JP2012024438A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic diagnostic apparatus which can contribute to an accurate diagnosis by increasing reception sensitivity and reducing an encoded side lobe in a balanced manner.SOLUTION: A transmitting part 12 feeds a driving signal by encoding the driving signal into a pulse signal consisting of a plurality of pulse numbers to a vibrator 2a. Then, an image processing part 14 decodes a receiving signal by performing pulse compression to the receiving signal received by a receiving part 13. Then, the image processing part 14 generates image data in a subject based on the decoded receiving signal. Then, a control part 18 measures body motion information in the subject from a plurality of image data having different frames. Then, the control part 18 determines the pulse number of the pulse signal for encoding the driving signal by the transmitting part 12 based on the measurement result of the body motion information. Then, the transmitting part 12 encodes the driving signal into the pulse signal of the pulse number determined by the control part 18.

Description

  The present invention relates to an ultrasonic diagnostic apparatus.

  Conventionally, it has a vibration probe (probe) provided with a large number of transducers (transducers) arranged, transmits and receives ultrasonic waves to and from a subject such as a living body, and receives data obtained from the received ultrasonic waves. 2. Description of the Related Art There is known an ultrasonic diagnostic apparatus that generates ultrasonic image data for each frame based on this and displays this on an image display apparatus.

  In such an ultrasonic diagnostic apparatus, a pulse signal encoding technique is employed as means for increasing the reception sensitivity. In this encoding technique, a pulse wave is extended in the time axis direction to form a plurality of pulse waves, and ultrasonic waves generated thereby are transmitted to the subject, and then the pulse waves obtained from the received reflected ultrasonic waves are The gain is increased by compressing in the time axis direction using a correlation function.

  When compressing a pulse wave, it is known that side lobes (encoded side lobes) appear. However, such encoded side lobes appear in the image as an artifact, which hinders accurate diagnosis. In addition to being a cause of misjudgment, it is required to suppress coding side lobes as much as possible.

In view of such problems, for example, there is a conventional ultrasonic diagnostic apparatus that reduces the encoded side lobe by performing pulse compression using a filter that is inconsistent with the encoded code (for example, Patent Documents). 1, 2).
In addition, there is a technique that generates and transmits a weighted chirp wave in order to reduce encoded side lobes (for example, Patent Document 3).

JP 11-309146 A U.S. Pat. No. 7,423,312 JP 2002-45359 A

  However, in any of the above-mentioned patent documents, even if the encoding side lobe can be reduced theoretically, it is difficult to completely suppress the encoding side lobe in actual use. This is because it is preferable to increase the number of pulses as much as possible in order to increase the reception sensitivity. However, the larger the number of pulses, the more affected by the movement of the subject and the operation of the vibration probe by the user. This is because the waveform of the reflected ultrasonic wave is likely to be disturbed, and when the pulse compression is performed, it is impossible to suppress the encoded side lobe as intended.

  An object of the present invention is to provide an ultrasonic diagnostic apparatus capable of contributing to accurate diagnosis by improving the reception sensitivity and reducing the encoding side lobe in a balanced manner.

In order to solve the above problems, the invention according to claim 1 is an ultrasonic diagnostic apparatus,
An ultrasonic probe having a transducer that outputs a transmission ultrasonic wave toward a subject by a drive signal, converts a reflected ultrasonic wave from the subject into a pulse signal, and outputs it as a reception signal;
A transmission unit that encodes the drive signal into a pulse signal composed of a plurality of pulses and supplies the pulse signal to the vibrator;
A receiving unit for receiving a reception signal output from the vibrator;
An image processing unit that performs pulse compression on the received signal received by the receiving unit and decodes the generated signal, and generates image data in the subject based on the decoded received signal;
A body motion information measuring unit for measuring body motion information in the subject from a plurality of image data having different frames;
Based on the measurement result of the body motion information by the body motion information measurement unit, a control unit that determines the number of pulses of the pulse signal for encoding the drive signal by the transmission unit;
With
The transmission unit encodes the drive signal into a pulse signal having the number of pulses determined by the control unit.

The invention according to claim 2 is the ultrasonic diagnostic apparatus according to claim 1,
The transmitter is characterized by performing encoding using a Barker code.

The invention according to claim 3 is the ultrasonic diagnostic apparatus according to claim 1,
The transmission unit performs encoding using a Golay code.

The invention according to claim 4 is the ultrasonic diagnostic apparatus according to claim 1,
The transmitter performs encoding with a chirp pulse whose frequency changes depending on time,
The controller may determine the number of pulses of the pulse signal by determining a change width of the frequency.

  According to the present invention, it is possible to improve reception sensitivity and reduce coding side lobes in a well-balanced manner and contribute to accurate diagnosis.

It is a figure which shows the external appearance structure of the ultrasound diagnosing device in embodiment of this invention. It is a block diagram which shows schematic structure of an ultrasound diagnosing device. It is a figure explaining a Barker code. It is a block diagram which shows schematic structure of an image generation part. It is a figure explaining the pulse pattern when encoding by a Barker code | cord | chord is performed. It is a figure explaining the result of having performed pulse compression. It is a flowchart explaining a body movement information measurement process. It is a figure explaining measurement of a motion vector. It is a figure explaining a transmission pulse pattern selection table. It is a figure explaining the other example of a transmission pulse pattern selection table. It is a figure explaining a Golay code. It is a figure explaining the other example of a transmission pulse pattern selection table.

  Hereinafter, an ultrasonic diagnostic apparatus according to an embodiment of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples. In addition, in the following description, what has the same function and structure attaches | subjects the same code | symbol, and abbreviate | omits the description.

  As shown in FIGS. 1 and 2, the ultrasonic diagnostic apparatus S according to the embodiment of the present invention transmits ultrasonic waves (transmission ultrasonic waves) to a subject such as a living body (not shown), and this subject. The ultrasonic probe 2 that receives the reflected wave of reflected ultrasonic waves (reflected ultrasonic wave: echo) is connected to the ultrasonic probe 2 via the cable 3 and an electric signal is sent to the ultrasonic probe 2. By transmitting the driving signal, the ultrasonic probe 2 transmits the transmission ultrasonic wave to the subject, and in response to the reflected ultrasonic wave from the subject received by the ultrasonic probe 2. An ultrasonic diagnostic apparatus main body 1 that images the internal state of the subject as an ultrasonic image based on a reception signal that is an electrical signal generated by the ultrasonic probe 2 is configured.

  The ultrasonic probe 2 includes a transducer 2a made of a piezoelectric element, and a plurality of the transducers 2a are arranged in a one-dimensional array in the azimuth direction (scanning direction or vertical direction). In the present embodiment, the ultrasonic probe 2 including n (for example, 128) transducers 2a is used. Note that the vibrators 2a may be arranged in a two-dimensional array. Further, the number of vibrators 2a can be set arbitrarily. In this embodiment, a linear electronic scan probe is used for the ultrasound probe 2, but either an electronic scanning method or a mechanical scanning method may be used, and a linear scanning method or a sector scanning method may be used. Alternatively, any method of the convex scanning method can be adopted.

  For example, as shown in FIG. 2, the ultrasonic diagnostic apparatus main body 1 includes an operation input unit 11, a transmission unit 12, a reception unit 13, an image generation unit 14, a memory unit 15, and a DSC (Digital Scan Converter). 16, a display unit 17, and a control unit 18.

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

The transmission unit 12 is a circuit that supplies a drive signal, which is an electrical signal, to the ultrasonic probe 2 via the cable 3 under the control of the control unit 18 to generate transmission ultrasonic waves in the ultrasonic probe 2. . The transmission unit 12 includes, for example, a clock generation circuit, a delay circuit, and a pulse generation circuit. The clock generation circuit is a circuit that generates a clock signal that determines the transmission timing and transmission frequency of the drive signal. The delay circuit sets a transmission signal transmission timing for each individual path corresponding to each transducer 2a, delays transmission of the drive signal by the set delay time, and is a transmission beam constituted by transmission ultrasonic waves. This is a circuit for performing focusing. The pulse generation circuit is a circuit for generating a pulse signal as a drive signal at a predetermined cycle.
The transmission unit 12 includes a transmission pulse pattern memory 121. The transmission pulse pattern memory 121 stores a plurality of Barker codes. These Barker codes have code lengths (N) of “2”, “3”, “4”, “5”, “7”, “11”, and “13”, respectively. It is as shown in FIG.
When there is an instruction for encoding from the control unit 18, the transmission unit 12 reads the specified Barker code from the transmission pulse pattern memory 121, expands the pulse in the time axis direction, divides it into N, and reads it. The pulse generation circuit generates a pulse signal that is a pulse pattern in which positive and negative phases are given to the divided portions according to the sign elements of the Barker code. For example, a pulse pattern generated by a Barker code having a code length of “13” is as shown in FIG.
In this embodiment, a Barker code represented by a change in phase is used, but a Barker code represented by a change in frequency or amplitude may be used.

  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, a TGC (Time Gain Control), an A / D conversion circuit, and a phasing addition circuit. The TGC is a circuit for amplifying the reception signal while changing the amplification factor with the passage of time for each individual path corresponding to each transducer 2a. The A / D conversion circuit is a circuit for sampling the amplified received signal at a predetermined sampling frequency and performing A / D conversion. The phasing addition circuit adjusts the time phase by giving a delay time to each individual path corresponding to each transducer 2a with respect to the A / D converted received signal, and adds these (phasing addition) to generate a sound. It is a circuit for generating line data.

As shown in FIG. 4, the image generation unit 14 includes a decoding unit 141, a decoding template storage unit 142, an envelope detection unit 143, a logarithmic amplification unit 144, a γ correction unit 145, and the like.
The decoding unit 141 reads out a decoding template corresponding to the pulse pattern of the pulse signal transmitted by the transmission unit 12 from the decoding template storage unit 142, and performs decoding by correlation processing with the sound ray data received from the reception unit 13 ( (Pulse compression). This decoding template is reference data obtained by inverting the pulse pattern specified from the Barker code. That is, the decoding unit 141 performs pulse compression using an autocorrelation function between sound ray data and reference data. For example, when sound ray data obtained from a pulse signal encoded by a Barker code having a code length of “13” as shown in FIG. 5 is decoded, waveform data as shown in FIG. 6 is obtained. It is done. That is, as the code length is increased, the gain of the encoded main lobe increases and the encoded side lobe is suppressed. Note that when the received signal is not encoded, the signal passes through the decoding unit 141.
Then, the image generation unit 14 performs envelope detection processing by the envelope detection unit 143 on the sound ray data subjected to pulse compression by the decoding unit 141, logarithmic amplification by the logarithmic amplification unit 144, and γ correction by the γ correction unit 145. Etc. to generate B-mode image data. The B-mode image data generated in this way is transmitted to the memory unit 15.

The memory unit 15 is configured by a semiconductor memory such as a DRAM (Dynamic Random Access Memory), for example, and stores the B-mode image data transmitted from the image generation unit 14 in units of frames. That is, it can be stored as frame image data. The stored frame image data is transmitted to the DSC 16 under the control of the control unit 18.
Further, in the present embodiment, the image data of one frame before is further stored in the memory unit 15 in order to measure body movement information described later.

  The DSC 16 converts the frame image data received from the memory unit 15 into an image signal based on a television signal scanning method, and outputs the image signal to the display unit 17.

  The display unit 17 is a display device such as an LCD (Liquid Crystal Display), a CRT (Cathode-Ray Tube) display, an organic EL (Electronic Luminescence) display, and a plasma display. The display unit 17 displays an image on the display screen according to the image signal output from the DSC 16.

The control unit 18 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and reads various processing programs such as a system program stored in the ROM to read the RAM. The operation of each part of the ultrasonic diagnostic apparatus S is centrally controlled according to the developed program.
The ROM is composed of a non-volatile memory such as a semiconductor and the like, a system program corresponding to the ultrasound diagnostic apparatus S, various processing programs such as body movement information measurement processing, which will be described later, and various data that can be executed on the system program. Memorize etc. 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.

  Next, body motion information measurement processing executed in the ultrasonic diagnostic apparatus S configured as described above will be described with reference to FIG. This body movement information measurement process is, for example, a process executed every time one frame of image data is generated. Here, the body movement information is, for example, when a position change occurs in a displayed image due to a change in an internal state such as an operation of the ultrasound probe 2 or an operation of a diagnostic region within the subject. , Information indicating the amount of change. In the present embodiment, the control unit 18 functions as a body motion information measurement unit by executing the body motion information measurement process. Note that this body motion information measurement unit may be configured by hardware.

The control unit 18 reads frame image data one frame before from the memory unit 15 (step S101).
Then, the control unit 18 sets a motion vector measurement region in the read frame image data one frame before (step S102). The measurement area is set, for example, as an area predetermined by the diagnostic site. Note that the measurement area to be set may be one place or plural places. Further, the frame image data may be divided into equal areas and each area may be set as a measurement area.

Next, the control unit 18 reads the frame image data of the latest frame from the memory unit 15 (step S103).
Then, the control unit 18 sets a search area in the frame image data of the latest frame read out (step S104). The size of the search area can be set as appropriate in consideration of the moving speed of the diagnostic region and the frame rate.

Then, the control unit 18 performs band limiting filter processing on the set measurement region and search region, and smoothes noise (step S105).
Then, the control unit 18 scans the measurement region on the search region, searches for a position that best matches the image data in the measurement region by cross-correlation calculation, the minimum two-row method, and the like, A motion vector as information is measured (step S106). For example, referring to FIG. 8, the control unit 18 searches the set measurement region M on the search region S in the frame image data F of the latest frame while searching for the most consistent position. As a result, it is determined that the alignment position C is the most consistent position. Then, when the position of the measurement region M in the frame image data one frame before is the position shown in FIG. 8, the control unit 18 measures the deviation amount V between the position and the alignment position C as a motion vector. The motion vector measurement method is not limited to the above-described method, and various known methods can be applied. Further, the amount of change in the image may be measured by other methods. For example, the amount of change in the image may be measured by analyzing a histogram indicating the distribution of pixel values. Alternatively, a two-dimensional FFT (Fast Fourier Transform) may be performed on the image, and the amount of change may be measured by a change in the amplitude or phase of the spatial frequency obtained based on this. Further, a two-dimensional vector may be constituted by adjacent pixels, and the distribution may be analyzed to measure the amount of change in the image. Further, in this embodiment, the shift amount V between the measurement region M and the alignment position C is measured by measuring a motion vector that can also specify the change direction of the image in addition to the change amount of the image. A measurement method that can specify only the amount of change may be applied.

  And the control part 18 determines the code length in the case of encoding of a pulse from the measurement result of a motion vector (step S107). Specifically, referring to the transmission pulse pattern selection table shown in FIG. 9 recorded in the ROM, the code length corresponding to the measurement result is selected from the table. This transmission pulse pattern selection table is set so that the larger the motion vector, the smaller the selected code length. The selected code length is stored in the RAM, and the code length is designated to the transmission unit 12 in accordance with the transmission timing of the drive signal in the transmission unit 12. In addition, about the relationship between a motion vector and code length, you may change according to a diagnostic part etc., for example, and it can set arbitrarily. Further, the set number of code lengths may be arbitrarily set. For example, only the code length of “13” and the code length of “2” may be set, or more than the code length shown in FIG. Many code lengths may be set. In this embodiment, encoding is not performed when a motion vector of 13 pixels or more is measured, but there is no problem even if encoding is performed. In this case, it is preferable to use one having a code length as small as possible. In addition, when measuring motion vectors for multiple measurement areas, the one with the largest motion vector may be adopted as the measurement result, and the average value of the motion vectors is obtained and used as the measurement result. You may make it do. Further, although the change amount indicated by the motion vector is represented by pixels, it may be represented by millimeters, inches, or the like.

  According to the ultrasonic diagnostic apparatus S configured as described above, since the code length is set to be smaller as the motion vector is larger, the reception sensitivity is increased by increasing the code length when the body motion is small. On the other hand, the coding side lobe can be reduced by reducing the code length when the body movement is large and suppressing the waveform disturbance as much as possible.

In the present embodiment, encoding by Barker code is performed, but encoding by Golay code may be performed. In this case, the transmission pulse pattern selection table stored in the ROM of the control unit 18 can be configured as shown in FIG. 10, for example. Needless to say, the relationship between the motion vector and the code length can be arbitrarily set. In the transmission pulse pattern memory 21 in the transmission unit 12, for example, as shown in FIG. 11, a plurality of Golay codes are stored, and these Golay codes have a code length (N) of “4”, “8”, “16”, and “32”. These code elements are as shown in FIG.
Then, when there is an instruction to encode from the control unit 18, the transmission unit 12 reads the designated Golay code from the transmission pulse pattern memory 121, expands the pulse in the time axis direction, and divides it into N equal parts, In accordance with the code element (A) and the code element (B) of the read Golay code, the pulse generation circuit generates a pulse signal that is a pulse pattern in which positive and negative phases are given to the divided parts.
Then, as described above, the decoding unit 141 of the image generation unit 14 performs decoding by correlation processing. Here, decoding by the Golay code is obtained by dividing the pulse pattern into one corresponding to the code element (A) and one corresponding to the code element (B), and performing correlation processing using an autocorrelation function for each. This is done by adding the results.
In this embodiment, a Golay code represented by a change in phase is used, but a Golay code represented by a change in frequency or amplitude may be used.

Also, encoding with a chirp pulse may be performed. In this case, the transmission pulse pattern selection table stored in the ROM of the control unit 18 can be configured as shown in FIG. 12, for example. When encoding with a chirp pulse, a frequency change width corresponding to the motion vector is selected from the transmission pulse pattern selection table. Needless to say, the relationship between the motion vector and the frequency change width can be arbitrarily set.
The chirp pulse is obtained by linearly changing the frequency with the passage of time. That is, the smaller the frequency change width, the smaller the number of pulses and the shorter the pulse width. Therefore, when the frequency change width is large, the gain of the encoded main lobe can be improved, but it is easily affected by body movement. On the other hand, when the frequency change width is small, the influence of body motion can be reduced, and the encoded side lobe can be suppressed.
Then, when there is an instruction for encoding from the control unit 18, the transmission unit 12 causes the pulse generation circuit to generate a pulse signal that is a chirp pulse formed by the designated frequency change width.
Then, as described above, the decoding unit 141 of the image generation unit 14 performs decoding by correlation processing using an autocorrelation function.

  As described above, according to the embodiment of the present invention, the ultrasonic probe 2 outputs a transmission ultrasonic wave toward the subject by the drive signal, and the reflected ultrasonic wave from the subject is a pulse signal. And a vibrator 2a that outputs the received signal as a received signal. Then, the transmitter 12 encodes the drive signal into a pulse signal composed of a plurality of pulses and supplies the encoded signal to the vibrator 2a. And the receiving part 13 receives the received signal output from the vibrator | oscillator 2a. Then, the image processing unit 14 performs pulse compression on the received signal received by the receiving unit 13 and decodes it. Then, the image processing unit 14 generates image data in the subject based on the decoded received signal. Then, the control unit 18 measures body movement information in the subject from a plurality of image data with different frames. And the control part 18 determines the pulse number of the pulse signal for encoding the drive signal by the transmission part 12 based on the measurement result of body motion information. Then, the transmission unit 12 encodes the drive signal into a pulse signal having the number of pulses determined by the control unit 18. As a result, the number of pulses of the pulse signal is changed according to the measurement result of the body movement of the subject, so that the generation of coding side lobes due to the influence of the body movement can be suppressed, and reception sensitivity is improved and coding is performed. It is possible to contribute to accurate diagnosis by reducing the side lobes in a well-balanced manner.

  Further, according to the embodiment of the present invention, the transmission unit 12 performs encoding using the Barker code, and thus can effectively suppress the encoded side lobe.

  Further, according to the embodiment of the present invention, the transmission unit 12 performs encoding using the Golay code, so that it is possible to effectively suppress the encoded side lobe.

  Further, according to the embodiment of the present invention, the transmission unit 12 performs encoding using a chirp pulse whose frequency changes depending on time. Then, the control unit 18 determines the number of pulses of the pulse signal by determining the change width of the frequency. As a result, encoding side lobes can be effectively suppressed.

  The description in the embodiment of the present invention is an example of the ultrasonic diagnostic apparatus according to the present invention, and the present invention is not limited to this. The detailed configuration and detailed operation of each functional unit constituting the ultrasonic diagnostic apparatus can be appropriately changed.

  In the present embodiment, encoding is performed using a Barker code, a Golay code, or a chirp pulse, but the encoding method is not limited to these, and other methods may be used.

  In the present embodiment, an example in which a hard disk, a semiconductor nonvolatile memory, or the like is used as a computer-readable medium for the program according to the present invention is disclosed, but the present invention is not limited to this example. As another computer-readable medium, a portable recording medium such as a CD-ROM can be applied. A carrier wave is also used as a medium for providing program data according to the present invention via a communication line.

DESCRIPTION OF SYMBOLS S Ultrasonic diagnostic apparatus 1 Ultrasonic diagnostic apparatus main body 2 Ultrasonic probe 2a Transducer 12 Transmission part 121 Transmission pulse pattern memory 13 Reception part 14 Image generation part 141 Decoding part 142 Decoding template memory | storage part 18 Control part

Claims (4)

An ultrasonic probe having a transducer that outputs a transmission ultrasonic wave toward a subject by a drive signal, converts a reflected ultrasonic wave from the subject into a pulse signal, and outputs it as a reception signal;
A transmission unit that encodes the drive signal into a pulse signal composed of a plurality of pulses and supplies the pulse signal to the vibrator;
A receiving unit for receiving a reception signal output from the vibrator;
An image processing unit that performs pulse compression on the received signal received by the receiving unit and decodes the generated signal, and generates image data in the subject based on the decoded received signal;
A body motion information measuring unit for measuring body motion information in the subject from a plurality of image data having different frames;
Based on the measurement result of the body motion information by the body motion information measurement unit, a control unit that determines the number of pulses of the pulse signal for encoding the drive signal by the transmission unit;
With
The ultrasonic diagnostic apparatus, wherein the transmission unit encodes the drive signal into a pulse signal having the number of pulses determined by the control unit.   The ultrasonic diagnostic apparatus according to claim 1, wherein the transmission unit performs encoding using a Barker code.   The ultrasonic diagnostic apparatus according to claim 1, wherein the transmission unit performs encoding using a Golay code. The transmitter performs encoding with a chirp pulse whose frequency changes depending on time,
The ultrasonic diagnostic apparatus according to claim 1, wherein the control unit determines the number of pulses of the pulse signal by determining a change width of the frequency.

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