WO2015008534A1 - 超音波観測装置、超音波観測装置の作動方法および超音波観測装置の作動プログラム - Google Patents
超音波観測装置、超音波観測装置の作動方法および超音波観測装置の作動プログラム Download PDFInfo
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- WO2015008534A1 WO2015008534A1 PCT/JP2014/063395 JP2014063395W WO2015008534A1 WO 2015008534 A1 WO2015008534 A1 WO 2015008534A1 JP 2014063395 W JP2014063395 W JP 2014063395W WO 2015008534 A1 WO2015008534 A1 WO 2015008534A1
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
- A61B8/44—Constructional features of the ultrasonic, sonic or infrasonic diagnostic device
- A61B8/4444—Constructional features of the ultrasonic, sonic or infrasonic diagnostic device related to the probe
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
- A61B8/13—Tomography
- A61B8/14—Echo-tomography
- A61B8/145—Echo-tomography characterised by scanning multiple planes
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
- A61B8/44—Constructional features of the ultrasonic, sonic or infrasonic diagnostic device
- A61B8/4477—Constructional features of the ultrasonic, sonic or infrasonic diagnostic device using several separate ultrasound transducers or probes
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
- A61B8/52—Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves
- A61B8/5207—Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves involving processing of raw data to produce diagnostic data, e.g. for generating an image
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
- A61B8/54—Control of the diagnostic device
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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
- G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
- G01S15/88—Sonar systems specially adapted for specific applications
- G01S15/89—Sonar systems specially adapted for specific applications for mapping or imaging
- G01S15/8906—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques
- G01S15/895—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques characterised by the transmitted frequency spectrum
-
- 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
- G01S7/52033—Gain control of receivers
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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
- G01S7/5205—Means for monitoring or calibrating
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
- A61B8/44—Constructional features of the ultrasonic, sonic or infrasonic diagnostic device
- A61B8/4438—Means for identifying the diagnostic device, e.g. barcodes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
- B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
- B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
- B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
- B06B1/0207—Driving circuits
Definitions
- the present invention relates to an ultrasonic observation apparatus that observes a tissue of a specimen using ultrasonic waves, an operation method of the ultrasonic observation apparatus, and an operation program of the ultrasonic observation apparatus.
- an ultrasound observation apparatus that generates an ultrasound image of a specimen based on ultrasound
- it is desirable that the image displayed when quantitatively evaluating the ultrasound image is not affected by the type of ultrasound probe that transmits and receives ultrasound.
- vibration that has been stored in advance when an image is generated using a received signal in order to suppress variation of each transducer.
- a technique for correcting a received signal based on a frequency characteristic of a child is disclosed (for example, see Patent Document 1).
- a technique for monitoring the transmission drive signal and correcting the transmission drive signal based on the ideal waveform data stored in advance in order to suppress variation of each vibrator is disclosed (for example, see Patent Document 2). reference).
- the present invention has been made in view of the above, and an ultrasonic observation apparatus and an ultrasonic observation apparatus capable of realizing observation of an ultrasonic image that eliminates the influence of the difference in the type of ultrasonic probe. It is an object to provide an operation method and an operation program for an ultrasonic observation apparatus.
- an ultrasonic observation apparatus converts an electrical transmission drive wave into an ultrasonic transmission echo, and transmits the transmission echo to a specimen.
- an ultrasonic probe that receives a reception echo reflected by the specimen and converts it into an electrical reception signal, and a parameter that gives characteristics according to the type of the ultrasonic probe, the transmission drive
- a storage unit that stores parameters necessary for wave generation and correction of the received signal, and the parameters stored in the storage unit are referred to, and the frequency spectrum of the transmission echo in a predetermined frequency band is the ultrasonic probe.
- the transmission drive wave generation unit that generates the transmission drive wave according to the type of the ultrasound probe, and the parameter stored in the storage unit, so that the same regardless of the type of A reception signal correction unit that corrects the received signal according to the type of the ultrasound probe, an image processing unit that generates image data using the reception signal corrected by the reception signal correction unit, and It is provided with.
- the transmission drive wave generator generates a frequency spectrum having a larger value as the attenuation amount is larger when converted into the transmission echo by the ultrasonic probe.
- the transmission drive wave is generated, and the reception signal correction unit corrects the reception signal for each frequency based on the attenuation amount.
- the storage unit calculates the attenuation amount for each frequency in the frequency spectrum when the transmission drive wave or the reception echo is converted by the ultrasonic probe.
- the transmission drive wave generation unit stores the parameter in association with the type of the ultrasonic probe, and the transmission drive wave generation unit stores the frequency spectrum of a predetermined frequency band to be output as the transmission echo.
- the transmission drive wave is generated by adding an attenuation amount for each frequency
- the reception signal correction unit stores the attenuation stored in the storage unit with respect to the frequency spectrum of the reception signal received from the ultrasonic probe.
- the received signal is corrected by adding a quantity for each frequency.
- the ultrasonic observation apparatus is characterized in that, in the above invention, the ultrasonic probe can be selected from a plurality of ultrasonic probes of different types.
- a frequency analysis unit that calculates a frequency spectrum by analyzing a frequency of an ultrasonic wave received by the ultrasonic probe, and a frequency calculated by the frequency analysis unit.
- a feature amount extraction unit that extracts at least one feature amount from the frequency spectrum by approximating the spectrum, and the image processing unit is a feature amount image corresponding to the feature amount extracted by the feature amount extraction unit
- a feature amount image data generation unit for generating data is provided.
- the feature amount extraction unit contributes to attenuation generated according to an ultrasonic reception depth and frequency before or after performing the frequency spectrum approximation processing. Attenuation correction processing is performed to reduce the above.
- the ultrasonic observation apparatus is characterized in that, in the above invention, the feature amount extraction unit approximates a frequency spectrum to be approximated by a polynomial by regression analysis.
- the feature amount extraction unit approximates the frequency spectrum to be approximated by a linear expression, and the inclination of the linear expression, the intercept of the linear expression, and the inclination At least one of intensities determined using the intercept and a specific frequency included in a frequency region of the frequency spectrum is extracted as a feature amount.
- the operation method of the ultrasonic observation apparatus converts an electrical transmission drive wave into an ultrasonic transmission echo, transmits the transmission echo to the specimen, and receives the reception echo reflected by the specimen.
- a parameter that gives characteristics according to the type of ultrasonic probe that is received and converted into an electrical reception signal, and that stores parameters necessary for generation of the transmission drive wave and correction of the reception signal With reference to the parameter, referring to the transmission drive wave generation step of generating the transmission drive wave according to the type of the ultrasound probe by a transmission drive wave generation unit, the parameter stored in the storage unit, A received signal correction step for correcting the received signal according to the type of the ultrasound probe, and image data using the received signal corrected in the received signal correction step.
- the operation program of the ultrasonic observation apparatus converts an electrical transmission drive wave into an ultrasonic transmission echo, transmits the transmission echo to a specimen, and receives a reception echo reflected by the specimen.
- a parameter that gives characteristics according to the type of ultrasonic probe that is received and converted into an electrical reception signal, and that stores parameters necessary for generation of the transmission drive wave and correction of the reception signal With reference to the parameter, referring to the transmission drive wave generation step of generating the transmission drive wave according to the type of the ultrasound probe by a transmission drive wave generation unit, the parameter stored in the storage unit, A received signal correction step for correcting the received signal in accordance with the type of the ultrasound probe, and image reception using the received signal corrected in the received signal correction step. Characterized in that to execute an image processing step of generating a data, to the computer.
- FIG. 1 is a block diagram showing a configuration of an ultrasonic observation apparatus according to Embodiment 1 of the present invention.
- FIG. 2 is a diagram illustrating a change in the frequency spectrum when the signal conversion unit converts the transmission drive wave into a transmission echo.
- FIG. 3 is a diagram illustrating a transmission drive wave generated by the transmission drive wave generation unit and a case where the signal conversion unit of the ultrasonic probe converts the transmission drive wave into a transmission echo.
- FIG. 4 is a diagram illustrating an outline (first example) of correction processing performed by the reception signal correction unit.
- FIG. 5 is a diagram showing an outline (second example) of correction processing performed by the reception signal correction unit.
- FIG. 1 is a block diagram showing a configuration of an ultrasonic observation apparatus according to Embodiment 1 of the present invention.
- FIG. 2 is a diagram illustrating a change in the frequency spectrum when the signal conversion unit converts the transmission drive wave into a transmission echo.
- FIG. 3 is a diagram illustrating a transmission
- FIG. 6 is a diagram illustrating a relationship between the reception depth and the amplification factor in the amplification process performed by the STC correction unit on the reception signal corrected by the reception signal correction unit.
- FIG. 7 is a flowchart showing an outline of processing of the ultrasonic observation apparatus according to Embodiment 1 of the present invention.
- FIG. 8 is a block diagram showing a configuration of an ultrasonic observation apparatus according to Embodiment 2 of the present invention.
- FIG. 9 is a diagram illustrating the relationship between the reception depth and the amplification factor in the amplification process performed by the amplification correction unit.
- FIG. 10 is a diagram illustrating an example of a frequency spectrum calculated by the frequency analysis unit.
- FIG. 11 is a diagram illustrating a frequency spectrum (first example) before and after correction by the reception signal correction unit when an ultrasonic probe is used.
- FIG. 12 is a diagram illustrating a frequency spectrum (second example) before and after correction by the reception signal correction unit when an ultrasonic probe is used.
- FIG. 13 is a diagram in which the feature amounts of the frequency spectrum curves shown in FIGS. 11 and 12 are plotted in the feature amount space.
- FIG. 14 is a diagram illustrating a straight line corresponding to the feature amount corrected by the attenuation correction unit.
- FIG. 15 is a flowchart showing an outline of processing of the ultrasonic observation apparatus according to Embodiment 2 of the present invention.
- FIG. 16 is a flowchart illustrating an outline of processing performed by the frequency analysis unit.
- FIG. 17 is a diagram schematically showing a data array of one sound ray.
- FIG. 18 is a diagram schematically illustrating an outline of the attenuation correction process performed by the attenuation correction unit of the ultrasonic observation apparatus according to another embodiment of the present invention.
- FIG. 1 is a block diagram showing a configuration of an ultrasonic observation apparatus according to Embodiment 1 of the present invention.
- An ultrasonic observation apparatus 1 shown in FIG. 1 is an apparatus for observing a specimen that is a diagnosis target using ultrasonic waves.
- the ultrasonic observation apparatus 1 outputs an ultrasonic transmission echo to the outside, receives an ultrasonic reception echo reflected from the outside, and converts it into an electrical reception signal;
- the transmitter / receiver 3 transmits / receives an electrical signal to / from the acoustic probe 2, the image processor 4 generates image data corresponding to the received signal, and an interface such as a keyboard, a mouse, and a touch panel.
- An input unit 5 that receives input of various types of information, a display unit 6 that displays various types of information including an image generated by the image processing unit 4 and that is realized by using a display panel made of liquid crystal, organic EL, or the like;
- a storage unit 7 that stores various kinds of information necessary for ultrasonic observation including parameters indicating characteristics according to the type of the touch element 2 and a control unit 8 that controls the operation of the ultrasonic observation apparatus 1 are provided.
- the ultrasonic observation apparatus 1 includes a scope in which an ultrasonic probe 2 is provided at a distal end portion thereof, and a processing apparatus (processor) in which a base end of the scope is detachably connected and the above-described parts other than the ultrasonic probe 2 are provided. ).
- the ultrasonic probe 2 converts the transmission drive wave, which is an electrical pulse signal received from the transmission / reception unit 3, into a transmission echo, which is an acoustic pulse signal, and the received echo that has been reflected and returned by an external specimen. It has a signal converter 21 for converting it into an electrical reception signal.
- the signal conversion unit 21 functions as a filter.
- FIG. 2 is a diagram illustrating a change in frequency spectrum when the signal conversion unit 21 converts a transmission drive wave into a transmission echo.
- the horizontal axis f represents frequency and the vertical axis I represents intensity.
- F ⁇ f
- FIGS. 2B and 2C are diagrams showing the spectrums of transmission echoes generated by the signal converters 21 of the ultrasonic probes 2 of different types.
- the spectrum C 2 shown in FIG. 2B is more attenuated than the spectrum C 3 shown in FIG.
- the amount of attenuation ⁇ I 1 (f 1 ) corresponding to the difference between the spectrum C 1 and the spectrum C 2 at an arbitrary frequency f 1 (f L ⁇ f 1 ⁇ f H ) in the frequency band F is
- the ultrasonic probe information is stored in the ultrasonic probe information storage unit 71 of the storage unit 7 in association with the type of the acoustic probe 2.
- the attenuation amount ⁇ I 2 (f 1 ) corresponding to the difference between the spectrum C 1 and the spectrum C 3 at an arbitrary frequency f 1 in the frequency band F is also the kind of the ultrasound probe 2.
- the ultrasound probe information storage unit 71 is also the kind of the ultrasound probe 2.
- two ultrasonic probes 2 have been described as examples, but other types of ultrasonic probes 2 may be stored in the ultrasonic probe information storage unit 71 in the same manner. Is possible.
- the ultrasonic probe 2 for outputting a spectrum C 2 shown in FIG. 2 (b) as a transmission echo ultrasonic probe 2A
- the ultrasonic probe 2 to the spectrum C 3 is output as transmission echoes shown in FIG. 2 (c) of ultrasonic probe 2B.
- the signal conversion unit 21 of the ultrasonic probe 2A is referred to as a signal conversion unit 21A
- the signal conversion unit 21 of the ultrasonic probe 2B is referred to as a signal conversion unit 21B.
- the ultrasonic probe 2 may be one that mechanically scans an ultrasonic transducer, or one that electronically scans a plurality of ultrasonic transducers. In the first embodiment, it is possible to select and use any one of a plurality of different types of ultrasound probes 2 as the ultrasound probe 2.
- the transmitting / receiving unit 3 is electrically connected to the ultrasonic probe 2.
- the transmission / reception unit 3 generates a transmission drive wave based on a preset waveform and transmission timing, and transmits the generated transmission drive wave to the ultrasonic probe 2.
- a received signal correction unit 32 that corrects the received signal received from the probe 2 to eliminate the influence of the difference in characteristics depending on the type of the ultrasound probe 2, and the received signal corrected by the received signal correction unit 32
- the STC correction unit 33 performs STC (Sensitivity Time Control) correction that corrects at a higher amplification factor as the reception depth increases.
- the transmission drive wave generation unit 31 generates a waveform based on the characteristics of the ultrasound probe 2 as a transmission drive wave based on information stored in an ultrasound probe information storage unit 71 of the storage unit 7 to be described later.
- FIG. 3 is a diagram illustrating a transmission drive wave generated by the transmission drive wave generation unit 31 and a case where the signal conversion unit 21 of the ultrasound probe 2 converts the transmission drive wave into a transmission echo.
- the transmission drive wave generation unit 31 generates different transmission drive waves for each type of the ultrasound probe 2. Specifically, the transmission drive wave generation unit 31 reads out the characteristics corresponding to the type of the ultrasound probe 2 from the ultrasound probe information storage unit 71, and has a rectangular shape as shown in FIG. A transmission drive wave having a spectrum C 6 is generated.
- the characteristics of the ultrasonic probe 2 here are the attenuation amounts ⁇ I 1 (f) and ⁇ I 2 (f) (where f ⁇ F) and the ultrasonic probe shown in FIGS. 2B and 2C, respectively. This means information unique to each ultrasonic probe 2 including the type of the probe 2.
- the curve and the straight line are composed of a set of discrete points.
- the transmission drive wave generator 31 generates a transmission drive wave corresponding to the type of the ultrasound probe 2 based on the spectrum of the transmission echo to be generated and the characteristics of the ultrasound probe 2.
- the transmission drive wave generation unit 31 generates a transmission drive wave having a frequency spectrum in a predetermined frequency band of the transmission echo that is different for each type of the ultrasonic probe.
- a spectrum C 4 of the transmission drive wave shown in FIG. 3A is for the ultrasonic probe 2A
- a spectrum C 5 of the transmission drive wave shown in FIG. 3B is for the ultrasonic probe 2B.
- the spectrum C 4 has a shape obtained by adding an attenuation amount ⁇ I 1 (f) (f ⁇ F) when the ultrasound probe 2A converts the spectrum C 6 of the transmission echo.
- the spectrum C 5 has a shape obtained by adding the attenuation ⁇ I 2 (f) (f ⁇ F) when the ultrasound probe 2B converts the spectrum C 6 of the transmission echo.
- the reception signal correction unit 32 applies correction corresponding to the type of the ultrasonic probe to the reception signal received from the ultrasonic probe 2 by the transmission / reception unit 3.
- FIG. 4 is a diagram showing an outline of the correction process performed by the reception signal correction unit 32, and specifically shows an outline of the correction process for the reception signal sent from the ultrasonic probe 2A.
- Spectrum C 7 shown in FIG. 4 (a) is the frequency spectrum of the received signal the signal conversion unit 21A of the ultrasonic probe 2A is generated by converting the received echo.
- the reception signal correction unit 32 corrects the reception signal by adding attenuation ⁇ I 1 (f) (f ⁇ F) when the ultrasound probe 2A converts the spectrum C 7 .
- a spectrum C 8 shown in FIG. 4B is obtained.
- the spectrum C 8 is a spectrum that excludes the influence of the ultrasonic probe 2A.
- FIG. 5 is a diagram showing an outline of the correction process performed by the reception signal correction unit 32, and specifically shows an outline of the correction process for the reception signal sent from the ultrasonic probe 2B.
- a spectrum C 9 shown in FIG. 5A is a frequency spectrum of a reception signal generated by converting a reception echo by the signal conversion unit 21B of the ultrasonic probe 2B.
- the reception signal correction unit 32 corrects the reception signal by adding the amount of attenuation ⁇ I 2 (f) (f ⁇ F) when the ultrasound probe 2B converts the spectrum C 9 .
- a spectrum C 8 shown in FIG. 5B is obtained.
- This spectrum C 8 is a spectrum that excludes the influence of the ultrasound probe 2B, and is the same as the spectrum obtained as a result of correcting the received signal converted by the ultrasound probe 2A (FIG. 4). (See (b)). In other words, the spectrum C 8 is nothing but the spectrum of the received echo.
- FIG. 6 is a diagram illustrating a relationship between the reception depth and the amplification factor in the amplification process performed by the STC correction unit 33 on the reception signal corrected by the reception signal correction unit 32.
- the reception depth z shown in FIG. 6 is an amount calculated based on the elapsed time from the reception start time of the ultrasonic wave.
- the amplification factor ⁇ (dB) increases linearly from ⁇ 0 to ⁇ th (> ⁇ 0 ) as the reception depth z increases.
- the amplification factor ⁇ takes a constant value ⁇ th when the reception depth z is equal to or greater than the threshold value z th .
- the value of the threshold value z th is such a value that the ultrasonic signal received from the specimen is almost attenuated and the noise becomes dominant. More generally, when the reception depth z is smaller than the threshold value z th , the amplification factor ⁇ may increase monotonously as the reception depth z increases.
- the transmission / reception unit 3 performs processing such as filtering on the echo signal amplified by the STC correction unit 33, and then performs A / D conversion to generate and output a digital RF signal in the time domain.
- processing such as filtering on the echo signal amplified by the STC correction unit 33
- a / D conversion to generate and output a digital RF signal in the time domain.
- the transmission / reception unit 3 has a multi-channel circuit for beam synthesis corresponding to the plurality of ultrasonic transducers.
- the image processing unit 4 includes a B-mode image data generation unit 41 that generates B-mode image data from the received signal.
- the B-mode image data generation unit 41 performs signal processing using a known technique such as a bandpass filter, logarithmic conversion, gain processing, contrast processing, and the like on the digital signal, and also according to the image display range on the display unit 6.
- B-mode image data is generated by thinning out data in accordance with the data step width determined in advance.
- the storage unit 7 includes an ultrasound probe information storage unit 71, an amplification factor information storage unit 72, and a window function storage unit 73.
- the ultrasound probe information storage unit 71 converts the type of the ultrasound probe 2 and the ultrasound probe 2 converts the transmission drive wave into a transmission echo or converts the reception echo into a reception signal.
- the correlation between the amount of attenuation generated in the spectrum during conversion or the like is stored as a parameter.
- the amplification factor information storage unit 72 stores, as amplification factor information, the relationship between the amplification factor and the reception depth that is referred to when the STC correction unit 33 performs amplification processing (for example, the relationship illustrated in FIG. 2).
- the window function storage unit 73 stores at least one of window functions such as Hamming, Hanning, and Blackman.
- the storage unit 7 is realized using a ROM in which an operation program of the ultrasound observation apparatus 1, a program for starting a predetermined OS, and the like are stored in advance, and a RAM in which calculation parameters and data of each process are stored.
- the control unit 8 includes an ultrasonic probe determination unit 81 that determines the type of the connected ultrasonic probe 2.
- the determination result of the ultrasonic probe determination unit 81 is stored in the ultrasonic probe information storage unit 71, and is referred to when the signal conversion unit 21, the transmission drive wave generation unit 31, and the reception signal correction unit 32 perform processing. Is done.
- the scope including the ultrasonic probe 2 determines the type of the ultrasonic probe 2 as a processing device at the connection portion with the processing device at the subsequent stage. It is only necessary to provide a connection pin for this purpose. Thereby, the ultrasonic probe determination unit 81 provided on the processing apparatus side can determine the type of the ultrasonic probe 2 according to the shape of the connection pin of the connected scope.
- the control unit 8 is realized by using a CPU having calculation and control functions.
- the control unit 8 reads out various programs including information stored and stored in the storage unit 7 and the operation program of the ultrasonic observation apparatus 1 from the storage unit 7, thereby performing various arithmetic processes related to the operation method of the ultrasonic observation apparatus 1. To control the ultrasonic observation apparatus 1 in an integrated manner.
- the operation program of the ultrasonic observation apparatus 1 can be recorded on a computer-readable recording medium such as a hard disk, flash memory, CD-ROM, DVD-ROM, or flexible disk and widely distributed. Recording of various programs on a recording medium or the like may be performed when the computer or the recording medium is shipped as a product, or may be performed by downloading via a communication network.
- a computer-readable recording medium such as a hard disk, flash memory, CD-ROM, DVD-ROM, or flexible disk and widely distributed. Recording of various programs on a recording medium or the like may be performed when the computer or the recording medium is shipped as a product, or may be performed by downloading via a communication network.
- FIG. 7 is a flowchart showing an outline of processing of the ultrasonic observation apparatus 1 having the above configuration. It is assumed that the type of the ultrasound probe 2 provided in the ultrasound observation apparatus 1 is determined in advance by the ultrasound probe determination unit 81.
- the transmission drive wave generation unit 31 generates a transmission drive wave and outputs it to the ultrasound probe 2 (step S1).
- the spectrum of the transmission drive wave is a spectrum C 4 shown in FIG.
- the spectrum of the transmitted driving wave is a spectrum C 5 shown in FIG. 3 (b).
- the signal converter 21 converts the transmission drive wave into a transmission echo, and generates and outputs the converted transmission echo (step S2).
- the spectrum of this transmission echo is, for example, the spectrum C 6 in FIG. As described with reference to FIG. 3, the transmission echo has the same spectrum regardless of the type of the ultrasound probe 2.
- the ultrasound probe 2 receives the reception echo returned from the transmission echo reflected by the living body (step S3).
- the signal conversion unit 21 that has received the reception echo converts the reception echo into a reception signal and outputs it to the transmission / reception unit 3 (step S4).
- the spectrum of this received signal is, for example, the spectrum C 7 shown in FIG. 4A in the case of the ultrasonic probe 2A. Also, when the ultrasonic probe 2B, the spectrum of the received signal is a spectrum C 9 shown in Figure 5 (a).
- the reception signal correction unit 32 that has received the reception signal from the ultrasound probe 2 corrects the frequency spectrum (step S5).
- the spectrum of this received signal is the same spectrum regardless of the type of the ultrasound probe 2 (see the spectrum C 8 in FIGS. 4B and 5B).
- the STC correction unit 33 performs STC correction on the reception signal whose spectrum is corrected by the reception signal correction unit 32 (step S6).
- the STC correction unit 33 performs STC correction based on the relationship between the amplification factor and the reception depth illustrated in FIG. 6, for example.
- the B-mode image data generation unit 41 generates B-mode image data using the echo signal amplified by the STC correction unit 33 (step S7).
- the display unit 6 displays a B mode image corresponding to the B mode image generated by the B mode image data generation unit 41 (step S8).
- step S8 the ultrasound observation apparatus 1 ends a series of processes. Note that the ultrasonic observation apparatus 1 may periodically repeat the processes of steps S1 to S8.
- the processing for eliminating the influence according to the type of the ultrasonic probe is performed on both the transmission drive wave and the reception signal, the ultrasonic wave It is possible to realize observation of an ultrasonic image that eliminates the influence of the difference in the type of probe.
- the transmission driving wave having a frequency spectrum having a larger value as the attenuation amount when converted into a transmission echo by the ultrasonic probe is larger is generated, and the received signal is generated. Since the correction is performed for each frequency based on the amount of attenuation, it is possible to reliably eliminate the influence of the difference in characteristics depending on the type of the ultrasonic probe.
- FIG. 8 is a block diagram showing a configuration of an ultrasonic observation apparatus according to Embodiment 2 of the present invention.
- the ultrasonic observation apparatus 11 shown in the figure includes a predetermined calculation for an ultrasonic probe 2, a transmission / reception unit 3, an input unit 5, a display unit 6, a control unit 8, and an electrical reception signal.
- symbol as the ultrasonic observation apparatus 1 is attached
- the arithmetic unit 12 performs an amplification correction unit 121 for performing an amplification correction to make the amplification factor constant regardless of the reception depth with respect to the digital RF signal output from the transmission / reception unit 3, and a fast Fourier transform to the digital RF signal subjected to the amplification correction
- Frequency analysis unit 122 that calculates a frequency spectrum by performing (FFT) and performing frequency analysis, and approximation processing based on regression analysis and ultrasonic waves propagate to the frequency spectrum of each location calculated by frequency analysis unit 122
- a feature amount extraction unit 123 that extracts the feature amount of the specimen by performing attenuation correction processing that reduces the contribution of attenuation generated according to the reception depth and frequency of the ultrasonic wave.
- FIG. 9 is a diagram illustrating the relationship between the reception depth and the amplification factor in the amplification process performed by the amplification correction unit 121.
- the amplification rate ⁇ (dB) in the amplification process performed by the amplification correction unit 121 takes the maximum value ⁇ th ⁇ 0 when the reception depth z is zero, and the reception depth z is zero to the threshold value z th. Decreases linearly until reaching 0 and is zero when the reception depth z is greater than or equal to the threshold z th .
- the amplification correction unit 121 amplifies and corrects the digital RF signal with the amplification factor determined in this way, thereby canceling the influence of the STC correction in the STC correction unit 33 and outputting a signal with a constant amplification rate ⁇ th. .
- the relationship between the reception depth z and the amplification factor ⁇ performed by the amplification correction unit 121 is different depending on the relationship between the reception depth and the amplification factor in the STC correction unit 33.
- the STC correction is a correction that uniformly amplifies the amplitude of the analog signal waveform over the entire frequency band. For this reason, when generating a B-mode image using the amplitude of ultrasonic waves, a sufficient effect can be obtained by performing STC correction, while in the case of calculating the frequency spectrum of ultrasonic waves. However, the influence of attenuation associated with the propagation of ultrasonic waves cannot be accurately eliminated. To solve this problem, when generating a B-mode image, output a reception signal subjected to STC correction, while generating an image based on a frequency spectrum, It is conceivable to perform a different new transmission and output a received signal not subjected to STC correction.
- the amplification correction unit 121 corrects the amplification factor.
- the frequency analysis unit 122 calculates a frequency spectrum at a plurality of locations (data positions) on the sound ray by performing fast Fourier transform on an FFT data group having a predetermined data amount for each sound ray (line data). The calculation result by the frequency analysis unit 122 is obtained as a complex number and stored in the storage unit 14.
- the frequency spectrum shows different tendencies depending on the tissue properties of the specimen. This is because the frequency spectrum has a correlation with the size, density, acoustic impedance, and the like of the specimen as a scatterer that scatters ultrasonic waves.
- the “tissue property” is, for example, any of cancer, endocrine tumor, mucinous tumor, normal tissue, vessel, and the like.
- FIG. 10 is a diagram illustrating an example of a frequency spectrum calculated by the frequency analysis unit 122. Specifically, a frequency spectrum obtained by performing a fast Fourier transform on the FFT data group is expressed by intensity I (f, z) and phase ⁇ (f, z) with frequency f and reception depth as a function of z. The spectrum of intensity I (f, z) is shown.
- intensity refers to any of parameters such as voltage, power, sound pressure, and acoustic energy.
- the horizontal axis f is the frequency
- the vertical axis I is the intensity
- the reception depth z is constant.
- the feature amount extraction unit 123 depends on the ultrasonic reception depth and frequency with respect to the approximation unit 124 that calculates the approximate expression of the frequency spectrum calculated by the frequency analysis unit 122 by regression analysis, and the approximate expression calculated by the approximation unit 124.
- an attenuation correction unit 125 that extracts a characteristic amount of the frequency spectrum by performing attenuation correction processing that reduces the contribution of attenuation of ultrasonic waves.
- the approximating unit 124 extracts a feature amount before attenuation correction (hereinafter referred to as a pre-correction feature amount) that characterizes the approximated primary equation by approximating the frequency spectrum with a linear equation (regression line) by regression analysis. Specifically, the approximating unit 124 extracts the slope a 0 and the intercept b 0 of the linear expression as the pre-correction feature quantity.
- a straight line L 10 illustrated in FIG. 10 is a straight line corresponding to a linear expression approximated by the approximation unit 124.
- the inclination a 0 has a correlation with the size of the ultrasonic scatterer, and it is generally considered that the larger the scatterer, the smaller the inclination.
- the intercept b 0 has a correlation with the size of the scatterer, the difference in acoustic impedance, the density (concentration) of the scatterer, and the like. Specifically, it is considered that the intercept b 0 has a larger value as the scatterer is larger, a larger value as the acoustic impedance is larger, and a larger value as the density (concentration) of the scatterer is larger.
- the intensity at the center frequency f M (hereinafter simply referred to as “intensity”) c 0 is an indirect parameter derived from the slope a 0 and the intercept b 0 , and gives the spectrum intensity at the center in the effective frequency band. Therefore, the intensity c 0 is considered to have a certain degree of correlation with the brightness of the B-mode image in addition to the size of the scatterer, the difference in acoustic impedance, and the density of the scatterer.
- the approximate polynomial calculated by the feature quantity extraction unit 123 is not limited to a linear expression, and it is possible to use a quadratic or higher approximate polynomial.
- the value of the pre-correction feature value is the same regardless of the type of the ultrasound probe 2.
- the frequency spectrum referred to in the first embodiment is used to describe the case where two different types of ultrasonic probes 2A and 2B are used.
- description will be made using the intercept b 0 and the intensity c 0 as the pre-correction feature quantity.
- FIG. 11 is a diagram illustrating frequency spectra before and after correction by the reception signal correction unit 32 when the ultrasound probe 2A is used. Specifically, spectrum C 7 is before reception signal correction, and spectrum C 8 is after reception signal correction.
- FIG. 12 is a diagram illustrating frequency spectra before and after correction by the reception signal correction unit 32 when the ultrasonic probe 2B is used. Specifically, spectrum C 9 is before reception signal correction, and spectrum C 8 is after reception signal correction.
- FIG. 13 is a diagram in which pairs of feature amounts of the spectra C 7 to C 9 shown in FIGS. 11 and 12 are plotted in a feature amount space (b 0 , c 0 ), respectively.
- a certain point B (b 2 , c 2 ) is generally a different point on the feature amount space.
- the set of corrected feature values (b 0 , c 0 ) is the spectrum before correction. Regardless, the point is C (b 3 , c 3 ).
- the pre-correction feature amounts of the frequency spectrum of the received signal are identical because the frequency spectrum depending on the type of the ultrasound probe 2 when the transmission drive wave generation unit 31 generates the transmission drive wave.
- the reception signal correction unit 32 eliminates the influence of the frequency spectrum depending on the type of the ultrasound probe 2 on the reception signal.
- the frequency spectrum of the received signal differs depending on the type of the ultrasound probe 2. Therefore, according to the second embodiment, it is possible to reliably eliminate the influence due to the difference in the type of the ultrasound probe 2, and it is possible to realize more accurate feature extraction.
- ⁇ is the attenuation rate
- z is the ultrasonic reception depth
- f is the frequency.
- the attenuation amount A (f, z) is proportional to the frequency f.
- the value of the attenuation rate ⁇ may be set or changed by input from the input unit 5.
- FIG. 14 is a diagram illustrating a straight line corresponding to the feature amount corrected by the attenuation correction unit 125.
- the image processing unit 13 generates feature amount image data for displaying information corresponding to the feature amount extracted by the B-mode image data generation unit 41 and the feature amount extraction unit 123 according to one of a plurality of display methods.
- An image data generation unit 131 An image data generation unit 131.
- the feature amount image data generation unit 131 determines the information assigned to each pixel in the feature amount image data according to the data amount of the FFT data group when the frequency analysis unit 122 calculates the frequency spectrum. Specifically, for example, information corresponding to the feature amount of the frequency spectrum calculated from the FFT data group is assigned to the pixel region corresponding to the data amount of one FFT data group. In the second embodiment, the number of feature amounts used when generating feature amount image data can be arbitrarily set.
- the storage unit 14 includes a correction information storage unit 141 in addition to the ultrasound probe information storage unit 71, the amplification factor information storage unit 72, and the window function storage unit 73.
- the amplification factor information storage unit 72 is a relationship between the amplification factor and the reception depth that is referred to when the STC correction unit 33 performs the amplification process (for example, the relationship illustrated in FIG. 6), and when the amplification correction unit 121 performs the amplification correction process.
- the relationship (for example, the relationship shown in FIG. 9) between the amplification factor and the reception depth referred to respectively is stored as amplification factor information.
- the correction information storage unit 141 stores information related to attenuation correction including Expression (1).
- the storage unit 14 is realized by using a ROM in which an operation program of the ultrasonic observation apparatus 11, a program for starting a predetermined OS, and the like are stored in advance, and a RAM in which calculation parameters and data of each process are stored.
- FIG. 15 is a flowchart showing an outline of processing of the ultrasonic observation apparatus 11 having the above configuration.
- the processes in steps S11 to S17 correspond to steps S1 to S7 in the flowchart shown in FIG. Hereinafter, the process after step S18 is demonstrated.
- step S18 the amplification correction unit 121 performs amplification correction on the signal output from the transmission / reception unit 3 so that the amplification factor is constant regardless of the reception depth (step S18).
- the amplification correction unit 121 performs amplification correction based on, for example, the relationship between the amplification factor and the reception depth shown in FIG.
- the frequency analysis unit 122 calculates a frequency spectrum by performing frequency analysis by FFT calculation (step S19).
- step S19 the process (step S19) performed by the frequency analysis unit 122 will be described in detail with reference to the flowchart shown in FIG.
- the frequency analysis unit 122 sets a counter k for identifying a sound ray to be analyzed as k 0 (step S31).
- FIG. 17 is a diagram schematically showing a data array of one sound ray.
- a white or black rectangle means one piece of data.
- the sound ray SR k is discretized at a time interval corresponding to a sampling frequency (for example, 50 MHz) in A / D conversion performed by the transmission / reception unit 3.
- FIG. 17 shows the case where the first data position of the sound ray SR k is set as the initial value Z (k) 0 , the position of the initial value can be arbitrarily set.
- the frequency analysis unit 122 acquires the FFT data group at the data position Z (k) (step S33), and applies the window function stored in the window function storage unit 73 to the acquired FFT data group (step S34). ). In this way, by applying the window function to the FFT data group, it is possible to avoid the FFT data group from becoming discontinuous at the boundary and to prevent the occurrence of artifacts.
- the frequency analysis unit 122 determines whether or not the FFT data group at the data position Z (k) is a normal data group (step S35).
- the FFT data group needs to have a power number of 2 data.
- the number of data in the FFT data group is 2 n (n is a positive integer).
- the normal FFT data group means that the data position Z (k) is the 2 n-1 th position from the front in the FFT data group.
- the FFT data groups F 2 and F 3 are both normal.
- step S35 If the result of determination in step S35 is that the FFT data group at the data position Z (k) is normal (step S35: Yes), the frequency analysis unit 122 proceeds to step S37 described later.
- step S35 If the result of determination in step S35 is that the FFT data group at the data position Z (k) is not normal (step S35: No), the frequency analysis unit 122 inserts zero data as much as the deficiency into the normal FFT data group. Generate (step S36).
- the FFT function group determined to be not normal in step S35 is subjected to a window function before adding zero data. For this reason, discontinuity of data does not occur even if zero data is inserted into the FFT data group.
- step S36 the frequency analysis unit 122 proceeds to step S37 described later.
- step S37 the frequency analysis unit 122 obtains a frequency spectrum composed of complex numbers by performing an FFT operation using the FFT data group (step S37). As a result, for example, a spectrum C 11 as shown in FIG. 10 is obtained.
- the frequency analysis unit 122 changes the data position Z (k) by the step width D (step S38).
- the step width D is stored in the storage unit 14 in advance.
- the step width D is desirably matched with the data step width used when the B-mode image data generation unit 41 generates the B-mode image data.
- a value larger than the data step width may be set.
- the frequency analysis unit 122 determines whether or not the data position Z (k) is larger than the maximum value Z (k) max in the sound ray SR k (step S39). If the data position Z (k) is greater than the maximum value Z (k) max (step S39: Yes), the frequency analysis section 122 is increased by one counter k (step S40). On the other hand, when the data position Z (k) is equal to or less than the maximum value Z (k) max (step S39: No), the frequency analysis unit 122 returns to step S33.
- the frequency analysis unit 122 performs an FFT operation on [ ⁇ (Z (k) max ⁇ Z (k) 0 ) / D ⁇ +1] FFT data groups for the sound ray SR k .
- [X] represents the maximum integer not exceeding X.
- step S40 the frequency analysis unit 122 determines whether the counter k is greater than the maximum value k max (step S41). When the counter k is greater than k max (step S41: Yes), the frequency analysis unit 122 ends a series of FFT processing. On the other hand, when the counter k is equal to or less than k max (step S41: No), the frequency analysis unit 122 returns to step S32.
- the frequency analysis unit 122 performs the FFT operation a plurality of times for each of (k max ⁇ k 0 +1) sound rays.
- the frequency analysis unit 122 performs frequency analysis processing on all the areas where the ultrasonic signal is received, a setting input of a specific region of interest is received by the input unit 5 in advance, You may make it perform a frequency analysis process only within the region of interest.
- the approximating unit 124 extracts a pre-correction feature quantity by performing regression analysis on the frequency spectrum calculated by the frequency analyzing unit 122 as an approximating process (step S20). Specifically, the approximating unit 124 calculates a linear expression that approximates the intensity I (f, z) of the frequency spectrum in the frequency spectrum frequency band f L ⁇ f ⁇ f H by regression analysis. A characteristic gradient a 0 and an intercept b 0 (, intensity c 0 ) are extracted as pre-correction feature values. Linear L 10 shown in FIG. 10, in step S20, which is an example of a regression line obtained by performing the pre-correction feature amount extraction processing for the spectrum C 11.
- the attenuation correction unit 125 performs an attenuation correction process on the pre-correction feature quantity extracted by the approximation unit 124 (step S21).
- the data sampling frequency is 50 MHz
- the data sampling time interval is 20 (nsec).
- the sound speed is 1530 (m / sec)
- the data position Z is 0 using the data step number n and the data step width D. 0153 nD (mm).
- the attenuation correction unit 125 substitutes the value of the data position Z obtained in this way into the reception depth z of the above-described equations (2) to (4), so that the slope a and the intercept b ( , Intensity c) is calculated.
- a straight line L 11 shown in FIG. 14 can be given.
- Steps S20 and S21 described above constitute a feature quantity extraction step in which the feature quantity extraction unit 123 extracts at least one feature quantity from the frequency spectrum by approximating the frequency spectrum.
- the feature amount image data generation unit 131 generates feature amount image data using the feature amount extracted in the feature amount extraction step (steps S20 and S21) (step S22).
- the display unit 6 displays the B mode image generated by the B mode image data generation unit 41 and / or the feature amount image generated by the feature amount image data generation unit 131 (step S23).
- the display unit 6 may display either one of the B mode image and the feature amount image, may display the B mode image and the feature amount image side by side, or may display the B mode image and the feature amount image. May be superimposed and displayed.
- the mixing ratio of the B-mode image and the feature amount image may be changed by an input from the input unit 5.
- the ultrasonic observation apparatus 11 ends a series of processes. Note that the ultrasound observation apparatus 11 may periodically repeat the processes of steps S11 to S23.
- the processing for eliminating the influence according to the type of the ultrasonic probe is performed on both the transmission drive wave and the reception signal.
- the processing for eliminating the influence according to the type of the ultrasonic probe is performed on both the transmission drive wave and the reception signal.
- a transmission drive wave having a frequency spectrum having a larger value as the attenuation amount when converted into a transmission echo by the ultrasonic probe is larger is generated, and the received signal is generated. Since the correction is performed for each frequency based on the attenuation amount, the influence of the difference in characteristics depending on the type of the ultrasonic probe can be surely eliminated.
- the feature amount is extracted by performing frequency analysis, but the feature amount is excluded from the feature amount according to the type of the ultrasound probe. Therefore, according to the second embodiment, even when a quantitative evaluation of an ultrasonic image is performed, the type of ultrasonic probe is not affected.
- the feature quantity extraction unit 123 may calculate the approximate expression of the corrected frequency spectrum after performing the attenuation correction of the frequency spectrum.
- FIG. 18 is a diagram schematically illustrating an outline of the attenuation correction process performed by the attenuation correction unit 125. As shown in FIG. 18, the attenuation correction unit 125 attenuates the expression (1) to the intensity I (f, z) at all frequencies f (f L ⁇ f ⁇ f H ) in the band for the spectrum C 11.
- control unit 8 may collectively perform the amplification correction process by the amplification correction unit 121 and the attenuation correction process by the attenuation correction unit 125. This process is equivalent to performing the amplification correction process in step S18 of FIG. 15 and changing the definition of the attenuation amount of the attenuation correction process in step S21 of FIG. 15 to the following equation (6).
- a ′ 2 ⁇ zf + ⁇ (z) (6)
- ⁇ (z) on the right side is the difference between the amplification factors ⁇ and ⁇ 0 at the reception depth z
- ⁇ (z) ⁇ ⁇ ( ⁇ th ⁇ 0 ) / z th ⁇ z + ⁇ th ⁇ 0 (z ⁇ z th ) (7)
- ⁇ (z) 0 (z > z th) ⁇ (8) It is expressed.
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Abstract
Description
図1は、本発明の実施の形態1に係る超音波観測装置の構成を示すブロック図である。同図に示す超音波観測装置1は、超音波を用いて診断対象である検体を観測するための装置である。超音波観測装置1は、外部へ超音波の送信エコーを出力するとともに、外部で反射された超音波の受信エコーを受信して電気的な受信信号に変換する超音波探触子2と、超音波探触子2との間で電気信号の送受信を行う送受信部3と、受信信号に対応する画像データの生成を行う画像処理部4と、キーボード、マウス、タッチパネル等のインタフェースを用いて実現され、各種情報の入力を受け付ける入力部5と、液晶または有機EL等からなる表示パネルを用いて実現され、画像処理部4が生成した画像を含む各種情報を表示する表示部6と、超音波探触子2の種類に応じた特性を示すパラメータを含む超音波観測に必要な各種情報を記憶する記憶部7と、超音波観測装置1の動作制御を行う制御部8と、を備える。超音波観測装置1は、先端部に超音波探触子2が設けられるスコープと、スコープの基端が着脱可能に接続され、超音波探触子2以外の上記部位が設けられる処理装置(プロセッサ)とによって構成される。
Bモード画像データ生成部41は、デジタル信号に対してバンドパスフィルタ、対数変換、ゲイン処理、コントラスト処理等の公知の技術を用いた信号処理を行うとともに、表示部6における画像の表示レンジに応じて定まるデータステップ幅に応じたデータの間引き等を行うことによってBモード画像データを生成する。
超音波探触子情報記憶部71は、上述したように、超音波探触子2の種類と、その超音波探触子2が送信駆動波を送信エコーに変換したり受信エコーを受信信号に変換したりする際にスペクトルに生じる減衰量とを関連付けたものをパラメータとして記憶する。
増幅率情報記憶部72は、STC補正部33が増幅処理を行う際に参照する増幅率と受信深度との関係(例えば、図2に示す関係)を増幅率情報として記憶する。
窓関数記憶部73は、Hamming、Hanning、Blackmanなどの窓関数のうち少なくともいずれか1つの窓関数を記憶する。
図7において、送信駆動波生成部31は送信駆動波を生成して超音波探触子2へ出力する(ステップS1)。この送信駆動波のスペクトルは、例えば超音波探触子2Aの場合には、図3(a)に示すスペクトルC4である。また、超音波探触子2Bの場合、送信駆動波のスペクトルは、図3(b)に示すスペクトルC5である。
図8は、本発明の実施の形態2に係る超音波観測装置の構成を示すブロック図である。同図に示す超音波観測装置11は、超音波探触子2と、送受信部3と、入力部5と、表示部6と、制御部8と、電気的な受信信号に対して所定の演算を施す演算部12と、電気的なエコー信号に対応する画像データの生成を行う画像処理部13と、記憶部14と、を備える。なお、上述した超音波観測装置1が有する構成要素と同様の機能を有する構成要素には、超音波観測装置1と同じ符号を付してある。
A(f,z)=2αzf ・・・(1)
と表される。ここで、αは減衰率であり、zは超音波の受信深度であり、fは周波数である。式(1)からも明らかなように、減衰量A(f,z)は、周波数fに比例している。減衰率αの具体的な値は、観察対象が生体である場合、0.0~1.0(dB/cm/MHz)、より好ましくは0.3~0.7(dB/cm/MHz)であり、生体の部位に応じて定まる。例えば、観察対象が膵臓である場合には、α=0.6(dB/cm/MHz)と定めることがある。なお、本実施の形態において、減衰率αの値を入力部5からの入力によって設定または変更可能な構成としてもよい。
a=a0+2αz ・・・(2)
b=b0 ・・・(3)
c=c0+2αzfM(=afM+b) ・・・(4)
式(2)、(4)からも明らかなように、減衰補正部125は、超音波の受信深度zが大きいほど、補正量が大きい補正を行う。また、式(3)によれば、切片に関する補正は恒等変換である。これは、切片が周波数0(Hz)に対応する周波数成分であって減衰の影響を受けないためである。
I=af+b=(a0+2αz)f+b0 ・・・(5)
で表される。この式(5)からも明らかなように、直線L11は、直線L10と比較して、傾きが大きく、かつ切片が同じである。
増幅率情報記憶部72は、STC補正部33が増幅処理を行う際に参照する増幅率と受信深度との関係(例えば、図6に示す関係)および増幅補正部121が増幅補正処理を行う際にそれぞれ参照する増幅率と受信深度との関係(例えば、図9に示す関係)を増幅率情報として記憶する。
補正情報記憶部141は、式(1)を含む減衰補正に関連した情報を記憶する。
ここまで、本発明を実施するための形態を説明してきたが、本発明は、上述した一実施の形態によってのみ限定されるべきものではない。例えば、本発明において、特徴量抽出部123が、周波数スペクトルの減衰補正を行ってから、補正後の周波数スペクトルの近似式を算出するようにしてもよい。図18は、減衰補正部125が行う減衰補正処理の概要を模式的に示す図である。図18に示すように、減衰補正部125は、スペクトルC11に対し、帯域内のすべての周波数f(fL<f<fH)における強度I(f,z)に式(1)の減衰量A(f,z)をそれぞれ加える補正(I(f,z)→I(f,z)+A(f,z))を行う。これにより、超音波の伝播に伴う減衰の寄与を削減した新たなスペクトルC12が得られる。近似部124は、スペクトルC12に対して回帰分析を行うことにより、特徴量を抽出する。この場合に抽出される特徴量は、図18に示す直線L11の傾きa、切片b(、強度c)である。この直線は、図14に示す直線L11と同じである。
A'=2αzf+γ(z) ・・・(6)
ここで、右辺のγ(z)は、受信深度zにおける増幅率βとβ0との差であり、
γ(z)=-{(βth-β0)/zth}z+βth-β0 (z≦zth) ・・・(7)
γ(z)=0 (z>zth) ・・・(8)
と表される。
2 超音波探触子
3 送受信部
4、13 画像処理部
5 入力部
6 表示部
7 記憶部
8 制御部
12 演算部
14 記憶部
21 信号変換部
31 送信駆動波生成部
32 受信信号補正部
33 STC補正部
41 Bモード画像データ生成部
71 超音波探触子情報記憶部
72 増幅率情報記憶部
73 窓関数記憶部
81 超音波探触子判定部
121 増幅補正部
122 周波数解析部
123 特徴量抽出部
124 近似部
125 減衰補正部
131 特徴量画像データ生成部
141 補正情報記憶部
Claims (10)
- 電気的な送信駆動波を超音波の送信エコーに変換し、該送信エコーを検体に対して送信するとともに、前記検体によって反射された受信エコーを受信して電気的な受信信号に変換する超音波探触子と、
前記超音波探触子の種類に応じた特性を与えるパラメータであって前記送信駆動波の生成および前記受信信号の補正に必要なパラメータを記憶する記憶部と、
前記記憶部が記憶する前記パラメータを参照し、前記送信エコーの所定の周波数帯域における周波数スペクトルが前記超音波探触子の種類によらず同じとなるように、前記超音波探触子の種類に応じた前記送信駆動波を生成する送信駆動波生成部と、
前記記憶部が記憶する前記パラメータを参照し、前記受信信号に対して前記超音波探触子の種類に応じた補正を行う受信信号補正部と、
前記受信信号補正部が補正した前記受信信号を用いて画像データを生成する画像処理部と、
を備えたことを特徴とする超音波観測装置。 - 前記送信駆動波生成部は、
前記超音波探触子によって前記送信エコーに変換される際の減衰量が大きい周波数ほど値が大きい周波数スペクトルを有する前記送信駆動波を生成し、
前記受信信号補正部は、
前記受信信号に対して前記減衰量をもとに周波数ごとの補正を行うことを特徴とする請求項1に記載の超音波観測装置。 - 前記記憶部は、
前記超音波探触子によって前記送信駆動波または前記受信エコーが変換された場合の周波数スペクトルにおける周波数ごとの減衰量を前記超音波探触子の種類と対応づけて前記パラメータとして記憶し、
前記送信駆動波生成部は、
前記送信エコーとして出力すべき所定の周波数帯域の周波数スペクトルに対して、前記記憶部が記憶する前記減衰量を周波数ごとに加えることによって前記送信駆動波を生成し、
前記受信信号補正部は、
前記超音波探触子から受信した受信信号の周波数スペクトルに対して、前記記憶部が記憶する前記減衰量を周波数ごとに加えることによって前記受信信号の補正を行うことを特徴とする請求項1または2に記載の超音波観測装置。 - 前記超音波探触子は、互いに種類が異なる複数の超音波探触子から選択可能であることを特徴とする請求項1~3のいずれか一項に記載の超音波観測装置。
- 前記超音波探触子が受信した超音波の周波数を解析することによって周波数スペクトルを算出する周波数解析部と、
前記周波数解析部が算出した周波数スペクトルを近似することによって前記周波数スペクトルから少なくとも1つの特徴量を抽出する特徴量抽出部と、
をさらに備え、
前記画像処理部は、
前記特徴量抽出部が抽出した特徴量に応じた特徴量画像データを生成する特徴量画像データ生成部を有することを特徴とする請求項1~4のいずれか一項に記載の超音波観測装置。 - 前記特徴量抽出部は、
前記周波数スペクトルの近似処理を行う前または行った後に、超音波の受信深度および周波数に応じて発生する減衰の寄与を削減する減衰補正処理を行うことを特徴とする請求項5に記載の超音波観測装置。 - 前記特徴量抽出部は、
回帰分析によって近似対象の周波数スペクトルを多項式で近似することを特徴とする請求項5または6に記載の超音波観測装置。 - 前記特徴量抽出部は、
前記近似対象の周波数スペクトルを一次式で近似し、前記一次式の傾き、前記一次式の切片、および前記傾きと前記切片と前記周波数スペクトルの周波数域に含まれる特定の周波数とを用いて定まる強度、の少なくとも1つを特徴量として抽出することを特徴とする請求項7に記載の超音波観測装置。 - 電気的な送信駆動波を超音波の送信エコーに変換し、該送信エコーを検体に対して送信するとともに、前記検体によって反射された受信エコーを受信して電気的な受信信号に変換する超音波探触子の種類に応じた特性を与えるパラメータであって前記送信駆動波の生成および前記受信信号の補正に必要なパラメータを記憶する記憶部から前記パラメータを参照し、前記超音波探触子の種類に応じた前記送信駆動波を送信駆動波生成部によって生成する送信駆動波生成ステップと、
前記記憶部が記憶する前記パラメータを参照し、前記受信信号に対して前記超音波探触子の種類に応じた補正を行う受信信号補正ステップと、
前記受信信号補正ステップで補正した前記受信信号を用いて画像データを生成する画像処理ステップと、
を有することを特徴とする超音波観測装置の作動方法。 - 電気的な送信駆動波を超音波の送信エコーに変換し、該送信エコーを検体に対して送信するとともに、前記検体によって反射された受信エコーを受信して電気的な受信信号に変換する超音波探触子の種類に応じた特性を与えるパラメータであって前記送信駆動波の生成および前記受信信号の補正に必要なパラメータを記憶する記憶部から前記パラメータを参照し、前記超音波探触子の種類に応じた前記送信駆動波を送信駆動波生成部によって生成する送信駆動波生成ステップと、
前記記憶部が記憶する前記パラメータを参照し、前記受信信号に対して前記超音波探触子の種類に応じた補正を行う受信信号補正ステップと、
前記受信信号補正ステップで補正した前記受信信号を用いて画像データを生成する画像処理ステップと、
をコンピュータに実行させることを特徴とする超音波観測装置の作動プログラム。
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