JP2009061086A - Ultrasonic diagnostic apparatus, and image processing method and program - Google Patents

Abstract

An ultrasonic diagnostic apparatus capable of obtaining a sound velocity distribution in a subject using data obtained by beam scanning for normal B-mode imaging.
This ultrasonic diagnostic apparatus performs a transmission / reception unit that processes reception signals output from a plurality of ultrasonic transducers, a reception signal storage unit that stores reception signals, and a reception focus process on the reception signals. By supplying the information on the sound velocity value to the reception control unit that generates the sound ray signal and performs the envelope detection processing, the ultrasonic image generation unit that generates the image signal based on the sound ray signal, When the reception control processing is performed on the reception signal read from the reception signal storage unit according to the delay amount set based on the sound speed value, and the sound speed value is changed based on the sound ray signal A sound speed analysis unit that analyzes a change in the degree of beam convergence in the reception focus processing and obtains a two-dimensional sound speed distribution in the subject.
[Selection] Figure 1

Description

  The present invention relates to an ultrasonic diagnostic apparatus that performs imaging of an organ or the like in a living body by transmitting / receiving ultrasonic waves to generate an ultrasonic image used for diagnosis. Furthermore, the present invention relates to an image processing method and an image processing program used in such an ultrasonic diagnostic apparatus.

  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.

  In general, in an ultrasound diagnostic apparatus, an ultrasound probe (probe) including a plurality of ultrasound transducers having an ultrasound transmission / reception function is used. Using such an ultrasonic probe, the subject is scanned with an ultrasonic beam formed by combining a plurality of ultrasonic waves, and ultrasonic echoes reflected inside the subject are received and received. By performing the focus processing, image information relating to a structure (for example, a viscera or a diseased tissue) existing in the subject can be obtained based on the intensity of the ultrasonic echo.

  Normally, reception focus processing is performed assuming that the sound speed in the subject is constant, but in reality, the sound speed varies depending on the tissue in the subject, and this causes a problem that the beam focusing degree deteriorates. A solution to the problem has been proposed.

  As a related technique, Patent Document 1 discloses an ultrasonic diagnostic apparatus aimed at accurately and easily setting an optimum set sound speed value required for electronic beam control. The system control unit of this ultrasonic diagnostic apparatus sets the set sound speed value while superimposing and displaying on the display unit two pre-shooting images obtained by oblique scanning from different directions based on a preset set sound speed value. Are updated sequentially. The delay time calculation unit calculates a delay time for deflecting the ultrasonic beam in the direction using the updated set sound velocity value, and controls the delay times of the transmission unit and the reception unit. The set sound speed value is sequentially updated, and the delay time for beam focusing is set based on the set sound speed value when the deviation between the two images superimposed and displayed on the display unit is minimized. Done. However, such a sound velocity value setting method is difficult to obtain with a device other than a linear probe, and a frame rate is deteriorated because the same region is scanned a plurality of times.

Further, Patent Document 2 discloses an ultrasonic diagnostic apparatus for measuring a two-dimensional distribution of local sound speed in a living body by moving a region of interest where the local sound speed is to be measured. This ultrasonic imaging apparatus includes at least two transmission ultrasonic transducers that transmit an ultrasonic beam into a living body, and at least two transmission regions that are arranged so that a reception region intersects a transmission region of each of the transmission ultrasonic transducers. The ultrasonic beam transmitted from one receiving ultrasonic transducer and at least two transmitting ultrasonic transducers is reflected at different points in the living body and then received by at least two receiving ultrasonic transducers. A means for measuring a time difference, a means for obtaining a local sound velocity in the living body from the time difference, and an interval between at least two ultrasonic transducers and / or an angle of an ultrasonic beam transmitted from the transmitting ultrasonic transducer. By changing the crossing area between the transmission area and the reception area, And means for moving the directionally. However, such a sound speed measurement method is difficult to realize with a convex type probe, and requires beam scanning different from B-mode imaging, which complicates design and increases costs.
Japanese Patent Laying-Open No. 2005-46193 (first page, FIG. 6) JP 62-254740 (page 1-2, Fig. 1)

  Therefore, in view of the above points, the present invention uses any data obtained by beam scanning for normal B-mode imaging, regardless of the type of ultrasonic probe, and the sound velocity in the subject. An object of the present invention is to provide an ultrasonic diagnostic apparatus capable of obtaining the distribution. Furthermore, an object of the present invention is to provide an image processing method and an image processing program used in such an ultrasonic diagnostic apparatus.

  In order to solve the above-described problem, an ultrasonic diagnostic apparatus according to an aspect of the present invention supplies a plurality of drive signals to a plurality of ultrasonic transducers, transmits ultrasonic waves toward the subject, A transmission / reception unit that processes a plurality of reception signals respectively output from a plurality of ultrasonic transducers that have received ultrasonic echoes propagated from the reception unit, a reception signal storage unit that stores a plurality of reception signals output from the transmission / reception unit, and transmission / reception The sound ray signal along the reception direction of the ultrasonic wave by performing reception focus processing by matching the phases of the plurality of reception signals output from the reception unit or the plurality of reception signals read out from the reception signal storage unit And a reception control means for performing envelope detection processing on the generated sound ray signal, and an image representing an ultrasonic image based on the sound ray signal output from the reception control means. A plurality of ultrasonic image generation means for generating a signal, and a plurality of information set based on the sound speed value for a plurality of reception signals read from the reception signal storage unit by supplying information related to the sound speed value to the reception control means. In response to the delay amount, the reception control means performs reception focus processing, and based on the sound ray signal output from the reception control means, analyzes the change in beam convergence in the reception focus processing when the sound velocity value is changed. Sound speed analysis means for obtaining a two-dimensional sound speed distribution in the subject.

  In addition, an image processing method according to one aspect of the present invention is configured to supply a plurality of drive signals to a plurality of ultrasonic transducers, transmit an ultrasonic wave toward the subject, and transmit an ultrasonic echo propagated from the subject. Is an image processing method used in an ultrasonic diagnostic apparatus for processing a plurality of reception signals respectively output from a plurality of ultrasonic transducers, and storing a plurality of reception signals in a reception signal storage unit and a plurality of reception signals By performing reception focus processing by matching the phase of the reception signal, a sound ray signal along the ultrasonic wave reception direction is generated, envelope detection processing is performed on the generated sound ray signal, and the sound is detected. A step (a) for generating an image signal representing an ultrasonic image based on the line signal, and a plurality of received signals read from the received signal storage unit are set based on the sound velocity value. A sound ray signal is generated by performing reception focus processing according to a plurality of delay amounts, and envelope detection processing is performed on the generated sound ray signal, and a sound speed value is changed based on the sound ray signal. Analyzing the change of the beam focusing degree in the reception focus processing at the time of the determination, and obtaining a two-dimensional sound velocity distribution in the subject.

  Furthermore, an image processing program according to one aspect of the present invention supplies ultrasonic signals to a subject by supplying a plurality of drive signals to a plurality of ultrasonic transducers, and transmits an ultrasonic echo propagated from the subject. Is an image processing program used in an ultrasonic diagnostic apparatus that processes a plurality of reception signals respectively output from a plurality of ultrasonic transducers, and stores a plurality of reception signals in a reception signal storage unit and a plurality of reception signals By performing reception focus processing by matching the phase of the reception signal, a sound ray signal along the ultrasonic wave reception direction is generated, envelope detection processing is performed on the generated sound ray signal, and the sound is detected. A procedure (a) for generating an image signal representing an ultrasonic image based on a line signal, and a sound speed value for a plurality of reception signals read from the reception signal storage unit A sound ray signal is generated by performing reception focus processing in accordance with a plurality of delay amounts set based on the delay amount, envelope detection processing is performed on the generated sound ray signal, and sound velocity is calculated based on the sound ray signal. The CPU is caused to execute the procedure (b) for analyzing the change in the degree of beam convergence in the reception focus process when the value is changed and obtaining the two-dimensional sound velocity distribution in the subject.

  According to the present invention, the received signal stored in the received signal storage unit is used to analyze the change in the degree of beam convergence in the reception focus process when the sound speed value is changed, and to analyze the two-dimensional sound speed distribution in the subject. Therefore, regardless of what type of ultrasonic probe is used, the sound speed distribution in the subject can be obtained using data obtained by beam scanning for normal B-mode imaging.

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. Signal storage unit 22, reception delay pattern storage unit 23, reception control unit 24, B-mode image generation unit 30, sound speed analysis unit 40, image reconstruction unit 51, image display control unit 52, D / An A converter 53, a display unit 54, a console 55, a control unit 56, and a storage unit 57 are provided.

  The ultrasonic probe 10 may be an external probe such as a linear scan method, a convex scan method, or a sector scan method, or an ultrasonic endoscope probe such as an electronic radial scan method or a mechanical radial scan method. 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 based on the applied drive signals, receive propagating ultrasonic echoes, and output reception signals.

  Each ultrasonic transducer is, for example, a piezoelectric ceramic represented by PZT (Pb (lead) zirconate titanate) or a polymer piezoelectric element represented by PVDF (polyvinylidene difluoride). It is constituted by a vibrator in which electrodes are formed at both ends of a piezoelectric material (piezoelectric body). When a voltage is applied to the electrodes of such a vibrator by sending a pulsed or continuous wave electric signal, 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 scanning of the subject by the ultrasonic beam may be performed electronically or mechanically. 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 transmits the plurality of drive signals to the ultrasonic probe 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. 10 or a plurality of drive signals are supplied to the ultrasound probe 10 so that the ultrasonic waves transmitted from the plurality of ultrasound 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 (reception data) by the A / D converter 21b. The A / D converter 21 b supplies a digital reception signal to the reception signal storage unit 22 and the reception control unit 24. The reception signal storage unit 22 is configured by a memory or the like, and stores the reception signal supplied from the A / D converter 21b. The received signal stored in the received signal storage unit 22 is used to analyze the sound speed in the subject.

  The reception delay pattern storage unit 23 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 24 selects one pattern from a plurality of reception delay patterns stored in the reception delay pattern storage unit 23 based on the reception direction set in the scanning control unit 11, and based on the pattern. Thus, the reception focus processing is performed by adding a delay to the plurality of reception signals output from the reception signal processing unit 21. By this reception focus processing, a sound ray signal in which the focus of the ultrasonic echo is narrowed is generated. Further, the reception control unit 24 performs envelope detection processing on the formed sound ray signal.

  The B-mode image 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 output from the reception control unit 24. For this purpose, the B-mode image generation unit 30 includes a sound ray signal storage unit 31, an STC (sensitivity time control) unit 32, and a DSC (digital scan converter) 33.

  The sound ray signal storage unit 31 includes a memory or the like, and temporarily stores a sound ray signal (sound ray data) output from the reception control unit 24. The STC unit 32 corrects attenuation with respect to the sound ray signal read from the sound ray signal storage unit 31 according to the depth of the reflection position of the ultrasonic wave. The DSC 33 converts (raster conversion) the sound ray signal corrected by the STC unit 32 into an image signal in accordance with a normal television signal scanning method, and performs necessary image processing such as gradation processing to thereby obtain a B-mode image. Generate a signal.

  In this embodiment, for example, in the freeze mode (a mode in which the same screen is repeatedly displayed based on stored data), the control unit 56 analyzes the sound speed in the subject according to the operator's instruction. The analysis unit 40 and the like are controlled. As a result, the sound speed analysis unit 40 supplies information related to the sound speed value to the reception control unit 24. The reception control unit 24 matches the phases of the plurality of reception signals read from the reception signal storage unit 22 according to the plurality of delay amounts set based on the information about the sound speed value supplied from the sound speed analysis unit 40. Perform receive focus processing.

  In general, 1530 m / s or 1540 m / s is used as the sound velocity value C0 in the human body, but actually, the sound velocity value varies depending on tissues in the human body. Therefore, a plurality of delay amounts D1 (j) = (C0 / Ci) · D0 are set by setting the sound velocity value Ci in the subject and multiplying the delay amount D0 (j) in the reception delay pattern by (C0 / Ci). (J) is set (j = 1, 2,..., L). L is the number of ultrasonic transducers used.

  The sound speed analysis unit 40 analyzes the change in the degree of beam convergence in the reception focus process when the sound speed value is changed based on the sound ray signal output from the reception control unit 24, and performs two-dimensional sound speed in the subject. Find the distribution. For this purpose, the sound speed analysis unit 40 includes a sound ray signal storage unit 41, a band limited image generation unit 42, a focus determination unit 43, a sound speed map image generation unit 44, and an analysis control unit 45.

  The analysis control unit 45 sequentially supplies information related to a plurality of different sound velocity values Ci (i = 1, 2,..., K) to the reception control unit 24. The sound ray signal storage unit 41 is configured by a memory or the like, and temporarily stores a sound ray signal (sound ray data) output from the reception control unit 24. The band limited image generation unit 42 generates a band limited image signal by limiting the frequency band of the sound ray signal read from the sound ray signal storage unit 41. The focus determination unit 43 calculates K focus determination values in the band limited image signal generated by the band limited image generation unit 42 for a plurality of different sound velocity values Ci (i = 1, 2,..., K). Then, the optimum sound speed value is obtained based on the focus determination values.

  The sound velocity map image generation unit 44 obtains a two-dimensional sound velocity distribution in the subject based on the optimum sound velocity value obtained for each region of the ultrasonic image, and further generates an image signal representing the sound velocity map of the entire ultrasonic image. Generate. The image signal representing the sound velocity map is output to the DSC 33 and converted (raster conversion) into an image signal in accordance with a normal television signal scanning method.

  On the other hand, the image reconstruction unit 51 reconstructs an ultrasound image represented by the image signal generated by the B-mode image generation unit 30 based on the two-dimensional sound speed distribution in the subject obtained by the sound speed analysis unit 40. Constitute.

  The image display control unit 52 includes an ultrasonic image based on the B mode image signal generated by the B mode image generation unit 27, an ultrasonic image based on the B mode image signal reconstructed by the image reconstruction unit 51, An image signal for display is generated by selecting one of the sound velocity maps based on the image signal generated by the map image generation unit 44 or combining a plurality of sound speed maps. The D / A converter 53 converts the digital image signal output from the image display control unit 52 into an analog image signal. The display unit 54 includes, for example, a display device such as a CRT or LCD, and displays an ultrasonic image based on an analog image signal.

  The control unit 56 controls the scanning control unit 11, the B-mode image generation unit 30, the sound speed analysis unit 40, the image display control unit 52, and the like according to the operation of the operator using the console 55. The console 55 is provided with operation means (sound speed analysis button) 55a operated by the operator to start the sound speed analysis operation of the sound speed analysis unit 40. When the operator presses the sound speed analysis button 55a, the control unit 56 controls each part to enter the freeze mode, and causes the sound speed analysis unit 40 or the like to perform a sound speed analysis operation.

  In the present embodiment, the scan control unit 11, the transmission control unit 13, the reception control unit 24, the STC 32, the DSC 33, the band limited image generation unit 42 to the image display control unit 52, and the control unit 56 include a CPU and software (program However, these may be constituted by a digital circuit or an analog circuit. The software (program) is stored in the storage unit 57. As a recording medium in the storage unit 57, 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 analysis unit 40 shown in FIG. 1 will be described in detail with reference to FIGS.
FIG. 2 is a diagram for explaining the operation of the sound velocity analysis unit shown in FIG. In the XY plane shown in FIG. 2, X takes any value from 1 to N, and Y takes any value from 1 to N. In order to perform reception focus processing of a reception signal on an ultrasonic image in a region Rn (5 × 5 pixels in FIG. 1) centered on the pixel Mn (X, Y), the analysis control unit 45 includes a plurality of different sound speeds. Information regarding the values Ci (i = 1, 2,..., K) is sequentially supplied to the reception control unit 24. The reception control unit 24 performs a reception focus process by matching the phases of a plurality of reception signals read from the reception signal storage unit 22 according to a plurality of delay amounts set based on the sound velocity value Ci, thereby performing pixel focusing. A sound ray signal corresponding to the region Rn centering on Mn (X, Y) is output.

  The sound ray signal output from the reception control unit 24 is temporarily stored in the sound ray signal storage unit 41. The band limited image generation unit 42 generates a band limited image signal by performing high-pass filter processing or band-pass filter processing on the sound ray signal read from the sound ray signal storage unit 41. At that time, the frequency band of the band limited image signal may be set according to the frequency of the ultrasonic wave to be transmitted and / or the depth of the focus formed in the subject.

  3 is a diagram illustrating a first configuration example of the band limited image generation unit illustrated in FIG. 1, and FIG. 4 illustrates an image represented by the image data generated by the band limited image generation unit illustrated in FIG. It is a figure which shows a spatial frequency band.

As illustrated in FIG. 3, the band limited image generation unit 42 a according to the first configuration example includes a downsampling unit 61, an upsampling unit 62, and a subtraction unit 63. The sound ray signal (original data) I _{ORG for} one frame read from the sound ray signal storage unit 41 is subjected to filtering processing such as thinning-out processing and Nyquist filter processing by the downsampling unit 61. Thereby, down-sampling data _IDWN having a small data size is generated.

Next, the down-sampling data I _DWN is subjected to a filtering process such as a process of inserting “0” value data and a smoothing filter process in the up-sampling unit 62. Thereby, up-sampling data (low-resolution image signal) I _LOW having the same data size as the original sound ray data I _ORG is obtained. As shown in FIG. 4, the up-sampling data I _LOW has a spatial frequency component lower than the cutoff frequency f _C and represents a blurred image with a low resolution.

Next, the subtracting unit 63 performs processing for subtracting the up-sampling data I _LOW from the original data I _{ORG as} shown in the following equation (1). Thereby, subband data I _SUB is obtained.
I _SUB = | I _ORG -I _LOW | (1)

As shown in FIG. 4, the subband data I _SUB has a higher spatial frequency component than the cutoff frequency f _C. In this way, the band limited image generation unit 42a generates a band limited image signal by performing high-pass filter processing on the original data I _ORG .

The control unit 56 sets the cut-off frequency f _C according to the frequency of the transmitted ultrasonic wave and / or the depth of the focal point formed in the subject. For example, the control unit 56 increases the cut-off frequency f _C when the ultrasonic frequency is high, and decreases the cut-off frequency f _C when the ultrasonic frequency is low. Further, the control unit 56 increases the cutoff frequency f _C when the depth of focus is shallow, and decreases the cutoff frequency f _C when the depth of focus is deep.

  FIG. 5 is a diagram illustrating a second configuration example of the band-limited image generation unit illustrated in FIG. 1, and FIG. 6 illustrates an image represented by the image data generated by the band-limited image generation unit illustrated in FIG. It is a figure which shows a spatial frequency band.

As shown in FIG. 5, the band limited image generation unit 42b according to the second configuration example includes downsampling units 71 and 74, upsampling units 72 and 75, and subtraction units 73, 76, and 77. . The sound ray signal (original data) I _{ORG for} one frame read out from the sound ray signal storage unit 41 is subjected to filter processing such as thinning-out processing and Nyquist filter processing by the downsampling unit 71. Thereby, downsampling data I _DWN1 having a small data size is generated.

Next, the downsampling data I _DWN1 is subjected to filtering processing such as processing for inserting data of “0” value and smoothing filtering processing in the upsampling unit 72. Thereby, up-sampling data (low-resolution image signal) I _LOW having the same data size as the original sound ray data I _ORG is obtained. As shown in FIG. 6, the upsampling data I _LOW has a spatial frequency component lower than the cutoff frequency f _C1 (blurred image resolution 1).

Next, the subtracting unit 73 performs processing for subtracting the up-sampling data I _LOW from the original data I _{ORG as} shown in the following equation (2). Thereby, subband data _ISUB1 is obtained.
I _SUB1 = | I _ORG -I _LOW | (2)

As shown in FIG. 6, the subband data I _SUB1 has a higher spatial frequency component than the cut-off frequency f _C1 . The subband data I _SUB1 is subjected to filter processing such as thinning processing and Nyquist filter processing by the downsampling unit 74. Thereby, down-sampled data I _DWN2 having a small data size is generated.

Next, the down-sampling data I _DWN2 is subjected to filtering processing such as processing for inserting data of “0” value and smoothing filtering processing in the up-sampling unit 75. Thereby, up-sampling data I _MID1 having the same data size as the subband data I _SUB1 is obtained.

The up-sampling data I _MID1 may be used as the band limited image signal. Further, the sub-sampling unit 76 subtracts the up-sampling data I _MID1 from the subband data I _SUB1 as shown in Expression (3). Subband data I _SUB2 and subtracting unit 77 subtracts subband data I _SUB2 from subband data I _SUB1 to generate subband data I _MID2 as shown in equation (4). It may be a restricted image signal.
I _SUB2 = | I _SUB1 -I _MID1 | (3)
I _MID2 = | I _SUB1 -I _SUB2 | (4)

As shown in FIG. 6, the up-sampling data I _MID1 (or subband data I _MID2 ) is higher than the cutoff frequency f _C1 (blur image resolution 1) and lower than the cutoff frequency f _C2 (blur image resolution 2). It has a spatial frequency component. In this way, the band limited image generation unit 42a generates a band limited image by performing the band pass filter process on the original data I _ORG .

The control unit 56 sets the cutoff frequencies f _C1 and f _C2 according to the frequency of the transmitted ultrasonic waves and / or the depth of the focal point formed in the subject. For example, the control unit 56 increases the cutoff frequencies f _C1 and f _C2 when the ultrasonic frequency is high, and decreases the cutoff frequencies f _C1 and f _C2 when the ultrasonic frequency is low. Further, the control unit 56 increases the cutoff frequencies f _C1 and f _C2 when the depth of focus is shallow, and decreases the cutoff frequencies f _C1 and f _C2 when the depth of focus is deep.

Referring again to FIG. 1, the focus determination unit 43 calculates a focus determination value based on the average value or energy value of the band limited image signal generated by the band limited image generation unit 42. For example, assuming that the band limited image signal in one frame is I _SUB (p) (pixel number p = 1, 2,..., M), the focus determination unit 43 uses the band limited image signal I as the focus determination value. average _{I AVE = ΣI SUB (p)} / M of _SUB (p), or the energy value of the band-limited image signal _{I SUB} (p) (image energy _amount) is calculated ^{_{I ENG = ΣI SUB (p)}} 2.

  The operator can set an image region used for calculation of the focus determination value by the focus determination unit 43 by operating the console 55. For example, it is possible to set from the system setting using coordinates and a trackball, or to select a region such as a central portion, a shallow portion, and a deep portion from the system setting. Alternatively, the image area used for calculation of the focus determination value by the focus determination unit 43 may be automatically selected based on the average luminance of a plurality of areas divided in advance. For example, the region having the highest average luminance is selected, or the region having the average luminance closest to the median value is selected.

The focus determination unit 43 calculates K focus determination values in the band limited image signal generated by the band limited image generation unit 42 for a plurality of different sound velocity values Ci (i = 1, 2,..., K). Then, the optimum sound speed value C _OP is obtained based on the focus determination values. For example, the sound speed value with the largest focus determination value is set as the optimum sound speed value C _OP for the pixel. By performing such processing while changing X to 1 to N and changing Y to 1 to N, the optimum sound velocity value C _OP () for each region (pixel Mn (X, Y)) of the ultrasonic image is obtained. X, Y) is required.

The sound velocity map image generation unit 44 obtains a two-dimensional sound velocity distribution in the subject based on the optimum sound velocity value obtained for each region of the ultrasonic image, and further generates an image signal representing the sound velocity map of the entire ultrasonic image. Generate. For example, the subject, the acoustic velocity value C between the first layer is _L1 (surface layer), sound velocity is assumed to include a second layer (deep) is C _L2. Since the ultrasonic wave reflected at the point P1 in the first layer passes only through the first layer, the optimum sound speed value obtained for the point P1 is used as the sound speed value C _L1 of the first layer. it can.

On the other hand, since the ultrasonic wave reflected at the point P2 in the second layer passes through both the first layer and the second layer, the sound velocity map image generation unit 44 uses the second layer. In order to obtain an accurate sound speed value C _L2 within the range, the optimum sound speed value obtained for the point P2 is corrected based on the sound speed value C _L1 of the first layer. In this way, a two-dimensional sound velocity distribution within the subject is obtained. The image signal representing the sound velocity map is output to the DSC 33 and converted (raster conversion) into an image signal in accordance with a normal television signal scanning method.

The image reconstruction unit 51 reconstructs an ultrasound image represented by the image signal generated by the B-mode image generation unit 30 based on the two-dimensional sound speed distribution in the subject obtained by the sound speed analysis unit 40. . That is, the image reconstructing unit 51 determines that the sound velocity value C _L1 of the first layer or the sound velocity value C _L2 of the second layer is different from the standard sound velocity value C0 in the human body due to the difference in the sound velocity value. Correct the misalignment.

Further, since the ultrasonic wave is refracted at the boundary line between the first layer having the sound velocity value C _L1 and the second layer having the sound velocity value C _L2 , the image reconstruction unit 51 performs the B-mode image. You may make it correct | amend the position shift which arises by refraction in the ultrasonic image represented by the image signal produced | generated by the production | generation part 30. FIG. For example, the image reconstruction unit 51 obtains the incident angle θ _I of the sound ray incident on the boundary line from the first layer, and follows the Snell's law expressed by the following equation (5) to generate the second layer from the boundary line. The emission angle θ _T of the sound ray that is emitted from the line is obtained.
(Sin θ _I ) / C _L1 = (sin θ _T ) / C _L2 (5)
By using this relationship, the image reconstruction unit 51 can correct the misalignment that occurs in the second layer.
Thereby, the image quality of the ultrasonic image displayed on the display unit 54 is improved.

  INDUSTRIAL APPLICABILITY The present invention can be used in an ultrasonic diagnostic apparatus that performs imaging of an organ or the like in a living body by transmitting and receiving ultrasonic waves and generates an ultrasonic image used for diagnosis.

1 is a block diagram illustrating a configuration of an ultrasonic diagnostic apparatus according to an embodiment of the present invention. It is a figure for demonstrating operation | movement of the sound speed analysis part shown in FIG. It is a figure which shows the 1st structural example of the band-limited image generation part shown in FIG. It is a figure which shows the spatial frequency band of the image represented by the image data produced | generated by the zone | band limited image generation part shown in FIG. It is a figure which shows the 2nd structural example of the band-limited image generation part shown in FIG. It is a figure which shows the spatial frequency band of the image represented by the image data produced | generated by the band-limited image generation part shown in FIG.

Explanation of symbols

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 Reception signal processing part 21a Amplifier 21b A / D converter 22 Reception signal storage part 23 Reception delay Pattern storage unit 24 Reception control unit 30 B-mode image generation unit 31 Sound ray signal storage unit 32 STC unit 33 DSC
DESCRIPTION OF SYMBOLS 40 Sound speed analysis part 41 Sound ray signal storage part 42, 42a, 42b Band-limited image generation part 43 Focus determination part 44 Sound speed map image generation part 45 Analysis control part 51 Image reconstruction part 52 Image display control part 53 D / A converter 54 display unit 55 console 55a operation means 56 control unit 57 storage unit 61, 71, 74 downsampling unit 62, 72, 75 upsampling unit 63, 73, 76, 77 subtraction unit

Claims (19)

A plurality of drive signals are respectively supplied to the plurality of ultrasonic transducers to transmit ultrasonic waves toward the subject, and a plurality of outputs are output from the plurality of ultrasonic transducers that have received the ultrasonic echoes propagated from the subject. A transmission / reception unit for processing received signals of
A reception signal storage unit for storing a plurality of reception signals output from the transmission / reception unit;
By performing a reception focus process by matching the phases of a plurality of reception signals output from the transmission / reception unit or a plurality of reception signals read from the reception signal storage unit, the ultrasonic wave is aligned along the ultrasonic wave reception direction. A reception control means for generating a sound ray signal and performing envelope detection processing on the generated sound ray signal;
Ultrasonic image generating means for generating an image signal representing an ultrasonic image based on a sound ray signal output from the reception control means;
By supplying information related to the sound speed value to the reception control means, the reception control means is supplied to the reception control means according to a plurality of delay amounts set based on the sound speed value for the plurality of reception signals read from the reception signal storage unit. Based on the sound ray signal output from the reception control means by performing the reception focus process, the change in the beam focusing degree in the reception focus process when the sound speed value is changed is analyzed to analyze the two-dimensional sound speed in the subject. Sound speed analysis means for obtaining the distribution;
An ultrasonic diagnostic apparatus comprising:   Image reconstruction means for reconstructing an ultrasound image represented by an image signal generated by the ultrasound image generation means based on a two-dimensional sound speed distribution in the subject determined by the sound speed analysis means. The ultrasonic diagnostic apparatus according to claim 1. The sound velocity analyzing means is
Analysis control means for sequentially supplying information related to a plurality of different sound velocity values to the reception control means for each region of the ultrasonic image;
Band-limited image generation means for generating a band-limited image signal by limiting the frequency band of the sound ray signal output from the reception control means;
A focus determination unit that calculates a focus determination value in a band-limited image signal generated by the band-limited image generation unit for each region of the ultrasonic image, and obtains an optimum sound speed value based on the focus determination value;
A sound speed map image generating means for generating an image signal representing a sound speed map of the whole ultrasonic image based on the optimum sound speed value obtained for each region of the ultrasonic image;
The ultrasonic diagnostic apparatus according to claim 1, comprising:   The ultrasonic diagnosis according to claim 3, wherein the band-limited image generation unit generates a band-limited image signal by performing high-pass filter processing or band-pass filter processing on the sound ray signal output from the reception control unit. apparatus.   The ultrasonic diagnostic apparatus according to claim 3, wherein the focus determination unit calculates a focus determination value based on an average value or an energy value of a band limited image signal generated by the band limited image generation unit.   The ultrasonic diagnostic apparatus according to claim 3, wherein the sound speed map image generation unit generates an image signal representing a color sound speed map corresponding to a sound speed value.   The ultrasonic diagnostic apparatus according to claim 1, further comprising operation means for starting the operation of the sound speed analysis means. A plurality of drive signals are respectively supplied to the plurality of ultrasonic transducers to transmit ultrasonic waves toward the subject, and a plurality of outputs are output from the plurality of ultrasonic transducers that have received the ultrasonic echoes propagated from the subject. An image processing method used in an ultrasonic diagnostic apparatus for processing a received signal of
A plurality of reception signals are stored in the reception signal storage unit, and a sound ray signal along the ultrasonic reception direction is generated by performing reception focus processing by matching the phases of the plurality of reception signals. Performing an envelope detection process on the sound ray signal, and generating an image signal representing an ultrasonic image based on the sound ray signal;
A sound ray signal is generated by performing reception focus processing on a plurality of reception signals read from the reception signal storage unit according to a plurality of delay amounts set based on a sound velocity value, and the generated sound ray signal Is subjected to an envelope detection process, and based on the sound ray signal, a change in the beam focusing degree in the reception focus process when the sound speed value is changed is analyzed to obtain a two-dimensional sound speed distribution in the subject. Step (b);
An image processing method comprising:   The method further comprises the step (c) of reconstructing an ultrasound image represented by the image signal generated in the step (a) based on the two-dimensional sound velocity distribution in the subject obtained in the step (b). Item 9. The image processing method according to Item 8. Step (b)
For each region of the ultrasonic image, a sound ray signal is generated by performing reception focus processing according to a plurality of delay amounts set based on a plurality of different sound velocity values, and envelope detection is performed on the generated sound ray signal. A step (b1) of applying processing;
(B2) generating a band limited image signal by limiting the frequency band of the sound ray signal obtained in step (b1);
Calculating a focus determination value in the band-limited image signal generated in step (b2) for each region of the ultrasonic image, and obtaining an optimum sound speed value based on the focus determination value (b3);
A step (b4) of generating an image signal representing a sound velocity map of the entire ultrasonic image based on the optimum sound velocity value obtained for each region of the ultrasonic image;
The image processing method of Claim 8 or 9 containing these.   The image processing method according to claim 10, wherein step (b2) includes generating a band-limited image signal by subjecting the sound ray signal obtained in step (b1) to high-pass filter processing or band-pass filter processing. .   The image processing method according to claim 10, wherein step (b3) includes calculating a focus determination value based on an average value or an energy value of the band limited image signal generated in step (b2).   The image processing method according to claim 10, wherein step (b4) includes generating an image signal representing a color sound speed map corresponding to the sound speed value. A plurality of drive signals are respectively supplied to the plurality of ultrasonic transducers to transmit ultrasonic waves toward the subject, and a plurality of outputs are output from the plurality of ultrasonic transducers that have received the ultrasonic echoes propagated from the subject. An image processing program used in an ultrasonic diagnostic apparatus for processing a received signal of
A plurality of reception signals are stored in the reception signal storage unit, and a sound ray signal along the ultrasonic reception direction is generated by performing reception focus processing by matching the phases of the plurality of reception signals. A procedure (a) of performing an envelope detection process on the sound ray signal and generating an image signal representing an ultrasonic image based on the sound ray signal;
A sound ray signal is generated by performing reception focus processing on a plurality of reception signals read from the reception signal storage unit according to a plurality of delay amounts set based on a sound velocity value, and the generated sound ray signal Is subjected to an envelope detection process, and based on the sound ray signal, a change in the beam focusing degree in the reception focus process when the sound speed value is changed is analyzed to obtain a two-dimensional sound speed distribution in the subject. Step (b)
An image processing program for causing a CPU to execute   Based on the two-dimensional sound velocity distribution in the subject obtained in the procedure (b), the CPU is further caused to execute the procedure (c) for reconstructing the ultrasonic image represented by the image signal generated in the procedure (a). The image processing program according to claim 14. Step (b)
For each region of the ultrasonic image, a sound ray signal is generated by performing reception focus processing according to a plurality of delay amounts set based on a plurality of different sound velocity values, and envelope detection is performed on the generated sound ray signal. A procedure (b1) for performing processing;
A step (b2) of generating a band limited image signal by limiting the frequency band of the sound ray signal obtained in the step (b1);
For each region of the ultrasonic image, a procedure (b3) for calculating a focus determination value in the band limited image signal generated in step (b2) and obtaining an optimum sound speed value based on the focus determination value;
A step (b4) of generating an image signal representing a sound velocity map of the entire ultrasonic image based on the optimum sound velocity value obtained for each region of the ultrasonic image;
The image processing program according to claim 14 or 15, further comprising:   The image processing program according to claim 16, wherein step (b2) includes generating a band-limited image signal by subjecting the sound ray signal obtained in step (b1) to high-pass filter processing or band-pass filter processing. .   The image processing program according to claim 16, wherein the step (b3) includes calculating a focus determination value based on an average value or an energy value of the band limited image signal generated in the step (b2).   The image processing program according to claim 16, wherein the step (b4) includes generating an image signal representing a color sound speed map corresponding to the sound speed value.

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