Ultrasonic imaging device and signal processing method

Abstract

The present application provides an ultrasonic imaging device and a signal processing method, which suppresses circuit size and efficiently performs a phase modulation addition operation on a received signal generated by an ultrasonic wave that is complexly propagated in a depth direction of an object, to generate an image with higher resolution. The received signals output from a plurality of ultrasonic elements are each delayed by a given delay amount corresponding to the depth of a reception focal point, the delayed received signals are branched, a phase-compensated signal is generated by shifting the phase of the branched received signals by a given phase shift amount, and the phase-compensated signal is added to the received signal before branching, thereby generating a phase-modulated signal.

Description

Technical Field

[0001] This invention relates to ultrasonic imaging technology that uses ultrasound to capture images of a subject. Background Technology

[0002] Ultrasonic imaging technology refers to the non-invasive technique of using ultrasound (not the sound waves that are meant to be heard, but generally high-frequency sound waves above 20kHz) to image the interior of a subject, primarily the human body.

[0003] Ultrasonic imaging devices transmit and receive ultrasonic waves using an array of ultrasonic elements with a finite aperture diameter. Therefore, they are susceptible to diffraction caused by the edges of the aperture, making it difficult to improve azimuth resolution. Consequently, novel phase modulation methods such as adaptive beamforming and aperture synthesis have been proposed.

[0004] Patent Document 1 discloses a technique for aperture synthesis using a modified virtual sound source method in ultrasonic imaging technology that performs focused transmission. Specifically, in the region where the energy of the ultrasonic beam converges to the focal point (Patent Document 1), Figure 2 In region A), the focus is treated as a virtual sound source and open-aperture synthesis is performed. In regions B and C, the ultrasonic energy around it is treated as radiating spherical waves from the end of the probe and open-aperture synthesis is performed.

[0005] On the other hand, Patent Document 2 discloses an ultrasonic imaging device comprising two or more delay-adding units that perform delay-addition on received signals using two or more delay times. The first delay-adding unit performs delay-addition based on a first delay time for phase-modulating the received signal generated from a transmitted beam (interference wave) transmitted from an ultrasonic element. The second delay-adding unit performs delay-addition on the received signal based on a second delay time for phase-modulating the received signal generated from a diffracted wave (spherical wave) with a phase different from the transmitted beam. The first and second delay-adding units respectively synthesize the delayed-addition signals.

[0006] Prior art literature

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 10-277042

[0009] Patent Document 2: International Publication No. 2016 / 125509 Summary of the Invention

[0010] -The problem the invention aims to solve-

[0011] The technology in Patent Document 1 is a technique for performing aperture synthesis during transmission, which cannot obtain a high-precision image with only one transmission.

[0012] In the technology of Patent Document 2, since the received signal is delayed by two or more delay times before addition is performed, more than two delay circuits are required for an ultrasonic element, thus increasing the circuit size.

[0013] The purpose of the invention is to reduce circuit size and efficiently perform phase modulation addition on the received signal generated by ultrasound waves that propagate complexly in the depth direction of the subject to generate a higher resolution image.

[0014] -Methods used to solve problems-

[0015] The ultrasonic imaging apparatus of the present invention comprises: a transmitting beamformer that transmits ultrasonic waves, phase-delayed in a manner focused on a given transmitting focal point, from a plurality of ultrasonic elements of a connected ultrasonic element array to a subject; and a receiving beamformer that receives received signals output by the plurality of ultrasonic elements of the ultrasonic element array from ultrasonic waves returned to the ultrasonic element array from the subject that received the transmitted ultrasonic waves, and generates phase-modulated signals by performing receiving beamforming according to each receiving focal point set within the subject. The receiving beamformer includes a delay circuit for delaying the received signals, an adder circuit, and a phase compensation circuit. The delay circuit delays the received signals output by the plurality of ultrasonic elements by a given delay amount corresponding to the depth of the receiving focal point. The adder circuit adds the received signals delayed by the delay circuit to generate phase-modulated signals. The phase compensation circuit generates a phase-compensated signal after the delay circuit has delayed the received signals, or a phase-modulated signal has been branched and its phase shifted by a given phase shift amount, and adds it to the received signal or phase-modulated signal before the branching.

[0016] -Invention Effects-

[0017] According to the present invention, not only can the circuit size be suppressed, but also an apparatus can be provided to perform phase modulation addition on the received signals generated by spherical waves that are transmitted separately from multiple ultrasonic elements and propagate in a complex direction in the depth direction of the subject, in addition to the transmitted beam, to generate a higher resolution image. Attached Figure Description

[0018] Figure 1 This is a block diagram showing the structure of the ultrasonic camera device according to the first embodiment.

[0019] Figure 2 (a) is a block diagram showing the structure of the receiving beamformer of the first embodiment, and (b) is a block diagram of the receiving beamformer of the comparative example.

[0020] Figure 3 This is an explanatory diagram showing the shape of the transmitted beam 310 and the wavefront and spherical wave.

[0021] Figure 4 It means Figure 1 A block diagram of the phase compensation circuit.

[0022] Figure 5 This is a graph showing an example of a delay curve representing the delay time relative to the depth of the first embodiment.

[0023] Figure 6 This is a flowchart illustrating the operation of each part of the ultrasonic camera device in the first embodiment during photography.

[0024] Figure 7 This is a block diagram showing the structure of the receiving beamformer in the second embodiment.

[0025] Figure 8 This is a graph showing an example of a delay curve representing the delay time relative to the depth of the second embodiment.

[0026] Figure 9 This is a block diagram showing the structure of the receiving beamformer in the third embodiment.

[0027] Figure 10 This is a block diagram showing the structure of the receiving beamformer according to the fourth embodiment.

[0028] Figure 11 This is a graph showing an example of a delay curve representing the delay time relative to the depth of the fifth embodiment.

[0029] Figure 12 This is a graph showing an example of a delay curve representing the delay time relative to the depth of the fifth embodiment.

[0030] Figure 13 This is a graph showing an example of a delay curve representing the delay time relative to the depth of the fifth embodiment.

[0031] Figure 14 (a) is an image of an ideal point image. Figure 14 (b) is the ultrasound image of the comparative example. Figure 14 (c) to (e) are ultrasonic images captured by the ultrasonic imaging device of the first embodiment.

[0032] -Symbol Explanation-

[0033] S1 receives signal

[0034] S100 receives signals

[0035] S2 receives signal

[0036] S3 receives signal

[0037] S4 phase modulation signal

[0038] S5 phase modulation signal

[0039] S6 receives signals

[0040] S7 phase modulation signal

[0041] S10 phase modulation signal

[0042] S11 Phase modulation signal

[0043] S12 phase modulation signal

[0044] 10 Transceiver Separation Circuit

[0045] 11 Control Department

[0046] 12 Console

[0047] 13 Receiver Beamformer

[0048] 14. Transmit Beamformer

[0049] 15. Image Processing Department

[0050] 15a Sending Opening Combination Section

[0051] 16 Image Display Unit

[0052] 17. Phase Compensation Circuit Control Unit

[0053] 18. Phase displacement storage unit

[0054] 19. Delay Time Preservation Department

[0055] 20. Receive Focus

[0056] 21 Delay Circuit

[0057] 21a Memory

[0058] 21b Interpolation Circuit

[0059] 22 Phase Compensation Circuit

[0060] 23 Adder Circuit

[0061] 25 Switches

[0062] 30 Send Focus

[0063] 36 receiving scan lines

[0064] Shift registers 41a and 41b

[0065] 42a, 42b interpolators

[0066] 90 subjects

[0067] 100 Ultrasonic Camera Device

[0068] 101 Ultrasonic Element Array

[0069] 102 Main body of ultrasonic camera device

[0070] 105 Transmit Channel

[0071] 106 Receive Channel

[0072] 116 Ultrasonic probe

[0073] 121 Delay Circuit

[0074] 123 Adder Circuit

[0075] 201 Converter

[0076] 222 Phase Compensation Circuit

[0077] 223 Adder Circuit

[0078] 224 filter

[0079] 225 Filter Coefficient Conversion Section

[0080] 301 Spherical Wave

[0081] 310 Transmit Beam

[0082] 350 delay time

[0083] 351 Delay Time

[0084] 371 Depth Range

[0085] 372 Depth range. Detailed Implementation

[0086] An ultrasonic imaging device according to one embodiment of the present invention will be described.

[0087] <<<First Implementation Method>>>

[0088] First, use Figures 1-6 The ultrasonic camera device 100 of the first embodiment will be described. Figure 1 This is a diagram showing the structure of an ultrasound diagnostic device. Figure 2 This is a diagram showing the structure of the receiving beamformer.

[0089] like Figure 1As shown, the ultrasonic imaging device 100 of this embodiment includes an ultrasonic imaging device main body 102 and an ultrasonic probe 116 having an ultrasonic element array 101 connected to the ultrasonic imaging device main body 102. The ultrasonic element array 101 is a structure in which multiple ultrasonic elements are arranged in an array. In the ultrasonic element array 101, the multiple ultrasonic elements (channels) used for transmission are also referred to as transmission channels, and the multiple ultrasonic channels used for reception are also referred to as reception channels.

[0090] use Figure 1 as well as Figure 2 The main components of the ultrasonic camera device body 102 will be described below. The ultrasonic camera device body 102 includes a transmitting beamformer 14, a receiving beamformer 13, a phase compensation circuit control unit 17, a phase shift storage unit 18, a transmit / receive separation circuit 10, an AD converter 201, an image processing unit 15, a control unit 11, an image display unit 16, and a control console 12.

[0091] In this embodiment, the receiving beamformer 13 includes a delay circuit 21, a phase compensation circuit 22, and an adder circuit 23.

[0092] The received signals s1, output from multiple ultrasonic elements (receiving channels 106), are converted into digital signals by the AD converter 201. The delay circuit 21 of the receiving beamformer 13 delays the converted received signals s1 according to a predetermined delay time for each receiving channel 106, based on the depth of the receiving focus 20. Specifically, the received signals s1 are used to generate multiple delayed received signals s2 by implementing a coarse (low) time resolution delay process controlled by the readout timing from the memory 21a, and a high time resolution delay process implemented by interpolation processing performed by the interpolation circuit 21b. For example, the time resolution delay process at the readout timing from the memory 21a is greater than the wavelength of the sound wave, and the interpolation processing performed by the interpolation circuit 21b is used to perform a high resolution delay process several times smaller than the wavelength of the sound wave.

[0093] Phase compensation circuit 22 branches one or more received signals s100 from the memory 21a in delay circuit 21 after they have just been read out, and sets a phase shift of the branched received signals s100 by a given amount, thereby generating a phase-compensated received signal s3. The phase shift amount is read from the phase shift amount storage unit 18, which stores the phase shift amount at each depth of the receiving focus 20, according to a readout instruction from phase compensation circuit control unit 17, and set in phase compensation circuit 22. Figure 2In the example, the phase compensation circuit 22 causes the entire received signal s100, which is read from the memory 21a in the delay circuit 21 and delayed with a coarse time resolution, to be branched and phase-shifted to generate the phase-compensated received signal s3.

[0094] The adder circuit 23 adds the multiple received signals s2 delayed by the delay circuit 21 and the more than one phase-compensated received signal s3 generated by the phase compensation circuit 22 to generate a phase-modulated signal s4.

[0095] Thus, in this embodiment, by shifting the phase of the received signal s100 immediately after being read from the memory 21a in the delay circuit 21, the delay circuit 21 and the phase compensation circuit 22 can generate received signals s2 and s3 that are substantially the same as those delayed by various delay times. The phase compensation circuit 22 omits the read-out process from the memory 21a, thus saving not only the corresponding memory but also eliminating the need for physical processing lines for signal processing in the circuit. Therefore, compared to the number of multiple delay processes required, the entire structure of the delay circuit 21 can be implemented with a simpler circuit structure. Therefore, it is possible to suppress the circuit size and achieve substantially the same effect as in the case of using multiple delay times to perform phase modulation addition on the received signal generated by ultrasound waves propagating complexly in the depth direction of the subject 90, thereby generating a high-resolution image.

[0096] The ultrasonic camera device 100 of this embodiment will now be described in detail.

[0097] The transmit beamformer 14 outputs transmit signals to the multiple ultrasonic elements (transmit channel 105) of the connected ultrasonic element array 101. The transmit channel 105 converts the transmit signals into ultrasonic waves and sends them to the subject 90.

[0098] At this time, the transmit beamformer 14 delays the phase of the transmitted signal by a given amount, so that the ultrasonic waves (spherical waves) 301-306 transmitted from each transmit channel 105 interfere with each other and... Figure 3 As shown, the beam is focused at a given depth of transmission focal point 30. Thus, a transmission beam (interference wave) 310 focused at the desired depth of transmission focal point 30 can be projected onto the subject 90. Furthermore, as... Figure 3 As shown, in addition to forming the aforementioned transmission beam (interference wave) 310, the ultrasonic waves (spherical waves) 301-306 transmitted from each transmission channel 105 propagate in all directions, thereby forming interference waves in which only a portion of them interfere, and propagate in a complex manner in the depth direction.

[0099] Within the object 90 through which the transmitting beam (interference wave) 310, ultrasonic waves (spherical waves) 301-306, and other interference waves propagate, these waves are reflected, scattered, etc., and a portion of the reflected and scattered waves re-arrive at the ultrasonic element array 101. The arriving waves are received by the multiple receiving channels 106 of the ultrasonic element array 101 and converted into received signals.

[0100] The AD converter 201 converts the received signal s1 output from the receiving channel 106 into a digital signal.

[0101] like Figure 2 As shown in (a), the delay circuit 21 of the receiving beamformer 13 receives the receiving signal s1 from multiple receiving channels 106 via the transceiver separation circuit 10 and the AD converter 201. According to the delay time indicated by the control unit 11, the receiving signal s1 is delayed according to the depth of the receiving focus 20 set in the subject 90.

[0102] Here, the delay circuit 21 includes a memory 21a and an interpolation circuit 21b configured for each receive channel 106.

[0103] The memory 21a temporarily stores the received signal s1, which is converted into a digital signal.

[0104] Interpolation circuit 21b reads the received signal s100 from memory 21a and performs interpolation processing. At this time, the timing of the received signal s100 read from memory 21a is adjusted using the clock unit of a digital signal to delay the received signal s1 with a delay accuracy of approximately wavelength or more. Next, in interpolation circuit 21b, the read received signal s100 is interpolated, and a fine adjustment is made to the delay time, which is less than a clock unit or several times the wavelength, to achieve a delay of the received signal s1 within the delay time indicated by control unit 11, generating a delayed received signal s2.

[0105] The delay time is predetermined based on the distance between the receiving focus 20 and the receiving channel 106 and is stored in the delay time storage unit 19. The control unit 11 provides a readout instruction for the delay time from the delay time storage unit 19 based on the position of the receiving focus 20 and sets it in the delay circuit 21.

[0106] The received signal s2 is a signal that delays the received signal s1 output by each receiving channel 106 by an amount corresponding to the distance between the receiving focus 20 and the receiving channel 106. Therefore, as Figure 2 The phases shown are consistent.

[0107] like Figure 2As shown, the phase compensation circuit 22 is configured for each interpolation circuit 21b, and branches the received signal s100 that has just been read from the memory 21a in the delay circuit 21, so that its phase is shifted by the phase shift amount indicated by the phase compensation circuit control unit 17, and generates the phase-compensated received signal s3.

[0108] Similar to the delay time stored in the delay time storage unit 19, the phase displacement amount is pre-stored in the phase displacement amount storage unit 18 and is supplied to the phase compensation circuit 22 according to the instruction from the phase compensation circuit control unit.

[0109] use Figure 4 The structures of the interpolation circuit 21b and the phase compensation circuit 22 in the delay circuit 21 will be described in detail. First, the interpolation circuit 21b in the delay circuit 21 is composed of a shift register 41a and an interpolator 42a. The received signal s100 after being read from the memory is delayed with high precision by multiplying the minute time shift of the shift register 41a and the interpolation coefficients of the interpolator 42a. The control unit 11 instructs the interpolation circuit 21b to read the timing from the memory 21a, and, referring to the value of the LUT (lookup table) stored in the delay time storage unit 19, gives the shift register 41a a time shift and the delay time as the interpolation coefficients of the interpolator 42a. As a result, a received signal s2 with a delay is generated.

[0110] The phase compensation circuit 22 has the same structure as the interpolation circuit 21b of the delay circuit 21, consisting of a shift register 41b and an interpolator 42b. The received signal s100, read from the memory 21a, is branched, and a high-precision phase shift, less than a clock cycle or several times the wavelength, is performed by the shift register 41b and interpolator 42b of the phase compensation circuit 22. Here, the phase shift amount implemented by the phase compensation circuit 22 is pre-stored in the phase shift amount storage unit 18 (LUT) according to each depth of the receiving focus. The phase shift amount storage unit 18 sends the phase shift amount to the phase compensation circuit 22 according to the read command from the phase compensation circuit control unit 17. Furthermore, timing and other control signals are sent from the phase compensation circuit control unit 17 to the phase compensation circuit 22. Thus, the phase-compensated received signal s3 is generated by the phase compensation circuit 22.

[0111] The adder circuit 23 generates a phase-modulated signal s4 by adding the delayed received signal s2 of each received channel 106 output by the interpolation circuit 21b of the delay circuit 21 and the received signal s3 of the received signal s2 output by the phase compensation circuit 22 after phase shifting.

[0112] In addition, such as Figure 4As shown, the adder circuit 23 can be in the form of adding the received signal s2 and the received signal s3 separately for each channel, and then performing an addition operation between all channels on the signal of each channel after the addition operation, as shown in the example. Figure 2 As shown, it can also be in the form of simultaneously adding the received signals s2 and s3 of all channels.

[0113] In this way, by adding the delayed received signal s2 and the received signal s3, which has undergone phase shifting of the received signal s2, a phase-modulated signal can be generated not only from the received signal generated by the transmitted beam 310, but also from the received signal generated by waves that propagate directly from spherical waves 301 to 306, or interference waves in which a portion of them has interfered. This will be explained below.

[0114] In the delay time storage unit 19, the delay time used by the receiving beamformer 13 to delay the received signal s1 is stored for each ultrasonic element (receiving channel 106). Since the receiving beamformer 13 sequentially aligns the focal point with a plurality of receiving focal points 20 on the receiving scan line set by the control unit 11, this delay time varies depending on the distance between the receiving focal point 20 and the receiving channel 106, for example... Figure 5 As shown by the dashed curve 350, it varies according to the depth of the receiving focus 20. Here, the variation in delay time at each depth is also referred to as the delay curve.

[0115] In this embodiment, a phase-modulated signal is generated not only based on the received signal generated by the transmit beam 310, but also based on the received signal generated by waves that propagate directly from spherical waves 301 to 306, interference waves in which a portion of them interfere, etc. Therefore, a signal (received signal s2) is generated by the phase shift of the received signal s1, which is the same as the received signal that delays the received signal s1 by a delay time 351 that is different from the delay time 350 used to align the received signal generated by the transmit beam 310 to the receiving focus 20.

[0116] For example, such as Figure 5 As shown, if the delay time (transmit beam delay time) 350 used to align the received signal generated by the transmit beam 310 to the receiving focus 20 is set to the delay time (spherical wave delay time) 351 required to align the received signal of the reflected wave generated by the spherical wave 301 to the receiving focus 20, then in order to obtain the phase-modulated signal s7 by performing addition operations after delaying the received signal s1 according to the spherical wave delay time 351, the following is required: Figure 2Prepare another set of delay circuits 121 and adder circuits 123 as in (b). Then, the received signal s1 from the receiving channel 106 needs to be branched, delayed by a delay time of 351 as a spherical wave by the other set of delay circuits 121, and added by the adder circuits 123 to obtain the received signal s6.

[0117] The inventors discovered that the received signal s6, delayed by a spherical wave delay time of 351, and the received signal s2, delayed by a transmit beam delay time of 350, do not have a large phase difference; their phase difference converges within one wavelength (2π rad). In particular, they found that while the spherical waves transmitted from each channel as a whole have a phase difference of more than one wavelength, when adding the delayed signal based on the transmit beam delay time and the delayed signal based on the spherical wave delay time according to this invention, if the addition operation is performed with a phase difference of more than one wavelength, the resolution degradation caused by the mutual phase deviation becomes dominant, leading to resolution degradation and preventing an effective improvement in image quality. Therefore, the inventors adopted the following structure: using the signal s100 that has just been read from the memory and given a coarse delay time, the phase compensation circuit 22 makes the phase difference displacement of the phase of the received signal s2 delayed by a delay time 350 by a predetermined small phase displacement amount, thereby generating a received signal s3 with the same waveform and phase as the received signal s6 delayed by a delay time 351 different from the received signal s6 delayed by a delay time 351.

[0118] Compared to preparing another set of delay circuits 121 and adder circuits 123, the phase compensation circuit 22 can reduce the size of the memory and the size of the delay processing circuit. Therefore, in the ultrasonic imaging device of this embodiment, the same phase-modulated signal s4 as the case where the received signal s1 is delayed by multiple delay times 350, 351 can be generated while reducing the size of the circuit.

[0119] Specifically, in this embodiment Figure 2 In the structure of (a), such as Figure 4 As shown, shift registers 41a and 41b and interpolators 42a and 42b can be constructed using only two to a finite number of taps (the number of stages in a digital filter). In contrast, in... Figure 2 In the case of preparing multiple delay lines of another set of delay circuits 121 as in the comparative example (b), more than 1000 memory buffer areas are required, corresponding to the total number of samples of one scan line. Therefore, in this embodiment... Figure 2 (a) structure and Figure 2 Compared to the comparative example (b), the circuit can be implemented such that, although the installation scale is very small, the phase modulation signal s4 can be generated.

[0120] In addition, the phase displacement of the phase compensation circuit 22 varies according to the depth direction of the delay time 351, so that the receiving focus 20 can obtain the received signal s3 at each depth.

[0121] Thus, in this embodiment, not only can the received signal generated by the transmit beam 310 be generated, but the phase of the received signal generated by interference waves, such as those generated by interference of any one or a portion of spherical waves 301-306, can also be made consistent, generating received signals s2 and s3. Therefore, the receive beamformer 13 can obtain a phase-modulated signal s4 reflecting information of the received signal s2 generated by the transmit beam 310 and the received signal s3 generated by any one of the spherical waves 301, etc., from the same received signal for the same receive scan line. Therefore, a high-resolution phase-modulated signal can be obtained compared to a phase-modulated signal obtained only for the transmit beam 310.

[0122] The control unit 11 moves the transmission channel 105 and controls each part, repeatedly transmitting and receiving until the phase-modulated signal of the required number of receive scan lines for image generation is obtained. This control method can also be used for linear scanning, convection scanning, or other scanning methods. In the case of sector (phased array) scanning, the transmission and reception apertures are the same, but the following method is adopted: by tilting the receive scan lines 36 in an angular direction, multiple transmission and reception scan lines are set on a two-dimensional plane, and imaging of a sector area is performed along this direction. For example, there is a method of preparing approximately 50-1300 scan lines in a sector shape of ±45° or ±60° centered on the probe aperture. In this case, the control unit 11 controls each part to move the transmission angular direction instead of the transmission channel 105, and repeatedly transmits and receives until the phase-modulated signal of the required number of receive scan lines 36 for image generation is obtained.

[0123] The image processing unit 15 generates an image based on the number of phase modulation signals required for image generation and displays it on the connected image display unit 16. For example, the image processing unit 15 performs signal processing such as digital filtering and interpolation processing on the phase modulation signals after delay addition, as well as conversion processing from RF (Radio Frequency) signals to luminance signals such as detection processing and envelope extraction processing. It also samples the luminance signals generated from multiple phase modulation signals, performs scan conversion (coordinate transformation) processing corresponding to the scanning mode, and performs image processing to convert the signal intensity / luminance value of each pixel, thereby generating an image signal. The image is generated by arranging the image signals.

[0124] Next, use Figure 6The operation of each part of the ultrasonic camera device in this embodiment during recording will be explained.

[0125] (Step 131)

[0126] First, the control unit 11 receives, via the console 12, transmission and reception parameters set based on camera condition parameters and / or camera parameters, and / or the type of the connected ultrasonic probe 116. Transmission and reception parameters include, for example, transmission aperture diameter, reception aperture system, frequency (center frequency, frequency band), transmission focus position, and the shape of the transmission pulse wave (wave number, amplitude), etc.

[0127] (Step 132)

[0128] Based on the conditions received in step 131, the control unit 11 calculates the shape of the transmission beam 310.

[0129] (Step 133)

[0130] The control unit 11 transmits transmission conditions such as the position of the transmission focus 30, transmission frequency, and number of transmissions to the transmission beamformer 14. The transmission beamformer 14 generates a transmission signal and outputs it to the ultrasonic elements of the transmission channel 105 of the ultrasonic element array 101. The ultrasonic elements of the transmission channel 105 convert the transmission signal into ultrasonic waves and transmit them. The receiving channel 106 of the ultrasonic element array 101 receives the sound waves from the subject generated by the transmission in step 135 and outputs a receiving signal s1.

[0131] (Step 134)

[0132] The delay circuit 21 temporarily stores the received signal s1 in the memory 21a. The interpolation circuit 21b reads the received signal s100 from the memory 21a at clock unit intervals and delays it with a coarse time resolution. In the interpolation circuit 21b, the read received signal s100 is interpolated to further delay it with a higher time resolution of less than a clock unit or less than a multiple of the wavelength, and the received signal s2 is output. Thus, under the control of the control unit 11, the delay time storage unit 19 delays the received signal s1 according to the delay time indicated by the interpolation circuit 21b, generating the delayed received signal s2.

[0133] (Step 135)

[0134] Phase compensation circuit 22 branches the received signal s100 that has just been output from memory 21a in delay circuit 21, thereby shifting the phase of the branched received signal s100 to generate a phase-shifted received signal s3. Furthermore, the phase shift amount is a value pre-stored in phase shift amount storage unit 18, and under the control of phase compensation circuit control unit 17, it is a value set from phase shift amount storage unit 18 in phase compensation circuit 22.

[0135] (Step 136)

[0136] The adder circuit 23 adds the delayed received signal s2 from the delay circuit 21 and the phase-shifted received signal s3 from the phase compensation circuit 22 to generate the phase-modulated signal s4.

[0137] (Step 137)

[0138] The image processing unit 15 performs signal processing and image processing on the phase modulation signal s4 of each received scan line to generate an image.

[0139] Thus, in this embodiment, not only can a received signal s3 equivalent to the received signal s2 generated by the transmitted beam 310 be generated through phase shifting, but also a received signal s3 equivalent to the received signal generated by an interference wave, such as one or a portion of the spherical waves 301-306, can be generated through phase shifting. Therefore, a high-resolution image reflecting the information of the received signal s2 generated by the transmitted beam 310 and the information of the received signal s3 generated by any one of the spherical waves 301, etc., can be generated with less computation by using a receiver beamformer 13 that reduces circuit size.

[0140] <Variation 1-1: Multiple Receiver Scan Lines>

[0141] A variation of the ultrasonic camera device of the first embodiment will be described.

[0142] The ultrasonic imaging device of this embodiment is not limited to a structure that obtains a phase-modulated signal by transmitting a single signal to one receiving scan line. It can also generate phase-modulated signals separately for multiple receiving scan lines by transmitting a single signal. As a result, the number of transmissions required to generate one image can be reduced, enabling high-speed imaging.

[0143] <Variation Example 1-2: Sending Opening Synthesis>

[0144] Other variations of the ultrasonic camera device according to the first embodiment will be described.

[0145] The ultrasonic imaging device of this embodiment can also be configured to generate phase-modulated signals for multiple receiving scan lines in a single transmission, and then combine the transmission apertures as needed. In this case, such as Figure 1 As shown, a transmission opening synthesis unit 15a is configured in the image processing unit 15.

[0146] The receiving beamformer 13 generates phase modulation signals s4 for multiple receiving scan lines based on the received signal s1 obtained through one transmission.

[0147] The transmitting aperture combining unit 15a stores the phase modulation signals s4 of multiple receive scan lines obtained in a single transmission in its built-in memory. The transmitting aperture combining unit 15a combines the phase modulation signals s4 of the multiple receive scan lines obtained during transmission with the phase modulation signals s4 of receive scan lines at the same position obtained in a previous transmission, thus obtaining the aperture-combined phase modulation signal. Alternatively, weighted summation can be performed during the addition operation.

[0148] The image processing unit 15 uses the phase-modulated signal after aperture synthesis to generate an image.

[0149] In this way, by performing aperture synthesis, the spatial resolution of the generated image can be improved.

[0150] Furthermore, this embodiment is the upstream processing of the signal processing of an ultrasonic device such as a beamformer 13, so it can be used not only in combination with transmitting aperture synthesis, but also in combination with other ultrasonic imaging methods, such as nonlinear (harmonic) imaging, Doppler imaging, color stream imaging, coherent imaging, and imaging using adaptive beamforming.

[0151] <Variation Example 1-3: Weighted Addition Based on Depth>

[0152] Another variation of the ultrasonic camera device according to the first embodiment will be described.

[0153] The adder circuit 23 of the receiving beamformer 13 can also be configured to perform a weighted addition operation when adding the delayed received signal s2 and the phase-shifted received signal s3. In this case, the control unit 11 can set appropriate weights for obtaining a high-resolution image by varying the weights of the adder circuit 23 according to the depth range. Furthermore, the control unit 11 can also receive weights set by the operator via the control console 12 and can change the weights according to the imaging conditions.

[0154] <<<Second Implementation Method>>>

[0155] use Figure 7 The ultrasonic camera device of the second embodiment will be described. Figure 7 The structure of the receiving beamformer 13 of the ultrasonic camera device in Embodiment 2 is shown.

[0156] like Figure 7 As shown, in order to obtain a phase-modulated signal reflecting the received signal from a plurality of spherical waves 301 to 306 and interference waves of a portion thereof, the receiving beamformer 13 of embodiment 2 branches and connects a plurality of phase compensation circuits 22-1, 22-2, and 22-3 from the memory 21a in the delay circuit 21.

[0157] Multiple phase compensation circuits 22-1, 22-2, and 22-3 branch the received signal s100 output from memory 21a into multiple branches, each with a different phase shift amount, generating phase-shifted received signals s3-1, s3-2, and s3-3. Adder circuit 23 adds the received signal s2 output from interpolation circuit 21b to the phase-shifted received signals s3-1, s3-2, and s3-3 to generate a phase-modulated signal s4.

[0158] For example, such as Figure 8 As shown, the phase displacement of phase compensation circuits 22-1, 22-2, and 22-3 is set by phase compensation circuit control unit 17 to generate a phase displacement with a delay equivalent to the delay of the received signal generated in the receiving channel 106 based on three waves, a subset of the interference waves of multiple spherical waves 301 to 306, for the purpose of delaying the delay time 351, 352, and 353 for aligning the focus with the receiving focus 20.

[0159] Therefore, not only can the transmitting beam 310 be obtained, but also the phase-modulated signal s4, which reflects the received signal generated by the interference wave of multiple spherical waves 301 to 306 and a portion thereof, can be obtained.

[0160] Furthermore, in this embodiment, since the circuit size of a single phase compensation circuit 22 is small, even when multiple phase compensation circuits 22-1, 22-2, and 22-3 are configured, the overall circuit size can be suppressed compared to the case where multiple delay circuits 121 are configured.

[0161] Other structures, actions, and effects are the same as in the first embodiment, so descriptions are omitted.

[0162] <Variation Example 2-1: Weighted Addition>

[0163] A variation of the ultrasonic camera device of the second embodiment will be described.

[0164] The adder circuit 23 of the receiving beamformer 13 can be configured to perform a weighted addition operation when adding the received signal s2 of the delay circuit 21 and the received signals s3-1, s3-2, s3-3 after phase shifting of the multiple phase compensation circuits 22-1, 22-2, 22-3.

[0165] The control unit 11 can be configured to set appropriate weights for obtaining a high-resolution image by changing the weights of the addition circuit 23 according to the depth range.

[0166] The control unit 11 can also receive weights set by the operator via the console 12, and can also change the weights according to the camera conditions.

[0167] <Variation Example 2-2: Phase Shift Processing Based on Time Series>

[0168] Other variations of the ultrasonic camera device according to the second embodiment will be described.

[0169] The receiving beamformer 13 can also replace the phase compensation circuits 22-1, 22-2, and 22-3 by generating phase-shifted received signals s3-1, s3-2, and s3-3 through a phase compensation circuit 22 and a memory. Specifically, the phase compensation circuit 22 performs phase shifting on the received signal s100 of the delay circuit 21 to generate the phase-shifted received signal s3-1, which is then stored in the memory. The received signal s2 is then phase-shifted again to generate the phase-shifted received signal s3-2, and this process of storing the phase-shifted received signals s3-1, s3-2, and s3-3 is repeated to generate and store these signals in the memory. Additionally, the received signal s2 without phase shifting is stored in the memory. The adder circuit 23 reads the received signal s2 and the phase-shifted received signals s3-1, s3-2, and s3-3 from the memory and performs an addition operation.

[0170] In this structure, only one phase compensation circuit 22 is required, thus the circuit size can be relatively small. Therefore, a receiving beamformer 13 can also be installed inside the ultrasonic probe 116.

[0171] Furthermore, the ultrasonic imaging device of the second embodiment can also, in the same manner as the ultrasonic imaging device of the first embodiment (variations 1-1, 1-2, 1-3), generate multiple receiving scan lines for a single transmission and perform high-speed imaging, perform transmission aperture synthesis, and perform weighted addition operations based on depth.

[0172] <<<Third Implementation Method>>>

[0173] use Figure 9 The ultrasonic camera device of the third embodiment will be described.

[0174] like Figure 9 As shown, the ultrasonic imaging device of Embodiment 3 has a structure in which a phase compensation circuit 222 and an adder circuit 223 are arranged after the adder circuit 23. Additionally, a memory for storing the phase-modulated signal is typically prepared after the adder circuit 23. Alternatively, the output signal can be processed continuously in a time sequence without a memory.

[0175] Phase compensation circuit 222 branches the phase modulation signal s5 output from adder circuit 23 of receiving beamformer, causing phase shift and generating phase-shifted phase modulation signal s10. Furthermore, adder circuit 223 adds the phase modulation signal s5 output from adder circuit 23 and the phase-shifted phase modulation signal s10 output from phase compensation circuit 222 to generate phase modulation signal s11.

[0176] The phase compensation circuit control unit 17 sets the phase displacement in the phase compensation circuit 222.

[0177] The image processing unit 15 uses the phase modulation signal s11 after addition to generate an image.

[0178] Other structures, actions, and effects are the same as in the first embodiment, so descriptions are omitted.

[0179] As in the third embodiment, by assigning a phase signal to the signal after a single phase-modulation addition operation, the installation scale can be significantly reduced compared to the first embodiment. In the first embodiment, a phase compensation circuit 22 of a corresponding number of channels is required, but in the second embodiment, only one phase compensation circuit 222 is needed. For example, in the case of 128 channels, the installation scale is reduced by approximately 1% or less compared to the first embodiment. Furthermore, in the first embodiment, rounding errors caused by interpolation processing in multiple channels may reduce the final image quality improvement, but in the third embodiment, since the phase shift is performed by at most one phase compensation circuit 222, the impact of rounding errors can be minimized. On the other hand, compared to the first embodiment, the amount of phase shift cannot be varied for each channel, thus reducing the design and adjustment freedom.

[0180] Alternatively, in the third embodiment, the following structure can also be adopted: the phase compensation circuit 222 is as described in the second embodiment. Figure 7 In this way, multiple phase-modulated signals with different phase displacements are configured in parallel, and the adder circuit 223 performs addition operations on them.

[0181] Furthermore, the ultrasonic imaging device of the third embodiment can also perform high-speed imaging, generate multiple receiving scan lines for a single transmission, perform transmission aperture synthesis, and perform weighted addition by the addition circuit 223 according to the depth, similar to the ultrasonic imaging device of the first embodiment's variations 1-1, 1-2, and 1-3.

[0182] <<<Fourth Implementation Method>>>

[0183] use Figure 10 The ultrasonic camera device of the fourth embodiment will be described.

[0184] In this embodiment, such as Figure 10 As shown, by using the digital filter 224 configured in the subsequent stage of the adder circuit 23, the waveform of the phase modulation signal s5 output by the adder circuit 23 is adjusted to generate a phase modulation signal s12 with the same waveform as the phase modulation signal s11 output by the ultrasonic imaging device of the third embodiment. The digital filter 224 is configured to include at least one adder, a multiplier, and a delay unit, and the waveform is adjusted by processing the phase modulation signal s5 using these adders, multipliers, and delay units.

[0185] The digital filter 224 is connected to a filter coefficient conversion unit 225. The digital filter 224 can be either a digital FIR filter or a digital IIR filter. The filter coefficient conversion unit 225 is connected to a phase shift value corresponding to the depth of the receiving focus from the phase shift value storage unit 18. Based on the phase shift value, the filter coefficients of the digital filter 224, such as the multiplication coefficients and delay coefficients (the values ​​of the weights used in the multiplication operation using each tap of the digital filter), are changed.

[0186] Specifically, such as Figure 10 As shown, the filter coefficient conversion unit 225 converts the phase information (phase displacement) output from the phase displacement storage unit 18 into filter coefficients for the digital filter 224, and modifies the filter coefficients prepared in advance by the ultrasonic imaging device. The modified filter coefficients are sent to the digital filter 224 and set. The digital filter 224 processes the waveform of the phase-modulated signal s5 using the modified filter coefficients to generate the phase-modulated signal s12. Thus, signal processing equivalent to that in the first embodiment can be performed through filter processing.

[0187] At this time, similar to the first embodiment, the phase compensation circuit control unit 17 instructs the output of the phase displacement amount corresponding to the phase displacement amount storage unit 18, and instructs the filter coefficient conversion unit to perform the conversion processing of the filter coefficients corresponding to the phase displacement amount.

[0188] That is, the ultrasonic camera device of the fourth embodiment can generate the same phase modulation signal S12 as the first embodiment or the third embodiment through filter control.

[0189] The other structures, operations, and effects of the ultrasonic imaging device in the fourth embodiment are the same as those in the first embodiment, and therefore descriptions are omitted. Furthermore, by using the digital filter 224, the ultrasonic imaging device in the fourth embodiment can simultaneously achieve the effects of both the ultrasonic imaging device of the first embodiment and the ultrasonic imaging device equipped with multiple phase compensation circuits of the second embodiment. Additionally, in the ultrasonic imaging device of the second embodiment, if it is necessary to achieve an effect equivalent to a device with a large number of phase compensation circuits 22-1 using the digital filter 224 of the fourth embodiment, it is only necessary to increase the number of taps (stages) of the filter coefficients of the digital filter 224. Thus, filter coefficients (filter coefficient series) having effects equivalent to those of the multiple phase compensation circuits 22-1 in the second embodiment can be generated.

[0190] Furthermore, the phase shift processing based on filter processing of the digital filter 224 in the ultrasonic imaging device of the fourth embodiment is implemented in software, not hardware, but on the CPU or GPU. Therefore, the hardware circuitry can be minimized. Moreover, since a filter block already present in the ultrasonic imaging device, such as a variable depth filter, can be used as the digital filter 224 to perform phase shift processing, the degree of adjustment in the design can be increased.

[0191] <<<Fifth Implementation Method>>>

[0192] use Figure 1 , Figure 7 , Figures 11-13 The ultrasonic camera device of the fifth embodiment will be described.

[0193] The structure of the ultrasonic camera device in the fifth embodiment is the same as that in the first or second embodiment, but the number of received signals after phase displacement generated according to the depth range of the subject 90 is different.

[0194] For example, such as Figure 1 as well as Figure 7 As shown, a switch 25 is provided to turn phase compensation circuit 22 and phase compensation circuits 22-1, 22-2, and 22-3 on / off. The control unit 11 disconnects phase compensation circuit 22 and phase compensation circuits 22-1, 22-2, and 22-3 according to the depth of the subject 90. Thus, for example, as... Figure 11 , Figure 12As shown, in a depth range 371 shallower than the transmission focus 30, the switch 25 is used to... Figure 1 Phase compensation circuit 22 Figure 7 The phase compensation circuits 22-1, 22-2, and 22-3 are disconnected and do not operate. In the depth range 372 that is shallower than the transmission focus 30, the phase compensation circuits 22 and 22-1, 22-2, and 22-3 are turned on by the switch 25 and operate, generating a received signal that is the same as the received signal generated by the spherical wave 301, etc., which is delayed by a delay time 351 or delay times 351, 352, and 353 respectively, and is reflected in the phase modulation signal s4.

[0195] Therefore, the computational load of the phase compensation circuit 22 can be suppressed, and the image with a range deeper than the transmission focus 30 can be made into a high resolution.

[0196] Furthermore, by switching switch 25, the number of received signals with phase shift generated in the depth range 371 shallower than the transmission focus 30 can be greater than the number of received signals with phase shift generated in the depth range 372 deeper than the transmission focus 30. Therefore, Figure 13 The portion that is shallower than the transmission focus 30 can generate a received signal equivalent to the portion that is deeper than the transmission focus 30, through a delay time of 350-353.

[0197] For example, for each part of the subject to be imaged (abdomen, circulatory organs, chest, legs, blood vessels, digestive organs, prenatal examination, etc.) and organ (liver, heart, kidneys, pancreas, gallbladder, ovaries, carotid artery, thyroid, etc.), a depth range in which increasing the amount of received signal after phase shifting generated by the phase compensation circuit 22 is effective for improving resolution is predetermined. Within this depth range, the control unit 11 can activate the phase compensation circuit 22 via switch 25. The selection of the part and organ is received from the operator via the control console 12 connected to the control unit 11.

[0198] Furthermore, the control unit 11 can also receive the desired depth range of the camera image from the operator via the console 12, and increase the number of phase compensation circuits 22 activated within that depth range. Alternatively, the phase compensation circuits 22 can be activated in advance within a given depth range.

[0199] Furthermore, the control unit 11 can also incorporate a machine learning model, which inputs various parameters related to ultrasonic imaging, such as imaging condition parameters, transmission and reception parameters, and probe type, as well as ultrasonic images or their received signals captured as preparation before the actual imaging, into the machine learning model, and calculates the number of received signals and / or the amount of phase displacement corresponding to the depth after appropriate phase displacement for each depth.

[0200] The machine learning model uses the following approach: taking the camera conditions, the captured image or received signal, and the received signal after phase shifting used in the image generation as input data, and using the obtained image, the number of received signals after phase shifting, and the amount of phase shift as correct data, and learning in advance.

[0201] Furthermore, since the accuracy and resolution of the camera vary depending on the type of organ, the machine learning model can also learn from different organs such as the liver, kidneys, blood vessels, and breasts.

[0202] Furthermore, in the first to fifth embodiments described above, the receiving beamformer 13 can be constructed in hardware. For example, a custom IC such as an ASIC (Application Specific Integrated Circuit) or a programmable IC such as a FPGA (Field-Programmable Gate Array) can be used to design the circuit to realize the functions of each part. Alternatively, some or all of the functions of the receiving beamformer 13 can be implemented in software. In this case, the receiving beamformer 13 is constructed from a computer equipped with a processor such as a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit) and memory. The CPU reads and executes the program stored in memory, thereby realizing these functions.

[0203] <<<Explanation of the effects of the implementation method>>>

[0204] use Figure 14 Sections (a) to (e) will explain the effects of this embodiment. Figure 14 (a) represents an ideal point image when taking an ideal image of a model (phantom) including tiny spheres. Figure 14 (b) is an ultrasonic imaging device using a conventional delay time (the delay time of each receiving scan line is considered as one curve) to capture images of... Figure 14 (a) Ultrasound image of the same model (comparative example).

[0205] Figure 14 (c) is the use of the ultrasonic camera device of embodiment 1, and Figure 14 The image taken from the same model (a) is obtained by adding circuit 23. Figure 5The received signal s2, obtained with a delay time of 350 seconds, and the received signal s3, obtained through phase shifting, are added together, and an ultrasonic image is generated based on the resulting phase-modulated signal s4. The phase shift of the received signal s3 relative to the received signal s2 is within one wavelength. Figure 14 The ultrasound image of (c) compared with the comparative example Figure 14 Compared with the ultrasound image in (b), it can be seen that the side lobes and noise components of the diffraction wave around the point can be suppressed to obtain an image that is close to the ideal point image.

[0206] on the other hand, Figure 14 (d) and Figure 14 The ultrasound image of (e) is compared with Figure 14 (c) Similarly, the same device as the ultrasonic imaging device in Embodiment 1 is used, but the ultrasonic image can be obtained by setting the phase shift of the received signal s3 relative to the received signal s2 to several wavelengths or more. If the phase shift is too large, in... Figure 14 In the ultrasound image of (d), artifacts are observed in other locations. Figure 14 In the ultrasound image of (e), the point image is split.

[0207] Therefore, compared with the comparative example, the ultrasonic imaging device of this embodiment can obtain high-resolution ultrasonic images with suppressed artifacts. Furthermore, it is known that the phase shift amount is preferably within one wavelength (2π rad).

Claims

1. An ultrasonic camera device, characterized in that, have: Transmit beamformer enables multiple ultrasonic elements from the connected ultrasonic element array to transmit phase-delayed ultrasonic waves to the subject in a manner that focuses on a given transmission focal point. as well as A receiving beamformer receives the received signals output by multiple ultrasonic elements of the ultrasonic element array that return ultrasonic waves transmitted from the subject to the ultrasonic element array, and performs receiving beamforming according to each receiving focus set within the subject to generate a first phase-modulated signal and a second phase-modulated signal. The receiving beamformer includes a delay circuit, an adder circuit, and a phase compensation circuit to delay the received signal. The delay circuit delays the received signals output by the plurality of ultrasonic elements by a given delay amount corresponding to the depth of the receiving focal point. The addition circuit has a first addition circuit and a second addition circuit. The first adder circuit performs an addition operation on the received signals that have been delayed by the delay circuit to generate the first phase modulation signal. The phase compensation circuit is configured after the first adder circuit to branch the first phase-modulated signal and generate a phase-compensated signal whose phase is shifted by a given phase displacement. The second adder circuit performs an addition operation on the first phase-modulated signal and the phase-compensated signal to generate the second phase-modulated signal.

2. The ultrasonic camera device according to claim 1, characterized in that, The delay circuit is a circuit structure that delays the received signals of the multiple ultrasonic elements at a low time resolution and then delays them at a higher time resolution than the low time resolution.

3. The ultrasonic camera device according to claim 2, characterized in that, An A / D converter is disposed between the delay circuit and the ultrasonic element to convert the received analog signals output by the ultrasonic element into digital signals. The delay circuit includes a memory for temporarily storing the received signal and an interpolation circuit. The interpolation circuit achieves the low time resolution delay processing by adjusting the timing of reading the received signal from the memory, and achieves the high time resolution delay processing by interpolating the received signal read from the memory.

4. The ultrasonic camera device according to claim 1, characterized in that, The phase shift is within one wavelength.

5. The ultrasonic camera device according to claim 1, characterized in that, Two or more phase compensation circuits are configured relative to the first phase modulation signal. If the phase displacements of two or more phase compensation circuits are different, the generated two or more phase-compensated signals are added to the first phase-modulated signal.

6. The ultrasonic camera device according to claim 1, characterized in that, The ultrasonic camera device also has a switch that turns the phase compensation circuit on / off according to the depth of the receiving focal point of the subject.

7. The ultrasonic camera device according to claim 5, characterized in that, The ultrasonic camera device also has a switch that switches the number of phase compensation circuits that are operating among the two or more phase compensation circuits according to the depth of the receiving focal point of the subject.

8. The ultrasonic camera device according to claim 1, characterized in that, The phase compensation circuit generates the phase-compensated signal only if the depth of the receiving focus is within a given range.

9. The ultrasonic camera device according to claim 1, characterized in that, The phase displacement of the phase compensation circuit varies according to the depth of the receiving focal point of the subject.

10. The ultrasonic camera device according to claim 8, characterized in that, The ultrasonic camera device also has a phase displacement storage unit, which pre-stores the phase displacement of each depth of the receiving focal point, and the phase compensation circuit shifts the phase of the received signal by using the phase displacement corresponding to the depth of the receiving focal point stored in the phase displacement storage unit.

11. The ultrasonic camera device according to claim 1, characterized in that, The receiving beamformer has a memory. Regarding the first transmission of the transmitting beamformer, the receiving beamformer generates the second phase modulation signal for multiple receiving focal points on multiple receiving scan lines and stores it in memory. Regarding subsequent transmissions, after generating the second phase modulation signal for multiple receiving focal points on multiple receiving scan lines, the receiving scan lines at the same positions are combined with the second phase modulation signal already stored in memory to perform transmitting aperture synthesis.

12. A signal processing method, comprising processing a received signal output by a plurality of ultrasonic elements in an ultrasonic element array that receives ultrasonic waves returned to the ultrasonic element array from a subject that has received ultrasonic waves, characterized in that, The received signals output by multiple ultrasonic elements are delayed by a given delay amount corresponding to the depth of the receiving focal point. The delayed received signals are added together to generate the first phase-modulated signal. The first phase-modulated signal is branched to generate a phase-compensated signal whose phase is shifted by a given phase displacement. The first phase-modulated signal and the phase-compensated signal are added together to generate the second phase-modulated signal.

Images