JP2009261442A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that intrinsic noise which is called center noise is generated when electronic sector scanning is performed in an ultrasonic diagnostic apparatus. <P>SOLUTION: A noise cancellation part range is set so as to include the center noise on a beam scanning surface. When a beam direction or a focus point is included in the noise cancellation part range, gate signals 102 are output. Thus, in respective differential amplifiers 26, the noise included in reception signals are canceled by cancellation signals 106. The cancellation signals 106 are configured as output signals from a dummy vibration element 18 and a dummy signal line 14. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to a center noise cancellation process.

  Electronic sector scanning is well known as an ultrasonic beam electronic scanning method. In electronic sector scanning, a delay time corresponding to the spatial position of the transmission focus point is given to each of a plurality of transmission signals supplied to a plurality of vibration elements. Similarly, a delay time is given to a plurality of reception signals according to the reception focus point. However, at the time of reception, reception dynamic focus is generally applied, and the delay time for each reception signal is dynamically varied. In any case, the applied delay time curve (delay curve) varies depending on the deflection angle of the ultrasonic beam, and the larger the deflection angle, the larger the delay time curve having a plurality of vibration elements as a whole. Used. In other words, in the case of the center position where the beam deflection angle is zero or in the vicinity thereof, a plurality of delay times given to the plurality of vibration elements are not greatly different from each other.

  From the above, when electronic sector scanning is applied, a specific noise group called center noise is generated in the vicinity of the center line on the fan-shaped ultrasonic image (see Patent Document 1). This will be specifically described. If electromagnetic noise enters a plurality of received signals at the same timing, the electromagnetic noise also appears in the beam data after phasing addition processing. At this time, if the beam deflection angle is large, that is, if the delay time curve has a large change, the occurrence position of each electromagnetic noise is dispersed, and the electromagnetic noise is not so noticeable in the ultrasonic image. On the other hand, if the beam deflection angle is small (especially near zero) and the delay time curve has only a small change, the occurrence positions of the respective electromagnetic noises are dense, and the noise group is near the center line on the ultrasonic image. Arise. This is particularly noticeable in a deep region in the center line. FIG. 7 schematically shows the center noise 202 that appears on the tomographic image 200 formed by electronic sector scanning. In electronic sector scanning, the distance between beams increases with depth, and the number of interpolated pixels increases with depth. Therefore, it is considered that noise is unnecessarily emphasized.

  Examples of noise generation sources include various devices used during surgery. In particular, it is known that an electric knife produces a large noise. Of course, other devices can also be sources of noise.

JP-A-3-212264 JP-A-6-63044

  In the electronic sector scanning, it is desired to effectively remove or reduce the center noise in order to improve the image quality of the ultrasonic image. Patent Document 2 discloses a technique for canceling electromagnetic noise. However, since noise cancellation is always performed instead of processing focusing on center noise, an unnecessary part is processed depending on circumstances, and the image quality is rather reduced. It is feared that will decline.

  An object of the present invention is to effectively remove or reduce center noise generated in electronic sector scanning. In particular, it is to enable local countermeasures against center noise.

  The present invention relates to an ultrasonic diagnostic apparatus for performing electronic sector scanning of an ultrasonic beam, and setting means for setting a noise canceling partial range extending from both sides in the beam scanning direction from the central beam direction of the electronic sector scanning. Determining means for determining a noise cancellation period when an azimuth or a focus point of the ultrasonic beam is included in the noise cancellation partial range when scanning the ultrasonic beam according to the electronic sector scanning; and the noise cancellation period The present invention relates to an ultrasonic diagnostic apparatus comprising: noise canceling means for performing noise cancellation processing on a received signal obtained by transmitting and receiving ultrasonic waves using a reference signal including electromagnetic noise. .

  According to the above configuration, when the azimuth or focus point of the ultrasonic beam enters the noise canceling partial range in the electronic sector scanning, it is determined that it is within the noise canceling period, and the reference signal is used within that period. Thus, a process for removing electromagnetic noise contained in the received signal is executed. Therefore, noise cancellation processing is not always applied to the entire ultrasound image, but noise cancellation processing is performed only on a specific partial range, so that unnecessary noise cancellation processing is performed on other portions. It is possible to prevent the image quality from deteriorating. The azimuth of the ultrasonic beam that is a candidate for the criterion is a transmission beam azimuth or a reception beam azimuth, and the focus point of the ultrasonic beam that is a candidate for the criterion is a transmission focus point or a reception focus point. A signal representing electromagnetic noise output from the dummy signal line, an electromagnetic noise component in the electrocardiogram signal, or the like may be used as the reference signal. It is desirable to apply a phasing addition process to the received signals after individually performing a noise cancellation process on a plurality of received signals.

  Preferably, the noise canceling partial range is a sector-like two-dimensional region that forms a part of a beam scanning surface formed by electronic sector scanning of the ultrasonic beam. According to this configuration, the control becomes simple. Preferably, the noise cancellation partial range is a two-dimensional region deeper than a predetermined depth, and the width of the noise cancellation partial range in the beam scanning direction is variably set in the depth direction. According to this configuration, it is possible to finely control whether or not noise cancellation is necessary.

  Preferably, the probe includes a probe inserted into a body cavity, and the probe is connected to the array transducer including a plurality of transducer elements for transmitting and receiving ultrasonic waves, and transmits a transmission signal and a reception signal. It includes a plurality of signal lines, a dummy vibrator for observing electromagnetic noise, and a dummy signal line connected to the dummy vibrator, and the reference signal is an output signal of the dummy signal line.

  Preferably, the ultrasonic beam is composed of a transmission beam and a reception beam, and the setting means dynamically transmits transmission delay data for forming a transmission beam at each transmission beam azimuth and the reception beam at each reception beam azimuth. The noise canceling partial range is set on the basis of at least one of the reception delay data to be formed. In this case, the delay amount difference (preferably absolute value) is calculated for each channel between the delay data for the central beam (for example, delay amount zero) and the delay data for each beam, and the sum of the differences is calculated. If the sum is equal to or less than a predetermined value, that is, if it can be regarded as being in the vicinity of the center, it can be determined that the noise canceling partial range. Furthermore, it is desirable that the width of the noise cancellation partial range is dynamically varied in the depth direction.

  As described above, according to the present invention, the center noise generated in the electronic sector scanning can be effectively removed or reduced.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing the main configuration of an ultrasonic diagnostic apparatus according to the present invention. This ultrasonic diagnostic apparatus is an apparatus that has a transesophageal probe and performs ultrasonic diagnosis on the heart by transmitting and receiving ultrasonic waves in the esophagus. Of course, the present invention can be applied to other types of ultrasonic diagnostic apparatuses.

  The probe 10 is the above-mentioned eclipse probe, and a plurality of signal lines 12 and 14 are provided in the insertion tube. A plurality of signal lines 12 shown in the figure are original signal lines for transmitting transmission signals and reception signals, and a signal line 14 is a dummy signal line for transmitting electromagnetic noise. A probe head is provided at the tip of the insertion tube, and a 1D array transducer is provided in the probe head. The 1D array transducer includes a plurality of vibrating elements 16. An ultrasonic beam is formed by the 1D array transducer, and the ultrasonic beam is electronically scanned. In this embodiment, the electronic scanning method is electronic sector scanning.

  A signal line 12 is connected to each of the plurality of vibration elements 16. On the other hand, a capacitor 18 that is electrically equivalent to the vibration element 16 (having similar electrical impedance) is connected to the tip of the dummy signal line 14. The capacitor 18 functions as a sensor that receives electromagnetic noise from an external device, particularly an electric knife, in the probe head. Similarly, the dummy signal line 14 also functions as a sensor that receives electromagnetic noise. In the present embodiment, electromagnetic noise from the outside is observed in the body by the capacitor 18 and the dummy signal line 14 which are dummy vibration elements in this way. It is also possible to perform noise cancellation processing using electromagnetic noise contained in an electrocardiogram signal or the like.

  Each of the plurality of transmitters 22 is a waveform generator, and a transmission signal output therefrom is sent to the corresponding signal line 12 via the amplifier 24 and further via the switch 20. Each amplifier 24 is a transmission amplifier, which performs power amplification. Each switch 20 is a circuit that connects the signal line 12 to the transmitter during transmission and connects the signal line 12 to the receiver during reception. The plurality of transmitters 22 and the plurality of transmission amplifiers 24 constitute a transmission beam former as a whole.

  On the other hand, the configuration of the reception beamformer will be described. The reception signal from each signal line 12 is sent to the corresponding A / D converter 30 via each switch 20 and each differential amplifier 26. . A memory or the like (not shown) is provided at the subsequent stage of each A / D converter 30, and a plurality of received signals read from the memory are added by the adder 32. That is, a reception beam is formed by such a phasing addition process, and a reception signal after phasing addition as beam data is output from the adder 32.

  In the present embodiment, a differential amplifier 26 is provided for each channel, that is, for each signal line 12 as illustrated. The differential amplifier 26 performs a noise canceling process, and removes a noise component included in the received signal by using a cancel signal 106 generated within a specified cancel period, as will be described below. Is. Specifically, the cancel signal 106 is composed of electromagnetic noise itself, and the electromagnetic noise included in the received signal is canceled by the cancel signal 106.

  The noise cancellation control unit 44 generates a gate signal 102 representing a noise cancellation period. In this embodiment, the central area (area where the center noise appears) on the sector-shaped scanning plane is defined as the noise cancellation partial area, and the reference coordinates (beam orientation, focus point) for transmission and reception are the noise cancellation partial area. When entering, the noise cancel period is determined on the time axis.

  The switch unit 33 includes two switch circuits 34 and 36 and an amplifier 42 as shown in the figure. The amplifier 42 is a circuit for performing impedance conversion. The switch circuits 34 and 36 are turned on when the gate signal 102 represents a noise cancellation period (that is, in the case of HI), and connect the signal 104 output from the dummy signal line 14 to the input of the amplifier 42. As a result, the signal 104 is sent as a cancel signal 106 to each differential amplifier 26. On the other hand, when the gate signal 102 represents outside the noise cancellation period, the switch circuits 34 and 36 connect the dummy signal line 14 and the input side of the amplifier 42 to the ground so that noise cancellation processing is not performed. That is, the cancel signal 106 is not substantially output, thereby effectively preventing the problem that the received signal is canceled unnecessarily outside the site where the noise occurs. That is, in this embodiment, in order to solve the problem caused by always performing the noise cancellation processing, a gate signal representing the noise cancellation partial range is generated, and the noise cancellation processing is locally performed only within the noise cancellation period. Has been done. In the noise cancellation partial area, the switch unit 33 may be turned on in advance when each switch 20 selects a transmitter in the previous transmission period.

  FIG. 2 shows a specific example of the noise cancellation control unit 44 shown in FIG. In the configuration example shown in FIG. 2, the noise cancellation control unit 44 includes a noise cancellation table 50 and a table creation unit 52. The table creation unit 52 obtains the contents of the noise cancellation table 50 by calculation, and various conditions including transmission / reception data are input to the input. The table creation unit 52 may be configured by a CPU and an operation program. For example, when the difference in delay amount is calculated for each channel between the delay data for the central transmission beam in the electronic sector scan and the delay data for each transmission beam, and the sum of the differences is less than a predetermined value Alternatively, a beam as a noise cancellation target may be determined. That is, as shown in FIG. 7, since the center noise appears in the central portion of the electronic sector scan, particularly in the lower portion thereof, this portion is specified as a partial range in the beam scanning direction. Of course, the width of the noise cancellation partial range in the beam scanning direction may be dynamically varied in the depth direction. The table data created by the table creation unit 52 is written into the noise cancellation table 50 as described above. In the noise cancellation table 50, the beam address θ is input along with the beam scanning, and the gate signal 102 is output when the θ belongs to the noise cancellation partial range. Incidentally, when the noise cancellation partial range is defined by the beam direction θ and the depth r, the gate signal 102 is output when those input parameters belong to the noise cancellation partial range.

  An example of the noise cancellation table 50 is conceptually shown in FIG. From 1 to n is determined as the direction of the transmission beam, and the noise cancellation partial range 60 is defined as a range from j to k in the beam scanning direction. That is, when the transmission beam direction corresponds to the noise cancellation partial range 60, noise cancellation processing is performed on the received signal. That is, as shown in FIG. 1, the electromagnetic noise included in each received signal is canceled by the cancel signal 106 in each differential amplifier 26. Incidentally, in FIG. 3, reference numerals 62 and 64 represent ranges other than the noise canceling partial range, and the noise canceling process is not executed within the range. As a result, there is an advantage that it is possible to prevent a problem that the image quality is deteriorated due to unnecessary noise cancellation processing in an area where the possibility of the occurrence of center noise is low.

  FIG. 4 shows a timing chart when the noise canceling process is performed. (A) represents a frame trigger signal, and one frame is defined by this signal. (B) shows a line trigger signal generated for each beam direction, that is, a transmission trigger. (C) shows the value of the beam counter, that is, the content of θ. (D) shows a gate signal, and noise cancellation processing is executed when the signal is HI. The HI state represents a generation period of the center noise, in other words, corresponds to a noise canceling partial range.

  Another example is shown in FIGS. 5 and 6. In FIG. 5, the noise cancellation partial range 66 is set at the center of the beam scanning area in the electronic sector scanning, but the area close to the transmission / reception origin is not subject to noise cancellation, and only below the center. A noise canceling partial range 66 is set. The other area 68 is an area where noise cancellation processing is not performed. When such a configuration is adopted, an operation as shown in FIG. 6 is executed. Here, the signals shown in (A) to (D) in FIG. 6 are the same as the signals shown in (A) to (D) in FIG. It should be noted that in the gate signal shown in (D), an effective gate period is set within a certain range in the beam scanning direction and within a certain depth range. According to such a configuration, the noise cancellation partial range can be set only in a region where the probability of occurrence of center noise is high, so that the noise cancellation processing is unnecessarily applied to the transmission origin, that is, a region close to the probe. It is possible to prevent problems due to the above. When the configurations shown in FIGS. 5 and 6 are employed, it is desirable to determine whether or not noise cancellation processing is necessary based on the beam address and depth of the reception focus point in the reception beam. In general, reception dynamic focus is applied at the time of reception, that is, scanning of the reception dynamic focus point is dynamically executed in a deep direction from the transmission / reception origin on the reception beam axis. Accordingly, it is desirable to determine whether noise cancellation processing is necessary.

1 is a block diagram showing a preferred embodiment of an ultrasonic diagnostic apparatus according to the present invention. It is a figure which shows the specific structural example of the noise cancellation control part shown in FIG. It is a figure which shows an example of a noise cancellation partial range. FIG. 4 is a timing chart for explaining the operation of the circuit when the noise cancellation partial range shown in FIG. 3 is applied. It is a figure which shows another noise cancellation partial range. 6 is a timing chart for explaining the operation of the circuit when the noise canceling partial range shown in FIG. 5 is applied. It is a figure for demonstrating center noise.

Explanation of symbols

  10 probes, 12 signal lines, 14 dummy signal lines, 16 vibration elements, 18 dummy vibration elements (capacitors), 20 switches, 22 transmitters, 26 differential amplifiers, 33 switch units, 34, 36 switch circuits, 44 noise cancellation control Department.

Claims (5)

In an ultrasonic diagnostic apparatus that performs electronic sector scanning of an ultrasonic beam,
Setting means for setting a noise canceling partial range extending from both sides in the beam scanning direction from the central beam direction of the electronic sector scanning as a center;
Determining means for determining the noise cancellation period when the azimuth or focus point of the ultrasonic beam in the case of scanning the ultrasonic beam according to the electronic sector scanning is included in the noise cancellation partial range;
Within the noise cancellation period, noise cancellation means for performing noise cancellation processing using a reference signal including electromagnetic noise for a reception signal obtained by transmission and reception of ultrasonic waves,
An ultrasonic diagnostic apparatus comprising: The apparatus of claim 1.
The noise cancellation partial range is a sector-like two-dimensional region that forms part of a beam scanning surface formed by electronic sector scanning of the ultrasonic beam.
An ultrasonic diagnostic apparatus. The apparatus of claim 1.
The noise canceling partial range is a two-dimensional region deeper than a predetermined depth,
The width of the noise cancellation partial range in the beam scanning direction is variably set in the depth direction.
An ultrasonic diagnostic apparatus. The device according to any one of claims 1 to 3,
Including a probe inserted into a body cavity,
The probe includes an array transducer including a plurality of vibration elements that transmit and receive ultrasonic waves;
A plurality of signal lines connected to the array transducer and transmitting transmission signals and reception signals;
A dummy vibrator for observing electromagnetic noise;
A dummy signal line connected to the dummy vibrator;
Including
The ultrasonic diagnostic apparatus, wherein the reference signal is an output signal of the dummy signal line. In the apparatus of any one of Claims 1-4,
The ultrasonic beam is composed of a transmission beam and a reception beam,
The setting means is based on at least one of transmission delay data for forming a transmission beam at each transmission beam azimuth and reception delay data for dynamically forming a reception beam at each reception beam azimuth. And setting the noise cancellation partial range.

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