WO2012002006A1 - Ultrasound diagnosis device and program - Google Patents

Ultrasound diagnosis device and program Download PDF

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Publication number
WO2012002006A1
WO2012002006A1 PCT/JP2011/056213 JP2011056213W WO2012002006A1 WO 2012002006 A1 WO2012002006 A1 WO 2012002006A1 JP 2011056213 W JP2011056213 W JP 2011056213W WO 2012002006 A1 WO2012002006 A1 WO 2012002006A1
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WIPO (PCT)
Prior art keywords
sampling
data
display
sampling frequency
acquired
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PCT/JP2011/056213
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French (fr)
Japanese (ja)
Inventor
加藤　美樹
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コニカミノルタエムジー株式会社
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Priority to JP2012522481A priority Critical patent/JP5803913B2/en
Publication of WO2012002006A1 publication Critical patent/WO2012002006A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/52017—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 particularly adapted to short-range imaging
    • G01S7/52023—Details of receivers
    • G01S7/52034—Data rate converters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/52017—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 particularly adapted to short-range imaging
    • G01S7/52023—Details of receivers
    • G01S7/52044—Scan converters

Definitions

  • the present invention relates to an ultrasonic diagnostic apparatus and a program.
  • a vibration probe provided with a large number of transducers (transducers) arranged in a one-dimensional or two-dimensional form, and transmits and receives ultrasonic waves to and from a subject such as a living body. Converts sound waves into electrical signals, samples them, performs phasing addition on the data obtained by sampling, generates an ultrasonic image based on the data obtained as a result, and displays this on the image display device.
  • transducers transducers
  • Such an ultrasonic diagnostic apparatus has been devised in various ways to obtain a good image in order to enable accurate diagnosis.
  • two interpolation lines at a line position shifted from the position of the reception line are weighted with data from the reception line in proportion to the interval from the reception line position to the scanning line, and the weighted data is combined to form the interpolation line.
  • display an ultrasonic image based on this for example, patent documents 1).
  • an echo signal in units of frames is sampled from a diagnostic region with a predetermined sampling clock and taken into the image memory, the whole image is taken into the first image memory with a sampling clock thinned to 1 / N, and an enlarged image is obtained.
  • a window signal indicating a region of interest which is gated with a predetermined sampling clock, fetched into a second image memory, and displays each image at the same frame rate (for example, Patent Document 2).
  • the received signal is sampled at as fine a pitch as possible, the S / N (Signal-Noise ratio) after phasing addition is improved and the reproducibility when the waveform is reproduced based on the sampled data. Since it becomes faithful, a higher sampling frequency can generate a better image.
  • the resolution of the image display device is about 1000 dots vertically, as long as image display is being performed, all of the sampled signals cannot be reflected in the image display, and the process of converting the number of display pixels (pixel number conversion) It was necessary to reduce the amount of data to a size that allows data to be displayed after processing. In many cases, this pixel number conversion process generates waveform distortion and interpolation error in principle.
  • An object of the present invention is to provide an ultrasonic diagnostic apparatus and program capable of displaying a good ultrasonic diagnostic image without causing an interpolation error or data distortion when converting a high acquisition sampling frequency to a low display-dependent sampling frequency. Is to provide.
  • the invention according to claim 1 is an ultrasonic diagnostic apparatus, An ultrasonic probe having a plurality of transducers for outputting a transmission signal by receiving a reflected ultrasonic wave from the subject and outputting a transmission ultrasonic wave toward the subject by a driving signal; A transmitter for supplying a drive signal to the vibrator; A reception unit that samples the reception signal obtained by the transducer at a preset acquisition sampling frequency, and obtains acquisition sampling data by phasing and adding the reception signal at each sampling point; A display unit for displaying an image; A control unit that thins out data from the acquired sampling data and down-samples to obtain a display-dependent sampling frequency set according to a display image size of the display unit; With The display unit displays an ultrasound diagnostic image based on the acquired sampling data down-sampled by the control unit.
  • the invention according to claim 2 is the ultrasonic diagnostic apparatus according to claim 1,
  • the control unit oversamples the acquired sampling data obtained by the receiving unit so as to be a least common multiple of the acquired sampling frequency and the display dependent sampling frequency, and then becomes the display dependent sampling frequency. It is characterized by downsampling.
  • Invention of Claim 3 is a program, Comprising: A computer provided in an ultrasonic diagnostic apparatus having a plurality of transducers that outputs a reception signal by receiving a reflected ultrasonic wave from a subject while outputting a transmission ultrasonic wave toward the subject by a drive signal, A function of acquiring the acquired sampling data of the received signal sampled at a preset acquisition sampling frequency and phased and added for each sampling point; A function of thinning down the data from the acquired sampling data and down-sampling so as to obtain a display-dependent sampling frequency set according to the display image size of the display unit that displays an ultrasound diagnostic image based on the acquired sampling data; , A function of outputting the downsampled acquired sampling data; It is characterized by realizing.
  • FIG. 1 It is a figure which shows the external appearance structure of the ultrasound diagnosing device in embodiment of this invention. It is a block diagram which shows schematic structure of an ultrasound diagnosing device. It is a flowchart explaining a sampling frequency setting process. It is a flowchart explaining a sampling frequency conversion process. It is a figure explaining the reception timing of the reflected ultrasonic wave in a vibrator
  • the ultrasonic diagnostic apparatus S transmits ultrasonic waves (transmission ultrasonic waves) to a subject such as a living body (not shown), and this subject.
  • the ultrasonic probe 2 that receives the reflected wave of reflected ultrasonic waves (reflected ultrasonic wave: echo) is connected to the ultrasonic probe 2 via the cable 3 and an electric signal is sent to the ultrasonic probe 2.
  • the ultrasonic probe 2 transmits the transmission ultrasonic wave to the subject, and in response to the reflected ultrasonic wave from the subject received by the ultrasonic probe 2.
  • An ultrasonic diagnostic apparatus main body 1 that images the internal state of the subject as an ultrasonic image based on a reception signal that is an electrical signal generated by the ultrasonic probe 2 is configured.
  • the ultrasonic probe 2 includes a transducer 2a made of a piezoelectric element. As shown in FIG. 5, a plurality of transducers 2a are arranged in a one-dimensional array in the azimuth direction (scanning direction or vertical direction). Has been. In the present embodiment, the ultrasonic probe 2 including n (for example, 128) transducers 2a is used. Note that the vibrators 2a may be arranged in a two-dimensional array. The number of vibrators 2a can be set arbitrarily. Further, in the present embodiment, the ultrasonic probe 2 that performs the linear scanning method is applied, but the one that performs the sector scanning method or the one that performs the convex scanning method may be applied.
  • the ultrasonic diagnostic apparatus body 1 includes an operation input unit 11, a transmission unit 12, a reception unit 13, an image generation unit 14, a memory unit 15, and a DSC (Digital Scan Converter). 16, a display unit 17, and a control unit 18.
  • an operation input unit 11 a transmission unit 12, a reception unit 13, an image generation unit 14, a memory unit 15, and a DSC (Digital Scan Converter).
  • a display unit 17 a control unit 18.
  • DSC Digital Scan Converter
  • the operation input unit 11 includes, for example, various switches, buttons, a trackball, a mouse, a keyboard, and the like for inputting data such as a command to start diagnosis and personal information of a subject, and the like. Output to the control unit 18.
  • the transmission unit 12 is a circuit that supplies a drive signal, which is an electrical signal, to the ultrasonic probe 2 via the cable 3 under the control of the control unit 18 to generate transmission ultrasonic waves in the ultrasonic probe 2. .
  • the transmission unit 12 includes, for example, a clock generation circuit, a delay circuit, and a pulse generation circuit.
  • the clock generation circuit is a circuit that generates a clock signal that determines the transmission timing and transmission frequency of the drive signal.
  • the delay circuit sets a transmission signal transmission timing for each individual path corresponding to each transducer 2a, delays transmission of the drive signal by the set delay time, and is a transmission beam constituted by transmission ultrasonic waves. This is a circuit for performing focusing.
  • the pulse generation circuit is a circuit for generating a pulse signal as a drive signal at a predetermined cycle.
  • the receiving unit 13 is a circuit that receives a reception signal of an electrical signal from the ultrasonic probe 2 via the cable 3 under the control of the control unit 18.
  • the frequency of the reception signal received by the reception unit 13 is 15 MHz, for example, but varies depending on the frequency of the pulse signal generated by the transmission unit 12.
  • the receiving unit 13 includes, for example, an amplifier, an A / D conversion circuit, and a phasing addition circuit.
  • the amplifier is a circuit for amplifying the received signal with a predetermined amplification factor set in advance for each individual path corresponding to each transducer 2a.
  • the A / D conversion circuit is a circuit for sampling the amplified received signal at a predetermined sampling frequency and performing A / D conversion.
  • the phasing addition circuit adjusts the time phase by giving a delay time to each individual path corresponding to each transducer 2a with respect to the A / D converted received signal, and adds these (phasing addition) to generate a sound. It is a circuit for generating line data.
  • the receiving unit 13 includes a memory (not shown) that temporarily stores sound ray data generated by the phasing addition circuit.
  • the image generation unit 14 performs logarithmic amplification, envelope detection processing, and the like on the sound ray data from the reception unit 13 to generate B-mode image data.
  • the B-mode image data generated in this way is transmitted to the memory unit 15.
  • the memory unit 15 is configured by a semiconductor memory such as DRAM (Dynamic Random Access Memory), for example, and stores the B-mode image data transmitted from the image generation unit 14 in units of frames. That is, it can be stored as frame image data.
  • the stored frame image data is transmitted to the DSC 16 under the control of the control unit 18.
  • the DSC 16 converts the frame image data received from the memory unit 15 into an image signal based on a television signal scanning method, and outputs the image signal to the display unit 17.
  • the display unit 17 is a display device such as an LCD (Liquid Crystal Display), a CRT (Cathode-Ray Tube) display, an organic EL (Electronic Luminescence) display, and a plasma display.
  • the display unit 17 displays an image on the display screen according to the image signal output from the DSC 16.
  • the control unit 18 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and reads various processing programs such as a system program stored in the ROM to read the RAM.
  • the operation of each part of the ultrasonic diagnostic apparatus S is centrally controlled according to the developed program.
  • the ROM is composed of a nonvolatile memory such as a semiconductor, and is a system program corresponding to the ultrasonic diagnostic apparatus S and various processing programs such as a sampling frequency setting process and a sampling frequency conversion process, which will be described later, which can be executed on the system program. And various data.
  • These programs are stored in the form of computer-readable program code, and the CPU sequentially executes operations according to the program code.
  • the RAM forms a work area for temporarily storing various programs executed by the CPU and data related to these programs.
  • sampling frequency setting process executed in the ultrasonic diagnostic apparatus S configured as described above will be described with reference to FIG.
  • This sampling frequency setting process is, for example, a process executed when the power is turned on or when a setting operation is performed by the operation input unit 11.
  • the control unit 18 sets a display dependent sampling frequency (Fsd) that matches the display size of the display unit 17 (step S101).
  • the setting of the display-dependent sampling frequency is performed by referring to a predetermined table and selecting a corresponding sampling frequency from the display size information output from the display unit 17, for example.
  • an image having a maximum display size of 1000 dots is displayed on the display unit 17 and an image that is about four times the display image size is taken into consideration in order to implement a zoom function for enlarging a part of the portion.
  • the display dependent sampling frequency is set to 60 MHz.
  • the setting of the display dependent sampling frequency may be arbitrarily selected by the user.
  • the control unit 18 sets the acquisition sampling frequency (Fss) according to the signal frequency to be extracted (step S102), and then ends this process.
  • This acquired sampling frequency is preferably set to a relatively high frequency in order to improve the S / N in the data after phasing addition, for example, and is set to 200 MHz in the present embodiment.
  • the receiving unit 13 samples the 15 MHz reception signal at a sampling frequency of 200 MHz, and performs phasing addition at this data rate.
  • the sampling data acquired as a result is referred to as acquired sampling data.
  • the acquired sampling frequency may be determined in advance, or may be arbitrarily selected by the user.
  • This sampling frequency conversion process is a process that is executed, for example, every time the received signal sampled by the receiving unit 14 is phased and added to generate sound ray data.
  • the control unit 18 sets a sampling frequency (Fso) that is the least common multiple of the acquisition sampling frequency (Fss) and the display dependent sampling frequency (Fsd), and the sampling data acquired at the acquisition sampling frequency (Fss) Oversampling is performed by inserting zero data (zero padding) so that the set sampling frequency (Fso) is obtained (step S201).
  • the sampling frequency (Fso) that is the least common multiple is set to 600 MHz. Then, by inserting two pieces of zero data between each piece of acquired sampling data, the acquired sampling data with a sampling frequency of 200 MHz is oversampled to 600 MHz.
  • the control unit 18 performs a band limiting filter (BPF (Band-Pass Filter) or LPF (Low-Pass Filter)) process on the oversampled acquired sampling data (Step S202). Specifically, it is realized by applying a band-limiting filter about half the display-dependent sampling frequency (Fsd) to the oversampled acquired sampling data.
  • a 28 MHz LPF (Low-Pass Filter) which is a frequency slightly lower than half of the display dependent sampling frequency (Fsd) is applied in order to provide a margin.
  • control unit 18 performs gain adjustment (step S203). Specifically, the control unit 18 adjusts the acquired sampling data so as to obtain a gain by applying a coefficient corresponding to an oversampled multiple.
  • control unit 18 performs data decimation (decimation processing) so as to obtain the display-dependent sampling frequency (Fsd) from the acquired sampling data oversampled to the sampling frequency (Fso) (step S204). . Specifically, the control unit 18 obtains sampling data with a sampling frequency of 60 MHz by thinning out the acquired sampling data oversampled to a sampling frequency of 600 MHz so that it becomes 1/10.
  • control part 18 outputs the acquisition sampling data downsampled as mentioned above to the image generation part 14 (step S205).
  • image data without distortion can be obtained by generating image data as described above. The reason will be described with reference to the drawings.
  • n transducers 2 a are arranged in the azimuth direction (scanning direction) in the ultrasound probe 2.
  • the time until the reflected ultrasonic wave is received from the echo source E differs for each transducer.
  • the distance from the echo source E to the transducer 2a is 30 mm and the transducer pitch is 0.15 mm
  • the distance from the echo source E to the reception position of the transducer 2a arranged at the position “0” L0 is expressed by the following formula (1)
  • the distance L15 from the echo source E to the receiving position of the transducer 2a arranged at the position “15” is expressed by the following formula (2). Note that the distance indicated by LC in FIG.
  • the distance to the receiving position of the child 2a is 0.075 mm, which is half the pitch of the transducer 2a.
  • the amount of sampling timing deviation until the reflected ultrasonic wave from the echo source E is received is (L0-L15) / 1540 * 200 * 10 6 ⁇ 11.6 (3)
  • the reception signal acquired from the transducer 2a arranged at the position “0” is delayed by 12 samples from the reception signal obtained from the transducer 2a arranged at the position “15”.
  • a phasing addition is performed by adding to the data.
  • the sampling frequency of the received signal is as high as possible because good data can be obtained.
  • a sampling frequency of wavelength ( ⁇ ) / 8 or more it is said that it is preferable. This is because when the phasing addition is performed, the delay amount of the sample often does not become an integer ratio as shown in the above-described equation (3), and even if the delay processing is performed on the sampled data, This is because the waveforms are not necessarily matched and data is added, but for example, data shifted by one sample may be added.
  • FIG. 6 shows a case where data for one sample is shifted and phased. As shown in FIG. 6, at a sampling frequency of 60 MHz, only 4 points of sampling data can be obtained for one period. Then, when the sampling data phased in this way is added for each sampling point after phasing, the result is as shown in FIG.
  • FIG. 8 shows a case where data for one sample is similarly shifted and phased. As shown in FIG. 8, at a sampling frequency of 200 MHz, about 13 sampling data can be obtained for one period. Then, when the sampling data phased in this way is added for each sampling point after phasing, the result is as shown in FIG.
  • FIG. 10 data (original data) sampled at a sampling frequency of 60 MHz with respect to a reception signal composed of four 15 MHz sine waves, and the original data and data delayed by one sample from the original data are added.
  • the result of performing 1024-point fast Fourier transform (FFT) on the object is shown.
  • the original data is represented by a broken line, and the original data and a sum of data delayed by one sample from the original data are represented by a solid line.
  • FIG. 11 shows data (original data) sampled at a sampling frequency of 200 MHz with respect to a reception signal composed of four 15 MHz sine waves, and original data and data delayed by one sample from the original data.
  • the result of performing 1024-point fast Fourier transform (FFT) on the sum is shown.
  • the original data is represented by a broken line, and the original data and a sum of data delayed by one sample from the original data are represented by a solid line.
  • a transmission ultrasonic wave is output to an object at a distance of 50 mm from the transducer 2a, and then a reflected ultrasonic wave is output.
  • the number of data sampled until the reception of is completed as shown in the following formula (4).
  • the speed of the transmission ultrasonic wave and the reflected ultrasonic wave is 1540 m / s. 50 * 10 ⁇ 3 * 2/1540 * 200 * 10 6 ⁇ 12987 (4)
  • the display size of the LCD used for the display unit 17 has, for example, a standard as shown in FIG. Of the display size standards shown in FIG. 12, high-resolution LCDs such as SXGA and UGA are generally used most frequently.
  • the display capability of such an LCD is 1024 dots vertically for SXGA and 1200 dots vertically for UGA.
  • pixels of about 1000 dots are usually used for display. That is, when sampling is performed at a sampling frequency of 200 MHz, all the sampled data cannot be converted into an image and cannot be displayed. Therefore, in the example shown in the above formula (4), until about 1/12. It is necessary to thin out the sampled data.
  • the ultrasonic diagnostic apparatus in order to enlarge and display a part of the image, it is performed to hold image data about four times the display size. It is preferable to hold sampling data with a sampling frequency of 60 MHz.
  • the transmission ultrasonic wave is output to the object at a distance of 50 mm from the transducer 2a and then the reflected ultrasonic wave is output as in the above example.
  • the number of data sampled until the reception of the sound wave is completed is expressed by the following equation (5). 50 * 10 ⁇ 3 * 2/1540 * 60 * 10 6 ⁇ 3896 (5)
  • sampling data can be calculated as follows.
  • the sampling point with a sampling frequency of 60 MHz is located at positions a to c in the figure. That is, the sampling points a and b do not coincide with the sampling points at the sampling frequency of 200 MHz, and thus need to be calculated by interpolation processing.
  • the sampling data can be simply calculated by calculating by linear interpolation as follows.
  • the value (sampling value) which the sampling data in each sampling point by the sampling frequency of 200 MHz shows in FIG.
  • the sampling values at the sampling points “6” and “7” at the sampling frequency of 200 MHz are generated by linear interpolation. That is, as shown in FIG. 16, when the distance from the sampling point “6” to “7” at the sampling frequency of 200 MHz is 1, the sampling point b is 2/3 from the sampling point “6” at the sampling frequency of 200 MHz. Therefore, the sampling value at the sampling point b is as shown in the following formula (7). 0.707107 * 1/3 + 0.309017 * 2 / 3 ⁇ 0.4417137 (7)
  • FIG. 17 shows the result of sampling a 15 MHz received signal at a sampling frequency of 600 MHz.
  • sampling values are obtained by performing linear interpolation on sampling points a and b
  • these sampling values have errors when compared with values obtained by actual sampling. Recognize. That is, such an error becomes a waveform distortion or an interpolation error and is reflected in the image data as it is, which may cause an artifact.
  • THI that images waveform distortion that occurs during propagation of ultrasound waves is applied
  • such an error is directly imaged as an artifact.
  • a 15 MHz reception signal is sampled at a sampling frequency of 200 MHz, and phasing addition is performed to obtain a sampling result shown in FIG. 14, and then, as shown in FIG. Oversampling is performed by inserting two zeros between each piece of acquired sampling data so that the frequency becomes 600 MHz.
  • the BPF process is performed on the oversampled data, as shown in FIG. 19, a result almost same as the result obtained by actually sampling at the sampling frequency of 600 MHz is obtained.
  • the sampling data over-sampled as described above is thinned out to 1/10 and down-sampled so that the sampling frequency is 60 MHz, the result shown in FIG. 20 is obtained. . That is, the result is almost the same as the original data obtained by sampling the 15 MHz received signal at the sampling frequency of 60 MHz, and the data is highly accurate.
  • the ultrasonic probe 2 outputs a transmission ultrasonic wave toward the subject by the drive signal and receives a reflected ultrasonic wave from the subject. Accordingly, a plurality of vibrators 2a that output reception signals are provided. Then, the transmission unit 12 supplies a drive signal to the vibrator 2a. Then, the reception unit 13 samples the reception signal obtained by the transducer 2a at a preset acquisition sampling frequency. Then, the receiving unit 13 obtains acquired sampling data by phasing and adding the received signals for each sampling point. Then, the display unit 17 displays an ultrasound diagnostic image based on the acquired sampling data.
  • the control unit 18 performs downsampling by thinning out the data from the acquired sampling data so that the display-dependent sampling frequency set according to the display image size of the display unit 17 is obtained.
  • the display unit 17 displays an ultrasound diagnostic image based on the acquired sampling data downsampled by the control unit 18.
  • control unit 18 after oversampling the acquired sampling data obtained by the receiving unit 13 so as to be the least common multiple of the acquired sampling frequency and the display dependent sampling frequency, Downsampling to a display-dependent sampling frequency.
  • generation of interpolation data associated with downsampling becomes unnecessary, generation of artifacts due to interpolation errors caused by generating interpolation data can be suppressed, and highly accurate image data can be generated.
  • the description in the embodiment of the present invention is an example of the ultrasonic diagnostic apparatus according to the present invention, and the present invention is not limited to this.
  • the detailed configuration and detailed operation of each functional unit constituting the ultrasonic diagnostic apparatus can be appropriately changed.
  • the sampling frequency which is the least common multiple of the acquisition sampling frequency and the display dependent sampling frequency is set and oversampling is performed on the acquired sampling data.
  • the frequency is an integral multiple of the frequency, the oversampling process is not necessary.
  • the oversampling process and the downsampling process are realized by software processing by the control unit, but may be realized by hardware.
  • the oversampling process is performed by inserting zero data between the sampling data.
  • the oversampling process may be performed by another method.
  • the downsampling process is performed by thinning out the sampling data.
  • the downsampling process may be performed by other methods.
  • a hard disk, a semiconductor nonvolatile memory, or the like is used as a computer-readable medium of the program according to the present invention, but the present invention is not limited to this example.
  • a portable recording medium such as a CD-ROM can be applied.
  • a carrier wave is also used as a medium for providing program data according to the present invention via a communication line.

Abstract

Provided are an ultrasound diagnosis device and a program which can display good ultrasound diagnosis images. A reception unit (13) subjects a received signal obtained by means of an oscillator (2a) to sampling at a preset acquisition sampling frequency. The reception unit (13) then subjects the received signal to phasing addition at each sampling point and thereby obtains acquisition sampling data. A display unit (17) then displays an image. A control unit (18) then performs downsampling by removing data from the acquisition sampling data in such a way that a display dependent sampling frequency, which is set in accordance with the display image size of the display unit (17), is met. The display unit (17) then displays an ultrasound diagnosis image on the basis of the acquisition sampling data that has been subjected to downsampling by the control unit (18).

Description

超音波診断装置及びプログラムUltrasonic diagnostic apparatus and program
　本発明は、超音波診断装置及びプログラムに関する。 The present invention relates to an ultrasonic diagnostic apparatus and a program.
　従来、多数の振動子（トランスデューサ）を一次元又は二次元状に配列して備える振動探触子（プローブ）を有し、生体等の被検体に対して超音波の送受信を行い、受信した超音波を電気信号に変換してこれをサンプリングし、サンプリングして得られたデータについて整相加算を行い、その結果得られたデータに基づいて超音波画像を生成し、これを画像表示装置に表示する超音波診断装置が知られている。 Conventionally, it has a vibration probe (probe) provided with a large number of transducers (transducers) arranged in a one-dimensional or two-dimensional form, and transmits and receives ultrasonic waves to and from a subject such as a living body. Converts sound waves into electrical signals, samples them, performs phasing addition on the data obtained by sampling, generates an ultrasonic image based on the data obtained as a result, and displays this on the image display device There are known ultrasonic diagnostic apparatuses.
　このような超音波診断装置においては、正確な診断を可能にするべく、良好な画像を得るために様々な工夫がなされている。 Such an ultrasonic diagnostic apparatus has been devised in various ways to obtain a good image in order to enable accurate diagnosis.
　例えば、受信線の位置からずれた線位置の２つの補間線を、受信線位置から走査線までの間隔に比例して受信線からのデータを重み付けし、重み付けしたデータを結合して補間線を得、これに基づいて超音波画像を表示するものがある（例えば、特許文献１）。 For example, two interpolation lines at a line position shifted from the position of the reception line are weighted with data from the reception line in proportion to the interval from the reception line position to the scanning line, and the weighted data is combined to form the interpolation line. There are some which display an ultrasonic image based on this (for example, patent documents 1).
　また、診断部位からフレーム単位のエコー信号を、所定のサンプリングクロックでサンプリングして画像メモリに取り込む際、全体画像については、１／Ｎに間引きしたサンプリングクロックで第１の画像メモリに取り込み、拡大画像については、関心領域を指示するウィンドウ信号で、所定のサンプリングクロックをゲートして、第２の画像メモリに取り込み、それぞれの画像を同じフレームレートで表示するものがある（例えば、特許文献２）。 Further, when an echo signal in units of frames is sampled from a diagnostic region with a predetermined sampling clock and taken into the image memory, the whole image is taken into the first image memory with a sampling clock thinned to 1 / N, and an enlarged image is obtained. Is a window signal indicating a region of interest, which is gated with a predetermined sampling clock, fetched into a second image memory, and displays each image at the same frame rate (for example, Patent Document 2).
特開平１０－２９０８０１号公報JP-A-10-290801 特開平６－１０３３６４号公報JP-A-6-103364
　ところで、受信信号のサンプリングは、できるだけ細かいピッチで行った方が、整相加算後のＳ／Ｎ（Signal-Noise ratio）の向上や、サンプリングしたデータに基づいて波形を再現したときの再現性が忠実なものとなるので、サンプリング周波数が高い方が良好な画像を生成することができる。
　しかしながら、画像表示装置の解像度は、縦１０００ドット程度なので、画像表示行っている限りは、サンプリングした信号の全てについて画像表示に反映することはできず、表示画素数に変換する処理（画素数変換処理）を行ってデータを表示可能なサイズまで、データ量を縮小する必要があった。
　この画素数変換処理は、多くの場合、原理的に波形歪みや補間誤差を発生させるので、サンプリング周波数を高くして整相加算を行って波形再現性を向上させても、この画素数変換処理により波形歪みや補間誤差が発生してしまい、アーチファクトの原因となっていた。
　特に近年は、超音波の生体伝搬中に発生する非線形歪みを画像化するＴＨＩ（Tissue Harmonic Imaging：組織ハーモニックイメージング法）がよく用いられているが、生体伝搬で発生する微小な歪みを抽出して画像化するＴＨＩでは、この画素数変換処理で生じる波形歪みの影響が特にアーチファクトの要因となり、画像品質が低下する大きな要因となっている。
　そして、上記特許文献１に記載の技術にあっても、画素数変換処理を行った際の波形の歪みを抑制することはできず、また、上記特許文献２に記載の技術であっても、このような波形歪みが考慮されて間引きするものではないので、波形歪みによる画質低下を抑制できるものではない。 By the way, if the received signal is sampled at as fine a pitch as possible, the S / N (Signal-Noise ratio) after phasing addition is improved and the reproducibility when the waveform is reproduced based on the sampled data. Since it becomes faithful, a higher sampling frequency can generate a better image.
However, since the resolution of the image display device is about 1000 dots vertically, as long as image display is being performed, all of the sampled signals cannot be reflected in the image display, and the process of converting the number of display pixels (pixel number conversion) It was necessary to reduce the amount of data to a size that allows data to be displayed after processing.
In many cases, this pixel number conversion process generates waveform distortion and interpolation error in principle. Therefore, even if the sampling frequency is increased and phasing addition is performed to improve waveform reproducibility, this pixel number conversion process is performed. As a result, waveform distortion and interpolation error occur, causing artifacts.
In recent years, THI (Tissue Harmonic Imaging) that images nonlinear distortion that occurs during propagation of ultrasonic waves is often used. In the THI to be imaged, the influence of the waveform distortion caused by the pixel number conversion processing becomes a factor of artifacts in particular, and is a major factor of reducing the image quality.
And even in the technique described in Patent Document 1, it is not possible to suppress waveform distortion when performing the pixel number conversion process, and even in the technique described in Patent Document 2, Since such waveform distortion is not taken into consideration and thinning out, it is not possible to suppress deterioration in image quality due to waveform distortion.
　本発明の課題は、高い取得サンプリング周波数を低い表示依存サンプリング周波数に変換する際に補間誤差やデータ歪みが発生せず、良好な超音波診断画像を表示することができる超音波診断装置及びプログラムを提供することである。 An object of the present invention is to provide an ultrasonic diagnostic apparatus and program capable of displaying a good ultrasonic diagnostic image without causing an interpolation error or data distortion when converting a high acquisition sampling frequency to a low display-dependent sampling frequency. Is to provide.
　以上の課題を解決するため、請求項１に記載の発明は、超音波診断装置において、
　駆動信号によって被検体に向けて送信超音波を出力するとともに、被検体からの反射超音波を受信することにより受信信号を出力する複数の振動子を有する超音波探触子と、
　前記振動子に駆動信号を供給する送信部と、
　前記振動子によって得られた受信信号を予め設定された取得サンプリング周波数にてサンプリングし、該サンプリング点毎に前記受信信号を整相加算して取得サンプリングデータを得る受信部と、
　画像の表示を行う表示部と、
　前記表示部の表示画像サイズに応じて設定された表示依存サンプリング周波数となるように前記取得サンプリングデータからデータを間引いてダウンサンプリングする制御部と、
　を備え、
　前記表示部は、前記制御部によってダウンサンプリングされた前記取得サンプリングデータに基づいて超音波診断画像を表示することを特徴とする。 In order to solve the above problems, the invention according to claim 1 is an ultrasonic diagnostic apparatus,
An ultrasonic probe having a plurality of transducers for outputting a transmission signal by receiving a reflected ultrasonic wave from the subject and outputting a transmission ultrasonic wave toward the subject by a driving signal;
A transmitter for supplying a drive signal to the vibrator;
A reception unit that samples the reception signal obtained by the transducer at a preset acquisition sampling frequency, and obtains acquisition sampling data by phasing and adding the reception signal at each sampling point;
A display unit for displaying an image;
A control unit that thins out data from the acquired sampling data and down-samples to obtain a display-dependent sampling frequency set according to a display image size of the display unit;
With
The display unit displays an ultrasound diagnostic image based on the acquired sampling data down-sampled by the control unit.
　請求項２に記載の発明は、請求項１に記載の超音波診断装置において、
　前記制御部は、前記受信部によって得られた前記取得サンプリングデータを、前記取得サンプリング周波数と前記表示依存サンプリング周波数との最小公倍数となるようにオーバーサンプリングした後、前記表示依存サンプリング周波数となるようにダウンサンプリングすることを特徴とする。 The invention according to claim 2 is the ultrasonic diagnostic apparatus according to claim 1,
The control unit oversamples the acquired sampling data obtained by the receiving unit so as to be a least common multiple of the acquired sampling frequency and the display dependent sampling frequency, and then becomes the display dependent sampling frequency. It is characterized by downsampling.
　請求項３に記載の発明は、プログラムであって、
　駆動信号によって被検体に向けて送信超音波を出力するとともに、被検体からの反射超音波を受信することにより受信信号を出力する複数の振動子を有する超音波診断装置に設けられたコンピュータに、
　予め設定された取得サンプリング周波数にてサンプリングされ、該サンプリング点毎に整相加算された前記受信信号の取得サンプリングデータを取得する機能と、
　前記取得サンプリングデータに基づいて超音波診断画像の表示を行う表示部の表示画像サイズに応じて設定された表示依存サンプリング周波数となるように、前記取得サンプリングデータからデータを間引いてダウンサンプリングする機能と、
　該ダウンサンプリングされた前記取得サンプリングデータを出力する機能と、
　を実現させることを特徴とする。 Invention of Claim 3 is a program, Comprising:
A computer provided in an ultrasonic diagnostic apparatus having a plurality of transducers that outputs a reception signal by receiving a reflected ultrasonic wave from a subject while outputting a transmission ultrasonic wave toward the subject by a drive signal,
A function of acquiring the acquired sampling data of the received signal sampled at a preset acquisition sampling frequency and phased and added for each sampling point;
A function of thinning down the data from the acquired sampling data and down-sampling so as to obtain a display-dependent sampling frequency set according to the display image size of the display unit that displays an ultrasound diagnostic image based on the acquired sampling data; ,
A function of outputting the downsampled acquired sampling data;
It is characterized by realizing.
　本発明によれば、高い取得サンプリング周波数を低い表示依存サンプリング周波数に変換する際に補間誤差やデータ歪みが発生せず、良好な超音波診断画像を表示することができる。 According to the present invention, when converting a high acquisition sampling frequency to a low display-dependent sampling frequency, an interpolation error or data distortion does not occur, and a good ultrasonic diagnostic image can be displayed.
本発明の実施の形態における超音波診断装置の外観構成を示す図である。It is a figure which shows the external appearance structure of the ultrasound diagnosing device in embodiment of this invention. 超音波診断装置の概略構成を示すブロック図である。It is a block diagram which shows schematic structure of an ultrasound diagnosing device. サンプリング周波数設定処理について説明するフローチャートである。It is a flowchart explaining a sampling frequency setting process. サンプリング周波数変換処理について説明するフローチャートである。It is a flowchart explaining a sampling frequency conversion process. 振動子における反射超音波の受信タイミングについて説明する図である。It is a figure explaining the reception timing of the reflected ultrasonic wave in a vibrator | oscillator. 整相後のサンプリング結果について説明する図である。It is a figure explaining the sampling result after phasing. 整相加算後のサンプリング結果について説明する図である。It is a figure explaining the sampling result after phasing addition. 整相後のサンプリング結果について説明する図である。It is a figure explaining the sampling result after phasing. 整相加算後のサンプリング結果について説明する図である。It is a figure explaining the sampling result after phasing addition. 整相加算後のサンプリング結果について説明する図である。It is a figure explaining the sampling result after phasing addition. 整相加算後のサンプリング結果について説明する図である。It is a figure explaining the sampling result after phasing addition. ＬＣＤの表示サイズについて説明する図である。It is a figure explaining the display size of LCD. サンプリングデータの間引き方法について説明する図である。It is a figure explaining the thinning-out method of sampling data. サンプリング値を示す図である。It is a figure which shows a sampling value. 補間処理によるサンプリングデータの生成について説明する図である。It is a figure explaining the production | generation of the sampling data by an interpolation process. 補間処理によるサンプリングデータの生成について説明する図である。It is a figure explaining the production | generation of the sampling data by an interpolation process. サンプリング値を示す図である。It is a figure which shows a sampling value. オーバーサンプリングの方法について説明する図である。It is a figure explaining the method of oversampling. オーバーサンプリングした結果について説明する図である。It is a figure explaining the result of oversampling. ダウンサンプリングした結果について説明する図である。It is a figure explaining the result of downsampling.
　以下、本発明の実施の形態に係る超音波診断装置について、図面を参照して説明する。ただし、発明の範囲は図示例に限定されない。なお、以下の説明において、同一の機能及び構成を有するものについては、同一の符号を付し、その説明を省略する。 Hereinafter, an ultrasonic diagnostic apparatus according to an embodiment of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples. In addition, in the following description, what has the same function and structure attaches | subjects the same code | symbol, and abbreviate | omits the description.
　本発明の実施の形態に係る超音波診断装置Ｓは、図１及び図２に示すように、図示しない生体等の被検体に対して超音波（送信超音波）を送信するとともに、この被検体で反射した超音波の反射波（反射超音波：エコー）を受信する超音波探触子２と、超音波探触子２とケーブル３を介して接続され、超音波探触子２に電気信号の駆動信号を送信することによって超音波探触子２に被検体に対して送信超音波を送信させるとともに、超音波探触子２にて受信された被検体内からの反射超音波に応じて超音波探触子２で生成された電気信号である受信信号に基づいて被検体内の内部状態を超音波画像として画像化する超音波診断装置本体１とを備えて構成している。 As shown in FIGS. 1 and 2, the ultrasonic diagnostic apparatus S according to the embodiment of the present invention transmits ultrasonic waves (transmission ultrasonic waves) to a subject such as a living body (not shown), and this subject. The ultrasonic probe 2 that receives the reflected wave of reflected ultrasonic waves (reflected ultrasonic wave: echo) is connected to the ultrasonic probe 2 via the cable 3 and an electric signal is sent to the ultrasonic probe 2. By transmitting the driving signal, the ultrasonic probe 2 transmits the transmission ultrasonic wave to the subject, and in response to the reflected ultrasonic wave from the subject received by the ultrasonic probe 2. An ultrasonic diagnostic apparatus main body 1 that images the internal state of the subject as an ultrasonic image based on a reception signal that is an electrical signal generated by the ultrasonic probe 2 is configured.
　超音波探触子２は、圧電素子からなる振動子２ａを備えており、この振動子２ａは、図５に示すように、方位方向（走査方向あるいは上下方向）に一次元アレイ状に複数配列されている。本実施の形態では、ｎ個（例えば、１２８個）の振動子２ａを備えた超音波探触子２を用いている。なお、振動子２ａは、二次元アレイ状に配列されたものであってもよい。また、振動子２ａの個数は、任意に設定することができる。また、本実施の形態では、超音波探触子２について、リニア走査方式を行うものを適用したが、セクタ走査方式を行うものやコンベックス走査方式を行うものを適用してもよい。 The ultrasonic probe 2 includes a transducer 2a made of a piezoelectric element. As shown in FIG. 5, a plurality of transducers 2a are arranged in a one-dimensional array in the azimuth direction (scanning direction or vertical direction). Has been. In the present embodiment, the ultrasonic probe 2 including n (for example, 128) transducers 2a is used. Note that the vibrators 2a may be arranged in a two-dimensional array. The number of vibrators 2a can be set arbitrarily. Further, in the present embodiment, the ultrasonic probe 2 that performs the linear scanning method is applied, but the one that performs the sector scanning method or the one that performs the convex scanning method may be applied.
　超音波診断装置本体１は、例えば、図２に示すように、操作入力部１１と、送信部１２と、受信部１３と、画像生成部１４と、メモリ部１５と、ＤＳＣ（Digital Scan Converter）１６と、表示部１７と、制御部１８とを備えて構成されている。 For example, as shown in FIG. 2, the ultrasonic diagnostic apparatus body 1 includes an operation input unit 11, a transmission unit 12, a reception unit 13, an image generation unit 14, a memory unit 15, and a DSC (Digital Scan Converter). 16, a display unit 17, and a control unit 18.
　操作入力部１１は、例えば、診断開始を指示するコマンドや被検体の個人情報等のデータの入力などを行うための各種スイッチ、ボタン、トラックボール、マウス、キーボード等を備えており、操作信号を制御部１８に出力する。 The operation input unit 11 includes, for example, various switches, buttons, a trackball, a mouse, a keyboard, and the like for inputting data such as a command to start diagnosis and personal information of a subject, and the like. Output to the control unit 18.
　送信部１２は、制御部１８の制御に従って、超音波探触子２にケーブル３を介して電気信号である駆動信号を供給して超音波探触子２に送信超音波を発生させる回路である。また、送信部１２は、例えば、クロック発生回路、遅延回路、パルス発生回路を備えている。クロック発生回路は、駆動信号の送信タイミングや送信周波数を決定するクロック信号を発生させる回路である。遅延回路は、駆動信号の送信タイミングを振動子２ａ毎に対応した個別経路毎に遅延時間を設定し、設定された遅延時間だけ駆動信号の送信を遅延させて送信超音波によって構成される送信ビームの集束を行うための回路である。パルス発生回路は、所定の周期で駆動信号としてのパルス信号を発生させるための回路である。 The transmission unit 12 is a circuit that supplies a drive signal, which is an electrical signal, to the ultrasonic probe 2 via the cable 3 under the control of the control unit 18 to generate transmission ultrasonic waves in the ultrasonic probe 2. . The transmission unit 12 includes, for example, a clock generation circuit, a delay circuit, and a pulse generation circuit. The clock generation circuit is a circuit that generates a clock signal that determines the transmission timing and transmission frequency of the drive signal. The delay circuit sets a transmission signal transmission timing for each individual path corresponding to each transducer 2a, delays transmission of the drive signal by the set delay time, and is a transmission beam constituted by transmission ultrasonic waves. This is a circuit for performing focusing. The pulse generation circuit is a circuit for generating a pulse signal as a drive signal at a predetermined cycle.
　受信部１３は、制御部１８の制御に従って、超音波探触子２からケーブル３を介して電気信号の受信信号を受信する回路である。なお、受信部１３が受信する受信信号の周波数は、例えば、１５ＭＨｚであるが、送信部１２によって発生するパルス信号の周波数等によって変動する。受信部１３は、例えば、増幅器、Ａ／Ｄ変換回路、整相加算回路を備えている。増幅器は、受信信号を、振動子２ａ毎に対応した個別経路毎に、予め設定された所定の増幅率で増幅させるための回路である。Ａ／Ｄ変換回路は、増幅された受信信号を所定のサンプリング周波数でサンプリングを行い、Ａ／Ｄ変換するための回路である。整相加算回路は、Ａ／Ｄ変換された受信信号に対して、振動子２ａ毎に対応した個別経路毎に遅延時間を与えて時相を整え、これらを加算（整相加算）して音線データを生成するための回路である。なお、受信部１３は、整相加算回路によって生成された音線データを一時的に保存する図示しないメモリを備えている。 The receiving unit 13 is a circuit that receives a reception signal of an electrical signal from the ultrasonic probe 2 via the cable 3 under the control of the control unit 18. The frequency of the reception signal received by the reception unit 13 is 15 MHz, for example, but varies depending on the frequency of the pulse signal generated by the transmission unit 12. The receiving unit 13 includes, for example, an amplifier, an A / D conversion circuit, and a phasing addition circuit. The amplifier is a circuit for amplifying the received signal with a predetermined amplification factor set in advance for each individual path corresponding to each transducer 2a. The A / D conversion circuit is a circuit for sampling the amplified received signal at a predetermined sampling frequency and performing A / D conversion. The phasing addition circuit adjusts the time phase by giving a delay time to each individual path corresponding to each transducer 2a with respect to the A / D converted received signal, and adds these (phasing addition) to generate a sound. It is a circuit for generating line data. The receiving unit 13 includes a memory (not shown) that temporarily stores sound ray data generated by the phasing addition circuit.
　画像生成部１４は、受信部１３からの音線データに対して対数増幅や包絡線検波処理などを実施し、Ｂモード画像データを生成する。このようにして生成されたＢモード画像データは、メモリ部１５に送信される。 The image generation unit 14 performs logarithmic amplification, envelope detection processing, and the like on the sound ray data from the reception unit 13 to generate B-mode image data. The B-mode image data generated in this way is transmitted to the memory unit 15.
　メモリ部１５は、例えば、ＤＲＡＭ（Dynamic Random Access Memory）などの半導体メモリによって構成されており、画像生成部１４から送信されたＢモード画像データをフレーム単位で記憶する。すなわち、フレーム画像データとして記憶することができる。そして、記憶されたフレーム画像データは、制御部１８の制御に従って、ＤＳＣ１６に送信される。 The memory unit 15 is configured by a semiconductor memory such as DRAM (Dynamic Random Access Memory), for example, and stores the B-mode image data transmitted from the image generation unit 14 in units of frames. That is, it can be stored as frame image data. The stored frame image data is transmitted to the DSC 16 under the control of the control unit 18.
　ＤＳＣ１６は、メモリ部１５より受信したフレーム画像データをテレビジョン信号の走査方式による画像信号に変換し、表示部１７に出力する。 The DSC 16 converts the frame image data received from the memory unit 15 into an image signal based on a television signal scanning method, and outputs the image signal to the display unit 17.
　表示部１７は、ＬＣＤ（Liquid Crystal Display）、ＣＲＴ（Cathode-Ray Tube）ディスプレイ、有機ＥＬ（Electronic Luminescence）ディスプレイ及びプラズマディスプレイ等の表示装置である。表示部１７は、ＤＳＣ１６から出力された画像信号に従って表示画面上に画像の表示を行う。 The display unit 17 is a display device such as an LCD (Liquid Crystal Display), a CRT (Cathode-Ray Tube) display, an organic EL (Electronic Luminescence) display, and a plasma display. The display unit 17 displays an image on the display screen according to the image signal output from the DSC 16.
　制御部１８は、例えば、ＣＰＵ（Central Processing Unit）、ＲＯＭ（Read Only Memory）、ＲＡＭ（Random Access Memory）を備えて構成され、ＲＯＭに記憶されているシステムプログラム等の各種処理プログラムを読み出してＲＡＭに展開し、展開したプログラムに従って超音波診断装置Ｓの各部の動作を集中制御する。
　ＲＯＭは、半導体等の不揮発メモリ等により構成され、超音波診断装置Ｓに対応するシステムプログラム及び該システムプログラム上で実行可能な、後述する、サンプリング周波数設定処理やサンプリング周波数変換処理等の各種処理プログラムや、各種データ等を記憶する。これらのプログラムは、コンピュータが読み取り可能なプログラムコードの形態で格納され、ＣＰＵは、当該プログラムコードに従った動作を逐次実行する。
　ＲＡＭは、ＣＰＵにより実行される各種プログラム及びこれらプログラムに係るデータを一時的に記憶するワークエリアを形成する。 The control unit 18 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and reads various processing programs such as a system program stored in the ROM to read the RAM. The operation of each part of the ultrasonic diagnostic apparatus S is centrally controlled according to the developed program.
The ROM is composed of a nonvolatile memory such as a semiconductor, and is a system program corresponding to the ultrasonic diagnostic apparatus S and various processing programs such as a sampling frequency setting process and a sampling frequency conversion process, which will be described later, which can be executed on the system program. And various data. These programs are stored in the form of computer-readable program code, and the CPU sequentially executes operations according to the program code.
The RAM forms a work area for temporarily storing various programs executed by the CPU and data related to these programs.
　次に、以上のようにして構成された超音波診断装置Ｓにおいて実行されるサンプリング周波数設定処理について図３を参照しながら説明する。このサンプリング周波数設定処理は、例えば、電源投入時や操作入力部１１による設定操作があったときに実行される処理である。 Next, a sampling frequency setting process executed in the ultrasonic diagnostic apparatus S configured as described above will be described with reference to FIG. This sampling frequency setting process is, for example, a process executed when the power is turned on or when a setting operation is performed by the operation input unit 11.
　先ず、制御部１８は、表示部１７の表示サイズに合わせた表示依存サンプリング周波数（Ｆｓｄ）の設定を行う（ステップＳ１０１）。
　この表示依存サンプリング周波数の設定は、例えば、表示部１７から出力される表示サイズ情報から、所定のテーブルを参照し、対応するサンプリング周波数を選択することにより行われる。本実施の形態では、表示部１７に最大縦１０００ドットの表示サイズの画像を表示するとともに、一部の部位を拡大するズーム機能を実施することを考慮し、表示画像サイズの４倍程度の画像データを持たせるため、６０ＭＨｚの表示依存サンプリング周波数に設定される。なお、表示依存サンプリング周波数の設定は、ユーザによって任意に選択できるようにしてもよい。 First, the control unit 18 sets a display dependent sampling frequency (Fsd) that matches the display size of the display unit 17 (step S101).
The setting of the display-dependent sampling frequency is performed by referring to a predetermined table and selecting a corresponding sampling frequency from the display size information output from the display unit 17, for example. In the present embodiment, an image having a maximum display size of 1000 dots is displayed on the display unit 17 and an image that is about four times the display image size is taken into consideration in order to implement a zoom function for enlarging a part of the portion. In order to have data, the display dependent sampling frequency is set to 60 MHz. The setting of the display dependent sampling frequency may be arbitrarily selected by the user.
　次に、制御部１８は、抽出しようとする信号周波数に合わせた取得サンプリング周波数（Ｆｓｓ）の設定を行った後（ステップＳ１０２）、この処理を終了する。
　この取得サンプリング周波数は、例えば、整相加算後のデータにおけるＳ／Ｎを向上させるために比較的高い周波数に設定されるのが好ましく、本実施の形態では、２００ＭＨｚに設定される。これにより、受信部１３では、１５ＭＨｚの受信信号を２００ＭＨｚのサンプリング周波数でサンプリングが行われ、このデータレートにて整相加算が行われることとなる。本実施の形態では、この結果取得されたサンプリングデータを取得サンプリングデータという。
　なお、この取得サンプリング周波数は、予め定められたものであってもよいし、ユーザによって任意に選択できるようにしてもよい。 Next, the control unit 18 sets the acquisition sampling frequency (Fss) according to the signal frequency to be extracted (step S102), and then ends this process.
This acquired sampling frequency is preferably set to a relatively high frequency in order to improve the S / N in the data after phasing addition, for example, and is set to 200 MHz in the present embodiment. As a result, the receiving unit 13 samples the 15 MHz reception signal at a sampling frequency of 200 MHz, and performs phasing addition at this data rate. In the present embodiment, the sampling data acquired as a result is referred to as acquired sampling data.
The acquired sampling frequency may be determined in advance, or may be arbitrarily selected by the user.
　次に、サンプリング周波数変換処理について図４を参照しながら説明する。このサンプリング周波数変換処理は、例えば、受信部１４によりサンプリングされた受信信号が整相加算されて音線データが生成される毎に実行される処理である。 Next, the sampling frequency conversion process will be described with reference to FIG. This sampling frequency conversion process is a process that is executed, for example, every time the received signal sampled by the receiving unit 14 is phased and added to generate sound ray data.
　先ず、制御部１８は、取得サンプリング周波数（Ｆｓｓ）と表示依存サンプリング周波数（Ｆｓｄ）との最小公倍数となるサンプリング周波数（Ｆｓｏ）を設定し、取得サンプリング周波数（Ｆｓｓ）にて取得したサンプリングデータが、設定したサンプリング周波数（Ｆｓｏ）となるようにゼロデータを挿入（ゼロパディング）してオーバーサンプリングを行う（ステップＳ２０１）。本実施の形態では、取得サンプリング周波数（Ｆｓｓ）が２００ＭＨｚ、表示依存サンプリング周波数（Ｆｓｄ）が６０ＭＨｚに設定されているので、最小公倍数となるサンプリング周波数（Ｆｓｏ）は、６００ＭＨｚに設定される。そして、取得サンプリングデータにおける各データ間にゼロデータを２個ずつ挿入することにより、サンプリング周波数が２００ＭＨｚの取得サンプリングデータが６００ＭＨｚにオーバーサンプリングされる。 First, the control unit 18 sets a sampling frequency (Fso) that is the least common multiple of the acquisition sampling frequency (Fss) and the display dependent sampling frequency (Fsd), and the sampling data acquired at the acquisition sampling frequency (Fss) Oversampling is performed by inserting zero data (zero padding) so that the set sampling frequency (Fso) is obtained (step S201). In the present embodiment, since the acquisition sampling frequency (Fss) is set to 200 MHz and the display dependent sampling frequency (Fsd) is set to 60 MHz, the sampling frequency (Fso) that is the least common multiple is set to 600 MHz. Then, by inserting two pieces of zero data between each piece of acquired sampling data, the acquired sampling data with a sampling frequency of 200 MHz is oversampled to 600 MHz.
　次に、制御部１８は、オーバーサンプリングした取得サンプリングデータに対して、帯域制限フィルタ（ＢＰＦ（Band-Pass Filter）又はＬＰＦ（Low-Pass Filter））処理を行う（ステップＳ２０２）。具体的には、オーバーサンプリングした取得サンプリングデータに対して、表示依存サンプリング周波数（Ｆｓｄ）の半分ほどの帯域制限フィルタをかけることにより実現される。本実施の形態では、余裕を持たせるため、表示依存サンプリング周波数（Ｆｓｄ）の半分よりも少し小さい周波数である２８ＭＨｚのＬＰＦ（Low-Pass Filter）をかけるようにしている。 Next, the control unit 18 performs a band limiting filter (BPF (Band-Pass Filter) or LPF (Low-Pass Filter)) process on the oversampled acquired sampling data (Step S202). Specifically, it is realized by applying a band-limiting filter about half the display-dependent sampling frequency (Fsd) to the oversampled acquired sampling data. In this embodiment, a 28 MHz LPF (Low-Pass Filter), which is a frequency slightly lower than half of the display dependent sampling frequency (Fsd), is applied in order to provide a margin.
　次に、制御部１８は、ゲイン調整を行う（ステップＳ２０３）。具体的には、制御部１８は、取得サンプリングデータに対し、オーバーサンプリングした倍数分の係数をかけることにより、ゲインが得られるように調整する。 Next, the control unit 18 performs gain adjustment (step S203). Specifically, the control unit 18 adjusts the acquired sampling data so as to obtain a gain by applying a coefficient corresponding to an oversampled multiple.
　次に、制御部１８は、サンプリング周波数（Ｆｓｏ）にオーバーサンプリングした取得サンプリングデータから、表示依存サンプリング周波数（Ｆｓｄ）となるようにデータの間引き（デシメーション処理）を行ってダウンサンプリングする（ステップＳ２０４）。具体的には、制御部１８は、サンプリング周波数６００ＭＨｚにオーバーサンプリングされた取得サンプリングデータについて１／１０となるようにデータを間引くことにより、サンプリング周波数が６０ＭＨｚとなるサンプリングデータを得る。 Next, the control unit 18 performs data decimation (decimation processing) so as to obtain the display-dependent sampling frequency (Fsd) from the acquired sampling data oversampled to the sampling frequency (Fso) (step S204). . Specifically, the control unit 18 obtains sampling data with a sampling frequency of 60 MHz by thinning out the acquired sampling data oversampled to a sampling frequency of 600 MHz so that it becomes 1/10.
　そして、制御部１８は、以上のようにしてダウンサンプリングされた取得サンプリングデータを画像生成部１４に出力する（ステップＳ２０５）。 And the control part 18 outputs the acquisition sampling data downsampled as mentioned above to the image generation part 14 (step S205).
　本実施の形態では、以上のようにして画像データの生成を行うことで、歪みのない画像データを得ることができるようになる。その理由を図面を参照しながら説明する。 In the present embodiment, image data without distortion can be obtained by generating image data as described above. The reason will be described with reference to the drawings.
　図５に示すように、超音波探触子２にはｎ個の振動子２ａが方位方向（走査方向）に配列されている。そして、エコー源Ｅから反射超音波を受信するまでの時間は振動子毎に異なる。例えば、エコー源Ｅから振動子２ａまでの距離を３０ｍｍとし、振動子のピッチを０．１５ｍｍとしたとき、エコー源Ｅから「０」の位置に配置された振動子２ａの受信位置までの距離Ｌ０は、下記式（１）となり、エコー源Ｅから「１５」の位置に配置された振動子２ａの受信位置までの距離Ｌ１５は、下記式（２）となる。なお、図５中ＬＣにて示される距離は、エコー源Ｅに対向する基準位置Ｓから「１５」の位置に配置された振動子２ａの受信位置までの距離である。基準位置Ｓは、「１５」の位置に配置された振動子２ａと「１６」の位置に配置された振動子２ａの中間に位置し、基準位置Ｓから「１５」の位置に配置された振動子２ａの受信位置までの距離は、振動子２ａのピッチの半分の０．０７５ｍｍとなる。
Figure JPOXMLDOC01-appb-M000001
 As shown in FIG. 5, n transducers 2 a are arranged in the azimuth direction (scanning direction) in the ultrasound probe 2. The time until the reflected ultrasonic wave is received from the echo source E differs for each transducer. For example, when the distance from the echo source E to the transducer 2a is 30 mm and the transducer pitch is 0.15 mm, the distance from the echo source E to the reception position of the transducer 2a arranged at the position “0” L0 is expressed by the following formula (1), and the distance L15 from the echo source E to the receiving position of the transducer 2a arranged at the position “15” is expressed by the following formula (2). Note that the distance indicated by LC in FIG. 5 is the distance from the reference position S facing the echo source E to the reception position of the transducer 2a arranged at the position “15”. The reference position S is located between the vibrator 2a arranged at the position “15” and the vibrator 2a arranged at the position “16”, and the vibration arranged from the reference position S to the position “15”. The distance to the receiving position of the child 2a is 0.075 mm, which is half the pitch of the transducer 2a.
Figure JPOXMLDOC01-appb-M000001
　以上の式より、反射超音波の速度が１５４０ｍ／ｓで、取得サンプリング周波数が２００ＭＨｚとすると、「０」の位置に配置された振動子２ａと、「１５」の位置に配置された振動子２ａとのエコー源Ｅからの反射超音波を受信するまでのサンプリングタイミングのずれ量は、
（Ｌ０－Ｌ１５）／１５４０＊２００＊１０６≒１１．６・・・（３）
で、およそ１２サンプル分となる。
　そして、このずれ量を考慮し、「０」の位置に配置された振動子２ａから取得した受信信号は、「１５」の位置に配置された振動子２ａから取得した受信信号を１２サンプル遅らせたデータに加算することで、整相加算を行うようにしている。 From the above formula, assuming that the reflected ultrasonic velocity is 1540 m / s and the acquisition sampling frequency is 200 MHz, the vibrator 2a arranged at the position “0” and the vibrator 2a arranged at the position “15”. The amount of sampling timing deviation until the reflected ultrasonic wave from the echo source E is received is
(L0-L15) / 1540 * 200 * 10 6 ≈11.6 (3)
Thus, there are about 12 samples.
In consideration of this shift amount, the reception signal acquired from the transducer 2a arranged at the position “0” is delayed by 12 samples from the reception signal obtained from the transducer 2a arranged at the position “15”. A phasing addition is performed by adding to the data.
　ここで、整数加算を行うときには、受信信号に対して、できるだけ、サンプリング周波数の高い方が良好なデータを得ることができるので好ましく、一般的には、波長（λ）／８以上のサンプリング周波数であるのが好ましいといわれている。これは、整相加算を行ったときに、上述した式（３）にて示されるように、サンプルの遅延量が整数比とならないことが多く、サンプリングしたデータについて遅延処理を行っても、必ずしも波形が一致してデータが加算されるとは限らず、例えば、１サンプル分ずれたデータが加算されることがあるという理由による。 Here, when performing integer addition, it is preferable that the sampling frequency of the received signal is as high as possible because good data can be obtained. Generally, at a sampling frequency of wavelength (λ) / 8 or more. It is said that it is preferable. This is because when the phasing addition is performed, the delay amount of the sample often does not become an integer ratio as shown in the above-described equation (3), and even if the delay processing is performed on the sampled data, This is because the waveforms are not necessarily matched and data is added, but for example, data shifted by one sample may be added.
　例えば、１５ＭＨｚの正弦波４波からなる受信信号に対して６０ＭＨｚのサンプリング周波数にてサンプリングした場合、図６に示すような波形によって表される。なお、図６では、１サンプル分データがずれて整相された場合を示している。図６に示すように、６０ＭＨｚのサンプリング周波数では、１周期に対して４点しかサンプリングデータを得ることができない。そして、このようにして整相されたサンプリングデータを、整相後のサンプリング点毎に加算すると、図７に示すようになる。 For example, when a received signal consisting of four 15 MHz sine waves is sampled at a sampling frequency of 60 MHz, it is represented by a waveform as shown in FIG. FIG. 6 shows a case where data for one sample is shifted and phased. As shown in FIG. 6, at a sampling frequency of 60 MHz, only 4 points of sampling data can be obtained for one period. Then, when the sampling data phased in this way is added for each sampling point after phasing, the result is as shown in FIG.
　一方、本実施の形態のように、１５ＭＨｚの正弦波４波からなる受信信号に対して２００ＭＨｚのサンプリング周波数にてサンプリングした場合、例えば、図８に示すような波形によって表される。なお、図８においても、同様に１サンプル分データがずれて整相された場合を示している。図８に示すように、２００ＭＨｚのサンプリング周波数では、１周期に対して約１３点のサンプリングデータを得ることができる。そして、このようにして整相されたサンプリングデータを、整相後の各サンプリング点毎に加算すると、図９に示すようになる。 On the other hand, when the received signal consisting of four 15 MHz sine waves is sampled at a sampling frequency of 200 MHz as in the present embodiment, for example, it is represented by a waveform as shown in FIG. FIG. 8 also shows a case where data for one sample is similarly shifted and phased. As shown in FIG. 8, at a sampling frequency of 200 MHz, about 13 sampling data can be obtained for one period. Then, when the sampling data phased in this way is added for each sampling point after phasing, the result is as shown in FIG.
　６０ＭＨｚのサンプリング周波数にてサンプリングした場合、整相加算後は、図７に示すように、波形が歪み、理想的なゲインの向上が認められないが、本実施の形態のように、２００ＭＨｚのサンプリング周波数にてサンプリングした場合、整相加算後は、図９に示すように、波形の変化はほとんど見られず、振幅がおよそ２倍にまで得られ、理想的なゲインの向上が認められるようになる。 When sampling is performed at a sampling frequency of 60 MHz, after phasing addition, the waveform is distorted and ideal gain improvement is not recognized as shown in FIG. 7, but 200 MHz sampling is performed as in this embodiment. When sampling is performed at a frequency, after phasing and adding, as shown in FIG. 9, there is almost no change in the waveform, the amplitude is obtained up to about twice, and an improvement in ideal gain is recognized. Become.
　次に、図７及び図９に示された結果を、図１０及び図１１を参照して説明する。
　図１０は、１５ＭＨｚの正弦波４波からなる受信信号に対して６０ＭＨｚのサンプリング周波数にてサンプリングしたデータ（オリジナルデータ）、及び、オリジナルデータとこのオリジナルデータから１サンプル分遅れたデータとを加算したものについて１０２４点の高速フーリエ変換（ＦＦＴ）を行った結果を表している。なお、図１０において、オリジナルデータを破線にて表し、オリジナルデータと、このオリジナルデータから１サンプル分遅れたデータとを加算したものを実線にて表している。
　また、図１１は、１５ＭＨｚの正弦波４波からなる受信信号に対して２００ＭＨｚのサンプリング周波数にてサンプリングしたデータ（オリジナルデータ）、及び、オリジナルデータとこのオリジナルデータから１サンプル分遅れたデータとを加算したものについて１０２４点の高速フーリエ変換（ＦＦＴ）を行った結果を表している。なお、図１１において、オリジナルデータを破線にて表し、オリジナルデータと、このオリジナルデータから１サンプル分遅れたデータとを加算したものを実線にて表している。 Next, the results shown in FIGS. 7 and 9 will be described with reference to FIGS.
In FIG. 10, data (original data) sampled at a sampling frequency of 60 MHz with respect to a reception signal composed of four 15 MHz sine waves, and the original data and data delayed by one sample from the original data are added. The result of performing 1024-point fast Fourier transform (FFT) on the object is shown. In FIG. 10, the original data is represented by a broken line, and the original data and a sum of data delayed by one sample from the original data are represented by a solid line.
FIG. 11 shows data (original data) sampled at a sampling frequency of 200 MHz with respect to a reception signal composed of four 15 MHz sine waves, and original data and data delayed by one sample from the original data. The result of performing 1024-point fast Fourier transform (FFT) on the sum is shown. In FIG. 11, the original data is represented by a broken line, and the original data and a sum of data delayed by one sample from the original data are represented by a solid line.
　図１０に示すように、６０ＭＨｚのサンプリング周波数にてサンプリングした場合には、１５ＭＨｚを示す２５６点目においては、オリジナルデータと比較して３ｄＢ程度しかゲインの向上が認められない。これに対して、２００ＭＨｚのサンプリング周波数にてサンプリングした場合には、１５ＭＨｚを示す７７点目においては、オリジナルデータと比較して６ｄＢ程度のゲインの向上が認められる。
　以上の結果から、整相加算を行う場合には、サンプリング周波数が高い方が大きなＳ／Ｎの向上が認められ、好ましいサンプリングデータを得ることができる。 As shown in FIG. 10, when sampling is performed at a sampling frequency of 60 MHz, gain improvement of only about 3 dB is recognized at the 256th point indicating 15 MHz as compared with the original data. On the other hand, when sampling is performed at a sampling frequency of 200 MHz, gain improvement of about 6 dB is recognized at the 77th point indicating 15 MHz as compared with the original data.
From the above results, when performing phasing addition, a higher S / N ratio is recognized when the sampling frequency is higher, and preferable sampling data can be obtained.
　上述のようにして、１５ＭＨｚの受信信号を２００ＭＨｚのサンプリング周波数でサンプリングを行うようにした場合、例えば、振動子２ａから５０ｍｍの距離にある物体に対して送信超音波を出力した後、反射超音波の受信が完了するまでの間にサンプリングされるデータの数は下記式（４）の通りとなる。ここで、送信超音波及び反射超音波の速度は１５４０ｍ／ｓとする。
５０＊１０－３＊２／１５４０＊２００＊１０６≒１２９８７・・・（４） As described above, when a 15 MHz reception signal is sampled at a sampling frequency of 200 MHz, for example, a transmission ultrasonic wave is output to an object at a distance of 50 mm from the transducer 2a, and then a reflected ultrasonic wave is output. The number of data sampled until the reception of is completed as shown in the following formula (4). Here, the speed of the transmission ultrasonic wave and the reflected ultrasonic wave is 1540 m / s.
50 * 10 −3 * 2/1540 * 200 * 10 6 ≈12987 (4)
　これに対し、表示部１７に用いられるＬＣＤの表示サイズには、例えば、図１２に示されるような規格がある。図１２に示される表示サイズの規格のうち、ＳＸＧＡやＵＧＡといった高解像度のＬＣＤが一般に最も多く使用されている。このようなＬＣＤにおける表示能力は、ＳＸＧＡでは縦１０２４ドット、ＵＧＡでは縦１２００ドットとなっているが、超音波診断装置においては、通常、１０００ドット程度の画素が表示に使用される。
　すなわち、２００ＭＨｚのサンプリング周波数にてサンプリングした場合、サンプリングしたデータ全てについて画像に変換し、これを表示させることができないので、上記式（４）に示された例では、およそ１／１２となるまでサンプリングしたデータを間引いて使用する必要がある。 On the other hand, the display size of the LCD used for the display unit 17 has, for example, a standard as shown in FIG. Of the display size standards shown in FIG. 12, high-resolution LCDs such as SXGA and UGA are generally used most frequently. The display capability of such an LCD is 1024 dots vertically for SXGA and 1200 dots vertically for UGA. In an ultrasonic diagnostic apparatus, pixels of about 1000 dots are usually used for display.
That is, when sampling is performed at a sampling frequency of 200 MHz, all the sampled data cannot be converted into an image and cannot be displayed. Therefore, in the example shown in the above formula (4), until about 1/12. It is necessary to thin out the sampled data.
　以上の理由から、整相加算時には高いサンプリング周波数にてサンプリングを行うのがよいが、サンプリングしたデータに基づいて画像を表示させる場合には、データの間引きを行う必要がある。 For the above reasons, it is preferable to perform sampling at a high sampling frequency at the time of phasing addition. However, when displaying an image based on the sampled data, it is necessary to thin out the data.
　なお、超音波診断装置では、上述したように、一部の部位を拡大して表示するために、表示サイズの４倍程度の画像データを保持することが行われており、その場合には、６０ＭＨｚのサンプリング周波数によるサンプリングデータを保持しておくのが好ましい。
　ここで、１５ＭＨｚの受信信号を６０ＭＨｚのサンプリング周波数でサンプリングを行うようにした場合、上述した例と同様、振動子２ａから５０ｍｍの距離にある物体に対して送信超音波を出力した後、反射超音波の受信が完了するまでの間にサンプリングされるデータの数は下記式（５）の通りとなる。
５０＊１０－３＊２／１５４０＊６０＊１０６≒３８９６・・・（５） In the ultrasonic diagnostic apparatus, as described above, in order to enlarge and display a part of the image, it is performed to hold image data about four times the display size. It is preferable to hold sampling data with a sampling frequency of 60 MHz.
Here, in the case where the 15 MHz received signal is sampled at the sampling frequency of 60 MHz, the transmission ultrasonic wave is output to the object at a distance of 50 mm from the transducer 2a and then the reflected ultrasonic wave is output as in the above example. The number of data sampled until the reception of the sound wave is completed is expressed by the following equation (5).
50 * 10 −3 * 2/1540 * 60 * 10 6 ≈3896 (5)
　つまり、２００ＭＨｚのサンプリング周波数でサンプリングしたサンプリングデータに対しておよそ３／１０の割合でデータの間引きを行い、６０ＭＨｚのサンプリング周波数にダウンサンプリングするのがよいことになる。 That is, it is better to thin out the data at a rate of about 3/10 with respect to the sampling data sampled at the sampling frequency of 200 MHz and down-sample to the sampling frequency of 60 MHz.
　しかしながら、６０ＭＨｚと２００ＭＨｚは整数比となっていないため、６０ＭＨｚにダウンサンプリングするため、一部のデータについては、２００ＭＨｚのサンプリング周波数でサンプリングしたサンプリングデータから補間処理等を行ってデータを算出する必要がある。補間処理を行う場合には、例えば、以下のようにしてサンプリングデータを算出することができる。 However, since 60 MHz and 200 MHz do not have an integer ratio, downsampling to 60 MHz is necessary. For some data, it is necessary to perform interpolation processing or the like from sampling data sampled at a sampling frequency of 200 MHz. is there. When performing the interpolation process, for example, sampling data can be calculated as follows.
　図１３に示すように、２００ＭＨｚのサンプリング周波数によるサンプリング点に対して、６０ＭＨｚのサンプリング周波数によるサンプリング点は図中ａ～ｃに示す位置となる。すなわち、ａとｂのサンプリング点については、２００ＭＨｚのサンプリング周波数によるサンプリング点と一致しないため、補間処理にて算出する必要がある。この場合、例えば、以下のようにしてリニア補間にて算出することによりサンプリングデータの算出を簡素に行うことができる。なお、２００ＭＨｚのサンプリング周波数による各サンプリング点におけるサンプリングデータの示す値（サンプリング値）を図１４に示す。 As shown in FIG. 13, with respect to the sampling point with a sampling frequency of 200 MHz, the sampling point with a sampling frequency of 60 MHz is located at positions a to c in the figure. That is, the sampling points a and b do not coincide with the sampling points at the sampling frequency of 200 MHz, and thus need to be calculated by interpolation processing. In this case, for example, the sampling data can be simply calculated by calculating by linear interpolation as follows. In addition, the value (sampling value) which the sampling data in each sampling point by the sampling frequency of 200 MHz shows in FIG.
　サンプリング点ａのサンプリング値を算出する場合は、２００ＭＨｚのサンプリング周波数によるサンプリング点「３」及び「４」におけるサンプリング値をリニア補間して生成する。
　すなわち、図１５に示すように、２００ＭＨｚのサンプリング周波数によるサンプリング点「３」から「４」の距離を１とした場合、サンプリング点ａは、２００ＭＨｚのサンプリング周波数によるサンプリング点「３」から１／３の位置となるので、サンプリング点ａのサンプリング値は下記式（６）の通りとなる。
０．９８７６８８＊１／３＋０．８０９０１７＊２／３＝０．８６８５７４・・・（６） When calculating the sampling value of the sampling point a, the sampling values at the sampling points “3” and “4” with the sampling frequency of 200 MHz are generated by linear interpolation.
That is, as shown in FIG. 15, when the distance from the sampling point “3” to “4” at the sampling frequency of 200 MHz is 1, the sampling point a is 1/3 from the sampling point “3” at the sampling frequency of 200 MHz. Therefore, the sampling value of the sampling point a is as shown in the following formula (6).
0.987688 * 1/3 + 0.809017 * 2/3 = 0.868574 (6)
　また、サンプリング点ｂのサンプリング値を算出する場合は、２００ＭＨｚのサンプリング周波数によるサンプリング点「６」及び「７」におけるサンプリング値をリニア補間して生成する。
　すなわち、図１６に示すように、２００ＭＨｚのサンプリング周波数によるサンプリング点「６」から「７」の距離を１とした場合、サンプリング点ｂは、２００ＭＨｚのサンプリング周波数によるサンプリング点「６」から２／３の位置となるので、サンプリング点ｂのサンプリング値は下記式（７）の通りとなる。
０．７０７１０７＊１／３＋０．３０９０１７＊２／３≒０．４４１７１３７・・・（７） When calculating the sampling value at the sampling point b, the sampling values at the sampling points “6” and “7” at the sampling frequency of 200 MHz are generated by linear interpolation.
That is, as shown in FIG. 16, when the distance from the sampling point “6” to “7” at the sampling frequency of 200 MHz is 1, the sampling point b is 2/3 from the sampling point “6” at the sampling frequency of 200 MHz. Therefore, the sampling value at the sampling point b is as shown in the following formula (7).
0.707107 * 1/3 + 0.309017 * 2 / 3≈0.4417137 (7)
　ここで、１５ＭＨｚの受信信号を６００ＭＨｚのサンプリング周波数でサンプリングを行った場合の結果を図１７に示す。 Here, FIG. 17 shows the result of sampling a 15 MHz received signal at a sampling frequency of 600 MHz.
　図１７に示すように、サンプリング点ａ及びｂについてリニア補間を行ってサンプリング値を得た場合、これらのサンプリング値は、実際にサンプリングを行って得た値と比較すると誤差が生じているのがわかる。すなわち、このような誤差は波形歪み、もしくは、補間誤差となり、そのまま画像データに反映される結果となるため、アーチファクトの原因となる場合がある。特に、超音波の生体伝搬中に生じる波形歪みを画像化するＴＨＩを適用した場合には、このような誤差はそのままアーチファクトとなって画像化されてしまう。 As shown in FIG. 17, when sampling values are obtained by performing linear interpolation on sampling points a and b, these sampling values have errors when compared with values obtained by actual sampling. Recognize. That is, such an error becomes a waveform distortion or an interpolation error and is reflected in the image data as it is, which may cause an artifact. In particular, when THI that images waveform distortion that occurs during propagation of ultrasound waves is applied, such an error is directly imaged as an artifact.
　そこで、本実施の形態を適用することにより、このようなアーチファクトを低減させることができる。
　すなわち、本実施の形態では、１５ＭＨｚの受信信号を２００ＭＨｚのサンプリング周波数でサンプリングして、整相加算を行って、図１４に示されるサンプリング結果を得た後、図１８に示すように、サンプリング周波数が６００ＭＨｚとなるように、取得したサンプリングデータの各データ間に０を２個ずつ挿入することによってオーバーサンプリングを行う。そして、オーバーサンプリングされたデータに対してＢＰＦ処理を行うと、図１９に示されるように、実際に６００ＭＨｚのサンプリング周波数にてサンプリングを行った結果とほとんど相違のない結果が得られる。
　そして、上述のようにしてオーバーサンプリングされたサンプリングデータに対して１／１０となるように間引きを行ってサンプリング周波数が６０ＭＨｚとなるようにダウンサンプリングすると、図２０に示されるような結果が得られる。すなわち、１５ＭＨｚの受信信号を６０ＭＨｚのサンプリング周波数でサンプリングしたオリジナルのデータとほとんど相違のない結果が得られ、精度の高いデータとなる。 Therefore, by applying this embodiment, such artifacts can be reduced.
That is, in this embodiment, a 15 MHz reception signal is sampled at a sampling frequency of 200 MHz, and phasing addition is performed to obtain a sampling result shown in FIG. 14, and then, as shown in FIG. Oversampling is performed by inserting two zeros between each piece of acquired sampling data so that the frequency becomes 600 MHz. When the BPF process is performed on the oversampled data, as shown in FIG. 19, a result almost same as the result obtained by actually sampling at the sampling frequency of 600 MHz is obtained.
Then, when the sampling data over-sampled as described above is thinned out to 1/10 and down-sampled so that the sampling frequency is 60 MHz, the result shown in FIG. 20 is obtained. . That is, the result is almost the same as the original data obtained by sampling the 15 MHz received signal at the sampling frequency of 60 MHz, and the data is highly accurate.
　以上説明したように、本発明の実施の形態によれば、超音波探触子２は、駆動信号によって被検体に向けて送信超音波を出力するとともに、被検体からの反射超音波を受信することにより受信信号を出力する複数の振動子２ａを有する。そして、送信部１２は、振動子２ａに駆動信号を供給する。そして、受信部１３は、振動子２ａによって得られた受信信号を予め設定された取得サンプリング周波数にてサンプリングする。そして、受信部１３は、サンプリング点毎に受信信号を整相加算して取得サンプリングデータを得る。そして、表示部１７は、取得サンプリングデータに基づいて超音波診断画像の表示を行う。そして、制御部１８は、表示部１７の表示画像サイズに応じて設定された表示依存サンプリング周波数となるように取得サンプリングデータからデータを間引いてダウンサンプリングする。そして、表示部１７は、制御部１８によってダウンサンプリングされた取得サンプリングデータに基づいて超音波診断画像を表示する。その結果、高いサンプリング周波数によって波形再現性の優れたサンプリングデータが得られ、このサンプリングデータから表示画像サイズに好適なデータ量に間引く際に、波形歪みや補間誤差の発生を抑制することができるので、アーチファクトのない、良好な超音波診断画像を表示することができる。また、超音波診断画像を表示するために必要以上のサンプリングデータを保持する必要がないため、メモリ量の増大が抑制され、消費電力の節約も図れるようになる。特に、バッテリ駆動される超音波診断装置にあっては、動作可能時間の長時間化が図れるようになる。 As described above, according to the embodiment of the present invention, the ultrasonic probe 2 outputs a transmission ultrasonic wave toward the subject by the drive signal and receives a reflected ultrasonic wave from the subject. Accordingly, a plurality of vibrators 2a that output reception signals are provided. Then, the transmission unit 12 supplies a drive signal to the vibrator 2a. Then, the reception unit 13 samples the reception signal obtained by the transducer 2a at a preset acquisition sampling frequency. Then, the receiving unit 13 obtains acquired sampling data by phasing and adding the received signals for each sampling point. Then, the display unit 17 displays an ultrasound diagnostic image based on the acquired sampling data. Then, the control unit 18 performs downsampling by thinning out the data from the acquired sampling data so that the display-dependent sampling frequency set according to the display image size of the display unit 17 is obtained. The display unit 17 displays an ultrasound diagnostic image based on the acquired sampling data downsampled by the control unit 18. As a result, sampling data with excellent waveform reproducibility can be obtained with a high sampling frequency, and waveform distortion and interpolation errors can be suppressed when thinning out this sampling data to a data amount suitable for the display image size. It is possible to display a good ultrasonic diagnostic image without artifacts. In addition, since it is not necessary to hold more sampling data than is necessary to display an ultrasonic diagnostic image, an increase in the amount of memory is suppressed and power consumption can be saved. In particular, in an ultrasonic diagnostic apparatus driven by a battery, the operable time can be extended.
　また、本発明の実施の形態によれば、制御部１８は、受信部１３によって得られた取得サンプリングデータを、取得サンプリング周波数と表示依存サンプリング周波数との最小公倍数となるようにオーバーサンプリングした後、表示依存サンプリング周波数となるようにダウンサンプリングする。その結果、ダウンサンプリングに伴う補間データの生成が不要となり、補間データを生成することにより生じる補間誤差を起因とするアーチファクトの発生を抑制でき、精度の高い画像データを生成することができる。 Further, according to the embodiment of the present invention, the control unit 18 after oversampling the acquired sampling data obtained by the receiving unit 13 so as to be the least common multiple of the acquired sampling frequency and the display dependent sampling frequency, Downsampling to a display-dependent sampling frequency. As a result, generation of interpolation data associated with downsampling becomes unnecessary, generation of artifacts due to interpolation errors caused by generating interpolation data can be suppressed, and highly accurate image data can be generated.
　なお、本発明の実施の形態における記述は、本発明に係る超音波診断装置の一例であり、これに限定されるものではない。超音波診断装置を構成する各機能部の細部構成及び細部動作に関しても適宜変更可能である。 The description in the embodiment of the present invention is an example of the ultrasonic diagnostic apparatus according to the present invention, and the present invention is not limited to this. The detailed configuration and detailed operation of each functional unit constituting the ultrasonic diagnostic apparatus can be appropriately changed.
　また、本実施の形態では、取得サンプリング周波数と表示依存サンプリング周波数との最小公倍数であるサンプリング周波数を設定し、取得サンプリングデータに対してオーバーサンプリングを行うようにしたが、取得サンプリング周波数が表示依存サンプリング周波数の整数倍であるときは、オーバーサンプリング処理は不要となる。 In this embodiment, the sampling frequency which is the least common multiple of the acquisition sampling frequency and the display dependent sampling frequency is set and oversampling is performed on the acquired sampling data. When the frequency is an integral multiple of the frequency, the oversampling process is not necessary.
　また、本実施の形態では、オーバーサンプリング処理及びダウンサンプリング処理を制御部によるソフトウエア処理により実現したが、ハードウエアにより実現するようにしてもよい。 In this embodiment, the oversampling process and the downsampling process are realized by software processing by the control unit, but may be realized by hardware.
　また、本実施の形態では、ゼロデータをサンプリングデータの間に挿入することによってオーバーサンプリング処理を行ったが、他の方法によってオーバーサンプリング処理を行うようにしてもよい。 In this embodiment, the oversampling process is performed by inserting zero data between the sampling data. However, the oversampling process may be performed by another method.
　また、本実施の形態では、サンプリングデータを間引くことによりダウンサンプリング処理を行うようにしたが、他の方法によってダウンサンプリング処理を行うようにしてもよい。 In this embodiment, the downsampling process is performed by thinning out the sampling data. However, the downsampling process may be performed by other methods.
　また、本実施の形態では、本発明に係るプログラムのコンピュータ読み取り可能な媒体としてハードディスクや半導体の不揮発性メモリ等を使用した例を開示したが、この例に限定されない。その他のコンピュータ読み取り可能な媒体として、ＣＤ－ＲＯＭ等の可搬型記録媒体を適用することが可能である。また、本発明に係るプログラムのデータを通信回線を介して提供する媒体として、キャリアウェーブ（搬送波）も適用される。 In this embodiment, an example in which a hard disk, a semiconductor nonvolatile memory, or the like is used as a computer-readable medium of the program according to the present invention is disclosed, but the present invention is not limited to this example. As other computer-readable media, a portable recording medium such as a CD-ROM can be applied. A carrier wave is also used as a medium for providing program data according to the present invention via a communication line.
　超音波画像によって診断を行う分野（特に医療分野）において利用可能性がある。 There is a possibility that it can be used in the field of diagnosis (especially in the medical field) using ultrasound images.
Ｓ　超音波診断装置
１　超音波診断装置本体
２　超音波探触子
２ａ　振動子
１２　送信部
１３　受信部
１７　表示部
１８　制御部 S ultrasonic diagnostic apparatus 1 ultrasonic diagnostic apparatus main body 2 ultrasonic probe 2a transducer 12 transmitting unit 13 receiving unit 17 display unit 18 control unit

Claims (3)

  1. 　駆動信号によって被検体に向けて送信超音波を出力するとともに、被検体からの反射超音波を受信することにより受信信号を出力する複数の振動子を有する超音波探触子と、
    　前記振動子に駆動信号を供給する送信部と、
    　前記振動子によって得られた受信信号を予め設定された取得サンプリング周波数にてサンプリングし、該サンプリング点毎に前記受信信号を整相加算して取得サンプリングデータを得る受信部と、
    　前記取得サンプリングデータに基づいて超音波診断画像の表示を行う表示部と、
    　前記表示部の表示画像サイズに応じて設定された表示依存サンプリング周波数となるように前記取得サンプリングデータからデータを間引いてダウンサンプリングする制御部と、
    　を備え、
    　前記表示部は、前記制御部によってダウンサンプリングされた前記取得サンプリングデータに基づいて前記超音波診断画像を表示することを特徴とする超音波診断装置。　     An ultrasonic probe having a plurality of transducers for outputting a transmission signal by receiving a reflected ultrasonic wave from the subject and outputting a transmission ultrasonic wave toward the subject by a driving signal;
    A transmitter for supplying a drive signal to the vibrator;
    A reception unit that samples the reception signal obtained by the transducer at a preset acquisition sampling frequency, and obtains acquisition sampling data by phasing and adding the reception signal at each sampling point;
    A display unit for displaying an ultrasound diagnostic image based on the acquired sampling data;
    A control unit that thins out data from the acquired sampling data and down-samples to obtain a display-dependent sampling frequency set according to a display image size of the display unit;
    With
    The ultrasonic diagnostic apparatus, wherein the display unit displays the ultrasonic diagnostic image based on the acquired sampling data down-sampled by the control unit.
  2. 　前記制御部は、前記受信部によって得られた前記取得サンプリングデータを、前記取得サンプリング周波数と前記表示依存サンプリング周波数との最小公倍数となるようにオーバーサンプリングした後、前記表示依存サンプリング周波数となるようにダウンサンプリングすることを特徴とする請求項１に記載の超音波診断装置。 The control unit oversamples the acquired sampling data obtained by the receiving unit so as to be a least common multiple of the acquired sampling frequency and the display dependent sampling frequency, and then becomes the display dependent sampling frequency. The ultrasonic diagnostic apparatus according to claim 1, wherein downsampling is performed.
  3. 　駆動信号によって被検体に向けて送信超音波を出力するとともに、被検体からの反射超音波を受信することにより受信信号を出力する複数の振動子を有する超音波診断装置に設けられたコンピュータに、
    　予め設定された取得サンプリング周波数にてサンプリングされ、該サンプリング点毎に整相加算された前記受信信号の取得サンプリングデータを取得する機能と、
    　前記取得サンプリングデータに基づいて超音波診断画像の表示を行う表示部の表示画像サイズに応じて設定された表示依存サンプリング周波数となるように、前記取得サンプリングデータからデータを間引いてダウンサンプリングする機能と、
    　該ダウンサンプリングされた前記取得サンプリングデータを出力する機能と、
    　を実現させるためのプログラム。     A computer provided in an ultrasonic diagnostic apparatus having a plurality of transducers that outputs a reception signal by receiving a reflected ultrasonic wave from a subject while outputting a transmission ultrasonic wave toward the subject by a drive signal,
    A function of acquiring the acquired sampling data of the received signal sampled at a preset acquisition sampling frequency and phased and added for each sampling point;
    A function of thinning down the data from the acquired sampling data and down-sampling so as to obtain a display-dependent sampling frequency set according to the display image size of the display unit that displays an ultrasound diagnostic image based on the acquired sampling data; ,
    A function of outputting the downsampled acquired sampling data;
    A program to realize
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WO2020007817A1 (en) 2018-07-04 2020-01-09 F. Hoffmann-La Roche Ag Novel bispecific agonistic 4-1bb antigen binding molecules
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JPWO2019230740A1 (en) * 2018-05-28 2021-08-26 国立研究開発法人理化学研究所 Tomographic image data acquisition method by oversampling, acquisition device, and control program
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WO2017055398A2 (en) 2015-10-02 2017-04-06 F. Hoffmann-La Roche Ag Bispecific antibodies specific for a costimulatory tnf receptor
WO2017060144A1 (en) 2015-10-07 2017-04-13 F. Hoffmann-La Roche Ag Bispecific antibodies with tetravalency for a costimulatory tnf receptor
WO2018127473A1 (en) 2017-01-03 2018-07-12 F. Hoffmann-La Roche Ag Bispecific antigen binding molecules comprising anti-4-1bb clone 20h4.9
WO2018185045A1 (en) 2017-04-04 2018-10-11 F. Hoffmann-La Roche Ag Novel bispecific antigen binding molecules capable of specific binding to cd40 and to fap
JPWO2019230740A1 (en) * 2018-05-28 2021-08-26 国立研究開発法人理化学研究所 Tomographic image data acquisition method by oversampling, acquisition device, and control program
WO2020007817A1 (en) 2018-07-04 2020-01-09 F. Hoffmann-La Roche Ag Novel bispecific agonistic 4-1bb antigen binding molecules
WO2020070035A1 (en) 2018-10-01 2020-04-09 F. Hoffmann-La Roche Ag Bispecific antigen binding molecules with trivalent binding to cd40
WO2024074727A1 (en) 2022-10-07 2024-04-11 Genethon Immunotherapy of skeletal myopathies using anti-fap car-t cells

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