JP2014083360A - Ultrasonograph - Google Patents

Abstract

An object of the present invention is to provide an ultrasonic diagnostic apparatus capable of simultaneous measurement in an azimuth direction and a depth direction when performing measurement using a CWD method in ultrasonic diagnosis.
A plurality of first transmission waves having different center frequencies are frequency-modulated and combined to generate a second transmission wave, the second transmission wave is continuously transmitted, and the frequency-modulated first Receiving a reflected wave corresponding to the second transmitted wave, generating a first received signal based on the reflected wave, and using a bandpass filter provided for each center frequency corresponding to the bandwidth related to frequency modulation, A plurality of second received signals corresponding to a plurality of azimuth directions are extracted from one received signal, each second received signal is demodulated, each demodulated second received signal is subjected to frequency analysis, and each azimuth direction is extracted. The distance information regarding the depth direction of each is calculated, and an ultrasonic image is generated and displayed based on the distance information regarding the depth direction of each azimuth direction.
[Selection] Figure 7

Description

  The present invention relates to an ultrasonic diagnostic apparatus that enables simultaneous measurement in the azimuth direction and the depth direction when performing continuous wave Doppler (CWD) measurement using continuous ultrasonic waves (CW).

  The ultrasonic diagnostic apparatus radiates an ultrasonic pulse generated from a vibrator provided in an ultrasonic probe into a subject and receives an ultrasonic reflected wave generated by a difference in acoustic impedance of the subject tissue by the vibrator. To collect biological information. Real-time display of image data is possible with a simple operation by simply bringing an ultrasonic probe into contact with the body surface. For example, moving objects such as the heart can be observed. Widely used for functional diagnosis.

  In ultrasonic diagnosis using such an ultrasonic diagnostic apparatus, there is a blood flow velocity measuring method called CWD method. This method measures blood flow velocity by performing Doppler imaging using continuous wave ultrasonic waves, and is generally used for measurement of high-speed blood flow in the deep part.

JP 2008-63829 A JP 2005-23391 A

  Unlike the PWD method, the conventional CWD method has no distance resolution. Also, multiple beams cannot be collected simultaneously. The former is likely to be able to cope with the recent study of the FMCW technology, but the latter is difficult to solve because of the fundamental problem that the beam is fluctuated during continuous wave transmission.

  In view of the above circumstances, an ultrasonic diagnosis that enables simultaneous measurement with resolution in the azimuth direction and depth direction (distance direction) when performing measurement using the CWD method in ultrasonic diagnosis. The object is to provide a device.

  An ultrasonic diagnostic apparatus according to an embodiment generates a second transmission wave by frequency-modulating and synthesizing a plurality of first transmission waves having different center frequencies via an ultrasonic probe, and generating the second transmission wave. And a reflected unit corresponding to the second modulated wave modulated by the frequency probe via the ultrasonic probe and a first received signal based on the reflected wave. A plurality of second receptions corresponding to a plurality of azimuth directions from the first reception signal using a receiving unit that generates and a band-pass filter provided for each of the center frequencies corresponding to a bandwidth related to the frequency modulation. A filter unit that extracts a signal; a demodulation unit that demodulates each second received signal; and a frequency analysis of each demodulated second received signal to calculate distance information about the depth direction in each azimuth direction An ultrasonic unit comprising: an analysis unit; an image generation unit that generates an ultrasonic image based on distance information about the depth direction of each azimuth direction; and a display unit that displays the ultrasonic image. It is a diagnostic device.

  As described above, according to the present invention, an ultrasonic diagnostic apparatus capable of simultaneous measurement with resolution in the azimuth direction and depth direction (distance direction) is realized when performing measurement using the CWD method in ultrasonic diagnosis. can do.

FIG. 1 shows a block diagram of an ultrasonic diagnostic apparatus 1 according to this embodiment. FIG. 2 is a diagram showing a configuration of the ultrasonic transmission unit 21 that realizes the frequency-divided FMCWD function. FIG. 3 is a diagram for explaining a transmission process according to the frequency-divided FMCWD function. FIG. 4 is a diagram for explaining transmission processing according to the frequency-divided FMCWD function. FIG. 5 is a diagram for explaining a transmission beam according to the frequency-divided FMCWD function. FIG. 6 is a diagram showing a configuration of the ultrasonic wave receiving unit 22 that realizes the frequency-divided FMCWD function. FIG. 7 is a diagram for explaining reception processing according to the frequency-divided FMCWD function. FIG. 8 is a conceptual diagram for explaining demodulation processing according to this application example. FIGS. 9A and 9B are diagrams for explaining the effect of the demodulation processing according to the application example. FIG. 10 is a diagram for explaining the effect of the demodulation processing according to the application example.

  Hereinafter, embodiments will be described with reference to the drawings. In the following description, components having substantially the same function and configuration are denoted by the same reference numerals, and redundant description will be given only when necessary.

  FIG. 1 shows a block diagram of an ultrasonic diagnostic apparatus 1 according to this embodiment. As shown in the figure, the ultrasonic diagnostic apparatus 1 includes an ultrasonic probe 12, an input device 13, a monitor 14, an ultrasonic transmission unit 21, an ultrasonic reception unit 22, a B-mode processing unit 23, a Doppler / blood flow detection. A unit 24, an image generation unit 25, an image memory 26, a display processing unit 27, a control processor (CPU) 28, a storage unit 29, and an interface unit 30 are provided. Hereinafter, the function of each component will be described.

  The ultrasonic probe 12 is a device (probe) that transmits an ultrasonic wave to a subject and receives a reflected wave from the subject based on the transmitted ultrasonic wave. And a backing layer. The ultrasonic transducer transmits an ultrasonic wave in a desired direction within the scan region based on a drive signal from the ultrasonic transmission unit 21 and converts a reflected wave from the subject into an electric signal. The matching layer is an intermediate layer provided in the ultrasonic transducer for efficiently propagating ultrasonic energy. The backing material prevents ultrasonic waves from propagating backward from the ultrasonic transducer. When ultrasonic waves are transmitted from the ultrasonic probe 12 to the subject P, the transmitted ultrasonic waves are successively reflected by the discontinuous surface of the acoustic impedance of the body tissue and received by the ultrasonic probe 12 as an echo signal. . The amplitude of this echo signal depends on the difference in acoustic impedance at the discontinuous surface that is to be reflected. Further, the echo when the transmitted ultrasonic pulse is reflected by the moving bloodstream undergoes a frequency shift due to the Doppler effect depending on the velocity component in the ultrasonic transmission / reception direction of the moving body.

  The ultrasonic probe 12 has a band in which CWD transmission / reception is possible. Further, it may be either a one-dimensional array probe in which a plurality of ultrasonic transducers are arranged one-dimensionally or a two-dimensional array probe in which a plurality of ultrasonic transducers are arranged two-dimensionally.

  The input device 13 is connected to the device main body 11, and various switches, buttons, and tracks for incorporating various instructions, conditions, region of interest (ROI) setting instructions, various image quality condition setting instructions, etc. from the operator into the device main body 11. It has a ball, mouse, keyboard, etc.

  Based on the video signal from the display processing unit 27, the monitor 14 displays in-vivo morphological information, blood flow information, Doppler waveform for each azimuth direction, and the like.

  The ultrasonic transmission unit 21 and the ultrasonic reception unit 22 execute transmission and reception for realizing a frequency-divided FMCWD function described later. The configurations and operations of the ultrasonic transmission unit 21 and the ultrasonic reception unit 22 will be described in detail later.

  The B-mode processing unit 23 receives the echo signal from the receiving unit 22, performs logarithmic amplification, envelope detection processing, and the like, and generates data in which the signal intensity is expressed by brightness.

  The Doppler / blood flow detection unit 24 extracts and analyzes a blood flow signal from the echo signal received from the reception unit 22 to obtain blood flow information such as a Doppler waveform, average velocity, blood flow data, dispersion, and power. Further, the Doppler / blood flow detection unit 24 detects the Doppler shift frequency for each azimuth direction according to the simultaneous multi-directional CWD function described later, the Doppler waveform for each azimuth direction, the average velocity as blood flow data, the variance, Obtain blood flow information such as power.

  The image generation unit 25 performs a RAW-pixel conversion (or voxel conversion) on the two-dimensional or three-dimensional RAW data received from the B-mode processing unit 23 and the image memory 26, thereby obtaining a two-dimensional or three-dimensional image. Generate data. Further, the image generation unit 25 performs predetermined image processing such as volume rendering, multi-planar reconstruction display (MPR), maximum value projection display (MIP) on the generated image data. . Note that a spatial smoothing may be performed by inserting a two-dimensional filter after the image generation unit 25 for the purpose of noise reduction and image connection.

  The image memory 26 generates two-dimensional or three-dimensional B-mode RAW data using a plurality of B-mode data received from the B-mode processing unit 23, for example.

  The display processing unit 27 executes various types such as dynamic range, brightness (brightness), contrast, γ curve correction, and RGB conversion on various image data generated and processed by the image generation unit 25.

  The control processor 28 has a function as an information processing apparatus (computer) and controls the operation of the main body of the ultrasonic diagnostic apparatus. The control processor 29 reads out a control program for realizing a frequency-divided FMCWD function, which will be described later, from the storage unit 31 and develops it on its own memory, and controls the simultaneous multidirectional CWD, and each direction obtained by the function. Calculations using direction-related Doppler signals (compound, spatial distribution of signal intensity, automatic angle correction, intravascular distribution of blood flow velocity, diagnosis index value, etc.) are executed.

  The storage unit 29 is a control program for realizing a frequency-divided FMCWD function, which will be described later, a diagnostic information (patient ID, doctor's findings, etc.), a diagnostic protocol, transmission / reception conditions, a program for realizing a speckle removal function, A body mark generation program, a conversion table for presetting the range of color data used for imaging for each diagnostic part, and other data groups are stored. Further, it is also used for storing images in an image memory (not shown) as required. Data in the storage unit 29 can be transferred to an external peripheral device via the interface unit 30.

  The interface unit 30 is an interface related to the input device 13, a network, and a new external storage device (not shown). Data such as ultrasonic images and analysis results obtained by the apparatus can be transferred by the interface unit 30 to another apparatus via a network.

(Frequency-divided FMCWD function)
Next, the frequency-divided FMCWD function of the ultrasonic diagnostic apparatus 1 will be described. This function is a technique for realizing CWD having resolution in both the azimuth direction and the distance direction (depth direction). That is, when blood flow measurement is performed by the CWD method, multiple waves (multi-frequency transmission waves) to which different fundamental frequencies are assigned for each azimuth direction of the ultrasonic beam are frequency-modulated for each band from each ultrasonic transducer. Send. In addition, by detecting the Doppler shift frequency of each fundamental frequency from the reflected wave obtained by the frequency-modulated multiplexed wave, the reflected wave from each azimuth direction is discriminated and the reflected wave for each discriminated azimuth direction is discriminated. To achieve resolution in the distance direction.

  FIG. 2 is a diagram illustrating a configuration of the ultrasonic transmission unit 21 that realizes the frequency-divided FMCWD function. The ultrasonic transmission unit 21 includes an original vibration generation unit 21a, a transmission frequency division unit 21b, a chirp wave generation unit 21c, a waveform synthesis unit 21d, and the like.

  The original vibration generating unit 21a repeatedly generates an original vibration waveform having a predetermined frequency fr Hz (period: 1 / fr second). The transmission frequency divider 21b divides the original vibration waveform and generates a basic waveform to which different basic frequencies f1, f2,... FN are assigned according to the azimuth direction.

  The chirp wave generator 21c includes chirp generators 21c-1 to 21c-N corresponding to the respective fundamental frequencies. Each of the chirp generators 21c-1 to 21c-N is sequentially input with a fundamental waveform having a corresponding fundamental frequency from the transmission frequency divider 21b. Each of the chirp generators 21c-1 to 21c-N generates chirp waves having the fundamental frequencies f1, f2,... FN as the center frequencies and the bandwidths Δf1 to ΔfN based on the input basic waveforms. Occur. As a result, as shown in FIGS. 3 and 4, each band is divided by a chirp wave i having a band of fi ± Δfi (where i is a natural number of 2 or more that satisfies 1 ≦ i ≦ N), and is arranged in the N direction. Secure corresponding N beams.

As shown in FIG. 4, the waveform synthesizer 21d receives the chirp waves from each of the chirp generators 21c-1 to 21c-N to perform transmission beam forming, and a transmission waveform VM in which each chirp wave is multiplexed. Is generated. The waveform synthesizing unit 21d gives different phase delays (φ ₁ , φ ₂ , φ ₃ ,..., Φ _N ) to the generated transmission waveform VM for each ultrasonic transducer, and supplies them to each ultrasonic transducer. As a result, as shown in FIG. 5, a chirp wave 1 corresponding to the azimuth direction θ1, a chirp wave 2 corresponding to the azimuth direction θ2,..., A transmission beam in which a chirp wave N corresponding to the azimuth direction θN is multiplexed. Are continuously transmitted from the ultrasonic probe 12. In the example of FIG. 5, an example of a transmission beam having a center deflection angle θ is shown.

  The transmitted transmission beam is reflected in the body of the subject and is received by each ultrasonic transducer as a reflected wave. The receiving unit 22 executes a receiving process according to the frequency-divided FMCWD function described below for each reflected wave received for each ultrasonic transducer.

  FIG. 6 is a diagram showing a configuration of the ultrasonic wave receiving unit 22 that realizes the frequency-divided FMCWD function. The ultrasonic receiving unit 22 includes a bandpass filter array 22a, a demodulator 22b, a frequency analyzer 22c, and the like.

  The bandpass filter array 22a includes bandpass filters 22a-1 to 22a-N corresponding to the frequency bands f1 ± Δf1 to fN ± ΔfN. Each band-pass filter 22a-1 to 22a-N extracts a signal in a corresponding frequency band from the received signal received via the ultrasonic probe 12. Thereby, N chirp waves 1 to N corresponding to N azimuth directions are separated.

  The demodulator 22b includes a plurality of demodulators 22b-1 to 22b-N corresponding to each frequency band. Each demodulator 22b-1 to 22b-N executes a demodulation process on the chirp waves 1 to N having a corresponding frequency band. As a result, as shown in FIG. 7, the power spectrum of N received beams corresponding to the N azimuth directions divided into f1 ± Δf1 to fN ± ΔfN is detected.

  The frequency analysis unit 22c includes N frequency analyzers 22c-1 to 22c-N corresponding to the frequency bands f1 ± Δf1 to fN ± ΔfN. Each frequency analyzer 22c-1 to 22c-N converts the frequency information into distance information by performing a discrete Fourier transform on the demodulated signal output from each demodulator 22b-1 to 22b-N. Thereby, distance information is detected for each azimuth direction (that is, for each of the transmitted and received beams 1 to N).

  The image generation unit 25 uses the distance information for each azimuth direction to generate an ultrasonic image in which Doppler information for each depth in each azimuth direction is mapped. The generated ultrasonic image is displayed on the monitor 14 in a predetermined form after being subjected to a predetermined display process in the display processing unit 27.

(Application examples)
Any demodulation process may be performed in each demodulator 22b-1 to 22b-N. In this application example, the complex conjugate waveform of the chirp wave corresponding to each frequency band generated at the time of transmission is added to the chirp waves 1 to N output from the band pass filters 22a-1 to 22a-N. The demodulation processing to be performed will be described.

  FIG. 8 is a conceptual diagram for explaining demodulation processing according to this application example. As shown in the figure, in the demodulation processing according to this application example, in each demodulator 22b-1 to 22b-N corresponding to each frequency band of the demodulator 22b, each chirp wave before being synthesized by the waveform synthesizer 21d. According to the 60 up (or down) modulation interval, the reverse direction corresponding to the distance direction observation interval converted from the ultrasonic propagation velocity (that is, when the chirp wave before synthesis is up, down, before synthesis) Demodulation is performed by integrating the received reference chirp wave 63 (that is, the complex conjugate waveform of the chirp wave 60) of the chirp wave is up).

  In general, all the reflector intensity information 61 of the corresponding distance direction observation section is included in the detection output of one chirp transmission 60 (up or down) and the single reception detector (τ = 0). Yes. By performing one frequency analysis (discrete Fourier transform: DFT) or the like using the detection output for all observation sections, the distance direction reflection intensity distribution can be detected as a frequency spectrum. This signal processing can greatly reduce the hardware / software scale. At the same time, since the effect of pulse compression is obtained, there is less waveform tailing compared to the pulse method, and a good distance resolution can be obtained.

  FIG. 9A shows a waveform obtained by demodulating the reflected signal from the pin target at the 30 mm position and the 60 mm position with the multi-phase demodulation range fixed at 0 mm, and the unit of the horizontal axis (time axis) is 1 μs. The vertical axis is 0.1 Vpp in full swing. Since the received wave is complex demodulated, waveform A is an I-phase signal and waveform B is a Q-phase signal. FIG. 9B shows the depth in the ± 500 kHz range obtained by applying a Hamming window to the frequency analysis result of the waveform of FIG. 9A, calculating the power spectrum after 128-point FFT, and logarithmically compressing. Is a different spectrum. That is, spectrum C is a component derived from reflection on the probe surface (body surface 0 mm), spectrum D is a reflection component from the pin target at the 30 mm position, and spectrum E is a reflection component from the pin target at the 60 mm position. is there. The vertical axis corresponds to the power dB itself, and the horizontal axis does not correct the FFT output rearrangement, so the frequency increases as the left end goes to the center at 0 Hz, the center is 500 kHz, and the right half is from the center. Negative absolute value decreases and becomes 0 Hz at the right end.

  FIG. 10 shows a comparison profile created from a B-mode image according to the spectrum shown in FIG. 9B, and FMCW A-mode (the number of FFT points is kept as it is, the band is halved and the sensitivity is higher than that in Chapter 3 analysis). Furthermore, it is adapted to the peak position standard. The underwater 30 mm and 40 mm pin target image signals P are obtained by logarithmically compressing the reflected echo power by the normal pulse method for STC correction (gain correction according to distance) for display. On the other hand, the spectrum F obtained by logarithmically compressing the reflected echo power by the FMCW method is not subjected to STC correction, but it can be seen that the pin target at the 30 mm position and the pin target at the 40 mm position can be well separated. From this figure, it can be confirmed that the FMCW method has no tail behind the fixed body due to the pulse compression effect, and that the distance resolution is good despite the continuous wave pencil probe (2 MHz).

  In this embodiment, the analog circuit (BPF or the like) is described in FIG. 2, FIG. 4, FIG. 5, FIG. 6, etc., but a DA converter or AD converter that converts an analog signal and a digital signal is used. If the sampling frequency is sufficiently high, waveform synthesis / separation by digital processing or software is possible.

(effect)
According to this ultrasonic diagnostic apparatus, when blood flow measurement is performed by the CWD method, a multi-frequency transmission wave to which a different fundamental frequency is assigned for each azimuth direction of an ultrasonic beam is transmitted from each ultrasonic transducer for each band. Transmit while modulating. In addition, by detecting the Doppler shift frequency of each fundamental frequency from the reflected wave obtained by the frequency-modulated multi-frequency transmission wave, the reflected wave from each azimuth direction is discriminated and each discriminated azimuth direction is discriminated. By demodulating the reflected wave, the frequency information is converted into distance information. Thereby, also in CDW method, the Doppler information for every depth can be acquired about each azimuth | direction direction (namely, every transmission-and-reception beam 1-N).

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage.

  In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

DESCRIPTION OF SYMBOLS 1 ... Ultrasonic diagnostic apparatus, 12 ... Ultrasonic probe, 13 ... Input device, 14 ... Monitor, 21 ... Ultrasonic transmission unit, 22 ... Ultrasonic reception unit, 23 ... B mode processing unit, 24 ... Doppler / blood flow detection Unit: 25 ... Image generation unit, 26 ... Image memory, 27 ... Display processing unit, 28 ... Control processor, 29 ... Storage unit, 30 ... Interface unit

Claims (3)

A transmission unit that generates a second transmission wave by frequency-modulating and synthesizing a plurality of first transmission waves having different center frequencies via an ultrasonic probe, and continuously transmits the second transmission wave When,
A receiving unit that receives a reflected wave corresponding to the second modulated wave that has been frequency-modulated via the ultrasonic probe and generates a first received signal based on the reflected wave;
A filter unit that extracts a plurality of second received signals corresponding to a plurality of azimuth directions from the first received signal using a bandpass filter provided for each of the center frequencies corresponding to the bandwidth related to the frequency modulation. When,
A demodulation unit for demodulating each second received signal;
An analysis unit for performing frequency analysis on each demodulated second received signal and calculating distance information regarding a depth direction in each azimuth direction;
An image generation unit that generates an ultrasonic image based on distance information regarding the depth direction of each azimuth direction;
A display unit for displaying the ultrasonic image;
An ultrasonic diagnostic apparatus comprising:   2. The ultrasonic diagnostic apparatus according to claim 1, wherein the demodulation unit demodulates each of the second reception signals using a complex conjugate waveform of the plurality of first transmission waves. The demodulation unit performs reverse demodulation corresponding to the distance direction observation section converted from the ultrasonic wave propagation speed according to the modulation sections of the plurality of first transmission waves,
The image generation unit generates the ultrasonic image in which a frequency distribution of a spectrum obtained by frequency analysis corresponding to all observation sections corresponds to a distance direction reflection intensity distribution;
The ultrasonic diagnostic apparatus according to claim 1 or 2.

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