JP4557579B2 - Ultrasonic diagnostic equipment - Google Patents

Description

The present invention transmits a sound wave with a fundamental bandwidth from an ultrasonic transducer group to a subject, receives a harmonic component generated in the subject by the ultrasonic transducer group, and receives the received harmonic component as a transformer unit group The present invention relates to an ultrasonic diagnostic apparatus that displays an ultrasonic tomographic image after being boosted by an amplifier and amplified by an amplifier group.

  In recent years, the effectiveness of the ultrasonic harmonic imaging method has been confirmed in an electronic scanning ultrasonic diagnostic apparatus equipped with multiple channels of transducers. This method transmits sound waves to a living body with a fundamental bandwidth, and from the living body. The fundamental wave signal is attenuated from the received signal by a digital filter, the harmonic component generated inside the living body is extracted, and an ultrasonic diagnostic image is displayed.

  FIG. 5 is a configuration explanatory view showing a conventional ultrasonic diagnostic apparatus. In an ultrasonic diagnostic apparatus including an ultrasonic transducer group in which a plurality of ultrasonic transducers are arranged in an array or matrix, a multi-channel ultrasonic transducer is formed as one set in order to form an ultrasonic beam shape. It is necessary to send and receive. Here, an example in which a set of N channels is provided will be described.

That is, the signal generated from the reference clock generator 11 that determines the operation timing of the ultrasonic diagnostic system and the signal from the system control unit 12 that controls the system under the conditions set on the operation panel or the like are sent to the transmission delay circuit group 13. Is output. The transmission delay circuit group 13 has a fundamental wave signal band for forming a transmission beam shape of an ultrasonic wave by the transmission unit group from the signal input from the reference clock generator 11 and the signal input from the system control unit 12. N signals, each having a different delay time, are generated and output to the transmitter group 14. In the transmission unit group 14, the signal input from the transmission delay circuit group 13 is an electrical signal for transmission that is amplified to a pulse waveform of several tens of volts to an amplitude necessary for transmitting a sound wave from the ultrasonic transducer. It is output to the ultrasonic transducer group 15. In the ultrasonic transducer group 15, a pulsed sound wave obtained by converting the electrical signal for transmission input from the transmission unit group 14 into ultrasonic waves by the piezoelectric transducer is transmitted to the subject. Sound waves reflected from the boundary surfaces having different acoustic impedances inside the subject are received by the ultrasonic transducer group 15 and converted into electrical signals, which are output to the voltage limiting circuit group 16. The electric signal converted by the ultrasonic transducer group 15 includes a fundamental wave component and a harmonic component. Therefore, the voltage limiting circuit group 16 takes out the received signal by limiting the amplitude of the fundamental wave component added to protect the circuit of the receiving unit due to the excessive amplitude due to the fundamental wave component sent by the transmission signal, and extracts the received signal. 17 is output. In the transformer group 17, the received signal input from the voltage limiting circuit group 16 is boosted to improve the SN ratio (signal / noise ratio) and output to the preamplifier group 18. The preamplifier group 18 amplifies the signal input from the transformer unit group 17 to a level suitable for the input dynamic range of the ADC (analog / digital conversion circuit) / delay circuit group in the subsequent stage and outputs the amplified signal to the ADC / delay circuit group 19. Is done. The ADC / delay circuit group 19 converts the analog signal input from the preamplifier group 18 into a digital signal, gives a delay time to each input signal, and outputs it to the adder 20. In the adder 20, the signals input from the ADC / delay circuit group 19 and provided with the respective delay times are added and output to the signal processing unit 21. In the signal processing unit 21, the fundamental component is attenuated by a digital filter from the signal input from the adder 20 to extract a harmonic component and output to the monitor unit 22. The monitor unit 22 displays an ultrasonic tomographic image using the harmonic component input from the signal processing unit 21.
Japanese Patent Laid-Open No. 11-188037 JP 2001-258882 A JP 2003-164456 A

  In the conventional ultrasonic diagnostic apparatus, the harmonic component level received by the ultrasonic transducer group is as small as several tens dB or less with respect to the fundamental wave component energy, and it is very important to improve the SN ratio. In order to improve the ratio, it is necessary to increase the step-up ratio of the transformer. However, although the SN ratio of a small signal is improved by increasing the step-up ratio of the transformer, the strong reflected echo signal from within the subject causes distortion in the receiving circuit after the transformer due to the step-up, and the harmonic component due to this distortion is reduced. It occurred and displayed as an artifact on the image, which was a big problem in diagnosis.

The present invention has been made in view of the above circumstances, and an ultrasonic diagnostic apparatus capable of improving signal distortion by attenuating a fundamental wave component by providing a frequency low-pass attenuation filter using the inductance of a transformer in front of an amplifier. The purpose is to provide .

According to the first aspect of the present invention, a sound wave is transmitted from a group of ultrasonic transducers to a subject at a predetermined frequency, and a reflected sound wave generated by the subject is received by the group of ultrasonic transducers to receive a received signal. In the ultrasonic diagnostic apparatus that generates and generates an ultrasonic image based on a signal component corresponding to a harmonic contained in the received signal, the received signal is boosted by a transformer group and amplified by an amplifier group. Is arranged in front of the amplifier group, and is composed of the transformer unit group and a capacitive element unit group connected in series with the ground side terminal of the primary side coil and the ground terminal of the secondary side coil of the transformer unit group. An ultrasonic diagnostic apparatus comprising a filter for attenuating at least a part of signal components corresponding to frequencies lower than the harmonic .

The ultrasonic diagnostic apparatus of the present invention improves the SN ratio by boosting a small harmonic component in the signal pass band of the frequency low-pass attenuation filter by providing a frequency low-pass attenuation filter using the inductance of the transformer before the amplifier. In addition, it is possible to improve signal distortion by attenuating a large fundamental wave component in the cut-off frequency band to prevent saturation in the amplifier.

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

  FIG. 1 is a configuration explanatory view showing an ultrasonic diagnostic apparatus according to an embodiment of the present invention. In an ultrasonic diagnostic apparatus including an ultrasonic transducer group in which a plurality of ultrasonic transducers are arranged in an array or matrix, a multi-channel ultrasonic transducer is formed as one set in order to form an ultrasonic beam shape. It is necessary to send and receive. Here, an example in which a set of N channels is provided will be described.

  That is, the signal generated from the reference clock generator 31 that determines the operation timing of the ultrasonic diagnostic system and the signal from the system control unit 32 that controls the system under the conditions set on the operation panel or the like are sent to the transmission delay circuit group 33. Is output. The transmission delay circuit group 33 has a fundamental wave signal band for forming a transmission beam shape of an ultrasonic wave by the transmission unit group from the signal input from the reference clock generator 31 and the signal input from the system control unit 32. N signals, each having a different delay time, are generated and output to the transmitter group 34. In the transmission unit group 34, the signal input from the transmission delay circuit group 33 is transmitted as an electric signal for transmission obtained by amplifying a pulse waveform of several tens of volts to an amplitude necessary for transmitting a sound wave from the ultrasonic transducer. It is output to the ultrasonic transducer group 35. In the ultrasonic transducer group 35, a pulsed sound wave obtained by converting the electrical signal for transmission input from the transmission unit group 34 into an ultrasonic wave by the piezoelectric transducer is transmitted to the subject. Sound waves reflected from the boundary surfaces having different acoustic impedances inside the subject are received by the ultrasonic transducer group 35 and converted into electrical signals, which are output to the voltage limiting circuit group 36. The electric signal converted by the ultrasonic transducer group 35 includes a fundamental wave component and a harmonic component. Therefore, in the voltage limiting circuit group 36, the amplitude of the transmission signal applied is limited to protect the circuit of the receiving unit due to the excessive amplitude transmitted by the transmission signal, and the received signal is extracted and output to the transformer unit group 37. . The transformer unit group 37 includes a transformer group 38 and a capacitive element unit group 39. That is, the terminals of the transformer primary and secondary coils that are different from the signal input / output terminals are connected (between the ground terminals), and the capacitive element of the capacitive element group 39 is connected to the connection point. Thus, a high-pass filter that is a frequency low-pass attenuation filter is configured by the self-inductance of the primary side coil and the secondary side coil and the capacitance of the capacitive element. The desired cutoff frequency of the high-pass filter is determined by the self-inductance value of the primary side coil and the secondary side coil and the capacitance value of the capacitive element. As a result, boosting can be performed at the transformer turn ratio originally intended in the signal pass band of the high-pass filter, and boosting at the transformer can be suppressed in the cut-off frequency band. In the transformer group 37, the signal in the signal pass band of the high-pass filter is boosted from the received signals input from the voltage limiting circuit group 36 to improve the SN ratio (signal / noise ratio) and output to the preamplifier group 40. The In the preamplifier group 40, the signal input from the transformer unit group 37 is amplified to a level suitable for the input dynamic range of the ADC / delay circuit group in the subsequent stage and output to the ADC / delay circuit group 41. The ADC / delay circuit group 41 converts the analog signal input from the preamplifier group 40 into a digital signal, gives a delay time to each input signal, and outputs it to the adder 42. The adder 42 adds the signals given delay times inputted from the ADC / delay circuit group 41 and outputs the added signals to the signal processing unit 43. In the signal processing unit 43, the fundamental component is attenuated by a digital filter from the signal input from the adder 42, and a harmonic component is extracted and output to the monitor unit 44. The monitor unit 44 displays an ultrasonic tomogram using the harmonic component input from the signal processing unit 43.

  The transmission delay circuit group 33, the transmission unit group 34, the ultrasonic transducer group 35, the voltage limiting circuit group 36, the transformer unit group 37, the transformer group 38, the capacitive element unit group 39, the preamplifier group 40, and the ADC. The delay circuit group 41 is configured as an ultrasonic probe.

  FIG. 2 is a characteristic diagram showing the filter characteristics of the frequency low-pass attenuation filter according to the embodiment of the present invention. FIG. 2 shows filter characteristics applied to a fundamental frequency of 2 MHz of a transmission signal with a step-up ratio of 1: 4 in the transformer group 38. The horizontal axis is the frequency unit in MHz, the vertical axis is the power (Power), the unit is dB, and the input signal (a) normalized by 0 dB of the transformer group 38 is compared with the signal at the output point of the transformer group 38 ( b) is obtained. The step-up in the transformer group 38 is 1: 1 of the transformer in the low cut-off frequency region and the turn ratio in the high pass frequency band (corresponding to 12 dB in decibel conversion). The high-pass filter, which is a low-frequency attenuation filter, has a fundamental frequency band that is a cut-off frequency region and a harmonic frequency band of an ultrasonic signal that is a pass frequency region, so that the preamplifier group 40 and the ADC / delay circuit group 41 are The harmonic component of the ultrasonic wave can be extracted without causing signal amplitude saturation.

  FIG. 3 is a circuit diagram showing a specific example of the frequency low-pass attenuation filter according to the embodiment of the present invention. In FIG. 3, the same parts as those in FIG. That is, the ultrasonic diagnostic apparatus uses a probe suitable for the diagnosis depending on the diagnosis part of the subject. The center frequencies of the probes used for these are usually varied from 1 MHz to 15 MHz. Therefore, it is necessary to switch the filter cutoff frequency of the frequency low-pass attenuation filter depending on the probe frequency used. Here, the structure provided with the means to switch the filter cutoff frequency of a frequency low-pass attenuation filter is shown.

  Different terminals (between the ground side terminals) of the primary coil and the secondary coil of the transformer of the transformer group 38 are connected, and one or more capacitors 45 of the capacitive element group 39 are connected to the connection point. Are connected in parallel, and each capacitor 45 is connected to an analog switch 46 for selecting the capacitor 45 correspondingly. One or more analog switches 46 are selected and switched by the system control unit 47. The system control unit 47 has a function of generating a signal for switching the cut-off frequency based on probe information or operation panel information. The analog switch 46 is switched by a signal from the system control unit 47 to select one or a plurality of capacitors 45. By doing so, the cutoff frequency of the frequency low-pass attenuation filter constituted by the inductances of the primary and secondary coils of the transformer of the transformer group 38 and the capacitance of the capacitor 45 is selected.

  FIG. 4 is a circuit diagram showing another specific example of the frequency low-pass attenuation filter according to the embodiment of the present invention. In FIG. 4, the same parts as those in FIG. Here, the structure provided with the means to switch the filter cutoff frequency of a frequency low-pass attenuation | damping filter with the probe frequency used is shown.

  Terminals different from the signal input / output terminals of the transformer primary side coil and secondary side coil (between the ground side terminals) are connected, and the voltage variable capacitive element 48 of the capacitive element group 39 is connected to the connection point. An output end of a DA (digital / analog) conversion unit 50 is connected to a connection point between the voltage variable capacitance element 48 and the transformer group 38 via a resistance element 49, and is connected to an input end of the DA conversion unit 50. Is connected to the system control unit 51. The system control unit 51 has a function of generating a digital signal for switching a cutoff frequency based on probe information or an operation panel of the ultrasonic diagnostic apparatus. The digital signal generated from the system control unit 51 is converted by the DA conversion unit 50. A predetermined set voltage is applied to the voltage variable capacitance element 48 through the resistance element 49 for converting into an analog signal and increasing the output impedance of the DA converter 50. The voltage variable capacitance element 48 is, for example, a variable capacitor diode or the like that exhibits a characteristic in which the capacitance value at both ends varies depending on the applied voltage value, and the inductance and voltage variable capacitance of the primary coil and secondary coil of the transformer of the transformer group 38. The filter cutoff frequency of the frequency low-pass attenuation filter constituted by the capacitance of the element 48 is set by the capacitance values at both ends of the voltage variable capacitance element 48.

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

1 is a configuration explanatory view showing an ultrasonic diagnostic apparatus according to an embodiment of the present invention. It is a characteristic view which shows the filter characteristic of the frequency low-pass attenuation filter which concerns on the example of embodiment of this invention. It is a circuit diagram which shows the specific example of the frequency low-pass attenuation | damping filter which concerns on the example of embodiment of this invention. It is a circuit diagram which shows the other specific example of the frequency low-pass attenuation | damping filter which concerns on the example of embodiment of this invention. It is structure explanatory drawing which shows the conventional ultrasonic diagnostic apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 31 ... Reference clock generator, 32 ... System control part, 33 ... Transmission delay circuit group, 34 ... Transmission part group, 35 ... Ultrasonic transducer group, 36 ... Voltage limiting circuit group, 37 ... Transformer group, 38 ... Transformer Group 39: Capacitance element group.

Claims (3)

A sound wave is transmitted from the ultrasonic transducer group to a subject at a predetermined frequency, and a reflected sound wave generated by the subject is received by the ultrasonic transducer group to generate a reception signal. In an ultrasonic diagnostic apparatus that generates an ultrasonic image based on a signal component corresponding to a harmonic included in the received signal, boosted by a group and amplified by an amplifier group,
The transformer unit group is arranged in front of the amplifier group,
The transformer unit group includes a transformer element group and a capacitive element unit group connected in series with the ground side terminal of the primary coil and the secondary coil ground terminal of the transformer unit group, and corresponds to a lower frequency than the harmonic. Comprising a filter for attenuating at least a part of the signal component ;
An ultrasonic diagnostic apparatus characterized by the above. 2. The capacitive element unit group including one or more capacitors, an analog switch that selects the capacitor, and a system control unit that controls the analog switch is used as the capacitive element unit group. The ultrasonic diagnostic apparatus as described. The capacitive element unit group includes a voltage variable capacitive element whose capacitance changes according to voltage, a digital / analog converter that is connected to the voltage variable capacitive element via a resistive element and converts a digital signal into an analog signal, and the digital The ultrasonic diagnostic apparatus according to claim 1, wherein a capacitive element unit group including a system control unit that sets a digital signal to be supplied to the analog conversion unit is used.

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