JP2014064856A - Ultrasonic examination apparatus, signal processing method of ultrasonic examination apparatus and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic examination apparatus capable of obtaining a suitable sound velocity value for every region in an image in a short time, and constructing a high-accuracy ultrasonic image without lowering a frame rate.SOLUTION: An ultrasonic examination apparatus includes: a region setting unit for setting a plurality of regions in an examination object; a sound velocity calculating unit for calculating the sound velocity of the regions; a sound velocity obtaining unit for obtaining a preliminary sound velocity on the basis of the sound velocity in the regions within a predetermined range from a region of interest; and an image quality determination unit for determining the image quality of the region of interest in the case of being based upon the preliminary sound velocity. When the determination result of the image quality determination unit is good, the preliminary sound velocity obtained by the sound velocity obtaining unit is adopted as the sound velocity of the region of interest, and when the determination result is not good, the sound velocity of the region of the interest is calculated by the sound velocity calculating unit.

Description

  The present invention relates to an ultrasonic inspection apparatus that performs imaging of an inspection target such as an organ in a living body by transmitting and receiving an ultrasonic beam, and generates an ultrasonic image used for inspection and diagnosis of the inspection target. The present invention relates to a signal processing method and program for an ultrasonic inspection apparatus.

  Conventionally, in the medical field, an ultrasonic inspection apparatus such as an ultrasonic diagnostic imaging apparatus using an ultrasonic image has been put into practical use. In general, this type of ultrasonic inspection apparatus has an ultrasonic probe (ultrasonic probe) including a plurality of elements (ultrasonic transducers), and an apparatus main body connected to the ultrasonic probe. The ultrasonic probe transmits the ultrasonic beam from the multiple elements of the ultrasonic probe toward the inspection object (subject), receives the ultrasonic echo from the subject, and receives the ultrasonic echo. An ultrasonic image is generated by electrically processing the ultrasonic echo signal thus processed in the apparatus main body.

  In an ultrasonic inspection apparatus, when generating an ultrasonic image, an ultrasonic wave is focused on a region to be inspected of a subject, for example, an organ in a living body or a lesion in the organ from a plurality of elements of the probe. Transmits a beam and receives ultrasonic echoes from the surface or interface of a reflector in the examination target area, for example, an organ or a lesion, via multiple elements, but is reflected by the same reflector. Are reflected by the reflector located at the focal position of the ultrasonic beam transmitted from the transmitting element, and reflected by the same reflector with respect to the ultrasonic echo signal received by the transmitting element. Since the ultrasonic echo signals received by other elements different from the transmitting element are delayed, the ultrasonic echo signals received by a plurality of elements are subjected to A / D (analog / digital) conversion to obtain element data and After the element And reception focusing processing over data, and generates an ultrasound image based on the generated sound ray signals by phasing and adding the combined phase, thus obtained sound ray signal or delay correction to.

By the way, in the ultrasonic inspection apparatus, when generating an ultrasonic image, the ultrasonic image is generated on the assumption that the sound speed in the living body of the subject is constant. However, in the actual living body, the sound speed value changes depending on the properties of the tissue in the living body, so the sound speed value varies. Due to this variation, the ultrasonic image has spatial distortion, contrast, or spatial resolution. Image quality degradation such as lowering of image quality.
On the other hand, in recent years, in order to more accurately diagnose a diagnostic part in a subject, the sound velocity value at an arbitrary diagnostic part is optimized, and such image distortion and reduction in spatial resolution are reduced. Has been made to improve.

For example, Patent Document 1 discloses a focused area setting unit that sets a focused area, a transmission focus instruction unit that causes an ultrasonic probe to transmit focus to the focused area, and an ultrasonic detection signal from the focused area. A set sound speed designating unit for designating a plurality of set sound speeds for receiving focus, a focus index calculating unit for calculating a focus index of an ultrasonic detection signal by receiving focus for each of a plurality of set sound speeds, An ultrasonic diagnostic apparatus is disclosed that includes environmental sound speed determining means for determining the environmental sound speed of a region of interest based on a focus index for each set sound speed.
Patent Document 1 discloses that an environmental sound speed is appropriately determined for each pixel level or line image level constituting an ultrasonic image based on a focus index, and a high-accuracy ultrasonic image is constructed. .

JP 2011-92686 A

  However, with the technique disclosed in Patent Document 1, an image with higher image quality than that of the conventional technique can be obtained. However, a focus index is comprehensively obtained based on a plurality of set sound speeds for each pixel level or each line image level. There is a problem that it takes time to obtain the environmental sound speed of all the pixels (lines) so that the set sound speed at which the focus index is the best is the optimum sound speed (environmental sound speed). As a result, there is a problem that the frame rate is lowered.

  An object of the present invention is to solve the above-mentioned problems of the prior art, and to obtain an appropriate sound speed value for each region in the image in a short time, and to obtain a high-accuracy ultrasonic image without reducing the frame rate. Is to provide an ultrasonic inspection apparatus, a signal processing method of the ultrasonic inspection apparatus, and a program.

  In order to achieve the above object, the present invention is an ultrasonic inspection apparatus that inspects an inspection object using an ultrasonic beam, an area setting unit that sets a plurality of areas in the inspection object, and an area A sound speed calculation unit that calculates the sound speed of the sound, a sound speed acquisition unit that acquires one of a plurality of areas as a target area, and acquires a preliminary sound speed based on the sound speed in at least one area within a predetermined range from the target area; An image quality determination unit that determines the image quality of a region of interest when based on the preliminary sound speed acquired by the sound speed acquisition unit, and if the determination result of the image quality determination unit is good, the preliminary sound speed acquired by the sound speed acquisition unit is Provided is an ultrasonic inspection apparatus that is employed as a sound speed of a region of interest, and calculates a sound speed of a region of interest by a sound speed calculation unit when a determination result is negative.

Here, it is preferable that the sound speed acquisition unit acquires the preliminary sound speed based on the sound speed in at least one region that is within a predetermined range in time and / or space from the region of interest.
Here, it is preferable that the area within the predetermined range in the space is an area close to the attention area on the same image.
In addition, it is preferable that the area within a predetermined range in the space is an area in the same partial image when the image is divided into a plurality of partial images.

Further, the region within the predetermined range in terms of time is preferably a region corresponding to the attention region in the image before the predetermined frame.
The region within a predetermined range in time is a region corresponding to a region of interest in at least one image obtained by performing a predetermined process on a plurality of images before a predetermined frame, or a plurality of predetermined frames. It is a region corresponding to a region of interest in at least one of the previous images, and the sound speed in the region is preferably a sound speed obtained by performing a predetermined process on sound speeds before a plurality of predetermined frames.
The predetermined process is preferably a process for obtaining either an average value or a median value of sound speeds before a plurality of predetermined frames.

The image quality determination unit preferably performs image quality determination based on any one of sharpness, brightness, contrast, and frequency of the image of the attention area generated based on the preliminary sound speed.
In addition, the image quality determination unit preferably performs image quality determination by comparing the image of the attention area generated based on the preliminary sound velocity with the image of the same area of the previous image.
Further, the image quality determination unit evaluates the similarity between the reference data generated based on the reception data after the phasing addition of the attention area generated based on the preliminary sound velocity and the reception data before the phasing addition, and determines the image quality. It is preferable to carry out.
Moreover, it is preferable that each element of the transducer array has an element data storage unit that stores element data output by receiving and outputting ultrasonic echoes.

  In order to achieve the above object, the present invention provides a signal processing method for an ultrasonic inspection apparatus that inspects an inspection object using an ultrasonic beam, wherein the region setting sets a plurality of areas in the inspection object. And a sound speed calculating step for calculating the sound speed of the area, and a sound speed for obtaining a preliminary sound speed based on the sound speed in at least one area within a predetermined range from the attention area, with one of the plurality of areas as the attention area. An acquisition step and an image quality determination step for determining the image quality of the region of interest based on the preliminary sound speed acquired by the sound speed acquisition step. If the determination result of the image quality determination step is good, the sound speed acquisition step is acquired. An ultrasonic inspection apparatus that employs the preliminary sound speed as the sound speed of the attention area and, if the determination result is negative, calculates the sound speed of the attention area by a sound speed calculation step To provide a signal processing method.

  In order to achieve the above object, the present invention is a program for causing a computer to perform signal processing of an ultrasonic inspection apparatus that inspects an inspection object using an ultrasonic beam, and a plurality of regions in the inspection object. An area setting step for setting the sound speed, a sound speed calculating step for calculating the sound speed of the area, and one of the plurality of areas as the attention area, and the preliminary setting based on the sound speed in at least one area within the predetermined range from the attention area A sound speed acquisition step for acquiring the sound speed, and an image quality determination step for determining the image quality of the attention area based on the preliminary sound speed acquired by the sound speed acquisition step, and if the determination result of the image quality determination step is good, The preliminary sound speed acquired in the sound speed acquisition step is adopted as the sound speed of the attention area. If the determination result is negative, the sound speed of the attention area is calculated in the sound speed calculation step. To provide an ultrasonic inspection device signal processing program, characterized in that.

  According to the present invention, the preliminary sound speed is acquired based on the sound speed value of the area within the predetermined range from the attention area, the image quality is determined when the image of the attention area is generated based on the preliminary sound speed, and the determination result is In the case of good, the preliminary sound speed is adopted as the sound speed of the region of interest, and when the determination result is negative, the sound speed is calculated by the sound speed calculation unit. Therefore, it is possible to construct a highly accurate ultrasonic image without reducing the frame rate.

It is a block diagram which shows notionally an example of a structure of the ultrasonic inspection apparatus which concerns on this invention. It is a block diagram which shows notionally an example of a structure of the sound speed determination part of the ultrasonic inspection apparatus shown in FIG. It is a schematic diagram for demonstrating an attention area | region and the area | region of the vicinity. It is a schematic diagram for demonstrating an attention area | region and the area | region of the vicinity. It is a flowchart for demonstrating operation | movement of the sound speed calculation part of the ultrasonic inspection apparatus shown in FIG. 3 is a flowchart for explaining the operation of the ultrasonic inspection apparatus shown in FIG. 1.

  An ultrasonic inspection apparatus, a signal processing method of the ultrasonic inspection apparatus, and a program according to the present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings.

FIG. 1 is a block diagram conceptually showing an embodiment of the configuration of the ultrasonic inspection apparatus of the present invention.
As shown in FIG. 1, the ultrasonic inspection apparatus 10 includes an ultrasonic probe 12, a transmission unit 14 and a reception unit 16 connected to the ultrasonic probe 12, an A / D conversion unit 18, and an element data storage unit 20. The image generation unit 24, the display control unit 26, the display unit 28, the control unit 30, the operation unit 32, the storage unit 34, the region setting unit 50, the sound speed determination unit 52, and the sound speed storage unit 54. And have.

The ultrasonic probe (ultrasonic probe) 12 has a transducer array 36 used in a normal ultrasonic inspection apparatus.
The transducer array 36 includes a plurality of elements arranged in a one-dimensional or two-dimensional array, that is, ultrasonic transducers. These ultrasonic transducers transmit an ultrasonic beam to a subject in accordance with a drive signal supplied from the transmission unit 14 when an ultrasonic image of an object to be examined (hereinafter referred to as a subject) is captured. An ultrasonic echo from the specimen is received and a reception signal (analog element signal) is output. In the present embodiment, each of the predetermined number of ultrasonic transducers forming one set among the plurality of ultrasonic transducers of the transducer array 36 generates each component of one ultrasonic beam, and sets a predetermined number of ultrasonic transducers. The ultrasonic transducer generates one ultrasonic beam that is transmitted to the subject.

  Each ultrasonic transducer includes, for example, a piezoelectric ceramic represented by PZT (lead zirconate titanate), a polymer piezoelectric element represented by PVDF (polyvinylidene fluoride), PMN-PT (magnesium niobate / lead titanate). It is constituted by an element in which electrodes are formed at both ends of a piezoelectric body made of a piezoelectric single crystal or the like typified by a solid solution, that is, a vibrator.

  When a pulsed or continuous wave voltage is applied to the electrodes of such a vibrator, the piezoelectric material expands and contracts, and pulse or continuous wave ultrasonic waves are generated from the respective vibrators, and the synthesis of these ultrasonic waves. As a result, an ultrasonic beam is formed. In addition, each vibrator expands and contracts by receiving propagating ultrasonic waves to generate electric signals, and these electric signals are output as ultrasonic reception signals (analog element signals).

  The transmission unit 14 includes, for example, a plurality of pulsars, and according to a transmission delay pattern selected according to a control signal from the control unit 30, a set of a predetermined number of ultrasonic transducers (hereinafter, referred to as a transducer array 36). The delay amount of each drive signal is adjusted so that the ultrasonic beam component transmitted from the ultrasonic element forms one ultrasonic beam and is supplied to a plurality of ultrasonic elements forming a set.

  In response to a control signal from the control unit 30, the receiving unit 16 causes the transducer array 36 to transmit the ultrasonic echo generated by the interaction between the ultrasonic beam transmitted from the transducer array 36 and the subject. Received and output received signals, ie, analog element signals for each ultrasonic element are amplified and output.

Here, the reception unit 16 includes a plurality of analog element signals received by a plurality of ultrasonic elements, corresponding to one transmission of the ultrasonic beam, and includes information on the received ultrasonic elements and information on reception times. Output as one analog element data. That is, the element data is data representing the intensity of the received signal with respect to the position of the element and the reception time.
The receiving unit 16 receives an ultrasonic echo and outputs analog element data every time the transmitting unit 14 transmits one ultrasonic beam. Therefore, the transmitter 14 outputs a plurality of analog element data corresponding to each transmission by transmitting the ultrasonic beam a plurality of times.
The receiver 16 supplies analog element data to the A / D converter 18.

  The A / D conversion unit 18 is connected to the reception unit 16 and converts the analog element data supplied from the reception unit 16 into digital element data (first element data). The A / D conversion unit 18 supplies the A / D converted digital element data to the element data storage unit 20 and the image generation unit 24.

  The element data storage unit 20 sequentially stores digital element data output from the A / D conversion unit 18. In addition, the element data storage unit 20 stores information on the frame rate input from the control unit 30 (for example, parameters indicating the depth of the reflection position of the ultrasonic wave, the density of the scanning line, and the visual field width) in the digital element data ( Hereinafter, the data is stored in association with element data).

The image generation unit 24 generates a sound ray signal (reception data) from the element data supplied from the A / D conversion unit 18 or the element data storage unit 20 under the control of the control unit 30, and superimposes the sound ray signal from the sound ray signal. A sound image is generated.
The image generation unit 24 includes a phasing addition unit 38, a detection processing unit 40, a DSC 42, an image creation unit 44, and an image memory 46.

The phasing addition unit 38 receives one reception delay pattern from a plurality of reception delay patterns stored in advance based on the distribution of sound speeds stored in the sound speed storage unit 54 according to the reception direction set in the control unit 30. A reception focus process is performed by selecting a delay pattern and adding and adding a delay to each element signal of element data based on the selected reception delay pattern. By this reception focus processing, reception data (sound ray signal) in which the focus of the ultrasonic echo is narrowed is generated.
The phasing addition unit 38 supplies the received data to the detection processing unit 40.

The detection processing unit 40 corrects attenuation by distance according to the depth of the reflection position of the ultrasonic wave on the reception data generated by the phasing addition unit 38, and then performs envelope detection processing to perform detection. B-mode image data that is tomographic image information related to the tissue in the specimen is generated.
A DSC (digital scan converter) 48 converts (raster conversion) the B-mode image data generated by the detection processing unit 40 into image data according to a normal television signal scanning method.

The image creation unit 44 performs various necessary image processing such as gradation processing on the B-mode image data input from the DSC 42 to create B-mode image data for use in inspection and display, and then creates the created inspection. Or display B-mode image data is output to the display control unit 26 for display or stored in the image memory 46.
The image memory 46 temporarily stores the inspection B-mode image data created by the image creation unit 44. The inspection B-mode image data stored in the image memory 46 is read to the display control unit 26 for display on the display unit 28 as necessary.

The display control unit 26 causes the display unit 28 to display an ultrasonic image based on the inspection B-mode image signal subjected to the image processing by the image creation unit 44.
The display unit 28 includes a display device such as an LCD, for example, and displays an ultrasonic image under the control of the display control unit 26.

The region setting unit 50 sets a plurality of regions in the imaging region where scanning with ultrasonic waves is performed according to an input from the operation unit 32 by the operator or according to an instruction from the control unit 30. In this apparatus, an appropriate sound speed is determined for each region.
FIG. 3 schematically shows the set area. In FIG. 3, the y direction corresponds to the ultrasonic wave transmission direction, and the x direction corresponds to the arrangement direction of the ultrasonic elements.
As indicated by a broken line in FIG. 3, the imaging region is divided into a plurality of rectangular portions to set the region.
In the illustrated example, the area is rectangular. However, the area is not limited to this, and the area may be a line area corresponding to a line for transmitting an ultrasonic beam, or may correspond to one pixel. There may be. Further, for example, in the case of a convex probe, each region may have a fan shape corresponding to the shape of the imaging region. In the illustrated example, the size of each region is the same. However, the size is not limited to this, and the size may be different for each region.
The size of the area to be set is not particularly limited. However, as the area is set smaller, the accuracy of the entire ultrasonic image is improved, but the processing time for determining the sound speed may be longer.
The region setting unit 50 supplies information on the set region to the sound speed determination unit 52 (element data acquisition unit 56).

The sound speed determination unit 52 is a part that sequentially determines an appropriate sound speed for each region set by the region setting unit 50.
The sound speed determination unit 52 includes an element data acquisition unit 56, a sound speed acquisition unit 58, an image quality determination unit 60, and a sound speed calculation unit 62.
In the present invention, the sound velocity of the region is defined as the region from the ultrasonic probe 12 to the region when it is assumed that the space between the region and the ultrasonic probe 12 (the transducer array 36) is filled with a uniform material. It represents the speed of sound. That is, the average sound speed between the region and the ultrasonic probe 12 is also referred to as ambient sound speed.

The element data acquisition unit 56 is a part that reads out element data corresponding to a region for obtaining a sound speed (hereinafter also referred to as a region of interest) from the element data storage unit 20 based on information on the region set by the region setting unit 50. .
The element data acquisition unit 56 supplies the read element data to the image quality determination unit 60.

The sound speed acquisition unit 58 has already determined a region within a predetermined range, that is, a spatially neighboring region, from the region for calculating the sound speed (region of interest) based on the region information set by the region setting unit 50. This is a part for reading the completed sound speed from the sound speed storage unit 54 and acquiring the preliminary sound speed as a temporary sound speed value of the region of interest.
Specifically, in the example shown in FIG. 3, the attention area for obtaining the sound speed is E _{(x, y)} , and the hatched areas (the areas x−2 and x−1, and E _{(x, y−1)} ) Is a region in which the speed of sound has been previously determined in the same frame, the sound speed acquisition unit 58 receives the attention region E _{(x, y) from} the sound speed storage unit 54 as the preliminary sound speed of the region of interest E _{(x, y) .} The sound speed value of the area E _{(x, y-1)} adjacent to _y) is acquired.

Note that the sound velocity acquisition unit 58 is limited to a configuration that acquires the sound velocity values of the region E _{(x, y-1)} adjacent to the region of interest E _{(x, y)} and the y direction (transmission direction of ultrasonic waves ₎ as the preliminary sound velocity. The sound speed value of the region of interest E _{(x, y)} and the region E _{(x-1, y)} adjacent in the x direction may be acquired as the preliminary sound velocity. Further, the area for acquiring the preliminary sound speed is not limited to the area adjacent to the attention area, and may be an area (a neighboring area) within a predetermined range from the attention area.
The predetermined range may be determined according to the diagnosis target (type of organ to be examined) and the like. For example, a region within 10 cm from the region of interest may be set as the predetermined range. The predetermined area may be changed by the operator.
Further, the configuration is not limited to the configuration in which the sound velocity value of one region is acquired as the preliminary sound velocity, and the sound velocity values in two or more regions may be read and the average value or the weighted average value may be acquired as the preliminary sound velocity. For example, in FIG. 3, the average value of the sound speed value in the area E _{(x, y-1) and} the sound speed value in the area E _{(x-1, y)} may be used as the preliminary sound speed in the attention area E _{(x, y).} .

In addition, the sound speed acquisition unit 58 is not limited to the structure of acquiring the sound speed value of the area in the same frame as the preliminary sound speed, and the structure of acquiring the sound speed value of the area at the same position before the predetermined frame as the preliminary sound speed, that is, It is good also as a structure which acquires the sound speed value of the area | region near in time as a preliminary sound speed.
FIG. 4 is a schematic diagram for explaining a region of interest and a temporally neighboring region.
In FIG. 4, when the frame including the attention area E _{(x, y), t} for which the sound speed value is calculated is the attention frame F _t , the sound speed acquisition unit 58 performs the attention of the frame F _t−1 immediately before the attention frame F _t. region _{E (x, y-1)} , the region of the same position as _t E _{(x, y),} reads out the sound velocity of the _t-1, the region of interest E _{(x, y),} may be pre-speed of sound _t.

Note that when the sound speed value in a temporally neighboring area is read out, the sound speed value in the area at the same position several frames before (frames F _t-2 and F _t-3 ) is not limited to the immediately preceding frame. The preliminary sound speed of the attention area E _{(x, y) and t} may be read out. Alternatively, the sound speed value of each area of a plurality of frames may be read, and the average value may be used as the preliminary sound speed of the attention area E _{(x, y) and t} .
Further, the sound speed acquisition unit 58 may read out the sound speed value in the temporally neighboring area and the sound speed value in the spatially neighboring area, and use these average values as the preliminary sound speed of the attention area. For example, the sound velocity values of the areas E _{(x, y-1) and t of} the same frame, the areas E _{(x-1, y) and t,} and the areas E _{(x, y) and t-1} of the previous frame, respectively. The average value of these values may be read out and used as the preliminary sound speed of the attention area E _{(x, y) and t} .
The sound speed acquisition unit 58 supplies the acquired preliminary sound speed to the image quality determination unit 60.

Based on the preliminary sound speed acquired by the sound speed acquisition unit 58, the image quality determination unit 60 generates an image of the region of interest (attention image) from the element data of the region of interest acquired by the element data acquisition unit 56. This is a part for determining image quality.
First, the image quality determination unit 60 generates an image of the attention area from the supplied element data. The image generation method is basically the same as that of the image generation unit 24. That is, according to the reception delay pattern based on the preliminary sound speed acquired by the sound speed acquisition unit 58, the element data is added with a delay to perform reception focus processing and generate reception data (sound ray signal). B-mode image data is generated by correcting the attenuation in accordance with the depth of the generated sound ray signal and performing envelope detection processing.

Next, the image quality is determined by evaluating the sharpness value of the generated B-mode image data of the attention area. If the sharpness value is greater than or equal to a predetermined threshold, it is determined that the image quality is good, and if it is less than the threshold, it is determined that the image quality is low.
As a method for calculating the sharpness value of the image, a known calculation method may be used. For example, a calculation method for calculating the half-value width of the maximum luminance point in the region of interest as the sharpness value can be used.

Note that the image quality determination method performed by the image quality determination unit 60 is not limited to the determination based on the sharpness value, and the contrast, luminance value, image spatial frequency, integral value, square integral value, peak value, half-value width, frequency spectrum, and the like. The image quality may be determined by an evaluation index such as a frequency spectrum integrated value, a square integrated value, or an autocorrelation value standardized by integration, maximum value, or DC component.
Further, the image quality determination method performed by the image quality determination unit 60 is not limited to the configuration in which the sharpness value (evaluation index) of the image is compared with a predetermined threshold value, and is compared with the sharpness value of the image in the same region of the previous frame. If the difference is within a predetermined range, it may be determined to be good.

  In addition, the image quality determination unit 60 performs reception focus processing by adding a delay to the element data according to a reception delay pattern based on the preliminary sound speed acquired by the sound speed acquisition unit 58 instead of the image of the region of interest. Image quality determination can also be performed based on the data. Specifically, the reference signal in which the received data after phasing addition at the preliminary sound speed is arranged for the same receiving elements as before the phasing addition, and the received data (delayed) before performing the phasing addition by correcting the delay time at the preliminary sound speed. Similarity with time-corrected element data) is evaluated, and if the similarity is equal to or greater than a predetermined threshold, it is determined that the image quality is good, and if it is equal to or less than the threshold, it is determined that the image quality is low.

  When it is determined that the image quality is good as a result of the image quality determination of the attention area, the image quality determination section 60 adopts the preliminary sound speed used for the image quality determination as the sound speed of the attention area and supplies it to the sound speed storage section 54. If it is determined that the image quality is poor, the determination result is supplied to the sound speed calculation unit 62.

The sound speed calculation unit 62 is a part that calculates the sound speed in detail for a region of interest that is determined to have poor image quality as a result of image quality determination by the image quality determination unit 60.
When the determination result that the image quality is bad is supplied from the image quality determination unit 60, the sound speed calculation unit 62 acquires the element data corresponding to the region of interest acquired by the element data acquisition unit 56, and the element data The sound speed value (hereinafter referred to as the set sound speed) is changed in various ways, and based on the set sound speed, a reception focus process is performed to form an ultrasonic image, and the set sound speed at which the contrast and / or sharpness of the image is the highest is obtained. And calculated as the optimum sound speed value of the attention area.
As a method for determining the optimum sound speed value, for example, as described in JP-A-8-317926, the optimum sound speed value can be determined based on the contrast of the image, the spatial frequency in the scanning direction, the variance, and the like. .

The sound speed calculation unit 62 will be described in more detail using the flowchart shown in FIG.
When the sound speed calculation unit 62 acquires the element data of the attention area, the sound speed calculation unit 62 changes the set sound speed V in increments of ΔV from Vst to Vend, and at each set sound speed V, based on the set sound speed V, the element data acquisition unit. Using the element data of the region of interest supplied from the reception focus processing, a sound ray signal is generated, an ultrasonic image is formed from this sound ray signal, and the sharpness of the image of the region of interest at each set sound velocity V Is calculated.
The sharpness value of the image at each set sound speed V is compared, and the obtained set sound speed V having the highest sharpness value is adopted as the optimum sound speed value.
As a search range for the set sound speed V, Vst may be 1400 m / s, Vend may be 1700 m / s, and ΔV may be about 10 to 50 m / s.
The sound speed calculation unit 62 supplies the calculated sound speed value to the sound speed storage unit 54.

Note that the sound speed calculation unit is not limited to the configuration in which the set sound speed with the highest sharpness value is the optimum sound speed value, and the image quality is determined based on the evaluation index such as the contrast, the brightness value, or the spatial frequency of the image. The optimal sound speed value may be set to the best sound speed.
In the above embodiment, the sound speed calculation unit is configured to search for the set sound speed within a predetermined search range. However, the present invention is not limited to this, and the search range is based on the preliminary sound speed acquired by the sound speed acquisition unit 58. It is good also as a structure which determines. For example, the optimum sound speed may be obtained by setting the range of ± 50 m / s of the preliminary sound speed as a search range. Further, after determining the search range based on the preliminary sound speed and performing a search, the image quality determination may be performed, and if the determination result is negative, the search range may be expanded to obtain the optimum sound speed.

  Further, the sound speed calculation method of the sound speed calculation unit 62 is not limited to a configuration in which the sound speed value that provides the best image quality is obtained by sequentially changing the set sound speed within a predetermined search range, and is optimal for various regions. A method for calculating the sound velocity value can be used. For example, the reference signal in which the received data after phasing addition at each set sound speed is arranged for the same receiving elements as before phasing addition, and the received data (delay time before performing phasing addition by correcting the delay time at each set sound speed) A method (e.g., the method described in Japanese Patent Application No. 2012-120242) can be used in which similarity is evaluated at each set sound speed and the sound speed when the similarity is high is set to an optimum sound speed value. It is.

  As described above, in order to obtain a higher quality image in an ultrasonic inspection apparatus, an index (focus index) for comprehensively determining image quality based on a plurality of set sound speeds for each region (pixel, line). Etc.) and the set sound speed at which the image quality determination result is the best is obtained as the optimum sound speed value. Therefore, there is a problem that it takes time to obtain the optimum sound speed in all regions. As a result, there is a problem that the frame rate is lowered.

On the other hand, the present invention acquires the preliminary sound speed based on the sound speed value of the area within the predetermined range from the attention area, determines the image quality when the image of the attention area is generated based on the preliminary sound speed, If the image quality judgment result is good, this preliminary sound speed is adopted as the sound speed of the region of interest. Therefore, an appropriate sound speed value for each region can be obtained in a short time.
Further, since the optimum sound speed value depends on the distance (depth) from the ultrasonic probe and the property of the tissue through which the ultrasonic wave passes, the optimum sound speed value is likely to be a close value in areas close to each other. Therefore, even if the sound velocity value in the spatially neighboring region is adopted as the sound velocity in the region of interest, a high-quality image can be obtained.
When the operator wants to acquire an ultrasound image, the operator stops the ultrasound probe and acquires the ultrasound image. In such a case, since the same tissue is detected in the same region between frames, the optimum sound speed value is also the same value. Therefore, even when the sound speed value in the temporally neighboring area is adopted as the sound speed value in the attention area, a high-quality image can be obtained.
In addition, when the position of the tissue boundary or the operator moves the ultrasonic probe, the result of the image quality determination based on the preliminary sound speed becomes negative, and the result of the image quality determination based on the preliminary sound speed acquired from the nearby region If not, an optimum sound speed is obtained, so that a high-quality image can be obtained.
As described above, the ultrasonic inspection apparatus of the present invention can obtain an appropriate sound speed value for each region in a short time, and can construct a highly accurate ultrasonic image without reducing the frame rate.

The sound speed storage unit 54 stores the sound speed value supplied from the image quality determination unit 60 and the sound speed calculation unit 62 as a so-called sound speed map in association with the position information of the area.
The sound speed storage unit 54 may be configured to sequentially update the sound speed value of the corresponding region each time the sound speed value is supplied from the image quality determination unit 60 or the sound speed calculation unit 62, or generates a sound speed map for each frame. You may do it.
When the sound speed acquisition unit 58 reads out the sound speed value in a temporally nearby region, the sound speed storage unit 54 generates a sound speed map for each frame and not only the latest sound speed (sound speed map), A sound speed map up to several frames before is stored.
The sound speed storage unit 54 supplies information on the sound speed map to the phasing addition unit 38 and the sound speed acquisition unit 58.

The control unit 30 controls each unit of the ultrasonic inspection apparatus 10 based on a command input from the operation unit 32 by the operator.
Here, the control unit 30 determines various information by the operator via the operation unit 32, particularly information necessary for setting a region by the region setting unit 50, and sound speed by the sound speed determination unit 52. When the necessary information is input, the above-described various information input from the operation unit 32 is transmitted as necessary to the transmission unit 14, the reception unit 16, the element data storage unit 20, and the image generation unit 24. The display control unit 26, the region setting unit 50, the sound speed determination unit 52, and the like are supplied.

The operation unit 32 is for an operator to perform an input operation, and can be formed from a keyboard, a mouse, a trackball, a touch panel, and the like.
In addition, the operation unit 32 includes an input device for an operator to input various information as required, particularly information used for setting the above-described region, information used for sound speed determination, and the like. .

The storage unit 34 includes various information input from the operation unit 32, the transmission unit 14, the reception unit 16, the element data storage unit 20, the image generation unit 24, the display control unit 26, the region setting unit 50, and the sound speed determination unit. 52 stores information necessary for processing and operation of each unit controlled by the control unit 30 and the like, and an operation program and processing program for executing the processing and operation of each unit. , MT, RAM, CD-ROM, DVD-ROM and other recording media can be used.
In addition, the phasing addition part 38, the detection process part 40, DSC42, the image creation part 44, the sound speed acquisition part 58, the image quality determination part 60, the sound speed calculation part 62, and the display control part 26 perform various processes to CPU and CPU. The program is composed of operation programs to be executed, but may be composed of a digital circuit.

  The operation and action of the ultrasonic inspection apparatus of the present invention will be described.

First, the operation of the ultrasonic inspection apparatus when generating an ultrasonic image will be described.
When the operator abuts the ultrasonic probe 12 on the surface of the subject and starts measurement, an ultrasonic beam is transmitted from the transducer array 36 according to the drive signal supplied from the transmission unit 14, and the ultrasonic wave from the subject is transmitted. The transducer array 36 receives the echo and outputs an analog element signal as a reception signal.
The receiving unit 16 outputs an analog element signal output from each element as one analog element data, and supplies it to the A / D converter 18. The A / D conversion unit 18 converts analog element data into digital element data, supplies the element data to the element data storage unit 20, and stores and holds the data.

  The phasing addition unit 38 of the image generation unit 24 reads the element data from the element data storage unit 20, performs reception focus processing on the element data, generates reception data (sound ray signal), and supplies the reception data (sound ray signal) to the detection processing unit 40. To do. At this time, the phasing addition unit 38 performs reception focus processing based on the sound speed map stored in the sound speed storage unit 54. The detection processing unit 40 processes the sound ray signal and generates a B-mode image signal. The DSC 42 performs raster conversion on the B-mode image signal, and the image creation unit 44 performs image processing to generate an ultrasonic image. The generated ultrasonic image is stored in the image memory 46, and the ultrasonic image is displayed on the display unit 28 by the display control unit 26.

Next, the operation of the ultrasonic inspection apparatus when obtaining the sound velocity map will be described.
FIG. 6 is a flowchart for explaining the operation of the ultrasonic inspection apparatus shown in FIG.
When the operator abuts the ultrasonic probe 12 on the surface of the subject and starts measurement, an ultrasonic beam is transmitted from the transducer array 36 according to the drive signal supplied from the transmission unit 14, and the ultrasonic wave from the subject is transmitted. The transducer array 36 receives the echo and outputs an analog element signal as a reception signal.
The receiving unit 16 outputs an analog element signal output from each element as one analog element data, and supplies it to the A / D converter 18. The A / D conversion unit 18 converts analog element data into digital element data, supplies the element data to the element data storage unit 20, and stores and holds the data.

On the other hand, the area setting unit 50 sets a plurality of areas in an imaging area where scanning with ultrasound is performed in response to an input from the operation unit 32 or an instruction from the control unit 30.
Sound speed determination unit 52, for each area set by the area setting unit 50 sequentially (from E ₁₁ to E _{end The),} by changing the region of interest to determine the speed of sound in each region.
The element data acquisition unit 56 of the sound speed determination unit 52 reads element data corresponding to the region of interest from the element data storage unit 20 and supplies the element data to the image quality determination unit 60. The sound speed acquisition unit 58 reads the already determined sound speed in the vicinity of the attention area from the sound speed storage unit 54, acquires it as a preliminary sound speed, and supplies the preliminary sound speed to the image quality determination unit 60.
The image quality determination unit 60 first performs reception focus processing of the element data of the attention area acquired by the element data acquisition unit 56 according to the reception delay pattern based on the preliminary sound speed acquired by the sound speed acquisition unit 58, generates reception data, B-mode image data is generated by correcting the attenuation according to the depth and performing envelope detection processing. Next, the sharpness value of the generated B-mode image data of the attention area is evaluated to determine the image quality. If the image quality is determined to be good, the preliminary sound speed used for the image quality determination is adopted as the sound speed of the attention area. , And supplied to the sound speed storage unit 54. If the image quality determination result is negative, the determination result is supplied to the sound speed calculation unit 62.
When the image quality determination result is negative, the sound speed calculation unit 62 comprehensively changes the set sound speed, calculates the sound speed with the best image quality as the sound speed of the attention area, and supplies the sound speed to the sound speed storage unit 54.
The sound speed storage unit 54 stores the sound speed values supplied from the image quality determination unit 60 and the sound speed calculation unit 62 as a sound speed map in association with the position information of the area.

As described above, the ultrasonic inspection apparatus of the present invention acquires the preliminary sound speed based on the sound velocity value of the area within the predetermined range from the attention area, and the image quality when the image of the attention area is generated based on the preliminary sound speed. If the image quality determination result is good and the preliminary sound speed is adopted as the sound speed of the attention area, the index for image quality determination is comprehensively determined at a plurality of set sound speeds, and the determination result is the best. Therefore, an appropriate sound speed value for each area can be obtained in a short time.
Further, since the optimum sound speed value depends on the distance (depth) from the ultrasonic probe and the property of the tissue through which the ultrasonic wave passes, the optimum sound speed value is likely to be a close value in areas close to each other. Therefore, even if the sound velocity value in the spatially neighboring region is adopted as the sound velocity in the region of interest, a high-quality image can be obtained.
When the operator wants to acquire an ultrasound image, the operator stops the ultrasound probe and acquires the ultrasound image. In such a case, since the same tissue is detected in the same region between frames, the optimum sound speed value is also the same value. Therefore, even when the sound speed value in the temporally neighboring area is adopted as the sound speed value in the attention area, a high-quality image can be obtained.
In addition, when the position of the tissue boundary or the operator moves the ultrasonic probe, the result of the image quality determination based on the preliminary sound speed becomes negative, and the result of the image quality determination based on the preliminary sound speed acquired from the nearby region If not, an optimum sound speed is obtained, so that a high-quality image can be obtained.
As described above, the ultrasonic inspection apparatus of the present invention can obtain an appropriate sound speed value for each region in a short time, and can construct a highly accurate ultrasonic image without reducing the frame rate.

In the above embodiment, the image quality determination unit 60 is configured to generate an image of the region of interest and obtain an evaluation index (sharpness value, etc.) based on the image to evaluate the image quality. There is no limitation, and the image quality may be determined from the element data of the attention area without generating the image of the attention area. That is, a configuration may be adopted in which reception focus processing is performed on element data for each of a plurality of set sound speeds, a focus index is obtained, and an optimum sound speed is determined based on the focus index.
As a focus index calculation method and determination method, for example, a method described in Japanese Patent Application Laid-Open No. 2011-92686 can be used.

In the above embodiment, the image quality determination unit 60 has a function of generating an image for determining the image quality. However, the present invention is not limited to this, and the image generation unit 24 performs image quality determination. It is good also as a structure which produces | generates the image for determination and determines in the image quality determination part 60. FIG.
In addition, the configuration is not limited to the configuration in which the image quality determination is performed by acquiring the preliminary sound speed in all areas within one frame, and the initial value set in advance for the area in which the sound speed is first determined within one frame. May be used as the preliminary sound speed, or the optimal sound speed may be calculated by the sound speed calculation unit 62 without acquiring the preliminary sound speed (without performing image quality determination). In some predetermined regions, the sound speed calculation unit 62 may calculate the optimum sound speed without acquiring the preliminary sound speed and determining the image quality. For example, in the region including the focal point of the ultrasonic beam, the optimum sound speed can be obtained more accurately by calculating the optimum sound speed, and the calculated sound speed can be used as a preliminary sound speed. The image quality of the area around the area can be improved.

Further, the generation of the ultrasonic image and the determination of the sound speed may be performed simultaneously or separately. In other words, the sound speed may be determined from the element data obtained by transmitting and receiving a set of ultrasonic waves for one frame, and an ultrasonic image may be generated. From the element data obtained by separate transmission and reception, The generation of the sound image and the determination of the sound speed may be performed, respectively. In the case where the ultrasonic image is generated from the element data used for the determination of the sound speed, in the region where the determination result by the image quality determination unit is good, the image used for the determination of the image quality is used as the ultrasonic image. Also good.
Further, the sound speed may be determined every frame or once every several frames.

  In the above embodiment, the reception focus process is performed based on the sound speed map stored in the sound speed storage unit 54 when the reception focus process is performed on the element data. However, the present invention is not limited to this. When transmitting the ultrasonic beam by the transmission unit 14, the delay amount of the drive signal may be adjusted based on the sound speed map stored in the sound speed storage unit 54.

  In the above embodiment, the preliminary sound speed is acquired and the image quality is determined. If the determination result is negative, the sound speed calculation unit 62 calculates the optimum sound speed of the attention area. There is no limitation, and if the determination result is negative, the determination result may be displayed on the display unit 28 to warn the operator. In this case, the operator may determine whether or not to calculate the sound speed.

As described above, the region for which the sound velocity acquisition unit 58 acquires the preliminary sound velocity may be a region that is temporally or spatially close to the region of interest, but the sound velocity value of any region is acquired. This may be determined in advance or may be determined automatically. For example, when the movement of the ultrasonic probe 12 is sensed by a difference from an acceleration sensor or an image of the previous frame and is stopped, it is preferable to acquire a sound velocity value in a temporally neighboring region. In addition, when the feature amount of the image moves between frames, it is preferable to obtain the sound speed value of a spatially neighboring region, and depending on the direction of motion, It is only necessary to automatically determine which sound speed of the area is acquired.
Alternatively, the imaging area may be divided into a plurality of partial images according to the image feature amount and the sound speed value of the area in the same partial image may be acquired as the preliminary sound speed.

  Further, the ultrasonic inspection apparatus of the present embodiment is controlled by a signal processing program stored in a memory attached to a control unit (not shown). That is, the signal processing program is read from the memory by the control unit, the area is set according to the signal processing program, and the function of determining the sound speed sequentially for the set area and creating the sound speed map is executed. The

  Note that the signal processing program of the ultrasonic inspection apparatus is not limited to the one stored in the memory attached to the control unit in this way, and the signal processing program is stored in the ultrasonic inspection apparatus such as a CD-ROM. The information may be recorded on a memory medium (removable medium) configured to be detachable and read into the apparatus via an interface corresponding to the removable medium.

  As described above, the ultrasonic inspection apparatus of the present invention, the signal processing method of the ultrasonic inspection apparatus, and the program have been described in detail, but the present invention is not limited to the above examples, and in a range not departing from the gist of the present invention. Of course, various improvements and modifications may be made.

DESCRIPTION OF SYMBOLS 10 Ultrasonic inspection apparatus 12 Ultrasonic probe 14 Transmission part 16 Reception part 18 A / D conversion part 20 Element data storage part 24 Image generation part 26 Display control part 28 Display part 30 Control part 32 Operation part 34 Storage part 36 Vibrator array 38 Phase adjusting and adding unit 40 Detection processing unit 42 DSC
44 Image creation section 46 Image memory 50 Area setting section 52 Sound speed determination section 54 Sound speed storage section 56 Element data acquisition section 58 Sound speed acquisition section 60 Image quality determination section 62 Sound speed calculation section

Claims (13)

An ultrasonic inspection apparatus that inspects an inspection object using an ultrasonic beam,
An area setting unit for setting a plurality of areas in the inspection object;
A sound speed calculation unit for calculating the sound speed of the region;
A sound velocity acquisition unit that acquires one of the plurality of regions as a region of interest, and acquires a preliminary sound speed based on a sound velocity in at least one of the regions within a predetermined range from the region of interest;
An image quality determination unit that determines the image quality of the attention area based on the preliminary sound speed acquired by the sound speed acquisition unit;
When the determination result of the image quality determination unit is good, the preliminary sound speed acquired by the sound speed acquisition unit is adopted as the sound speed of the attention region. When the determination result is negative, the sound speed calculation unit performs the attention region. An ultrasonic inspection apparatus characterized by calculating the sound speed of the sound.   The ultrasonic inspection apparatus according to claim 1, wherein the sound speed acquisition unit acquires a preliminary sound speed based on a sound speed in at least one of the regions within a predetermined range in time and / or space from the region of interest.   The ultrasonic inspection apparatus according to claim 2, wherein the spatially predetermined region is a region close to the attention region on the same image.   The ultrasonic inspection apparatus according to claim 2 or 3, wherein the spatially predetermined region is a region in the same partial image when the image is divided into a plurality of partial images.   The ultrasonic inspection apparatus according to claim 2, wherein the region within a predetermined range in time is a region corresponding to the region of interest in an image before a predetermined frame.   The region within a predetermined range in terms of time is a region corresponding to the region of interest in at least one image obtained by performing a predetermined process on a plurality of images before a predetermined frame, or the plurality of predetermined regions The area corresponding to the attention area in at least one of the images before the frame, and the sound speed in the area is a sound speed obtained by performing a predetermined process on the sound speed before the plurality of predetermined frames. Item 6. The ultrasonic inspection apparatus according to any one of Items 2 to 5.   The ultrasonic inspection apparatus according to claim 6, wherein the predetermined process is a process of obtaining either an average value or a median value of sound speeds before the plurality of predetermined frames.   The ultrasonic inspection according to claim 1, wherein the image quality determination unit performs image quality determination based on any one of sharpness, brightness, contrast, and frequency of the image of the region of interest generated based on preliminary sound speed. apparatus.   The ultrasonic inspection according to claim 1, wherein the image quality determination unit performs image quality determination by comparing an image of the region of interest generated based on a preliminary sound speed and an image of the same region of the previous image. apparatus.   The image quality determination unit evaluates the similarity between the reference data generated based on the reception data after the phasing addition of the region of interest generated based on the preliminary sound velocity and the reception data before the phasing addition, and determines the image quality The ultrasonic inspection apparatus according to any one of claims 1 to 9.   The ultrasonic inspection apparatus according to claim 1, further comprising an element data storage unit that stores element data that each element of the transducer array receives and outputs an ultrasonic echo. A signal processing method of an ultrasonic inspection apparatus that inspects an inspection object using an ultrasonic beam,
An area setting step for setting a plurality of areas in the inspection object;
A sound speed calculating step for calculating the sound speed of the area;
A sound speed acquisition step of acquiring one of the plurality of areas as a target area and acquiring a preliminary sound speed based on a sound speed in at least one of the areas within a predetermined range from the target area;
An image quality determination step for determining an image quality of the attention area based on the preliminary sound speed acquired in the sound speed acquisition step,
When the determination result of the image quality determination step is good, the preliminary sound speed acquired by the sound speed acquisition step is adopted as the sound speed of the attention area. When the determination result is negative, the attention area is calculated by the sound speed calculation step. A signal processing method for an ultrasonic inspection apparatus, characterized by calculating a sound speed of the ultrasonic inspection apparatus. A program that causes a computer to execute signal processing of an ultrasonic inspection apparatus that inspects an inspection object using an ultrasonic beam,
An area setting step for setting a plurality of areas in the inspection object;
A sound speed calculating step for calculating the sound speed of the area;
A sound speed acquisition step of acquiring one of the plurality of areas as a target area and acquiring a preliminary sound speed based on a sound speed in at least one of the areas within a predetermined range from the target area;
An image quality determination step for determining an image quality of the attention area based on the preliminary sound speed acquired in the sound speed acquisition step,
When the determination result of the image quality determination step is good, the preliminary sound speed acquired by the sound speed acquisition step is adopted as the sound speed of the attention area. When the determination result is negative, the attention area is calculated by the sound speed calculation step. A signal processing program for an ultrasonic inspection apparatus characterized by calculating a sound speed of the ultrasonic inspection apparatus.

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