JP2013244160A - Ultrasonic diagnostic equipment and method for estimating sound velocity - Google Patents

Abstract

A sound velocity (local sound velocity) in a desired region in a subject is accurately obtained.
The ultrasonic diagnostic apparatus transmits an ultrasonic wave to a subject according to a plurality of drive signals, and outputs a plurality of reception signals by receiving an ultrasonic echo propagating from the subject. An ultrasonic probe including a transducer, a member interposed between the ultrasonic probe and the subject, an acoustic coupler that propagates ultrasonic waves at a predetermined sound velocity, and a sound velocity value calculating means for obtaining an average sound velocity of the subject; The sound velocity value calculation means performs the calculation based on the sound velocity of the acoustic coupler when obtaining the average sound velocity on the surface layer of the subject.
[Selection] Figure 1

Description

  The present invention relates to an ultrasonic diagnostic apparatus and a sound velocity estimation method, and more particularly to a technique for accurately obtaining a sound velocity (local sound velocity) in a desired region within a subject.

  In the medical field, various imaging techniques have been developed in order to observe and diagnose the inside of a subject. In particular, ultrasonic imaging that acquires internal information of a subject by transmitting and receiving ultrasonic waves enables real-time image observation, and other medical uses such as X-ray photographs and RI (radio isotope) scintillation cameras. Unlike imaging technology, there is no radiation exposure. Therefore, ultrasonic imaging is used as a highly safe imaging technique in a wide range of areas including gynecological system, circulatory system, digestive system, etc. in addition to fetal diagnosis in the obstetrics field.

  The principle of ultrasonic imaging is as follows. Ultrasound is reflected at the boundary between regions having different acoustic impedances, such as the boundary between structures in the subject. Therefore, by transmitting an ultrasonic beam into a subject such as a human body, receiving an ultrasonic echo generated in the subject, and determining the reflection position and reflection intensity where the ultrasonic echo is generated, It is possible to extract the contour of the structure (eg, internal organs or lesion tissue).

  In general, in an ultrasonic diagnostic apparatus, an ultrasonic probe including a plurality of ultrasonic transducers (vibrators) having an ultrasonic transmission / reception function is used. By scanning a subject using an ultrasonic beam formed by combining a plurality of ultrasonic waves by transmission focus processing, receiving an ultrasonic echo reflected inside the subject, and performing reception focus processing, Based on the intensity of the ultrasonic echo, image information relating to a structure existing in the subject is obtained, and an ultrasonic image is displayed on the display unit.

  By the way, as one of the morphological images of the ultrasonic image, a B-mode image representing the shape (an image in which the amplitude of the ultrasonic echo is represented by the luminance of a point) is used. However, there is a desire to use information other than the shape for diagnosis, and one of them is the speed of sound. Since the speed of sound is effective acoustic information for diagnosing living tissues, lesions and their progress, etc., when doctors make an ultrasound diagnosis, it is proposed to measure the sound speed of a subject using various measurement methods. Has been. Attempts have also been made to measure the speed of sound in a desired region within the subject (hereinafter referred to as “local sound speed”).

For example, Patent Document 1 proposes a method for obtaining a sound speed (local sound speed) in a desired region in a subject based on a reception signal of an ultrasonic echo reflected in the subject. In this method, ROI1 and ROI2 are first set as two regions of interest at positions with different depths in the subject. Next, with ROI1 as the transmission focus position, the beam focusing degree in the reception focus process when the set sound velocity value is sequentially changed is determined. Then, based on the determination result, the average acoustic velocity C ₁ of the first in the path from the ultrasonic probe to ROI1 is required. Similarly, as the transmission focus position ROI2, average acoustic velocity _{C 2} of the second in a path from the ultrasonic probe to the ROI2 is required. Next, based on the first and second average sound speeds C ₁ and C ₂ and the distances from the ultrasonic probe to ROI 1 and ROI ₂ , the average sound speed (local sound speed) C _x in the path from ROI 1 to ROI 2 is obtained. It is done.

JP 2010-207490 A

However, in the method described in Patent Document 1, when the first average acoustic velocity C ₁ in the path leading to ROI1 from the ultrasonic probe has not been accurately determined, the average sound velocity C _x in the path leading to the ROI2 from ROI1 accurate Can not ask for. Moreover, determining the average acoustic velocity C ₁ distance (depth) at reducing the first ultrasonic probe and ROI1 more accurately can be considered, but an ultrasonic beam focusing accuracy and the distance is too small The reception signal of the ultrasonic echo is disturbed due to badness or the influence of the body wall (abdominal wall), and it is difficult to accurately obtain the local sound speed.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an ultrasonic diagnostic apparatus and a sound speed estimation method capable of accurately obtaining the sound speed (local sound speed) in a desired region within a subject. And

  To achieve the above object, the ultrasonic diagnostic apparatus according to the first aspect of the present invention transmits an ultrasonic wave to a subject according to a plurality of drive signals and receives an ultrasonic echo propagating from the subject. An ultrasonic probe including a plurality of ultrasonic transducers for outputting a plurality of received signals, a member interposed between the ultrasonic probe and the subject, and an acoustic coupler for propagating ultrasonic waves at a predetermined sound speed; Sound speed value calculating means for obtaining an average sound speed of the subject, and the sound speed value calculating means is an embodiment in which the mean sound speed on the surface layer of the subject is obtained based on the sound speed of the acoustic coupler.

  According to the above aspect, the average sound speed on the surface layer of the subject can be accurately obtained using the sound speed of the acoustic coupler. Thereby, the sound speed (local sound speed) in a desired region in the subject can be accurately obtained.

  In the ultrasonic diagnostic apparatus according to the second aspect of the present invention, in the first aspect, the acoustic coupler has a predetermined thickness in the ultrasonic transmission / reception direction of the ultrasonic probe.

  The ultrasonic diagnostic apparatus according to the third aspect of the present invention transmits an ultrasonic wave to a subject according to a plurality of drive signals and outputs a plurality of received signals by receiving an ultrasonic echo propagating from the subject. An ultrasonic probe including a plurality of ultrasonic transducers, and a member interposed between the ultrasonic probe and the subject, having a predetermined thickness in the ultrasonic transmission / reception direction of the ultrasonic probe, and supersonic at a predetermined sound speed By supplying an acoustic coupler that propagates sound waves and a plurality of drive signals to a plurality of ultrasonic transducers, and performing reception focus processing and detection processing on a plurality of reception signals output from the plurality of ultrasonic transducers, An ultrasonic image is represented on the basis of signal processing means for generating sound ray signals along the reception direction of ultrasonic waves, and sound ray signals generated by the signal processing means. Image signal generating means for generating an image signal; area setting means for setting a first area in the vicinity of the boundary between the subject and the acoustic coupler; and setting a second area in the subject; For the second region, focus determination means for determining the beam convergence in the reception focus processing when the set sound velocity value is sequentially changed, and the first average sound velocity in the path from the ultrasonic probe to the first region The sound speed setting means for setting the sound speed of the acoustic coupler and the determination result of the focus determination means determine at least a second average sound speed in the path from the ultrasonic probe to the second region, and the first and second average sound speeds. And a sound speed value calculating means for calculating an average sound speed in a path from the first area to the second area based on the distance from the ultrasonic probe to the first and second areas. It is an aspect.

  According to the above aspect, based on the first average sound velocity in the path from the ultrasonic probe to the first region and the second average sound speed in the route from the ultrasonic probe to the second region, When calculating the average sound velocity in the second region from the region, the first region is set near the boundary between the subject and the acoustic coupler with the acoustic coupler interposed between the ultrasound probe and the subject. By setting the sound speed of the acoustic coupler as the first average sound speed, the calculation accuracy of the average sound speed from the first area to the second area can be improved. Thereby, the sound speed (local sound speed) in a desired region in the subject can be accurately obtained.

  In the ultrasonic diagnostic apparatus according to the fourth aspect of the present invention, in the third aspect, the region setting means sets the first region at the boundary between the acoustic coupler and the subject.

  In the ultrasonic diagnostic apparatus according to the fifth aspect of the present invention, in the third aspect, the area setting means sets the first area in the acoustic coupler.

  The ultrasonic diagnostic apparatus according to a sixth aspect of the present invention is the ultrasonic diagnostic apparatus according to any of the third to fifth aspects, wherein the acoustic coupler has an identification member including its thickness and sound velocity, and the acoustic probe is attached to the ultrasonic probe. A coupler information reading means for reading the identification member of the acoustic coupler, and the sound speed setting means calculates the first average sound speed in the path from the ultrasonic probe to the first region based on the reading result by the coupler information reading means. This is a mode in which the sound speed of the acoustic coupler is set.

  The sound speed estimation method according to the seventh aspect of the present invention includes a plurality of ultrasonic waves transmitted to a subject according to a plurality of drive signals and a plurality of reception signals output by receiving ultrasonic echoes propagating from the subject. An ultrasonic probe including an ultrasonic transducer and a member interposed between the ultrasonic probe and the subject, and having a predetermined thickness in the ultrasonic transmission / reception direction of the ultrasonic probe and ultrasonic waves at a predetermined sound speed An acoustic velocity estimation method using an ultrasonic diagnostic apparatus comprising: an ultrasonic coupler that transmits a plurality of drive signals to a plurality of ultrasonic transducers in an ultrasonic probe, and an ultrasonic wave that propagates from a subject The reception direction of ultrasonic waves by performing reception focus processing and detection processing on multiple reception signals output from multiple ultrasonic transducers that have received echoes A sound ray signal generating step for generating a sound ray signal along the line, and an ultrasonic image generating step for generating an image signal representing an ultrasonic image based on the sound ray signal generated in the sound ray signal generating step, and An area setting step for setting a first area in the vicinity of the boundary between the subject and the acoustic coupler and setting a second area in the subject; and a set sound velocity value for the second area in the subject A focus determination step for determining a beam convergence degree in the reception focus processing when the values are sequentially changed, and a sound speed setting for setting the first average sound speed in the path from the ultrasonic probe to the first region as the sound speed of the acoustic coupler In accordance with the determination result in the step and the focus determination step, a second average sound velocity in at least a path from the ultrasonic probe to the second region is obtained, A sound speed value calculating step for calculating an average sound speed in a path from the first area to the second area based on the average sound speed of 2 and the distance from the ultrasonic probe to the first and second areas; It is an aspect containing.

  According to the above aspect, based on the first average sound velocity in the path from the ultrasonic probe to the first region and the second average sound speed in the route from the ultrasonic probe to the second region, When calculating the average sound velocity in the second region from the region, the first region is set near the boundary between the subject and the acoustic coupler with the acoustic coupler interposed between the ultrasound probe and the subject. By setting the sound speed of the acoustic coupler as the first average sound speed, the calculation accuracy of the average sound speed from the first area to the second area can be improved. Thereby, the sound speed (local sound speed) in a desired region in the subject can be accurately obtained.

  The sound speed estimation method according to an eighth aspect of the present invention is the aspect in the seventh aspect, in which the region setting step sets the first region at the boundary between the acoustic coupler and the subject.

  The sound speed estimation method according to the ninth aspect of the present invention is an aspect in which, in the seventh aspect, the region setting step sets the first region in the acoustic coupler.

  The sound speed estimation method according to a tenth aspect of the present invention is the sound speed estimation method according to any of the seventh to ninth aspects, wherein the acoustic coupler has an identification member including the thickness and speed of the acoustic coupler, and the acoustic probe is attached to the ultrasonic probe. A coupler information reading step for reading the identification member of the acoustic coupler, and the sound speed setting step includes a first average sound speed in a path from the ultrasonic probe to the first region based on a reading result by the coupler information reading step. Is set to the sound speed of the acoustic coupler.

  According to the present invention, the sound speed (local sound speed) in a desired region in the subject can be accurately obtained.

1 is a block diagram illustrating a configuration of an ultrasonic diagnostic apparatus according to an embodiment of the present invention. It is a flowchart figure which shows the sound speed estimation method used in the ultrasound diagnosing device shown in FIG. It is a figure which shows the relative positional relationship between an ultrasonic probe and a region of interest.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of an ultrasonic diagnostic apparatus according to an embodiment of the present invention. The ultrasonic diagnostic apparatus includes an ultrasonic probe 10, a scanning control unit 11, a transmission delay pattern storage unit 12, a transmission control unit 13, a drive signal generation unit 14, a reception signal processing unit 21, and a reception delay pattern. Storage unit 22, reception control unit 23, B-mode image signal generation unit 30, focus determination unit 41, sound speed value calculation unit 42, sound speed map creation unit 43, image display control unit 51, and display unit 52 A console 61, a control unit 62, a storage unit 63, an acoustic coupler 100, and a coupler information storage unit 102. Here, the transmission delay pattern storage unit 12 to the reception control unit 23 constitute signal processing means.

  The ultrasonic probe 10 includes a plurality of ultrasonic transducers 10a constituting a one-dimensional or two-dimensional transducer array. These ultrasonic transducers 10a transmit ultrasonic waves to the subject based on a plurality of applied drive signals, receive ultrasonic echoes propagating from the subject, and output a plurality of received signals.

  The acoustic coupler 100 includes an ultrasonic wave propagation medium that adjusts the distance (offset) between the ultrasonic probe 10 and the subject, and includes an ultrasonic wave transmitting / receiving surface (a plurality of ultrasonic transducers) of the ultrasonic probe 10. 10a is provided so as to be removable. When the acoustic coupler 100 is in close contact with the ultrasonic probe 10, the acoustic coupler 100 has a predetermined thickness in the transmission / reception direction of ultrasonic waves and propagates ultrasonic waves at a predetermined sound velocity.

  The acoustic coupler 100 may be made of any material that can regulate the speed of sound. For example, urethane rubber used for a phantom material can be preferably used. Moreover, the acoustic coupler 100 preferably has a thickness that allows sufficient convergence accuracy of the ultrasonic beam.

  The acoustic coupler 100 is provided with an identification member 104 (for example, a barcode) for identifying the speed of sound and thickness. The ultrasonic probe 10 is provided with coupler information reading means 106 for reading the identification member 104 of the acoustic coupler 100. The reading method of the coupler information reading unit 106 is not particularly limited, and various methods such as optical, magnetic, and electrical can be employed. Thus, when the acoustic coupler 100 is attached to the ultrasonic probe 10, the sound speed and thickness of the acoustic coupler 100 are read by the coupler information reading unit 106, and the sound speed and thickness of the acoustic coupler 100 are stored in the coupler information storage unit 102. The

  Each ultrasonic transducer 10a includes, for example, a piezoelectric ceramic represented by PZT (Pb (lead) zirconate titanate), a polymer piezoelectric element represented by PVDF (polyvinylidene difluoride), and the like. It is comprised by the vibrator | oscillator which formed the electrode at the both ends of the material (piezoelectric body) which has the piezoelectricity. When a pulsed or continuous wave voltage is applied to the electrodes of such a vibrator, the piezoelectric body expands and contracts. By this expansion and contraction, pulsed or continuous wave ultrasonic waves are generated from the respective vibrators, and an ultrasonic beam is formed by combining the ultrasonic waves. Each vibrator expands and contracts by receiving propagating ultrasonic waves and generates an electrical signal. These electrical signals are output as ultrasonic reception signals.

  The scanning control unit 11 sequentially sets the transmission direction of the ultrasonic beam and the reception direction of the ultrasonic echo. The transmission delay pattern storage unit 12 stores a plurality of transmission delay patterns used when forming an ultrasonic beam. The transmission control unit 13 selects one pattern from a plurality of delay patterns stored in the transmission delay pattern storage unit 12 according to the transmission direction set in the scanning control unit 11, and based on the pattern The delay times given to the drive signals of the plurality of ultrasonic transducers 10a are set. Alternatively, the transmission control unit 13 may set the delay time so that ultrasonic waves transmitted at a time from the plurality of ultrasonic transducers 10a reach the entire imaging region of the subject.

  For example, the drive signal generator 14 includes a plurality of pulsars corresponding to the plurality of ultrasonic transducers 10a. The drive signal generation unit 14 sends a plurality of drive signals to the ultrasonic probe 10 so that the ultrasonic waves transmitted from the plurality of ultrasonic transducers 10a form an ultrasonic beam according to the delay time set by the transmission control unit 13. A plurality of drive signals are supplied to the ultrasonic probe 10 so that the ultrasonic waves supplied or transmitted from the plurality of ultrasonic transducers 10a at a time reach the entire imaging region of the subject.

  The reception signal processing unit 21 includes a plurality of amplifiers (preamplifiers) 21a and a plurality of A / D converters 21b corresponding to the plurality of ultrasonic transducers 10a. The reception signal output from the ultrasonic transducer 10a is amplified by the amplifier 21a, and the analog reception signal output from the amplifier 21a is converted into a digital reception signal by the A / D converter 21b. The A / D converter 21 b outputs a digital reception signal to the reception control unit 23.

  The reception delay pattern storage unit 22 stores a plurality of reception delay patterns used when receiving focus processing is performed on a plurality of reception signals output from the plurality of ultrasonic transducers 10a. The reception control unit 23 selects one pattern from the plurality of reception delay patterns stored in the reception delay pattern storage unit 22 based on the reception direction set in the scanning control unit 11, and the reception delay pattern Based on the set sound velocity value, a reception focus process is performed by adding a delay to a plurality of reception signals. By this reception focus processing, a reception signal (sound ray signal) in which the focus of the ultrasonic echo is narrowed is formed. Further, the reception control unit 23 performs envelope detection processing on the formed sound ray signal.

  Here, the delay amount of the reception signal in the reception focus process is determined based on the sound speed in the subject. In general, 1530 m / s or 1540 m / s is set as the in-vivo sound velocity value C0, but actually, the sound velocity value differs depending on the tissue in the living body. Therefore, by setting the average sound velocity Ci in the subject and multiplying the delay amount D0 (j) in the reception delay pattern by (C0 / Ci), a plurality of delay amounts D1 (j) = (C0 / Ci) · D0. (J) is determined (j = 1, 2,..., N). Where N is the number of ultrasonic transducers used.

  The B-mode image signal generation unit 30 generates a B-mode image signal that is tomographic image information related to the tissue in the subject based on the sound ray signal generated by the reception control unit 23. For this purpose, the B-mode image signal generation unit 30 includes an STC (sensitivity time control) unit 31 and a DSC (digital scan converter) 32.

  The STC unit 31 corrects the attenuation due to the distance on the sound ray signal generated by the reception control unit 23 according to the depth of the ultrasonic reflection position. Further, the DSC 32 converts the sound ray signal corrected by the STC unit 31 into an image signal in accordance with a normal television signal scanning method (raster conversion), and performs necessary image processing such as gradation processing to obtain B A mode image signal is generated. An ultrasonic image is displayed on the display unit 52 based on the B-mode image signal generated by the B-mode image signal generation unit 30.

  The control unit 62 controls the sound speed value calculation unit 42 so as to sequentially change the set sound speed value Ci in parallel with the generation of the B mode image signal by the B mode image signal generation unit 30. The focus determination unit 41 determines the beam convergence in the reception focus process when the set sound speed value Ci is sequentially changed for a plurality of regions in the ultrasonic image.

  For example, the focus determination unit 41 performs a fast Fourier transform on the sound ray signal generated by the reception control unit 23 so that the ratio of the high frequency component in the sound ray signal (for example, the ratio of the high frequency component to the mid frequency component) is increased. It may be determined that the beam focusing degree is the maximum when the maximum value is reached, or the B-mode image signal generated by the B-mode image signal generation unit 30 is subjected to fast Fourier transform to obtain a space in the B-mode image signal. It may be determined that the beam focusing degree is maximum when the ratio of the high frequency component of the frequency becomes maximum.

  The sound speed value calculation unit 42 acquires the sound speed and thickness of the acoustic coupler 100 attached to the ultrasonic probe 10 from the coupler information storage unit 102. Then, the sound velocity value calculation unit 42 acquires the first average sound velocity in the path from the ultrasonic probe 10 to the first region (near the boundary between the subject and the acoustic coupler 100) acquired from the coupler information storage unit 102. The sound speed of the coupler 100 is set. Further, the sound velocity value calculation unit 42 obtains a second average sound velocity in a path from at least the ultrasonic probe 10 to the second region (region in the subject) according to the determination result of the focus determination unit 41. Furthermore, the sound velocity value calculation unit 42 reaches from the first region to the second region based on the first and second average sound velocities and the distances from the ultrasonic probe 10 to the first and second regions. The average sound speed in the path (the third area from the first area to the second area) is calculated. By repeating such calculation for a plurality of regions in the subject, the sound speed (local sound speed) in each region in the subject can be calculated.

  The sound speed map creating unit 43 generates an image signal representing a sound speed map that displays the sound speed distribution in the subject based on the average sound speed calculated for the plurality of regions by the sound speed value calculating unit 42. The image display control unit 51 is a B-mode image signal generated by the B-mode image signal generation unit 30 and an image signal representing a sound speed map generated by the sound speed map generation unit 43 in accordance with an operation of the operator using the console 61. Is selected to generate an image signal for display. The display unit 52 includes, for example, a display device such as a CRT or LCD, and displays an ultrasonic image or a sound velocity map based on a display image signal.

  The control unit 62 controls the scanning control unit 11, the B-mode image signal generation unit 30, the focus determination unit 41, and the like according to an operator's operation using the console 61. In the present embodiment, the scanning control unit 11, the transmission control unit 13, the reception control unit 23 to the image display control unit 51, and the control unit 62 are configured by a CPU and software (program). Or an analog circuit. The software (program) is stored in the storage unit 63. As a recording medium in the storage unit 63, a flexible disk, MO, MT, RAM, CD-ROM, DVD-ROM, or the like can be used in addition to the built-in hard disk.

  Next, the sound speed estimation method used in the ultrasonic diagnostic apparatus shown in FIG. 1 will be described in detail.

  FIG. 2 is a flowchart showing a sound speed estimation method used in the ultrasonic diagnostic apparatus shown in FIG. 1, and FIG. 3 is a diagram showing a relative positional relationship between the ultrasonic probe and the region of interest. In FIG. 3, it is assumed that a region of interest (ROI) is located directly below the ultrasonic probe 10 in order to simplify the description.

  First, when the operator operates the console 61 to instruct the creation of a sound velocity map, the flowchart shown in FIG. 2 is started.

  First, the sound velocity value calculation unit 42 acquires the sound velocity V and the thickness D of the acoustic coupler 100 attached to the ultrasonic probe 10 from the coupler information storage unit 102 (step S10).

  Next, the sound velocity value calculation unit 42 sets ROI1 at the boundary between the acoustic coupler 100 and the subject (step S12). However, the ROI 1 is not limited to the boundary between the acoustic coupler 100 and the subject and may be inside the acoustic coupler 100.

  Next, the sound velocity value calculation unit 42 sets ROI2 in the subject (step S14). The ROI 2 is set as the ROI 2 by designating the region designated in the subject when the operator operates the console 61.

  As a result, as shown in FIG. 3, ROI1 is set at the boundary between the acoustic coupler 100 and the subject at the position of the distance (depth) d1 (= D) from the ultrasound probe 10, and the distance (from the ultrasound probe 10) ROI2 is set in the subject at the position of depth (d1 + d2).

Next, the sound velocity value calculation unit 42 sets the sound velocity V of the acoustic coupler 100 as the average sound velocity C1 in the path from the ultrasonic probe 10 to the ROI ₁ (step S16).

  Next, the sound speed value calculation unit 42 sequentially changes the set sound speed value, and the reception control unit 23 performs reception focus processing (step S18). Subsequently, the focus determination unit 41 or the operator determines the beam convergence degree in the reception focus process when the set sound velocity value is sequentially changed for at least ROI 2 (step S20).

  For example, when the focus determination unit 41 performs fast Fourier transform on the sound ray signal generated by the reception control unit 23, the ratio of the high frequency component in the sound ray signal (for example, the ratio of the high frequency component to the mid frequency component). It may be determined that the beam focusing degree is the maximum when the maximum value is reached, or the B-mode image signal generated by the B-mode image signal generation unit 30 is subjected to fast Fourier transform to obtain a space in the B-mode image signal. It may be determined that the beam focusing degree is maximum when the ratio of the high frequency component of the frequency becomes maximum. Alternatively, the operator may determine the beam focusing degree in the reception focus process based on the image quality of the ultrasonic image displayed on the display unit 52.

Here, it is appropriate to consider that the set sound speed value when the image quality in the ROI 2 is optimum is the average sound speed C ₂ in the path from the ultrasonic probe 10 to the ROI 2 (depth d1 + d2). This is because the image quality is optimal in ROI 2, and it is considered that the ultrasonic beam is most focused in ROI 2. The amount of delay given to the vibrator at this time is equal to the delay time calculated based on the set sound speed value for the entire path regardless of the sound speed distribution of the path.

Then, sound velocity calculation unit 42, based on the set sound velocity for beam focusing degree (quality of ultrasound images) to the maximum in ROI2, obtaining an average acoustic velocity C ₂ in the path leading to the ultrasonic probe 10 ROI2 ( Step S22).

Then, sound velocity calculation unit 42, an average acoustic velocity _{C 1} and _{C 2,} based on the distance from the ultrasonic probe 10 to the ROI1 and ROI2, calculates the average speed of sound Cx in the pathway leading to the ROI2 from ROI1 (step S22).

Here, if the sound velocity according to the distance (depth) from the ultrasonic probe 10 is g (x), the average sound velocity C ₁ in the path from the ultrasonic probe 10 to the ROI ₁ is expressed by the following equation (1). Is done. Incidentally, as described above, the average acoustic velocity C ₁ is the acoustic velocity V of the acoustic coupler 100 is set.

Similarly, the average acoustic velocity _{C 2} in the path leading to the ultrasonic probe 10 ROI2 is expressed by the following equation (2).

  However, the average sound velocity Cx in the route from ROI1 to ROI2 is expressed by the following equation (3).

Based on the equation (2), to represent the average acoustic velocity Cx using an average acoustic velocity _{C 1} and _{C 2,} so that the following equation (4).

  Equation (4) gives the average sound velocity in the region from ROI1 to ROI2. If the interval between the two ROIs is shortened, the local sound velocity in the region near the surface of the subject can be accurately obtained. That is, by setting ROI1 near the boundary (preferably the boundary) between the acoustic coupler 100 and the subject, and setting ROI2 near the surface in the subject (for example, the surface layer), the local sound speed between the regions can be accurately determined. Can be sought. Further, after obtaining the local sound speed between the ROI1 and ROI2 areas, in order to obtain the local sound speed in a deeper area, ROI2 is set to a new ROI1, and a new ROI2 is formed in an area deeper than the new ROI1. Set. Then, the average sound speed in the new ROI1 is the distance to the original ROI1 obtained by multiplying the distance to the new ROI1 by the average sound speed in the original ROI1 and the time to that area, and the area of the original ROI1 and ROI2. The sum of the distances between the original ROI1 and ROI2 obtained by multiplying the local sound speed between them and the time between them is obtained by dividing by the time until the new ROI1. The average sound speed of the new ROI 2 is obtained by the same method as the method of obtaining the average sound speed of the original ROI 2. When the average sound speed of the new ROI1 and ROI2 is obtained in this way, the local sound speed between the new ROI1 and ROI2 areas is calculated in the same manner as the local sound speed between the original ROI1 and ROI2 areas. Can be sought. Thus, after obtaining the local sound velocity near the surface in the subject, the local sound velocity in each region is repeatedly obtained while gradually shifting ROI1 and ROI2 toward the deep portion of the subject. It is possible to accurately obtain the local sound speed even in a deep region within the subject without accumulation of errors near the surface. Further, if the setting of the ROI is sequentially switched and the sound speed of each part is calculated for the entire ultrasound image, a sound speed map can be created.

According to this embodiment, on the basis of the ultrasonic probe 10 first the average acoustic velocity _{C 1} in the path leading to ROI1, the second and the average acoustic velocity _{C 2} in a path from the ultrasonic probe 10 in ROI2, from ROI1 When calculating the average sound velocity Cx in ROI2, ROI1 is set in the vicinity of the boundary between the subject and the acoustic coupler 100 with the acoustic coupler 100 interposed between the ultrasonic probe 10 and the subject. by setting the sound velocity V of the acoustic coupler as an average acoustic velocity C _1, it can be from the first region to improve the calculation accuracy of the mean sound velocity Cx in the second region. Thereby, the sound speed (local sound speed) in a desired region in the subject can be accurately obtained.

  The ultrasonic diagnostic apparatus and the sound speed estimation method according to 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 gist of the present invention. Of course you can go.

  DESCRIPTION OF SYMBOLS 10 ... Ultrasonic probe, 10a ... Ultrasonic transducer, 11 ... Scan control part, 12 ... Transmission delay pattern memory | storage part, 13 ... Transmission control part, 14 ... Drive signal generation part, 21 ... Received signal processing part, 21a ... Amplifier, 21b ... A / D converter, 22 ... Reception delay pattern storage unit, 23 ... Reception control unit, 30 ... B mode image signal generation unit, 31 ... STC unit, 32 ... DSC, 41 ... Focus determination unit, 42 ... Sonic value Calculation unit, 43 ... sound velocity map creation unit, 51 ... image display control unit, 52 ... display unit, 61 ... console, 62 ... control unit, 63 ... storage unit, 100 ... acoustic coupler, 102 ... coupler information storage unit, 104 ... Identification member, 106 ... Coupler information reading means

Claims (10)

An ultrasonic probe including a plurality of ultrasonic transducers that transmit ultrasonic waves to a subject according to a plurality of drive signals and output a plurality of received signals by receiving ultrasonic echoes propagating from the subject;
A member interposed between the ultrasonic probe and the subject, an acoustic coupler that propagates ultrasonic waves at a predetermined sound velocity;
A sound velocity value calculating means for obtaining an average sound velocity of the subject,
The sound velocity value calculation means is an ultrasonic diagnostic apparatus that performs an average sound velocity on the surface layer of a subject based on the sound velocity of the acoustic coupler.   The ultrasonic diagnostic apparatus according to claim 1, wherein the acoustic coupler has a predetermined thickness in an ultrasonic transmission / reception direction of the ultrasonic probe. An ultrasonic probe including a plurality of ultrasonic transducers that transmit ultrasonic waves to a subject according to a plurality of drive signals and output a plurality of received signals by receiving ultrasonic echoes propagating from the subject;
An acoustic coupler that is interposed between the ultrasonic probe and a subject, has a predetermined thickness in the ultrasonic transmission / reception direction of the ultrasonic probe, and propagates ultrasonic waves at a predetermined sound velocity;
A plurality of drive signals are supplied to the plurality of ultrasonic transducers, and a reception focus process and a detection process are performed on the plurality of reception signals output from the plurality of ultrasonic transducers, so that the ultrasonic reception direction can be obtained. Signal processing means for generating a sound ray signal along;
Image signal generating means for generating an image signal representing an ultrasonic image based on the sound ray signal generated by the signal processing means;
A region setting means for setting a first region in the vicinity of a boundary between the subject and the acoustic coupler, and for setting a second region in the subject;
Focus determination means for determining the beam convergence in the reception focus processing when the set sound velocity value is sequentially changed for the second region in the subject;
A sound speed setting means for setting a first average sound speed in a path from the ultrasonic probe to the first region as a sound speed of the acoustic coupler;
According to the determination result of the focus determination means, at least a second average sound velocity in a path from the ultrasonic probe to the second region is obtained, and the first and second average sound velocities and the first and first sound velocity from the ultrasonic probe are determined. A sound speed value calculating means for calculating an average sound speed in a path from the first area to the second area based on the distance to the second area;
An ultrasonic diagnostic apparatus comprising:   The ultrasonic diagnostic apparatus according to claim 3, wherein the region setting means sets a first region at a boundary between the acoustic coupler and the subject.   The ultrasonic diagnostic apparatus according to claim 3, wherein the region setting unit sets a first region in the acoustic coupler. The acoustic coupler has an identification member including the thickness and speed of sound of the acoustic coupler,
Coupler information reading means for reading an identification member of the acoustic coupler when the acoustic coupler is attached to the ultrasonic probe,
The sound speed setting means sets a first average sound speed in a path from the ultrasonic probe to a first region as a sound speed of the acoustic coupler based on a reading result by the coupler information reading means. The ultrasonic diagnostic apparatus according to any one of the above. An ultrasonic probe including a plurality of ultrasonic transducers that transmit ultrasonic waves to a subject according to a plurality of drive signals and output a plurality of reception signals by receiving ultrasonic echoes propagated from the subject; An ultrasonic diagnosis comprising: a member interposed between a probe and a subject, an acoustic coupler having a predetermined thickness in an ultrasonic transmission / reception direction of the ultrasonic probe and propagating ultrasonic waves at a predetermined sound velocity A sound speed estimation method using a device,
A plurality of drive signals are supplied to a plurality of ultrasonic transducers in the ultrasonic probe, and reception focus is applied to a plurality of reception signals output from the plurality of ultrasonic transducers that have received an ultrasonic echo propagating from a subject. A sound ray signal generating step for generating a sound ray signal along the reception direction of the ultrasonic waves by performing the processing and the detection processing;
An ultrasonic image generation step for generating an image signal representing an ultrasonic image based on the generated sound ray signal generated in the sound ray signal generation step;
A region setting step of setting a first region in the vicinity of the boundary between the subject and the acoustic coupler, and setting a second region in the subject;
A focus determination step for determining the beam convergence in the reception focus process when the set sound velocity value is sequentially changed for the second region in the subject;
A sound speed setting step of setting a first average sound speed in a path from the ultrasonic probe to the first region as a sound speed of the acoustic coupler;
According to the determination result in the focus determination step, at least a second average sound velocity in a path from the ultrasound probe to the second region is obtained, and the first and second average sound velocities, and the first and first sound velocity from the ultrasound probe are determined. A sound speed value calculating step for calculating an average sound speed in a path from the first area to the second area based on the distance to the second area;
Sound velocity estimation method including   The sound speed estimation method according to claim 7, wherein the region setting step sets a first region at a boundary between the acoustic coupler and the subject.   The sound speed estimation method according to claim 7, wherein the region setting step sets a first region in the acoustic coupler. The acoustic coupler has an identification member including the thickness and speed of sound of the acoustic coupler,
A coupler information reading step of reading an identification member of the acoustic coupler when the acoustic coupler is mounted on the ultrasonic probe;
10. The sound speed setting step sets a first average sound speed in a path from the ultrasonic probe to a first region as a sound speed of the acoustic coupler based on a reading result obtained by the coupler information reading step. The sound speed estimation method according to any one of the above.

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