JP2019033899A - Ultrasonic diagnostic apparatus and specular reflector image generation method - Google Patents

Abstract

To provide an ultrasonic diagnostic apparatus that can render a specular reflector such as puncture needles without lowering a frame rate over a large angular range, and a specular reflector image generation method.SOLUTION: An ultrasonic diagnostic apparatus has: a transmission unit for transmitting the transmission ultrasound from an oscillator; a transmission delay generation unit for controlling a delay time of a driving signal every oscillator so that a grating lobe is generated in addition to a main lobe in a visual field; a sound ray signal generation unit for performing phasing addition on signals received from a plurality of oscillators and generating sound ray signals; and a signal processing unit for extracting only a component derived from a grating lobe from the sound ray signal, calculating the angle of the grating lobe and distance information to a reflection point of the grating lobe reflected by a puncture needle based on the sound ray signal including only the component derived from the grating lobe, and generating the needle image data showing the puncture needle based on the angle and distance information.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an ultrasonic diagnostic apparatus and a specular reflector image generation method using ultrasonic waves.

  In the ultrasonic diagnostic apparatus, a plurality of transducers (converters) that convert between voltage signals and ultrasonic vibrations are arranged in a predetermined direction (scanning direction), and these transducers are driven by a drive voltage. An ultrasonic wave is emitted by applying. The ultrasonic diagnostic apparatus can acquire two-dimensional data almost in real time by temporally changing (scanning) a transducer that detects a voltage change caused by incidence of an ultrasonic reflected wave. .

  Further, the ultrasonic diagnostic apparatus is used not only in image diagnosis but also in, for example, a biopsy for collecting a tissue in a subject. Specifically, in order to accurately puncture a region of interest such as a tumor, the region of interest and the puncture needle are monitored in real time using an ultrasonic diagnostic apparatus.

  When the puncture needle is depicted in the ultrasonic diagnostic apparatus, if the angle of the puncture needle becomes an acute angle with respect to the entry surface, the reflected ultrasound from the puncture needle may not be received by the ultrasonic probe. In order to solve this, ultrasonic transmission in the first transmission direction for generating an ultrasonic diagnostic image (luminance image) and ultrasonic transmission in the second transmission direction for drawing the puncture needle are performed. In accordance with each reflected wave, a luminance image with good image quality and an image in which a puncture needle is suitably depicted are generated, and these are superimposed. However, in the superimposed image obtained in this way, since the ultrasonic transmission is performed a plurality of times in order to generate one image (one frame), the frame rate is lowered. For this reason, there is a demand for an ultrasonic diagnostic apparatus that improves the real-time performance by rendering the puncture needle more appropriately without reducing the frame rate.

  As a technique that meets such a demand, for example, there is a technique disclosed in Patent Document 1. Patent Document 1 discloses an image generated by performing normal reception focus and an image in which reception focus is tilted by a predetermined angle with respect to the transmission direction of the ultrasonic beam in order to visualize the needle (specular reflection surface). Are disclosed.

JP 2015-27346 A

  However, in the technique disclosed in Patent Document 1, the angle range in which the reception focus can be tilted is limited to the transmission path range of the ultrasonic beam, so that a puncture needle inserted at a high angle can be suitably depicted. It is difficult to do.

  In view of the above, an object of the present invention is to provide an ultrasonic diagnostic apparatus and a specular reflector image generation method capable of rendering a specular reflector such as a puncture needle over a wide angular range without reducing the frame rate. And

  An ultrasonic diagnostic apparatus according to the present invention is an ultrasonic diagnostic apparatus including an ultrasonic probe that transmits transmission ultrasonic waves and receives reflected ultrasonic waves toward a subject into which a specular reflector is inserted. Generating a drive signal and outputting it to each of the plurality of transducers included in the ultrasonic probe, and a transmission unit for transmitting the transmission ultrasonic wave from the transducer, and a main unit in the image field of view. A transmission delay generation unit that controls a delay time of the drive signal for each transducer so that a grating lobe is generated in addition to a lobe, a reception unit that receives a reception signal from each of the plurality of transducers, and A sound ray signal generation unit that generates a sound ray signal by phasing and adding reception signals from a plurality of transducers, and extracts only a component derived from the grating lobe from the sound ray signal, and is derived from the grating lobe. Completion Based on the sound ray signal including only the frequency, the angle of the grating lobe, and the distance information to the reflection point where the grating lobe is reflected by the specular reflector, and based on the angle and distance information Specular reflector image data indicating the specular reflector based on the signal processing unit that generates coordinate information corresponding to the position of the specular reflector, the sound ray signal including only the component derived from the grating lobe, and the coordinate information An image processing conversion unit for generating

  The specular reflector image generation method of the present invention includes an ultrasonic diagnostic apparatus including an ultrasonic probe that transmits transmission ultrasonic waves and receives reflected ultrasonic waves toward a subject into which the specular reflector is inserted. The specular reflector image generation method according to claim 1, wherein a drive signal having a delay time controlled for each of the plurality of transducers of the ultrasonic probe is generated so that a grating lobe is generated in addition to a main lobe in an image field. Output to each of a plurality of transducers included in the ultrasound probe, transmit the transmission ultrasound from the transducers, and perform phasing addition of reception signals from the plurality of transducers to obtain a sound ray signal Only the component derived from the grating lobe is extracted from the sound ray signal, and based on the sound ray signal including only the component derived from the grating lobe, the angle of the grating lobe and the gray Ingurobu calculates the distance information to the reflection point which is reflected by the specular reflector generates a specular reflector image data indicating the specular reflector based on the angle and distance information.

  According to the present invention, a specular reflector such as a puncture needle can be depicted over a wide angular range without reducing the frame rate.

The figure which illustrated the appearance composition of the ultrasonic diagnostic equipment Block diagram illustrating the internal configuration of the ultrasonic diagnostic apparatus A diagram for explaining a grating lobe generated when a plane wave composed of continuous waves in the main lobe direction is transmitted. Conceptual diagram illustrating the relationship between the grating lobe and the main lobe Conceptual diagram for explaining how a puncture needle is detected using a grating lobe Flow chart showing an operation example of the ultrasonic diagnostic apparatus in the needle enhancement mode Flowchart for explaining image generation processing when main lobe steer angle is 0 ° Flowchart for explaining image generation processing when the steer angle of the main lobe is x ° The figure which shows the frequency characteristic of the normalized sensitivity of transmission / reception of the ultrasonic probe used for a comparative example and an Example The figure which shows the frequency characteristic of the normalization sensitivity of transmission of the ultrasonic probe used for a comparative example and an Example The figure which shows the time characteristic of the signal strength of the drive signal in Examples other than Example 6, and a comparative example. The figure which shows the power spectrum of the drive signal in Examples other than Example 6, and a comparative example. The figure which shows the time characteristic of the signal strength of the transmission ultrasonic wave in Examples other than Example 6, and a comparative example. The figure which shows the power spectrum of the transmission ultrasonic wave in Examples other than Example 6, and a comparative example. The figure which shows the time characteristic of the signal strength of the drive signal in Example 6. FIG. The figure which shows the power spectrum of the drive signal in Example 6 The figure which shows the time characteristic of the signal strength of the transmission ultrasonic wave in Example 6. FIG. The figure which shows the power spectrum of the transmission ultrasonic wave in Example 6. FIG. The figure which shows the relationship between the element grouping number, a grating lobe angle, and a transmission frequency in m = 1. The figure which shows the relationship between the element grouping number in m = 2, a grating lobe angle, and a transmission frequency.

  Embodiments of the present invention will be described below with reference to the drawings. However, the scope of the invention is not limited to the illustrated example. In addition, in the following description, what has the same function and structure attaches | subjects the same code | symbol, and abbreviate | omits the description.

<Outline of each configuration>
As shown in FIGS. 1 and 2, the ultrasonic diagnostic apparatus S according to the present embodiment includes an ultrasonic diagnostic apparatus main body 1 and an ultrasonic probe 2. FIG. 1 is a diagram illustrating an external configuration of the ultrasonic diagnostic apparatus S. FIG. 2 is a block diagram illustrating the internal configuration of the ultrasonic diagnostic apparatus S. The ultrasonic probe 2 transmits ultrasonic waves (transmitted ultrasonic waves) to a subject such as a living body (not shown) and receives reflected waves (reflected ultrasonic waves: echoes) reflected by the subject. To do.

  The ultrasonic diagnostic apparatus main body 1 is connected to the ultrasonic probe 2 via a cable 3, and transmits an electric signal drive signal to the ultrasonic probe 2, so that the ultrasonic probe 2 is attached to the subject. On the other hand, based on the received signal, which is an electrical signal generated by the ultrasonic probe 2 in response to the reflected ultrasonic wave from the inside of the subject received by the ultrasonic probe 2 while transmitting the transmission ultrasonic wave. The internal state in the subject is imaged as an ultrasound image.

  The ultrasonic probe 2 includes a vibrator 2a that is a piezoelectric element, for example. For example, a plurality of the vibrators 2a are arranged in a one-dimensional array in the azimuth direction. In the present embodiment, the ultrasound probe 2 includes, for example, several tens to several hundreds of transducers 2a. Note that the vibrators 2a may be arranged in a two-dimensional array. The number of vibrators 2a can be set arbitrarily.

  In the present embodiment, a linear scanning type electronic scan probe is employed for the ultrasound probe 2, but either an electronic scanning method or a mechanical scanning method may be employed. As the ultrasonic probe 2, any of a linear scanning method, a sector scanning method, or a convex scanning method may be adopted. Further, as will be described later, in the present embodiment, it is preferable to employ the ultrasonic probe 2 that can transmit ultrasonic waves in a wide band with good sensitivity.

  For example, as shown in FIG. 2, the ultrasonic diagnostic apparatus body 1 includes an operation input unit 11, a transmission unit 12, a reception unit 13, a sound ray signal generation unit 14, a signal processing unit 15, and image processing conversion. A unit 16, a display unit 17, and a control unit 18 are provided.

  The operation input unit 11 includes, for example, various switches, buttons, a trackball, a mouse, a keyboard, and the like for inputting data such as a command for starting diagnosis and personal information of a subject, and the like. Output to the control unit 18.

  As shown in FIG. 2, the operation input unit 11 includes a needle enhancement mode selection unit 111. The needle enhancement mode selection unit 111 synthesizes and displays needle image data that enhances the puncture needle and makes it easy to see when normal ultrasonic diagnosis using a puncture needle is performed. Can be selected to be displayed. Details of the needle emphasis mode will be described later.

  The transmission unit 12 supplies a drive signal, which is an electrical signal for generating transmission ultrasonic waves, to the ultrasonic probe 2 via the cable 3 under the control of the control unit 18.

  More specifically, the transmission unit 12 includes a clock generation circuit, a pulse generation circuit, a duty setting unit, and the like, and generates a pulse signal as a drive signal. The clock generation circuit is a circuit that generates a clock signal that determines the transmission timing and transmission frequency of the drive signal. The pulse generation circuit is a circuit for generating a pulse signal at a predetermined cycle. The pulse generation circuit generates a rectangular pulse signal by switching and outputting, for example, five values (+ HV / + MV / 0 / −MV / −HV). Note that the voltage switched by the pulse generation circuit is not limited to five values, and may be set to an appropriate value, but is preferably five or less. Thereby, the frequency component contained in the transmission ultrasonic wave can be suitably controlled without increasing the apparatus cost so much. Note that the frequency component included in the transmitted ultrasonic wave is more preferable as the wider the band, the wider the detectable angular range.

  The duty setting unit sets the duty ratio of the pulse signal output from the pulse generation circuit. That is, the pulse generation circuit outputs a pulse signal having a pulse waveform according to the duty ratio set by the duty setting unit. For example, the duty ratio may be changeable based on an input operation by the operation input unit 11.

  In the present embodiment, the duty setting unit generates peaks included in the transmission frequency band of the ultrasonic probe 2 on the low frequency side and the high frequency side of the center frequency of the transmission frequency band of the ultrasonic probe 2, respectively. Set the duty ratio of the pulse signal. As a method for setting the duty ratio of such a pulse signal, for example, a method disclosed in Japanese Patent Application Laid-Open No. 2014-168555 can be applied.

  The transmission unit 12 may further include a duration of each section of the same voltage level of the drive signal output from the pulse generation circuit and a time and voltage setting unit for setting the voltage level. In other words, the pulse generation circuit outputs a drive signal having a pulse waveform according to the duration and voltage level of each section set by the time and voltage setting unit. For example, the duration and voltage level of each section set by the time and voltage setting unit may be changeable based on an input operation by the operation input unit 11.

  The transmission unit 12 configured as described above sequentially switches the plurality of transducers 2a that supply the drive signal while shifting a predetermined number for each transmission / reception of the ultrasonic wave under the control of the control unit 18, and the plurality of the output selected. Scanning is performed by supplying a drive signal to the vibrator 2a. In particular, when the needle emphasis mode is selected by an operation on the needle emphasis mode selection unit 111, the transmission unit 12 sets a plurality of elements to a plurality of elements based on control of a transmission delay generation unit 181 of the control unit 18 described later. By performing element grouping to be grouped together, transmission is performed in which the grating lobes are intentionally sent into the image field.

  The grating lobe is a kind of sub-pole (side lobe) that can be generated by the relationship between the element pitch (interval) of the transducer 2a (piezoelectric element) provided in the ultrasonic probe 2 and the wavelength of the transmitted ultrasonic wave. is there. FIG. 3 is a diagram for explaining a grating lobe generated when a plane wave composed of a continuous wave in the main lobe direction (0 °) is transmitted. As shown in FIG. 3, the grating lobe is at an angle (θ) shifted by one or more wavelengths due to the relationship between the spacing (element pitch (l)) and the wavelength (λ) between a plurality of transducers of the ultrasonic probe. Arise. Details of the relationship between the angle (grating angle) θ, the frequency λ of the transmission ultrasonic wave, and the element pitch l will be described later.

  A grating lobe is not required to generate B-mode image data for normal ultrasound diagnosis, but in the needle enhancement mode, the apparent element pitch is increased by element grouping in order to detect the puncture needle appropriately. A grating lobe intentionally generated in the image field is used. The element grouping is a method of giving the same delay time by regarding two or more adjacent elements as one element for the delay time usually given for each element. As a result, the grating lobe can be generated in the image field even by an ultrasonic probe designed so that the grating lobe is not generated in the image field during normal transmission and reception.

  FIG. 4 is a conceptual diagram illustrating the relationship between the grating lobe and the main lobe. As shown in FIG. 4, the grating lobe is sent in a different direction from the main lobe. In FIG. 4, for the sake of simplicity, only the main lobe and a pair of left and right grating lobes are illustrated, but actually the grating lobes are generated at various angles different from the main lobe depending on the frequency transmitted and received. It will be.

  FIG. 5 is a conceptual diagram for explaining how a puncture needle is detected using a grating lobe. As shown in FIG. 5, in the needle emphasis mode, normal B-mode image data that depicts the internal structure of the subject is generated using the main lobe, and the puncture inserted into the subject using the grating lobe The needle is detected.

  Further, the transmission unit 12 may perform a pulse inversion method in order to extract a harmonic component used for tissue harmonic imaging (THI). Tissue harmonic imaging is an imaging method that can obtain a B-mode image with good contrast by imaging a harmonic component with respect to a fundamental component of a transmission signal. In the pulse inversion method, the first and second pulse signals that are reversed in polarity or time are transmitted at a predetermined time interval, and the corresponding received signals are combined to cancel the fundamental wave component. This emphasizes harmonic components. Note that in the pulse inversion method of the present embodiment, the second pulse signal in which the polarity is inverted by changing at least one of the plurality of duties of the first pulse signal may be transmitted. Further, the second pulse signal may be time-reversed with respect to the first pulse signal. In the following description, transmission of the first pulse signal may be referred to as first transmission, and transmission of the second pulse signal may be referred to as second transmission. In addition, a reception signal corresponding to the first transmission may be referred to as a first reception signal, and a reception signal corresponding to the second transmission may be referred to as a second reception signal.

  The receiving unit 13 is a circuit that receives a reception signal of an electrical signal from the ultrasonic probe 2 via the cable 3 under the control of the control unit 18. The receiving unit 13 includes, for example, an amplifier and an A / D conversion circuit. The amplifier is a circuit for amplifying the received signal with a predetermined amplification factor set in advance for each individual path corresponding to each transducer 2a. The A / D conversion circuit is a circuit for analog-digital conversion (A / D conversion) of the amplified received signal.

  The sound ray signal generation unit 14 performs phasing addition on the A / D converted reception signal to generate a sound ray signal. As shown in FIG. 2, the sound ray signal generation unit 14 includes a phasing addition unit 141 and a phasing addition unit 142. The phasing addition unit 141 generates a sound ray signal (hereinafter referred to as sound ray signal_1) that does not include a grating lobe and includes only a signal derived from the main lobe, and the phasing addition unit 142 includes a grating lobe in each direction. A sound ray signal (hereinafter referred to as sound ray signal_2) is generated. The sound ray signal_1 corresponds to the first sound ray signal of the present invention, and the sound ray signal_2 corresponds to the second sound ray signal of the present invention.

  The phasing adder 141 and the phasing adder 142 acquire the reception signal for the ultrasonic beam transmitted so that the grating lobe is generated in the image area as described above from the reception unit 13, and Perform phasing addition. More specifically, the phasing adder 141 and the phasing adder 142 adjust the time phase by providing a delay time for each individual path corresponding to each transducer 2a, and add these to generate sound ray data. To do. Here, the phasing adder 141 and the phasing adder 142 have different delay times.

  More specifically, the phasing adder 141 and the phasing adder 142 perform the following processing. The phasing / adding unit 141 performs phasing / addition with respect to the received signal at a delay time in which element grouping is not performed, and generates a sound ray signal_1. On the other hand, the phasing / adding unit 142 performs phasing / addition with respect to the received signal at the delay time in which element grouping is performed, and generates a sound ray signal_2. That is, the sound ray signal_2 is a sound ray signal generated by performing the same number of element groupings at the time of transmission and reception, and a grating lobe is generated in the same direction during transmission and reception. Therefore, the sound ray signal_2 is added to the component derived from the main lobe. It becomes a sound ray signal including a component derived from lobes.

  The phasing addition unit 142 only needs to operate when the above-described needle emphasis mode is selected.

  The signal processing unit 15 is a circuit that performs various processes on the sound ray signal generated by the sound ray signal generation unit. As shown in FIG. 2, the signal processing unit 15 includes a harmonic component extraction unit 151, a grating signal extraction unit 152, a high echo region extraction unit 153, a frequency analysis unit 154, a coordinate calculation unit 155, and an image generation unit 156.

  When applying the tissue harmonic imaging, the harmonic component extraction unit 151 performs a pulse inversion method on the sound ray signal_1 to extract a harmonic component. In the present embodiment, it is assumed that the harmonic component extraction unit 151 extracts the second harmonic component. More specifically, the harmonic component extraction unit 151 adds (synthesizes) the first received signal and the second received signal, and removes the fundamental wave component included in the added sound ray signal, as necessary. The second harmonic component is extracted by performing filtering. Whether or not to apply tissue harmonic imaging may be determined based on, for example, an operation on the operation input unit 11 or may be determined to be applied compulsorily.

  When the needle emphasis mode is selected, the grating signal extraction unit 152 includes the sound ray signal_1 including only the main lobe component without including the grating lobe component, and the sound ray signal including both the main lobe component and the grating lobe component. Based on _2, only the grating lobe component is extracted. Specifically, the grating signal extraction unit 152 multiplies and subtracts the sound ray signal_1 by a predetermined coefficient from the sound ray signal_2 to obtain a sound ray signal including only the grating lobe component (hereinafter referred to as the sound ray signal_3). Generate). Here, the grating signal extraction unit 152 may change a coefficient to be multiplied by the sound ray signal_1 according to the intensity ratio of the main lobe component included in each of the sound ray signal_1 and the sound ray signal_2. A predetermined fixed coefficient may be used.

  The grating signal extraction unit 152 may extract only the grating lobe component using the sound ray signal added by the harmonic component extraction unit 151, but the sound ray signal_2 due to the sound pressure dependency of the harmonic generation. Therefore, it is desirable to extract only the grating lobe component using only the sound ray signal before addition, that is, the fundamental wave signal.

  Further, the grating signal extraction unit 152 may perform extraction processing of only the grating lobe component on both or either one of the first reception signal and the second reception signal. Which of the first received signal and the second received signal is to be subjected to the extraction process may be determined as follows. That is, for example, when it is important to focus on the S / N ratio, the extraction process is performed on both received signals, and when it is desired to reduce the processing load, the extraction process is performed on one of the received signals. It may be determined based on the device request.

  When the extraction process is performed for both the first reception signal and the second reception signal with an emphasis on the S / N ratio, the grating signal extraction unit 152 performs a subtraction process, for example, at the stage of sound ray information having phase information. By performing the above, even-order harmonics such as second-order harmonics are canceled out, and the fundamental wave and odd-order harmonic components can be doubled and extracted. In this subtraction process, either (first received signal)-(second received signal) or (second received signal)-(first received signal) may be performed. Since the odd-order harmonics are hardly generated in the grating lobe whose sound pressure is lower than that of the main lobe, it is possible to obtain the fundamental wave signal derived from the grating lobe having substantially twice the signal intensity by the above method.

  Alternatively, the grating signal extraction unit 152 may employ a method in which detection processing is performed on the first reception signal and the second reception signal, and an absolute value signal having no phase information is added and then added. In this case, in principle, a signal including a fundamental wave and harmonics of both the even and odd orders is obtained with twice the signal intensity. However, as described above, the sound pressure is low in the grating lobe and Since the generation is small, it is possible to obtain a reception signal mainly composed of a fundamental wave.

  The high echo region extraction unit 153, the frequency analysis unit 154, and the coordinate calculation unit 155, when the needle enhancement mode is selected, the sound ray signal_3 including only the components derived from the grating lobe extracted by the grating signal extraction unit 152 Based on the above, the reflected echo of the puncture needle is extracted, and the position of the puncture needle is specified. Details of the processing of each component are as follows.

  The high echo area extraction unit 153 performs a process of extracting a high echo area having an intensity equal to or higher than a predetermined threshold value for the sound ray signal_3. In the present invention, the extraction process of the high echo area is not essential, but since the direct reflection intensity of the puncture needle is higher than that of many biological tissues, the extraction process of the high echo area is performed by a frequency analysis calculation by the frequency analysis unit 154 in the subsequent stage. It is effective to reduce the load. The extraction threshold value in the high-echo region extraction process may be a fixed value determined in advance, or may be any method that is adaptively determined based on the maximum value of the received signal for one sound ray.

  The frequency analysis unit 154 performs frequency analysis such as Fast Fourier Transform (FFT) on the sound ray signal_3 and outputs the result. When performing frequency analysis on the high echo area extracted by the high echo area extraction unit 153, the frequency analysis unit 154 performs analysis including the area around the extracted high echo area (before and after in the time axis). It is preferable. Further, the frequency analysis unit 154 may perform thinning (decimation processing) before performing frequency analysis. When performing decimation processing, the frequency analysis unit 154 needs to perform processing within a range that does not affect the frequency region to be analyzed and select the number of transmission data so as to satisfy the necessary frequency resolution. Further, when the extracted high echo areas are close to each other, the frequency analysis unit 154 sets the analysis areas so that they do not overlap each other. Here, it is more preferable that the frequency analysis unit 154 devise such as outputting frequency values for the number of high echo areas included in the analysis area.

  The coordinate calculation unit 155 performs coordinate calculation processing for calculating coordinate information of a position corresponding to the puncture needle. As a calculation method of the coordinate information of the puncture needle, for example, the following method may be adopted. That is, the coordinate calculation unit 155 calculates the angle of the grating lobe reflected by the puncture needle and the distance information from the reflection point of the grating lobe on the puncture needle to the transducer 2a. Then, the coordinate calculation unit 155 calculates candidate coordinates corresponding to the position of the puncture needle based on the angle of the grating lobe and the distance information.

  The angle of the grating lobe (hereinafter referred to as the grating lobe angle) θ is obtained by the following equation (1) based on the wavelength of the transmission ultrasonic wave and the interval (element pitch) between the plurality of transducers 2a.

  In Expression (1), λ is the wavelength of the transmitted ultrasonic wave, l is the element pitch, m is the order number of the grating, and is an integer of 1 or more. The transmitting unit 12 changes the apparent element pitch by performing element grouping during transmission as described above. Specifically, for example, when two-element grouping is performed on the vibrator 2a having a pitch of 0.2 mm, the apparent element pitch is 0.2 mm × 2 = 0.4 mm. Further, when the three-element grouping is performed, the apparent element pitch is 0.2 mm × 3 = 0.6 mm. In the ultrasonic diagnostic apparatus S, the apparent element pitch is increased by performing the element grouping at the time of transmission in this way, and thereby the grating lobe is compared with the case of not performing the element grouping based on the formula (1). The angle θ can be reduced.

  In addition, since the grating lobe contributes to an artifact (virtual image), the general ultrasonic diagnostic apparatus S is designed so that the frequency λ and the element pitch of the transmission ultrasonic wave are θ> 90 °, In many cases, it is designed so that the reflection probe for the grating lobe is not received by the ultrasonic probe 2 so that the grating lobe does not occur in the image field. However, in the ultrasonic diagnostic apparatus according to the present invention, since the puncture needle is detected using the grating lobe in the needle enhancement mode, the apparent element pitch is increased by performing element grouping, and θ <90 °. Thus, the reflected echo of the grating lobe can be received by the ultrasonic probe 2.

  In the above formula (1), m, which is the order number of the grating, may be m = 1 or 2. The reason is as follows.

  The number of orders represents the number of shifts in wavelength. If 1, the shift is one wavelength, and if 2, the shift is two wavelengths. In order to generate grating lobes with a higher order number, it is necessary to increase the wave length (pulse duration) of the transmitted ultrasonic waves. Here, a long wave run length means that the overlapping degree of grating lobes is large. The large degree of overlap between the grating lobes sent in different directions means that multiple grating lobes are sent simultaneously without blind spots, so they can be inserted into the subject at various insertion angles. This is preferable because the reflected echo from the puncture needle can be received.

  Specifically, for example, it is desirable that the wave length of the waveform of the transmission ultrasonic wave is equal to or more than two waves of the lower limit frequency component of the transmission probe 6 dB band of the ultrasonic probe. This makes it possible to obtain an overlap of one wavelength or more with respect to one wavelength shift (grating order number m = 1) even at a low frequency in the band, and the S / N of the puncture needle reflected echo signal by the grating lobe. Can be improved. More specifically, the transmission method described in Japanese Patent Application Laid-Open No. 2006-214622, that is, the transmission frequency band of the ultrasonic probe includes a wide range (almost the entire range) of frequency components, so that the blind angle of the grating lobe is reduced. By using a transmission method that is substantially non-existent, the grating lobe overlap is large due to the long wave length, and the generation of nonlinear components is controlled, so that the B mode image quality by tissue harmonic imaging is good. It is possible to satisfy all of image quality, puncture needle detection angle range, and puncture needle detection S / N.

  However, when the order number of the grating is increased (shifted by three wavelengths or more), the overlap between the grating lobes is considerably reduced. In addition, as the order number m increases, θ increases and is affected by the directivity sensitivity characteristic of the vibrator 2a. For this reason, a grating lobe with m = 3 or more is not useful for detecting a puncture needle, and it is preferable to use 1 or 2 as the order number m.

  Whether the order number m is 1 or 2 can be determined based on the directivity sensitivity characteristic of the vibrator 2a. However, the transmission with the grouping number changed is performed twice (grouping number = 2 & 3) or a method of performing an angle calculation at the time of steering wave transmission performed by performing a spatial compound method and specifying an angle from both results may be adopted.

  Based on the grating lobe angle reflected by the puncture needle and the distance information from the reflection point to the transducer 2a, the coordinate calculation unit 155, for example, coordinates using the position of the transducer 2a as the origin. The coordinates of the reflection point (that is, the position of the puncture needle) in the system are calculated. Note that the coordinate calculation unit 155 may calculate the distance information from the reflection point to the transducer 2a by a calculation method well known in the art in an ultrasonic diagnostic apparatus.

  As described above, the coordinate calculation unit 155 can calculate the grating lobe angle reflected by the reflection point and the distance to the reflection point. However, as shown in FIG. 4, the grating lobes are generated symmetrically, so whether the reflection point exists on the left or right side with respect to the 0 ° direction even when the sound ray signal_3 including only the grating lobe component is used. It cannot be specified. For this reason, the coordinate calculation unit 155 first calculates the coordinates of the reflection point by the puncture needle that exists symmetrically with respect to the transmission direction of the main lobe as candidate coordinates (including the right and left coordinates) It is necessary to specify which of the left and right candidate coordinates is the coordinates of the reflection point.

  In the present embodiment, one of the following two methods is adopted as a method of specifying whether the reflection point exists at the left or right position. The first method is to specify one of the left and right by providing the user with a left enhancement and a right enhancement in the needle enhancement mode. The left needle emphasis mode is a mode that should be used when a puncture needle is inserted from the left side, for example. The right needle emphasis mode is a mode when a puncture needle is inserted from the right side. The mode to be used. The left mode and the right mode may be selected by operating the needle enhancement mode selection unit 111 of the operation input unit 11 when the user of the ultrasound diagnostic apparatus S starts the needle enhancement mode. The definition of “left” and “right” on the basis of what is defined is not particularly limited in the present invention. For example, the left side and the right side in the ultrasonic diagnostic image may be set to “left” and “right”, respectively.

  In the second method, the transmission ultrasonic beam is steered with respect to the two left and right candidate coordinates, and the frequency of the echo signal derived from the grating lobe obtained by performing the same analysis processing as described above depends on the steering angle. It is a method of specifying by using different things. When the spatial compound method is applied to improve the contrast and image quality in the B mode, the transmission ultrasonic beam is inevitably steered. Therefore, it is more preferable to adopt the second method.

  Based on the sound ray signal_1 generated by the phasing addition unit 141 of the sound ray signal generation unit 14, the image generation unit 156 performs brightness conversion after performing envelope detection processing, logarithmic amplification, gain adjustment, and the like, and receives the received signal. B-mode image data in which the intensity of the image is expressed by luminance is generated and output to the image processing conversion unit 16. The B-mode image data generation process by the image generation unit 156 is performed both when the needle emphasis mode is selected and when it is not selected.

  Note that even when the needle emphasis mode is selected and the grating signal extraction unit 152 performs the extraction processing of the grating lobe component using the fundamental wave signal without using the harmonic component, the image generation unit 156 performs the sound ray signal. The B-mode image generated using _1 is preferably an image to which tissue harmonic imaging is applied. By applying tissue harmonic imaging, due to the sound pressure dependency, in the B-mode image generated by the image generation unit 156, it is possible to reduce image quality degradation due to the grating lobe included at the time of transmission.

  The image processing conversion unit 16 is a circuit that performs various processes on the image data generated by the signal processing unit 15. As illustrated in FIG. 2, the image processing conversion unit 16 includes a straight line region extraction unit 161, a display image synthesis unit 162, and a DSC 163.

  When the needle emphasis mode is selected, the straight line region extraction unit 161 punctures from image data including only the grating lobe component generated based on the sound ray signal_3 based on the coordinates of the reflection points by the plurality of grating lobes. A straight line region that is highly likely to correspond to a needle is extracted. Then, the straight line region extraction unit 161 performs enhancement processing such as coloring and luminance amplification on the extracted straight line region, and generates needle image data indicating the puncture needle. In this case, since the optimum values of the luminance, transmittance, and color of the pixel corresponding to the puncture needle vary depending on the puncture angle and the needle diameter, it is preferable that the pixel can be changed according to the operation on the operation input unit 11, for example. As a specific method of the straight line region extraction processing in the straight line region extraction unit 161, for example, a feature amount extraction method such as Hough conversion may be employed.

  In order to facilitate extraction, the straight line region extraction unit 161 preferably performs binarization processing before Hough conversion. In addition, since the straight line region extraction unit 161 extracts continuous points instead of a single point, the pixel number filtering process may be performed so that bright points having a certain number of pixels or more are processed. Furthermore, in order to prevent the processing by the pixel number filter from becoming excessive, the straight line region extraction unit 161 may perform processing for improving extraction stability such as smoothing using a Gaussian filter or the like before the pixel number filter. Good. Further, since the puncture needle may bend instead of a complete straight line depending on the tissue state in the living body, the straight line region extraction unit 161 sets an arbitrary window around the extracted straight line region, and the continuous high-luminance component in the window May be extracted as needle image data corresponding to the puncture needle.

  The display image synthesizing unit 162 synthesizes the needle image data with the B-mode image data to generate needle emphasized image data. The synthesizing method in the display image synthesizing unit 162 is not particularly limited in the present invention. For example, an overlay display in which needle image data is superimposed and displayed on the B-mode image at an arbitrary transmittance may be used. Such overlay display is preferable from the viewpoint that the tissue information in the B-mode image data is not lost.

  The DSC 163 converts the input image data into an image signal based on a television signal scanning method, and outputs the image signal to the display unit 17. The image data input to the DSC 163 is B-mode image data when the needle enhancement mode is not selected, and is needle enhancement image data when the needle enhancement mode is selected.

  The straight line detection process in the straight line region extraction unit 161 may be performed either before or after the process of the DSC 163. For example, when polar coordinate conversion is involved, such as when a convex method or a sector method is employed, the straight line detection process is preferably performed after the process of the DSC 163.

  The display unit 17 may be a display device such as an LCD (Liquid Crystal Display), a CRT (Cathode-Ray Tube) display, an organic EL (Electronic Luminescence) display, an inorganic EL display, or a plasma display. The display unit 17 displays an ultrasonic image on the display screen according to the image signal output from the DSC 163.

  The control unit 18 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and reads various processing programs such as a system program stored in the ROM to read the RAM. The operation of each part of the ultrasonic diagnostic apparatus S is centrally controlled according to the developed program. The ROM is configured by a nonvolatile memory such as a semiconductor, and stores a system program corresponding to the ultrasonic diagnostic apparatus S, various processing programs that can be executed on the system program, various data, and the like. These programs are stored in the form of computer-readable program code, and the CPU sequentially executes operations according to the program code. The RAM forms a work area for temporarily storing various programs executed by the CPU and data related to these programs.

  As illustrated in FIG. 2, the control unit 18 includes a transmission delay generation unit 181. The transmission delay generation unit 181 sets a delay time for each individual path corresponding to each transducer 2a with respect to the transmission timing of the drive signal, and delays the transmission of the drive signal by the set delay time. Thereby, the transmission beam transmitted by the ultrasonic probe 2 is focused.

  Further, the transmission delay generation unit 181 adjusts the delay time for each individual path corresponding to each transducer 2a, thereby grouping a plurality of elements into a plurality of groups and transmitting an ultrasonic wave for each group. I do. Regarding the number of transducers 2a included in the group (number of element groupings), the angle of the generated grating lobe becomes an angle suitable for detection of the puncture needle. What is necessary is just to set beforehand so that it may become a suitable value, and the transmission delay production | generation part 181 should just set delay time so that it may transmit by the set element grouping number.

<Description of operation of ultrasonic diagnostic apparatus>
The configuration of the ultrasonic diagnostic apparatus S according to the present embodiment and the outline of each configuration have been described above. Hereinafter, an operation example of the ultrasonic diagnostic apparatus S in the needle enhancement mode will be described. FIG. 6 is a flowchart illustrating an operation example of the ultrasonic diagnostic apparatus S in the needle enhancement mode.

  In step S <b> 101, the control unit 18 determines the element grouping number based on the operation input to the operation input unit 11. The determination of the element grouping number may be set based on, for example, the setting contents of the needle emphasis mode input via the operation input unit 11. For example, the number of groupings can be changed according to the puncture angle range (low angle / high angle) to be detected. Depending on the ultrasonic probe to be used, the frequency band and the directivity sensitivity characteristic of the element are sufficiently wide, and when a necessary angle range can be covered with one type of grouping, the number of fixed groups may be used.

  In step S102, each component of the ultrasound diagnostic apparatus S performs image generation processing when the main lobe transmission direction is 0 °.

[Details of Step S102]
FIG. 7 is a flowchart for explaining the image generation process when the steer angle of the main lobe is 0 °. Hereinafter, with reference to FIG. 7, the details of the process of step S102, that is, the image generation process when the main lobe steer angle is 0 ° will be described.

  In step S201, the transmission delay generation unit 181 performs a plurality of operations when the main lobe transmission angle (steer angle) is 0 °, that is, when the main lobe of the ultrasonic beam is transmitted in a direction going straight from the ultrasonic probe 2. Delay information for each of the transducers 2a is generated. Here, the transmission delay generation unit 181 generates delay information for each transducer 2a according to the number of element groupings determined in step S101.

  In step S202, the transmission unit 12 generates a drive signal based on the delay information generated in step S201, supplies the drive signal to the ultrasonic probe 2, and transmits the transmission ultrasonic wave toward the subject.

  In step S <b> 203, the reception unit 13 receives a reception signal generated by the ultrasonic probe 2 based on the reflected echo of the transmission ultrasonic wave.

  In step S204, the phasing addition unit 141 performs phasing addition using a delay time in which element grouping is not performed based on the received signal, and generates a sound ray signal_1 that does not include a grating lobe component.

  In step S205, the phasing addition unit 142 performs phasing addition using the delay time after performing element grouping based on the received signal, and generates the sound ray signal_2 including the grating lobe component.

  In step S206, the harmonic component extraction unit 151 performs a pulse inversion method on the sound ray signal_1 generated in step S204, and extracts a harmonic component.

  In step S207, the image generation unit 156 generates B-mode image data using the extracted harmonic components. That is, the B-mode image data generated in step S207 is image data to which tissue harmonic imaging is applied. As a result, even if a grating lobe is included in the transmission ultrasonic wave transmitted in step S202, the influence on the image data of the grating lobe component is suppressed due to the sound pressure dependence of tissue harmonic imaging, and high quality (contrast B-mode image data can be generated. The B-mode image data generated in step S207 is used in step S105 shown in FIG.

  On the other hand, in step S208, the grating signal extraction unit 152 performs sound including only the grating lobe component based on the sound ray signal_1 generated in step S204 and the sound ray signal_2 generated in step S205. A line signal_3 is generated.

  In step S209, the high echo area extraction unit 153 extracts a high echo area in the sound ray signal_3.

  In step S210, the frequency analysis unit 154 performs frequency analysis on the sound ray signal_3.

  In step S211, the coordinate calculation unit 155 calculates the grating lobe angle using the above equation (1) based on the element grouping number, the element pitch, and the wavelength of the transmission ultrasonic wave determined in step S101 of FIG.

In step S212, the coordinate calculation unit 155 calculates candidate coordinates of the reflection point of the grating lobe by the puncture needle based on the sound ray signal_3. Note that, as described above, it cannot be specified in this step S212 whether the candidate coordinates exist on the left or right with respect to the transmission direction of the main lobe. Hereinafter, the left and right candidate coordinates calculated by the coordinate calculation unit 155 in step S212 are referred to as C _L (left side) and C _R (right side), respectively.

  In the flowchart shown in FIG. 7, the processes in steps S204 to S207 and the processes in steps S205 to S212 may be performed in parallel or separately.

  Returning to the description of FIG. In step S103, each component of the ultrasound diagnostic apparatus S performs image generation processing when the steer angle of the main lobe is an arbitrary steer angle x °. The steer angle x ° is preferably set at a predetermined angle depending on the shape of the ultrasonic probe and the directivity sensitivity characteristic. For example, when the spatial compound method is applied and the angle of the spatial compound is set to −10, 0, + 10 °, the steer angle x ° for performing the grating lobe angle analysis processing is −10 °, + 10 °, or both. Preferably there is. Further, when any one of a plurality of compound angles (for example, −10, 0, + 10 ° / −15, 0, + 15 °) is selected by a user operation or the like, before the needle emphasis mode selection operation is performed. More preferably, the steer angle is selected in accordance with the spatial compound angle. Thereby, even in the needle emphasis mode, it is possible to obtain a B-mode image that does not change from the image before the operation. Details of the image generation processing when the steer angle of the main lobe is an arbitrary steer angle x ° in step S103 will be described below in association with FIG.

[Details of Step S103]
FIG. 8 is a flowchart for explaining the image generation process when the steer angle of the main lobe is x °. Hereinafter, with reference to FIG. 8, the details of the process of step S <b> 103, that is, the image generation process when the main lobe steer angle is x ° will be described.

  In step S301, the transmission delay generation unit 181 transmits the main lobe of the ultrasonic beam in a direction in which the transmission angle (steer angle) of the main lobe is x °, that is, in a direction inclined by x ° from the ultrasonic probe 2. The delay information for each of the plurality of transducers 2a is generated. Here, the transmission delay generation unit 181 generates delay information for each transducer 2a according to the number of element groupings determined in step S101.

  In step S302, the transmission unit 12 generates a drive signal based on the delay information generated in step S301, supplies the drive signal to the ultrasonic probe 2, and transmits the transmission ultrasonic wave toward the subject.

  In step S303, the reception unit 13 receives a reception signal generated by the ultrasonic probe 2 based on an echo signal of a transmission ultrasonic wave.

  In step S304, the phasing addition unit 141 performs phasing addition using a delay time in which element grouping is not performed based on the received signal, and generates a sound ray signal_1 that does not include a grating lobe component.

  In step S305, the phasing addition unit 142 performs phasing addition using the delay time after element grouping based on the received signal, and generates the sound ray signal_2 including the grating lobe component.

  In step S306, the harmonic component extraction unit 151 performs a pulse inversion method on the sound ray signal_1 generated in step S304, and extracts a harmonic component.

  In step S307, the image generation unit 156 generates B-mode image data using the extracted harmonic components. That is, the B mode image data generated in step S307 is image data to which tissue harmonic imaging is applied. The B-mode image data generated in step S307 is used in step S105 shown in FIG.

  On the other hand, in step S308, the grating signal extraction unit 152 performs sound including only the grating lobe component based on the sound ray signal_1 generated in step S304 and the sound ray signal_2 generated in step S305. A line signal_3 is generated.

In step S309, the coordinate computing unit 155, calculated in step S212 in FIG. 7, the candidate coordinates _C L, _{C R} and the element pitch, element grouping number, and based on the steering angle x °, the equation (1) using the calculated angle a _L and transmitting ultrasonic waves of a frequency f _L of the grating lobe passing candidate coordinates C _L, and the grating lobe passing candidate coordinates C _R the angle a _R and transmission ultrasound of a frequency f _R To do.

In step S310, the coordinate calculation unit 155, a sound ray signal _3, the frequency _f L, based on the _{f R,} echo signal portion corresponding from transducer 2a candidate coordinates _C L, in each of the distance to the _{C R} Frequency analysis.

In step S311, the coordinate calculation unit 155 compares the reflected echo intensity with respect to the transmission ultrasonic wave with the frequency f _{L and} the reflected echo intensity with respect to the transmission ultrasonic wave with the frequency f _R based on the determination condition, and compares the candidate coordinates C _L and C _R. Which of the coordinates corresponds to the puncture needle is determined.

  Returning to the description of FIG. In step S104, the straight line region extraction unit 161 extracts a straight line region that is highly likely to correspond to the puncture needle based on the sound ray signal_3 and the coordinates corresponding to the puncture needle, and based on the straight line region. To generate needle image data.

  In step S105, the coordinate calculation unit 155 performs B-mode image data with a steer angle of 0 ° generated in step S207 shown in FIG. 7 and B-mode image data with a steer angle x ° generated in step S307 shown in FIG. And a spatial compound process for generating composite B-mode image data.

  In step S <b> 106, the display image synthesis unit 162 synthesizes the synthesized B-mode image data and the needle image data to generate needle enhanced image data.

  In step S <b> 107, the display unit 17 displays the needle emphasized image data whose scanning method has been converted by the DSC 163.

  6 to 8 described above, in the image generation process in step S102 in FIG. 6 (processes in steps S201 to S212 shown in FIG. 7) and the image generation process in step S103 in FIG. 6 (in FIG. 8). Steps S301 to S311 shown) are repeated by changing the sound ray position for each frame.

In operation of the ultrasonic diagnostic apparatus S described in connection with FIG. 8 from FIG. 6, the left and right candidate coordinates C _L of the puncture _needle, of C _R, when specifying the right or left by changing the transmission steer angle Explained. Here, when the method of specifying either left or right based on the input to the operation input unit 11 is employed, the processing after step S305 (only the grating lobe signal extraction and analysis when the main lobe steer angle is x °) is performed. Processing) is not required.

  Further, the case of performing spatial compounding has been described in the operation example of the ultrasonic diagnostic apparatus S described in relation to FIGS. When the method of specifying either left or right based on the input to the operation input unit 11 is adopted without performing spatial compounding (the first method described above), the process of step S103 shown in FIG. 6 is unnecessary.

  Further, in the operation example of the ultrasonic diagnostic apparatus S described with reference to FIG. 6 to FIG. 8, the transmission / reception is performed twice at the steer angles 0 ° and x °, and the coordinates corresponding to the puncture needle are the left and right candidate coordinates. However, the analysis may be performed by using more transmission beam steering, for example, by performing the same processing at the time of transmission / reception at −x °.

<Example>
In the above, each structure of the ultrasound diagnosing device S concerning this Embodiment was demonstrated, and the operation example of the ultrasound diagnosing device S was demonstrated. In the following, the effect of the present invention will be specifically described by giving an example (Example) when the present invention is specifically implemented and a comparative example when not implementing the present invention. The embodiments described below are merely examples of the present invention, and the present invention is not limited to these.

[Setting conditions]
First, setting conditions of the ultrasonic diagnostic apparatus used in each comparative example and corner example described below will be described.

  9A and 9B are diagrams for explaining the frequency characteristics of the ultrasonic probes used in the comparative example and the example. FIG. 9A is a diagram illustrating the frequency characteristics of the normalized sensitivity of transmission / reception of the ultrasonic probe, and FIG. 9B is a diagram illustrating the frequency characteristics of the normalized sensitivity of transmission of the ultrasound probe.

  9A and 9B, the horizontal axis represents frequency [MHz], and the vertical axis represents normalized sensitivity [dB]. The maximum value of the normalized sensitivity is 0 [dB].

  In FIG. 9A, a transmission / reception −6 dB band indicating a −6 dB sensitivity band for transmission / reception is indicated by a black double arrow, and a transmission / reception −20 dB band indicating a −20 dB sensitivity band for transmission / reception is indicated by a white double arrow. In FIG. 9A, it is assumed that the transmission / reception-20 dB band is 4.0 to 18.3 [MHz], and the center frequency FC6 of the transmission / reception-6 dB band is 10.25 [MHz].

  In FIG. 9B, a transmission -6 dB band indicating a transmission -6 dB sensitivity band is indicated by a black double arrow, and a transmission -20 dB band indicating a transmission -20 dB sensitivity band is indicated by a white double arrow. In FIG. 9B, it is assumed that the transmission −20 dB band is 3.4 to 21.3 [MHz], and the frequency TxFL6 that is the lower limit of the −6 dB transmission sensitivity band is 5.0 [MHz].

  The −6 dB element directivity sensitivity characteristics of the ultrasonic probe were 5 MHz = ± 55 °, 10 MHz = ± 30 °, and 15 MHz = ± 20 °.

  The transmission / reception conditions are as follows. Transmission was performed using a drive circuit with drive frequency = 240 MHz (delay time resolution = 4.17 nsec), and the transmission focal length was 20 mm in all cases. The number of transmission vibrators was 84 elements only in Comparative Example 3 described later, and 28 elements in the other Examples and Comparative Examples. In addition, the depth of field of image was 40 mm. The reception aperture was controlled by using a so-called dynamic focus in which the aperture is changed for each depth so that the F value is in the vicinity of 2.

  The high echo region extraction processing was performed in all of the following examples and comparative examples. The specific processing contents are as follows. That is, extraction was performed using a fixed threshold method that extracts only an echo area corresponding to a luminance of 20 or more in 8-bit image luminance.

  The drive waveform is as follows. The driving waveforms shown in FIGS. 10A and 10B were used in examples other than Example 6 described later and comparative examples. FIG. 10A is a diagram illustrating time characteristics of signal strengths of drive signals in Examples and Comparative Examples other than Example 6. FIG. 10B is a diagram showing the power spectrum of the drive signal in Examples other than Example 6 and Comparative Examples. FIG. 11A is a diagram illustrating time characteristics of signal intensity of transmission ultrasonic waves in Examples and Comparative Examples other than Example 6. Moreover, FIG. 11B is a figure which shows the power spectrum of the transmission ultrasonic wave in Examples other than Example 6, and a comparative example.

  On the other hand, the driving waveforms shown in FIGS. 12A and 12B were used only in Example 6. FIG. 12A is a diagram illustrating the time characteristics of the signal strength of the drive signal in the sixth embodiment. FIG. 12B is a diagram illustrating the power spectrum of the drive signal in the sixth embodiment. FIG. 13A is a diagram illustrating time characteristics of signal intensity of transmission ultrasonic waves in the sixth embodiment. FIG. 13B is a diagram illustrating a power spectrum of transmission ultrasonic waves according to the sixth embodiment.

  The transmission acoustic wave run length (pulse duration) was equivalent to 1.48 waves and 3.41 waves, respectively, when converted to TxFL6 (5 MHz), which is the lower limit of the −6 dB transmission sensitivity band. In other words, the wave lengths of the transmission waveforms used in the examples other than Example 6 and the comparative example are longer than the wave lengths of the transmission waveforms used in Example 6.

  The image mode was performed by tissue harmonic imaging by the pulse inversion method, and the second transmission was a waveform obtained by reversing the polarity of each driving waveform described above.

  Image synthesis by spatial compounding was performed in all of the following examples and comparative examples. Specifically, when the transmission to the front was set to 0 °, three-way space compounding was performed in which transmission and reception were performed in the directions of 0, -15 and + 15 °, respectively, and synthesis was performed.

[Comparative Example 1]
Using the setting conditions described above, normal transmission without element grouping was performed in each direction of the spatial compound. For the transmission at -15, + 15 ° direction, only the delay addition similar to that at the time of normal B-mode image generation is performed. 30 ° steer reception in the incoming direction was performed. For 30 ° steer reception, B-mode tissue harmonic imaging by the pulse inversion method was not performed, and an image composed of fundamental wave components was obtained. Tissue harmonic imaging was performed only when the first transmission was received. Then, high echo area extraction processing is performed on the echo signal of 30 ° steer reception using the above-described fixed value threshold method, and the obtained result is added and synthesized to the B-mode image data obtained by normal processing. did.

  In Comparative Example 1, since the B-mode image data was generated by the same processing as usual, a good image was obtained. However, the visibility of the puncture needle was as follows. That is, the visibility was good at 15 ° where the steer transmission / reception by the spatial compound contributes to the visualization of the puncture needle, but the visibility of the puncture needle at 30 ° greatly deteriorated even when 30 ° steer reception was performed, and 45 ° There was almost no visibility.

[Comparative Example 2]
In Comparative Example 2, an image was obtained in the same manner as in Comparative Example 1, except that the 30 ° steer reception performed at 0 ° direction transmission was performed by moving the center of the reception aperture so as to pass through the transmission focal point. . As in Comparative Example 1, there was no problem with the depiction of the B-mode image and the visibility of 15 ° puncture, but the visibility at a puncture angle of 30 ° or more was not improved. This is considered to be because, for 28 element transmission to the transmission focal point 20 mm, when 30 ° steer reception passing through the transmission focal point is performed, the center of the reception aperture is outside the end portion of the transmission aperture and deviates from the combined wavefront path. It is done.

[Comparative Example 3]
In Comparative Example 3, transmission / reception was performed by increasing the transmission aperture to 84 elements so that the aperture center of 30 ° transmission focal point passing steer reception was not outside the transmission aperture end. Conditions other than the transmission aperture are the same as in Comparative Example 2. In Comparative Example 3, since the received sound ray is in the transmission synthetic wavefront path, the puncture needle visibility at 30 ° was improved. However, there was no significant effect at 45 °. Further, since the focus dependency of the transmission beam is increased, the image quality of the B-mode image other than the vicinity of the focal point is greatly deteriorated.

[Example 1]
Hereinafter, examples when the present invention is applied will be described. In the first embodiment, in transmission delay control in the 0 ° direction, a delay time is given for every two elements by two-element grouping, and detection of a puncture needle using a grating lobe is attempted. Further, in the first embodiment, whether the coordinates corresponding to the puncture needle is one of the left and right candidate coordinates is performed by a left-right limited operation via the operation input unit 11. The other conditions are the same as in Comparative Example 1 above.

  14A and 14B are diagrams illustrating the relationship between the number of element groupings, the grating lobe angle, and the transmission frequency. FIG. 14A corresponds to the order number m = 1, and FIG. 14B corresponds to the order number m = 2. As shown in FIG. 14A, in the case of the order number m = 1 and the two-element grouping, a grating lobe of about 7.6 MHz is generated in the 30 ° direction, and the transmitted component includes this 7.6 MHz component. In other words, when the number of element groupings is 2, and a 7.6 MHz grating lobe is received, candidate coordinates for the puncture needle exist in the 30 ° direction. As described above, by extracting only the grating lobe component, an echo signal derived from the puncture needle can be obtained during 30 ° steer reception.

  For this reason, in Example 1, in addition to the case of 15 ° puncture that was also visible in Comparative Example 1, the visibility in 30 ° puncture was greatly improved. Although the visibility at 45 ° puncture is not sufficient, the image quality of the B-mode image data due to tissue harmonic imaging did not deteriorate, and the puncture needle visibility could be improved without reducing the frame rate.

[Example 2]
In the second embodiment, the steer reception performed at the time of 0 ° direction transmission is 45 ° steer reception. The other conditions are the same as in the first embodiment. As shown in FIG. 14A, in the case of the order number m = 1 and the two-element grouping, a grating lobe of about 5.4 MHz is generated in the 45 ° direction, and the transmitted component includes this 5.4 MHz component. In other words, when the number of element groupings is 2 and a grating lobe of 5.4 MHz is received, candidate coordinates of the puncture needle exist in the 45 ° direction. Since 45 ° has a smaller angle than 55 °, which is a -6 dB directivity angle sensitivity of 5 MHz, an echo signal derived from the puncture needle can be obtained during 45 ° steer reception. For this reason, in addition to the 15 ° puncture that was also visible in Comparative Example 1, the visibility at the 45 ° puncture was greatly improved. Although the visibility for 30 ° puncture is not sufficient, the image quality of the B-mode image data due to tissue harmonic imaging has not deteriorated, and the puncture needle visibility can be improved without reducing the frame rate.

[Example 3]
In the third embodiment, the reception performed at the time of 0 ° direction transmission is phasing addition reception by two-element grouping. The other conditions are the same as in the first embodiment. In the third embodiment, a fundamental wave reception signal including only a main lobe-derived component obtained by normal phasing addition from a fundamental wave reception signal including a component derived from a grating lobe in addition to the main lobe (before pulse inversion). The first received signal) is subtracted to obtain a received signal containing only components derived from the grating lobe.

  Further, in Example 3, as in Comparative Example 1, high reflection component extraction processing is performed by the fixed threshold method, frequency analysis of the obtained high echo area is performed, and the obtained frequency value and FIG. Grating angle information was obtained from the relationship between the frequency and the grating angle shown in FIG. Based on the distance information of the high echo area obtained in this way, the angle information by frequency analysis, and the left / right limited operation of the puncture direction, the process of determining the coordinates of the puncture needle in the high echo area is repeated to obtain the puncture needle image. Generated and added to the B-mode image.

  In the third embodiment, the transmission component includes any component of 7.6 MHz that generates a grating lobe at 30 ° and 5.4 MHz that generates a grating lobe at 45 °. For this reason, the echo originating in the puncture needle of any angle of 30 degrees and 45 degrees can be received. In Example 3, the position of the puncture needle can also be specified by frequency analysis and left and right limited operation. For this reason, in Example 3, the visibility of the puncture needle could be improved without degrading the B-mode image data and without reducing the frame rate at any angle of 30 ° and 45 °. When the order number m = 2, as shown in FIG. 14B, in the ultrasonic probe 2 used in Example 3, the grating angle is substantially larger than the −6 dB directivity angle sensitivity angle. Since it is understood that transmission / reception cannot be performed (θ = 90 ° is exceeded and a reflected echo cannot be received), the angle can be determined without the need for discrimination between m = 1 and m = 2.

[Example 4]
In the fourth embodiment, not only at 0 ° direction transmission but also at −15 ° and + 15 ° spatial compound steer transmission / reception includes grating lobe by phasing addition reception in which 2-element grouping is performed in addition to normal phasing addition reception Echo reception, signal extraction from grating lobe only, and coordinate determination processing by frequency analysis were performed. The other conditions are the same as in Example 3 except that the left / right limited operation in the puncture direction is not performed. That is, in Example 4, the left / right discrimination of the puncture direction was performed by combining the frequency analysis result of 0 ° direction transmission and the frequency analysis result at the time of steer transmission / reception of −15 ° and + 15 °.

  Specifically, when frequency analysis is performed on a signal derived from a grating lobe in the 0 ° direction, it can be seen that if a frequency of 7.6 MHz is obtained, the puncture needle angle is 30 °. Cannot be determined. However, for example, at the time of + 15 ° transmission / reception (toward the left on the display screen), if the frequency of the grating lobe derived from the same distance is 5.4 MHz by performing the frequency analysis of the grating lobe in the same manner as the 0 ° direction, +15 Since the angle between the transmission and reception is 45 °, it can be determined that the position of the puncture needle is on the right side on the display screen. On the other hand, if the puncture needle is on the left side of the display screen, the angle formed by the + 15 ° transmission / reception is 15 °, and therefore a 5.4 MHz grating lobe-derived echo cannot be obtained. For this reason, it can be determined that the position of the puncture needle is not on the left side of the display screen.

  Thus, in Example 4, the image quality of the B-mode image data is not deteriorated, and there is no need for the left and right limited operations, and the puncture needle visibility is improved at any angle without reducing the frame rate. I was able to.

[Example 5]
In Example 5, straight line extraction processing by Hough transformation was performed at the time of puncture needle image generation, and this was combined with B-mode image data. The other conditions are the same as in Example 4. By such straight line extraction processing, image synthesis derived from tissue that is not a straight line is suppressed in the high echo area, and thus the visibility of the puncture needle is improved as compared with Example 4.

[Example 6]
In Example 6, as described above, the transmission waveforms shown in FIGS. 12A and 12B and FIGS. 13A and 13B were used. The transmission waveform used in Example 6 has a shorter wave run length than the transmission waveforms used in Comparative Examples 1 to 3 and Examples 1 to 5 shown in FIGS. 10A and 10B and FIGS. 11A and 11B. ing. The other conditions are the same as in Example 4.

  In the sixth embodiment, the frequency component necessary for receiving the grayy glove is included in the transmission waveform, and the same effect as in the fourth embodiment can be obtained. As the wave length of the transmission waveform is shortened, the echo intensity of the reflection grating lobe by the puncture needle which is the combined wavefront of one wavelength shift is reduced, and the puncture needle visibility is slightly lowered as compared with the fourth embodiment. . However, compared with Comparative Examples 1 to 3, the puncture needle visibility is greatly improved.

<Image quality evaluation>
Various index values of the drive signals and transmission ultrasonic waves of Comparative Examples 1 to 3 and Examples 1 to 6 described above, and image data generated using the drive signals and transmission ultrasonic waves in the ultrasonic diagnostic apparatus S The image quality evaluation results of the ultrasonic images are shown in Table 1 below.

  In Table 1 above, the visibility of the puncture needle in the “Puncture Needle Visibility” column of the “Image Evaluation Result” column was evaluated as follows. That is, using a 24-gauge puncture needle, puncture the pork thigh meat while securing the center of the slice using a puncture guide whose puncture angle is arbitrarily variable. Ten orthopedic surgeons performing a puncture procedure on a scoring scale scored out of 10 points. Finally, the average value was used as the image evaluation result of the puncture needle visibility.

  In addition, the evaluation of the image quality of the B-mode image data shown in the “B-mode image quality” column in Table 1 was performed as follows. That is, apart from the puncture needle visibility evaluation, the same subject's shoulder rotator cuff was observed under the same conditions. As with the visibility of the puncture needle, 10 orthopedic surgeons scored 10 points out of 10 in this case. Finally, the average value was used as the evaluation result of the B-mode image quality.

  In addition, the comprehensive evaluation shown in the “Comprehensive Score” column in Table 1 above is a comprehensive evaluation in consideration of the necessity of the right / left limited operation in addition to the evaluation of the image quality of the B-mode image data and the puncture needle visibility. Evaluation was made by 10 orthopedic surgeons on a 10-point scale, and the average value was taken as the total score.

The evaluation criteria of these “image evaluation result column” and “total score” column are as follows.
10: Descriptive performance that is satisfactory for grasping the organizational status 8: Descriptive capability that is practically acceptable for grasping the organizational status 6: Descriptive capability that is not satisfactory but is capable of grasping the organizational status 4 : Rendering ability with a certain degree of difficulty in grasping the organizational state 2: Rendering ability to the extent that it is difficult to grasp the organizational state

  As described above, according to the first to sixth embodiments of the ultrasonic diagnostic apparatus S according to the present invention, the frame rate is reduced as compared with the first to third comparative examples that do not perform element grouping and do not use a grating lobe. The visibility of the puncture needle was greatly improved without doing so. At the same time, since the B-mode image data is generated based on the main lobe reception signal using tissue harmonic imaging, B-mode image data with good image quality could be obtained in any of Examples 1 to 6. In other words, there was no particular adverse effect on the image quality of the B-mode image data due to the adoption of a transmission method in which grating lobes are generated in the image field by element grouping.

  In Example 1 in which 30 ° steer reception was performed at 0 ° direction transmission, the puncture needle visibility at 30 ° was greatly improved, and in Example 2 in which 45 ° steer reception was performed, the puncture needle visibility at 45 ° was greatly improved. Further, in Examples 3 to 6 in which the reception at the time of 0 ° direction transmission was phasing addition reception by two-element grouping, the puncture needle visibility at both 30 ° and 45 ° was improved.

  Furthermore, in Examples 4 to 6, it was possible to determine in which direction the puncture needle exists in the left or right direction by utilizing two different phasing addition receptions during spatial compound steer transmission / reception. In Example 5, the overall visibility of the puncture needle was improved by performing straight line detection by Hough conversion. In Example 6, transmission / reception similar to that of Example 4 was performed using a transmission waveform having a short wave length, but the visibility was somewhat reduced compared to Example 4 because the wave length was shortened. Compared with Comparative Examples 1 to 3, it was greatly improved.

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The ultrasonic diagnostic apparatus of the present invention includes an ultrasonic probe that transmits transmission ultrasonic waves and receives reflected ultrasonic waves toward a subject into which a specular reflector such as a puncture needle is inserted. An ultrasonic diagnostic apparatus, which generates a drive signal and outputs it to each of a plurality of transducers included in the ultrasonic probe, thereby transmitting the transmission ultrasonic wave from the transducer; A transmission delay generation unit that controls the delay time of the drive signal for each transducer so that a grating lobe is generated in addition to the main lobe in the image field, and a reception signal is received from each of the plurality of transducers. Only a component derived from the grating lobe is extracted from the sound ray signal, a sound ray signal generating portion that generates a sound ray signal by phasing and adding reception signals from the plurality of transducers, Gratingro Based on the sound ray signal including only the component derived from the sphere, the angle information of the grating lobe and the distance information to the reflection point where the grating lobe is reflected by the specular reflector are calculated. Based on a signal processing unit that generates coordinate information corresponding to the position of the specular reflector, a sound ray signal including only a component derived from the grating lobe, and the coordinate information, the specular reflection indicating the specular reflector An image processing conversion unit that generates body image data.

  Further, according to the ultrasonic diagnostic apparatus of the present invention, the transmission delay generation unit controls the delay time so that transmission ultrasonic waves are transmitted simultaneously from a predetermined number of adjacent transducers.

  Further, according to the ultrasonic diagnostic apparatus of the present invention, the sound ray signal generation unit performs phasing addition on the received signal without using the delay time provided by the transmission delay generation unit, and the grating A first phasing addition unit that generates a first sound ray signal that does not include a component derived from a lobe, and performing phasing addition using the delay time provided by the transmission delay generation unit to the reception signal; A second phasing addition unit that generates a second sound ray signal including a component derived from the grating lobe.

  According to the ultrasonic diagnostic apparatus of the present invention, the signal processing unit outputs a sound ray signal including only a component derived from the grating lobe based on the first sound ray signal and the second sound ray signal. A grating signal extraction unit to be generated is included.

  Further, according to the ultrasonic diagnostic apparatus of the present invention, the signal processing unit includes a frequency analysis unit that performs frequency analysis on a sound ray signal including only components derived from the grating lobe, and a result of the frequency analysis. And a coordinate calculation unit that calculates the angle of the grating lobe and the distance information, and generates coordinate information of the specular reflector based on the angle and distance information.

  With such a configuration, transmission is performed in which a grating lobe is generated in the image field of view, and only the signal derived from the grating lobe is extracted from the received signal, and the position of the reflection point is set as the position of the specular reflector. Needle image data corresponding to the reflector can be generated. Thereby, the visibility of the specular reflector can be improved without reducing the frame rate.

  In the ultrasonic diagnostic apparatus of the present invention, the signal processing unit includes an image generation unit that generates B-mode image data indicating the inside of the subject based on the first sound ray signal, and the image processing conversion The unit includes a display image synthesis unit that synthesizes the B-mode image data and the specular reflector image data.

  Further, in the ultrasonic diagnostic apparatus of the present invention, the image processing conversion unit extracts a straight line region based on a sound ray signal including only components derived from the grating lobe and the coordinate information, and the straight line region is extracted from the mirror surface. It has a straight line region extraction unit for reflecting body image data.

  With such a configuration, it is possible to generate specular reflector image data (needle image data) with high accuracy and to generate a composite image that easily recognizes the position of the specular reflector by generating image data that emphasizes a linear region. Data can be generated.

  In the ultrasonic diagnostic apparatus of the present invention, the signal processing unit further includes a harmonic component extraction unit that extracts a harmonic component from the first sound ray signal, and the image generation unit includes the harmonic component. The B-mode image data is generated based on the above.

  With such a configuration, even when transmission is performed in which the grating lobe is generated in the image field, B-mode image data with good image quality is generated by tissue harmonic imaging that generates B-mode image data using harmonic components. be able to. That is, it is possible to improve both the visibility of the specular reflector and the image quality of the B-mode image data.

  Moreover, in the ultrasonic diagnostic apparatus of the present invention, the coordinate calculation unit is based on a reception signal for a transmission ultrasonic wave transmitted in one transmission direction and a reception signal for a transmission ultrasonic wave transmitted in a different transmission direction. Then, one of the left and right candidate coordinates of the specular reflector generated by the grating lobes transmitted symmetrically is specified as the coordinates of the specular reflector.

  With such a configuration, the coordinates of the specular reflector can be specified without selecting any of the left and right candidate coordinates.

  In the ultrasonic diagnostic apparatus of the present invention, the transmission unit sets a -20 dB ratio band of the transmission ultrasonic wave to 110% or more.

  With such a configuration, transmission / reception is possible over a wide angular range, more specifically, in a frequency range of about 5 to about 15 MHz when the center frequency is 10 MHz. In addition, with such a configuration, when the grating angle at 15 MHz is θ, a grating lobe signal within the angle range of θ to 3θ can be transmitted and received, so that the practical puncture angle range is almost covered. Is possible.

  As mentioned above, although embodiment of this invention was described referring drawings, this invention is not limited to this example. Various changes or modifications that can be conceived by those skilled in the art within the scope of the claims are also included in the technical scope of the present invention. In addition, the constituent elements in the above embodiments may be arbitrarily combined within the scope not departing from the spirit of the disclosure.

  In the above-described embodiment, the puncture needle is illustrated as an example of the specular reflector, but the present invention is not limited to this, and can be applied to, for example, a catheter or the like.

  The present invention is suitable for an ultrasonic diagnostic apparatus that renders a specular reflector such as a puncture needle in real time.

DESCRIPTION OF SYMBOLS S Ultrasonic diagnostic apparatus 1 Ultrasonic diagnostic apparatus main body 11 Operation input part 111 Needle emphasis mode selection part 12 Transmission part 13 Receiving part 14 Sound ray signal generation part 141 Phasing addition part 142 Phasing addition part 15 Signal processing part 151 Harmonic Component extraction unit 152 Grating signal extraction unit 153 High echo region extraction unit 154 Frequency analysis unit 155 Coordinate operation unit 156 Image generation unit 16 Image processing conversion unit 161 Linear region extraction unit 162 Display image synthesis unit 163 DSC
17 Display Unit 18 Control Unit 181 Transmission Delay Generation Unit 2 Ultrasonic Probe 2a Transducer 3 Cable

Claims (13)

An ultrasonic diagnostic apparatus comprising an ultrasonic probe that transmits transmission ultrasonic waves and receives reflected ultrasonic waves toward a subject into which a specular reflector is inserted,
A transmitter for transmitting the transmission ultrasonic wave from the transducer by generating a drive signal and outputting it to each of the plurality of transducers included in the ultrasound probe;
A transmission delay generator for controlling the delay time of the drive signal for each transducer so that a grating lobe is generated in addition to the main lobe in the image field;
A receiving unit that receives a reception signal from each of the plurality of transducers;
A sound ray signal generation unit that generates a sound ray signal by phasing and adding reception signals from the plurality of vibrators;
Only the component derived from the grating lobe is extracted from the sound ray signal, and based on the sound ray signal including only the component derived from the grating lobe, the frequency, angle, and the grating lobe of the grating lobe are the mirror surface. Calculating a distance information to a reflection point reflected by the reflector, and generating a coordinate information corresponding to the position of the specular reflector based on the angle and the distance information;
An image processing conversion unit that generates specular reflector image data indicating the specular reflector based on the sound ray signal including only the component derived from the grating lobe and the coordinate information;
An ultrasonic diagnostic apparatus. The transmission delay generation unit performs element grouping for controlling the delay time so that transmission ultrasonic waves are transmitted simultaneously from a predetermined number of adjacent transducers.
The ultrasonic diagnostic apparatus according to claim 1. The sound ray signal generator is
The transmission delay generation unit performs phasing addition on the reception signal using a delay time during which the element grouping is not performed, and generates a first sound ray signal that does not include a component derived from the grating lobe. A phase adder;
Second phasing for generating a second sound ray signal including a component derived from the grating lobe by performing phasing addition on the received signal using a delay time in which the transmission delay generating unit performs the element grouping. An adder;
Having
The ultrasonic diagnostic apparatus according to claim 2. The signal processing unit includes a grating signal extraction unit that generates a sound ray signal including only a component derived from the grating lobe based on the first sound ray signal and the second sound ray signal.
The ultrasonic diagnostic apparatus according to claim 3. The signal processing unit
A frequency analysis unit that performs frequency analysis on a sound ray signal including only components derived from the grating lobes;
A coordinate calculation unit that calculates the angle of the grating lobe and the distance information based on the result of the frequency analysis, and generates coordinate information of the specular reflector based on the angle and distance information;
5. The ultrasonic diagnostic apparatus according to claim 1, comprising: The signal processing unit includes an image generation unit that generates B-mode image data indicating the inside of the subject based on the first sound ray signal,
The image processing conversion unit includes a display image combining unit that combines the B-mode image data and the specular reflector image data.
The ultrasonic diagnostic apparatus according to claim 3. The image processing conversion unit extracts a linear region based on the sound ray signal including only the component derived from the grating lobe and the coordinate information, and uses the linear region as the specular reflector image data. Have
The ultrasonic diagnostic apparatus according to claim 6. The signal processing unit further includes a harmonic component extraction unit that extracts a harmonic component from the first sound ray signal,
The image generation unit generates the B-mode image data based on the harmonic component;
The ultrasonic diagnostic apparatus according to claim 6. The signal processing unit further includes a high echo region extraction unit that extracts a high echo region having an intensity equal to or higher than a predetermined threshold for a sound ray signal including only a component derived from the grating lobe,
The frequency analysis unit performs the frequency analysis only on the high echo area.
The ultrasonic diagnostic apparatus according to claim 5. The coordinate calculation unit is generated by grating lobes transmitted symmetrically based on a reception signal for a transmission ultrasonic wave transmitted in one transmission direction and a reception signal for a transmission ultrasonic wave transmitted in a different transmission direction. Identify any of the left and right candidate coordinates of the specular reflector as the coordinates of the specular reflector,
The ultrasonic diagnostic apparatus according to claim 5. The transmission unit has a -20 dB ratio band of the transmission ultrasonic wave of 110% or more.
The ultrasonic diagnostic apparatus as described in any one of Claim 1 to 10. The transmission unit sets the wave length of the waveform of the transmission ultrasonic wave to be equal to or more than two waves of the lower limit frequency component of the transmission-6 dB band of the ultrasonic probe,
The ultrasonic diagnostic apparatus as described in any one of Claims 1-11. A method for generating a specular reflector image in an ultrasonic diagnostic apparatus including an ultrasonic probe that transmits transmission ultrasonic waves and receives reflected ultrasonic waves toward a subject into which a specular reflector is inserted,
A plurality of vibrations of the ultrasonic probe having a drive signal in which a delay time is controlled for each of the plurality of vibrators of the ultrasonic probe so that a grating lobe is generated in addition to the main lobe in the image field. Outputting to each of the children to transmit the transmission ultrasonic wave from the vibrator,
A sound ray signal is generated by phasing and adding reception signals from the plurality of vibrators,
Only the component derived from the grating lobe is extracted from the sound ray signal, and based on the sound ray signal including only the component derived from the grating lobe, the angle of the grating lobe and the grating lobe are reflected by the specular reflector. Calculating distance information to the reflected reflection point, and generating specular reflector image data indicating the specular reflector based on the angle and distance information;
Specular reflector image generation method.

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