JP2015136449A - Ultrasonic diagnostic apparatus and beam forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance calculation accuracy of delay data in an ultrasonic diagnostic apparatus.SOLUTION: The thickness of a fat layer 116 is specified on each path 108 connecting each vibration element and a focal point 100. A distance 110 between the vibration element and the focal point 100 is divided into a fat layer section 112 and a non-fat layer section 114 on each path 108. At the time of calculation of delay data, sound speed for fat is applied to the fat layer section 112 and general sound speed is applied to the non-fat layer section 114. A skin layer section is further specified and sound speed for skin may be applied thereto.

Description

  The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to generation of delay data for beam forming.

  In ultrasonic diagnosis, in general, a probe containing an array transducer composed of a plurality of vibration elements is brought into contact with the surface of a living body, and transmission and reception of ultrasonic waves are executed in this state. An ultrasonic beam is formed by the array transducer, and the ultrasonic beam is scanned electronically.

  A transmission beam is formed by supplying a plurality of transmission signals with a predetermined delay relationship to the plurality of vibration elements. In addition, a reception beam is formed by performing phasing addition processing on a plurality of reception signals from a plurality of vibration elements. At the time of reception, a reception dynamic focus technique for dynamically shifting the reception focus in a deep direction is applied.

  In order to form an ultrasonic beam (transmission beam, reception beam) having a desired shape in a desired direction, it is necessary to apply appropriate delay processing to the plurality of transmission signals and the plurality of reception signals. Therefore, delay data is given to the beamformer. Delay processing conditions are determined based on such data.

  In general, delay data is calculated on the assumption that the speed of sound in a living body is constant. However, the actual sound speed varies depending on the properties of the living tissue. In particular, the fat layer exists subcutaneously with a certain thickness in many subjects, and the sound speed in the fat layer is different from the sound speed of other general tissues.

  Patent Document 1 discloses an ultrasonic diagnostic apparatus that calculates delay data based on the thickness of a fat layer. In such an apparatus, the thickness of the fat layer is specified by manually specifying two boundaries of the fat layer on the tomographic image. The delay data is calculated on the assumption that the fat layer has a certain thickness.

  Also in the ultrasonic diagnostic apparatus disclosed in Patent Document 2, delay data is calculated based on the thickness of the fat layer. This document discloses the calculation of the thickness by the received signal processing in addition to the input of the thickness by the user, but does not disclose the specific method. This document also mentions that the thickness of the fat layer is determined in each direction, but does not disclose the specific method. In general, the boundary of the fat layer is quite unclear on the B-mode tomographic image, and it is difficult to automatically extract the entire fat layer based on the B-mode tomographic image itself. If the accuracy of identifying the fat layer is low, the thickness of the fat layer cannot be measured with high accuracy, resulting in a decrease in the accuracy of delay data calculation. Note that Patent Literature 3 discloses a sound speed correction technique.

Japanese Patent No. 4711583 Japanese Patent No. 2759808 Japanese Patent Laid-Open No. 5-115475

  An object of the present invention is to improve the image quality of an ultrasonic image by increasing the beamforming accuracy. Alternatively, an object of the present invention is to enable a user to set a delay processing condition adapted to an actual in vivo structure without any particular burden on the user. Alternatively, an object of the present invention is to enable generation of delay data in which the fat layer is accurately identified and its form is reflected.

  An ultrasonic diagnostic apparatus according to the present invention is an image representing an array transducer having a plurality of vibration elements that form an ultrasonic beam and a tissue structure on a scanning surface formed by electronic scanning of the ultrasonic beam. Based on a fat layer reference tomographic image different from the B-mode tomographic image, measuring means for individually measuring a fat layer thickness on each path between a beam focus and each of the vibration elements, and the plurality of vibrations Based on a plurality of fat layer thicknesses measured on a plurality of paths corresponding to the element, a calculation unit that calculates delay data for forming the ultrasonic beam, and performs beam forming based on the delay data A beam former.

  The speed of ultrasonic waves in the fat layer is significantly different from the speed of ultrasonic waves in other tissues, so it is not necessary to distinguish between fat layers and other tissues. When uniform sound speed (representative sound speed) is applied, good focus cannot be obtained, or an ultrasonic beam shape as designed cannot be obtained. This causes a deterioration in the image quality of the ultrasonic image.

  On the other hand, according to the said structure, the fat layer thickness on each path | route between each vibration element and a beam focus is measured separately. Usually, since the thickness of the fat layer changes in the beam scanning direction, in the above configuration, the fat layer thickness is measured for each path. However, the fat layer thickness may be actually measured for a plurality of paths, and the fat layer thickness may be estimated by interpolation for the other paths. In any case, the fat layer thickness is specified for each path, and the delay data is calculated based on the fat layer thickness. Therefore, when calculating the beamforming delay data, the sound speed specific to the fat layer can be applied to the portion corresponding to the fat layer on each path, so that the delay data can be calculated with high accuracy, As a result, it is possible to realize a good focus and to bring the actual ultrasonic beam shape closer to the ideal shape. That is, the image quality of the ultrasonic image can be improved.

  In calculating the delay data, preferably, a general sound speed (representative sound speed) is applied to the internal tissue existing behind the fat layer. It is also possible to prepare a table indicating the sound speed for each tissue type and calculate delay data by applying a sound speed unique to each organization.

  In general, it is often difficult to clearly identify the fat layer on the B-mode tomographic image in which the echo intensity is expressed by luminance. In the above configuration, the fat layer thickness on each path can be measured on the basis of the fat layer reference tomographic image that is different from the B-mode tomographic image and can identify the fat layer relatively clearly. As a result, good beam forming can be realized.

  The fat layer thickness is desirably the thickness of only the fat layer, but since the skin layer is thin, the thickness of the combined portion of the fat layer and the skin layer may be defined as the fat layer thickness. This eliminates the need to detect the boundary between the fat layer and the skin layer. Since the ultrasonic wave propagation layer (acoustic lens or the like) in the probe is also thin, the thickness of the portion including the fat layer, the skin layer, and the ultrasonic wave propagation layer in the probe may be defined as the fat layer thickness. However, since the thickness of the ultrasonic wave propagation layer in the probe is known, another sound speed may be applied thereto. Alternatively, the delay data may be calculated ignoring such an ultrasonic wave propagation layer. After applying the delay data calculated based on the fat layer reference tomographic image acquired at a predetermined timing, the delay data may be maintained as it is until the diagnosis site is changed. The delay data may be updated periodically, in which case the delay data may be updated in real time. It should be noted that a conventional calculation method can be used for calculating the delay data except that a plurality of types of sound speeds are applied on each path. A straight path may be assumed as each path, but a path considering refraction may be assumed. Preferably, the transmission delay data and the reception delay data are updated by the above method. However, the above method may be applied to one of them, and default delay data may be applied to the other. From the viewpoint of biosafety, it is desirable to apply the above method not to delay data for transmission but to delay data for reception. When receiving dynamic focus is performed, delay data is calculated for each depth of each sample point.

  Preferably, the storage unit stores information indicating the fat sound speed and the representative sound speed, and the calculation unit calculates the fat sound speed for the fat layer section specified by the fat layer thickness on each path. The delay data is calculated by applying the representative sound speed to all or part of other sections. Preferably, the storage unit further stores information indicating the sound velocity for skin, and the other section includes a skin layer section, and an inner section between the lower surface of the fat layer and the beam focus, The computing unit applies the sound speed for skin to the skin layer section and applies the representative sound speed to the internal section. According to this configuration, the sound speed suitable for each tissue can be finely applied, so that the beamforming accuracy can be further improved.

  Preferably, tissue elasticity image forming means for forming a tissue elasticity image representing tissue elasticity as the fat layer reference tomographic image based on reception data obtained from the scanning plane is included. According to this configuration, the fat layer thickness can be measured based on information obtained by transmitting and receiving ultrasonic waves. The tissue elasticity image is an image representing elasticity information (displacement, strain, elastic modulus, etc.) at each position in the living body. Since the elastic information is different between the fat layer and other tissues, the fat layer can be identified relatively clearly. Note that default delay data is used for the first measurement. If the delay data is repeatedly updated, the fat layer thickness reference tomographic image that is the basis for measuring the fat layer thickness is improved, so that the accuracy of beam forming increases.

  Preferably, selection means for selecting a tissue elasticity image to be referred to when calculating the delay data based on the received data is included. According to this configuration, for example, the tissue elasticity image acquired in a state where the probe contact state is not appropriate is excluded, and the fat layer thickness is based on the tissue elasticity image acquired in a state where the probe contact state is appropriate. Can be measured. For example, since the inter-frame correlation value deteriorates while the probe is moving, it is possible to determine the stabilized state of the probe, that is, the stabilized state of the scanning plane, based on the inter-frame correlation value.

  Preferably, it includes means for forming a non-ultrasonic tomographic image by acquiring cross-sectional data corresponding to the scanning plane from volume data acquired by another medical device, and the fat layer reference tomographic image is the It is a non-ultrasonic tomographic image. According to this configuration, tomographic data corresponding to the current beam scanning plane is acquired from volume data acquired by an X-ray CT apparatus, an MRI apparatus, or the like, and the fat layer thickness is measured based on the tomographic data. In such tomographic data, it is possible to clearly identify the fat layer. More specifically, according to the X-ray CT apparatus, the MRI apparatus, etc., tomographic data with high resolution or tomographic data in which tissue differences are emphasized can be obtained. It is possible to accurately calculate the thickness (distance) of the fat layer after correctly identifying the fat layer by using it. Therefore, according to the said structure, compared with the case where it calculates using the tissue elasticity image based on echo information, a beam forming precision can be improved more.

  The above method can be applied in various modes other than the B mode. Although it is not always necessary to display the fat layer reference tomographic image, the image may be displayed. In that case, the detected fat layer boundary may be clearly indicated.

  The beam forming method according to the present invention includes a step of individually measuring a fat layer thickness on each path between a beam focus and each vibration element based on fat layer measurement data representing a tissue structure in a living body. For forming the ultrasonic beam based on a plurality of fat layer thicknesses corresponding to the plurality of vibration elements, a sound velocity of the ultrasonic wave in the fat layer, and a general sound velocity of the ultrasonic wave in the living tissue A step of calculating delay data, a step of providing the delay data to a beam former, and a step of forming at least one of a transmission beam and a reception beam by delay processing by the beam former. The above method can be realized as a function of a program. The program is installed in the ultrasonic diagnostic apparatus via a portable storage medium or a network.

  ADVANTAGE OF THE INVENTION According to this invention, the beam forming precision can be improved and the image quality of an ultrasonic image can be improved. Alternatively, according to the present invention, it is possible to set a delay processing condition suitable for an actual in vivo structure without any particular burden on the user. Alternatively, according to the present invention, it is possible to generate delay data reflecting the form after accurately specifying the fat layer.

1 is a block diagram showing a first embodiment of an ultrasonic diagnostic apparatus according to the present invention. It is a figure which shows the structural example of a transmission beam former and a reception beam former. It is a figure which shows the example of a display in 1st Embodiment. It is a figure which shows the 1st example of the area division on each path | route. It is a figure showing the 2nd example of section division on each route. It is a block diagram which shows 2nd Embodiment of the ultrasonic diagnosing device which concerns on this invention. It is a figure which shows the example of a display in 2nd Embodiment. It is a conceptual diagram which shows the case where area division is applied with respect to electronic sector scanning.

  FIG. 1 shows a first embodiment of an ultrasonic diagnostic apparatus according to the present invention. This ultrasonic diagnostic apparatus is an apparatus that is installed in a medical institution such as a hospital and forms an ultrasonic image by transmitting and receiving ultrasonic waves to and from a living body. The ultrasonic diagnostic apparatus shown in FIG. 1 has a function of forming a B-mode tomographic image and an elastic image.

  In FIG. 1, a probe 10 is an ultrasonic probe that transmits and receives ultrasonic waves. In the present embodiment, the probe 10 has an array transducer 12 composed of a plurality of transducer elements. The plurality of vibration elements are arranged linearly in the illustrated example. Of course, they may be arranged in an arc.

  An ultrasonic beam 16 is formed by the array transducer 12. The ultrasonic beam 16 is scanned electronically, thereby forming a scanning surface. As the electronic scanning method, an electronic linear scanning method is applied in the present embodiment. Of course, other scanning methods such as an electronic sector method may be applied. In the electronic linear scanning method, a transmission / reception opening 14 is set on the array transducer 12, and an ultrasonic beam 16 is formed using a plurality of vibration elements included in the transmission / reception opening 14. The ultrasonic beam 16 is electronically scanned by moving the transmission / reception aperture 14 in the element array direction.

  In this embodiment, the 1D array transducer 12 is provided, but a 2D array transducer may be provided. Moreover, you may make it use the probe inserted in a body cavity other than the probe 10 contact | abutted to a biological body.

  The transmission beam former 18 constitutes a transmission circuit. At the time of transmission, a plurality of transmission signals are supplied from the transmission beam former 18 to the array transducer 12 in parallel. In this case, a delay time is given to each transmission signal in order to form an ultrasonic beam (transmission beam). The transmission beam former 18 performs delay processing on individual transmission signals based on the transmission delay data. When a plurality of transmission signals are sent to the array transducer 12, a transmission beam is formed by the array transducer 12.

  At the time of reception, when a reflected wave from the living body is received by the array transducer 12, a plurality of reception signals are output from the array transducer 12 to the reception beam former 20. The reception beamformer 20 constitutes a reception circuit. It executes a phasing addition process on a plurality of input reception signals, thereby transmitting beam data as a reception signal after phasing addition. In the phasing addition process, a delay process for forming a reception beam is applied to each received signal. The reception beamformer 20 performs a phasing addition process so that a reception focus point is formed for each depth according to a so-called reception dynamic focus method. In that case, reception delay data is used.

  In the first embodiment shown in FIG. 1, the delay data for transmission and the delay data for reception are calculated by the delay data calculation unit 24. Default transmission delay data and reception delay data are also prepared. As will be described in detail later, in the present embodiment, the delay data calculation unit 24 performs the fat sound velocity for the fat layer section in accordance with the fat layer thickness on each path connecting each vibration element and the focal point. The delay data is calculated by applying (sound speed in the fat layer) and applying the representative sound speed (general sound speed in the living body) to the other sections. At that time, the sound speed table 46 is referred to.

  In the configuration shown in FIG. 1, both transmission delay data and reception delay data are calculated. However, for example, only reception delay data may be calculated. In that case, data prepared as default data is used as transmission delay data.

  In this embodiment, for example, 1540 m / s is registered as the representative sound speed, and 1470 m / s is registered as the fat sound speed in the sound speed table 46. Furthermore, if necessary, for example, 1605 m / s may be registered as the sound velocity for the skin, and the sound velocity for other tissues may be registered. All of the numerical values given above are examples, and individual numerical values can be changed depending on the situation.

  The signal processing unit 26 is a module that performs predetermined signal processing on the beam data output from the reception beamformer. The signal processing includes processing such as detection, logarithmic compression, and filtering.

  In the present embodiment, the B-mode image forming unit 28 is configured by a digital scan converter (DSC). The B-mode image forming unit 28 forms a B-mode image as a black and white tomographic image by applying coordinate conversion, interpolation processing, and the like to a plurality of input beam data. The image data is sent to the display device 40 via the display processing unit 30.

  Next, formation of the elastic image and measurement of the fat layer thickness based on the elastic image will be described.

  The frame selection unit 32 performs a correlation calculation between sequentially input frames (frame data). Each frame corresponds to one scanning plane, which is composed of a plurality of beam data. Each beam data is composed of a plurality of echo data arranged in the depth direction. The frame selection unit 32 performs a correlation calculation between adjacent frames to obtain a correlation value, and determines whether the correlation value is within a certain excellent range. When the correlation value is within the excellent range, the displacement calculation is executed or the displacement calculation result is validated. For example, under a situation where the probe is moved on the body surface, the correlation value between frames becomes very poor. When an elastic image is formed in such a situation, it is difficult to obtain an appropriate elastic image that forms the basis of delay data calculation. That is, when the elastic image obtained under such circumstances is used as a basis, the measurement accuracy of the fat layer thickness is lowered. On the other hand, in the present embodiment, the frame selection unit 32 determines whether the probe is stable, and an elastic image is formed based on the frame sequence acquired in such a stabilized state. Yes. In the present embodiment, the correlation value calculation is performed based on the RF signal output from the reception beamformer, and the stabilization state is determined thereby. However, the stabilization state is determined based on the elastic image. It may be.

  The frame sequence acquired in the stabilized state is sent to the displacement calculation unit 34. The displacement calculation unit 34 is a module that calculates a displacement for each coordinate between frames. Various known methods can be used for calculating the displacement. For example, the displacement can be calculated by applying a pattern matching process for each coordinate of interest between frames. In that case, a two-dimensional displacement vector may be calculated, or a displacement component in the beam direction, that is, the depth direction may be calculated. In addition to a method of calculating displacement between adjacent frames, a method of calculating displacement between a reference frame and a currently obtained frame may be used.

  The elasticity information calculation unit 36 is a module that calculates elasticity information for each coordinate by applying a spatial differentiation process or the like based on the displacement calculated for each coordinate on the frame. The elasticity information is, for example, strain, and an elastic modulus or the like may be calculated instead. When calculating elasticity information, it is possible to use various known methods such as a method in which displacement is given by a push pulse due to radiation pressure, and elasticity information is calculated based on sound velocity information of a transverse wave generated by the displacement. It is.

  The elastic image forming unit 38 is a module that forms an elastic image by two-dimensionally mapping elasticity information obtained for each coordinate. In this embodiment, the elastic image forming unit 38 is configured by a digital scan converter (DSC).

  The display processing unit 30 has a color calculation function, an image composition function, and the like. A process of associating the elasticity information with the hue is executed for the elasticity image, thereby forming an elasticity image as a color image. In this case, for example, a soft tissue portion is expressed in a red color, and a hard tissue portion is expressed in a blue color. When the elastic image is displayed on the display 40 as a color image, a B-mode image is also displayed as the background image.

  In the present embodiment, elasticity information is sent to the boundary detection unit 42. The boundary detection unit 42 has a function of identifying the fat layer on the scanning plane and detecting the lower boundary of the fat layer. That is, the boundary between the fat layer and the internal tissue on the back side is specified. Furthermore, the upper boundary of the fat layer, ie the boundary between the skin layer and the skin layer, may be specified. Furthermore, other tissue boundaries may be identified. In specifying the boundary, a technique such as edge search along the beam direction, that is, the depth direction can be used. In this regard, various known edge detection techniques can be used. In the first embodiment, the lower boundary of the fat layer is specified based on the elastic image. Specifically, the boundary is specified from the degree of change in the elasticity information by observing the elasticity information along the depth direction. Furthermore, the boundary line of the fat layer is formed by connecting a plurality of identified boundary points in the electronic scanning direction and applying interpolation processing, smoothing processing, etc. to the curve obtained thereby.

  The thickness calculation unit 44 is a module that calculates the thickness of the fat layer on each path connecting each vibration element and the focal point. In that case, the boundary detected by the boundary detection unit 42 is referred to. There are several possible definitions of fat layer thickness. For example, the distance from each vibration element to the lower boundary of the fat layer may be defined as the fat layer thickness. Further, the distance from the body surface to the lower boundary of the fat layer may be defined as the fat layer thickness. Furthermore, the distance between the upper boundary and the lower boundary in the fat layer may be defined as the fat layer thickness.

  The transmission / reception control unit 22 is a controller that controls the transmission beam former 18 and the reception beam former 20. The transmission / reception control unit 22 includes a delay data calculation unit 24 that calculates transmission delay data and reception delay data in this embodiment. The delay data calculation unit 24 applies the sound speed for fat to the section corresponding to the fat layer thickness on the path for each vibration element, and applies the representative sound speed to the other non-fat layer section, Delay data is being calculated. In that case, each sound speed registered on the sound speed table 46 is referred to. Except for applying the sound speed corresponding to each section, it is possible to use a conventional delay data calculation method for calculating the delay data. As will be described later, the fat layer thickness may be specified, the skin layer thickness may also be specified, and the optimum sound speed may be applied to each. The calculated transmission delay data is sent to the transmission beam former 18, and the calculated reception delay data is sent to the reception beam former 20. Alternatively, delay conditions in the transmission beam former 18 and the reception beam former 20 are set based on such delay data. The configuration shown in FIG. 1 is controlled by a main control unit (not shown). The main control unit is constituted by a CPU and an operation program. The main control unit controls the transmission / reception control unit 22. An operation panel is connected to the main control unit, and the user can select an operation mode and perform various inputs using the operation panel. The individual blocks (configurations) shown in FIG. 1 can be realized as software functions.

  As described above, according to the embodiment shown in FIG. 1, the fat layer thickness can be measured on each path based on the elastic image acquired in the stabilized state, and the delay data can be accurately calculated based on them. The update of the delay data may be executed based on a predetermined event, or may be performed periodically. The delay data may be updated sequentially in real time. The transmission delay data includes a plurality of delay data corresponding to a plurality of transmission beam addresses. In electronic linear scanning, the contents of the delay data may be made common. The reception delay data consists of a plurality of delay data sets corresponding to a plurality of reception beam addresses. In electronic linear scanning, the contents of these delay data sets may be made common. Each delay data set includes a plurality of delay data corresponding to a plurality of reception point depths.

  FIG. 2 shows a configuration example of the transmission beamformer and the reception beamformer. As described above, the array transducer 12 is composed of a plurality of transducer elements 12a. The array transducer 12 is connected to the transmission beam former 18 and the reception beam former 20 via a switching circuit 48. The switching circuit 48 is a circuit for scanning the transmission / reception aperture in the element arrangement direction (electronic scanning direction).

  The transmission beam former 18 has a plurality of transmitters 50. Each transmitter 50 includes a waveform memory 52, a delay circuit 54, a D / A converter 56, and a power amplifier 58. The timing of reading waveform data from the waveform memory 52 is controlled by a control signal 59, and the waveform data read from the waveform memory 52 is delayed by the delay circuit 54. In this case, for example, coarse delay processing may be executed by adjusting the read timing of the waveform memory 52, and finer delay processing may be applied to the delay circuit 54. The delay condition in the delay circuit 54 is determined by the control signal 61. The delay circuit 54 can be configured as an interpolation circuit, for example. The D / A converter 56 converts the input transmission signal as an analog signal into a transmission signal as a digital signal. The read timing of the waveform memory 52 and the delay condition in the delay circuit 54 are determined based on the delay data described above. A plurality of waveform memories may be constituted by a single waveform memory.

  The reception beam former 20 includes a plurality of receivers 60 and an adder 62. Each receiver 60 includes a preamplifier 64, a D / A converter 66, and a delay circuit 68. Each received signal is amplified by the preamplifier 64 and then input to the D / A converter 66 where it is converted into a digital signal. The digital reception signal is subjected to delay processing in the delay circuit 68. The delay condition in that case is determined by the control signal 70. A plurality of received signals after the delay processing are added in the adder 62. As a result, a reception beam is electronically configured. The beam data 72 after the phasing addition processing is output to the signal processing unit 26 and the frame selection unit 32 shown in FIG. The beam data is an RF signal. When executing the reception dynamic focus, the delay processing condition is switched every time the reception focus is switched. A protection circuit and the like provided between the switching circuit 48 and the reception beam former 20 are not shown.

  FIG. 3 shows a display example according to the first embodiment. In the example shown in FIG. 3, a B-mode image 76 and an elastic image 78 are displayed side by side in the left-right direction on the display screen 74. Both the B-mode image 76 and the elastic image 78 are images that are updated in real time. On the B-mode image 76, the lower boundary 84 and the upper boundary 86 of the fat layer are generally unclear. The contour of the tumor 82 is also quite blurred.

  On the other hand, the elasticity image 78 is an image displaying elasticity information at each position as described above, that is, an image representing the hardness in each tissue. In the illustrated example, the hardness of the tissue is represented by a color. The color sample is a color bar 80. In the elastic image 78, the entire mass 90 is represented by a color within a certain range, and the entire fat layer is represented by a color within another certain range. The fat layer is a soft layer and is displayed in a color different from a hard mass or the like. Therefore, it is possible to easily specify the lower boundary 92 of the fat layer. Furthermore, it is easy to specify the upper boundary 94 of the fat layer. Incidentally, reference numeral 88 represents a region of interest, and elastic information in the region of interest 88 is expressed in color. Of course, the elasticity information may be displayed over the entire scanning surface. A B-mode image is also displayed as the background of the elastic image 78.

  Although it is not always possible to clearly identify the fat layer on the B-mode image 76, it is possible to identify the fat layer, particularly its boundary, relatively easily using the elastic image 78. In FIG. 3, the elastic image 78 is displayed as a color image. However, the elastic image 78 is not necessarily displayed as long as the fat layer thickness can be measured. That is, the elastic image 78 may be used in the background processing.

  FIG. 4 shows a first example of section division on each route. In FIG. 4, the relationship between the array transducer 12 and the scanning plane 79 is shown as a conceptual diagram. The x direction is the element arrangement direction, that is, the electronic scanning direction. A transmission / reception aperture 14 is set on the array transducer 12 and scanned in the electronic scanning direction. A region of interest 88 is set on the scanning surface 78, which corresponds to a range for calculating elasticity information. According to the present embodiment, it is possible to easily specify the lower boundary 92 of the fat layer 116 based on the elastic image. In addition, the code | symbol 118 represents the skin layer and the boundary between the skin layer 118 and the fat layer 116 is not specified specially in the example shown in FIG. Reference numeral 120 denotes an internal tissue on the back side of the fat layer 116. Reference numeral 104 indicates a body surface level, and reference numeral 106 indicates a level at which the focal point 100 exists. Reference numeral 102 indicates the depth of focus.

  In FIG. 4, the path group is shown as a plurality of lines connecting the individual vibration elements and the focal point 100. Reference numeral 108 indicates one path. In the present embodiment, when the boundary 92 is specified, the fat layer thickness is specified on each path 108. In FIG. 4, reference numeral 110 indicates a distance from the vibration element to the focal point 100, reference numeral 112 indicates a fat layer section, and reference numeral 114 indicates a non-fat layer section (inner section). In the illustrated example, the distance 112 from the end face of the vibration element to the boundary 92 is defined as the fat layer thickness. In other words, the fat layer section 112 includes a portion other than the fat layer in a strict sense, but since this portion is a relatively thin region, there is not much problem in delay data calculation. In calculating the delay data, the sound speed for fat is applied to the fat layer section 112, and the representative sound speed is applied to the non-fat layer section 114. Such processing is executed for each section on each route. This makes it possible to calculate delay data with high accuracy. In particular, a comfortable sound speed can be set for each route according to the form of the boundary 92. In FIG. 4, each path is represented as a straight path, but it is also possible to set the path in consideration of refraction. However, if such a route setting is performed, the amount of calculation becomes enormous, so it is desirable to assume a straight route as in this embodiment. In FIG. 4, the ultrasonic transmission part in the probe is considered, but of course, the distance from the wave transmitting / receiving surface to the boundary 92 in the probe may be defined as the fat layer thickness. In FIG. 4, a path intersecting at one point is shown, but various focal points can be realized to manipulate the shape of the ultrasonic beam.

  FIG. 5 shows a second example of section division. The same components as those shown in FIG. 4 are denoted by the same reference numerals, and the description thereof is omitted. In the second example shown in FIG. 5, the distance 110 from the vibrating element to the focal point 100 is divided into a plurality of sections on each path 108. Reference numeral 114 represents a non-fat layer section (inner section), reference numeral 126 represents a fat layer section, reference numeral 124 represents a skin layer section, and reference numeral 122 represents an intra-probe ultrasonic wave propagation section. Yes. As described above, by dividing the section more finely, it is possible to finely apply the optimum sound speed to each section, thereby further improving the accuracy of the delay data. In particular, since the skin layer has a sound speed considerably different from that of the fat layer, it is possible to further improve the accuracy of the delay data by handling the skin layer independently. In this example, in addition to the lower boundary 92 of the fat layer 116, the upper boundary 94 is also specified in order to specify the skin layer 118. Since the skin layer 118 and the fat layer 116 have considerably different elastic moduli, it is possible to clearly identify both of them on the elastic image. Also in the segmentation example shown in FIG. 5, the propagation part inside the probe may be excluded from the segmentation.

  Next, a second embodiment will be described with reference to FIGS. In addition, regarding the content of those figures, the same code | symbol is attached | subjected to the structure same as the structure shown in FIG. 1, and the description is abbreviate | omitted.

  In FIG. 6, a sensor 130 is integrally provided on the probe 10. The sensor 130 is a detector for detecting the position and orientation of the probe in a three-dimensional space. For example, a magnetic detection system, an optical detection system, or the like can be used. When the magnetic detection method is used, a generator for generating a three-dimensional magnetic field is separately provided, and the three-dimensional magnetic field generated thereby is detected by the sensor 130. In that case, the sensor 130 includes three magnetic sensors corresponding to three directions. An output signal of the sensor 130 is sent to the read control unit 132.

  The read control unit 132 specifies the position of the scanning plane in the three-dimensional space based on the position and orientation of the probe. Then, the cross-sectional data (two-dimensional data) corresponding to the specified position is read from the volume data storage unit 134. Volume data is stored in the volume data storage unit 134. The volume data is data acquired by the X-ray CT apparatus or data acquired by the MRI apparatus. Volume data is stored in the volume data storage unit 134 via a portable medium or via a network. The cross-sectional data read from the volume data storage unit 134 is data representing a cross-section at the same position as the current scanning plane, and the data is sent to the display processing unit 30 and the boundary detection unit 42. For example, a CT tomographic image can be displayed on the display device 40. On the other hand, the data is referred to by the boundary detection unit 42, and the boundary of the fat layer is specified based on, for example, a CT tomographic image. As a result, the thickness calculator 44 measures the fat layer thickness on each of a plurality of paths corresponding to the plurality of vibration elements. The measurement result is sent to the delay data calculation unit 24.

  According to the second embodiment, it is possible to clearly identify a fat layer lacking clarity on an ultrasound image on the basis of another medical image, and based on that, the boundary of the fat layer can be accurately determined. The advantage is that it can be detected. Similar to the first embodiment, the delay data may be updated when a predetermined event occurs, or it may be updated intermittently. Further, the delay data may be updated in real time.

  FIG. 7 shows a display example according to the second embodiment. In FIG. 7, the array transducer 12 is also schematically shown together with the display screen 138. A CT tomographic image 142 is displayed on the display screen 138 along with the B-mode image 140 in this example. These images 140 and 142 represent the same cross section. By the edge detection processing on the CT tomographic image 142, the boundary 148 of the fat layer 146 is specified. In addition, an upper boundary 145 is identified as necessary. When attention is paid to the specific path 152, the area from the vibration element to the focal point 151 is divided into three sections in the illustrated example. A section 154 indicates the distance between the upper boundary 145 and the vibration element, a section 156 indicates the distance between the upper boundary 145 and the lower boundary 148, and the section 158 indicates the lower side. The distance between the boundary 148 and the focal point 151 is shown. The section 158 is a non-fat layer section, for which the representative sound speed is applied. The section 156 is a fat layer section, and the sound speed for fat is applied thereto. For the section 154, the sound speed for skin is applied as necessary, or the representative sound speed is applied. Reference numeral 144 represents a skin layer, and reference numeral 150 represents an internal tissue.

  As described above, according to the above configuration, the beam forming condition in the ultrasonic diagnostic apparatus is determined based on the image that can be clearly identified the fat layer and the like, which is obtained by a medical apparatus other than the ultrasonic diagnostic apparatus. Is possible. In particular, it is possible to realize highly accurate beam forming by specifying the fat layer thickness on each path and applying the fat sound speed thereto. Therefore, it is possible to remarkably improve the image quality of various ultrasonic images generated as a result of ultrasonic diagnosis.

  FIG. 8 shows an example of section division for electronic sector scanning. In the electronic sector scanning, all the vibration elements constituting the array transducer 160 are used. In FIG. 8, reference numeral 180 represents a skin layer, and reference numeral 181 represents a boundary between the skin layer 180 and the fat layer 182. Reference numeral 183 indicates a boundary between the fat layer 182 and the internal tissue 184. Reference numeral 162 denotes a scanning plane formed by electronic sector scanning. A plurality of paths connecting the individual vibration elements and the focal point 164 are set, and a specific path is indicated by reference numeral 166 in FIG. Focusing on the path 166, in the illustrated example, a constant depth section 168 corresponding to the skin layer 180 is fixedly set, and a section 170 corresponding to the constant depth 168 is set on each path. Is set. The size of the section 170 differs depending on each route. In this configuration, the skin layer is handled as having a constant thickness.

  The section 172 is a fat layer section, which corresponds to the distance from a point exceeding a certain thickness 168 until the boundary 183 exists. Section 174 is a non-fat layer section, which is an internal section. In calculating the fat layer data, the sound speed for fat is applied to the fat layer section 172, and the representative sound speed is applied to the non-fat layer section 174. The skin sound speed is applied to the section 170. In this example, the boundary 181 is not detected, but it may be detected. In electronic sector scanning, since the region at the apex is narrow, it is desirable to assume the skin layer as a layer having a certain thickness as described above. Of course, the distance to the lower boundary 183 may be defined as the fat layer thickness ignoring the skin layer. The boundary detection can be based on the elastic image as described above, or can be based on another medical image. In any case, by specifying the fat layer based on the tomographic image in which the fat layer can be clearly specified as compared with the B-mode image, it is possible to improve the calculation accuracy of the delay data as compared with the conventional case. In this embodiment, the fat layer is not handled as a uniform thickness, but the fat layer thickness is calculated individually for each path, so that an appropriate delay condition can be set for each path. Benefits are gained. As a result, image distortion in the ultrasonic image can be improved, and the image quality of the ultrasonic image can be improved.

10 probe, 12 array transducer, 16 ultrasonic beam, 18 transmit beamformer, 20 receive beamformer, 24 delay data calculator, 32 frame selector, 34 displacement calculator, 36 elasticity information calculator, 42 boundary detection Section, 44 thickness calculation section, 46 sound velocity table.

Claims (9)

An array transducer having a plurality of transducer elements for forming an ultrasonic beam;
Based on a fat layer reference tomographic image different from the B-mode tomographic image, which is an image representing a tissue structure on a scanning surface formed by electronic scanning of the ultrasonic beam, the beam focus and each vibration element Measuring means for individually measuring the fat layer thickness on each path between,
An arithmetic unit that calculates delay data for forming the ultrasonic beam based on a plurality of fat layer thicknesses measured on a plurality of paths corresponding to the plurality of vibration elements;
A beam former that performs beam forming based on the delay data; and
An ultrasonic diagnostic apparatus comprising: The ultrasonic diagnostic apparatus according to claim 1,
Including a storage unit storing information indicating the speed of sound for fat and the representative speed of sound;
The computing unit applies the fat sound velocity to the fat layer section specified as the fat layer thickness on each path, and applies the representative sound speed to all or a part of the other sections. To calculate the delay data,
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 2,
The storage unit further stores information indicating the sound velocity for skin,
The other section includes a skin layer section, and an inner section between the lower surface of the fat layer and the beam focus,
The calculation unit applies the sound speed for skin to the skin layer section, and applies the representative sound speed to the internal section.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
Including tissue elasticity image forming means for forming a tissue elasticity image representing tissue elasticity as the fat layer reference tomographic image based on the received data obtained from the scanning plane;
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 4.
Including selection means for selecting a tissue elasticity image to be referred to when calculating the delay data based on the received data,
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
Means for forming a non-ultrasonic tomographic image by acquiring cross-sectional data corresponding to the scanning plane from volume data acquired by another medical device;
The fat layer reference tomographic image is the non-ultrasonic tomographic image,
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
In parallel with the sequential formation of the scanning plane, the fat layer reference tomographic images are sequentially formed, and the delay data is sequentially updated in real time.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
The measuring means includes
First detection means for detecting a lower boundary line of the fat layer on the fat layer reference tomographic image;
Second detection means for detecting an upper boundary line of the fat layer on the fat layer reference tomographic image;
Including
The plurality of fat layer thicknesses are measured as a distance between the lower boundary line and the upper boundary line;
An ultrasonic diagnostic apparatus. Individually measuring the fat layer thickness on each path between the beam focus and each vibration element based on the fat layer measurement data representing the tissue structure in the living body;
A delay for forming the ultrasonic beam based on a plurality of fat layer thicknesses corresponding to the plurality of vibration elements, a sound speed of ultrasonic waves in the fat layer, and a general sound speed of ultrasonic waves in a living tissue A process of calculating data;
Providing the delay data to the beamformer;
Forming at least one of a transmission beam and a reception beam by delay processing by the beam former;
A beam forming method comprising:

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