JP2007061431A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely obtain information about a movement speed by reducing the influence of noise caused by the periodical operation of equipment arranged in the periphery of an ultrasonic probe. <P>SOLUTION: A signal processing circuit 15 orthogonally detects a reflected ultrasonic signal, Fourier-transforms an orthogonal analytic signal obtained by this, and judges Doppler shift based on a component about a frequency band other than a prescribed frequency band containing OHz in the result of the Fourier transformation. A system control circuit 19 judges the operation frequency of an electric appliance (such as an insulation type switching power source 42) existing in the periphery of the probe 2 and performing the periodical operation, and sets a sampling frequency in the Fourier transformation so as to become a measure of the operation frequency. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ultrasonic diagnostic apparatus that acquires information on motion speed based on Doppler shift generated in a reflected ultrasonic signal received by an ultrasonic probe.

  An ultrasonic beam is transmitted into a subject such as a living body to display a tomographic image (B mode image) of the tissue in the living body, and an image (Doppler mode display image) representing the motion state of the moving reflector. An ultrasonic diagnostic apparatus that displays is well known. Note that the state of motion is, for example, the state of blood flow.

The B-mode image is obtained from the intensity distribution of the reflected echo signal. The Doppler mode display image is obtained from the frequency shift generated in the reflected echo signal due to the Doppler effect caused by the motion of the reflector.
JP-A-10-137243

  In recent years, with the improvement of reception sensitivity, ultrasonic diagnostic apparatuses have received weak radiated noise and propagating noise generated by electric circuits arranged inside or around the ultrasonic diagnostic apparatus together with reflected echo signals. I came. Such noise may cause significant artifacts in the Doppler mode display image and may interfere with diagnosis.

  For medical devices that make patient connections, it is necessary to ensure electrical safety. For this reason, an insulating switching power supply is often employed in the power supply circuit of this type of apparatus so as to keep the leakage current extremely low. Usually, the switching power supply is operated at a switching frequency of about several tens of kHz to several hundreds of kHz. However, since it is an insulating type, there is a possibility that interference occurs in the received echo signal. For this reason, the power supply switching noise generated in the switching circuit of the power supply circuit is mixed and interfered with the reception echo as common mode noise and becomes an artifact in the diagnostic information image.

  FIG. 9 is a diagram showing an example in which artifacts are generated on the blood flow display due to an unstable disturbance clock signal when the ultrasonic continuous wave Doppler method is executed.

  The present invention has been made in view of such circumstances, and the object of the present invention is to reduce the influence of noise caused by the periodic operation of the devices arranged around the ultrasonic probe and to reduce the movement speed. The object is to provide an ultrasonic diagnostic apparatus capable of accurately obtaining information about the above.

  In order to achieve the above object, a first aspect of the present invention provides an ultrasonic diagnostic apparatus for acquiring information on a motion speed based on a Doppler shift generated in a reflected ultrasonic signal received by an ultrasonic probe. Means for quadrature detection of the sound wave signal, means for Fourier transform of the quadrature analysis signal obtained by the quadrature detection, and the Doppler shift based on components other than the predetermined frequency band including 0 Hz of the result of the Fourier transform Determining means for determining the operating frequency of an electrical device that is present in the vicinity of the ultrasonic probe and performs periodic operation, and sets the sampling frequency in the Fourier transform to be a divisor of the operating frequency And means for performing.

  In order to achieve the above-mentioned object, the second aspect of the present invention obtains information on the motion speed based on the Doppler shift generated in the reflected ultrasonic signal received by the ultrasonic probe, and depends on the Doppler carrier frequency. In an ultrasonic diagnostic apparatus that measures the amount of Doppler shift based on a frequency spectrum within a fixed reception band, a determination unit that determines an operating frequency of an electrical device that is present around the ultrasonic probe and performs a periodic operation; Means for setting the Doppler carrier frequency so that a reception band does not include a multiple of the operating frequency.

  According to each of the above-described inventions, it is possible to reduce the influence of noise caused by the periodic operation of the devices arranged around the ultrasonic probe, and to acquire information on the motion speed with high accuracy.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a block diagram showing a configuration of an ultrasonic diagnostic apparatus 1 according to the first embodiment.

  The ultrasonic diagnostic apparatus 1 includes connector ports 10-1, 10-2,..., 10-n, probe connector selection circuits 11-1, 11-2, 11-n, a transmission drive circuit 12, a reception delay circuit 13, A phasing addition circuit 14, a signal processing circuit 15, a digital scan converter (DSC) 16, a transmission / reception circuit control circuit 17, a wireless interface (wireless I / F) 18 and a system control circuit 19 are included.

  The ultrasonic probe 2 can be connected to each of the connector ports 10-1 to 10-n. That is, the ultrasonic diagnostic apparatus 1 can connect n ultrasonic probes 2 in parallel. The probe connector selection circuits 11-1 to 11-n are connected to the connector ports 10-1 to 10-n, respectively. The probe connector selection circuits 11-1 to 11-n selectively connect the connector ports 10-1 to 10-n to the transmission drive circuit 12 and the reception delay circuit 13 under the control of the transmission / reception circuit control circuit 17. The ultrasonic probe 2 is connected to the transmission drive circuit 12 and the reception delay circuit 13 when the connection destination of the connector ports 10-1 to 10-n is selected by the probe connector selection circuits 11-1 to 11-n. Is done.

  The transmission drive circuit 12 outputs a pulse signal having a constant repetition rate (PRF: pulse rate frequency) to the ultrasonic probe 2 as an ultrasonic transmission signal. The ultrasonic probe 2 includes a plurality of transducers. The transmission drive circuit 12 can output the ultrasonic transmission signals for each of the plurality of transducers in parallel at individual timings. The transmission timing of each of the plurality of ultrasonic signals is instructed from the transmission / reception circuit control circuit 17. Upon receiving the ultrasonic transmission signal, the ultrasonic probe 2 transmits an ultrasonic beam by exciting a plurality of transducers individually. An ultrasonic echo generated by the reflection of the ultrasonic beam in the subject is received by the ultrasonic probe 2. When the ultrasonic probe 2 receives an ultrasonic echo, a plurality of transducers individually output an ultrasonic echo signal corresponding to the ultrasonic echo.

  For example, in the blood flow velocity measurement mode by the two-part steering continuous wave Doppler method using the sector type ultrasonic probe 2, about half of the vibrators provided in the ultrasonic probe 2 are continuously driven at a single frequency. Then, ultrasonic waves having a single carrier frequency are continuously transmitted from the vibrator. The remaining half of the transducers receive ultrasonic echoes generated by the moving object such as blood flow in the subject.

  The reception delay circuit 13 amplifies a plurality of ultrasonic echo signals output from the ultrasonic probe 2 and delays the signals by an individual delay amount. The delay amounts of the plurality of ultrasonic echo signals are instructed from the transmission / reception circuit control circuit 17.

  The phasing addition circuit 14 performs phasing addition of a plurality of ultrasonic echo signals. The signal processing circuit 15 processes the output signal of the phasing addition circuit 14 and acquires a B-mode image or a Doppler mode display image. For example, the signal processing circuit 15 performs envelope detection or the like for acquiring a B-mode image. Further, the signal processing circuit 15 performs quadrature detection, FFT, filtering, and the like in order to obtain a Doppler mode display image. The signal processing circuit 15 outputs an image signal representing the acquired image.

  The digital scan converter 16 includes a frame memory, a D / A converter, a write / read controller, and the like. The digital scan converter 16 converts the various scanning system image signals output from the signal processing circuit 15 into standard television scanning system image signals by independently performing writing to and reading from the frame memory. The image signal output from the digital scan converter 16 is sent to the display system 3. The display system 3 includes a TV monitor and displays an image represented by an input image signal.

  The transmission / reception circuit control circuit 17 controls the operations of the probe connector selection circuits 11-1 to 11-n, the transmission drive circuit 12, and the reception delay circuit 13 in accordance with various conditions such as a diagnostic mode and an operation direction.

  The wireless interface 18 performs wireless communication with a device (hereinafter referred to as a peripheral device) disposed around the ultrasound diagnostic apparatus 1 and the ultrasound probe 2. The peripheral device is, for example, an electrocardiograph monitor 4. The electrocardiograph monitor 4 includes a wireless interface 41 that is compatible with the wireless interface 18. In order to realize the above compatibility, it is desirable to adopt a general-purpose communication standard such as the IEEE802.11b standard. Thereby, it is possible to realize wireless communication between the ultrasonic diagnostic apparatus 1 and various peripheral devices.

  The system control circuit 19 includes a microprocessor (MPU) 19a and a memory 19b. The microprocessor 19a performs a determination process. The memory 19b stores various information. In the system control circuit 19, the microprocessor 19 a controls the operation of the ultrasonic diagnostic apparatus 1 based on the operating conditions input via a system control console (not shown) and the detailed control parameters stored in the memory 19 b. .

Next, the operation of the ultrasonic diagnostic apparatus 1 configured as described above will be described.
The ultrasonic diagnostic apparatus 1 can display a B-mode image or a Doppler mode display image on the display system 3 by the same operation as a known similar apparatus.

  For example, when blood flow velocity measurement by the ultrasonic Doppler method is performed while observing an electrocardiogram waveform of a circulatory disease patient using an electrocardiograph monitor, as shown in FIG. The electrocardiograph monitor 4 is installed in The electrocardiograph monitor 4 is equipped with an insulated switching power supply 40 so as to keep the leakage current extremely low in order to ensure electrical safety when performing patient connection. The electrocardiograph monitor 4 has a function of wirelessly transmitting switching frequency information related to the switching frequency of the insulating switching power supply 40 from the wireless interface 41. The switching frequency information may be information indicating the value of the switching frequency, or may be a trigger signal indicating the switching timing.

  Now, when a diagnostic operation using the Doppler method is activated, in the ultrasonic diagnostic apparatus 1, the system control circuit 19 executes a setting process as shown in FIG.

  In step Sa1, the system control circuit 19 inputs operating conditions via a system control console (not shown). In step Sa2, the system control circuit 19 sets various parameters for realizing the desired operation based on the input operation conditions and the detailed control parameters stored in the memory 19b. This parameter includes a sampling frequency in FFT (Fast Fourier Transform) and a Doppler carrier frequency.

  In step Sa3, the system control circuit 19 confirms whether there is a peripheral device. This is performed, for example, by searching for devices that can communicate with the wireless interface 18. If there is a peripheral device, the system control circuit 19 proceeds from step Sa3 to step Sa4. In step Sa4, the system control circuit 19 determines the switching frequency fsw of the peripheral device. The system control circuit 19 acquires switching frequency information from an external device via the wireless interface 18, and determines the switching frequency fsw based on this information. In the example of FIG. 1, the system control circuit 19 determines the switching frequency fsw based on the switching frequency information transmitted from the electrocardiograph monitor 4.

  In step Sa5, the system control circuit 19 confirms whether the sampling frequency in the FFT matches the divisor of the switching frequency fsw. If the sampling frequency does not match the divisor of the switching frequency fsw, the system control circuit 19 proceeds from step Sa5 to step Sa6. In step Sa6, the system control circuit 19 changes the sampling frequency to a divisor of the switching frequency fsw.

  Specifically, if the sampling frequency is 20 kHz and the switching frequency fsw is 22 kHz, the system control circuit 19 changes the sampling frequency to 22 kHz.

  When the sampling frequency has been changed, the system control circuit 19 ends the processing shown in FIG. If there is no peripheral device, the system control circuit 19 ends the processing shown in FIG. 2 from step Sa3.

  When the Doppler method is used, the signal processing circuit 15 performs quadrature detection on the output signal of the phasing addition circuit 14. Subsequently, the signal processing circuit 15 performs FFT processing on the orthogonal analysis signals g (t) _I and g (t) _Q subjected to the orthogonal detection. In the FFT, if the sampling frequency is 2 fs, the components in the frequency range (Nyquist frequency range) of −fs to + fs shown in FIG. 3 can be reproduced and analyzed without deterioration.

  On the other hand, in the result of FFT, a component based on the frequency fluctuation caused by the pulsation of the body tissue appears greatly in a frequency band of about ± 100 Hz. This component is not necessary for blood flow signal analysis, which is the main purpose of using the Doppler method. For this reason, the signal processing circuit 15 filters the components in the frequency band of about ± 100 Hz in the FFT result. Then, the signal processing circuit 15 obtains a Doppler shift amount based on the remaining components, and obtains speed information based on the Doppler shift amount.

  In the FFT processing, the frequency component outside the Nyquist frequency range is analyzed by changing the frequency of the signal frequency to be analyzed g (t) at the sampling frequency 2fs, although the intensity is reduced by the undersampling effect. For example, as shown in FIG. 4, when the sampling frequency is 20 kHz, the Nyquist frequency range is ± 10 kHz. Therefore, when the analyzed signal has components of +3 kHz and −5 kHz, these are components of +3 kHz and −5 kHz. As a result, it is reproduced and analyzed without deterioration of signal intensity. However, when the signal to be analyzed has a component of +22 kHz, the strength is deteriorated because it is outside the Nyquist range, but the component of +22 kHz is analyzed at 20 kHz as a component of +2 kHz.

  If the +22 kHz component is a noise component having a switching frequency due to the switching operation of the insulating switching power supply 40, this noise component will be included in the FFT result. However, as described above, the sampling frequency is adjusted to a divisor of the switching frequency. That is, if the switching frequency is +22 kHz, for example, as shown in FIG. 5, the sampling frequency is +22 kHz. As a result, as shown in FIG. 5, a noise component having a switching frequency can be reduced to a direct current (zero Hz) in the FFT result. Then, since the component in the vicinity of the direct current in the FFT result is filtered as described above, the noise component is reduced by this and is not used for acquiring the speed information.

  Thus, according to the first embodiment, speed information can be obtained with high accuracy without being affected by noise caused by the switching operation of the insulating switching power supply 40.

(Second Embodiment)
The second embodiment is realized by the ultrasonic diagnostic apparatus 1 having the same configuration as that of the first embodiment. The second embodiment is different from the first embodiment in the processing contents of the system control circuit 19 in the setting processing when a diagnostic operation using the Doppler method is activated.

In the ultrasonic diagnostic apparatus 1, when a diagnostic operation using the Doppler method is started, the system control circuit 19 executes a setting process as shown in FIG. In FIG. 6, steps that perform the same processing as in FIG. 2 are assigned the same reference numerals, and detailed descriptions thereof are omitted.

  The system control circuit 19 performs the same processing as in the first embodiment for steps Sa1 to Sa4. Then, the process proceeds from step Sa4 to step Sb1.

  In step Sb1, the system control circuit 19 checks whether or not a multiple of the switching frequency fsw is within the reception band. The reception band is determined based on the Doppler carrier frequency. Typically, the reception band is a certain range with the Doppler carrier frequency as the center frequency. For example, the Doppler carrier frequency is 2.5 MHz and the reception band is in the range of 2.5 MHz ± 25 kHz. If the multiple of the switching frequency fsw is within such a reception band, the system control circuit 19 proceeds from step Sb1 to step Sb2. In step Sb2, the system control circuit 19 changes the Doppler carrier frequency so that a multiple of the switching frequency fsw is outside the reception band.

  Specifically, if the reception band is in the range of 2.5 MHz ± 25 kHz and the switching frequency is 830 kHz, the triple of the switching frequency fsw is 2.49 MHz and falls within the reception band. Therefore, the system control circuit 19 slightly increases the Doppler carrier frequency, for example, so that 2.49 MHz is not included in the reception band.

  When the change of the Doppler carrier frequency is completed, the system control circuit 19 ends the processing shown in FIG. If there is no peripheral device, the system control circuit 19 ends the processing shown in FIG. 6 from step Sa3.

  When the Doppler method is used, the reception delay circuit 13 extracts a component in the reception band from the ultrasonic echo signal. Therefore, even if a frequency component outside the reception band is included in the ultrasonic echo signal, this component is excluded from the analysis target in Doppler processing.

  When the switching frequency fsw is 830 kHz, the third harmonic is 2490 kHz. At this time, if the Doppler carrier frequency is set to 2.5 MHz, the above-described third harmonic falls within the reception band as shown in FIG. However, in such a case, as shown in FIG. 8, the Doppler carrier frequency is changed and the third harmonic is out of the reception band. As a result, the third harmonic is excluded from analysis in Doppler processing and is not used for acquiring speed information.

  Thus, according to the second embodiment, speed information can be obtained with high accuracy without being affected by noise caused by the switching operation of the insulating switching power supply 40.

  In addition, it is possible to suppress the mixing of noise using an isolation circuit, or to remove noise using a filter circuit. However, this complicates the circuit significantly, so that the circuit can be accommodated. The problem of space and cost increase arises. According to the first or second embodiment, a sufficient effect can be achieved with a significantly simpler configuration than the above-described method.

  This embodiment can be variously modified as follows.

  The peripheral device may be a device other than the electrocardiograph monitor 4 such as an extracorporeal circulation device or a wireless communication device. The device that performs the periodic operation may be a device other than a switching power source such as a motor provided in the extracorporeal circulation device or a wireless circuit that performs a hopping operation in the wireless communication device.

  The ultrasound diagnostic apparatus 1 and the ultrasound probe 2 are also apparatuses for patient connection, and the power supply system of the ultrasound diagnostic apparatus 1 is an insulation type like the electrocardiograph monitor 4. For this reason, noise may occur due to the switching operation in the power supply system of the ultrasonic diagnostic apparatus 1, and therefore, the operation as in each of the above embodiments can be performed in consideration of the switching frequency.

  Communication with peripheral devices may be performed by wire. In this case, however, it is necessary to isolate the electrical safety.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components 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 embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a block diagram showing a configuration of an ultrasonic diagnostic apparatus 1 according to a first embodiment of the present invention. The flowchart which shows the process sequence in 1st Embodiment by the system control circuit 19 in FIG. 1 in the setting process when the diagnostic operation using a Doppler method is started. The figure which shows the sampling frequency and Nyquist frequency range in FFT. The figure which shows the example of the folding of the frequency component outside a Nyquist frequency range. The figure which shows the example of the folding of the switching frequency component after the change of a sampling frequency. The flowchart which shows the process sequence in 2nd Embodiment by the system control circuit 19 in FIG. 1 in the setting process when the diagnostic operation using a Doppler method is started. The figure which shows the example in which the 3rd harmonic of the switching frequency fsw enters in a receiving band. The figure which shows a mode that the Doppler carrier frequency was changed so that a 3rd-order harmonic might be outside a receiving band. The figure which shows the example which produced the artifact on the blood-flow display resulting from the unstable clock signal of disturbance when the ultrasonic continuous wave Doppler method is performed.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Ultrasonic diagnostic apparatus, 2 ... Ultrasonic probe, 3 ... Display system, 4 ... Electrocardiograph monitor, 10-1-10-n ... Connector port, 11-1-11-n ... Probe connector selection circuit, 12 DESCRIPTION OF SYMBOLS ... Transmission drive circuit, 13 ... Reception delay circuit, 14 ... Phased addition circuit, 15 ... Signal processing circuit, 16 ... Digital scan converter, 17 ... Transmission / reception circuit control circuit, 18 ... Wireless interface, 19 ... System control circuit, 40 ... Insulated switching power supply, 41... Wireless interface.

Claims (3)

In the ultrasonic diagnostic apparatus for acquiring information on the motion speed based on the Doppler shift generated in the reflected ultrasonic signal received by the ultrasonic probe,
Means for quadrature detection of the reflected ultrasonic signal;
Means for Fourier transforming the orthogonal analysis signal obtained by the orthogonal detection;
Means for determining the Doppler shift based on a component other than a predetermined frequency band including 0 Hz in the result of the Fourier transform;
Determining means for determining an operating frequency of an electrical device that is present around the ultrasonic probe and performs a periodic operation;
Means for setting a sampling frequency in the Fourier transform to be a divisor of the operating frequency. Information on the motion speed is acquired based on the Doppler shift generated in the reflected ultrasonic signal received by the ultrasonic probe. In the ultrasonic diagnostic equipment to measure,
Determination means for determining an operating frequency of an electrical device that is present around the ultrasonic probe and performs a periodic operation;
Means for setting the Doppler carrier frequency so that the reception band does not include a multiple of the operating frequency. Comprising communication means for wirelessly communicating with the electrical device;
The ultrasonic diagnostic apparatus according to claim 1, wherein the determination unit determines the operating frequency based on information acquired from the electrical device via the communication unit.

Images