Ultrasonic imaging device and ultrasonic imaging method

Abstract

The goal is to achieve both improved reception sensitivity and increased frame rate when imaging in vivo sound sources. [Solution] By adding multiple received signal sequences 80 for each receiving channel, an added received signal sequence 86 consisting of multiple added received signals 88 is generated. Beamforming is repeatedly performed to form received beam data 94 from the added received signal sequence 86. This forms a received beam data sequence 92 from the added received signal sequence 86.

Description

Technical Field

[0001] The present disclosure relates to an ultrasonic imaging apparatus and an ultrasonic imaging method, and particularly to a technique for imaging a sound source in a living body.

Background Art

[0002] An ultrasonic imaging system is a system for treating or examining a living body as a patient. The ultrasonic imaging system has an insertion member and an ultrasonic imaging apparatus. In the ultrasonic imaging apparatus, an image representing the position of the insertion member inserted into the living body is generated and displayed. Treatment of the living body and the like are performed while referring to such an image.

[0003] As the ultrasonic imaging apparatus, an ultrasonic diagnostic apparatus is usually used. The insertion member is, for example, a catheter inserted into a blood vessel. Generally, prior to the insertion of the catheter, a guide wire is inserted into the blood vessel. The guide wire is also an insertion member. An ultrasonic imaging method for imaging an insertion member inserted into a blood vessel using an ultrasonic probe abutted against the surface of a living body is also called EVUS (Extra-vascular ultrasound).

[0004] An advanced ultrasonic imaging system has been proposed that uses the photoacoustic effect to image implantable devices. In this ultrasonic imaging system, a light-absorbing element is provided at the tip of the implantable device. Light pulses generated by a light pulse generator are guided into the interior of the implantable device through an optical fiber, and these light pulses irradiate the light-absorbing element. The absorption of the light pulses by the light-absorbing element generates a photoacoustic wave within the body. This photoacoustic wave is received by an ultrasonic probe in contact with the surface of the body. Based on the received information obtained in this way, an image representing the position of the light-absorbing element (i.e., the sound source) (hereinafter referred to as a photoacoustic image or PA image) is formed. For example, the photoacoustic image is combined with an ultrasonic image (hereinafter also referred to as a US image) generated by the transmission and reception of ultrasonic waves. The resulting composite image is displayed. By observing the composite image, the position of the tip of the implantable device can be clearly identified while observing the biological tissue. Note that elements or materials other than the light-absorbing element may be placed in the body as the sound source. The sound source can also be called a beacon.

[0005] Patent Document 1 describes an example of the advanced ultrasonic imaging system described above. However, Patent Document 1 does not describe the details of the processing of multiple received signals output from multiple transducers (particularly the processing before phase alignment). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2018 / 052093 [Overview of the project] [Problems that the invention aims to solve]

[0007] In ultrasound imaging devices that image sound sources within living organisms, beamforming (also called phase shaping or phase summing) is repeatedly performed to form received beam data from a sequence of received signals consisting of multiple received signals output from multiple transducers. This generates a sequence of received beam data (received frame data) consisting of multiple received beam data. To increase reception sensitivity, multiple received frame data arranged on the time axis are generally added together to generate summed received frame data.

[0008] Generally, there is a trade-off between frame rate and reception sensitivity. To increase the number of received frame data points added, the frame rate must be decreased. To increase the frame rate, the number of received frame data points added must be decreased. In ultrasound imaging systems, the processing load (computational load) for beamforming is substantial. If a high-speed processor is used as the processor that performs beamforming, it is possible to improve both the frame rate and reception sensitivity, but in that case, the cost of the ultrasound imaging system will increase.

[0009] The purpose of this disclosure is to reduce the processing load for beamforming while obtaining good reception sensitivity. Alternatively, the purpose of this disclosure is to achieve both improved reception sensitivity and improved frame rate when imaging in vivo sound sources. [Means for solving the problem]

[0010] The ultrasonic imaging apparatus according to this disclosure is characterized by including: a transducer array that receives multiple ultrasonic waves periodically generated by a sound source in a living body and outputs multiple received signal sequences in chronological order; multiple receivers that generate an added received signal sequence consisting of multiple added received signals by adding the multiple received signal sequences for each receiving channel; and a beamforming unit that repeatedly performs beamforming to form received beam data from the added received signal sequence, thereby forming a received beam data sequence from the added received signal sequence.

[0011] The ultrasonic imaging method according to this disclosure is characterized by including the steps of: receiving a plurality of ultrasonic waves periodically generated by a sound source in a living body and thereby acquiring a plurality of received signal sequences arranged in chronological order; generating an added received signal sequence consisting of a plurality of added received signals by adding the plurality of received signal sequences for each receiving channel; and performing beamforming to form received beam data from the added received signal sequence for each receiving beam position, thereby forming a received beam data sequence from the added received signal sequence. [Effects of the Invention]

[0012] According to this disclosure, it is possible to reduce the processing load for beamforming while obtaining good reception sensitivity. Alternatively, according to this disclosure, it is possible to achieve both improved reception sensitivity and improved frame rate when imaging in vivo sound sources. [Brief explanation of the drawing]

[0013] [Figure 1] This is a diagram showing the configuration of an ultrasonic imaging system according to an embodiment. [Figure 2] This figure shows the processing method related to the comparative example. [Figure 3] This figure shows the processing method according to the embodiment. [Figure 4] This is a diagram showing the configuration of the receiving unit according to the embodiment. [Figure 5] This figure shows the transmission and reception sequence according to the embodiment. [Figure 6] This is a diagram showing the operation of the receiver. [Figure 7] This diagram shows the configuration of an ultrasonic imaging system according to another embodiment. [Figure 8] This figure shows several receiving apertures set on an oscillator array. [Figure 9] This diagram shows the configuration of the receiving unit according to another embodiment. [Figure 10] This diagram shows the relationship between the number of receptions and the number of additions. [Figure 11] This figure shows the change in receiving aperture size according to the receiving point depth. [Figure 12] It is a diagram showing the configuration of the receiving unit according to the first modification example. [Figure 13] It is a diagram showing the configuration of the receiving unit according to the second modification example. [Figure 14] It is a diagram showing the addition count profile according to the third modification example. [Figure 15] It is a timing chart showing the operation of the receiving unit according to the third modification example.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments will be described based on the drawings.

[0015] (1) Outline of Embodiment The ultrasonic imaging apparatus according to the embodiment includes a transducer array, a plurality of receivers, and a former. The transducer array receives a plurality of ultrasonic waves periodically generated by a sound source in a living body, and outputs a plurality of received signal sequences in time series order. The plurality of receivers generate an added received signal sequence composed of a plurality of added received signals by adding the plurality of received signal sequences for each reception channel. The former repeatedly executes beamforming for forming received beam data from the added received signal sequence, thereby forming a received beam data sequence from the added received signal sequence.

[0016] The above configuration adds a plurality of received signal sequences before repeatedly executing beamforming. According to the above configuration, a good SNR (Signal-to-Noise Ratio) can be obtained by adding the plurality of received signal sequences. Further, according to the above configuration, the processing ability of the former that executes beamforming in determining the frame rate does not become a bottleneck (limiting factor). Therefore, it is possible to achieve both an improvement in reception sensitivity and an improvement in frame rate.

[0017] The sound source within the living body is, for example, one that generates ultrasound through the photoacoustic effect. Each receiving channel corresponds to a system or route for processing the received signal, and specifically corresponds to an individual receiver. When generating multiple received signal sequences, the entire transducer array may be operated, or only a part of the transducer array may be operated. Averaging, weighted addition, etc., may be performed as the summation of multiple received signals for each receiving channel. Beamforming corresponds to phase shaping or phase shaping addition. Multiple beamforming operations are performed sequentially when generating one received frame data. Hereinafter, these multiple beamforming operations will be referred to as the beamforming process, depending on the context. Based on the received frame data, an image representing the location of the sound source (e.g., a photoacoustic image) is formed.

[0018] In one embodiment, each receiver in a plurality of receivers includes an adder that generates an added received signal by adding multiple received signals that are input in chronological order. The SNR is improved by adding the multiple received signals. If each individual receiver is composed of a processor, each processor functions as an adder. A single processor may function as multiple receivers. In that case, the single processor functions as multiple adders.

[0019] In this embodiment, each receiver includes a first storage area for storing a new received signal that has been input, and a second storage area for storing an added received signal output from an adder. The adder in each receiver adds the new received signal read from the first storage area and the added received signal read from the second storage area, thereby generating a new added received signal to be stored in the second storage area.

[0020] This configuration allows for easy generation of an added received signal, and in particular, it eliminates the need for sophisticated synchronization control between the input of a new received signal and the generation of the added received signal. The first and second storage areas may be provided on a single memory. Multiple first storage areas and multiple second storage areas may be provided on a single memory.

[0021] The ultrasonic imaging apparatus according to this embodiment includes a controller and a multiplexer. The controller distributes multiple active transducers to a transducer array. The multiplexer connects multiple receivers to the multiple active transducers. This configuration can be used when the number of receiving channels is less than the number of transducers constituting the transducer array.

[0022] In this embodiment, multiple effective oscillators constitute the receiving aperture. The controller changes the size of the receiving aperture according to the receiving point depth. For example, the size of the receiving aperture increases continuously or stepwise as the receiving point depth increases. When receiving dynamic focus is applied, the receiving focal depth is changed dynamically. Each individual receiving focal point is a receiving point.

[0023] The ultrasonic imaging apparatus according to this embodiment includes a calculator and a controller. The calculator calculates an evaluation value by evaluating an additive received signal sequence or a received beam data sequence. The controller changes the number of received signal sums for each received frame period based on the evaluation value. This configuration allows for an improvement in frame rate while maintaining a constant image quality. The evaluation value is a value indicating the quality of the additive received signal sequence or the received beam data sequence, for example, the signal-to-noise ratio (SNR).

[0024] In this embodiment, a first reception frame period and a second reception frame period are set on the time axis. Each receiver adds the last summation received signal in the first reception frame period to the first received signal in the second reception frame period, thereby generating the first summation received signal in the second reception frame period. This configuration allows for an increase in the number of received signals to be added without sacrificing the frame rate. This configuration may be adopted when responsiveness and time resolution are not issues.

[0025] In the embodiment, each receiver weight-adds the last summation received signal in the first reception frame period to the first received signal in the second reception frame period. The ultrasonic imaging apparatus according to the embodiment includes a calculator and a controller. The calculator evaluates the summation received signal sequence or received beam data sequence corresponding to the first reception frame period and calculates an evaluation value. The controller controls the weighted addition based on the evaluation value. With this configuration, depending on the situation, priority is given to improving the quality of the summation received signal or to preventing a decrease in responsiveness.

[0026] In this embodiment, the beamforming device changes the timing of beamforming execution according to the received beam position in the electronic scanning direction, thereby changing the number of received signal summations according to the received beam position. This configuration changes the image quality depending on the received beam position.

[0027] In this embodiment, the number of received signal summations corresponding to the central receiving beam position in the electronic scanning direction is greater than the number of received signal summations corresponding to the receiving beam positions at the edges in the electronic scanning direction. This configuration allows for higher image quality in the center of the image compared to the image quality at the edges.

[0028] The ultrasonic imaging method according to this embodiment includes a receiving step, an adding step, and a forming step. In the receiving step, multiple ultrasonic waves periodically generated by a sound source in the living body are received, thereby acquiring multiple received signal sequences arranged in chronological order. In the adding step, the multiple received signal sequences are added together for each receiving channel, thereby generating an added received signal sequence consisting of multiple added received signals. In the forming step, beamforming is performed to form received beam data from the added received signal sequence for each receiving beam position, thereby forming a received beam data sequence from the added received signal sequence.

[0029] The above ultrasound imaging method is performed using an ultrasound imaging device. An ultrasound diagnostic device may be used as the ultrasound imaging device.

[0030] (2) Details of the embodiment Figure 1 shows an ultrasonic imaging system according to an embodiment. The illustrated ultrasonic imaging system is a medical system installed in a medical institution such as a hospital, and is specifically used when advancing the tip of an implantable member to the affected area while observing a photoacoustic image (PA image) that shows the position of the tip of the implantable member. The ultrasonic imaging system may be used for other purposes.

[0031] The ultrasonic imaging system comprises an optical pulse generator 10, an ultrasonic diagnostic device 12, and an insertion member 18. The ultrasonic diagnostic device 12 functions as an ultrasonic imaging device.

[0032] The optical pulse generator 10 has a light source 17. The light source 17 is a laser that generates a pulse train of laser light. The base end of an optical fiber 19 is connected to the light source 17. The tip of the optical fiber 19 is located inside the tip of the insertion member 18.

[0033] The insertion member 18 is, for example, a catheter inserted into a blood vessel in the living body 16. Other examples of the insertion member 18 include a guidewire and a puncture needle. A light-absorbing element 18a made of a light-absorbing material is provided inside the tip of the insertion member 18. When a light pulse is irradiated onto the light-absorbing element 18a, the light-absorbing element 18a absorbs the light pulse. At that time, a photoacoustic wave 20 is generated as ultrasound due to the photoacoustic effect. The photoacoustic wave 20 propagates within the living body 16 as a pulsed wave. The light-absorbing element 18a functions as a sound source within the living body 16. By imaging the sound source, the position of the tip of the insertion member 18 can be determined in real time.

[0034] Next, the ultrasound diagnostic device 12 will be described. The ultrasound diagnostic device 12 has a B-mode mode for generating B-mode tomographic images (US images) and a PA mode for generating photoacoustic images (PA images). In practice, the B-mode and PA modes are executed alternately. That is, as will be described later, the frame period for B-mode and the frame period for PA mode are set alternately. Hereinafter, the frame period for PA mode will be referred to as the received frame period, depending on the circumstances.

[0035] The ultrasound probe 21 is brought into contact with the surface 16A of the living body 16. The ultrasound probe 21 is usually held by the examiner (doctor, medical technologist, etc.). The ultrasound probe 21 may also be held by a robotic arm or the like. The ultrasound probe 21 has a transducer array 22 composed of multiple transducers.

[0036] During the B-mode frame period, ultrasound waves transmitted from the transducer array 22 are radiated into the living body 16, and the reflected waves from within the living body 16 are received by the transducer array 22. This transmission and reception is repeated. Alternatively, during the B-mode frame period, the transmitted beam and the received beam are electronically scanned in the electronic scanning direction.

[0037] During the frame period for PA mode, the oscillator array 22 does not perform transmission operations, but only reception operations. More specifically, multiple photoacoustic waves 20 intermittently generated within the living organism 16 are sequentially received by the oscillator array 22. Multiple reception periods are set on the time axis according to the reception cycle. Each reception period is the period for the oscillator array 22 to receive one photoacoustic wave. The optical pulse period and the reception period are the same. A configuration may be provided to coincide the start of the optical pulse period with the start of the reception period.

[0038] The transmitting unit 24 is a transmitting beamformer. That is, during transmission, the transmitting unit 24 outputs multiple transmission signals in parallel to multiple oscillators. The transmitting unit 24 is composed of, for example, an electronic circuit.

[0039] The receiving unit 26 is an electronic circuit that processes multiple received signals output in parallel from multiple oscillators during reception. The receiving unit 26 may be composed of one or more processors. Examples of such processors include FPGAs, DSPs, and ASICs.

[0040] Specifically, the receiving unit 26 has a plurality of receivers 27, a controller 28, and a beamforming unit 30. The plurality of receivers 27 correspond to multiple receiving channels. Each receiver has an amplifier 32, an ADC 33, and a processing unit 34. The beamforming unit 30 is a module that performs beamforming processing. The beamforming unit 30 has an adder 36. Some functions of the controller 28 belong to the beamforming unit 30.

[0041] The controller 28 controls the operation of multiple receivers 27. Specifically, during the B-mode frame period, the controller 28 controls the beamforming process. During the B-mode frame period, the receiver 26 does not perform summation processing for each received channel, and each processing unit 34 functions as a buffer to temporarily store the received signal for beamforming. During the PA-mode frame period, the controller 28 controls both summation processing and beamforming processing for each received channel. The operation of the receiver 26 during the PA-mode frame period (particularly the generation of the summation received signal sequence) will be described in detail later.

[0042] When B mode is executed, the receiver 26 outputs received frame data (first received frame data). The first received frame data is sent to the US image generation unit 40 via the beam data processing unit 38. When PA mode is executed, the receiver 26 outputs received frame data (second received frame data). The second received frame data is sent to the PA image generation unit 42 via the beam data processing unit 38.

[0043] The first received frame data consists of multiple received beam data arranged in the electronic scanning direction. The second received frame data also consists of multiple received beam data arranged in the electronic scanning direction. However, unlike the first received frame data, the second received frame data is data generated after addition processing in the receiving unit 26. Each received beam data consists of echo data arranged in the depth direction. Examples of electronic scanning methods that can be selected during B-mode and PA-mode execution include electronic linear scanning and electronic sector scanning.

[0044] The beam data processing unit 38 is composed of electronic circuits that process each received beam data. The beam data processing unit 38 includes an envelope detection circuit, a filter circuit, a logarithmic transformation circuit, and the like.

[0045] The US image generation unit 40 functions when B-mode is being executed. The US image generation unit 40 is a module that has a digital scan converter (DSC) and generates first display frame data from first received frame data. Specifically, the US image generation unit 40 generates a tomographic image (B-mode tomographic image) representing the tissue structure as a US image. The DSC has a coordinate transformation function, a pixel interpolation function, etc.

[0046] The PA image generation unit 42 functions when PA mode is executed. The PA image generation unit 42 is a module that has a DSC and a sound source identification unit and generates second display frame data from second received frame data. The sound source identification unit identifies the location of the sound source in the living body by detecting or extracting the sound source signal contained in the second display frame data generated by the DSC. The PA image includes a marker that represents the location of the sound source in the beam scanning plane. The marker is, for example, a point with high brightness or a predetermined color.

[0047] The display processing unit 44 generates a composite image by superimposing a PA image onto a US image (tomographic image). The composite image is displayed on the display unit 46. The display unit 46 is composed of an organic EL display device, a liquid crystal display, etc. The US image generation unit 40, the PA image generation unit 42, and the display processing unit 44 may each be composed of a processor. The CPU described below may function as the US image generation unit 40, the PA image generation unit 42, and the display processing unit 44.

[0048] The main control unit 48 controls the operation of each element that constitutes the ultrasound diagnostic apparatus 12. The main control unit 48 sets the transmission and reception sequence and controls the operation of the transmission unit 24 and the reception unit 26. The main control unit 48 is composed of, for example, a CPU that executes a program.

[0049] The following details the processes performed by the receiver in PA mode.

[0050] Figure 2 shows the processing for the comparative example. The vertical axis is the time axis. In the comparative example, multiple received signal sequences 64 are acquired in chronological order. Each received signal sequence 64 consists of multiple received signals 66 output from multiple oscillators constituting the array oscillator. x indicates the direction of electron scanning, and y indicates the depth direction.

[0051] By repeatedly executing the beamforming process 68, multiple received beam data sequences 70 are generated from multiple received signal sequences 64. Each received beam data sequence consists of multiple received beam data sequences 72. In the comparative example, to increase the receiving sensitivity, multiple received beam data sequences 70 are added together (see reference numeral 74), thereby generating added received beam data 76. The added received beam data 76 consists of multiple added beam data sequences 78.

[0052] In the comparative example, it is possible to improve the SNR, but each beamforming process 68 must be executed at high speed according to the set frame rate. If the processor that repeatedly executes the beamforming process 68 does not have high performance, it will not be possible to execute each beamforming process 68 at high speed, and the frame rate will decrease.

[0053] Figure 3 shows the processing according to the embodiment. The vertical axis is the time axis. In this embodiment as well, multiple received signal sequences 80 are acquired in chronological order. Each received signal sequence consists of multiple received signals 82 output from multiple oscillators constituting the array oscillator.

[0054] In this embodiment, prior to the beamforming process 90, a plurality of received signal sequences 80 are added together (specifically, averaged) (see reference numeral 84), thereby generating an added received signal sequence 86. The added received signal sequence 86 is composed of a plurality of added received signals 88 arranged in the direction of electronic scanning. The beamforming process 90 based on the added received signal sequence 86 forms a received beam data sequence 92. The received beam data sequence 92 is composed of a plurality of received beam data 94 arranged in the direction of electronic scanning.

[0055] In general, the summation of multiple received signals for each receiving channel can be performed at high speed. In this embodiment, a received beam data sequence 92 with a good SNR can be generated by performing the beamforming process 90 only once. Therefore, even if the performance of the processor performing the beamforming process is not high, the processing according to this embodiment can be realized, and it is possible to achieve both improved receiving sensitivity and improved frame rate. Note that if one received frame data (see reference numeral 92) consists of n received beam data 94, the beamforming process 90 consists of n beamforming operations. n is an integer of 2 or more (actually 100 or more).

[0056] In Figure 4, (A) shows the transmission and reception sequence according to the embodiment. The horizontal axis is the time axis. T1 represents the frame period for B mode, and T2 represents the frame period for PA mode. The time length t1 of the B mode frame period T1 is, for example, 25 ms. The time length t2 of the PA mode frame period T2 is, for example, 25 ms. When considering two adjacent T2s with T1 in between, the earlier T2 can be called the first received frame period, and the later T2 can be called the second received frame period.

[0057] (B) shows details of the frame period T1 for B-mode and the frame period T2 for PA-mode. During the frame period T1 for B-mode, multiple ultrasonic pulses 61 are transmitted according to the ultrasonic pulse repetition frequency. The ultrasonic pulse repetition frequency is, for example, 8 kHz. T3 shows the ultrasonic pulse repetition period. T4 shows the reception period.

[0058] (C) shows a train of optical pulses. The train of optical pulses consists of multiple optical pulses 62 arranged on the time axis. Each optical pulse generates an optical acoustic wave. The optical pulse repetition frequency is, for example, 1 kHz. T5 indicates the optical pulse repetition period.

[0059] In the PA mode frame period T2, multiple reception periods T6 are set to receive multiple intermittently occurring photoacoustic waves. The multiple reception periods T6 are set to have the same period as the optical pulse repetition period T5. One reception of a photoacoustic wave results in the output of one received signal train from the array oscillator.

[0060] In the example shown in Figure 4, the generation timing of each optical pulse 62 coincides with the start timing of each reception period T6, but they may be out of sync. Control may be performed to synchronize the generation timing of the former with the start timing of the latter, or a process may be performed to correct the difference in timing between the two.

[0061] Figure 5 shows an example configuration of the receiving unit shown in Figure 1. Specifically, Figure 5 shows one receiver 27 and a controller 28. In the illustrated configuration example, the receiver 27 has an amplifier 32, an ADC 33, and a processing unit 34. The processing unit 34 has a memory 50 and an adder 52. A first storage area 54 and a second storage area 56 are provided on the memory 50. The memory 50 is composed of one or more physical memories. A single memory may be shared by multiple receivers 27. That is, multiple first storage areas 54 and multiple second storage areas 56 may be set on a single memory.

[0062] The received signal A output from the ADC33 is stored in the first memory area 54. The added received signal is stored in the second memory area 56. The adder 52 adds the received signal B read from the first memory area 54 and the added received signal C read from the second memory area 56 to generate a new added received signal D. The new added received signal D is stored in the second memory area 56. This reading, adding, and writing process is repeated. The added received signal E generated in the final addition is read from the second memory area 56, and this added received signal E is used in the beamforming process.

[0063] The controller 28 is composed of a processor or electronic circuit. The CPU described above may also function as the controller 28. The controller 28 functions as an adder controller 58 and a phase-shaping controller 60. The adder controller 58 controls the addition process for each receiving channel. Multiple adder received signals corresponding to multiple receiving channels constitute an adder received signal sequence. The phase-shaping controller 60 is part of the former and controls the beamforming process based on the adder received signal sequence. The beamforming process generates a received beam data sequence.

[0064] Figure 6 shows the receiver's operation as a timing chart. The horizontal axis is the time axis. Symbol 200 indicates an addition process consisting of m operation units. m is an integer greater than or equal to 2 (actually 5 or 10 or greater). Each operation unit consists of reading the received signal B and the added received signal C, generating the added received signal D by adding them together, and writing the added received signal D. After the addition process, beamforming is performed based on the added received signal sequence. The beamforming process consists of n beamforming operations. One beamforming operation generates one received beam data.

[0065] Figures 7 and 8 show an example of the configuration of an ultrasonic imaging system according to another embodiment (second embodiment). Components included in Figures 7 and 8 that are the same as those shown in Figures 1 and 5 are denoted by the same reference numerals as those used for the components shown in Figures 1 and 5.

[0066] In Figure 7, a multiplexer 96 is provided between the ultrasonic probe 21 and the receiver 26. The controller 28A controls the operation of the multiplexer 96. In the configuration shown in Figure 7, the number of receiving channels is less than the number of transducers constituting the transducer array. As will be explained below, when PA mode is executed, multiple effective transducers constituting the receiving aperture are distributed across the entire transducer array 22.

[0067] Figure 8 shows the configuration of the receiving unit according to the second embodiment. The controller 28A has a receiving aperture controller 104. The receiving aperture controller 104 controls the receiving aperture, and specifically controls the operation of the multiplexer.

[0068] In Figure 9, (A) shows the receiving aperture settings for a comparative example, and (B) shows the receiving aperture settings for the second embodiment. For the sake of simplicity, in the following explanation, the array oscillator will be assumed to consist of 15 oscillators, and the receiving aperture will consist of 5 oscillators. That is, the number of receiving channels will be assumed to be 5.

[0069] In the comparative example, to acquire one frame of received information, three receiving apertures 100A, 100B, and 100C are set sequentially, meaning that three receptions are performed. Each of the five oscillators constituting each receiving aperture 100A, 100B, and 100C is an effective oscillator.

[0070] In the second embodiment, five effective oscillators 102 constituting a receiving aperture are distributed across the entire oscillator array 22. All other oscillators are inactive oscillators 101. One or more inactive oscillators 101 exist between two adjacent effective oscillators 102. For each receiving channel connected to an individual effective oscillator 102, multiple received signals output from that individual effective oscillator 102 are added together.

[0071] Figure 10 shows the relationship between the number of receptions and the number of additions. The horizontal axis represents the number of receptions, and the vertical axis represents the number of additions. Reference numeral 106 indicates the relationship relating to the comparative example. Reference numeral 108 indicates the relationship relating to the second embodiment. In the second embodiment, the number of additions increases linearly with increasing receptions. In the comparative example, the number of additions increases in a stepwise manner with increasing receptions, but the rate of increase is considerably smaller than that of the second embodiment.

[0072] In the second embodiment, the size of the receiving aperture is changed, as shown in Figure 11. In Figure 11, the solid line 114 shows the change in aperture size according to the second embodiment, and the dashed line 112 shows the change in aperture size according to the comparative example described above. In Figure 11, the horizontal axis is the depth axis, and the vertical axis is the number of effective oscillators.

[0073] In the second embodiment, in the illustrated example, the receiving aperture size increases linearly from depth 0 to depth y2, specifically increasing from a minimum value to 5 effective oscillators. The receiving aperture size remains constant in the range greater than depth y2.

[0074] In the comparative example, the receiving aperture size increases linearly from depth 0 to depth y1, specifically increasing from a minimum value to 5 effective oscillators. The receiving aperture size remains constant in the range greater than depth y1.

[0075] In the second embodiment, three received signals are added for each receiving channel to acquire one frame of received information. On the other hand, in the comparative example, it is necessary to sequentially set the receiving aperture at three different positions to acquire one frame of received information. Considering these differences, the SNR of the second embodiment is about the same as that of the comparative example near depth y1. On the other hand, the SNR of the second embodiment is superior to that of the comparative example near depth y2.

[0076] In the second embodiment, an increase in artifacts caused by grating lobes, etc., is expected due to the increased distance between adjacent effective oscillators. However, this is not considered a major problem when imaging to identify the location of the sound source. In the first embodiment shown in Figure 1, etc., the receiving aperture size may be changed according to the receiving point depth.

[0077] Figure 12 shows the first modified examples of the first and second embodiments. Components included in Figure 12 that are the same as those shown in Figure 5 are denoted by the same reference numerals as those used for the components shown in Figure 5.

[0078] Controller 28B has an adder controller 58A. The adder controller 58A has an arithmetic unit 116 that calculates an evaluation value. Specifically, the arithmetic unit 116 calculates the SNR as an evaluation value based on a plurality of summation received signals E (i.e., summation received signal sequences) obtained at the end of each reception frame period (frame period for PA mode). Based on the SNR calculated in the (N-1)th reception frame period, the adder controller determines the number of received signals to be added (i.e., the number of receptions) in the Nth reception frame period.

[0079] For example, the arithmetic unit 116 detects the maximum value (MAX), minimum value (MIN), and root mean square (RMS) in the summation received signal sequence, and calculates the SNR using (MAX-MIN) / RMS. The summation controller 58A determines to reduce the number of receptions if the SNR exceeds a certain threshold. A numerical value other than SNR may be calculated as the evaluation value. The SNR may be calculated as the evaluation value for each receiver, and the number of receptions may be controlled based on multiple SNRs calculated by multiple receivers.

[0080] According to the first modification, for example, if a fairly good SNR is obtained by summing during the N-1th received frame period, the number of receptions in the Nth received frame period will decrease, making it possible to increase the frame rate.

[0081] Let me explain in detail. In a transmit / receive sequence, if the frame duration for B-mode is 20ms and the frame duration for PA-mode (receive frame duration) is 20ms, the overall frame rate of the transmit / receive sequence is 25Hz. If the receive frame duration can be shortened to 5ms, the overall frame rate of the transmit / receive sequence can be increased to 40Hz. Of course, if the evaluation value deteriorates, the receive frame duration will be lengthened to increase the number of summation cycles.

[0082] In the example configuration shown in Figure 12, the evaluation value was calculated based on an additive received signal sequence. However, the evaluation value may also be calculated based on a received beam data sequence consisting of multiple received beam data Fs.

[0083] Figure 13 shows a second modification of the first and second embodiments. Components included in Figure 13 that are the same as those shown in Figure 5 are denoted by the same reference numerals as those used for the components shown in Figure 5.

[0084] In the second modified example, in each receiver 27, the last summation received signal E during the N-1th received frame period is stored in the second memory area 56. Then, during the Nth received frame period, the first received signal B and the last summation received signal E are added together to generate the first summation received signal D. This first summation received signal D is stored in the second memory area 56.

[0085] As described above, in the second modified example, the summation result is carried over between two temporally adjacent received frames, thus increasing the number of received signal summations.

[0086] In the second modified example, the adder controller 58B within the controller 28C may function as the arithmetic unit 116. The arithmetic unit 116 calculates an evaluation value based on an adder receiving signal sequence consisting of multiple adder receiving signals E or a received beam data sequence consisting of multiple received beam data F. The evaluation value is, for example, the SNR. If the evaluation value is smaller than a threshold, the addition across received frames may be performed, and if the evaluation value is larger than the threshold, the addition across received frames may be postponed. The addition across received frames is actually a weighted addition, and the weights are changed according to the evaluation value (see reference numeral 118).

[0087] Next, a third modification of the first and second embodiments will be described using Figures 14 and 15. In the third modification, the number of received signal additions is changed according to the received beam position (received beam number) in the electronic scanning direction.

[0088] In Figure 14, the horizontal axis represents the received beam number, and the vertical axis represents the number of received signal summations. Profile 120 shows the number of received signal summations for each received beam number. The number of received signal summations corresponding to both ends of the oscillator array is relatively small, while the number of received signal summations corresponding to the center of the oscillator array is relatively large. To realize Profile 120, it is necessary to change the readout timing of the summation of received signals required for beamforming for each received beam number.

[0089] Figure 15 shows the beamforming process in the third modified example as a timing chart. The horizontal axis is the time axis. (A) shows multiple reception periods. Specifically, 50 reception periods, numbered #1 to #50, are set within a single reception frame period. T7 indicates the duration of the reception period. T7 is, for example, 40 μs.

[0090] (B) shows multiple summing periods. T8 indicates the duration of the summing period, which is, for example, 10 μs. (C) shows multiple beamforming periods. For example, T8 is 80 μs and T9 is 160 μs.

[0091] (D) indicates the beamforming target. In the illustrated example, there are received beam numbers from 1 to 192 (see Figure 14). In other words, the beamforming process ultimately generates 192 received beam data L1 to L192. In the illustrated example, on the time axis, received beam data L1 to L8 are generated within the period from 9.50 to 9.75 ms, followed by received beam data L185 to L192. Received beam data L9 to L16 are generated within the period from 9.75 to 10.00 ms, followed by received beam data L177 to L184. Received beam data L89 to L104 are generated within the period from 12.25 to 12.50 ms.

[0092] In the third modification, when forming the received beam data corresponding to the edge of the electronic scanning direction, the summed received signal group generated by the 38th summation is used. When forming the received beam data corresponding to the center of the electronic scanning direction, the summed received signal group generated by the 49th summation is used. Generally, the user is most interested in the central part of the image, or the ultrasonic probe is operated so that the area of ​​interest is in the central part of the image. From this perspective, in the fourth modification, the quality of the central part is prioritized over the quality of the edges.

[0093] As described above, in the fourth modification, the number of received signal summations is changed according to the receiving beam position, meaning that the readout timing of the received signal group is changed according to the receiving beam position. This provides the advantage of improving the frame rate. [Explanation of Symbols]

[0094] 10 Optical pulse generator, 12 Ultrasound diagnostic device, 18 Insertion member, 22 Transducer array, 26 Receiving unit, 27 Receiver, 28 Controller, 30 Forming unit, 34 Processing unit, 36 Adder, 52 Adder, 54 First memory area, 56 Second memory area, 58 Adder controller, 60 Phase adjustment controller.

Claims

1. A transducer array that receives multiple ultrasound waves periodically generated by sound sources within the body and outputs multiple received signal sequences in chronological order, Multiple receivers that generate an added received signal sequence consisting of multiple added received signals by adding the aforementioned multiple received signal sequences for each receiving channel, A beamforming device that repeatedly performs beamforming to form received beam data from the summed received signal sequence, thereby forming a received beam data sequence from the summed received signal sequence, An ultrasonic imaging device characterized by the following features.

2. In the ultrasonic imaging apparatus according to claim 1, Each of the aforementioned plurality of receivers includes an adder that generates an added received signal by adding up a plurality of received signals that are input in chronological order. An ultrasonic imaging device characterized by the following features.

3. In the ultrasonic imaging apparatus according to claim 2, Each of the receivers includes a first storage area for storing a new received signal that has been input, and a second storage area for storing an added received signal output from the adder. The adder in each receiver adds the new received signal read from the first storage area and the added received signal read from the second storage area, thereby generating a new added received signal to be stored in the second storage area. An ultrasonic imaging device characterized by the following features.

4. In the ultrasonic imaging apparatus according to claim 1, A controller that distributes multiple effective oscillators to the oscillator array, A multiplexer that connects the multiple receivers to the multiple effective oscillators, An ultrasonic imaging device characterized by including [a specific component].

5. In the ultrasonic imaging apparatus according to claim 4, The plurality of effective oscillators constitute a receiving aperture, The controller changes the size of the receiving aperture according to the depth of the receiving point. An ultrasonic imaging device characterized by the following features.

6. In the ultrasonic imaging apparatus according to claim 1, A calculator that calculates an evaluation value by evaluating the summation received signal sequence or the received beam data sequence, A controller that changes the number of times the received signal is added for each received frame period based on the aforementioned evaluation value, An ultrasonic imaging device characterized by including [a specific component].

7. In the ultrasonic imaging apparatus according to claim 1, A first reception frame period and a second reception frame period are set on the time axis. Each receiver adds the last summation received signal in the first reception frame period and the first received signal in the second reception frame period to generate the first summation received signal in the second reception frame period. An ultrasonic imaging device characterized by the following features.

8. In the ultrasonic imaging apparatus according to claim 7, Each receiver weights and adds the last received signal in the first receiving frame period and the first received signal in the second receiving frame period. The aforementioned ultrasonic imaging device, A calculator that evaluates the summation received signal sequence or received beam data sequence corresponding to the first received frame period and calculates an evaluation value, A controller that controls the weighted addition based on the evaluation value, An ultrasonic imaging device characterized by including [a specific component].

9. In the ultrasonic imaging apparatus according to claim 1, The beamforming apparatus changes the timing of beamforming execution according to the position of the received beam in the electronic scanning direction, thereby changing the number of times the received signal is added according to the position of the received beam. An ultrasonic imaging device characterized by the following features.

10. In the ultrasonic imaging apparatus according to claim 9, The number of received signal sums corresponding to the central receiving beam position in the aforementioned electronic scanning direction is greater than the number of received signal sums corresponding to the receiving beam positions at the edges in the aforementioned electronic scanning direction. An ultrasonic imaging device characterized by the following features.

11. The process involves receiving multiple ultrasound waves periodically generated by sound sources within a living organism, thereby obtaining multiple received signal sequences arranged in chronological order, and The process of generating an added received signal sequence consisting of multiple added received signals by adding the aforementioned multiple received signal sequences for each receiving channel, The process involves performing beamforming to form received beam data from the summation of received signal sequences for each receiving beam position, thereby forming a received beam data sequence from the summation of received signal sequences, An ultrasonic imaging method characterized by including

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