shows a tendency that varies depending on the properties of the living tissue scanned with ultrasonic waves. This is because the frequency spectrum has a correlation with the size, number density, acoustic impedance, and the like of the scatterer that scatters ultrasonic waves. The “characteristics of the biological tissue” referred to here includes, for example, malignant tumor (cancer), benign tumor, endocrine tumor, mucinous tumor, normal tissue, cyst, vascular vessel and the like.

FIG. 4 is a diagram schematically showing a data array in one sound ray of the ultrasonic signal. In the sound ray SR _k shown in the figure, a white or black rectangle means data at one sample point. In the sound ray SR _k , the data located on the right side is sample data from a deeper location when measured from the ultrasonic transducer 21 along the sound ray SR _k (see the arrow in FIG. 4). The sound ray SR _k is discretized at a time interval corresponding to a sampling frequency (for example, 50 MHz) in A / D conversion performed by the transmission / reception unit 31. FIG. 4 shows the case _where the eighth data position of the sound ray SR _k of number k is set as the initial value Z ^(k) _{0 in} the direction of the reception depth z, but the position of the initial value is arbitrarily set. be able to. The calculation result by the frequency analysis unit 332 is obtained as a complex number and stored in the storage unit 37.

A data group F _j (j = 1, 2,..., K) shown in FIG. 4 is a sample data group to be subjected to FFT processing. In general, in order to perform FFT processing, a sample data group needs to have a power number of 2 data. In this sense, the sample data group F _j (j = 1, 2,..., K−1) is a normal data group with the number of data 16 (= 2 ⁴ ), while the sample data group F _K is Since the number of data is 12, it is an abnormal data group. When performing an FFT process on an abnormal data group, a process for generating a normal sample data group is performed by inserting zero data in an insufficient amount. This point will be described in detail when the processing of the frequency analysis unit 332 is described (see FIG. 9).

FIG. 5 is a diagram illustrating an example of a frequency spectrum calculated by the frequency analysis unit 332. In FIG. 5, the horizontal axis is the frequency f. In FIG. 5, the vertical axis represents the common logarithm (decibel expression) I = ₁₀ log ₁₀ (I ₀ / I _c ) obtained by dividing the intensity I ₀ by the reference intensity I _c (constant). It will be described later regression line L ₁₀ shown in FIG. In the present embodiment, the curve and the straight line are composed of a set of discrete points.

In the frequency spectrum C ₁ shown in FIG. 5, the lower limit frequency f _L and the upper limit frequency f _H of the frequency band used for the subsequent calculation are the frequency band of the ultrasonic transducer 21 and the frequency band of the pulse signal transmitted by the transmitting / receiving unit 31. It is a parameter determined based on the above. Hereinafter, in FIG. 5, the frequency band determined by the lower limit frequency f _L and the upper limit frequency f _H is referred to as “frequency band F”.

  The feature amount calculation unit 333 calculates the feature amounts of a plurality of frequency spectra in a set region of interest (hereinafter sometimes referred to as ROI (Region of Interest)). The feature amount calculation unit 333 approximates the frequency spectrum with a straight line, and calculates the feature amount of the frequency spectrum before performing the attenuation correction process (hereinafter referred to as pre-correction feature amount), and the approximation unit 333a calculates the feature amount. An attenuation correction unit 333b that calculates a feature amount by performing attenuation correction on the pre-correction feature amount.

The approximating unit 333a performs a regression analysis of the frequency spectrum in a predetermined frequency band and approximates the frequency spectrum with a linear expression (regression line), thereby calculating a pre-correction feature quantity characterizing the approximated primary expression. For example, in the case of the frequency spectrum C ₁ shown in FIG. 5, the approximating unit 333 a performs a regression analysis in the frequency band F and approximates the frequency spectrum C ₁ with a linear expression to obtain a regression line L ₁₀ . In other words, the approximating unit 333a has a mid-band fit that is a value on the regression line of the slope a ₀ , the intercept b ₀ of the regression line L ₁₀ , and the center frequency f _M = (f _L + f _H ) / 2 of the frequency band F. (Mid-band fit) c ₀ = a ₀ f _M + b ₀ is calculated as a feature amount before correction.

Of the three pre-correction feature quantities, the slope a ₀ has a correlation with the size of the ultrasonic scatterer, and it is generally considered that the larger the scatterer, the smaller the slope. The intercept b ₀ has a correlation with the size of the scatterer, the difference in acoustic impedance, the number density (concentration) of the scatterer, and the like. Specifically, the intercept b ₀ has a larger value as the scatterer is larger, has a larger value as the difference in acoustic impedance is larger, and has a larger value as the number density of the scatterers is larger. The mid-band fit c ₀ is an indirect parameter derived from the slope a ₀ and the intercept b ₀ and gives the intensity of the spectrum at the center in the effective frequency band. Therefore, the midband fit c ₀ is considered to have a certain degree of correlation with the brightness of the B-mode image in addition to the size of the scatterer, the difference in acoustic impedance, and the number density of the scatterers. Note that the feature amount calculation unit 333 may approximate the frequency spectrum with a second-order or higher polynomial by regression analysis.

The correction performed by the attenuation correction unit 333b will be described. In general, the ultrasonic attenuation A (f, z) is attenuation that occurs while the ultrasonic waves reciprocate between the reception depth 0 and the reception depth z, and the intensity change before and after the reciprocation (difference in decibel expression). ). The attenuation amount A (f, z) is empirically known to be proportional to the frequency in a uniform tissue, and is expressed by the following equation (1).
A (f, z) = 2αzf (1)
Here, the proportionality constant α is an amount called an attenuation rate. Z is the ultrasonic reception depth, and f is the frequency. When the observation target is a living body, a specific value of the attenuation rate α is determined according to the part of the living body. The unit of the attenuation rate α is, for example, dB / cm / MHz. In the present embodiment, a configuration in which the value of the attenuation rate α can be changed by an input from the input unit 35 is also possible.

The attenuation correction unit 333b performs attenuation correction according to the following equations (2) to (4) with respect to the pre-correction feature values (slope a ₀ , intercept b ₀ , midband fit c ₀ ) extracted by the approximation unit 333a. As a result, feature quantities a, b, and c are calculated. In the first embodiment, the attenuation correction unit 333b performs attenuation correction to calculate the feature quantities a, b, and c that are frequency feature quantities.
a = a ₀ + 2αz (2)
b = b ₀ (3)
c = c ₀ + A (f _M , z) = c ₀ + 2αzf _M (= af _M + b) (4)
As is clear from equations (2) and (4), the attenuation correction unit 333b performs correction with a larger correction amount as the ultrasonic reception depth z is larger. Further, according to the equation (3), the correction related to the intercept is an identity transformation. This is because the intercept is a frequency component corresponding to a frequency of 0 (Hz) and is not affected by attenuation.

FIG. 6 is a diagram illustrating a straight line having the feature amounts a, b, and c calculated by the attenuation correction unit 333b as parameters. The equation for the straight line L ₁ is
I = af + b = (a ₀ + 2αz) f + b ₀ (5)
It is represented by As is clear from this equation (5), the straight line L ₁ has a larger slope (a> a ₀ ) and the same intercept (b = b ₀ ) compared to the straight line L ₁₀ before attenuation correction. is there.

  The comparison unit 334 compares the feature amount to be displayed among the feature amounts a, b, and c calculated by the feature amount calculation unit 333 at each sample point with a preset threshold value. This threshold value is a value indicating a feature amount, and is a value for distinguishing blood vessels and tumors from other tissues. For example, when the feature quantity to be displayed is set to the feature quantity c, the feature quantity c is compared with a threshold set for the feature quantity c. The comparison unit 334 generates a comparison result (a magnitude relationship between the feature amount c and the threshold value) for each reception depth of each sound ray and outputs the result to the sound ray setting unit 335.

  The sound ray setting unit 335 sets a Doppler scanning execution sound ray based on the comparison result by the comparison unit 334. In the first embodiment, the sound ray setting unit 335 extracts sound rays having a characteristic amount smaller than the threshold value, and is sandwiched between sound rays located at both ends in the ultrasonic scanning direction among the extracted sound rays. The sound ray in the selected area is set as the Doppler scanning execution sound ray.

7 and 8 are diagrams for explaining processing executed by the sound ray setting unit of the ultrasonic observation apparatus according to Embodiment 1 of the present invention. As shown in FIG. 7, when a tumor B _G and a blood vessel B _L are depicted in the B-mode image W _B , frequency feature amounts (feature amounts a) corresponding to the tumor B _G and the blood vessel B _L , respectively. , B, c) are different from other positions. At this time, in the comparison result of the comparison unit 334, it is assumed that the feature amount of the region indicating the tumor _BG and the feature amount of the region indicating the blood vessel _BL are below the threshold value. In this case, the sound ray setting unit 335 extracts sound rays including a region below the threshold, and among the extracted sound rays, the sound rays SR _A and SR _B positioned at both ends in the ultrasonic scanning direction, A sound ray in an area sandwiched between the sound rays SR _A and SR _B is set as a Doppler scanning execution sound ray (see FIG. 8). Incidentally, as shown in FIG. 8, the displaying the Doppler scan execution acoustic line B-mode image W _B, may be displayed for confirmation.

  The control unit 36 causes the ultrasonic transducer 21 to perform Doppler scanning in a range corresponding to the sound ray set by the sound ray setting unit 335. The ultrasonic observation device 3 acquires a plurality of echo signals for each reception depth at each sound ray by repeating the process in which the ultrasonic transducer 21 transmits ultrasonic waves to each depth.

  The blood flow detection unit 336 detects blood flow at each reception depth based on an echo signal acquired by Doppler scanning. The blood flow detection unit 336 can detect blood flow using a known method. The blood flow detection unit 336 detects blood flow for each reception depth and outputs the detection result to the display specification setting unit 337.

  The display specification setting unit 337 sets the display specification of the feature quantity of the display target to be displayed on the display device 4 in the region where the blood flow detection unit 336 detects the blood flow. Specifically, in the first embodiment, the display specification setting unit 337 does not give color information to the feature amount c in the region where the blood flow detection unit 336 detects blood flow (hereinafter, blood flow detection region). Set as follows. For this reason, a color corresponding to the feature amount c is not given to a region where the blood flow detection unit 336 detects blood flow, and a B-mode image is displayed in that region.

  The image processing unit 34 visually recognizes the feature amount calculated by the B-mode image data generation unit 341 that generates B-mode image data that is an ultrasonic image to be displayed by converting the amplitude of the echo signal into luminance, and the attenuation correction unit 333b. A feature amount image data generation unit 342 that generates feature amount image data to be displayed together with the B-mode image in association with information.

  The B-mode image data generation unit 341 performs signal processing using known techniques such as gain processing, contrast processing, and γ correction processing on the B-mode reception data received from the signal processing unit 32, and the display device 4. The B-mode image data is generated by thinning out data according to the data step width determined according to the image display range. The B-mode image is a grayscale image in which values of R (red), G (green), and B (blue), which are variables when the RGB color system is adopted as a color space, are matched.

  The B-mode image data generation unit 341 performs coordinate conversion for rearranging the B-mode reception data from the signal processing unit 32 so that the scanning range can be spatially represented correctly, and then performs interpolation processing between the B-mode reception data. As a result, the gaps between the B-mode reception data are filled, and B-mode image data is generated. The B-mode image data generation unit 341 outputs the generated B-mode image data to the feature amount image data generation unit 342.

  The feature amount image data generation unit 342 generates feature amount image data to which visual information related to the feature amount calculated by the feature amount calculation unit 333 is added, and the feature amount image data is converted into each image of the B-mode image data. Superposed image data is generated by superimposing the pixel. The feature amount image data generation unit 342 gives visual information set to the area set in the display specification setting unit 337. The feature amount image data generation unit 342 does not superimpose visual information regardless of the feature amount, for example, for an area that is set not to be given a color.

For example, the feature amount image data generation unit 342 applies the sample data group F to a pixel region corresponding to the data amount of one sample data group F _j (j = 1, 2,..., K) illustrated in FIG. Visual information corresponding to the characteristic amount of the frequency spectrum calculated from _j is assigned. The feature amount image data generation unit 342 generates a feature amount image by associating a hue as visual information with any one of the above-described inclination, intercept, and midband fit, for example. Specifically, the feature amount image data generation unit 342 assigns visual information based on the color scheme set by the display specification setting unit 337 when the hue as the visual information is associated with the feature amount a. As visual information related to the feature amount, in addition to hue, for example, a color space constituting a predetermined color system such as saturation, brightness, luminance value, R (red), G (green), B (blue), etc. You can list variables.

FIG. 9 is a diagram illustrating an example of an image generated by the image processing unit of the ultrasound observation apparatus according to Embodiment 1 of the present invention. Figure 9 is an image by the image processing unit 34 has generated in accordance with the display specification set by the display specification setting unit 337, a diagram showing the superimposed image W _F obtained by superimposing the characteristic amount image in B mode image W _B is there. As shown in FIG. 9, in the region B _GF corresponding to the tumor B _G, while the color information (indicated by hatching in FIG. 9) is applied, in the region B _LF corresponding to the blood vessel B _L is The B mode image is displayed without color information (color is colorless). In FIG. 9, the outer edge of the region B _LF corresponding to the blood vessel _BL is shown by a broken line for the sake of explanation, but the broken line is not displayed in the actual image.

  The control unit 36 is realized using a CPU (Central Processing Unit) having arithmetic and control functions, various arithmetic circuits, and the like. The control unit 36 controls the ultrasonic observation apparatus 3 in an integrated manner by reading information stored and stored in the storage unit 37 from the storage unit 37 and executing various arithmetic processes related to the operation method of the ultrasonic observation apparatus 3. To do. Note that the control unit 36 may be configured using a CPU or the like common to the signal processing unit 32 and the calculation unit 33.

  The storage unit 37 stores a plurality of feature amounts calculated for each frequency spectrum by the attenuation correction unit 333b and image data generated by the image processing unit 34. In addition, the storage unit 37 includes a display specification information storage unit 371 that stores a threshold value for the feature amount, a color arrangement condition set by the display specification setting unit 337, and the like.

  In addition to the above, the storage unit 37 may include, for example, information necessary for the amplification process (relationship between the amplification factor β and the reception depth z shown in FIG. 2) and information necessary for the amplification correction process (the amplification factor β shown in FIG. 3). (Relationship with reception depth z), information necessary for attenuation correction processing (see equation (1)), window function information necessary for frequency analysis processing (Hamming, Hanning, Blackman, etc.), and the like are stored.

  In addition, the storage unit 37 stores various programs including an operation program for executing the operation method of the ultrasound observation apparatus 3. The operation program can be recorded on a computer-readable recording medium such as a hard disk, a flash memory, a CD-ROM, a DVD-ROM, or a flexible disk and widely distributed. The various programs described above can also be obtained by downloading via a communication network. The communication network here is realized by, for example, an existing public line network, a LAN (Local Area Network), a WAN (Wide Area Network) or the like, and may be wired or wireless.

  The storage unit 37 having the above configuration is realized using a ROM (Read Only Memory) in which various programs and the like are installed in advance, and a RAM (Random Access Memory) that stores calculation parameters and data of each process. .

  FIG. 10 is a flowchart showing an outline of processing performed by the ultrasonic observation apparatus 3 having the above configuration. First, the ultrasonic observation device 3 receives an echo signal as a measurement result of an observation target by the ultrasonic transducer 21 from the ultrasonic endoscope 2 (step S1).

  The signal amplifying unit 311 that has received the echo signal from the ultrasonic transducer 21 amplifies the echo signal (step S2). Here, the signal amplifying unit 311 performs amplification (STC correction) of the echo signal based on the relationship between the amplification factor and the reception depth shown in FIG. 2, for example.

  Subsequently, the B-mode image data generation unit 341 generates B-mode image data using the echo signal amplified by the signal amplification unit 311 and outputs the B-mode image data to the display device 4 (step S3). The display device 4 that has received the B-mode image data displays a B-mode image corresponding to the B-mode image data (step S4).

  The amplification correction unit 331 performs amplification correction on the signal output from the transmission / reception unit 31 so that the amplification factor is constant regardless of the reception depth (step S5). Here, the amplification correction unit 331 performs amplification correction so that, for example, the relationship between the amplification factor and the reception depth illustrated in FIG. 3 is established.

  Thereafter, the frequency analysis unit 332 calculates frequency spectra for all the sample data groups by performing frequency analysis by FFT calculation (step S6: frequency analysis step). FIG. 11 is a flowchart showing an outline of the processing executed by the frequency analysis unit 332 in step S6. Hereinafter, the frequency analysis process will be described in detail with reference to the flowchart shown in FIG.

First, the frequency analysis unit 332 sets k ₀ as a counter k (number k) for identifying a sound ray to be analyzed (step S21).

Subsequently, the frequency analysis unit 332 sets an initial value Z ^(k) ₀ of a data position (corresponding to a reception depth) Z ^(k) representing a series of data groups (sample data group) acquired for the FFT calculation. (Step S22). For example, FIG. 4 shows a case _where the eighth data position of the sound ray SR _k is set as the initial value Z ^(k) ₀ as described above.

  Thereafter, the frequency analysis unit 332 acquires a sample data group (step S23), and causes the window function stored in the storage unit 37 to act on the acquired sample data group (step S24). By applying the window function to the sample data group in this way, it is possible to avoid the sample data group from becoming discontinuous at the boundary and to prevent the occurrence of artifacts.

Subsequently, the frequency analysis unit 332 determines whether or not the sample data group at the data position Z ^(k) is a normal data group (step S25). As described with reference to FIG. 4, the sample data group needs to have the number of powers of two. Hereinafter, the number of data in the normal sample data group is 2 ⁿ (n is a positive integer). In the present embodiment, the data position Z ^(k) is set to be the center of the sample data group to which the data position Z ^(k) belongs as much as possible. Specifically, since the number of data in the sample data group is 2 ⁿ , the data position Z ^(k) is set to the 2 ⁿ / 2 (= 2 ^n-1 ) th position close to the center of the sample data group. The In this case, the sample data group is normal when there are 2 ⁿ⁻¹ −1 (= N ⁾ data in front of the data position Z ^(k) and 2 behind the data position Z ^{(k). This} means that there are ^n-1 (= M) data. In the case shown in FIG. 4, the sample data groups F ₁ , F ₂ , F ₃ ,..., F _K-1 are all normal. FIG. 4 illustrates the case of n = 4 (N = 7, M = 8).

If the result of determination in step S25 is that the sample data group at data position Z ^(k) is normal (step S25: Yes), the frequency analysis unit 332 proceeds to step S27 described later.

If the result of determination in step S25 is that the sample data group at the data position Z ^(k) is not normal (step S25: No), the frequency analysis unit 332 inserts zero data as much as the deficient amount into a normal sample data group. Generate (step S26). A window function is applied to the sample data group determined to be not normal in step S25 (for example, the sample data group F _{K in} FIG. 4) before adding zero data. For this reason, even if zero data is inserted into the sample data group, discontinuity of data does not occur. After step S26, the frequency analysis unit 332 proceeds to step S27 described later.

  In step S27, the frequency analysis unit 332 obtains a frequency spectrum that is a frequency distribution of amplitude by performing an FFT operation using the sample data group (step S27).

Subsequently, the frequency analysis unit 332 changes the data position Z ^(k) by the step width D (step S28). It is assumed that the step width D is stored in advance in the storage unit 37. FIG. 4 illustrates a case where D = 15. The step width D is desirably matched with the data step width used when the B-mode image data generation unit 341 generates B-mode image data. However, if the amount of calculation in the frequency analysis unit 332 is to be reduced, the step width D A value larger than the data step width may be set as the width D.

Thereafter, the frequency analysis unit 332 determines whether or not the data position Z ^(k) is larger than the maximum value Z ^(k) _max in the sound ray SR _k (step S29). When the data position Z ^(k) is larger than the maximum value Z ^(k) _max (step S29: Yes), the frequency analysis unit 332 increases the counter k by 1 (step S30). This means that the processing is shifted to the next sound ray. On the other hand, when the data position Z ^(k) is equal to or less than the maximum value Z ^(k) _max (step S29: No), the frequency analysis unit 332 returns to step S23. In this way, the frequency analysis unit 332 performs an FFT operation on [(Z ^(k) _max −Z ^(k) ₀ +1) / D + 1] sample data groups for the sound ray SR _k . Here, [X] represents the maximum integer not exceeding X.

After step S30, the frequency analysis unit 332 determines whether or not the counter k is greater than the maximum value k _max (step S31). When the counter k is larger than the maximum value k _max (step S31: Yes), the frequency analysis unit 332 ends the series of frequency analysis processing. On the other hand, when the counter k is equal to or less than the maximum value k _max (step S31: No), the frequency analysis unit 332 returns to step S22. The maximum value k _max is a value arbitrarily input by a user such as an operator through the input unit 35 or a value preset in the storage unit 37.

In this way, the frequency analysis unit 332 performs the FFT operation a plurality of times for each of (k _max −k ₀ +1) sound rays in the analysis target region. The result of the FFT operation is stored in the storage unit 37 together with the reception depth and the reception direction.

  In the above description, the frequency analysis unit 332 performs the frequency analysis process on all the areas where the ultrasonic signal is received. However, the frequency analysis process is performed only within the set region of interest. It is also possible.

  Subsequent to the frequency analysis processing in step S6 described above, the feature amount calculation unit 333 calculates pre-correction feature amounts of a plurality of frequency spectra, and performs ultrasonic attenuation of the pre-correction feature amounts of the respective frequency spectra. A correction feature amount of each frequency spectrum is calculated by performing attenuation correction to eliminate the influence (steps S7 to S8: feature amount calculation step).

In step S7, the approximating unit 333a calculates a pre-correction feature amount corresponding to each frequency spectrum by performing regression analysis on each of the plurality of frequency spectra generated by the frequency analyzing unit 332 (step S7). Specifically, the approximating unit 333a approximates each frequency spectrum with a linear expression by performing regression analysis, and calculates a slope a ₀ , an intercept b ₀ , and a midband fit c ₀ as pre-correction feature values. For example, the straight line L ₁₀ shown in FIG. 5 is a regression line approximated by the approximation unit 333 a to the frequency spectrum C ₁ of the frequency band F by regression analysis.

Subsequently, the attenuation correction unit 333b calculates a correction feature amount by performing attenuation correction on the pre-correction feature amount approximated to each frequency spectrum by the approximation unit 333a, thereby calculating a correction feature amount. The corrected feature amount is stored in the storage unit 37 (step S8). A straight line L ₁ illustrated in FIG. 6 is an example of a straight line obtained by the attenuation correction unit 333b performing the attenuation correction process.

In step S8, the attenuation correction unit 333b obtains the data position Z = (f _sp / 2v _s) obtained using the sound ray data array of the ultrasonic signal at the reception depth z in the above-described equations (2) and (4). ) Calculate by substituting Dn. Here, f _sp is the sampling frequency, v _s of the data speed of sound, D is the number of data step from the first data of step width, n represents sound ray to the data position of the sample data group to be processed. For example, the sampling frequency f _sp data and 50 MHz, the sound velocity v _s and 1530 m / sec, when a 15 step width D employs a data sequence shown in FIG. 4, a z = 0.2295n (mm).

  Thereafter, for each pixel in the B-mode image data generated by the B-mode image data generation unit 341, the calculation unit 33 sets a display specification of the feature amount to be displayed among the feature amounts calculated in step S8 ( Step S9: Display specification setting step). FIG. 12 is a flowchart showing an overview of display specification setting processing executed by the calculation unit of the ultrasonic observation apparatus according to Embodiment 1 of the present invention.

  In step S40, the computing unit 33 first causes the comparison unit 334 to compare the feature quantity to be displayed with a preset threshold value (comparison step). As a result of the comparison by the comparison unit 334, the calculation unit 33 determines whether there is a feature amount that is equal to or less than a threshold value. Here, when the calculation unit 33 determines that there is a feature amount equal to or less than the threshold (step S40: Yes), the calculation unit 33 proceeds to step S41.

  In step S41 following step S40, the sound ray setting unit 335 sets a Doppler scanning execution sound ray based on the comparison result by the comparison unit 334 (sound ray setting step). As described above, the sound ray setting unit 335, among sound rays having a feature amount equal to or less than the threshold value, is located at both ends of the ultrasonic scanning direction, and the sound in the region sandwiched between these sound rays. The line is set as a Doppler scanning execution sound line (see FIG. 8).

  In step S <b> 42 subsequent to step S <b> 41, the control unit 36 causes the ultrasonic transducer 21 to perform Doppler scanning in a scanning range corresponding to the sound ray set by the sound ray setting unit 335. The ultrasonic transducer 21 repeats the process of transmitting ultrasonic waves along the scanning direction, and acquires a plurality of echo signals for each reception depth at each sound ray.

  In step S43 following step S42, the blood flow detection unit 336 detects blood flow at each reception depth based on the echo signal acquired by Doppler scanning. The blood flow detection unit 336 detects blood flow for each reception depth and outputs the detection result to the display specification setting unit 337.

  In step S44 subsequent to step S43, the display specification setting unit 337 sets the display specification of the feature quantity of the display target to be displayed on the display device 4 in the area where the blood flow detection unit 336 detects the blood flow in the feature quantity image. To do. For example, the display specification setting unit 337 sets the color information to be colorless for the feature amount in the region where the blood flow detection unit 336 detects the blood flow.

  On the other hand, when the calculation unit 33 determines in step S40 that there is no feature amount equal to or less than the threshold (step S40: No), the calculation unit 33 proceeds to step S45.

  In step S45, the arithmetic unit 33 maintains the normal setting. In the generation of the feature amount image data performed by the feature amount image data generation unit 342, the arithmetic unit 33 superimposes visual information corresponding to the feature amount according to the conditions stored in the display specification setting information storage unit 371 in advance. Set to display specifications like this, or set to maintain the display specifications.

  In this way, the calculation unit 33 sets the display specification of the feature quantity to be displayed.

  Returning to FIG. 10, in step S <b> 10 following step S <b> 9, the feature amount image data generation unit 342 calculates the feature amount calculated in step S <b> 8 for each pixel in the B mode image data generated by the B mode image data generation unit 341. The feature amount image data is generated by superimposing the visual information according to the display specifications set in step S44 or S45 (step S10: feature amount image data generation step). At this time, the feature image data generation unit 342 gives the visual information set for the region to the region set by the display specification setting unit 337. For example, the feature amount image data generation unit 342 generates feature amount image data that makes the visual information colorless (no color is superimposed) regardless of the feature amount for the set region.

  Thereafter, the display device 4 displays a superimposed image in which the feature amount image corresponding to the feature amount image data generated by the feature amount image data generation unit 342 is superimposed on the B-mode image under the control of the control unit 36 ( Step S11). The feature amount image includes, for example, a superimposed image that displays an image in which visual information related to the feature amount is superimposed on a B-mode image, observation target identification information, and the like.

  The image to be displayed may include feature amount information, approximate expression information, image information such as gain and contrast, and the like. Further, the B-mode image corresponding to the superimposed image may be displayed side by side with the feature amount image.

  According to the first embodiment of the present invention described above, the calculation unit 33 calculates a feature amount from the result of frequency analysis, compares the feature amount with a preset threshold value, and falls below the threshold value. A sound ray including a feature amount is extracted, and a range where Doppler scanning is performed from the extracted sound ray is set. Thus, in the past, Doppler scanning was performed on the entire ultrasound scanning region. In the first embodiment, however, Doppler scanning is performed only on regions (sound rays) including tumors and blood vessels. Data for distinguishing blood vessels is acquired. According to the first embodiment, an ultrasonic image capable of distinguishing a blood vessel and a tumor can be generated while suppressing a decrease in frame rate. The surgeon can easily recognize a tumor and a blood vessel from the image generated according to the first embodiment and perform an appropriate diagnosis.

  In the first embodiment described above, it has been described that Doppler scanning is performed in a range corresponding to the sound ray set by the sound ray setting unit 335 under the control of the control unit 36. The sound ray setting unit 335 may set a sound ray to be subjected to Doppler scanning by thinning out sound rays. As a result, the number of transmission / reception times of Doppler scanning can be reduced, and further reduction in the frame rate can be suppressed. The sound ray setting unit 335 may change the thinning method according to the size of the region formed by the plurality of sound rays that are set.

  Further, in the first embodiment described above, it has been described that the feature amount below the threshold is extracted and the Doppler scan execution sound ray is set. However, depending on the type of feature amount, the feature amount larger than the threshold is a blood vessel or the like. When a tissue to be detected is indicated, a sound ray having a feature amount larger than a threshold value may be extracted, and a sound ray for performing Doppler scanning may be set from the extracted sound ray.

(Embodiment 2)
FIG. 13 is a diagram illustrating processing executed by the sound ray setting unit of the ultrasonic observation apparatus according to Embodiment 2 of the present invention. In the second embodiment, even when the feature amount is lower than the threshold value, sound rays for performing Doppler scanning are set based on the number of pixels included in the feature amount group. The configuration of the ultrasonic observation system will be described assuming that the configuration of the ultrasonic observation system 1 described above is the same. Only the parts different from the first embodiment will be described below.

As illustrated in FIG. 13, when the blood vessel B _L and the minute tissues B _N 1 to B _N 3 whose feature amounts are lower than the threshold value are depicted, in the first embodiment, the sound is determined based on the comparison result of the comparison unit 334. line SR _C, and SR _Z, and a sound ray in a region sandwiched by a sound ray SR _C and the sound ray SR _Z, is set to the Doppler scan run sound ray. However, microstructure B _N 1 to B _N 3 is clear that not a blood vessel B _L from its size, but the feature quantity is below the threshold value, it is not necessary to perform a Doppler scan. For this reason, in the second embodiment, the sound ray including such a minute region is excluded from the Doppler scanning execution sound ray.

  In the second embodiment, the comparison unit 334 compares the feature quantity with the threshold value, and counts the number of pixels of the feature quantity group that is a group of feature quantities that are below the threshold value as a result of the comparison. The threshold value for the count value is compared with a threshold value for determining that the Doppler scanning is not performed. Here, the feature amount group is a group composed of a plurality of feature amounts that are lower than a threshold value and that are adjacent to each other in the image. The comparison unit 334 counts the number of pixels from the region occupied by the feature amount group and compares it with a threshold value. The threshold value at this time is equal to or less than the number of pixels corresponding to a size that does not exist as a blood vessel. This threshold value may be changeable via the input unit 35.

The sound ray setting unit 335 extracts sound rays that are below the threshold value from the comparison result between the feature value and the threshold value by the comparison unit 334. Then, from the comparison result between the number of pixels and the threshold value by the comparison unit 334, the sound ray that passes through the region (feature amount group) where the pixel number is less than the threshold value is excluded from the setting target sound rays. In addition, in the same sound ray, the sound ray setting unit 335 gives priority to a portion where the number of pixels is equal to or greater than the threshold when including both a portion where the number of pixels is less than the threshold and a portion where the number of pixels is equal to or greater than the threshold. This sound ray is left without being excluded from the Doppler scanning execution sound ray. The sound ray setting unit 335 extracts sound rays at both ends in the ultrasonic scanning direction among the sound rays remaining after the exclusion, and the extracted sound rays and the sound rays in the region sandwiched by the extracted sound rays. Is set to the Doppler scanning execution sound line. In the example shown in FIG. 13, sound ray SR _C, and SR _D, and a sound ray in a region sandwiched by a sound ray SR _C and the sound ray SR _D, it is set in the Doppler scan run sound ray.

  In the second embodiment, the computing unit 33 calculates a feature value from the result of frequency analysis, compares the feature value with a preset threshold value, and determines a sound ray including a feature value that is less than the threshold value. In addition to extracting, based on the number of pixels in the feature group, the sound lines in the area where Doppler scanning is unnecessary are excluded from the extracted sound lines, and the remaining sound lines after the exclusion are set as sound lines for Doppler scanning I tried to do it. In the second embodiment, as compared with the first embodiment described above, the Doppler scan is performed only for the blood vessel and the region including the same level of tissue as the blood vessel, and the tumor and the blood vessel are distinguished. Get the data. According to the second embodiment, compared with the first embodiment, an ultrasonic image capable of distinguishing a blood vessel and a tumor can be generated while further suppressing a decrease in the frame rate. The surgeon can easily recognize a tumor and a blood vessel from the image generated according to the second embodiment and perform an appropriate diagnosis.

  In the above-described second embodiment, if it is possible to perform Doppler scanning at only a part of the depth of one sound ray, the sound ray has a portion where the number of pixels falls below the threshold and the number of pixels. May include both a portion having a threshold value equal to or greater than a threshold value, and a Doppler scanning execution sound ray excluding only a portion where the number of pixels is less than the threshold value may be set.

  So far, the embodiment for carrying out the present invention has been described, but the present invention should not be limited only by the embodiment described above. In the first and second embodiments described above, it has been described that a color is not given to a region where blood flow is detected regardless of the feature amount, but a color different from the color used as the feature amount image is given. May be. If visual information is superimposed so that the tumor and the blood vessel can be visually distinguished, the color may be set without being colorless.

  In the first and second embodiments described above, when a plurality of feature amount groups (regions in which the number of pixels is greater than or equal to the threshold value) include different sound rays and are independent from each other, the Doppler scanning execution sound rays are independent from each other. Each sound ray in a plurality of independent regions is set as a Doppler scanning execution sound ray according to the feature amount group.

  In the first and second embodiments described above, visual information may be given by calculating a feature amount for the entire image, or visual information may be given by calculating a feature amount for a set region of interest. Good.

  In the first and second embodiments, the ultrasonic endoscope 2 having an optical system such as a light guide has been described as an ultrasonic probe. However, the present invention is not limited to the ultrasonic endoscope 2, and the imaging optical system and An ultrasonic probe that does not have an image sensor may be used. Furthermore, a thin ultrasonic miniature probe without an optical system may be applied as the ultrasonic probe. Ultrasonic miniature probes are usually inserted into the biliary tract, bile duct, pancreatic duct, trachea, bronchi, urethra, ureter, and used to observe surrounding organs (pancreas, lung, prostate, bladder, lymph nodes, etc.).

  Further, as the ultrasonic probe, an external ultrasonic probe that irradiates ultrasonic waves from the body surface of the subject may be applied. The extracorporeal ultrasonic probe is usually used in direct contact with the body surface when observing an abdominal organ (liver, gallbladder, bladder), breast (particularly mammary gland), and thyroid gland.

  The ultrasonic transducer may be a linear transducer, a radial transducer, or a convex transducer. When the ultrasonic transducer is a linear transducer, the scanning area is rectangular (rectangular, square), and when the ultrasonic transducer is a radial or convex transducer, the scanning area is fan-shaped or annular. Eggplant. In addition, the ultrasonic endoscope may be one that mechanically scans the ultrasonic transducer, or a plurality of elements are arranged in an array as the ultrasonic transducer, and the elements involved in transmission and reception are switched electronically. Alternatively, electronic scanning may be performed by delaying transmission / reception of each element.

  As described above, the present invention can include various embodiments without departing from the technical idea described in the claims.

DESCRIPTION OF SYMBOLS 1 Ultrasonic observation system 2 Ultrasound endoscope 3 Ultrasound observation apparatus 4 Display apparatus 21 Ultrasonic transducer 31 Transmission / reception part 32 Signal processing part 33 Calculation part 34 Image processing part 35 Input part 36 Control part 37 Storage part 331 Amplification correction Unit 332 frequency analysis unit 333 feature amount calculation unit 333a approximation unit 333b attenuation correction unit 334 comparison unit 335 sound ray setting unit 336 blood flow detection unit 337 display specification setting unit 341 B-mode image data generation unit 342 feature amount image data generation unit 371 Display specification information storage unit C ₁ frequency spectrum

Claims (6)

Ultrasonic observation that generates ultrasonic image data based on an ultrasonic signal acquired by an ultrasonic probe including an ultrasonic transducer that transmits ultrasonic waves to an observation target and receives ultrasonic waves reflected by the observation target A device,
A frequency analyzer that calculates a plurality of frequency spectra by analyzing a frequency of a signal generated based on the ultrasonic signal;
A feature amount calculation unit for calculating a frequency feature amount based on the frequency spectrum calculated by the frequency analysis unit;
A comparison unit that compares the frequency feature quantity with a first threshold value that is preset for the frequency feature quantity;
Based on the comparison result by the comparison unit, a sound ray setting unit for setting a sound ray for performing Doppler scanning;
A feature amount image data generation unit that generates feature amount image data indicating the frequency feature amount based on a detection result of blood flow by the Doppler scanning;
An ultrasonic observation apparatus comprising: The feature amount image data generation unit generates the feature amount image data having a display specification different from a display specification of the region where the blood flow is not detected, in the region where the blood flow is detected. The ultrasonic observation apparatus according to claim 1. The sound ray setting unit is configured such that the number of pixels corresponding to a feature amount group including frequency feature amounts whose positions are adjacent to each other in the feature amount image data is greater than a second threshold set in advance with respect to the number of pixels. The ultrasonic observation apparatus according to claim 1, wherein, when small, a sound ray including a region corresponding to the feature amount group is excluded from a sound ray that performs the Doppler scan. The ultrasonic observation apparatus according to claim 1, wherein the feature amount image data generation unit generates superimposed image data in which the feature amount image data is superimposed on the ultrasound image data. Ultrasonic observation that generates ultrasonic image data based on an ultrasonic signal acquired by an ultrasonic probe including an ultrasonic transducer that transmits ultrasonic waves to an observation target and receives ultrasonic waves reflected by the observation target A method of operating the device, comprising:
A frequency analysis step in which a frequency analysis unit calculates a plurality of frequency spectra by analyzing a frequency of a signal generated based on the ultrasonic signal;
A feature amount calculating unit that calculates a frequency feature amount based on the frequency spectrum calculated in the frequency analysis step; and
A comparison step in which the comparison unit compares the frequency feature quantity with a first threshold value preset for the frequency feature quantity;
A sound ray setting unit sets a sound ray for performing Doppler scanning based on the comparison result of the comparison step; and
A feature amount image data generating unit that generates feature amount image data indicating the frequency feature amount based on a blood flow detection result by the Doppler scanning;
A method for operating an ultrasonic observation apparatus, comprising: Ultrasonic observation that generates ultrasonic image data based on an ultrasonic signal acquired by an ultrasonic probe including an ultrasonic transducer that transmits ultrasonic waves to an observation target and receives ultrasonic waves reflected by the observation target An operating program for the device,
A frequency analysis unit that calculates a plurality of frequency spectra by analyzing a frequency of a signal generated based on the ultrasonic signal; and
A feature amount calculation unit that calculates a frequency feature amount based on the frequency spectrum calculated in the frequency analysis procedure; and
A comparison unit in which the comparison unit compares the frequency feature quantity with a first threshold value preset for the frequency feature quantity;
A sound ray setting unit, based on the comparison result of the comparison procedure, a sound ray setting procedure for setting a sound ray for performing Doppler scanning;
A feature amount image data generation unit for generating feature amount image data indicating the frequency feature amount based on a blood flow detection result by the Doppler scanning;
Is executed by the ultrasonic observation apparatus. A program for operating the ultrasonic observation apparatus.

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