JP2009095665A - Ultrasonic diagnostic method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable microstructures, continuous surfaces, and speckles to be distinguished, which cannot be distinguished by a conventional display. <P>SOLUTION: An ultrasonograph provided herein is characterized not only by sending ultrasonic waves to a subject but also by having an ultrasonic probe arranged with a plurality of elements which output received signals by receiving ultrasonic signals reflected by the subject, an RF image generation means generating RF data by focusing on a delay based on one or more preset provisional sonic speed against actual ultrasonic speed sent toward the subject, a phase image generation means generating a phase image from the RF data generated by the RF image generating means, a display image generation means generating a display image displaying the phase image and the amplitude image generated by the RF data together, and a display means displaying the display image. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an ultrasonic diagnostic method and apparatus, and more particularly to a technique for visualizing in order to determine the size, shape, and properties of a reflector based on the amplitude / phase change characteristics depending on the assumed sound speed at the time of image generation.

  Conventionally, a tomographic image of a subject is acquired using ultrasonic waves and used for medical diagnosis. At this time, when generating an ultrasonic image from the received ultrasonic signal, it is necessary to set (assuming) the sound speed for generating image data. However, if the set assumed sound speed is different from the actual sound speed, the image quality is reduced. In response to this problem, various techniques have been proposed in order to generate an image at an optimum assumed sound speed.

  For example, the received signal is delayed by one of the delay data based on the average sound speed of the living body, and the other is delayed by the delay data based on the sound speed different from the average sound speed of the living body, separately imaged, It is known that a user determines an optimum assumed sound speed by simultaneously displaying two different types of images on a monitor (see, for example, Patent Document 1).

  In addition to the determination of the optimum sound speed, a technique for displaying and using information obtained by comparing images of different assumed sound speeds has been proposed.

Regarding this, for example, the speckle is reduced by calculating the coherence degree as a ratio of the amplitude of the coherently added signal and the amplitude of the non-coherently added signal (for example, see Patent Document 2), coherent, etc. Known is a signal in which a coherent signal is suppressed when there is a predetermined degree of similarity between the added signal and the non-coherent added signal (see, for example, Patent Document 3).
JP 2003-10180 A JP-A-11-151241 Special Table 2002-534184

  However, all of the above conventional ones display information obtained at different hypothetical sound speeds, and only speckles and other signals can be distinguished, but among other signals, they are continuous with microstructures. There is a problem that surface signals cannot be distinguished. For example, in the case of using the above-described coherent signal, it is difficult to distinguish between a microstructure signal and a continuous surface signal in the coherent signal, even though the coherent signal can be distinguished from the non-coherent signal.

  The present invention has been made in view of such circumstances, and could not be distinguished even when the amplitude is the same and the shape is similar, or the degree of coherence was used, which could not be distinguished by conventional display. Another object of the present invention is to provide an ultrasonic diagnostic method and apparatus capable of distinguishing a continuous structure and speckle from a microstructure.

  In order to achieve the object, the invention according to claim 1 transmits an ultrasonic wave toward the subject and outputs a reception signal by receiving an ultrasonic signal reflected from the subject. RF data is generated by focusing with an ultrasonic probe in which a plurality of elements are arranged and a delay based on one or more types of assumed sound speeds set in advance with respect to the actual sound speed of ultrasonic waves transmitted to the subject. A display image in which the phase image generation unit that generates a phase image from the RF data generated by the RF image generation unit, and the phase image and the amplitude image generated from the RF data are arranged side by side. There is provided an ultrasonic diagnostic apparatus comprising display image generation means for generating and display means for displaying the display image.

  As a result, by displaying phase images based on various different assumed sound velocities together with amplitude images, it has become possible to distinguish minute structures, continuous surfaces and speckles that could not be distinguished by conventional display.

  Similarly, in order to achieve the above object, the invention according to claim 2 transmits an ultrasonic wave toward the subject and receives an ultrasonic signal reflected from the subject. An ultrasonic probe in which a plurality of elements that output signals are arranged, and a focus based on a delay based on one or more hypothetical sound speeds that are preset with respect to the actual sound speed of the ultrasonic waves that are transmitted toward the subject. RF image generating means for generating RF data, phase image generating means for generating a phase image from the RF data generated by the RF image generating means, a display image for displaying the phase image, and an amplitude generated from the RF data Provided is an ultrasonic diagnostic apparatus comprising display image generation means for generating a display image for displaying an image, display means for switching and displaying the phase image and the amplitude image.

  As a result, even if the phase image and the amplitude image are switched and displayed, it is possible to distinguish between the minute structure, the continuous surface, and the speckle.

  According to a third aspect of the present invention, the phase image shows phase information, a scan direction differential value, a waveform, or a waveform with normalized amplitude.

  Thereby, it becomes easy to see a display image, and it becomes easier to distinguish a minute structure, a continuous surface, and speckle.

  According to a fourth aspect of the present invention, the phase image has a scan direction resolution equal to or greater than an element interval.

  Thereby, the display image has higher resolution, and the microstructure, the continuous surface, and the speckle are more easily distinguished.

  According to a fifth aspect of the present invention, the phase image is generated from a plurality of frames.

  According to a sixth aspect of the present invention, the plurality of frames are obtained by a device capable of generating RF data of two sound lines or more in the scan direction by one transmission.

  According to a seventh aspect of the present invention, the phase image is generated from a signal generated by changing a plurality of the assumed sound speeds from one transmission.

  As a result, images at each sound velocity are not shifted between frames, and processing at a high frame rate is possible.

  In addition, according to an eighth aspect of the present invention, the display means displays the phase image alone or in a plurality.

In addition, according to a ninth aspect of the present invention, the display means displays the phase image and the amplitude image as they are or with different colors, superimposed or side by side, or individually or in a plurality.

  According to a tenth aspect of the present invention, the display unit modulates the luminance and color of the amplitude image according to the phase image, and displays one or a plurality of the amplitude images.

  Further, as shown in claim 11, in the ultrasonic diagnostic apparatus according to claims 1 to 10, the display mode of the display means is displayed as a normal display mode and a plurality of images superimposed or arranged, Or it has the mode switching means which switches the display mode to display individually or in multiple.

  As described above, by providing the display means and performing various display methods, it becomes easier to distinguish the minute structure or the continuous surface or the speckle.

  Similarly, in order to achieve the above-mentioned object, the invention according to claim 12 transmits an ultrasonic wave from an ultrasonic probe in which a plurality of elements are arranged toward the subject and reflects it from the subject. Receiving the ultrasonic signal, and generating RF data by focusing with a delay based on one or more kinds of assumed sound speeds preset with respect to the actual sound speed of the ultrasonic waves to be transmitted to the subject, Generating a phase image from the RF data generated by the RF image generation means, generating a display image in which the phase image and the amplitude image generated from the RF data are arranged side by side, and displaying the generated display image An ultrasonic diagnostic method is provided.

  As a result, by displaying phase images based on various different assumed sound velocities together with amplitude images, it has become possible to distinguish minute structures, continuous surfaces and speckles that could not be distinguished by conventional display.

  Similarly, in order to achieve the above object, the invention according to claim 13 transmits an ultrasonic wave from an ultrasonic probe in which a plurality of elements are arranged toward the subject, and reflects it from the subject. Receiving the ultrasonic signal, and generating RF data by focusing with a delay based on one or more kinds of assumed sound speeds preset with respect to the actual sound speed of the ultrasonic waves to be transmitted to the subject, A phase image is generated from the RF data generated by the RF image generation means, a display image in which the phase image and the amplitude image generated from the RF data are arranged side by side is generated, and the phase image and the amplitude image are switched. Provided is an ultrasonic diagnostic method characterized by displaying.

  This also makes it possible to distinguish between minute structures, continuous surfaces, and speckles that could not be distinguished by conventional display.

  As described above, according to the present invention, phase images based on various different assumed sound velocities are displayed together with amplitude images, thereby distinguishing microstructures, continuous surfaces, and speckles that could not be distinguished by conventional display. It becomes possible to do.

  Hereinafter, an ultrasonic diagnostic method and apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

  The present invention relates to a phase change in the scanning direction (arrangement direction of transducers of an ultrasonic probe) of a microstructure, a continuous surface / line, and a speckle, and an ultrasonic wave set when a determination image is generated from a received ultrasonic image. The phase information and amplitude information at multiple hypothetical sound speeds are displayed so that the difference in phase change when changing the sound wave speed (assumed sound speed) can be visualized, and the user can judge microstructures, continuous surfaces / lines, and speckles. It is something that can be done.

  Note that the ultrasonic sound speed that is set by changing a plurality of predetermined increments at the time of image generation is referred to as the set sound speed or the assumed sound speed with respect to the actual ultrasonic sound speed (actual sound speed) transmitted to the subject.

  The present invention pays attention to the difference in the phase change characteristics of the microstructure signal, the continuous surface / line signal, and the speckle signal when the assumed sound speed is changed.

  Specifically, the phase change characteristic will be described in detail later, but simply speaking, it is as follows.

  First, in the case of a minute structure, when the assumed sound speed is smaller (slower) than the actual sound speed (hereinafter also referred to as the optimum sound speed), the phase is convex upward in the scanning direction (the arrangement direction of the transducers of the ultrasonic probe) ( The slope becomes steeper as the assumed sound speed is closer to the optimum sound speed, and when the assumed sound speed is greater (faster) than the optimum sound speed, the phase changes downward (convex) in the scan direction. The slope becomes steeper as it approaches the optimum sound speed.

  In the case of a continuous surface / line, the phase is uniform regardless of the assumed sound speed.

  In the case of speckle, the phase changes randomly depending on the assumed sound speed.

  In the following embodiment, determination of a microstructure, a continuous surface / line, and speckle is performed based on these facts.

  FIG. 1 is a system configuration diagram showing a schematic configuration of an embodiment of an ultrasonic diagnostic apparatus according to the present invention.

  As shown in FIG. 1, the ultrasound diagnostic apparatus 1 captures and displays an ultrasound image of a diagnosis part of a subject using ultrasound, and includes an ultrasound probe 10, a transmission / reception unit 12, and scanning control. Unit 14, AD conversion unit 16, RF image generation unit 18, phase image generation unit 20, display image generation unit 22, monitor 24, and mode switching means 26.

  The ultrasonic probe 10 transmits ultrasonic waves toward a diagnosis site in the body of the subject and receives ultrasonic waves reflected in the body. The ultrasonic probe 10 of the present embodiment includes a plurality of ultrasonic transducers constituting a one-dimensional ultrasonic transducer array, and each ultrasonic transducer is a vibration in which electrodes are formed at both ends of a piezoelectric element such as PZT, for example. Consists of children. This electrode is connected to the transmitting / receiving unit 12 by a signal line. When a voltage is applied to each electrode, the vibrator generates ultrasonic waves. Further, when the transducer receives the reflected ultrasonic wave, it generates an electrical signal, which is output as a received signal.

  The transmission / reception unit 12 applies an ultrasonic transmission signal to the ultrasonic probe 10 to generate an ultrasonic wave from the vibrator, and transmits the ultrasonic wave based on the delay given from the scanning control unit 14. Then, the reflected ultrasonic waves are received and the reception signals of the respective elements output from the ultrasonic probe 10 are amplified as they are (without receiving focus).

  The AD conversion unit 16 receives the ultrasonic reception signal from the transmission / reception unit 12, performs AD conversion, and passes it to the RF image generation unit 18. The RF image generation unit 18 stores the reception data received from the AD conversion unit 16. The RF image generation unit 18 uses various stored sound speeds (actual sound speeds (actual sound speeds) to be transmitted to the subject as described above from the stored reception data of each element, as will be described in detail later. Is received and focused with a delay based on the assumed sound speed, and RF data based on each assumed sound speed is generated.

  The phase image generation unit 20 generates a phase image for determining microstructures, speckles, and boundaries from images (RF data) generated at various sound speeds (assumed sound speeds).

  The display image generation unit 22 generates a display image to be displayed on the monitor 24 from the image (RF data) generated by the RF image generation unit 18 and the phase image generated by the phase image generation unit 20. It is. The mode switching means 26 is for switching the display mode of the image on the monitor 24.

  In this embodiment, when reconstructing an image from received data, the difference in phase change characteristics when the assumed sound speed is changed variously with respect to the actual sound speed is visualized, and the user can make a microstructure, a continuous surface / line, The speckle can be determined. Before describing the operation of the ultrasonic diagnostic apparatus 1, the phase change characteristic when the assumed sound speed is changed will be described.

  2 to 9 are graphs showing the phase change characteristics when the assumed sound speed is changed.

  Each graph shows the phase change characteristic when the assumed sound speed is changed from 1400 [m / s] to 1620 [m / s] in steps of 40 [m / s] or 20 [m / s]. In the scan direction (X position) and the vertical axis as the phase.

  FIG. 2 is a graph showing the phase change characteristic depending on the assumed sound speed of the microstructure signal at the assumed sound speed of 1400 [m / s] to 1500 [m / s], and FIG. 3 is the assumed sound speed of 1500 [m / s]. It is a graph which shows the phase change characteristic depending on the assumed sound speed of the microstructure signal in ˜1620 [m / s].

  In the case of FIG. 2 where the assumed sound speed is 1400 [m / s] to 1500 [m / s], the graph of the assumed sound speed 1500 [m / s] has a positive slope in the vicinity of the X position 100 to 120. The graphs in which the assumed sound speed is smaller than 1500 [m / s] (that is, the assumed sound speed is slower) are all lower right, and the inclination is steeper as the assumed sound speed is closer to 1500 [m / s]. The inclination becomes gentler as the sound speed becomes slower than 1500 [m / s].

  Further, in the case of FIG. 3 in which the assumed sound speed is 1500 [m / s] to 1620 [m / s], the graphs are all rising to the right in the vicinity of the X positions 100 to 120. The inclination is the largest when the assumed sound speed is 1500 [m / s], and the inclination becomes gentler as the assumed sound speed becomes larger than 1500 [m / s].

  The shape of such a graph of FIG.2 and FIG.3 is considered to show that the micro structure exists in X position 100-120 vicinity.

  FIG. 4 is a graph showing the phase change characteristic depending on the assumed sound speed of the surface signal at the assumed sound speed of 1400 [m / s] to 1480 [m / s], and FIG. 5 is the assumed sound speed of 1540 [m / s] to 1620. It is a graph which shows the phase change characteristic depending on the assumed sound speed of the surface signal in [m / s].

  As can be seen from FIGS. 4 and 5, the phase does not change much even if the assumed sound speed is changed in the vicinity of the X positions 100 to 130 and 150 to 180. This is considered to indicate that a surface (continuous surface) exists in the portion.

FIG. 6 is a graph showing the phase change characteristic depending on the assumed sound speed of speckle at the assumed sound speed of 1400 [m / s] to 1480 [m / s], and FIG. 7 shows the assumed sound speed of 1540 [m / s] to 1
It is a graph which shows the phase change characteristic depending on the assumed sound speed of the speckle in 620 [m / s]. As shown in FIGS. 6 and 7, in the case of speckle, the phase changes randomly when the assumed sound speed is changed.

  FIG. 8 is a graph showing the amplitude change characteristic depending on the assumed sound speed of the microstructure at an assumed sound speed of 1400 [m / s] to 1500 [m / s], and FIG. 9 is an assumed sound speed of 1500 [m / s]. It is a graph which shows the amplitude change characteristic by the assumed sound speed of the microstructure signal in 1620 [m / s].

  As can be seen from FIGS. 8 and 9, the graphs showing the change in the amplitude of the microstructure are both mountain-shaped (convex upward) graphs having a peak (maximum value) near the X position 110, and an assumed sound speed 1500. The amplitude value is maximum at [m / s], and the maximum amplitude value increases as the assumed sound speed approaches 1500 [m / s], and the shape is steep.

  Next, the reason why the phase change of the microstructure when the assumed sound speed is changed has the characteristics shown in the graphs of FIGS.

In FIG. 10, it is assumed that the ultrasonic wave reflected from the point A (0, z ₀ ) at the sound velocity V ₀ is observed by the element (vibrator) at the position X in the ultrasonic probe 10 at the time t after reflection. Then, this time t is calculated as the following equation (1).

t = sqrt (z ₀ ² + X ² ) / V ₀ (1)
In Equation (1), sqrt () means taking the square root of the value in ().

  Further, in FIG. 10, it is assumed that the ultrasonic wave reflected from the point A ′ (x, z) at the sound velocity V is observed at the time t after reflection by the element (vibrator) at the position X in the ultrasonic probe 10. . Similar to the above, this time t is expressed by the following equation (2).

t = sqrt {z ² + (X−x) ² } / V ... (2)
The trajectory of the point A ′ when the curves given by the equations (1) and (2) touch each other in the (X, t) plane is given by the following equation (3).

z ² = x ² × {V ² / (V ₀ ² −V ² )} + z ₀ ² V ² / V ₀ ² (3)
Point A ′ indicates a position where the signal becomes stronger when the phase is matched and added as the assumed sound speed V with respect to the optimum sound speed (actual sound speed).

From equation (3), the locus of the point A ′ (x, z) is an ellipse centered on the origin when V> V ₀ , and a hyperbola centered on the origin when V <V ₀ . In the B-mode image, since the downward direction of the z-axis is upward, the elliptical trajectory centered on the origin when V> V ₀ is concave, and the hyperbola centered on the origin when V <V ₀ is used. The locus is convex.

FIG. 11 shows a state where the curves given by the equations (1) and (2) are in contact with each other on the (X, t) plane. FIG. 11A shows the case of V <V ₀ , the solid line J shows the reflected wave from the point A, and the broken line H1 shows the reflected wave from the point A ′ when it is on the right side of the z axis as shown in FIG. Represents. A broken line H2 represents a reflected wave from a point on the left side of the z axis in FIG. Since V <V ₀ at this time, the reflected wave from the point A ′ has a larger time t for the same X position, and therefore the broken line H1 (H2) appears above the solid line J.

FIG. 11B shows a case where V = V ₀ , and FIG. 11C shows a case where V> V ₀ . When V approaches V ₀ , the broken line H approaches the solid line J, and when V = V ₀ , the broken line H coincides with the solid line J. In the case of FIG. 11C, the broken line appears on the lower side of the solid line, contrary to FIG.

  From these figures, it can be intuitively understood that the locus of the point A ′ (x, z) where the broken line touches the solid line has the tendency as described above.

  In the model described here, the observed reflected wave is simply a line. However, in reality, the waveform has a width in the t direction and there is a difference in intensity in the X direction. There is a need to. Moreover, in this model, for the sake of simplicity, reflection from point A and point A ′ is performed simultaneously, but actually, it is necessary to consider the time from when an ultrasonic wave is transmitted to each point to reflection. There is.

  Next, the operation of the RF image generation unit 18 in the apparatus configuration of FIG. 1 will be described along the flowchart of FIG.

  As described above, the RF image generation unit 18 generates images (RF data) from data obtained at various sound speeds by changing the assumed sound speed.

  First, in step S100 in FIG. 12, the initial value of the assumed sound speed to be changed in various ways is set. This value is not particularly limited and may be determined as appropriate. For example, it may be determined as 1400 [m / s] as in the example of FIG.

  Then, a signal is sent to the ultrasonic probe 10 from the transmission / reception unit 12 controlled by the scanning control unit 14 based on the set initial value, and data based on the assumed initial sound velocity value is acquired and sent to the RF image generation unit 18.

  Next, in step S110, the assumed sound speed is changed by a predetermined amount by one step, and ultrasonic data based on the changed assumed sound speed is acquired. The predetermined amount of one step is not particularly limited, and may be 40 [m / s], 10 [m / s], 20 [m / s], as in the example of FIG. The assumed sound speed is changed by a fixed amount.

  Next, in step S120, the obtained hypothetical sound speed data are added with their phases matched to generate RF (Radio Frequency) data. This RF data includes both amplitude information and phase information. In this way, RF data is created with images at all assumed sound speeds.

  In step S130, it is determined whether or not image generation has been completed. If it has not been completed, the process returns to step S110, and the assumed sound speed is changed by one step and image generation is continued. The end of image generation is determined by whether or not the processing for all assumed sound velocities has been completed. For example, it may be determined in advance by determining in advance how many steps the assumed sound velocity is to be terminated and counting the number of times.

  Next, the operation of the phase image generation unit 20 will be described.

  FIG. 13 is a flowchart showing the operation of the phase image generation unit 20.

  First, in step S200 of FIG. 13, an initial value of the assumed sound speed is set. This is the same as step S100 in FIG.

  Next, in step S210, the assumed sound speed is changed by one step. This is also the same as step S110 of FIG. 12 described above, and the predetermined amount of this one step is not particularly limited, and may be 40 [m / s] as in the example of FIG. s] or 20 [m / s], and the assumed sound speed is changed by a predetermined amount.

  Next, in step S220, RF data is received from the RF image generation unit 18, and a phase image is generated therefrom. This phase image may be simply an image of phase information, but in order to eliminate difficulty in viewing due to inversion at ± 180 °, the focus is now on the phase change in the scan direction. May be used. Note that the phase unevenness change of the microstructure has a substantially constant slope determined by the difference between the assumed sound speed and the actual sound speed in the first derivative value, and a continuous value in the second derivative value.

  The phase image may be the waveform itself, or a normalized waveform obtained by dividing the waveform by the amplitude in order to erase the amplitude information.

  Next, in step S230, it is determined whether or not the generation of the phase image has been completed. If there is still RF data for which a phase image should be generated, the process returns to step S210, and the assumed sound speed is changed by one step to generate the RF image. The next RF data is received from the unit 18 and the generation of the phase image is continued.

  Then, when the processing for all changed assumed sound velocities is completed, the phase image generation processing is terminated.

  In the display image generation unit 22, for one or more types of assumed sound speeds, an amplitude image generated from the RF image (RF data) generated by the RF image generation unit 18, a phase image generated by the phase image generation unit 20, and Are arranged side by side as shown in FIG. 14, for example, and a display image to be displayed on the monitor 24 is generated.

  At this time, the result may be logarithmically compressed, gain / DR (dynamic range) / STC (depth weighting) / gray map adjustment may be performed, and scan conversion may be performed to generate a display image.

  In addition, the type of assumed sound speed, the arrangement of each image, and the size of each display image may be selectable by the user. For example, as shown in FIG. 15 or FIG. 16, the amplitude image may be displayed one larger, and a plurality of phase images may be displayed side by side.

  Here, as the amplitude image, for example, an image at a standard assumed sound speed of 1540 [m / s] or an image at an optimal sound speed obtained by a well-known method as disclosed in, for example, Japanese Patent Laid-Open No. 8-317926 is selected. You may make it do.

  Further, as the phase image, a plurality of images may be selected centering on the image at the standard assumed sound speed of 1540 [m / s] or the optimum sound speed obtained by the known method.

  As described above, this embodiment pays attention to the phase unevenness characteristic of the microstructure in the scan direction and the difference in the phase change of the microstructure, continuous surface / line, and speckle when the assumed sound speed is changed. Since phase images based on various different assumed sound velocities are displayed together with amplitude images, it is possible to distinguish between minute structures, continuous surfaces, and speckles that cannot be distinguished by conventional display.

  As described above, the phase image may include not only the phase but also the scan direction differential value, the waveform, and the normalized waveform. The phase image and the amplitude image need not always be displayed side by side at the same time, and the display of the phase image and the display of the amplitude image may be switched by the mode switching unit 26, respectively.

  In addition, the conventional ultrasonic diagnostic apparatus forms transmission / reception beams at the sound ray positions of the element spacing, generates RF data, generates amplitude data, and then generates amplitude data by interpolating the sound rays between the elements. In general, however, a configuration in which a display image is formed is used, but recently, a configuration in which a transmission / reception beam is formed also on sound rays between elements and RF data is generated has been seen.

  In the apparatus configuration according to the present embodiment, phase images can be displayed with a resolution equal to or higher than the element interval in the scan direction, which is suitable for determining the unevenness characteristic of the microstructure.

  In the embodiment described above, the phase image is generated from a single frame, but a plurality of frames may be used. Although the speckle phase changes randomly between frames, it shows a constant value for microstructures and continuous surfaces. However, a high frame rate is required to capture the microstructure signal in a plurality of frames.

  FIG. 17 shows a comparison of the S / N ratio between the amplitude image after averaging the plurality of frames and the determination image.

  In FIG. 17, D is a determination image, and A is an amplitude image. FIG. 17 shows the result of scanning the SN ratio after averaging for the number of used frames ± 16 (total of 32) in order to change the frame interval. The wider the frame interval on the horizontal axis, the larger the decimation number. It is shown that.

  It can be seen from the graph of FIG. 17 that when the frame interval is wide, the SN ratio of the determination image and the amplitude image is approximately the same, but when the frame interval is narrow, the difference is large and is approximately 1.3 times. In other words, there is a characteristic that the speckle change with respect to the microstructure signal is larger than the amplitude change, and from this characteristic, it is possible to obtain a determination image having a higher SN than the amplitude image by using a plurality of frames with a high frame rate. Show.

  According to the graph of FIG. 17, by averaging the phase images of a plurality of frames under the condition of a high frame rate, it is possible to more suitably discriminate the uneven change and the speckle random change characteristic of the microstructure signal in the scanning direction. It can be seen that it can be visualized separately. Similarly, by averaging the phase images of a plurality of frames, it becomes possible to visualize the difference in the phase change characteristics of the microstructure signal, the continuous surface signal, and the speckle depending on the assumed sound speed.

  Recent software-based ultrasonic apparatuses have received signals as digital data, and can generate images at various assumed sound speeds using received data obtained from the same transmission (one transmission). It is coming. Also, analog bases have been able to do the same with high-performance circuit configurations.

  Therefore, a plurality of frames may be obtained using received data obtained by a device that can generate RF data of two or more sound rays in the scan direction by one transmission.

  The apparatus configuration in this embodiment is useful for the following two reasons. The first point is that RF data at various assumed sound speeds can be displayed without any shift between frames, and in particular, it is possible to solve that the difference in appearance due to the frame position of the microstructure signal is large. The point is that a plurality of frames can be used under the high frame rate condition described above.

In the embodiment described above, the case where the transducer array of the ultrasonic probe is one-dimensional has been described, but the present invention is of course applicable to a two-dimensional case. In the two-dimensional case, since the phase-matching addition is performed based on the two-dimensional position of the vibrator, the microstructure signal shows a two-dimensional phase unevenness change in which the inclination changes depending on the assumed sound speed, The signal shows a two-dimensionally uniform phase, the continuous line signal shows a uniform phase in the direction along the line, a phase unevenness change in the direction perpendicular to the line, and speckles are two-dimensionally random Shows a significant phase change. For example, by displaying a phase image in each of the two-dimensional scan directions or a three-dimensional phase image, it is possible to distinguish a microstructure, a continuous surface, and speckle with better SN than in the case of one dimension. Further, in the above-described embodiment, only the case where one type of RF data is used as the transmission / reception frequency of the ultrasonic wave has been described. include. For example, the microstructure signal shows the same phase unevenness change in the scan direction even if the frequency is different, but the speckle is a result of interference, so if the frequency is different, the method of phase change in the scan direction is different. By displaying the phase images side by side, it becomes easier to distinguish the fine structure and the speckle.

  The ultrasonic diagnostic method and apparatus of the present invention have been described in detail above, but the present invention is not limited to the above examples, and various improvements and modifications can be made without departing from the spirit of the present invention. Of course it is good.

1 is a system configuration diagram showing a schematic configuration of an embodiment of an ultrasonic diagnostic apparatus according to the present invention. It is a graph which shows the phase change characteristic depending on the assumed sound speed of the microstructure signal in the assumed sound speed of 1400 [m / s] to 1500 [m / s]. It is a graph which shows the phase change characteristic by the assumption sound speed of the microstructure signal in assumption sound speed 1500 [m / s]-1620 [m / s]. It is a graph which shows the phase change characteristic by the assumption sound speed of the surface signal in assumption sound speed 1400 [m / s]-1480 [m / s]. It is a graph which shows the phase change characteristic by the assumption sound speed of the surface signal in assumption sound speed 1540 [m / s]-1620 [m / s]. It is a graph which shows the phase change characteristic according to the assumed sound speed of speckle in assumption sound speed 1400 [m / s]-1480 [m / s]. It is a graph which shows the phase change characteristic depending on the assumed sound speed of the speckle in the assumed sound speed of 1540 [m / s] to 1620 [m / s]. It is a graph which shows the amplitude change characteristic depending on the assumed sound speed of the microstructure in the assumed sound speed of 1400 [m / s] to 1500 [m / s]. It is a graph which shows the amplitude change characteristic according to the assumed sound speed of the microstructure signal in the assumed sound speed of 1500 [m / s] to 1620 [m / s]. It is explanatory drawing which shows an ultrasonic signal reception state. It is explanatory drawing which shows a mode that the curve given by Formula (1) and Formula (2) touches in the (X, t) plane, (a) is a case where V <V ₀ , (b) This is a case where V = V ₀ , and (c) is a case where V> V ₀ . It is a flowchart which shows the effect | action of an RF image generation part. It is a flowchart which shows the process which produces | generates the phase image in a phase image generation part. It is explanatory drawing which shows an example of the image display method. It is explanatory drawing which similarly shows another example of the image display method. It is explanatory drawing which similarly shows another example of the image display method. It is a graph which compares and shows the SN ratio of the amplitude image after several frame average, and the determination image.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Ultrasound diagnostic apparatus, 10 ... Ultrasonic probe, 12 ... Transmission / reception part, 14 ... Scan control part, 16 ... AD conversion part, 18 ... RF image generation part, 20 ... Phase image generation part, 22 ... Display image generation part 24 ... monitor, 26 ... mode switching means

Claims (13)

An ultrasonic probe in which a plurality of elements that transmit an ultrasonic wave toward the subject and output a reception signal by receiving an ultrasonic signal reflected from the subject are arranged;
RF image generation means for generating RF data by focusing with a delay based on one or more types of assumed sound speeds preset with respect to the actual sound speed of the ultrasonic waves transmitted toward the subject;
Phase image generation means for generating a phase image from RF data generated by the RF image generation means;
Display image generating means for generating a display image in which the phase image and the amplitude image generated from the RF data are arranged side by side;
Display means for displaying the display image;
An ultrasonic diagnostic apparatus comprising: An ultrasonic probe in which a plurality of elements that transmit an ultrasonic wave toward the subject and output a reception signal by receiving an ultrasonic signal reflected from the subject are arranged;
RF image generation means for generating RF data by focusing with a delay based on one or more types of assumed sound speeds preset with respect to the actual sound speed of the ultrasonic waves transmitted toward the subject;
Phase image generation means for generating a phase image from RF data generated by the RF image generation means;
Display image generating means for generating a display image for displaying the phase image and a display image for displaying an amplitude image generated from the RF data;
Display means for switching and displaying the phase image and the amplitude image;
An ultrasonic diagnostic apparatus comprising:   The ultrasonic diagnostic apparatus according to claim 1, wherein the phase image shows phase information, a differential value in a scanning direction, a waveform, or a waveform with normalized amplitude.   The ultrasonic diagnostic apparatus according to claim 1, wherein the phase image has a resolution in a scanning direction equal to or greater than an element interval.     The ultrasonic diagnostic apparatus according to claim 1, wherein the phase image is generated from a plurality of frames.   The ultrasonic diagnostic apparatus according to claim 5, wherein the plurality of frames are obtained by an apparatus capable of generating RF data of two sound rays or more in the scanning direction by one transmission.   The ultrasound diagnostic apparatus according to claim 1, wherein the phase image is generated from a signal generated by changing a plurality of the assumed sound velocities from one transmission.   The ultrasonic diagnostic apparatus according to claim 1, wherein the display unit displays the phase image singly or in plural.   The super display according to any one of claims 1 to 8, wherein the display means displays the phase image and the amplitude image as they are or in a different color, superimposed or arranged in a single or plural number. Ultrasonic diagnostic equipment.   The ultrasonic diagnostic apparatus according to claim 1, wherein the display unit modulates luminance and color of the amplitude image in accordance with the phase image, and displays the single or a plurality of the amplitude images. .   The ultrasonic diagnostic apparatus according to any one of claims 1 to 10, further comprising: a normal display mode as a display mode of the display means; a display mode in which a plurality of images are displayed in a superimposed or side-by-side manner; or a single or a plurality of display modes. An ultrasonic diagnostic apparatus comprising mode switching means for switching between the two. While transmitting an ultrasonic wave from the ultrasonic probe in which a plurality of elements are arranged toward the subject, receiving an ultrasonic signal reflected from the subject,
RF data is generated by focusing with a delay based on one or more hypothetical sound speeds set in advance with respect to the actual sound speed of the ultrasonic wave transmitted toward the subject,
A phase image is generated from the RF data generated by the RF image generation means,
Generating a display image in which the phase image and the amplitude image generated from the RF data are arranged side by side;
An ultrasonic diagnostic method comprising displaying the generated display image. While transmitting an ultrasonic wave from the ultrasonic probe in which a plurality of elements are arranged toward the subject, receiving an ultrasonic signal reflected from the subject,
RF data is generated by focusing with a delay based on one or more hypothetical sound speeds set in advance with respect to the actual sound speed of the ultrasonic wave transmitted toward the subject,
A phase image is generated from the RF data generated by the RF image generation means,
Generating a display image in which the phase image and the amplitude image generated from the RF data are arranged side by side;
An ultrasonic diagnostic method, wherein the phase image and the amplitude image are switched and displayed.

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