JP5756377B2 - Ultrasonic diagnostic apparatus and ultrasonic image generation method - Google Patents

Description

  The present invention relates to an ultrasonic diagnostic apparatus and an ultrasonic image generation method, and in particular, received data obtained by processing a reception signal output from an array transducer that has received an ultrasonic echo from a subject with a reception signal processing unit. The present invention relates to an ultrasonic diagnostic apparatus that generates an ultrasonic image based on the above.

  Conventionally, in the medical field, an ultrasonic diagnostic apparatus using an ultrasonic image has been put into practical use. In general, this type of ultrasonic diagnostic apparatus transmits an ultrasonic beam from an array transducer of an ultrasonic probe into a subject, receives an ultrasonic echo from the subject with the array transducer, and receives the received signal. An ultrasonic image is generated by electrical processing in the apparatus main body.

For example, Patent Document 1 discloses that received signals output from an array transducer that has received an ultrasonic echo are amplified by a preamplifier, A / D converted by an A / D converter, and converted into digital received data. In addition, there is disclosed an ultrasonic diagnostic apparatus that performs addition focusing in a state where phases are matched with each other by giving an appropriate delay, thereby performing reception focus processing.
A sound ray signal in which the focus of the ultrasonic echo is narrowed down by this reception focus processing is generated, and the tomographic image information in the subject is generated based on the plurality of sound ray signals in the diagnostic region thus generated. A B-mode image signal is generated.

In such an ultrasonic diagnosis, if there is variation in the gain of the preamplifier that amplifies the reception signals output from the array transducers, accurate reception focus processing can be performed even if the received data is phased and added. It becomes difficult.
Therefore, for example, Patent Document 2 includes an adder that adds a predetermined value to the output of the A / D converter and a multiplier that multiplies the predetermined value, thereby removing the offset contained in the received signal and receiving the signal. An ultrasonic diagnostic apparatus is disclosed that corrects for variations in preamplifier gain between signals. With such a configuration, it is possible to generate a high-quality ultrasonic image by performing an accurate reception focus process.

JP-A-4-232888 JP 2001-95805 A

  However, even if the variation in the gain of the preamplifier between the received signals is corrected, if the signal after A / D conversion is distorted due to the non-linearity of each preamplifier, the image quality of the generated ultrasonic image is reduced. As a result, the ultrasonic diagnostics with high accuracy cannot be performed.

  The present invention has been made to solve such a conventional problem, and can generate a high-quality ultrasonic image even if a preamplifier for amplifying a received signal has nonlinearity. An object of the present invention is to provide an ultrasonic diagnostic apparatus and an ultrasonic image generation method.

In the ultrasonic diagnostic apparatus according to the present invention, an ultrasonic beam is transmitted from an array transducer toward a subject, and a reception signal output from the array transducer that has received an ultrasonic echo from the subject is processed by a reception signal processing unit. An ultrasonic diagnostic apparatus that generates an ultrasonic image based on received data obtained by performing a reception signal processing unit , a preamplifier for amplifying a reception signal output from an array transducer, and a reception amplified by the preamplifier A / D converter for A / D conversion of signal, input protection circuit arranged in front of preamplifier , preamplifier non-linearity and input protection circuit for received signal A / D converted by A / D converter And a distortion correction unit that corrects distortion caused by saturation of the pre-amplifier. By referring to the correction value table created based on the input / output characteristics of the log input and the digital output from the A / D converter, the A / D converter performs correction of the received signal , and the array When the received signal output from the transducer is saturated by the input protection circuit and the saturated part is missing, it is A / D converted by the A / D converter by supplementing the missing saturated part with a half-sine waveform. The received signal is further corrected .

Distortion seen correction unit can correct the received signal by fitting a half cycle of the waveform of the sine wave to be expected from the transmit beam waveform. Alternatively, the distortion correction unit can also correct the received signal by estimating a half-cycle waveform of the sine wave based on the saturated time width of the received signal that has been A / D converted by the A / D converter. .

In the ultrasonic image generation method according to the present invention, an ultrasonic beam is transmitted from an array transducer toward a subject and a reception signal output from the array transducer that has received an ultrasonic echo from the subject is received by a reception signal processing unit. An ultrasonic image generation method for generating an ultrasonic image based on reception data obtained by processing, and a received signal output from an array transducer is amplified by a preamplifier after being input via an input protection circuit , The received signal amplified by the preamplifier is A / D converted by the A / D converter, and a correction value created based on the input / output characteristics of the analog input to the preamplifier and the digital output from the A / D converter measured in advance. By referring to the table, the preamplifier nonlinearity for the received signal A / D converted by the A / D converter With correcting distortion due to sex, when the saturation partial reception signals outputted from the array transducer saturated to an input protection circuit is lost, to compensate for the missing saturated portion at a half cycle of the waveform of a sine wave The reception data is generated by further correcting the reception signal that has been A / D converted by the A / D converter .

  According to the present invention, since the distortion correction unit corrects the distortion caused by the non-linearity of the preamplifier with respect to the reception signal A / D converted by the A / D converter, even if the preamplifier has the non-linearity. Therefore, it is possible to generate a high-quality ultrasonic image.

1 is a block diagram showing a configuration of an ultrasonic diagnostic apparatus according to Embodiment 1 of the present invention. 3 is a block diagram illustrating an internal configuration of a reception signal processing unit used in Embodiment 1. FIG. It is a figure which shows the input-output characteristic of a received signal processing part. (A) is a figure which shows an undistorted received signal waveform, (B) is a figure which shows the received signal waveform clipped at the time of saturation. 10 is a diagram illustrating a distortion correction method according to Embodiment 2. FIG. 10 is a diagram illustrating a distortion correction method according to Embodiment 3. FIG.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
Embodiment 1
FIG. 1 shows the configuration of the ultrasonic diagnostic apparatus according to the first embodiment. The ultrasonic diagnostic apparatus includes an ultrasonic probe 1 and a diagnostic apparatus main body 2 connected to the ultrasonic probe 1 by wireless communication.

  The ultrasonic probe 1 has a plurality of ultrasonic transducers 3 arranged in a one-dimensional or two-dimensional array, and a reception signal processing unit 4 is connected to each of the ultrasonic transducers 3. A wireless communication unit 6 is connected to the processing unit 4 via a parallel / serial conversion unit 5. The transmission control unit 8 is connected to the plurality of ultrasonic transducers 3 via the transmission drive unit 7, the reception control unit 9 is connected to the plurality of reception signal processing units 4, and the communication control unit 10 is connected to the wireless communication unit 6. It is connected. A probe controller 11 is connected to the parallel / serial converter 5, the transmission controller 8, the reception controller 9, and the communication controller 10.

Each of the plurality of ultrasonic transducers 3 transmits an ultrasonic wave according to a drive signal supplied from the transmission drive unit 7 and receives an ultrasonic echo from the subject to output a reception signal. Each ultrasonic transducer 3 includes, for example, a piezoelectric ceramic represented by PZT (lead zirconate titanate), a polymer piezoelectric element represented by PVDF (polyvinylidene fluoride), PMN-PT (magnesium niobate / titanate). It is constituted by a vibrator in which electrodes are formed on both ends of a piezoelectric body made of a piezoelectric single crystal represented by a lead solid solution).
When a pulsed or continuous wave voltage is applied to the electrodes of such a vibrator, the piezoelectric body expands and contracts, and pulsed or continuous wave ultrasonic waves are generated from the respective vibrators, and the synthesis of those ultrasonic waves. As a result, an ultrasonic beam is formed. In addition, each transducer generates an electric signal by expanding and contracting by receiving propagating ultrasonic waves, and these electric signals are output as ultrasonic reception signals.

The transmission drive unit 7 includes, for example, a plurality of pulsars, and based on the transmission delay pattern selected by the transmission control unit 8, the ultrasonic waves transmitted from the plurality of ultrasonic transducers 3 are transmitted to the tissue in the subject. The delay amount of each drive signal is adjusted so as to form a wide ultrasonic beam covering the area, and supplied to a plurality of ultrasonic transducers 3.
Each reception signal processing unit 4 generates a complex baseband signal by performing orthogonal detection processing or orthogonal sampling processing on the reception signal output from the corresponding ultrasonic transducer 3 under the control of the reception control unit 9. Then, by sampling the complex baseband signal, sample data including information on the tissue area is generated, and the sample data is supplied to the parallel / serial converter 5. The reception signal processing unit 4 may generate sample data by performing data compression processing for high-efficiency encoding on data obtained by sampling a complex baseband signal.
The parallel / serial converter 5 converts the parallel sample data generated by the plurality of received signal processors 4 into serial sample data.

The wireless communication unit 6 modulates a carrier based on serial sample data to generate a transmission signal, supplies the transmission signal to the antenna, and transmits radio waves from the antenna, thereby transmitting serial sample data. As the modulation scheme, for example, ASK (Amplitude Shift Keying), PSK (Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), 16QAM (16 Quadrature Amplitude Modulation), and the like are used.
The wireless communication unit 6 performs wireless communication with the diagnostic apparatus main body 2 to transmit sample data to the diagnostic apparatus main body 2 and to receive various control signals from the diagnostic apparatus main body 2. A control signal is output to the communication control unit 10. The communication control unit 10 controls the wireless communication unit 6 so that the sample data is transmitted with the transmission radio wave intensity set by the probe control unit 11, and also performs probe control on various control signals received by the wireless communication unit 6. To the unit 11.

The probe control unit 11 controls each unit of the ultrasonic probe 1 based on various control signals transmitted from the diagnostic apparatus main body 2.
The ultrasonic probe 1 includes a battery (not shown), and power is supplied from the battery to each circuit in the ultrasonic probe 1.
The ultrasonic probe 1 may be an external probe such as a linear scan method, a convex scan method, a sector scan method, or an ultrasonic endoscope probe such as a radial scan method.

  On the other hand, the diagnostic apparatus body 2 includes a wireless communication unit 21, a data storage unit 23 is connected to the wireless communication unit 21 via a serial / parallel conversion unit 22, and an image generation unit 24 is connected to the data storage unit 23. Has been. Further, a display unit 26 is connected to the image generation unit 24 via the display control unit 25. In addition, a communication control unit 27 is connected to the wireless communication unit 21, and a main body control unit 28 is connected to the serial / parallel conversion unit 22, the image generation unit 24, the display control unit 25, and the communication control unit 27. Further, an operation unit 29 for an operator to perform an input operation and a storage unit 30 for storing an operation program are connected to the main body control unit 28, respectively.

The wireless communication unit 21 transmits various control signals to the ultrasonic probe 1 by performing wireless communication with the ultrasonic probe 1. The wireless communication unit 21 outputs serial sample data by demodulating a signal received by the antenna.
The communication control unit 27 controls the wireless communication unit 21 so that various control signals are transmitted with the transmission radio wave intensity set by the main body control unit 28.
The serial / parallel converter 22 converts the serial sample data output from the wireless communication unit 21 into parallel sample data. The data storage unit 23 is configured by a memory, a hard disk, or the like, and stores at least one frame of sample data converted by the serial / parallel conversion unit 22.
The image generation unit 24 performs reception focus processing on the sample data for each frame read from the data storage unit 23 to generate an image signal representing an ultrasound diagnostic image. The image generation unit 24 includes a phasing addition unit 31 and an image processing unit 32.

  The phasing addition unit 31 selects one reception delay pattern from a plurality of reception delay patterns stored in advance according to the reception direction set in the main body control unit 28, and sets the selected reception delay pattern. Based on this, the reception focus process is performed by adding a delay to each of the plurality of complex baseband signals represented by the sample data. By this reception focus processing, a baseband signal (sound ray signal) in which the focus of the ultrasonic echo is narrowed is generated.

The image processing unit 32 generates a B-mode image signal that is tomographic image information related to the tissue in the subject based on the sound ray signal generated by the phasing addition unit 31. The image processing unit 32 includes an STC (sensitivity time control) unit and a DSC (digital scan converter). The STC unit corrects the attenuation due to the distance according to the depth of the reflection position of the ultrasonic wave on the sound ray signal. The DSC converts the sound ray signal corrected by the STC unit into an image signal according to a normal television signal scanning method (raster conversion), and performs necessary image processing such as gradation processing to thereby obtain a B-mode image signal. Is generated.
The display control unit 25 causes the display unit 26 to display an ultrasound diagnostic image based on the image signal generated by the image generation unit 24. The display unit 26 includes a display device such as an LCD, for example, and displays an ultrasound diagnostic image under the control of the display control unit 25.
The main body control unit 28 controls each unit in the diagnostic apparatus main body 2 based on various command signals and the like input from the operation unit 29 by the operator.

  In such a diagnostic apparatus main body 2, the serial / parallel conversion unit 22, the image generation unit 24, the display control unit 25, the communication control unit 27, and the main body control unit 28 are used for causing the CPU and the CPU to perform various processes. Although composed of operation programs, they may be composed of digital circuits. The operation program is stored in the storage unit 30. As a recording medium in the storage unit 30, in addition to a built-in hard disk, a recording medium such as a flexible disk, MO, MT, RAM, CD-ROM, DVD-ROM, SD card, CF card, USB memory, or server, etc. Can be used.

  Here, FIG. 2 shows an internal configuration of each received signal processing unit 4 in the ultrasonic probe 1. The received signal processing unit 4 has an input protection circuit 41 connected to the corresponding ultrasonic transducer 3, a preamplifier 42 and a variable gain amplifier 43 are sequentially connected to the input protection circuit 41, and a low pass filter 44 is connected to the variable gain amplifier 43. An A / D converter 45 is connected via Further, a distortion correction unit 46 is connected to the A / D converter 45.

The input protection circuit 41 prevents a signal having a voltage exceeding the set value from being input from the ultrasonic transducer 3 to the preamplifier 42. The preamplifier 42 statically amplifies the reception signal output from the ultrasonic transducer 3, and the variable gain amplifier 43 dynamically adjusts the gain.
The low-pass filter 44 removes high-frequency components that are not used for signal detection from the reception signals amplified by the preamplifier 42 and the variable gain amplifier 43. The A / D converter 45 converts the analog reception signal from which the high frequency component has been removed by the low-pass filter 44 into a digital signal based on the conversion start signal input from the reception control unit 9.

The distortion correction unit 46 corrects distortion caused by nonlinearity in the reception signal processing unit 4 for the reception signal A / D converted by the A / D converter 45.
As shown in FIG. 3, the input / output characteristics between the analog input S1 input to the preamplifier 42 and the digital output S2 from the A / D converter 45 are measured in advance, and the digital output S2 in the non-linear region is measured based on the measurement result. Is created on a straight line L showing a linear relationship with the analog input S1, and the correction value table is built in the distortion correction unit 46 in advance.

Next, the operation of the first embodiment will be described.
First, an ultrasonic wave is transmitted from a plurality of ultrasonic transducers 3 according to a drive signal supplied from the transmission drive unit 7 of the ultrasonic probe 1 and output from each ultrasonic transducer 3 that has received an ultrasonic echo from a subject. The received signals are supplied to the corresponding received signal processing units 4.

  The received signal passes through the input protection circuit 41 of the received signal processing unit 4, is amplified by the preamplifier 42 and the variable gain amplifier 43, and unnecessary high frequency components are removed by the low-pass filter 44. D-converted. At this time, distortion occurs in the digital output output from the A / D converter 45 in the non-linear region due to non-linearity in the reception signal processing unit 4, particularly non-linearity of the preamplifier 42 as shown in FIG. However, the distortion correction unit 46 refers to the built-in correction value table so that the digital signal from the A / D converter 45 is linearly related to the analog reception signal input to the preamplifier 42. Correct the output. For this reason, the reception signal A / D converted by the A / D converter 45 is output as sample data from the distortion correction unit 46 in a state in which distortion due to nonlinearity is corrected.

  The sample data generated in this way is serialized by the parallel / serial converter 5 and then wirelessly transmitted from the wireless communication unit 6 to the diagnostic apparatus body 2. Sample data received by the wireless communication unit 21 of the diagnostic apparatus main body 2 is converted into parallel data by the serial / parallel conversion unit 22 and stored in the data storage unit 23. Further, sample data for each frame is read from the data storage unit 23, an image signal is generated by the image generation unit 24, and an ultrasonic diagnostic image is displayed on the display unit 26 by the display control unit 25 based on the image signal. Is done.

As described above, the distortion correction unit 46 of the reception signal processing unit 4 corrects the distortion of the reception signal A / D converted by the A / D converter 45. Even if it has non-linearity, a high-quality ultrasonic image is generated.
Although distortion generated by the preamplifier 42 can be corrected at the analog signal stage before A / D conversion, a complicated analog circuit is required, which leads to an increase in power consumption in the analog unit. . In contrast, in the present invention, since the distortion correction unit 46 corrects the digital output output from the A / D converter 45, distortion correction can be performed with a simpler configuration.

  The correction value table built in the distortion correction unit 46 is created by measuring input / output characteristics of the analog input S1 input to the preamplifier 42 and the digital output S2 from the A / D converter 45 in advance. However, it is not limited to this. For example, by performing pre-scanning or the like in advance, the intensity of the ultrasonic beam transmitted from the ultrasonic transducer 3 is reduced, and reception signals without distortion are collected only in the linear region of the preamplifier 42, and thus obtained. A correction value table can also be created based on the received undistorted received signal.

Embodiment 2
Since the reception signal processing unit 4 is provided with an input protection circuit 41 for preventing a signal having a voltage exceeding the set value from being input to the preamplifier 42, the ultrasonic transducer 3 supplies the reception signal processing unit 4 to the reception signal processing unit 4. When a received signal having a voltage exceeding the set value is input, for example, a part of the received signal having a signal waveform as shown in FIG. 4A is saturated in the input protection circuit 41 and is shown in FIG. 4B. As shown, the received signal having a distorted signal waveform is clipped due to lack of the saturated portions W1 to W3. As a result, the received signal A / D converted by the A / D converter 45 also lacks the saturated portions W1 to W3.

Therefore, in the second embodiment, when the reception signal output from the ultrasonic transducer 3 is distorted by being saturated by the input protection circuit 41, the reception is A / D converted by the A / D converter 45. The distortion correction unit 46 corrects the signal so as to correct the distortion.
The distortion correction unit 46 predicts an undistorted echo waveform based on the waveform of the transmission beam from the ultrasonic transducer 3 in accordance with the drive signal supplied from the transmission drive unit 7, and fits the expected waveform to A / The received signal that has been A / D converted by the D converter 45 is corrected.

As shown in FIG. 5, the received signal clipped by the input protection circuit 41 is a signal in which a part of the sine wave having the frequency of the transmission beam is missing. Each of P3 is fitted to a reception signal A / D converted by the A / D converter 45. At this time, it is preferable to fit by fitting the period and amplitude of the waveforms P1 to P3 to the received signal as much as possible.
By doing so, the missing saturated portions W1 to W3 are compensated by the waveforms P1 to P3, and the distortion correction unit 46 can output the sample data with corrected distortion. For this reason, even when the received signal is saturated, a high-quality ultrasonic image can be generated.

Instead of fitting, it is also possible to correct the received signal by estimating an undistorted echo waveform based on the saturated time width of the received signal A / D converted by the A / D converter 45.
As shown in FIG. 6, if the time widths T1 to T3 of the saturated portion in the reception signal A / D converted by the A / D converter 45 are measured, a sine wave corresponding to the saturated portion from these time widths T1 to T3. It is possible to estimate the waveform for half a cycle. Distortion can be corrected by synthesizing the half-cycle waveform estimated in this way with the saturated portion of the received signal A / D converted by the A / D converter 45.
Even in this case, the distortion correction unit 46 can output the sample data in which the distortion is corrected, and a high-quality ultrasonic image can be generated.

  The correction when the received signal is saturated in the second embodiment can be performed together with the correction of the distortion caused by the non-linearity of the preamplifier 42 in the first embodiment, thereby generating a higher-quality ultrasonic image. Can be achieved.

  In the first and second embodiments, the ultrasonic probe 1 and the diagnostic apparatus body 2 are connected to each other by wireless communication. However, the present invention is not limited to this, and the ultrasonic probe 1 is connected to the diagnostic apparatus via a connection cable. It may be connected to the main body 2. In this case, the wireless communication unit 6 and the communication control unit 10 of the ultrasonic probe 1 and the wireless communication unit 21 and the communication control unit 27 of the diagnostic apparatus main body 2 are not necessary.

  DESCRIPTION OF SYMBOLS 1 Ultrasonic probe, 2 Diagnostic apparatus main body, 3 Ultrasonic transducer, 4 Reception signal processing part, 5 Parallel / serial conversion part, 6 Wireless communication part, 7 Transmission drive part, 8 Transmission control part, 9 Reception control part, 10 Communication Control unit, 11 Probe control unit, 21 Wireless communication unit, 22 Serial / parallel conversion unit, 23 Data storage unit, 24 Image generation unit, 25 Display control unit, 26 Display unit, 27 Communication control unit, 28 Main unit control unit, 29 Operation unit, 30 storage unit, 31 phasing addition unit, 32 image processing unit, 41 input protection circuit, 42 preamplifier, 43 variable gain amplifier, 44 low-pass filter, 45 A / D converter, 46 distortion correction unit, S1 analog input, S2 Digital output, W1-W3 saturated portion, P1-P3 half-cycle waveform, T1-T3 saturated portion time width.

Claims (4)

Based on received data obtained by processing a reception signal output from the array transducer that has received an ultrasonic echo from the array transducer while transmitting an ultrasonic beam from the array transducer toward the subject. An ultrasonic diagnostic apparatus for generating an ultrasonic image
The reception signal processing unit has a preamplifier for amplifying a received signal output from the pre SL array transducer, the received signal amplified by the preamplifier and A / D converter for converting A / D, is disposed in front of the preamplifier An input protection circuit, and a distortion correction unit that corrects distortion caused by the non-linearity of the preamplifier and saturation in the input protection circuit with respect to the reception signal A / D converted by the A / D converter,
The distortion correction unit refers to a correction value table created on the basis of input / output characteristics of an analog input to the preamplifier and a digital output from the A / D converter that are measured in advance. When the received signal output from the array transducer is saturated by the input protection circuit and the saturated portion is missing, the missing saturated portion is corrected to a sine wave. An ultrasonic diagnostic apparatus characterized by further correcting the received signal that has been A / D converted by the A / D converter by supplementing with a waveform corresponding to a half cycle . The ultrasonic diagnostic apparatus according to claim 1 , wherein the distortion correction unit corrects a reception signal by fitting a waveform corresponding to a half cycle of the sine wave expected from a transmission beam waveform. The distortion correction unit corrects a received signal by estimating a half-cycle waveform of the sine wave based on a saturated time width of the received signal A / D converted by the A / D converter. The ultrasonic diagnostic apparatus according to 1. Based on received data obtained by processing a reception signal output from the array transducer that has received an ultrasonic echo from the array transducer while transmitting an ultrasonic beam from the array transducer toward the subject. An ultrasonic image generation method for generating an ultrasonic image,
The received signal output from the array transducer is amplified by a preamplifier after being input via an input protection circuit ,
The received signal amplified by the preamplifier is A / D converted by an A / D converter,
A / D conversion is performed by the A / D converter by referring to a correction value table created based on input / output characteristics of the analog input to the preamplifier and the digital output from the A / D converter measured in advance. When the received signal output from the array transducer is saturated by the input protection circuit and the saturated portion is lost, the saturation caused by the preamplifier nonlinearity is corrected for the received signal. An ultrasonic image generation method comprising: generating the reception data by further correcting a reception signal that has been A / D converted by the A / D converter by supplementing a portion with a waveform corresponding to a half cycle of a sine wave .

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