JP2016198119A - Ultrasonic imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic imaging apparatus which can acquire images with a high degree of accuracy by reducing variations of receiving signals between transmissions in aperture synthesis processing.SOLUTION: A reception beam former 108 for performing aperture synthesis processing includes: a delay addition phasing part 204 for phasing by delaying and adding a receiving signal for each transmission for each of one or more reception focuses; a beam memory 206 for storing delay phasing data for each of the reception focuses by the delay addition phasing part 204; and an in-between-transmissions synthesis part 205 which reads and synthesizes the delay phasing data for the same reception focuses out of the delay phasing data for each transmission that is stored in the beam memory. The in-between-transmissions synthesis part 205 synthesizes the delay phasing data after weighting the delay phasing data for each transmission of the same reception focus by a weighting factor.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ultrasound imaging technique for capturing an image in a subject using ultrasound.

  The ultrasound imaging technique is a technique for non-invasively imaging the inside of a subject such as a human body using ultrasound (a sound wave not intended to be heard, generally a sound wave having a high frequency of 20 kHz or higher). It is.

  Since ultrasonic transmission / reception by the ultrasonic imaging apparatus is performed by an array having a finite aperture diameter, it is difficult to improve the resolution in the azimuth direction due to the influence of ultrasonic diffraction by the edge of the aperture. This problem can be solved if an infinitely long array can be prepared, but in reality it is difficult to realize. Therefore, in recent years, channel domain phasing techniques have been actively studied to improve the resolution in the azimuth direction, and new phasing methods such as adaptive beamformers and aperture synthesis have been actively reported.

  The aperture synthesis will be briefly described. First, a delay time is given to each of the reception signals of a plurality of elements constituting the ultrasonic probe, thereby focusing on a certain point and then obtaining a phasing signal obtained by addition. Aperture synthesis is performed by synthesizing and superimposing the phasing signal and the phasing signal obtained by one or more other transmissions / receptions at the same point.

  Aperture synthesis can superimpose phasing signals obtained by transmitting and receiving ultrasonic probes from different directions to a point, giving high resolution of point images and robustness against inhomogeneities. It is expected. Furthermore, since the processing gain is improved by the superimposition processing, it is possible to perform transmission by thinning out the number of ultrasonic transmissions more than usual, and it can be applied to high-speed imaging.

  An object of the invention of Patent Document 1 is to obtain a tomographic image equivalent to a case of photographing from multiple directions while avoiding an increase in hardware and a decrease in frame rate. In Patent Literature 1, the main reflection angle of the ultrasonic wave is obtained from the position of the ultrasonic element having the highest intensity among the reception signals of a plurality of ultrasonic elements, and the addition is performed after weighting the reception signal around the main reflection angle. Thus, a technique for phasing is disclosed.

JP 2004-215987 A

  The present invention solves the following two problems of the conventional aperture synthesis method.

  The first problem is to synthesize the phasing signal of the received signal obtained by aperture synthesis for each of a plurality of transmissions, that is, to synthesize the phasing signal between transmissions. If the error caused by (device) varies between transmissions, it is greatly affected. The inventor has found that the variation of the received signal error caused by the system between transmissions becomes an image error that cannot be ignored when generating an ultrasonic image by aperture synthesis. Variations in transmission of errors caused by the system vary between individual devices, and even in the same device, change due to aging degradation of the probe, failure of the analog transmission / reception circuit, and the like. Therefore, it is necessary to prepare a technique for eliminating the error of the received signal in the time direction between multiple transmissions.

  The second problem is that, for high-speed imaging, aperture transmission was performed because there was less overlap between transmissions in the irradiated area of the transmitted ultrasonic waves when transmission was performed with the number of ultrasonic transmissions reduced than usual. In some cases, blocking noise occurs. This problem is more conspicuous in the focused transmission than in the diffuse transmission because the irradiation area is narrow near the transmission focal point, and an X-shaped blocking artifact occurs near the focal point. This problem can also be solved by reducing the variation in the received signal between transmissions, as in the first problem.

  These first and second problems have not been realized by a method of generating an image with a received signal for each transmission without performing synthesis between transmissions. This is because, by adding the received signal in the channel direction, even if there is a variation in the received signal between transmissions due to an error caused by the transmission / reception system, the influence is finally included in the ultrasonic image. This is because does not appear.

  The technique disclosed in Patent Document 1 performs phasing by weighting and adding each received signal of a plurality of elements, and aperture synthesis processing for adding signals after phasing between a plurality of transmissions is performed. Absent.

  An object of the present invention is to reduce variations in received signals between transmissions in aperture synthesis processing and obtain a highly accurate image.

  The ultrasonic imaging apparatus according to the present invention includes a reception beamformer that performs aperture synthesis processing, and the reception beamformer delays and adds the reception signal for each transmission for each of one or more reception focal points, and phase adjusts the received signal. Delay addition and phasing unit, beam memory storing delay phasing data for each reception focus by delay addition phasing unit for each transmission, and the same reception focus among delay phasing data for each transmission stored in beam memory And an inter-transmission combiner that reads and combines the delayed phasing data.

  The inter-transmission combiner weights the delayed phasing data for each transmission with respect to the same reception focus by applying the respective weighting factors, and then combines them.

  According to the present invention, it is possible to reduce variations in received signals between transmissions by weighting in aperture synthesis processing, so that a highly accurate image can be obtained.

1 is a block diagram showing a configuration of a reception beam former of an ultrasonic imaging apparatus according to a first embodiment. The (a) perspective view of the ultrasonic imaging device of a 1st embodiment, and (b) block diagram. Explanatory drawing for demonstrating the process of the delay addition phasing part 204 of FIG. (A) Explanatory drawing explaining the delay phasing data of the beam memory 206 in FIG. 1, (b) Processing in which the inter-transmission synthesizing unit 205 weights the delay phasing data of the same reception focus for each transmission with a weighting coefficient (C) Explanatory drawing which shows the scanning line of an aperture synthetic | combination image. (A) Explanatory drawing which shows the scanning line of an aperture synthetic image, (b) Explanatory drawing which shows the structure of the weight table 601, (c) Explanatory drawing which shows the structure of the weight table of a comparative example. 5 is a flowchart showing the operation of the ultrasonic imaging apparatus according to the first embodiment. (A) graph showing variation in signal value of delay phased data for each transmission, (b) graph showing weighting factor for each transmission, (c) variation in signal value of delayed phased data after transmission for each transmission Graph showing. The overlap of transmission beams of the ultrasonic imaging apparatus is shown for (a) low-speed imaging for diffusion transmission, (b) high-speed imaging for diffusion transmission, (c) low-speed imaging for focus transmission, and (d) high-speed imaging for focus transmission, respectively. Illustration. The block diagram which shows the structure of the reception beam former of the ultrasonic imaging apparatus of 2nd Embodiment. The perspective view of the ultrasonic imaging apparatus of 2nd Embodiment. 6 is a flowchart showing the operation of the ultrasonic imaging apparatus according to the second embodiment. The block diagram which shows the structure of the reception beam former of the ultrasonic imaging apparatus of 3rd Embodiment. The perspective view of the ultrasonic imaging device of 3rd Embodiment. The block diagram which shows the structure of the reception beam former of the ultrasonic imaging apparatus of 4th Embodiment. 10 is a flowchart showing the operation of the ultrasonic imaging apparatus according to the fourth embodiment. The block diagram which shows the partial structure of the receiving beam former of the ultrasonic imaging apparatus of 5th Embodiment.

  An ultrasonic imaging apparatus according to an embodiment of the present invention will be described.

(First embodiment)
The ultrasonic imaging apparatus according to the first embodiment will be described with reference to FIGS. 1, 2A and 2B. 1 is a block diagram of a part of the apparatus, FIG. 2A is a perspective view of the apparatus, and FIG. 2B is a block diagram showing a schematic configuration of the entire apparatus.

  As shown in FIG. 1 and FIGS. 2A and 2B, the ultrasonic imaging apparatus of the first embodiment includes an ultrasonic element array 101 in which a plurality of ultrasonic elements 105 are arranged along a predetermined direction. The transmission beam former 104 that transmits ultrasonic waves from at least a part (201, 202, 203) of the plurality of ultrasonic elements 105, and the reception that is output from the plurality of ultrasonic elements 105 that have received the ultrasonic waves from the subject 100. A reception beamformer 108 for phasing a signal and an image processing unit 109 for generating image data using a phasing output output from the reception beamformer.

  The reception beamformer 108 is a beamformer that performs aperture synthesis processing. As shown in FIG. 1, the reception beamformer 108 includes a delay addition phasing unit 204 that delays and adds a received signal for each transmission for each of one or more reception focal points, and a delay addition phasing unit 204. A beam memory 206 that stores delay phasing data for each reception focus for each transmission, and a transmission that reads and synthesizes delay phasing data for the same reception focus among the delay phasing data for each transmission stored in the beam memory 206. And an inter-synthesis unit 205.

  The inter-transmission synthesizing unit 205 weights the delayed phasing data for each transmission with respect to the same reception focus by applying the respective weighting factors, and then synthesizes them. As a result, it is possible to suppress an error caused by the system (apparatus device) between transmissions, thereby causing an error in the delayed phasing data and an error that cannot be ignored in the signal after aperture synthesis. Therefore, an ultrasonic image with high resolution can be obtained by aperture synthesis. In addition, when performing high-speed imaging by thinning out the number of transmissions of ultrasonic waves than usual, artifacts caused by aperture synthesis can be prevented and high-resolution ultrasonic images can be obtained even if there is little overlap of irradiation areas between transmissions. Can do.

  The ultrasonic imaging apparatus may include a weight memory 112 that stores a predetermined weight coefficient. As a result, the inter-transmission combining unit 205 can read out the weighting coefficient from the weighting memory and use it for weighting.

  Hereinafter, the ultrasonic imaging apparatus according to the first embodiment will be described more specifically.

  The overall configuration of the ultrasonic imaging apparatus will be further described with reference to FIGS. 1 and 2A and 2B.

  As shown in FIG. 2A, the ultrasonic imaging apparatus includes an ultrasonic probe 106, an apparatus main body 102, an image display unit 103, and a console 110. In the apparatus main body 102, as shown in FIG. 2B, a transmission beamformer 104, a transmission / reception separation circuit (T / R) 107, a reception beamformer 108, an image processing unit 109, and the operation thereof are controlled. A control unit 111 is arranged. The weight memory 112 is disposed in the control unit 111.

  As shown in FIG. 1, the reception beamformer 108 temporarily takes in the weighting coefficient used for the calculation from the weight memory 112 and stores it in addition to the above-described delay addition phasing unit 204, beam memory 206, and inter-transmission synthesis unit 205. A weight table 601 and a frame memory 207 are provided. The ultrasonic probe 106 includes the ultrasonic element array 101 shown in FIG.

  The transmission beam former 104 in FIG. 2B generates a transmission beam signal for generating an ultrasonic transmission beam. The transmission beam signal is transferred to the ultrasonic probe 106 via the transmission / reception separation circuit 107. The ultrasonic probe 106 delivers the transmission beam signal to the ultrasonic elements 105 of the ultrasonic element array 101. The ultrasonic element 105 transmits ultrasonic waves toward the inside of the subject 100. The echo signal reflected in the body is received by the ultrasonic element array 101 of the ultrasonic probe 106. The received signal is subjected to phasing calculation processing and the like in the reception beam former 108 again through the transmission / reception separation circuit 107.

  The phasing process performed by the delay addition phasing unit 204 will be described with reference to FIG. The delay addition phasing unit 204 processes a plurality of reception beams (beam # 1 to beam #M) in parallel from reception data received by the ultrasonic element 105 in response to one transmission of ultrasonic waves by the transmission beam former 104. Generate by. In the present embodiment, the reception beam refers to a set of a plurality of reception focal points arranged linearly in the depth direction. In the specification and the drawings, # is used as a sign indicating a number (No.). In general, the number of reception beams (reception focus sets) is formed as one near the center of the transmission beam, or about 2 to 8 near the center (parallel beam forming). However, the number is not limited to these, and any number may be formed within the directivity angle 10 of the ultrasonic element array 101. Within a directivity angle of 10 (for example, 90 °), 32, 64, 128, etc. reception beams may be generated in parallel.

  Here, as an example, a case will be described in which the delay and addition phasing unit 204 generates a reception beam by using a delay method when the center of the ultrasonic element array 101 is set to time zero. Note that the reception beam may be generated using a delay method (virtual sound source method) in which the transmission focal position is set to time zero.

  In FIG. 3, when phasing the reception signal for the reception focus 11 a of the second reception beam (beam # 2), the delay addition phasing unit 204 outputs the reception signal of the ultrasonic element 105 of the active channel of the ultrasonic element array 101. Each is delayed by applying a delay time represented by a delay curve 12a shown in FIG. Similarly, when phasing the reception signal for the reception focal point 11b, the reception signal is delayed by applying the delay time represented by the delay curve 12b. When phasing is performed for the reception focal points 13a and 13b on the m-th reception beam (beam #m), the reception signals are applied by applying the delay times represented by the delay curves 14a and 14b in FIG. Delay.

  The delay addition phasing unit 204 adds the signals after delaying the received signals. Thereby, delay phasing data is obtained for one reception focus. By performing this calculation for all reception focal points set on the reception beam, a set of delay phasing data is obtained for one reception beam.

  By performing this calculation for all reception focal points on the M reception beams (beam # 1 to beam #M), it is possible to generate delay phasing data of the reception focal point of the sector region 15. That is, an image of the fan-shaped region 15 (that is, a set of reception focal points) as an aggregate of M parallel reception beams is generated by a single transmission and reception of ultrasonic waves from the ultrasonic element array 101. The shape of the aggregate of reception beams may be a fan shape or a reception beam shape in which the beam direction is selected in the normal vector direction of the surface layer of each ultrasonic element 105. Further, it may be an assembly of arbitrary plural beams that covers the range of the transmission beam transmitted by the ultrasonic element 105. In FIG. 3, the ultrasonic element 105 has a linear shape arranged on a straight line, but may have a convex shape with a curved element arrangement. Further, the transmission beam scanning method may be a sector type.

  The obtained delay phasing data for each reception focus is accumulated in the beam memory 206 for each reception beam from the delay addition phasing unit 204 through the inter-transmission synthesis unit 205. Therefore, in the beam memory 206, one image of the sector area 15 configured from the delayed phasing data of the reception focal points of the M reception beams is stored for each transmission / reception of the ultrasonic wave. Since the memory capacity of the beam memory 206 is finite, in order to store the delay phasing data of the received beam obtained by the new transmission / reception, the delay phasing data of the oldest received beam is deleted and updated. However, if you have enough memory to store the delayed phasing data from all transmissions and receptions during ultrasound imaging, you do not need to delete the old data, The phasing data is stored in the beam memory 206.

  Next, the operation of the inter-transmission combining unit 205 will be described with reference to FIG. The inter-transmission synthesizing unit 205 generates an aperture synthesized image by synthesizing the delay phasing data obtained for the reception focus at the same position by different transmissions among the delay phasing data stored in the beam memory 206.

  First, an aperture composite image to be finally formed is determined as shown in FIG. The aperture composite image in FIG. 4C is composed of J scan lines (Scan line # 1 to Scan line #J). Each scanning line includes S reception focal points (σ = 1, 2,... S) in the depth direction. In the specification and FIG. 4, φ is used as a code representing a scanning line number, σ is used as a code indicating a reception focus number, and n is used as a code indicating a transmission (Tx) number.

  The delay phasing data of the reception focus at the same position as the reception focus in the aperture synthesized image is read from the beam memory 206 and synthesized. For example, when the direction of the scanning line of the aperture synthetic image and the interval between the reception focal points correspond to the direction of the reception beam and the interval between the reception focal points calculated by the delay and addition phasing unit 204, respectively, transmission numbers 1, 2,. .. In the fan-shaped area image obtained at N, the reception focal points 21, 22,... 23 at the same position as the s-th reception focal point 24 of the j-th scanning line of the aperture composite image are shown in FIG. As included. The inter-transmission combiner 205 reads out the delayed phasing data of the reception focal points 21, 22,.

  In the present embodiment, when synthesizing the delay phasing data, the inter-transmission synthesizing unit 205 weights and adds the delay phasing data between the transmissions as shown in FIG. 4B. The delay phasing data for each transmission includes variations due to errors caused by the system (device) and block noise during high-speed imaging. Therefore, multiplication is performed as shown in the following equation (1), and calculation is performed. To solve this problem.

  In Equation (1), R (j, s) is delayed phasing data after synthesis of the s-th reception focus of the j-th scanning line of the aperture synthesized image, and r (j, s, n). Is the delay phasing data obtained with the transmission number n, and is the delay phasing data of the reception focal point at the same position as R (j, s) of the aperture synthetic image. w (j, s, n) represents a weighting factor for weighting the delay phasing data r (j, s, n), and is a weighting factor stored in the weighting table 601. That is, as the weighting coefficient w (j, s, n), individual weighting coefficients are set for each transmission number, scanning line number, and reception focus number.

  Note that the direction of the scanning line of the aperture synthesized image and the interval between the reception focal points may not correspond to the direction of the reception beam and the interval between the reception focal points calculated by the delay addition phasing unit 204, respectively. In such a case, the delay phasing data of the reception focus of the reception beam closest to the reception focus of the aperture synthetic image may be used as r (j, s, n) as it is, or linear interpolation such as bilinear interpolation. Alternatively, by using nonlinear interpolation such as bicubic interpolation, r (j, s, n) may be obtained by interpolation calculation from the value of delayed phasing data at a position close to the reception focus of the aperture synthesized image. .

  Next, the weight coefficients stored in the weight table 601 will be described with reference to FIG. The present embodiment is characterized in that weight coefficients are prepared for each transmission for all reception focal points of all scanning lines 1 to J.

  When the total number of scanning lines of the aperture synthetic image is J, the number of reception focal points on one scanning line is S, and the number of transmissions used for one aperture synthesis is N, the weights are as shown in FIG. The table 601 includes a storage area that can store J values, which is the total number of scanning lines, and can store S × N weighting coefficient values. That is, in each table, the weights of the S reception focal points on one scanning line are stored for N transmissions. For example, as shown in FIG. 5A, the weighting coefficient for each transmission of 1 to N times with respect to the s-th reception focus 61 of the second scanning line of the aperture composite image is the second weight in FIG. It is stored in row 62 of the scanning line weight table.

  The weight table 601 does not necessarily have the configuration shown in FIG. 5B, and it is sufficient that weighting factors can be stored for the total number of transmissions, the total number of received focal points, and the total number of scanning lines. Further, when the weight data in the weight table 601 is duplicated, the weight table 601 may have only a combination of weight data of the minimum data amount from which the duplicated amount is removed.

  For the weighting factor in the weighting table, an optimal value is calculated in advance for each settable imaging condition so that variation due to the delay phasing data system and block noise during high-speed imaging are reduced. It is stored in the weight memory 112 in the unit 111. The control unit 111 reads a table corresponding to the imaging conditions set on the console 110 by the operator from the weight memory 112 and stores the table in the weight table 601.

  Next, the operation flow of the ultrasonic imaging apparatus of the present invention will be described with reference to FIG.

  First, when an operator (operator / examiner) of the apparatus inputs imaging conditions to the console 110, the control unit 111 indicates a control signal indicating information on probe conditions, ultrasonic irradiation conditions, and aperture synthesis conditions in accordance with the imaging conditions. Is output. The reception beamformer 108 receives the control signal (step S401).

  Next, the control unit 111 selects a weighting coefficient table corresponding to the above imaging condition, and downloads it to the weighting table 601 in the reception beamformer 108 (step S402).

  Next, transmission / reception of ultrasonic waves is performed in the ultrasonic element array 101 (step S403). The reception data received by the ultrasonic element 105 in one transmission is transmitted to the delay addition phasing unit 204, and the calculation of the delay phasing data of the reception focal points of a plurality of reception beams as described with reference to FIG. Done. The obtained delay phasing data of the reception focal points of the plurality of reception beams is stored in the beam memory 206 (step S404).

  The processes of steps S403 to S404 are repeated for each set of transmission and reception of ultrasonic waves.

  Next, the delay phasing data between a plurality of transmissions stored in the beam memory and the weight data in the weight table are sent to the inter-transmission combining unit 205 (steps S405 and S406).

  As described with reference to FIG. 4, the inter-transmission synthesizing unit 205 obtains the delayed phasing data R (j, s) after the synthesis of the s-th reception focus of the scanning line number j of the aperture synthetic image as the transmission number. The data r (j, s, n) at the same position as the reception focus (scanning line number j, reception focus number s) of the aperture composite image, which is the delay phasing data obtained at n, is transmitted number n. After weighting by the weighting factor w (j, s, n) of the scanning line number j and the reception focal point number s, the weighted delay phasing data similarly calculated with other transmission numbers is added and synthesized (step) S407).

  The three steps S405, S406, and S407 related to the inter-transmission synthesis are repeated for all (J × S) reception focal points of one frame of the aperture synthetic image.

  The aperture synthesis image synthesized by the inter-transmission synthesis unit 205 is stored in the frame memory 207 in the reception beamformer 108 (step S408). With the above process, the processing by the reception beamformer 108 is completed.

  The frame data stored in the frame memory 207 is transmitted to the image processing unit 109. The image processing unit 109 performs back-end image processing, generates an ultrasonic image (for example, a B-mode image), and outputs it to the image display unit 103 (step S409). In addition, the image processing unit 109 uses the frame data sent from the frame memory 207 to perform nonlinear imaging images, contrast contrast images, continuous wave Doppler images, pulse Doppler images, color flow images, elastic wave images such as elastography, etc. Various ultrasonic images can be generated and applications can be executed.

  In FIG. 6, the weight values are downloaded from the control unit before the transmission / reception of all the ultrasonic waves. However, the operation in step S <b> 402 may be performed immediately before step S <b> 406. Alternatively, it may be performed every time the combining process between transmissions is performed. In that case, the block of step S402 is arranged between the blocks of steps S404 and S406 in FIG. 6, and the operations of steps S402 → S406 → S407 → S402 are repeated until one frame is completed. In this case, the capacity of the weight data transferred to the weight table by one download process can be limited to a capacity necessary for the inter-transmission combining process in step S407.

  According to the present embodiment, as shown in FIG. 7A, the delay phasing data in which the signal intensity varies depending on the number of transmissions due to errors caused by the system and block noise during high-speed imaging is suppressed. Is multiplied by a predetermined weighting factor (FIG. 7B) to reduce the variation between transmissions (FIG. 7C). Therefore, by adding the delay phasing data after being multiplied by the weighting factor, it is possible to obtain a synthesis result in which errors caused by the system and block noise during high-speed imaging are reduced.

  8A shows the overlap of transmission beams in the case of low-speed imaging with spread transmission, and FIG. 8B shows the overlap of transmission beams in the case of high-speed imaging with spread transmission. FIG. 8C shows the overlap of transmission beams in the case of low-speed imaging with low F value focus transmission (focusing transmission), and FIG. 8D shows the transmission in the case of high-speed imaging with low F value focus transmission. The beam overlap is shown. In the case of the high-speed imaging shown in FIGS. 8B and 8D, the overlapping of transmission beams is smaller than that in the case of low-speed imaging, and blocking artifacts are likely to be generated. In particular, in the case of high-speed imaging with focus transmission in FIG. 8D, there is little overlap between transmission beams near the focal point, and it appears as a remarkable blocking artifact. Even in the case of high-speed imaging as shown in FIGS. 8B and 8D, according to the present embodiment, the delay phasing data can be multiplied by a weighting factor to reduce variation between transmissions. Blocking artifacts can be reduced.

  Further, since the aperture synthesis processing of this embodiment is transmitted while shifting the positions of the active channels 201, 202, and 203 little by little as in the general aperture synthesis processing, as shown in FIG. The reception focal points 21, 22,... 23 at the same position as the s-th reception focal point 24 of the scanning line number j are different positions (different prospective angles, different reception beam numbers) of the image of the fan-shaped region 15 obtained by each transmission. Exists. By synthesizing these data, it is possible to superimpose the delay phasing data transmitted / received while expecting the reception focal point 24 from different directions, so that the accuracy of the delay phasing data of the reception focal point 24 can be improved. .

(Comparative Example 1)
As a comparative example, FIG. 5C shows a weight table in the case where weighting is not performed between transmissions as in the prior art, but weighting is performed in the channel direction (arrangement direction of ultrasonic elements) and the depth direction. Since the weight table in FIG. 5C only needs to be a combination of the channel direction and the depth direction, only one two-dimensional memory space (table) is required.

  Therefore, in the weight table of the comparative example, even if there is a variation in the signal strength of the delayed phasing data for each transmission as shown in FIG. 7A, this cannot be corrected, resulting in the system. It is not possible to obtain a synthesis result in which errors and block noise during high-speed imaging are reduced.

(Second Embodiment)
The ultrasonic imaging apparatus according to the second embodiment will be described with reference to FIGS.

  FIG. 9 is a partial block diagram of the ultrasonic imaging apparatus according to the second embodiment, and FIG. 10 is a perspective view of the entire apparatus. The ultrasonic imaging apparatus according to the second embodiment has an input / output port 701 in the main body 102 for accepting rewriting from outside the weighting coefficient of the weight memory 112 or the weight table 601. On the outside of the main body 102, a weighting factor calculation unit 702 for calculating a weighting factor by calculation is arranged. The weighting factor calculation unit 702 is connected to the weighting memory 112 or the weighting table 601 via the input / output port 701, and rewrites the weighting factor stored in the weighting memory 112 or the weighting table 601 with the weighting factor obtained by the calculation.

  The weighting factor calculation unit 702 can receive the delay phasing data for each transmission from the beam memory 206 and calculate the weighting factor. For example, the weighting factor calculation unit 702 is configured to include an adaptive engine 208 that obtains an adaptive weight as a weighting factor by performing adaptive processing on delay phasing data for each transmission. In addition to the adaptive engine 208, a control unit 703 is disposed in the weighting coefficient calculation unit 702. The control unit 703 controls the operation of the adaptive engine 208 and the exchange of signals with the delay phasing data and the weighting factor main body 102 via the input / output port 701.

  FIG. 11 shows an operation flow of the ultrasonic imaging apparatus of the present embodiment. In the operation flow of FIG. 11, steps S505, S506, and S507 are performed instead of steps S406 and S407 of FIG. 6 of the first embodiment. The other steps are the same as those described with reference to FIG. 6, and the description thereof will be omitted. Steps S505, S506, and S507 will be described. If the delay phasing data is stored in the beam memory 206, the adaptive engine 208 receives the delay phasing data under the control of the control unit 111 and the control unit 703 (step S505). The adaptation engine 208 uses the delay phasing data in the beam memory 206 to obtain the optimum adaptation weight corresponding to the variation between transmissions of the delay phasing data, and rewrites this adaptation weight with the weight coefficient in the weight table 601 (step S506). The inter-transmission synthesizing unit 205 reads the delay phasing data and the adaptive weight, weights the delay phasing data with the adaptive weight, and synthesizes between the transmissions (step S507).

  Thereby, the dispersion | variation between transmission of delay phasing data can be reduced more effectively using the weighting coefficient according to delay phasing data. Therefore, it is possible to generate a high-resolution ultrasonic image in which errors caused by the system and block noise during high-speed imaging are reduced.

  In addition, by storing the obtained adaptive weight in the weight memory 112 in correspondence with the imaging conditions at that time, the weight memory can be used in accordance with the difference in delay phasing data for each apparatus and the change over time of the apparatus. The weighting coefficient in 112 can be updated to an optimum value. At the time of updating, it is also possible to display on the image display unit 108 that the weighting factor calculation unit 702 is updating the weighting factor, the adjustment state, the progress of adjustment, and the like. It is also possible to display this display on an indicator 802 attached to the weighting factor calculation unit 702.

  The weighting factor calculation unit 702 according to the present embodiment is arranged outside the main body 102, and only needs to be connected to the main body 102 to rewrite the weighting coefficient in the weight table 601 and update the weight memory 112. Therefore, the ultrasonic diagnostic imaging apparatus can be downsized as compared with the case where the weighting coefficient calculation unit 702 is arranged in the main body 102. In addition, there is also an advantage that a single weighting factor calculation unit 702 can be reused by a plurality of ultrasonic image diagnostic apparatuses. This also makes it possible to perform a refresh operation by changing the weighting coefficient as part of the regular maintenance work of the apparatus when the apparatus characteristics change due to aging degradation of the probe, malfunction of the analog transmission / reception circuit, or the like.

  Next, the calculation method of adaptive weight calculation (step S506 in FIG. 11) in the adaptive engine 208 will be described. The procedure for obtaining the adaptive weight for the sth reception focus of the jth scanning line will be described below.

  The input to the adaptive engine 208 is delay phasing data r (j, s, 1), r (j, s, 2),..., R (j, s, N) obtained by N transmissions. The outputs from the adaptive engine 208 are weighting factors w (j, s, 1), w (j, s, 2),..., W (j, s, N). Hereinafter, for simplicity of explanation, the notation of j is omitted, and the input delay phasing data r (j, s, 1), r (j, s, 2), ..., r (j, s, N ) As a vector r (s) = [r1 (s), r2 (s),..., RN (s)], and weight coefficients w (j, s, 1), w (j, s, 2),. Let w (j, s, N) be the vector w (s) = [r1 (s), r2 (s),..., rN (s)].

  The adaptation engine 208 creates a covariance matrix Γ (s) from the input vector r using the following equation (2). In the formula (2), * represents a conjugate complex number.

  It is also possible to input the vector r with a time width of 2T + 1 points of −T ≦ s ≦ T in the time sample direction. In this case, by taking an ensemble average, the covariance matrix Γ (s) Can be represented by the following formula (3).

  Using these covariance matrices, for example, the adaptive weight vector w (s) by the MVDR method can be calculated from the following equation (4).

  In Expression (4), a is a steering vector, which is an inclination with respect to the direction of the input vector r (s), and is expressed as Expression (5) from the phase relationship of each transmission number n.

  In Expression (5), θ represents the phase shift amount when θ = 0 when the phase around the transmission numbers is zero, and f is the ultrasonic frequency. In general, when θ = 0, a = [1,1,..., 1] and all elements can be expressed by a vector of 1, and this vector is a steering vector direction.

  In the adaptive engine 208, the weight vector w (s) = [r1 (s), r2 (s),..., RN (s)] corresponding to the transmission numbers 1 to N can be calculated from the above process. (S506).

  Note that the adaptive weight calculation method is not limited to the MVDR method, and w (s) may be calculated using various weight generation processes such as the APES method, the MUSIC method, and the ESMV method.

  Also, using the adaptive weight calculation method described here, the weighting coefficient stored in the weight memory 112 of the first embodiment can be calculated for each ultrasound imaging condition.

(Third embodiment)
The ultrasonic imaging apparatus according to the third embodiment will be described with reference to FIGS. FIG. 12 is a block diagram illustrating a partial configuration of the ultrasonic imaging apparatus according to the third embodiment, and FIG. 13 is a perspective view of the apparatus and a diagram illustrating connection to a communication line.

  As shown in FIG. 12, the ultrasonic imaging apparatus of the third embodiment has a configuration similar to that of the apparatus of FIG. 9 of the second embodiment, but instead of the input / output port 701 of FIG. A communication port 901 having a data conversion function for converting data is arranged in the main body 102. In addition, a communication port 903 having a data conversion function is also arranged in the weighting factor calculation unit 702.

  As a result, even if the weighting factor calculation unit 702 is disposed at a location away from the main body 102, the control signal, the delay phasing data, and the weighting factor data are exchanged by connecting the two via the communication line 902 or the network. Therefore, the updating operation of the weighting coefficient can be performed as in the second embodiment. Therefore, it is possible to perform the operation of updating the weighting coefficient stored in the weight memory 112 by remote control as part of periodic device maintenance by remote operation.

(Fourth embodiment)
An ultrasonic imaging apparatus according to the fourth embodiment will be described with reference to FIGS. 14 and 15. FIG. 14 is a block diagram showing a partial configuration of the ultrasonic imaging apparatus according to the fourth embodiment, and FIG. 15 shows an operation flow of the apparatus.

  The ultrasonic imaging apparatus according to the fourth embodiment includes a weighting coefficient calculation unit 702 that calculates a weighting coefficient using delay phasing data for each transmission instead of the weight table of the apparatus of FIG. 1 according to the first embodiment. It is provided inside the reception beamformer 108. The weighting factor calculation unit 702 includes an adaptive engine 208 that obtains an adaptive weight as a weighting factor by performing adaptive processing on the delay phasing data for each transmission. Further, the weight memory 112 is not arranged in the control unit 111.

  The operation of the weighting factor calculation unit 702 including the adaptive engine 208 is the same as that of the weighting factor calculation unit 702 of the second embodiment.

  The operation of the ultrasonic imaging apparatus will be described with reference to FIG. As can be seen from FIG. 15, the operation flow of the apparatus is similar to the operation flow of FIG. 11 of the third embodiment, but since the weight memory 112 and the weight table 601 are not provided, step S402 is not performed and the weight coefficient The calculation unit 702 receives delay phasing data directly from the beam memory 206. In addition, the adaptive weight obtained by the adaptive engine 208 in steps S505 and S506 is directly transferred to the inter-transmission combining unit 205. The inter-transmission synthesizing unit 205 weights the delayed phasing data with the adaptive weight, and synthesizes between the transmissions (step S507).

  Accordingly, the adaptive engine 208 can obtain the adaptive weight by calculation from the delay phasing data stored in the beam memory 206 every time the aperture synthesis process is performed. The inter-transmission synthesizer can weight and synthesize delayed phasing data using adaptive weights, and therefore can effectively reduce errors caused by the system and block noise during high-speed imaging. Therefore, a high-resolution ultrasonic image can be obtained.

(Fifth embodiment)
An ultrasonic imaging apparatus according to the fifth embodiment will be described with reference to FIG.

  The ultrasonic imaging apparatus of the fifth embodiment has the same configuration as that of the apparatus of FIG. 14 of the fourth embodiment, but as shown in FIG. 16, a degeneration unit 501 that degenerates delay phasing data for each transmission. Have The weighting factor calculation unit 702 calculates a weighting factor using the delay phasing data reduced by the reduction unit 501. Thereby, the calculation amount of the adaptive engine 208 of the weight coefficient calculation unit 702 is reduced.

  For example, the degeneration unit 501 degenerates the delay phasing data of N transmissions from the beam memory 206 from N to M. For example, the delay phasing data of 16 transmissions is reduced to data equivalent to the delay phasing data of 4 transmissions. Thereby, the calculation time of the inverse matrix calculation in the adaptive engine 208 is increased by (4 ^ 3) = 64 times, and the mounting scale can be significantly reduced. Thereby, the cost of an apparatus can be reduced.

  The operation of the degeneration unit 501 will be further described. Consider a case where the degeneracy unit 501 reduces the delay phased data of the number of transmissions N to a data amount equivalent to the number of transmissions L (N> L).

The degeneration unit 501 first generates a partial vector r ₁ ^ (s) having the number L of elements obtained by cutting out the length L portion of the vector r as shown in the following equation (6).

  Next, when all the partial vectors are averaged, a degenerate transmission vector g (s) can be created as shown in the following equation (7).

Thereby, the degeneration unit 501 inputs the signal vector g (s) having L elements to the inter-transmission combining unit 205 instead of the signal vector r (s) having N elements. In addition, r _l ^ (s) generated by the degeneration unit is input to the adaptive engine 208.

The adaptive engine 208 calculates a covariance matrix Γ ^ (s) (formula (8)) using a partial vector r _l ^ (s) with L elements.

  Γ ^ (s) represented by Expression (8) is a matrix having L × L elements. Using this degenerate covariance matrix Γ ^ (s), adaptive engine 208 obtains weighting coefficient w ^ (s) having an element of L by Equation (9) and outputs it to inter-transmission combining section 205.

  As described above, the inter-transmission synthesizing unit 205 performs inter-transmission synthesizing processing in a form in which the number of elements is degenerated from N to L by using w ^ and g instead of w and r in Expression (1). And the amount of calculation can be reduced to (L ^ 3) / (N ^ 3).

DESCRIPTION OF SYMBOLS 100 Subject 101 Ultrasonic element array 102 Ultrasonic imaging device main body 103 Image display part 104 Transmission beam former 106 Ultrasonic probe 107 Transmission / reception separation circuit (T / R)
108 Reception Beamformer 109 Image Processing Unit 110 Console 111 Control Unit 601 Weight Table

Claims (10)

An ultrasonic element array in which a plurality of ultrasonic elements are arranged along a predetermined direction, a transmission beam former that transmits ultrasonic waves from at least a part of the plurality of ultrasonic elements, and an ultrasonic wave received from a subject A reception beamformer for phasing reception signals output from the plurality of ultrasonic elements, and an image processing unit for generating image data using the phasing output output from the reception beamformer,
The reception beamformer is a beamformer that performs aperture synthesis processing, a delay addition phasing unit that delays and adds the received signal for each transmission for each of one or more reception focal points, and the delay addition. A delay memory for the same reception focus among the beam memory for storing the delay phasing data for each reception focus by the phasing unit for each transmission and the delay phasing data for each transmission stored in the beam memory. An inter-transmission combiner that reads and combines the phase data;
The ultrasonic imaging apparatus characterized in that the inter-transmission synthesizing unit synthesizes after delay-phased data for each transmission of the same reception focus is weighted with a weighting coefficient.   2. The ultrasonic imaging apparatus according to claim 1, further comprising a weight memory storing a predetermined weight coefficient, wherein the inter-transmission synthesizer reads the weight coefficient from the weight memory and uses it for weighting. A characteristic ultrasonic imaging apparatus.   The ultrasonic imaging apparatus according to claim 2, further comprising a port for accepting rewriting of the weighting coefficient.   The ultrasonic imaging apparatus according to claim 3, further comprising a weighting factor calculation unit that calculates the weighting factor by calculation, wherein the weighting factor calculation unit is connected to the weighting memory via the port, An ultrasonic imaging apparatus, wherein the weighting factor stored in the data is rewritten to a weighting factor obtained by calculation.   5. The ultrasonic imaging apparatus according to claim 4, wherein the weighting factor calculation unit calculates the weighting factor using the delayed phasing data for each transmission. 6.   6. The ultrasonic imaging apparatus according to claim 5, wherein the weighting factor calculation unit calculates the weighting factor using the delayed phasing data for each transmission.   The ultrasound imaging apparatus according to claim 6, wherein the weighting factor calculation unit obtains an adaptive weight as the weighting factor by performing adaptive processing on the delayed phasing data for each transmission. apparatus.   The ultrasonic imaging apparatus according to claim 1, further comprising a weighting factor calculation unit that calculates the weighting factor using the delayed phasing data for each transmission.   9. The ultrasonic imaging apparatus according to claim 8, wherein the weighting factor calculation unit obtains an adaptive weight as the weighting factor by adaptively processing the delayed phasing data for each transmission. apparatus.   10. The ultrasonic imaging apparatus according to claim 8, further comprising: a degeneration unit that degenerates the delay phasing data for each transmission, wherein the weighting factor calculation unit degenerates the delay phasing data degenerated by the degeneration unit. An ultrasonic imaging apparatus, wherein the weighting factor is calculated using

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