JP2005334196A - Ultrasonic diagnostic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To automatically optimize parameters for drawing a tissue elasticity image according to a diagnosis state without troubling operator's hands. <P>SOLUTION: This ultrasonic diagnostic equipment stepwisely changes frame rates of ultrasonic operation, finds the ratios of strain amounts in the tissue elasticity image obtained by the respective frame rates and sets a frame rate making the ratio maximum. The frame rate is set by setting the number of frame intervals and scanning period, which make the ratio of the strain amount maximum, as the parameters. Alternatively, a rejection level most suited for the ratio of the strain amount is found and set as a parameter. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ultrasonic diagnostic apparatus that obtains and displays a tomographic image of a diagnostic site in a subject using ultrasonic waves, and in particular from a set of RF signal frame data arranged in time series on the image. The present invention relates to an ultrasonic diagnostic apparatus capable of calculating strain and elastic modulus at each point and displaying them as an elastic image quantitatively indicating the hardness or softness of a living tissue.

  A conventional general ultrasonic diagnostic apparatus includes an ultrasonic transmission / reception unit for transmitting and receiving ultrasonic waves to a subject, and a tomographic image in the subject including a moving tissue using a reflected echo signal from the ultrasonic transmission / reception unit. A tomographic scanning unit that repeatedly obtains data at a predetermined cycle and an image display unit that displays time-series tomographic image data obtained by the tomographic scanning unit are provided. The structure of the living tissue inside the subject is displayed as a B-mode image, for example.

On the other hand, recently, using this ultrasonic apparatus, the elastic modulus of a living tissue at a diagnostic site is measured and displayed as an elastic modulus image. Examples of such an ultrasonic device include those described in Patent Document 1 or Patent Document 2.
JP-A-5-317313 JP 2000-60853 A

  Recently, an external force is applied artificially from the body surface of a subject with a pressurizing device or an ultrasonic probe, and ultrasonic reception of two adjacent frames (two consecutive frames) that change in time series in that state is performed. A technique has been used in which a correlation is calculated between signals, a displacement at each point is obtained, a distortion is measured by spatially differentiating the displacement, and this distortion data is imaged. In addition, a technique for imaging elastic modulus data represented by Young's modulus of living tissue based on stress distribution and strain data due to external force has become realistic. According to the elastic image created based on such strain and elastic modulus data (hereinafter referred to as elastic frame data), the hardness and softness of the living tissue can be measured and displayed.

  However, the elastic frame data imaging process by such a conventional ultrasonic diagnostic apparatus is a correlation calculation between adjacent RF signal frame data acquired in time series during a series of pressurization or decompression operations. Therefore, the amount of pressurization or decompression given in the time interval between the RF signal frame data constituting the set of these plural RF signal frame data is suitable for rendering the elastic image data. When the amount of pressurization or the amount of depressurization (generally about 1%) is not sufficiently reached, there is a problem that it is difficult to appropriately draw an elastic image based on elastic frame data.

  Therefore, the applicant of the present application is provided with an RF signal frame data selection means for selecting a set of RF signal frame data to be a reference for displacement measurement, and a frame interval between the current RF signal frame data and the past RF signal frame data. An application has been filed in which the number can be arbitrarily selected (Japanese Patent Application No. 2003-6932). As a result, the frame interval between the past and present RF signal frame data can be set to an appropriate size, and an elastic image based on the elastic frame data can be drawn appropriately.

  However, in such an ultrasonic diagnostic apparatus, the operator has to optimize the number of frame intervals as a parameter at the time of rendering the tissue elasticity image while actually depicting the tissue elasticity image, which is troublesome. Had a problem.

  The present invention has been made in view of the above-described points, and provides an ultrasonic diagnostic apparatus capable of automatically optimizing tissue elasticity image rendering parameters in accordance with a diagnosis situation without bothering an operator. The purpose is to do.

The first feature of the ultrasonic diagnostic apparatus according to the present invention is that ultrasonic transmission / reception means for transmitting and receiving ultrasonic waves to a subject and outputting reflected echo signals, and the ultrasonic transmission / reception means output from the ultrasonic transmission / reception means. A tomographic scanning unit that repeatedly acquires RF signal frame data in the subject using a reflected echo signal at a predetermined period, and a displacement from a plurality of time-series RF signal frame data groups acquired by the tomographic scanning unit. RF signal frame for selecting RF signal frame data at the present time and RF signal frame data separated by a predetermined number of frame intervals going back in the past by an arbitrary number of frames as a set of RF signal frame data to be measured Based on the data selection means and the distortion amount ratio obtained by changing the number of frame intervals step by step, the optimum frame interval Parameter setting means for setting the number, signal processing means for generating elastic image data based on a set of RF signal frame data selected by the RF signal frame data selecting means, and the elasticity generated by the signal processing means And image display means for displaying image data.
This is because the RF signal frame data selection means for selecting a set of RF signal frame data to be a reference for displacement measurement is performed by the current RF signal frame data and the adjacent RF signal frame data set, the current RF signal frame data, and the current RF signal frame data. The frame interval between the current RF signal frame data and the past RF signal frame data without fixing the number of frame intervals between the two, as in the case of a set with the RF signal frame data retroactive by a certain number of frame intervals. Since the number can be arbitrarily selected, the frame rate can be changed stepwise by changing the number of frame intervals stepwise. Then, the strain amount ratio in the tissue elasticity image obtained at each frame rate is obtained, and the frame rate at which it becomes the maximum, that is, the number of frame intervals is set as an optimum parameter.

  A second feature of the ultrasonic diagnostic apparatus according to the present invention is that ultrasonic transmission / reception means for transmitting and receiving ultrasonic waves to a subject and outputting reflected echo signals, and the ultrasonic transmission / reception means output from the ultrasonic transmission / reception means. A tomographic scanning unit that repeatedly acquires RF signal frame data in the subject using a reflected echo signal at a predetermined period, and a displacement from a plurality of time-series RF signal frame data groups acquired by the tomographic scanning unit. RF signal frame for selecting RF signal frame data at the present time and RF signal frame data separated by a predetermined number of frame intervals going back in the past by an arbitrary number of frames as a set of RF signal frame data to be measured The data selection means and the distortion amount ratio obtained by changing the predetermined cycle of the tomographic scanning means stepwise Parameter setting means for setting the period of the layer scanning means, signal processing means for generating elastic image data based on the set of RF signal frame data selected by the RF signal frame data selection means, and generated by the signal processing means Image display means for displaying the elastic image data. This is because, when the number of frame intervals is fixed, the scanning period of the tomographic scanning means, that is, the frame rate is changed stepwise to obtain the strain amount ratio in the tissue elastic image obtained at each frame rate, which is the maximum. The frame rate, that is, the scanning cycle is set as an optimum parameter.

  According to a third feature of the ultrasonic diagnostic apparatus of the present invention, in the ultrasonic diagnostic apparatus described in the first or second feature, the parameter setting means has an optimum rejection level based on the distortion amount ratio. Is to set. The rejection level is a function that hides an elastic image of a frame when the distortion amount ratio of the frame is equal to or less than a threshold value. The threshold of the rejection level is set based on the distortion amount ratio.

  According to the present invention, there is an effect that tissue elasticity image rendering parameters can be automatically optimized according to the diagnosis situation without bothering the operator.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention. This ultrasonic diagnostic apparatus obtains a tomographic image of a diagnostic region of a subject using ultrasonic waves, and displays an elastic image representing the hardness or softness of the biological tissue of the subject. As shown in the figure, the ultrasonic diagnostic apparatus includes a probe 1, an ultrasonic transmission / reception unit 2, a tissue elasticity image signal processing unit 3, a display device 4, a control unit 5, a control panel 8, And an external storage medium 9. The control unit 5 includes an internal storage medium 6 and a tissue elasticity image parameter optimization unit 7.

  In the figure, a probe 1 converts an electric signal from the apparatus into an ultrasonic wave and converts a reflected echo from a living body into an electric signal. The ultrasonic transmission / reception unit 2 generates an electric signal for ultrasonic transmission, receives a reflected echo signal from the living body, and performs phasing. The tissue elasticity image signal processing unit 3 performs various processes on the reflected echo signal received by the ultrasonic transmission / reception unit 2 to finally generate a tissue elasticity image and output it to the display device 4.

  The operator inputs each operation information and subject information to the apparatus using the control panel unit 8. The internal recording medium 6 and the external recording medium 9 temporarily store and record various data such as image data and subject information. The control unit 5 controls the entire ultrasonic apparatus.

  In the present invention, a tissue elasticity image parameter optimization unit 9 is provided in the control unit 6, calculates a tissue elasticity image rendering parameter that is optimal according to each diagnosis situation, and uses the calculated parameter for the ultrasound transmission / reception unit 2. And output to the tissue elasticity image signal processing unit 3.

  Next, detailed processing of the tissue elasticity image signal processing unit 3 will be described. FIG. 2 is a diagram illustrating a detailed configuration of the tissue elasticity image signal processing unit. The frame data storage unit 21 in the current phase and the frame data storage unit 21 in the previous phase store two echo echo signals received by the ultrasonic transmission / reception unit 2.

The displacement amount calculation unit 22 performs a correlation process on the data for two frames stored in the frame data storage units 20 and 21, and how much the current phase data is deviated from the previous frame data. Calculate whether
If the current phase data is shifted upward relative to the data of the previous time phase, a negative displacement amount (indicating that the tissue has moved upward), and the current phase data of the previous time phase data If the data is shifted downward, a positive displacement amount (indicating that the tissue has moved downward) is obtained.

The distortion amount calculation unit 23 performs a differentiation process on the displacement amount data from the displacement amount calculation unit 22 to calculate the distortion amount. If the displacement amount has a positive slope, it becomes a positive distortion amount, and if it has a negative inclination, it becomes a negative distortion amount.
The intra-frame distortion amount average value calculation unit 24 obtains a ratio of data having a positive distortion amount and data having a negative distortion amount in one frame. This ratio is used to determine whether the tissue elasticity image at that time phase is valid or invalid.

  The tissue elasticity image is drawn by pushing or pulling the probe 1 in contact with the subject. Therefore, the positive distortion amount occupies most when pressed, and conversely, the negative distortion amount occupies most when pulled.

  If the distortion amount ratio is small, it is determined that the elasticity data of the frame is not appropriate. In that case, since the elastic image of this frame is inappropriate and invalid from the intra-frame distortion amount average value calculation unit 24 to the image processing unit 25, a signal for non-display is output. This signal is a tissue elasticity image invalid signal.

  In addition, the ratio of the distortion amount at which the elastic image invalid signal is generated by providing a stepwise threshold with respect to the distortion amount ratio can be arbitrarily set by the operator operating the control panel unit 8. . The threshold value of the distortion amount ratio is set as a rejection level. The rejection level is a function that hides an elastic image of a frame when the distortion amount ratio of the frame is equal to or less than a threshold value. That is, it is a function that does not display an improper tomographic image.

  The tissue elasticity image is drawn using the frame data of the current phase and the frame data of the previous time phase. Further, the frame data of the two time phases vary depending on the pressing / pulling speed of the probe 1. Therefore, an appropriate tissue elasticity image cannot be obtained even if ultrasonic waves are transmitted and received at a slow frame rate when the probe 1 is pushed / pulled at high speed. The reverse is also true.

  The distortion amount ratio within one frame varies depending on the pushing / pulling speed of the probe, the elasticity of the tissue at the diagnostic site, and the like. Therefore, it is possible for the operator to appropriately draw an elastic image based on the elastic frame data by setting the frame rate and the rejection level of ultrasonic scanning according to the diagnosis situation.

  Therefore, in this embodiment, an appropriate frame rate and rejection level can be automatically set according to the speed of pushing / pulling the probe 1 and the elasticity of the tissue at the diagnostic site by the following procedure. To do.

  FIG. 3 is a diagram illustrating an example of parameter optimization processing. First, the control unit 6 of the ultrasonic apparatus switches the frame rate in stages. In this embodiment, it is assumed that the frame rate is switched to five levels of Max, High, Middle, Low, and Min. During this time, it is assumed that the operator pushes / pulls the probe 1 at a fixed arbitrary speed.

  First, in the first step S31, the distortion amount ratio for each frame output from the intra-frame distortion amount average value calculation unit 24 is stored at the frame rate Max, and the distortion amount ratio for a certain number of frames is stored. The average R1 of the acquisition is obtained. In the next step S32, the frame rate is switched from Max to High, the same processing is performed, and the average R2 is obtained. As described above, in steps S33 to S35, the frame rate is sequentially switched like Middle, Low, and Min to finish obtaining the distortion amount ratio average values R3 to R5.

  The tissue elasticity image parameter optimization unit 7 in the ultrasonic device control unit 5 stores five frame rate values of Max, High, Middle, Low, and Min and distortion amount ratio average values R1 to R5 for the frame rate. ing.

  Therefore, in step S36, the maximum strain amount ratio average value is obtained by comparing the five strain amount ratio average values R1 to R5 in the tissue elasticity image parameter optimization unit 7. A frame rate value giving this maximum distortion amount ratio average value is output to the control unit 5 of the ultrasonic apparatus. The control unit 6 of the ultrasonic apparatus performs subsequent transmission / reception of ultrasonic waves at the frame rate at which the distortion amount ratio average value is maximized, and renders an elastic image.

Further, in step S37, the rejection level is set so that the elastic image is rendered effective in the strain amount ratio.
As an example, assume that there are four stages of rejection levels.
Rejection level 4 is when the distortion ratio is 9: 1 (90%) or higher.
Rejection level 3 is when the distortion amount ratio is 8: 2 (80%) or more.
Rejection level 2 is when the distortion amount ratio is 7: 3 (70%) or higher.
Rejection level 1 is when the distortion amount ratio is 6: 4 (60%) or more.
Assume that the tissue elasticity image is appropriate and enable rendering.

  For example, when the strain amount ratio at the frame rate at which the strain amount ratio average value is maximum is 72%, the rejection level 2 is set in the tissue elasticity image parameter optimization unit 7.

  As described above, the two parameters of the frame rate and the rejection level are automatically optimized according to the diagnosis situation.

  Alternatively, the parameter may be recorded on the external recording medium 9, and the operator may read the parameter as needed to render an elastic image.

  In the above-described embodiment, the case where the optimum frame rate is extracted by switching the frame rate has been described. However, the number of frame intervals between the past and current RF signal frame data is set to an appropriate size. Also good. That is, in FIG. 2, the case where the frame data storage units 20 and 21 store the frame data having a time interval of one time phase has been described. However, the number of frame intervals may be set to a plurality of time phases.

It is a block diagram which shows the Example of the ultrasonic diagnosing device by this invention. It is a figure which shows the detailed structure of a tissue elasticity image signal processing part. It is a figure which shows an example of the optimization process of a parameter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ultrasonic probe 2 ... Ultrasonic transmission / reception part 3 ... Tissue elastic image signal processing part 4 ... Display apparatus 5 ... Control part 6 ... Internal recording medium 7 ... Tissue elastic image parameter optimization part 8 ... Control panel part 9 ... External recording medium 20 ... current frame data storage unit 21 ... previous frame data storage unit 22 ... displacement calculation unit 23 ... distortion calculation unit 24 ... intra-frame distortion average calculation unit 25 ... image processing Part

Claims (3)

Ultrasonic transmission / reception means for transmitting and receiving ultrasonic waves to a subject and outputting reflected echo signals;
A tomographic scanning means for repeatedly acquiring RF signal frame data in the subject at a predetermined cycle using the reflected echo signal output from the ultrasonic transmitting / receiving means;
From a plurality of time-series RF signal frame data groups acquired by the tomographic scanning means, a set of RF signal frame data to be subjected to displacement measurement is present RF signal frame data, and an arbitrary number of frames therefrom. RF signal frame data selection means for selecting RF signal frame data separated by a predetermined number of frame intervals going back in the past;
Parameter setting means for setting an optimum number of frame intervals based on a distortion amount ratio obtained by changing the number of frame intervals stepwise;
Signal processing means for generating elastic image data based on a set of RF signal frame data selected by the RF signal frame data selection means;
An ultrasonic diagnostic apparatus comprising: image display means for displaying the elasticity image data generated by the signal processing means. Ultrasonic transmission / reception means for transmitting and receiving ultrasonic waves to a subject and outputting reflected echo signals;
A tomographic scanning means for repeatedly acquiring RF signal frame data in the subject at a predetermined cycle using the reflected echo signal output from the ultrasonic transmitting / receiving means;
From a plurality of time-series RF signal frame data groups acquired by the tomographic scanning means, a set of RF signal frame data to be subjected to displacement measurement is present RF signal frame data, and an arbitrary number of frames therefrom. RF signal frame data selection means for selecting RF signal frame data separated by a predetermined number of frame intervals going back in the past;
Parameter setting means for setting the period of the tomographic scanning means based on a distortion amount ratio obtained by changing the predetermined period of the tomographic scanning means stepwise;
Signal processing means for generating elastic image data based on a set of RF signal frame data selected by the RF signal frame data selection means;
An ultrasonic diagnostic apparatus comprising: image display means for displaying the elasticity image data generated by the signal processing means.   3. The ultrasonic diagnostic apparatus according to claim 1, wherein the parameter setting unit sets an optimum rejection level based on the distortion amount ratio.

Images