JP5016782B2 - Ultrasonic diagnostic equipment - Google Patents

Description

  The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to an ultrasonic diagnostic apparatus having a function of receiving reflected ultrasonic waves from a plurality of directions substantially simultaneously.

  The ultrasonic diagnostic apparatus radiates an ultrasonic wave generated from a piezoelectric vibration element built in an ultrasonic probe into a subject and receives a reflected wave caused by a difference in acoustic impedance of the subject tissue by the piezoelectric vibrator. It is displayed on the monitor. This diagnosis method is widely used for organ function diagnosis and morphological diagnosis because real-time two-dimensional image data can be easily obtained by a simple operation by simply bringing an ultrasonic probe into contact with the body surface.

  Ultrasound diagnostic methods for obtaining biological information from reflected waves from the tissue or blood cells of a subject have made rapid progress with the development of two major technologies, the ultrasonic pulse reflection method and the ultrasonic Doppler method, and are obtained using the above technology. The B-mode image and the color Doppler image that are obtained are indispensable in today's ultrasound diagnosis.

  In the most popular electronic scanning ultrasonic diagnostic apparatus today, two-dimensional image data is generally obtained by arranging a plurality of piezoelectric vibrating elements in one dimension and controlling the driving of each of these piezoelectric vibrating elements at high speed. Real-time display.

  The color Doppler method scans a predetermined section in a living body with an ultrasonic pulse, and when the ultrasonic wave is irradiated to a moving reflector such as blood (blood cell), the velocity of the reflector (blood flow velocity) The Doppler frequency shift generated in response to the above is captured and imaged. This color Doppler method was initially used to image intracardiac blood flow information with a high blood flow velocity, but today it is also applied to imaging of extremely slow blood flow such as tissue blood flow in abdominal organs. Is becoming possible.

  In order to improve the diagnostic ability in the color Doppler method, excellent measurement accuracy (low flow velocity detection ability and high flow velocity detection ability), temporal resolution, and spatial resolution are required.

  When a moving reflector is irradiated with an ultrasonic pulse and the moving speed of the reflector is measured from the Doppler frequency shift of the reflected wave, conventionally, transmission / reception with ultrasonic waves is predetermined for this reflector. The transmission speed is measured repeatedly based on a series of reflected waves obtained at the observation time Tobs (Tobs = Tr · L).

In this case, the detection capability (low flow velocity detection capability: lower limit value of measurable flow velocity) Vmin for the low flow velocity reflector is a series of reflected waves obtained by the L times of ultrasonic transmission / reception (hereinafter referred to as transmission / reception). Is determined by the characteristics of a filter (for example, an MTI filter) used for detecting a Doppler component from the filter, that is, the cutoff frequency and shoulder characteristics of the filter. At this time, Vmin is a transmission / reception repetition frequency (rate frequency). If fr (fr = 1 / Tr), the following expression (1) is obtained.

On the other hand, the measurable upper limit of flow velocity (high flow velocity detection capability) Vmax is determined by the Nyquist frequency defined by 1/2 of the transmission / reception repetition frequency (rate frequency) fr, and is represented by the following equation (2). However, C is the sound velocity value in the subject, f0 is the center frequency of the received ultrasound, and ξ is the angle between the ultrasound transmission / reception direction and the blood flow direction. When the Doppler frequency shift exceeds the Nyquist frequency, a folding phenomenon occurs in the frequency spectrum of the Doppler signal, making it impossible to accurately measure the blood flow velocity.

  That is, in order to improve the low flow velocity detection capability Vmin, which is the first requirement item in the color Doppler method, it is necessary to set the rate frequency fr low or to increase the number of times of transmission / reception L repeatedly performed in a predetermined direction. In order to improve the high flow rate detection capability Vmax, the rate frequency fr must be set high. However, when the rate frequency fr is increased, the next ultrasonic wave is radiated before the reflected wave from the deep part is received. Therefore, the so-called residual echo is received in which the reflected wave of the adjacent rate section is mixed. Problem arises.

The real-time property, which is the second requirement item, is determined by the number of display images (frame frequency) Fn per unit time, and this frame frequency Fn is expressed by the following equation (3). However, M is the total number in the scanning direction necessary for generating one color Doppler image data, and in order to improve the real-time property, the transmission / reception count L or the total number M in the scanning direction must be set small. .

  Furthermore, in order to improve the spatial resolution that is the third requirement item, it is necessary to increase the total number M in the scanning direction. That is, the frame frequency Fn, the low flow velocity detection capability Vmin, the high flow velocity detection capability Vmax, and the spatial resolution are in a contradictory relationship, and it is difficult to satisfy these simultaneously. Therefore, frame frequency Fn and high flow velocity detection capability Vmax are important for blood flow measurement in the circulatory region, and frame frequency and low flow velocity detection capability Vmin are important for blood flow measurement in the abdomen and peripheral organs. It has been.

  In order to solve such problems, transmission ultrasonic waves are emitted in a predetermined direction of the subject, and reflected waves (reception ultrasonic waves) by the transmission ultrasonic waves are simultaneously transmitted from a plurality of directions adjacent to the predetermined direction. A so-called parallel simultaneous reception method that increases the amount of data received per unit time has been proposed (see, for example, Non-Patent Document 1).

  However, when parallel simultaneous reception is performed, the center axis of the transmission beam is different from the center axis of the reception beam, so that the transmission / reception sensitivity deteriorates when the transmission ultrasonic wave has a strong directivity as in the prior art. Furthermore, when the parallel and simultaneous reception directions are three or more, uniform transmission / reception sensitivity cannot be obtained in the reception direction.

In order to improve such problems, a method of reducing the number (aperture) of elements of an ultrasonic transducer used for one ultrasonic transmission, and the drive signal amplitude of each vibration element are weighted with respect to the arrangement direction. A method of expanding the beam width of the transmission beam has been proposed (see, for example, Patent Document 1).
Toshihiko Kawano et al., “Examination of high frame rate of ultrasonic diagnostic equipment for circulatory organs”, Proceedings of the Japanese Society of Ultrasonic Medicine, Japanese Society of Ultrasonic Medicine, 1989, Vol. 55, p. 727-728 Japanese Patent Laid-Open No. 3-155843 (page 4-6, FIG. 1-9)

  According to the method of Patent Document 1, although the transmission beam width is widened, it is improved from the conventional method (that is, when the transmission beam width of the same level as that in the case where parallel simultaneous reception is not performed), but the converged transmission is performed. Because the beam is used, it is difficult to widen the beam width corresponding to the received beam. For this reason, the distortion of the transmission / reception beam described below (hereinafter referred to as beam bending) and the non-uniformity in the reception sensitivity. Still remains.

  FIG. 17 shows beam bending, which is the first problem of the conventional method or the method of Patent Document 1, and FIG. 18 shows non-uniformity of reception sensitivity, which is the second problem of the above method. Yes.

  FIG. 17A shows a transmission when ultrasonic waves are transmitted in a predetermined direction (a central axis direction of a transmission beam) using a convex scanning ultrasonic probe in which ultrasonic transducers are arranged on a convex surface. The parallel simultaneous reception by a beam (solid line) and a plurality of reception beams (broken lines) formed overlapping with the transmission beam is shown. For the sake of simplicity, this figure shows the reception beams Br-1 and Br-3 corresponding to the end of the transmission beam Bt and the reception beam Br-2 positioned at the center of the transmission beam Bt.

  The transmission ultrasonic waves in the conventional parallel simultaneous reception method are converged to a predetermined position (depth) of the subject as in the case of non-parallel simultaneous reception, and the ultrasonic energy is concentrated in this region. On the other hand, the reception ultrasonic wave is applied with a so-called dynamic convergence method in which the convergence point is sequentially moved in the depth direction corresponding to the reception timing, and a reception beam continuously converged in the depth direction can be formed.

  In such a case, the ultrasonic reception sensitivity is determined by the product of the sound field (transmission sound field) in the transmission beam and the sound field (reception sound field) in the reception beam (that is, the transmission / reception sound field in the transmission / reception beam). Then, in the transmission / reception beam formed by the transmission beam Bt shown in FIG. 17A and the reception beam (for example, reception beam Br-1) positioned at the end of the transmission beam Bt, the transmission sound field in the convergence region is obtained. Has a particularly large effect on the transmitted and received sound field. As a result, as shown in FIG. 17B, beam bending occurs in the center direction of the transmission beam, and a super beam generated by a transmission / reception beam Btr-1 having such a beam bending or a transmission / reception beam Btr-3 (not shown). Image distortion occurs in the sonic image data.

  Next, FIG. 18A schematically shows the transmission sound field, the reception sound field, and the transmission / reception sound field in the parallel simultaneous reception, and the sound pressure of the transmission sound field at the end of the transmission beam is the center. Smaller than part. For this reason, when three or more simultaneous reception directions are set, the magnitude of the transmitted / received sound field (that is, the reception sensitivity) is nonuniform in the scanning direction, and an ultrasonic image generated by the nonuniform transmitted / received sound field. On the data, a light and dark stripe pattern occurs and the image quality deteriorates. In addition, the significant decrease in the reception sensitivity at the end of the transmission beam not only deteriorates the image quality of the B-mode image data, but also makes it difficult to estimate the flow velocity value, dispersion value, etc. in the generation of color Doppler image data.

  On the other hand, when the transmission sound field is widened in the scanning direction (azimuth direction) as shown in FIG. 18B for the purpose of improving the non-uniformity of the sensitivity described above, useless transmission is performed in an area not involved in the generation of image data. Ultrasonic energy is radiated, not only lowering the reception sensitivity, but also increasing the frequency of occurrence of virtual images (artifacts) due to side lobes and multiple reflections.

  That is, the above-mentioned beam bending, non-uniform reception sensitivity, and further degradation in reception sensitivity degrade the image quality of the ultrasonic image data and reduce its diagnostic ability.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to eliminate beam bending of transmission / reception beams in parallel simultaneous reception, and to reduce reception sensitivity deterioration and non-uniformity in each parallel reception direction. Accordingly, an object of the present invention is to provide an ultrasonic diagnostic apparatus capable of generating ultrasonic image data excellent in real-time property and image quality.

The ultrasonic diagnostic apparatus according to the embodiment includes a plurality of arranged vibration elements that transmit and receive ultrasonic waves.
The ultrasonic probe provided and the intensity of transmitted ultrasonic waves at the array end of the vibration element
Weighting function set lower than the intensity of transmitted ultrasound in the heart and information on the delay time for diffusion
Based on the drive signal having
A transmission means for transmitting a transmitted ultrasonic wave, and a receiver based on an ultrasonic reflected wave obtained by the vibration element.
Parallel reception to obtain a phasing addition signal by forming multiple reception sound lines by phasing and adding the received signal.
And transmitting means for increasing the number of received sound rays in the parallel receiving means.
Accordingly, the diffusion delay time is set so as to increase the degree of diffusion of the transmission ultrasonic wave.
It is a sign .

  According to the present invention, it is possible to improve beam bending of transmission / reception beams in parallel simultaneous reception, and to reduce reception sensitivity and non-uniformity in each parallel reception direction. For this reason, it is possible to generate ultrasonic image data excellent in real-time property and image quality, and the diagnostic ability is greatly improved.

  Embodiments of the present invention will be described below with reference to the drawings.

  The first feature of the first embodiment of the present invention described below is that a predetermined ultrasonic scanning probe having ultrasonic transducers (hereinafter referred to as transducer elements) arranged in a one-dimensional manner on a convex surface is used. When performing parallel simultaneous reception on the imaging region, the width of a plurality of receiving vibration elements (hereinafter referred to as reception aperture width) used for one parallel simultaneous reception on the imaging region is abbreviated. The purpose is to form a diffused transmission beam by driving an oscillating element having the same transmission aperture width.

  Furthermore, the second feature of the present embodiment is that, when driving the vibration element having the transmission aperture width, in the azimuth direction, the drive signal amplitude for the vibration element at the end is controlled based on a preset weighting function. The purpose is to form a flat transmitted sound field.

(Device configuration)
In the following, the configuration of the ultrasonic diagnostic apparatus and the operation of each unit in the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing the overall configuration of the ultrasonic diagnostic apparatus according to the present embodiment, and FIGS. 2 and 4 are block diagrams of a transmission / reception unit and a data generation unit that constitute the ultrasonic diagnostic apparatus. .

  An ultrasonic diagnostic apparatus 100 shown in FIG. 1 includes an ultrasonic probe 20 for convex scanning that includes a vibration element arranged one-dimensionally on a convex surface and transmits / receives ultrasonic waves to / from a subject, and the vibration element. A transmission / reception unit 10 is provided for supplying a driving signal to the selected transmission vibration element and performing phasing addition on the reception signal obtained from the reception vibration element selected in the same manner. A data generation unit 50 that performs signal processing on the received signal obtained from the unit 10 to generate B-mode data and color Doppler data, and stores the data generated in the data generation unit 50 to store the two-dimensional or three-dimensional data A data storage / processing unit 70 for generating B-mode image data and color Doppler image data, and performing desired image processing on the obtained image data, and generation The a display unit 81 for displaying the image data.

  In addition, the ultrasonic diagnostic apparatus 100 includes a reference signal generator 1 that generates a continuous wave or a rectangular wave having a frequency substantially equal to the center frequency of the transmission ultrasonic wave to the transmission / reception unit 10 or the data generation unit 50, and an operator. An input unit 83 for inputting specimen information, initial setting conditions of the apparatus, various command signals, and the like, and a system control unit 82 for comprehensively controlling each unit of the ultrasonic diagnostic apparatus 100 are provided.

  The ultrasonic probe 20 transmits and receives ultrasonic waves by bringing the front surface into contact with the surface of the subject, and M1 vibrating elements are arranged in a one-dimensional manner in a convex shape on the contact surface with the subject. Yes. This vibration element is an electroacoustic transducer, and has a function of converting an electrical pulse into a transmission ultrasonic wave at the time of transmission, and converting an ultrasonic reflected wave (received ultrasonic wave) into an electric signal (received signal) at the time of reception. Have.

  Next, the transmission / reception unit 10 illustrated in FIG. 2 includes a transmission unit 2 that supplies a driving signal to M2 (M2 <M1) transmission vibration elements selected by an element selection unit 41 described later, and the element. The receiving unit 3 that performs phasing addition on the received signals obtained from the M3 (M3≈M2) receiving vibrating elements selected by the selecting unit 41, and the transmitting vibrating element and the receiving vibrating element are selected. Then, an element selection unit 41 that connects the transmission unit 2 and the reception unit 3 and an element selection control unit 42 that controls the element selection unit 41 are provided.

  The transmission unit 2 includes a rate pulse generator 11, a transmission delay circuit 12, a drive circuit 13, and a drive signal amplitude control circuit 14. The rate pulse generator 11 is supplied from the reference signal generator 1. By dividing the continuous wave, a rate pulse that determines the repetition period of the transmission ultrasonic wave is generated. The transmission delay circuit 12 gives the rate pulse a delay time for spreading the transmission beam into a predetermined shape. However, the transmission delay circuit 12 is not necessarily required when the relative delay time of the drive signal applied to each of the transmitting vibration elements is zero.

  On the other hand, the drive circuit 13 generates a drive signal for driving the M2 vibrating elements selectively connected by the element selection unit 41 based on the timing of the rate pulse, and the drive signal amplitude control circuit 14 Based on the element selection information from the control unit 42, a predetermined weight is applied to the drive signal amplitude of the transmitting vibration element in the vicinity of the transmission opening end. The details of the weighting function of the drive signal amplitude and the effect in this case will be described later.

  Next, the receiving unit 3 includes a preamplifier 31 composed of M3 channels, an A / D converter 32, a channel selection circuit 33, and M-channel beamformers 34-1 to 34-M. The preamplifier 31 is for amplifying the M3 channel reception signal supplied from the element selection unit 41 to ensure a sufficient S / N. The first stage portion has a high voltage supplied from the drive circuit 13. A limiter circuit (not shown) is provided for protection from the drive signal. The channel selection circuit 33 performs M-stage parallel reception on the M3 channel reception signal amplified to a predetermined size by the preamplifier 31 and converted to a digital signal by the A / D converter 32. Next, the M4 channel adjacent to the M3 channel is selected at M locations, and each of the M received signal groups composed of the M4 channel is supplied to the beamformers 34-1 to 34-M.

  Each of the beam formers 34-1 to 34-M has a delay circuit and an adder circuit (not shown), converted into a digital signal by the A / D converter 32 and converted into a reception signal of the M4 channel selected by the channel selection circuit 33. On the other hand, after adding a delay time for convergence for converging an ultrasonic wave reflected from a predetermined depth, addition synthesis (phased addition) is performed. In this case, by performing so-called dynamic focusing in which the convergence region is sequentially changed to a deep portion with the reception timing, a reception beam having a substantially uniform beam width is formed regardless of the depth.

  Here, a method of selecting the transmitting vibration element, the receiving vibration element and the M4 channel reception signal performed by the element selection unit 41 and the channel selection circuit 33 described above will be described.

  FIG. 3 schematically shows a vibration element selection method and a reception signal selection method for an M4 channel when performing parallel simultaneous reception in a predetermined direction. In FIG. In this example, the number of transmitting vibration elements M2 and the number of receiving vibration elements M3 is 9, the number of channels M4 of the reception signal group selected by the channel selection circuit 33 is 5, and the number of reception signal groups M is 5.

  In FIG. 3, the ultrasonic probe 20 has M1 vibrating elements 22-1 to 22-M1 arranged in a convex shape. Then, for example, the vibration elements 22-X to 22- (X + 8) are selected from the vibration elements 22-1 to 22-M1 by the element selection unit 41, and the transmission unit 2 selects the selected vibration elements for transmission. A drive signal is supplied to 22-X to 22- (X + 8) to radiate transmission ultrasonic waves into the subject. However, in the present embodiment, the transmitting vibration elements 22-X to 22- (X + 8) are driven substantially simultaneously, and the wavefront of the transmitted ultrasonic wave radiated at this time is formed with the same curvature as the vibration element array surface. The

  On the other hand, at the time of reception, the element selection unit 41 selects, for example, the vibration elements 22-X to 22- (X + 8) as reception vibration elements. However, here, a case where the same vibration element as the transmission vibration element is selected as the reception vibration element is shown, but the present invention is not limited to this, and reception sensitivity deterioration due to a decrease in sound pressure at the end of the transmission beam is shown. In order to prevent this, the number of transmission channels M2 may be set slightly larger than the number of reception channels M3.

  The reception signals obtained from the vibration elements 22 -X to 22-(X + 8) selected by the element selection unit 41 are received signals from M4 (M4 = 5) reception vibration elements adjacent in the channel selection circuit 33. The unit is grouped into M (M = 5) received signal groups, and these received signal groups are supplied to the beam formers 34-1 to 34-M.

  That is, the reception signals of the vibration elements 22-X to 22- (X + 4) are supplied to the beam former 34-1, and the vibration elements 22- (X + 1) to 22- (X + 5),. The reception signals of 22 to (X + 8) are supplied to the beam former 34-2,..., The beam former 34-5. Each of the beam formers 34-1 to 34-5 performs phasing addition processing for dynamic focusing on the M4 reception signals supplied from the channel selection circuit 33, and the vibration element 22- (X + 2). Five reception beams centering on 22− (X + 3),... 22− (X + 6) are formed.

  By the transmission / reception method described above, vibration elements 22- (X + 2), 22- (X + 3),... In a transmission beam in a predetermined direction centered on the transmission vibration element 22- (X + 4) and having a convex wavefront. Five reception beams centering on 22− (X + 6) are formed, and five stages of parallel simultaneous reception are performed. In this case, the transmission direction and the reception direction of the ultrasonic waves are set in a direction perpendicular to the arrangement surface of the vibration elements. However, the transmission delay circuit 12 or the beam former 34 gives the beam deflection delay time to the above transmission. It is also possible to set the beam and the reception beam in arbitrary directions. However, in any case, in the parallel simultaneous reception of this embodiment, a plurality (M) of reception beams are formed in the transmission beam.

  Next, referring back to FIG. 1, the data generation unit 50 generates B-mode data by performing signal processing on the M-channel reception signals output from the beam formers 34-1 to 34-M of the reception unit 3 described above. A B-mode data generation unit 4 and a color Doppler data generation unit 5 that processes the received signal to generate color Doppler data are provided.

  4 includes an envelope detector 51 and a logarithmic converter 52. The B-mode data generator 4 of the data generator 50 shown in FIG. The envelope detector 51 performs envelope detection on the reception signals of the M channels output from the beam formers 34-1 to 34-M in the reception unit 3 of the transmission / reception unit 10, and the logarithmic converter 52 B-mode data for M scanning directions (rasters) is generated by relatively emphasizing a small signal amplitude by logarithmic conversion processing on the received signal after envelope detection.

  On the other hand, the color Doppler data generation unit 5 of the data generation unit 50 includes a π / 2 phase shifter 54, mixers 55-1 and 55-2, and LPFs (low-pass filters) 56-1 and 56-2. Then, quadrature detection is performed on the M channel received signal supplied from the receiving unit 3 of the transmitting / receiving unit 10 to generate a complex signal (I signal and Q signal).

  The color Doppler data generation unit 5 further includes a Doppler signal storage circuit 58, an MTI filter 59, and an autocorrelation calculator 60. The complex signal obtained by the quadrature detection is temporarily stored in the Doppler signal storage unit 58, and then the MTI filter 59, which is a high-pass digital filter, is stored in the complex signal stored in the Doppler signal storage unit 58. The signal is read out, and the Doppler component (clutter component) caused by the reflex movement or pulsatile movement of the organ is reflected from this complex signal. The autocorrelation calculator 60 calculates an autocorrelation value for the Doppler signal of the blood flow information extracted by the MTI filter 59, and further, based on the autocorrelation value, an average blood flow velocity value and a variance value And the power value is calculated to generate color Doppler data for M scanning directions (raster).

  Returning to FIG. 1 again, the data storage / processing unit 70 includes a data storage unit 6 and a data processing unit 7, and the data storage unit 6 is generated by the data generation unit 50 in units of M rasters. Mode data and color Doppler data are sequentially stored to generate three-dimensional or two-dimensional B-mode image data and color Doppler image data.

  On the other hand, the data processing unit 7 uses the three-dimensional B-mode image data and color Doppler image data generated in the data storage unit 6 and uses volume rendering image data, surface rendering image data, MIP (maximum intensity projection). ) Image processing is performed to generate image data, MPR (multi-planar reconstruction) image data, and the like.

  The display unit 81 includes a display data generation circuit, a conversion circuit, and a monitor (not shown). The display data generation circuit applies the B mode image data and the color Doppler image data generated in the data storage / processing unit 70 to the display unit 81. Scan conversion processing corresponding to a predetermined display form is performed to generate display data. Next, the conversion circuit performs D / A conversion and television format conversion on the display data and then displays the data on the monitor.

  On the other hand, the input unit 83 includes an input device such as a display panel, a keyboard, a trackball, a mouse, a selection button, and an input button on the operation panel, and inputs patient information, data collection conditions, display conditions, and the like. Various command signals are input.

  The system control unit 82 includes a CPU and a storage circuit (not shown), and the above-described various information input or set from the input unit 83 by the operator is stored in the storage circuit. Based on these pieces of information, the CPU controls the transmission / reception unit 10, the data generation unit 50, the data storage / processing unit 70, and the overall system. In particular, in this embodiment, transmission control for sequentially radiating transmission ultrasonic waves having a convex wavefront with respect to a plurality of transmission directions set at predetermined intervals with respect to the subject, the transmission direction or these Reception control for receiving reception ultrasonic waves from a plurality of directions (M directions) close to the transmission direction is performed substantially simultaneously.

(Shape of transmit beam, receive beam, and transmit / receive beam)
Next, the shape of the transmission beam formed by this embodiment will be described with reference to FIG. For example, the radius of curvature of the transducer array surface is 50 mm, the center frequency of the transmitted ultrasonic wave is 3.75 MHz (that is, the wavelength λ is 0.4 mm), the number of transmitting vibration elements M2 used for parallel simultaneous reception is 48 elements, FIG. 5B shows the transmission beam when the ultrasonic transducer 20 for convex scanning having the vibration element interval d of 0.3 mm is used and the M2 transmitting vibration elements are simultaneously driven as shown in FIG. 5A. Show.

In this case, the distance L to which the transmission beam having the wave surface of the curved surface substantially the same as the vibration element array surface is irradiated is approximately expressed by the following equation (4), and the transmission beam gradually diffuses further away from the distance L. Increase. That is, according to this transmission method, it is possible to obtain a uniform transmission beam having a wavefront with a curvature substantially equal to the curvature of the transducer array surface up to a distance of 10 cm from the vibration element.

  Next, the shapes of the transmission beam, reception beam, and transmission / reception beam in the parallel simultaneous reception of this embodiment are shown in FIG. FIG. 6A shows a transmission beam (solid line) Bt formed by the driving method shown in FIG. 5A, and five stages of parallel simultaneous reception beams (broken lines) Br-1 to B-1 formed in the transmission beam Bt. FIG. 6B shows transmission / reception beams Btr-1 to Btr-5 determined by the transmission beam Bt and the reception beams Br-1 to Br-5 described above. That is, according to the transmission method of the present embodiment, a relatively uniform transmission beam can be obtained in the parallel simultaneous reception region, so that it is possible to eliminate beam bending that has conventionally occurred in the transmission and reception beams.

(Weighting of drive signal amplitude)
Next, a driving signal amplitude weighting method performed by the driving signal amplitude control circuit 14 in the transmission unit 2 of the transmission / reception unit 10 and its effect will be described with reference to FIGS. The drive signal amplitude control circuit 14 sets the drive signal amplitude for the M2 transmitting vibration elements selected by the element selection unit 41 of the transmission / reception unit 10 based on the function (see FIG. 7) of the following equation (5), In particular, the vibration signal for transmission closer to the end portion reduces the drive signal amplitude.

  On the other hand, FIG. 8 shows a transmission sound field when a drive signal having a uniform amplitude as shown in FIG. 8A-1 is supplied to the M2 transmitting vibration elements (FIG. 8A-2). ), And an example of the transmission sound field (FIG. 8B-2) when the drive signal having the amplitude distribution shown in Expression (5) or FIG. 8B-1 is supplied. In the transmission sound field in the case where the drive signal has a uniform amplitude, unevenness is generated in the vicinity of the center portion, and a gentle decrease is observed at the end portion. On the other hand, the transmission sound field in the case of the amplitude distribution shown in FIG. 8 (b-1) has a substantially uniform characteristic from the center to the end, and can also sharply reduce the end. .

  FIG. 9 shows a transmission / reception sound field in parallel simultaneous reception when the drive signal having the amplitude distribution shown in Expression (5) is used. FIG. 9A shows a transmission sound field Bt and reception received at this time. FIG. 9B shows the sound fields Br-1 to Br-5, and FIG. 9B shows the transmission / reception sound fields Btr-1 to Btr- formed by the transmission sound field Bt and the reception sound fields Br-1 to Br-5. 5 is shown. As is apparent from this figure, when the drive signal having the amplitude distribution shown in the above equation (5) is used, the transmission / reception sound having a substantially uniform magnitude is obtained regardless of the position (direction) of parallel simultaneous reception. Thus, it is possible to generate B-mode image data and color Doppler image data having uniform sensitivity.

  Furthermore, since transmission ultrasonic waves radiated outside the region where parallel simultaneous reception is performed are very small, transmission energy can be used effectively, and artifacts due to side lobes and multiple reflections can be reduced.

(Image data generation procedure)
Next, the image data generation procedure in the above embodiment will be described with reference to FIGS. In the present embodiment, a case will be described in which the convex scanning ultrasonic probe 20 is used to generate B-mode image data and color Doppler image data for a subject by applying M-stage parallel simultaneous reception.

  The operator of the ultrasonic diagnostic apparatus 100 first inputs the probe ID of the ultrasonic probe 20 used in the input unit 83 of FIG. 1 and various conditions necessary for collecting the image data, and the input information is system control. The data is stored in a storage circuit (not shown) of the unit 82. As the above conditions, the transmission delay time (however, in this embodiment, the delay time difference is zero), the number of parallel simultaneous reception stages (the number of reception signal groups) M, the number of transmission vibration elements M2, the number of reception vibration elements M3, and the number of reception signal groups The number of channels M4, the weighting function of the drive signal, and the like are set in the input unit 83 as necessary.

  When the initial setting is completed, the operator fixes the tip (ultrasonic wave transmitting / receiving surface) of the ultrasonic probe 20 at a predetermined position on the surface of the subject body and starts transmitting / receiving ultrasonic waves. That is, the system control unit 82 receives the information on the number M2 of transmitting vibration elements and the number M3 of receiving vibration elements once stored in the storage circuit in the element selection control unit 42 of the transmission / reception unit 10 and receives the information on the number M of parallel simultaneous reception stages. Information related to the weighting function of the drive signal is supplied to the channel selection circuit 33 of the unit 3 to the drive signal amplitude control circuit 14 of the transmission unit 2, respectively.

  The element selection control unit 42 to which the number of transmission vibration elements M2 and the number of reception vibration elements M3 (M3≈M2) are supplied supplies a control signal to a multiplexer (not shown) of the element selection unit 41, and the first ultrasonic wave The transmitting vibration elements 22-1 to 22-M2 (M2 = 9) used for transmission / reception are selected. In addition, the drive signal amplitude control circuit 14 of the transmission unit 2 sets a weighting function of the drive signal amplitude.

  Next, when generating the B-mode data, the rate pulse generator 11 of FIG. 2 generates a rate pulse that determines the repetition period Tr of the ultrasonic pulse by dividing the reference signal supplied from the reference signal generator 1. The signal is supplied to the drive circuit 13 via the transmission delay circuit 12.

  The M2 channel drive circuit 13 generates an M2 channel impulse or a drive signal having a preset waveform based on the rate pulse timing, and further, based on the weighting function supplied from the drive signal amplitude control circuit 14. To set the amplitude of the drive signal. The amplitude-weighted M2 channel drive signal is supplied to the transmission vibration elements 22-1 to 22-M2 selected by the element selection unit 41, and these transmission vibration elements 22-1 to 22-. M2 is driven substantially simultaneously to radiate a convex wavefront transmission ultrasonic wave into the subject.

  A part of the transmitted ultrasonic wave radiated to the subject is reflected at an interface or tissue between organs having different acoustic impedances. Further, when this ultrasonic wave is reflected by a moving reflector such as a heart wall or blood cell, the ultrasonic frequency is subjected to Doppler shift.

  The ultrasonic reflected wave (received ultrasonic wave) reflected by the tissue or blood cell of the subject is received by the receiving vibrating elements 1 to M3 (M3≈M2) of the ultrasonic probe 20 already selected by the element selecting unit 41. And converted into an electric signal (received signal). Further, the received signal is supplied to the receiving unit 3 of the transmitting / receiving unit 10 via the element selecting unit 41, amplified to a predetermined size by the preamplifier 31 of the receiving unit 3, and then supplied to the A / D converter 32. Converted into a digital signal.

  The M3 channel reception signal converted into the digital signal is supplied to the channel selection circuit 33, and the channel selection circuit 33 selects a reception signal group of the adjacent M4 channel (M4 <M3) from among these M3 channel reception signals. For example, M groups are selected at intervals of one element (see FIG. 3), and these M received signal groups are supplied to the beam formers 34-1 to 34-M.

  That is, the M4 channel received signal group obtained by the vibrating elements 22-1 to 22-M4 is the beam former 34-1, and the received signal group obtained by the vibrating elements 22-2 to 22- (M4 + 1) is the beam former. Similarly, the reception signal groups obtained by the vibration elements 22-3 to 22- (M4 + 2),..., The vibration elements 22- (M3-M4 + 1) to 22-M3 are supplied to 34-2. The beam former 34-3 is supplied to the beam former 34-M. Each of the beam formers 34-1 to 34-M performs dynamic focusing by phasing and adding the reception signals of the M4 channel.

  The received signals of the M channels phased and added in the beam formers 34-1 to 34-M are supplied to the B-mode data generation unit 4 in the data generation unit 50 of FIG. 4 and after envelope detection and logarithmic conversion are performed. 1 is stored in the data storage unit 6 in the data storage / processing unit 70 of FIG.

  On the other hand, in the generation of the color Doppler data, the transmission vibration elements 22-1 to 22-M2 and the reception vibration elements 22-1 to 22-M3 are performed by the same procedure as described above in order to obtain the Doppler shift of the reception signal. Is used to perform ultrasonic transmission / reception a plurality of times (L times), and a Doppler signal is detected for the received signal obtained at this time.

  That is, the system control unit 82 controls the element selection control unit 42 to select the transmission vibration elements 22-1 to 22-M2 and the reception vibration elements 22-1 to 22-M3 and transmit / receive ultrasonic waves for color Doppler. To do. Then, the obtained M channel reception signal is supplied to the color Doppler data generation unit 5, and a complex signal is generated from quadrature detection by the mixers 55-1 and 55-2 and the LPFs 56-1 and 56-2. Next, each of the real number component (I component) and the imaginary number component (Q component) of the complex signal is temporarily stored in the Doppler signal storage unit 58. Similarly, complex signals are collected by the same procedure for received signals obtained by the second to Lth ultrasonic transmission / reception using the same vibration element, and stored in the Doppler signal storage unit 58.

  If the storage of the M-channel complex signal obtained by L times of ultrasonic transmission / reception using the transmitting vibration elements 22-1 to 22-M2 and the receiving vibration elements 22-1 to 22-M3 is completed, the system The control unit 82 sequentially reads L complex signal components corresponding to a predetermined position (depth) in each of the M channel complex signals stored in the Doppler signal storage unit 58 and supplies the L complex signal components to the MTI filter 59. Then, the MTI filter 59 performs a filtering process on the supplied complex signal component, for example, a reflected wave component from a fixed reflector such as a living tissue or a tissue Doppler component (clutter component) generated by the movement of a tissue such as a myocardium. The blood flow Doppler component resulting from the blood flow is extracted.

  Next, the autocorrelation calculator 60 to which the complex signal of the blood flow Doppler component is supplied from the MTI filter 59 performs autocorrelation processing using this complex signal, and further, based on the autocorrelation processing result, the average of blood flow Calculate speed value, variance value, power value, etc. Such an operation is also performed on other positions (depths), and the calculated average velocity value, variance value, and power value of the blood flow are stored in the data storage / processing unit 70 of FIG. Save in part 6.

  That is, in the B mode data storage area and the color Doppler data storage area of the data storage unit 6, the vibration elements 22-1 to 22-M4, the vibration elements 22-2 to 22- (M4 + 1),... B mode data and color Doppler data corresponding to M received beam directions (rasters) formed by phasing addition of received signal groups from (M3-M4 + 1) to 22-M3 are stored.

  In the same procedure, the system control unit 82 controls the element selection control unit 42 to select the vibration elements 22- (M2 + 1) to 22-2M2, the vibration elements 22- (2M2 + 1) to 22-3M2,. The B-mode data and color Doppler data of each raster obtained by performing M-stage parallel simultaneous reception are stored in the B-mode data storage area and the color Doppler data storage area of the data storage unit 6.

  By the above procedure, the B mode data and color Doppler data obtained in units of M received beam directions (raster) are sequentially stored in the data storage unit 6 to generate two-dimensional B mode image data and color Doppler image data. The data processing unit 7 performs image processing as necessary. The display data generation circuit of the display unit 81 performs processing such as scan conversion corresponding to a predetermined display form on the B-mode image data and color Doppler image data generated in the data storage / processing unit 70. Display data is generated, and this display data is D / A converted and television format converted in a conversion circuit (not shown) and displayed on the monitor.

  In this embodiment, the transmission aperture width is set to be approximately the same as the reception aperture width. For example, as shown in FIG. 10, the number of receiving vibration elements M3 increases to M3x as the number of parallel simultaneous reception stages M increases. In this case, by increasing the number M2 of transmitting vibration elements to M2x at the same rate, it is possible to obtain a relatively uniform transmission / reception beam without depending on the number of stages of parallel simultaneous reception without beam bending. It becomes.

(Modification)
Next, a modification of the above embodiment will be described with reference to FIGS. In this modification, an ultrasonic probe for linear scanning in which vibration elements are arranged on a straight line is shown. FIG. 11 shows a transmission beam Bt obtained by simultaneously driving the vibration elements arranged on a straight line. In this case as well, the transmission beam Bt is transmitted in the same manner as the convex scanning ultrasonic probe of FIG. beam Bt forms a wavefront (translational wave surface) having substantially the same curvature as the vibrating element array surface within a distance L (i.e., infinite radius of curvature).

  As shown in FIG. 12, even when the transmission beam and the reception beam are deflected in a predetermined direction by giving a deflection transmission delay time and reception delay time to the vibration element, the difference in delay time for beam diffusion is reduced to zero. Is set to a wavefront having substantially the same curvature as the vibration element array surface.

  That is, in FIG. 11 or FIG. 12, it is possible to form a transmission beam Bt having a beam width substantially equal to the transmission aperture width and having a uniform sound field in the scanning direction.

  According to the first embodiment of the present invention described above, when performing parallel simultaneous reception for a predetermined imaging region using a convex scanning ultrasonic probe or a linear scanning ultrasonic probe, one parallel operation is performed. Transmit and receive beams without beam bending by forming a transmission beam having a convex or flat wavefront by driving simultaneously a vibrating element having a transmission aperture width that is approximately the same as the reception aperture width used for simultaneous reception. It becomes possible to form.

  Furthermore, when driving the transmission element having the transmission aperture width, a flat transmission sound field is formed in the azimuth direction by controlling the drive signal amplitude for the vibration element at the end based on a preset weighting function. It is possible to obtain a transmission / reception beam for parallel simultaneous reception having a high reception sensitivity.

  In addition, since the end of the transmission sound field can be sharply reduced by weighting the drive signal amplitude, transmission ultrasonic waves radiated in unnecessary directions can be prevented, and the influence of multiple reflections and side lobes can be reduced. It becomes possible.

  Therefore, the transmission / reception beam formed in the present embodiment enables generation of ultrasonic image data excellent in real-time property and image quality, and the diagnostic ability is greatly improved.

  In the above embodiment, the case where the transmitting vibration element is simultaneously driven in order to obtain a wavefront having substantially the same curvature as that of the vibration element array surface has been described. Any driving method may be used as long as it is possible to form a transmission beam having the above.

  Next, a second embodiment of the present invention will be described. The feature of the second embodiment is that when performing parallel simultaneous reception for a predetermined imaging region using a sector scanning ultrasonic probe in which ultrasonic transducer elements are linearly arranged in a one-dimensional array, It is to form a diffuse transmission beam having a uniform sound field for an imaging region where parallel simultaneous reception is performed.

(Device configuration)
The ultrasonic diagnostic apparatus according to the present embodiment and the ultrasonic diagnostic apparatus according to the first embodiment described above are particularly different in the configuration of the transmission / reception unit and the ultrasonic probe. The configuration and operation of the ultrasonic diagnostic apparatus according to the present embodiment will be described with reference to FIGS.

  FIG. 13 is a block diagram illustrating the overall configuration of the ultrasonic diagnostic apparatus according to the present embodiment, and FIG. 14 is a block diagram of a transmission / reception unit that configures the ultrasonic diagnostic apparatus. In the configuration of the ultrasonic diagnostic apparatus of the present embodiment described below, units having the same operations and functions as the units of the first embodiment described above are given the same reference numerals, and detailed descriptions thereof are omitted. .

  The ultrasonic diagnostic apparatus 200 shown in FIG. 13 includes an ultrasonic probe 210 for sector scanning in which M1 vibration elements are linearly arranged in a one-dimensional array and transmits / receives ultrasonic waves to / from a subject, and the vibration elements. A transmission / reception unit 101 that supplies a driving signal and performs phasing addition on the reception signals obtained from these vibration elements is provided.

  Furthermore, the ultrasonic diagnostic apparatus 200 is similar to the ultrasonic diagnostic apparatus 100 of the first embodiment in that the data generation unit 50, the data storage / processing unit 70, the display unit 81, the reference signal generation unit 1, the input unit 83, and the system A control unit 82 is provided.

  The transmission / reception unit 101 illustrated in FIG. 14 includes a transmission unit 201 that supplies a driving signal to M2 (M2 <M1) transmission vibration elements that are set in advance, and M3 (M3≈M2) reception vibrations. A receiving unit 301 is provided that performs phasing addition on the received signal obtained from the element. The transmission unit 201 includes a rate pulse generator 11, a transmission delay circuit 121, a drive circuit 13, and a drive signal amplitude control circuit 14. The transmission delay circuit 121 spreads the transmission beam to a predetermined angle. A delay time for diffusion and a delay time for deflection for deflecting in a predetermined direction are given to the rate pulse.

  On the other hand, the drive circuit 13 generates a drive signal for driving the M2 transmission vibration elements based on the timing of the rate pulse, and the drive signal amplitude control circuit 14 sets the drive signal amplitude of the transmission vibration element. Predetermined weighting is performed.

  On the other hand, the receiving unit 301 includes a preamplifier 31 and an A / D converter 32 configured with M3 channels, and M-channel beamformers 34-1 to 34-M.

  Here, the characteristics of the transmission / reception beam obtained by the transmission / reception unit 101 will be described with reference to FIGS. FIG. 15 shows a relationship between a transmitting vibration element driving method and a transmission beam and a reception beam when performing parallel simultaneous reception with respect to a direction in which the deflection angle is zero (that is, perpendicular to the arrangement surface of the vibration elements). The total delay time set only by the diffusion delay time is given to the drive signal for each of the M2 vibrating elements shown in FIG. 15A, and a transmission beam Bt having a convex wavefront is formed. Is done.

  On the other hand, FIG. 15B shows the reception beams Br-1 to Br-M and the above-described transmission beam Bt formed by the M channel beamformers 34-1 to 34-M in the reception unit 301 at the time of parallel simultaneous reception. As shown, a uniform transmission beam Bt is emitted in a region where parallel simultaneous reception is performed. In this case, for example, at the deepest part of the image observation region (α1 and α2 in FIG. 15B), the transmission beam diffusion angle is set so that the end of the transmission beam Bt coincides with the reception beams Br-1 and Br-M. Set up.

  Next, FIG. 16 shows the relationship between the transmission vibration element driving method and the transmission beam and the reception beam when performing parallel simultaneous reception in the direction of the deflection angle θ0. FIG. The drive signal for each of the M2 transmitting vibration elements shown is given a total delay time obtained by combining the deflection delay time and the diffusion delay time. The transmission vibration element driven by this drive signal has a θ0 value. A transmission beam Bt having a convex wavefront in the direction is emitted.

  FIG. 16B shows the reception beams Br-1 to Br-M and the above-described transmission beam Bt formed by the M channel beamformers 34-1 to 34-M in the reception unit 301 at the time of parallel simultaneous reception. As shown, a uniform transmission beam Bt is emitted in a region where parallel simultaneous reception is performed.

  A transmission / reception beam is formed by the transmission beam and the reception beam shown in FIG. 15 or FIG. 16, and B-mode image data or color Doppler image data is generated and displayed by this transmission / reception beam. Since it is the same as that of the first embodiment, the description thereof is omitted.

  In this embodiment, when the reception area is increased for reasons such as an increase in the number of parallel simultaneous reception stages, the spread delay time is set so that the spread angle of the transmission beam is increased corresponding to the reception area. Updates are made.

  According to the second embodiment of the present invention described above, when parallel simultaneous reception is performed with respect to a predetermined imaging region using a sector scanning ultrasonic probe, imaging in which one parallel simultaneous reception is performed is performed. By forming a spread transmission beam for the region, a transmission / reception beam without beam bending can be obtained.

  Further, in the same manner as in the first embodiment, when forming the diffuse transmission beam, the azimuth direction is controlled by controlling the drive signal amplitude of the vibration element in the vicinity of the end of the transmission aperture based on a preset weighting function. A flat transmission sound field can be formed, and a parallel simultaneous reception transmission / reception beam having uniform reception sensitivity can be obtained.

  In addition, the edge of the transmission sound field can be sharply reduced by the weighting of the drive signal amplitude, so that transmission ultrasonic waves radiated in unnecessary directions can be prevented, and the influence of multiple reflections and side lobes can be reduced. It becomes possible.

  Therefore, the transmission / reception beam formed in the present embodiment enables generation of ultrasonic image data excellent in real-time property and image quality, and the diagnostic ability is greatly improved.

  As mentioned above, although the Example of this invention has been described, this invention is not limited to said Example, It can change and implement. For example, in the above-described embodiments, the ultrasonic probe in which the vibration elements are arranged one-dimensionally has been described. However, an ultrasonic probe in which the vibration elements are arranged two-dimensionally may be used, and for convex scanning, linear scanning, and sector scanning. It is not limited to the ultrasonic probe.

  In the above-described embodiment, the case where the number of transmitting vibration elements and the number of receiving vibration elements are substantially equal has been described. However, the present invention is not limited to this. It is also possible to set it smaller than the number of elements M3.

  Furthermore, the amplitude weighting function for the drive signal of the transmitting vibration element is not limited to the expression (5), and any other weighting function may be used as long as the weight is such that the drive signal amplitude of the transmitting vibration element at the end is reduced. May be used.

1 is a block diagram showing the overall configuration of an ultrasonic diagnostic apparatus according to a first embodiment of the present invention. The block diagram which shows the structure of the transmission / reception part in the Example. The figure which shows typically the selection method of the vibration element for transmission in the parallel simultaneous reception of the Example, and the vibration element for reception. The block diagram which shows the structure of the data generation part in the Example. The figure which shows the shape of the transmission beam formed in the Example. The figure which shows the shape of the transmission beam, reception beam, and transmission / reception beam which are formed in the Example. The figure which shows the amplitude weighting function of the drive signal supplied to the vibration element for transmission in the Example. The figure which shows the relationship between the drive signal amplitude and transmission sound field in the Example and the conventional method. The figure which shows the transmission sound field in the Example, a reception sound field, and a transmission / reception sound field. The figure which shows the increase in the transmission aperture width accompanying the increase in the number of parallel simultaneous receiving steps in the same Example. The figure which shows the drive method and transmission beam of the transmission vibration element in the modification of the Example. The figure which shows the drive method and transmission beam of a transmission vibration element in the case of deflecting a transmission beam and a reception beam in the modification of the Example. The block diagram which shows the whole structure of the ultrasonic diagnosing device in the 2nd Example of this invention. The block diagram which shows the structure of the transmission / reception part in the Example. The figure which shows the relationship between the drive method of the transmission vibration element at the time of performing parallel simultaneous reception with respect to the direction where a deflection angle is zero in the Example, a transmission beam, and a reception beam. The figure which shows the drive method of the oscillation element for transmission at the time of performing parallel simultaneous reception with respect to a predetermined | prescribed deflection | deviation direction, the transmission beam, and a reception beam in the Example. The figure for demonstrating the beam bending of the transmission / reception beam in the conventional parallel simultaneous reception. The figure for demonstrating the nonuniformity of the reception sensitivity in the conventional parallel simultaneous reception.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Reference signal generation part 2, 201 ... Transmission part 3, 301 ... Reception part 4 ... B mode data generation part 5 ... Color Doppler data generation part 6 ... Data storage part 7 ... Data processing part 10, 101 ... Transmission / reception part 11 ... Rate pulse generators 12, 121 ... transmission delay circuit 13 ... drive circuit 14 ... drive signal amplitude control circuit 20, 210 ... ultrasonic probe 31 ... preamplifier 32 ... A / D converter 33 ... channel selection circuit 34 ... beam former 41 ... Element selection unit 42 ... Element selection control unit 50 ... Data generation unit 70 ... Data storage / processing unit 81 ... Display unit 82 ... System control unit 83 ... Input unit 100, 200 ... Ultrasonic diagnostic apparatus

Claims (3)

An ultrasonic probe including a plurality of arranged vibration elements that transmit and receive ultrasonic waves; and
Based on the weighting function for setting the intensity of the transmission ultrasonic wave at the array end of the vibration element to be lower than the intensity of the transmission ultrasonic wave at the center of the array, and the drive signal having information on the delay time for diffusion, A transmission means for transmitting transmission ultrasonic waves diffused based on the diffusion delay time ;
To phasing addition process the received signal based on the reflected ultrasonic wave obtained by said vibration element
And a parallel receiving means for obtaining a phasing addition signal by forming a plurality of receiving sound rays ,
The transmission means transmits the transmission according to an increase in the number of reception sound rays in the parallel reception means.
The ultrasonic diagnostic apparatus, wherein the diffusion delay time is set so as to increase a degree of ultrasonic diffusion . The transmission means transmits ultrasonic waves from the vibration element based on the weighting function and the deflection delay time for controlling the ultrasonic transmission timing of the vibrator in addition to the diffusion delay time ,
The ultrasonic diagnostic apparatus according to claim 1, wherein the transmission unit controls a wavefront direction of the transmission ultrasonic wave based on the deflection delay time. Image data generating means for generating ultrasonic image data based on the phasing addition signal;
The ultrasonic diagnostic apparatus according to any one of claims 1 or 2, and display means for displaying the generated the image data, further comprising a.

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