JP2008073417A - Ultrasonic diagnostic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To further improve accuracy and reliability of tissue differentiation by presenting an elastic image and compression information corresponding to the elastic image with good accuracy. <P>SOLUTION: This ultrasonic diagnostic device includes: a means for sequentially obtaining elastic information related to the hardness of tissue in a plurality of measuring points of a tomographic region of a subject based upon the ultrasonic tomographic data measured in the process where pressure applied to the tissue of the subject changes; a smoothing means for smoothing elastic information pieces different in acquisition time; and a means for generating an elastic image based on the smoothed elastic information and displaying the same, wherein the smoothing means performs smoothing between the elastic information pieces acquired at the time t, (t-9), (t-54), (t-63) when the compression information related to the pressure applied to the tissue of the subject is in the equal state. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to an ultrasonic diagnostic apparatus, and specifically provides an elastic image representing the hardness or softness of a tissue of a subject and compressed information corresponding thereto to a user with high accuracy, so that discrimination in diagnosis is possible. The present invention relates to an ultrasonic diagnostic apparatus that can be improved.

  In the conventional ultrasonic diagnostic apparatus, as shown in FIGS. 2A to 2C, the probe 2 is applied to the target tissue of the subject and a certain stress is applied to cause a distortion of about 5% to 20%. While generating a slight strain change of about 0.2% to 1% in the generated state, elasticity information such as strain and elastic modulus representing the hardness or softness of the tissue is calculated. Then, in accordance with the elasticity information, for example, an elasticity image with gradation according to hue and luminance is generated and displayed. The examiner recognizes the elasticity information of the tissue from this elasticity image and discriminates between the benign and malignant of the tissue.

  Here, as described in Non-Patent Document 1, the elasticity of tissue generally has a non-linear characteristic and has a stress-strain relationship as shown in FIG. Since the elastic modulus is given by the slope of this characteristic curve, the elastic modulus changes depending on the absolute compression state (strain ε, pressure (stress) σ). Further, as shown in the same document, since the degree of this non-linearity varies from tissue to tissue, the magnitude relationship between the elasticity of breast cancer and fibrous tissue is switched depending on whether the strain condition is 5% or 20%. In order to perform benign / malignant discrimination with high accuracy, as shown in FIG. 4, it is necessary to evaluate with reference to an absolute compression state.

  By the way, when generating an elastic image, for example, as described in Patent Document 1, smoothing such as persistence processing is performed between elastic information calculated in the past, that is, at different acquisition times, and noise components are generated. It is known to generate an elastic image having a high S / N ratio with the image removed.

US Pat. No. 6,558,324 Krouskop T, et al: Elastic Moduli of Breast and Prostate Tissues Under Compression.Ultrasonic Imaging 20: 260-274, 1998.

  However, in an elastic image generated by using the smoothing process described in Patent Document 1, there is a case where the tissue cannot be distinguished accurately.

  That is, as described above, the biological tissue shows a non-linear response to compression, and the hardness changes according to the degree of compression, so when distinguishing the tissue, the hardness of the tissue that appears in the elastic image, It is necessary to evaluate in association with the compression state when the elastic image is obtained. However, in the technique of Patent Document 1, since such a fact is not taken into consideration, for example, smoothing processing is performed between past elastic information obtained under a compressed state different from the compressed state at the current time. An elastic image that is not strictly correlated with the compression state at the current time is generated.

  Furthermore, since this elastic image becomes an image depending on the state of change in the compression state up to the compression state at the current time, deterministic diagnosis may be hindered.

  An object of the present invention is to provide an elastic image and compressed information corresponding to the elastic image with high accuracy to further improve the accuracy or reliability of tissue discrimination.

  In order to solve the above-mentioned problem, a first aspect of the ultrasonic diagnostic apparatus of the present invention is based on ultrasonic tomographic data measured in the process of changing the pressure applied to the tissue of the subject, Means for sequentially obtaining elasticity information at measurement points, smoothing processing means for smoothing elasticity information at different acquisition times, and means for generating and displaying an elasticity image based on the smoothed elasticity information. The compression information correlated with the pressure applied to the tissue of the subject at each acquisition time of the elasticity information to be smoothed is smoothed and displayed together with the elasticity image.

  That is, in this aspect, the elasticity image based on the smoothed elasticity information is displayed, and the compression information at the respective acquisition times of the elasticity information that is the object of the smoothing is also smoothed and displayed. Therefore, it is possible to provide compressed information that correlates with this elastic image with high accuracy while providing an elastic image with a high S / N ratio from which noise components have been removed. As a result, the accuracy or reliability of tissue discrimination can be further improved.

  In this case, it is desirable to have a means for setting the region of interest in the elastic image, and to make the measurement point in the set region of interest follow the tissue of the subject that is displaced according to a change in pressure.

  In other words, since the tissue of the subject is displaced according to the change in applied pressure, when the region of interest is set in the tissue to be identified that is the region of interest, for example, the region to be identified in the region of interest due to a change in the compression state. As a result of the transition of different surrounding tissues and smoothing processing by mixing the elasticity information of the discrimination target tissue and the surrounding tissues, there is a possibility that the spatial resolution of the elastic image is deteriorated. However, according to this, since the measurement point in the region of interest is made to follow the change in the tissue of the subject, the elasticity information of the same identification target tissue is always measured, and smoothing processing is performed between the elasticity information. Therefore, it is possible to suppress the deterioration of the spatial resolution of the elastic image.

  In addition, the second aspect of the ultrasonic diagnostic apparatus of the present invention is based on the ultrasonic tomographic data measured in the process in which the pressure applied to the tissue of the subject changes, and the elasticity at a plurality of measurement points of the tomographic site of the subject. Smoothing processing means comprising: means for sequentially obtaining information; smoothing processing means for smoothing elastic information having different acquisition times; and means for generating and displaying an elastic image based on the smoothed elastic information. Is characterized in that smoothing is performed between elastic information acquired in a state where compression information correlated with pressure applied to the tissue of the subject is equivalent.

  That is, in this aspect, smoothing is performed only on the elastic information obtained in the same compressed information state, that is, in the same compressed state, and an elastic image based on the smoothed elastic information is displayed. Therefore, the compressed information displayed at the same time when the elastic image is displayed is accurately correlated with the elastic information such as the hardness of the tissue appearing in the elastic image without performing the smoothing as in the first aspect described above. Will be. As a result, the accuracy or reliability of tissue discrimination can be further improved.

  In this case, it is desirable that the smoothing processing means performs the smoothing process only between the elastic information acquired when the compression information is within the set range.

  According to this, instead of performing the smoothing process on all measured elasticity information, the elasticity information measured when the compression information is within the set range, that is, when the reference compression condition necessary for discrimination is satisfied. Since the smoothing process is performed only in the case where only the elastic information whose compression state is within the set range needs to be ensured, the required memory amount can be saved. In addition, the setting range of the compression information can be arbitrarily selected by the user.

  Moreover, the following aspects can be suitably employ | adopted in the ultrasonic diagnostic apparatus of a 1st aspect and a 2nd aspect. In other words, as the smoothing process, any one of an addition average process of elasticity information and / or compression information to be smoothed, a process for obtaining a median value, or a persistence process can be appropriately employed.

  The compression information includes pressure applied to the body surface of the subject, pressure applied to the tissue of the subject, displacement of the tissue of the subject, distortion of the tissue of the subject, phase in the ECG waveform, amplitude value in the ECG waveform, or Any one of the blood flow velocities by the blood flow Doppler can be appropriately adopted.

  As the elasticity information, any one of displacement, strain, and elastic modulus of the tissue of the subject can be appropriately employed.

  ADVANTAGE OF THE INVENTION According to this invention, the compression information corresponding to an elastic image and an elastic image accurately can be provided, and the precision thru | or reliability of a tissue discrimination can be improved further.

  Hereinafter, embodiments of an ultrasonic diagnostic apparatus to which the present invention is applied will be described. In the following description, the same functional parts are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a block diagram of an ultrasonic diagnostic apparatus according to an embodiment of the present invention. As shown in FIG. 5, the ultrasonic probe 2 used in contact with the subject 1 as shown in FIG. 1 transmits a plurality of ultrasonic waves to and from the subject 1. The transducer is formed having an ultrasonic transmission / reception surface 21 in which the transducers are aligned. The probe 2 is driven by ultrasonic pulses supplied from the transmission circuit 3, and performs beam scanning mechanically or electronically. The transmission / reception control circuit 4 controls the transmission timing of ultrasonic pulses for driving the plurality of transducers of the probe 2 to form an ultrasonic beam toward the focal point set in the subject 1. ing. The transmission / reception control circuit 4 is configured to electronically scan the ultrasonic beam in the direction in which the transducers of the probe 2 are arranged.

  On the other hand, the probe 2 receives a reflected echo signal generated from the subject 1 and outputs it to the receiving circuit 5. In accordance with the timing signal input from the transmission / reception control circuit 4, the reception circuit 5 takes in the reflected echo signal and performs reception processing such as amplification. The reflected echo signal received and processed by the receiving circuit 5 controls the phase of the reflected echo signal received by the plurality of transducers in the phasing and adding circuit 6, and receives an ultrasonic wave reception beam at one or more convergence points. Form. A reflected echo signal (hereinafter referred to as ultrasonic tomographic data) subjected to phasing addition in the phasing addition circuit 6 is input to the signal processing unit 7 and signals such as gain correction, log compression, detection, contour enhancement, filter processing, and the like. Processing is done. Note that the radio frequency (RF) signal of the ultrasonic tomographic data generated in the phasing addition circuit 6 may be a complex demodulated I and Q signal. In this manner, the probe 2 scans the ultrasonic beam in the body of the subject 1 in a certain direction, and obtains ultrasonic tomographic data corresponding to one tomographic image.

  The ultrasonic tomographic data processed by the signal processing unit 7 is guided to the black and white scan converter 8 where it is converted into a digital signal and also converted into two-dimensional tomographic image data corresponding to the scanning plane of the ultrasonic beam. . In other words, the monochrome scan converter 8 acquires the RF signal frame data in the subject 1 including the moving tissue in an ultrasonic cycle, and converts the frame data into an image for display in order to read out in synchronization with the television. An A / D converter that converts a reflected echo signal from the signal processing unit 7 into a digital signal, and a tomogram digitized by the A / D converter. It comprises a plurality of frame memories for storing image data in time series and a controller for controlling these operations. The signal processing unit 7 and the monochrome scan converter 8 constitute a tomographic image reconstruction unit. The tomographic image data output from the black and white scan converter 8 is supplied to the image display 10 via the switching addition unit 9 so that the tomographic image is displayed.

  The image display 10 displays time-series tomographic image data obtained by the black-and-white scan converter 8, and includes a D / A converter that converts image data input via the switching addition unit 9 into an analog signal, It comprises a color television monitor that receives an analog video signal from the D / A converter and displays it as an image.

  On the other hand, the ultrasonic tomographic data output from the phasing addition circuit 6 is guided to the RF signal frame data selection unit 11. The RF signal frame data selection unit 11 selects an RF signal group corresponding to the scanning plane (tomographic plane) of the ultrasonic beam as a frame data and stores it in a memory or the like. The displacement calculation unit 12 sequentially captures a plurality of pairs of frame data with different acquisition times stored in the RF signal frame data selection unit 11, and based on the captured pair of frame data, displacement vectors of a plurality of measurement points on the tomographic plane. And is output to the strain / elastic modulus calculation unit 13 and the smoothing processing unit 14 as displacement frame data.

  The strain / elastic modulus calculation unit 13 obtains strains at a plurality of measurement points on the tomographic plane based on the input displacement frame data, and outputs them to the smoothing processing unit 14 as strain frame data. Further, the strain / elastic modulus calculation unit 13 takes in pressure measurement data applied to the subject from the pressure measurement unit 19 to obtain a stress distribution of each part of the subject, and generates elasticity from the previously obtained strain frame data and the stress distribution. The rate is obtained and output to the smoothing processing unit 14 as elastic frame data. As shown in FIG. 5B, the pressure measurement unit 19 takes in an output signal of the pressure sensor 23 provided on the compression plate 22 attached to the ultrasonic transmission / reception surface 21, and the body surface of the subject 1 The pressure applied is measured, and the measured pressure data is sent to the strain / elastic modulus calculation unit 13 and the smoothing processing unit 14. As shown in FIG. 5C, the pressure measurement is performed based on the displacement frame data of the reference deformable body 24 using the probe 2 having the reference deformable body 24 mounted on the front surface of the compression plate 22. It is also possible to measure the pressure applied to the body surface. These pressure measurement methods are described in JP-A-2005-13283 or JP-A-2005-66041.

  The smoothing processing unit 14, which is a characteristic part of the present embodiment, will be described in detail later, displacement frame data input from the displacement calculation unit 12, strain frame data input from the strain / elastic modulus calculation unit 13, A smoothing process is performed based on any of the elastic frame data and the pressure measurement data input from the pressure measurement unit 19, and the result is output to the elasticity data processing unit 15.

  The elastic data processing unit 15 performs various image processing such as smoothing processing and contrast optimization processing in the coordinate plane on the elastic frame data input from the smoothing processing unit 14 and sends the processed data to the color scan converter 16. It has become.

  The color scan converter 16 converts the elastic frame data output from the elastic data processing unit 15 to generate a color elastic image and displays it on the image display 10 via the switching addition unit 9. In other words, the color scan converter 16 is configured such that red, which is gradation (for example, 256 gradations) into an elastic image, based on a range of preset upper and lower limits of elasticity (displacement, strain, or elastic modulus). Assign a hue code such as green or blue. For example, a hard region where the elastic modulus of the elastic frame data is measured to be large is converted to a blue code, and conversely, a soft region where the elastic modulus is measured to be small is converted to a red code. A black and white scan converter can be used in place of the color scan converter 16. In this case, the distribution of the elastic modulus can be expressed by brightening the brightness of the hard region measured with a large elastic modulus, and conversely decreasing the luminance of the soft region measured with a small elastic modulus.

  The switching addition unit 9 receives black and white tomographic image data output from the black and white scan converter 8 and color elastic image data output from the color scan converter 16 and switches both images to switch either one of them. It has a function of displaying, a function of adding and synthesizing one of the two images in a semi-transparent manner and displaying the images on the image display 10 and a function of displaying both the images side by side. Further, the cine memory unit 18 stores the image data output from the switching addition unit 9 in the memory, and calls the past image data and displays it on the image display 10 in accordance with a command from the control interface unit 17. Yes. Furthermore, the selected image data can be transferred to a recording medium such as an MO.

  Next, the basic operation of this embodiment configured as described above will be described. First, while changing the pressure applied to the subject 1 by the probe 2, the subject 1 is scanned with an ultrasonic beam and the reflected echo signal from the scanning surface is continuously received. Based on the RF signal output from the phasing addition circuit 6, the tomographic image is reconstructed by the signal processing unit 7 and the black and white scan converter 8 and displayed on the image display 10 via the switching adder 9.

  On the other hand, the RF signal frame data selection unit 11 captures the RF signal in the process of changing the pressure applied to the subject 1 and repeatedly acquires the frame data in synchronization with the frame rate, and stores it in the built-in frame memory. Save in sequence order. Then, a plurality of pairs of frame data are successively selected and output to the displacement calculation unit 12 with the frame data including a pair of reflected echo signals having different acquisition times as a unit. The displacement calculation unit 12 performs one-dimensional or two-dimensional correlation processing on the selected pair of frame data, measures the displacement of each measurement point on the scanning plane, and generates displacement frame data. As a method for detecting the displacement vector, for example, an image is divided into blocks of, for example, N × N pixels, and a block closest to the block of interest in the current frame is searched from the previous frame, and based on this. Thus, a known block matching method for obtaining the displacement of the measurement point can be applied. Further, the displacement can be calculated by calculating the autocorrelation in the same region of the pair of RF signal frame data.

  The displacement frame data obtained by the displacement calculation unit 12 is input to the strain / elastic modulus calculation unit 13, and the predetermined elasticity information such as strain and elastic modulus at each measurement point is calculated to obtain necessary elasticity information. The frame data is output to the smoothing processing unit 14. The distortion calculation is calculated by spatially differentiating the displacement as is well known.

  The displacement frame data obtained by the displacement calculation unit 12 is also input to the smoothing processing unit 14. Then, as will be described in each embodiment described later, the smoothing processing unit 14 obtains compression information for the subject 1 such as pressure information output from the pressure measurement unit 19 and elasticity information of the tissue of the subject 1. And smoothing between a plurality of elastic information. The smoothed elasticity information is input to the color scan converter 16 via the elasticity data processing unit 15 to generate an elasticity image and displayed on the image display 10.

  Hereinafter, the smoothing processing unit 14 which is a characteristic part of the ultrasonic diagnostic apparatus according to the present embodiment will be described based on specific examples.

  FIG. 6 is an example in which the relationship between the time when the elastic frame data obtained in the process of changing the pressure applied to the subject 1 by the probe 2 and the compression state at that time is shown by a black circle plot. .

  When the elastic frame data is acquired as shown in FIG. 6, with the conventional smoothing technique, for example, if the smoothing process is performed between the past four frames, the white outline of the figure is obtained at the current time t. The elastic frame data measured in the past compression state indicated by the triangle is smoothed with the elastic frame data obtained at the current time t, and an elastic image is generated. Then, in order to receive the contribution of the elastic frame data obtained in the compression state stronger than the compression state at the current time, the elasticity information indicating the hardness or softness of the tissue appearing in this elastic image and the compression state at the current time Is not strictly correlated.

  Further, for example, at time (t-9), which is the same compression state as time t, smoothing processing is performed with the elastic frame data measured in the past compression state indicated by the white square in the figure, and an elastic image is obtained. Is generated. Then, unlike the case of time t, the elasticity information at time (t-9) receives contribution of elastic frame data obtained in a compressed state weaker than time (t-9). That is, the elasticity information measured at an arbitrary time changes depending on the history of the change in the compression state up to the measurement time. Therefore, the relationship between the information on the absolute compression state and the elasticity information at an arbitrary time is not highly accurate, and there are cases where the diagnosis cannot be made deterministically.

  In contrast, the present embodiment attempts to obtain a relationship between absolute compression state information and elasticity information with high accuracy. For example, as a smoothing process, At the same time, the compression information at each acquisition time of the elastic frame data to be smoothed is also smoothed.

  That is, the smoothing processing unit 14 of the present embodiment first smoothes, for example, the last four elastic frame data and pressure information in addition to the elastic frame data as elastic information and the pressure information as compression information at the current time t. The memory is provided in the processing unit 14. Each of the pressure information and the elastic frame data secured in the memory is defined as follows.

Pressure information: P (t), P (t-1), P (t-2), P (t-3), P (t-4)
Elastic frame data: Ei, j (t), Ei, j (t-1), Ei, j (t-2), Ei, j (t-3), Ei, j (t-4) (i, j Is the coordinates of the measurement point)
Next, an averaging process is performed as a smoothing process for each of the pressure information and the elastic frame data. If the pressure information after the smoothing process is defined as P ′ (t) and the elastic information after the smoothing process is defined as E′i, j (t) (i, j are the coordinates of the measurement point), P ′ (t) and E′i, j (t) is calculated as follows.
(Formula 1)
P ′ (t) = {P (t) + P (t−1) + P (t−2) + P (t−3) + P (t−4)} / 5
(Formula 2)
E'i, j (t) = {Ei, j (t) + Ei, j (t-1) + Ei, j (t-2) + Ei, j (t-3) + Ei, j (t- 4)} / 5
Then, the pressure information P ′ (t) after the smoothing process and the elasticity information E′i, j (t) after the smoothing process are input to the elasticity data processing unit 15, and the smoothing process in the coordinate plane as described above. Various image processing such as contrast optimization processing is performed. Further, processing is performed by the color scan converter 16 or the like, and an elastic image is generated and displayed on the image display 10.

  At this time, if a region of interest (hereinafter referred to as ROI) is set on the elastic image, a representative value such as an average value of the elastic information E′i, j (t) after smoothing processing at the measurement points in the ROI < E′i, j (t)> is calculated. As shown in FIG. 7, in addition to the elasticity image, the pressure information P ′ (t) after the smoothing process and the elasticity information representative value <E′i, j (t)> after the smoothing process The relationship P ′ (t) − <E′i, j (t)> is plotted as a graph.

  Here, on this graph, for example, it is possible to change the hue or shape of the plot at the current time so that the state of the pressure information and elasticity information at the current time can be grasped at a glance. is there.

It is also possible to automatically change the measurement point in the ROI set in the elastic image by following the tissue of the subject that is displaced according to the change in the compression state. That is, by using the information on the displacement of the measurement point in the ROI calculated by the displacement calculation unit 12, it is possible to track the displacement of the tissue to be identified. As a result, the coordinate area occupied by the ROI in the compression process moves relative to the coordinate system of the elastic image as shown in FIG. 8, but if the displacement information is used, as shown in the lower part of FIG. It is possible to track and follow the coordinates of the movement destination of the same tissue region, that is, P _-4 , P _-3 , P _-2 , P _-1 , P. By using this method, the elastic information E′i, j (t) after the smoothing process is obtained as follows.
(Formula 3)
E′i, j (t) = {Ei, j (t) + Ei ₋₁ , j ₋₁ (t−1) + Ei ₋₂ , j ₋₂ (t−2) + Ei ₋₃ , j ₋₃ (T-3) + Ei- ₄ , j- ₄ (t-4)} / 5
Then, the smoothing process can be performed between the elasticity information of the same tissue, and the elasticity information of the discrimination target tissue and the surrounding tissue is not mixed, and the deterioration of the spatial resolution of the elasticity image can be suppressed.

  Further, in this embodiment, an example in which elastic frame data of elastic modulus is smoothed as elastic information has been described, but it is also possible to use displacement frame data and strain frame data in addition to the elastic modulus. It is also possible to use information about elasticity such as viscosity, stress, Poisson's ratio, strain ratio between tissues of interest using means. In the following embodiments, the elastic frame data of elastic modulus will be described as a representative, but the present invention is not limited to this.

  In addition, the above processing can be performed in real time at an arbitrary time t. By displaying a graph of the relationship between the compression state and the elasticity information and an elastic image, the elasticity response to the compression operation can be displayed to the examiner in real time. Can be provided. Furthermore, the present invention can be applied to various living tissues such as a mammary gland region, prostate, and thyroid gland.

  According to the present embodiment, the smoothing process is performed between the elastic frame data, and at the same time, the compression information at each acquisition time of the elastic frame data to be smoothed is also smoothed to contribute to the past compression state. By reflecting, the determinism of the relationship between the compression state information and the elasticity information can be improved.

  Furthermore, after tracking the measurement points of the tissue to be identified and converting the coordinates, the elasticity caused by mixing the elasticity information of the tissue to be identified and the surrounding tissue is processed by adding the elasticity information. Degradation of the spatial resolution of the image can be avoided.

  In this embodiment, an attempt is made to measure the elasticity information at the current time with high accuracy using the elasticity information measured in an equivalent compressed state. When elastic frame data is acquired as shown in FIG. 6 as in the first embodiment, the smoothing processing unit 14 first secures, for example, the past 73 pressure information and elastic frame data measurement results in the memory. To do. Data secured in memory is defined as follows.

Pressure information: P (t-1), P (t-2), P (t-3), ..., P (t-73)
Elastic frame data: Ei, j (t-1), Ei, j (t-2), Ei, j (t-3), ..., Ei, j (t-73)
Next, the smoothing processing unit 14 searches for past pressure information that realizes a compression state equivalent to the pressure information P (t) at the current time t. In the case of FIG. 6, the times t-9, t-22, t-54, and t-63 are selected as corresponding.

Then, smoothing processing is performed using the elastic frame data at the time. The elastic information E′i, j (t) after the smoothing process is calculated as follows.
(Formula 4)
E′i, j (t) = {Ei, j (t) + Ei, j (t−9) + Ei, j (t−22) + Ei, j (t−54) + Ei, j (t− 63)} / 5 (i and j are coordinates of measurement points)
Next, the pressure information P (t) and the smoothed elasticity information E′i, j (t) are input to the elasticity data processing unit 15 to perform smoothing processing, contrast optimization processing, etc. in the coordinate plane. Various image processing is performed. Further, processing is performed by the color scan converter 16 or the like, and an elastic image is generated and displayed on the image display 10.

  At this time, as in the first embodiment, in addition to the elasticity image, the relationship between the pressure information P (t) and the magnitude of the elasticity information representative value <E′i, j (t)> after the smoothing process: P ( t)-<E'i, j (t)> is plotted as a graph.

  The above processing can be performed in real time at an arbitrary time t, and by displaying a graph of the relationship between the compression state and the elasticity information and an elasticity image, the elasticity response to the compression operation is provided to the examiner in real time. be able to.

In the present embodiment, the pressure information P (t) acquired at the current time as the compression information is applied as it is. However, according to the method of the first embodiment, the pressure information P ′ (t) after the smoothing process is applied. You may calculate and apply as follows.
(Formula 5)
P ′ (t) = {P (t) + P (t−9) + P (t−22) + P (t−54) + P (t−63)} / 5
Further, in the present embodiment, it is shown that the same compression state is searched from the past pressure information. However, in reality, it is rare that the compression state completely matches, and it is determined that the compression state is equivalent. It is necessary to set a predetermined allowable range (compressed state range). In other words, if this range is expressed as ΔP, a past compression state that falls within the range of P (t) ± ΔP is searched for the pressure state P (t) at the current time, and elastic frame data that satisfies the condition is searched. Smoothing processing is performed between the two.

  Further, this width is not set to a constant value, but for example, within 10% of the value of P (t) at the current time, that is, P (t) ± 0.1 × P (t) is the same. You may set to the compression state range determined to be a compression state.

  Further, for example, four compression states may be retrieved from the past pressure information from the state closest to the magnitude of P (t) at the current time, and applied for smoothing processing.

  According to the present embodiment, since the smoothing process is performed only between the elastic information obtained in the same compressed state, the elastic information measured between the different compressed states is mixed as in the conventional method. Therefore, it is possible to prevent the accuracy of the correlation between the current compressed state and the elastic image from being lowered.

  Also, as shown in FIG. 9, since the addition averaging process is performed with the elasticity information obtained in the same compression state, the coordinate areas occupied by the interested part which is the tissue to be differentiated are equal, and the boundary part of the interested part is It is possible to prevent deterioration of the spatial resolution of the elastic image without bleeding.

  In the first and second embodiments, for the purpose of realizing a high S / N by using the elasticity information of a plurality of frames, the smoothing process is performed by particularly searching for 4 frames from the past elasticity frame data. Although the example which performs this was shown, it cannot be overemphasized that the past number of frames added to smoothing processing is not restricted to four frames.

In the first and second embodiments, the arithmetic mean is calculated as the smoothing process. However, as in the present embodiment, for example, between the past elastic frame data and the current elastic frame data, The value may be obtained to obtain elastic frame data after the current time smoothing process. That is, for example, the elastic information E′i, j (t) after the smoothing process in the case of the second embodiment is calculated as follows.
(Formula 6)
E′i, j (t) = median {Ei, j (t) + Ei, j (t−9) + Ei, j (t−22) + Ei, j (t−54) + Ei, j (t -63)}
Here, median {} represents processing for obtaining the median of the population of numerical values in {}.

  According to this method, it is possible to effectively remove noise in the elastic frame data at the time when inappropriate compression such as instantaneous camera shake is applied.

Further, as the smoothing process, for example, the so-called persistence process, in which the information after the smoothing process in the past of one frame and the current information are combined at a predetermined ratio C (C <1.0), pressure information, and You may give to both elasticity information. The pressure information and elasticity information after the persistence processing are calculated as follows.
(Formula 7)
P ′ (t) = (1−C) × P (t) + C × P ′ (t−1)
(Formula 8)
E′i, j (t) = (1−C) × Ei, j (t) + C × E′i, j (t−1)
In addition, it is possible to adopt a method for realizing a high S / N by performing the same statistical processing on both a plurality of past elasticity information and pressure information.

  In the first to third embodiments, it has been described that the pressure information applied to the contact surface between the probe and the living body skin is used as an index of the compression state. However, in this embodiment, the compression information other than the pressure information is used. The example which solves a subject is shown.

  For example, as shown in FIG. 10, information on stress σ in ROI may be applied as compression information to evaluate the relationship with elasticity information. There are various methods for evaluating the stress σ, and there is a method for estimating the stress distribution propagating inside the living body based on the pressure information applied to the surface and the information on the strain generated inside the living body. The stress information may be acquired according to such a known method.

  Moreover, you may employ | adopt the well-known method of measuring stress with a pressure sensorless method. Further, it is not always necessary to obtain the stress information as the stress dimension (kPa), and the absolute compression state may be evaluated as an index correlated with the stress.

  In addition, distortion and displacement information can be used as the compression information. That is, using the image on the apparatus such as a B-mode image or elasticity image that is a tomographic image, the ROI is set in the region of interest, and the process of resetting the distortion on the apparatus in the state of zero compression is performed from the apparatus interface. input. Compression is started from the reset state, and minute distortion changes in the ROI are integrated. That is, the integrated value of the slight strain change is expressed by ε (t) = ΣΔε (t), and the calculated integrated value is plotted as an elastic image and the relationship between the elastic information and the strain as in the above-described embodiment. Can be displayed. Alternatively, a plurality of regions of interest may be set and their characteristic curves may be plotted and displayed simultaneously.

  Here, an example in which the integrated value of the distortion is obtained and plotted is shown, but the same processing can be performed using the displacement information. That is, the displacement information output from the displacement calculation unit 12 in FIG. 1 can be used as the compression information by obtaining the accumulated displacement from the zero compression state, as in the case of the distortion described above.

Further, the displacement information may be obtained from a magnetic sensor or the like attached to the probe, for example, RVS (Real Time Virtual Sonography).
This method is actually realized. Moreover, you may comprise using a laser displacement meter etc.

  The problem of the present invention is also solved by evaluating the absolute compression state based on information other than the pressure information as in the present embodiment, according to the same method as the embodiment described with the above pressure information as a representative. be able to.

  Recently, it has become possible to evaluate the elasticity of the tissue around the blood vessel, such as the degree of arteriosclerosis, the hardness of plaque in the blood vessel, and the hardness of deep vein thrombosis. Attempts to measure the elasticity information of the tissue by using it have become mainstream. However, for example, since the blood vessel wall is a thin tissue of about 1 mm, the spatial resolution of the elastic image is very important when evaluating elasticity information. For example, the evaluation of the carotid artery as shown in FIG. Then, since the blood vessel expands and contracts due to the pulsation, the coordinates of the blood vessel wall greatly change in the elastic image.

  Therefore, when smoothing processing such as past elasticity information and addition averaging processing is performed by the conventional method, elasticity information of different tissues such as blood vessel and muscle elasticity information is added to the blood vessel wall elasticity information, as described above. Are mixed together, the evaluation accuracy of the elasticity information is extremely deteriorated.

  Therefore, the present embodiment attempts to use ECG information as information that replaces the compressed information in the above-described embodiments.

  FIG. 12 is a diagram showing a typical ECG waveform. The movement amount and direction of the blood vessel wall are synchronized with the pulsation, and it can be said that at the same phase of the ECG waveform, the blood vessel is at the same position and at the same compression state. Therefore, in this embodiment, smoothing processing is performed between elastic information obtained at the same phase of the ECG waveform.

  That is, it is assumed that the elasticity information Ei, j (t) at the current time t is measured at the rise of the T wave of the ECG waveform. At this time, the elasticity information measured in the same phase of ECG is searched from past elasticity frame data. In the figure, the time ta, tb is recognized as the same phase of the ECG, and the elastic information Ei, j (ta), Ei, j (tb) obtained at that time is obtained.

Next, for example, if the averaging process between the past two frames is set as the smoothing process, the elasticity information E′i, j (t) after the smoothing process at the current time is set as follows: Calculate to
(Formula 9)
E′i, j (t) = {Ei, j (t) + Ei, j (ta) + Ei, j (tb)} / 3
The processing after the elasticity information E′i, j (t) is obtained is processed in the same manner as in the above-described embodiment, and an elasticity image or the like is displayed on the image display 10.

  In the present embodiment, an example is shown in which the elasticity information measured in the same phase of the ECG is searched and the smoothing process is performed between the elasticity information, but the elasticity information that exactly matches the phase is not selected. The stabilization processing may be performed between elastic information having the same ECG amplitude. In addition, when an ECG waveform is used, it is possible to trigger data acquisition timing with an ECG trigger, and thereby control to positively acquire elasticity information in the same phase.

  Further, instead of using the ECG waveform for identifying the compressed information, it is also possible to use information on the change in blood flow velocity over time due to Doppler.

  That is, if Doppler measurement is performed simultaneously with the evaluation of elasticity, and the Doppler ROI is set inside the blood vessel as shown in FIG. 11, the time change of the blood flow velocity as shown in FIG. 13 can be obtained. If the information on the change in blood flow velocity with time is applied instead of the ECG waveform, the elasticity information measured in the same compressed state can be selected.

  In the above-described embodiment, it has been shown that smoothing processing is performed at an arbitrary time t without imposing a condition on the compression state. However, in this embodiment, a compression state serving as a diagnostic criterion is set in advance. Thus, discrimination is performed based on elasticity information under the conditions. Hereinafter, this method will be described in detail.

  For example, assume that a reference compression state as shown in FIG. 14 is set for an absolute compression state. That is, the reference compression state (AkPa to BkPa) is set. At this time, the times when the reference compression state was satisfied were (t-72), (t-69), (t-65), ..., (t-20), and were measured at these times. A smoothing process of elasticity information is applied based only on elasticity information. The elasticity information measured at the time when the reference compression state is not satisfied is not subjected to the smoothing process based on the search process for the same compression state.

  In this case, as shown in FIG. 15, the elastic image is displayed on two screens. For example, the left screen displays an elastic image constructed so as to satisfy the above-described reference compression state, and the right screen displays the current time t. The elasticity image obtained in step 1 may be displayed in real time. In this case, the left elastic image is updated only when the compression state satisfies the reference compression state. In addition, on the right screen of the real-time display, it is possible to check measurement conditions such as searching for a measurement section or adjusting the compression direction.

  In addition, after freezing the ultrasonic diagnosis, only one final image constructed to satisfy the reference compression state applied to the diagnosis may be automatically saved as a still image. Even if the state is changed, the same smoothing processing can be performed in the reference compression state after the change. In addition, for example, a display such as “diagnosis image” may be attached to the final image so that the examiner can easily recognize an image suitable for diagnosis.

  Further, the reference compression state in the present embodiment can be arbitrarily set and changed by moving the cursor on the graph by various input devices such as a keyboard, a mouse, and a touch panel.

  According to the present embodiment, only the elastic frame data measured when the reference compression state is satisfied needs to be secured, and the required memory amount can be saved.

  Moreover, in Examples 1-6, by excluding the elasticity information measured in the process in which the compression state does not change so much like the elasticity information in the specific part 30 of FIG. 14, from the object of the smoothing process, It is also possible to further improve the accuracy of the elastic information after the smoothing process.

It is a block block diagram of one Embodiment of the ultrasonic diagnosing device of this invention. It is a figure explaining an example of compression operation which applies pressure to an object tissue with an ultrasonic probe. It is a figure which shows an example of the stress-distortion diagram of a mammary gland and a fat tissue. It is a figure explaining an example which sets a standard compression state and performs organization discrimination. It is an external view which shows an example of an ultrasonic probe. It is an external view which shows an example of the ultrasonic probe provided with the compression board and the pressure sensor. It is an external view which shows an example of the ultrasonic probe provided with the reference deformation body in the compression board. It is a figure which shows an example of the graph which plotted the relationship between the time which measured the elastic frame data obtained in the process of changing the pressure applied to a subject, and the compression state at that time. It is a figure which shows the elasticity image and the graph which plotted the relationship of the magnitude | size of the compression information after a smoothing process, and the elasticity information representative value after a smoothing process. It is a figure explaining changing a measurement point automatically in accordance with the structure | tissue of the subject displaced in the process of the change of a compression state. It is a figure which shows an example which performs the addition averaging process between the elasticity information obtained by the same compression state, and prevents the boundary part of an interested part from oozing and preventing deterioration of the spatial resolution of an elastic image. It is a figure which shows an example which applies the information of stress (sigma) in ROI as compression information, and evaluates the relationship with elastic information. It is a figure which shows an example of the diagnostic image in the case of diagnosing the elastic information of the carotid artery and the plaque in a carotid artery. It is a figure which shows an example of an ECG waveform. It is a figure which shows an example of the time change of the blood flow velocity by ultrasonic Doppler. It is a figure which shows an example which presets the compression state used as a diagnostic reference, and performs discrimination by the elastic information on the conditions. It is the figure which showed an example which displays an elasticity image by 2 screens.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Subject 2 Probe 3 Transmission circuit 4 Transmission / reception control circuit 5 Reception circuit 6 Phased addition circuit 7 Signal processing part 8 Black-and-white scan converter 9 Switching addition part 10 Image display 11 RF signal frame data selection part 12 Displacement calculation part 13 Strain / elastic modulus calculation unit 14 Smoothing processing unit 15 Elastic data processing unit 16 Color scan converter 17 Control interface unit 18 Cine memory unit 19 Pressure measurement unit 21 Ultrasonic transmission / reception surface 22 Compression plate 23 Pressure sensor 24 Reference deformation body 30 Specific part

Claims (8)

Means for sequentially obtaining elasticity information at a plurality of measurement points of the tomographic site of the subject based on ultrasonic tomographic data measured in the process of changing the pressure applied to the tissue of the subject, and the elasticity information having different acquisition times Smoothing processing means for smoothing, and means for generating and displaying an elasticity image based on the smoothed elasticity information,
An ultrasonic diagnostic apparatus characterized in that compressed information correlated with pressure applied to the tissue of the subject at each acquisition time of the elasticity information to be smoothed is smoothed and displayed together with the elasticity image. A means for setting a region of interest in the elastic image, and causing the measurement point in the set region of interest to follow the tissue of the subject that is displaced according to the change in the pressure. Item 2. The ultrasonic diagnostic apparatus according to Item 1. Means for sequentially obtaining elasticity information at a plurality of measurement points of the tomographic site of the subject based on ultrasonic tomographic data measured in the process of changing the pressure applied to the tissue of the subject, and the elasticity information having different acquisition times Smoothing processing means for smoothing, and means for generating and displaying an elasticity image based on the smoothed elasticity information,
The ultrasonic diagnostic apparatus characterized in that the smoothing processing means performs smoothing between elastic information acquired in a state where compression information correlated with pressure applied to the tissue of the subject is equivalent. The smoothing process is any one of an addition averaging process of elasticity information and / or compression information to be smoothed, a process for obtaining a median value, or a persistence process. The ultrasonic diagnostic apparatus according to 3. The compression information is any one of a pressure applied to the body surface of the subject, a pressure applied to the tissue of the subject, a displacement of the tissue of the subject, or a distortion of the tissue of the subject. The ultrasonic diagnostic apparatus according to claim 1 or 3. The ultrasonic diagnostic apparatus according to claim 1, wherein the compression information is any one of a phase or an amplitude value in an ECG waveform, or a blood flow velocity caused by blood flow Doppler. The ultrasonic diagnostic apparatus according to claim 1, wherein the elasticity information is any one of displacement, strain, and elastic modulus of the tissue of the subject. The ultrasonic diagnostic apparatus according to claim 3, wherein the smoothing processing unit performs the smoothing process only between the elastic information acquired when the compression information is within a set range.

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