JP5634817B2 - Ultrasonic diagnostic equipment - Google Patents

Description

  The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to processing for suppressing unnecessary signal components.

  An ultrasonic diagnostic apparatus is an apparatus that displays ultrasonic images by transmitting and receiving ultrasonic waves to and from a living body. In order to improve the image quality of an ultrasonic image, it is desirable to reduce unnecessary signals (unnecessary components) such as side lobes, grating lobes, and noises in the reception beamformer.

  In the receive beamformer, a plurality of element reception signals from a plurality of signal elements are subjected to phasing processing (delay processing) and then added for focusing. After the addition, beam data as an RF signal is obtained. The beam data is used for forming an ultrasonic image. In the case of the reflected wave from the focus point, the phase (time phase) is uniform among the plurality of element reception signals after the delay processing, so that an RF signal having a large amplitude after addition is obtained. On the other hand, in the case of a reflected wave from a place other than the focus point, an RF signal having a low amplitude is observed because the phases do not match among the plurality of element reception signals. In other words, more unnecessary signal components are included. Non-Patent Document 1, Patent Document 1, and the like disclose a technique for reducing unnecessary components by paying attention to the phase uniformity or the degree of variation among a plurality of element reception signals.

  The general method in such a prior art is demonstrated below. A plurality of element reception signals from a plurality of vibration elements are input to a plurality of delay devices for phase adjustment, where delay processing is performed. The plurality of element reception signals after the delay processing are added by a signal adder, and thereby beam data (reception signal after phasing addition processing) as an RF signal is obtained. In addition to the signal processing flow, the sign adder adds a plurality of code (sign-bit) data included in the plurality of element reception signals after the delay process and before the addition process. Here, the value taken by the code data is 1 (positive) or -1 (negative). More specifically, code data corresponding to the number of elements constituting the reception aperture, that is, the number of channels (N) is added, and the weighting coefficient k (or gain) multiplied by the beam data based on the added value S. An adjustment coefficient k) is calculated. In general, k is multiplied by beam data as it is, thereby adjusting the gain. For example, k is calculated as in the following equations (1) and (2). Incidentally, S is an addition value of code data, and P is an index for increasing or decreasing the effect. Since the reception aperture varies depending on the depth of the reception point, N changes according to the depth of the reception point. a is a coefficient generated in the middle, and is a coefficient indicating the degree of variation for a plurality of code data.

k has a value of 0-1. If the phases of all the channels are aligned (in the case of the focus point), S ² = N ² , a becomes 0, and k becomes the maximum value. If noise, the polarity becomes random, so k approaches 0. In this way, the weighting coefficient can be changed between the true signal component and the unnecessary signal component. When unnecessary signal components called side lobes and grating lobes are dominant, the received signal is multiplied by k having a small value, and the unnecessary signal components are suppressed.

International Publication WO2010 / 018282

J. Camacho, et al, "Phase Coherence Imaging", IEEE trans. UFFC, vol. 56, No. 5, 2009.

  However, according to the above prior art, since various conditions such as the transmission focus point are not considered, the received signal is suppressed more than necessary, and an insufficiently bright portion (blackout) tends to occur on the ultrasonic image. There was a problem.

  An object of the present invention is to maintain or improve the image quality of a supersonic image by preventing or reducing excessive suppression of received signals when reducing unnecessary signals.

An apparatus according to the present invention includes a plurality of vibration elements that transmit and receive ultrasonic waves, delay processing means that performs a delay process on a plurality of element reception signals from the plurality of vibration elements, and a plurality of post-delay processes. Based on addition processing means for generating a reception signal by addition processing of element reception signals, a plurality of index data, a transmission focus point, and a reception focus point representing the states of the plurality of element reception signals after the delay processing and before the addition processing Te, characterized in that it comprises a and suppression processing means for executing processing for suppressing unnecessary signal component that is included in the received signal after the addition processing.

  According to the above configuration, the process of suppressing unnecessary signal components in the received signal based on the state of the plurality of element received signals after the delay process and before the addition process, further considering the transmission focus point and the reception focus point. Can be executed. If unnecessary signal component suppression processing is uniformly performed in the depth direction, excessive suppression results such as black spots are likely to occur. However, according to the above configuration, for example, according to the distance from the transmission focus point to the reception focus point. The suppression processing can be executed in consideration of the degree of phase disturbance. Preferably, the index data is code data indicating whether the amplitude value is positive or negative.

  Preferably, the suppression processing means weakens the suppression effect of the unnecessary signal component as the distance from the transmission focus point to the reception focus point increases. When the distance increases, the phase disturbance naturally increases and the suppression effect may increase more than necessary. However, according to the above configuration, such a problem can be avoided or reduced.

  Preferably, the suppression processing means is configured such that the greater the distance from the transmission focus point to the reception focus point, the weaker the suppression effect of the unnecessary signal component, and the greater the depth of the reception focus point. The suppression effect of the unnecessary signal component is weakened as the time increases. According to this configuration, it is possible to execute unnecessary signal component suppression processing that is more realistic.

Preferably, the suppression processing unit calculates a gain coefficient to be multiplied with the received signal. Preferably, the suppression processing unit includes a first coefficient generation unit that generates a first coefficient that changes according to a degree of variation of the plurality of element reception signals based on the plurality of index data, the transmission focus point, and the transmission focus point. Based on the reception focus point , a second coefficient generation unit that generates a second coefficient that changes in response thereto, and calculates a gain coefficient by which the reception signal is multiplied based on the first coefficient and the second coefficient And a gain coefficient calculation unit.

  Preferably, the apparatus includes means for performing one-dimensional smoothing or two-dimensional smoothing of the gain coefficient. According to this configuration, the image quality does not change suddenly.

  According to the present invention, when reducing unnecessary signals, it is possible to prevent or reduce excessive suppression of received signals and maintain or improve the quality of supersonic images.

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 function which determines the coefficient b1 according to the distance from a transmission focus point to a reception focus point. It is a figure which shows the function which determines the coefficient b2 according to the depth of a receiving focus point. It is a figure which shows the function produced | generated by synthesize | combining the function shown in FIG. 2 and the function shown in FIG.

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

  FIG. 1 shows a preferred embodiment of an ultrasonic diagnostic apparatus according to the present invention, and FIG. 1 is a block diagram showing the overall configuration thereof. This ultrasonic diagnostic apparatus is used in the medical field, and is an apparatus that forms an ultrasonic image based on a reception signal obtained by transmitting and receiving ultrasonic waves to and from a living body. In this embodiment, a B-mode tomographic image is formed as an ultrasound image, but a Doppler image or the like may be formed as a matter of course. This ultrasonic diagnostic apparatus has the above-described function for suppressing unnecessary signal components.

  In FIG. 1, an array transducer 10 is arranged in an ultrasonic probe and is composed of a plurality of vibration elements 12. The plurality of vibration elements 12 are arranged in a straight line. Of course, they may be arranged in an arc shape. An ultrasonic beam (transmission beam, reception beam) is formed using the plurality of vibration elements 12 and is electronically scanned. As electronic scanning methods, electronic sector scanning, electronic linear scanning, and the like are known. It is also possible to use a 2D array transducer instead of the 1D array transducer.

  The transmission unit 14 is a transmission beam former. That is, the transmission unit 14 supplies a plurality of transmission signals having a predetermined delay relationship to the plurality of vibration elements 12 during transmission. As a result, a transmission beam is formed. At the time of reception, the reflected wave from each point in the living body is received by the array transducer 10. As a result, a plurality of reception signals (element reception signals) are generated and output to the amplification unit 16. The amplification unit 16, the delay unit 20, and the signal addition unit 28 constitute a reception unit, and the reception unit is a reception beam former.

  The amplification unit 16 includes a plurality of amplifiers 18. A delay unit 20 is provided at the subsequent stage, and the delay unit 20 includes a plurality of delay units 22. Delay processing (phasing processing) is executed by these delay devices 22. The delay time given to each delay unit 22, that is, the delay data is supplied from the control unit 50. An apodization processing unit may be provided after the delay unit 20. A plurality of reception signals (a plurality of element reception signals) after the delay processing are input to the signal addition unit 28. Therefore, the plurality of reception signals are added to form a reception beam electronically. The received signal after the phasing addition processing is output to the detection unit 30. The detection unit 30 is a known circuit that performs detection processing. An input unit 52 is connected to the control unit 50.

  In the present embodiment, an unnecessary signal component suppression unit 32 is provided to suppress unnecessary signal components. Specifically, it includes a code adder 34, a weight table 36, a gain coefficient calculator 38, and a multiplier 40.

  Only a sign bit indicating a positive or negative sign is input to the sign adding unit 34 after each delay process and before the addition process. That is, a plurality of code data are input in parallel there. The code addition unit 34 calculates an addition value S by adding a plurality of code data, and calculates an intermediate coefficient a from the addition value S and the number of data N by the above equation (1) (the above ( 1) Refer to equation). This coefficient a indicates the degree of variation for a plurality of received signals. If the plurality of code data are all aligned with one of 1 (positive) or -1 (negative), the value of the coefficient a is 0. On the other hand, if it is disjoint, the value of the coefficient a approaches 1. In this way, it is possible to evaluate the degree of variation in a plurality of received signals only by referring to a plurality of code data (code bits). Instead of the code data, the received signal itself may be referred as index data. As described above, the code addition unit 34 is a calculation unit for the coefficient a indicating the degree of variation. This calculation is executed in real time and is executed for each reception point. Information indicating the number N of channels is passed from the control unit 50 to the code addition unit 34.

  On the other hand, the weight table 36 is a circuit for obtaining another coefficient b as a weight based on the depth 100 of the transmission focus point and the depth 102 of the reception point (reception dynamic focus point). This will be described in detail below.

  In general, ideal delay processing can be performed near the transmission focus point, so that the phases of the reception channels are uniform, whereas delay is achieved in the short-distance and far-distance areas away from the transmission focus point in the front-rear direction. There is a tendency that the phase between the reception channels is not very uniform even by processing. In other words, the phase disturbance naturally increases as the distance from the transmission focus point increases and decreases regardless of the size of the unnecessary signal component. Under such circumstances, if the coefficient for gain adjustment is simply calculated by evaluating the degree of variation in the code data, an excessive gain limiting action occurs on the near side and the far side from the transmission focus point, and an ultrasonic image is obtained. On the other hand, a problem such as a decrease in luminance, that is, blackout occurs. Therefore, it is desirable to weaken the suppression action as the distance from the transmission focus point increases and decreases. In other words, it is desirable to suppress unnecessary signals strongly at and near the transmission focus point. As is well known, the farther away from the transmission / reception surface, the weaker the received signal and the greater the phase disturbance. Such a tendency is recognized regardless of the size of the unnecessary signal. Therefore, it is desirable to weaken the suppression function of the received signal as the distance from the transmission / reception origin increases. Conversely, it is desirable to increase the suppression function of the reception signal at a short distance where the phase is less likely to be disturbed. The weight table 36 satisfies the above two requirements at the same time.

  FIG. 2 conceptually shows the first action exhibited by the weight table 36, and FIG. 3 conceptually shows the second action exhibited by the weight table 36. In FIG. 2, the horizontal axis indicates the reception point depth 102, and the vertical axis indicates the coefficient (weight) b1. For a certain transmission focus point depth 100, the function 200 is selected. The function 200 generates the maximum weight when the reception point coincides with the transmission focus point, and generates a weight that gradually decreases as the reception point moves away from the transmission focus point in the direction of the short distance area and the long distance area. . When the transmission focus point depth 100 moves to a short distance, for example, the function 202 is used. On the other hand, when the transmission focus point depth 100 moves to a long distance, for example, the function 204 is used. In either case, the weight value is reduced corresponding to the fact that the phase disturbance tends to increase as the distance from the transmission focus point increases. FIG. 3 shows a function 206 for gradually reducing the coefficient (weight) b2 in accordance with the reception point depth 102. This is a characteristic corresponding to the fact that the SNR is lowered and the phase is disturbed as the distance from the transmission / reception origin increases. Reference numeral 208 denotes a function in which the weight is changed from the middle. However, the weight b2 can be determined using such a function.

FIG. 4 shows a weighting function 210 obtained by multiplying or combining the weighting function shown in FIG. 2 and the weighting function shown in FIG. This considers the depth of the reception focus point in addition to the distance from the transmission focus point to the reception focus point. The weighting coefficient b as a correction coefficient is determined using such a weighting function 210.
Returning to FIG. 1, the weighting table 36 stores the weighting function as shown in FIG. 4. When the transmission focus point depth and the reception focus point depth are given from the control unit 50, the combination is supported. The weight b is output (see the following equation (3)). The gain coefficient calculation unit 38 obtains a gain adjustment coefficient k by multiplying the unnecessary signal reduction coefficient a output from the code addition unit 34 and the weight b (the following equation (4)) reference).

  The coefficient k determined as described above is output to the multiplier 40, and is multiplied by the received signal (beam data). As a result, when a lot of unnecessary signal components are included, the gain of the received signal is further reduced, effective suppression of unnecessary signals is performed, and when the content rate of unnecessary signals is small. The gain of the received signal is maintained as much as possible, that is, the true signal is preserved without much suppression. Moreover, as the reception point moves away from the transmission focus point, that is, according to the degree to which the phase is naturally disturbed, the suppression function of the reception signal is weakened, and as the reception point becomes deeper, the suppression function of the reception signal is weakened. Even when the coefficient a is larger than necessary due to the phase disturbance inherent in the sound field, the effect can be reduced. That is, it is possible to prevent excessive signal suppression and prevent image quality degradation such as blackout.

  Incidentally, although multiplication of coefficients is performed in the present embodiment, other methods such as signal subtraction may be used to suppress or reduce unnecessary signal components. The coefficient b may be determined by multiplying a plurality of function values.

  The received signal that has undergone the above processing is sent to the signal processing unit 42. The signal processing unit 42 executes various signal processing such as logarithmic conversion, and the processed signal is sent to the image forming unit 44. The image forming unit 44 is configured by a digital scan converter (DSC) in the present embodiment. Thereby, a B-mode tomographic image is constructed. The image data is sent to the display 48 via the display processing unit 46. In this embodiment, a B-mode image is formed, but a two-dimensional blood flow image or the like may be formed.

  A smoothing process may be performed on a one-dimensional coefficient sequence including a plurality of coefficients k arranged in the depth direction, and the smoothed coefficient k may be given to the multiplier. Alternatively, a two-dimensional smoothing process may be performed on the two-dimensional coefficient sequence aligned in the depth direction and the beam scanning direction, and the smoothed coefficient k may be given to the multiplier. This can alleviate a sharp change in image quality.

  DESCRIPTION OF SYMBOLS 10 Array vibrator | oscillator, 14 transmission part, 32 unnecessary signal component suppression part, 34 code | symbol addition part, 36 weight table, 38 gain coefficient calculating part, 40 multiplier.

Claims (7)

A plurality of vibration elements for transmitting and receiving ultrasonic waves;
Delay processing means for performing delay processing on a plurality of element reception signals from the plurality of vibration elements;
Addition processing means for generating a reception signal by addition processing of a plurality of element reception signals after the delay processing;
A plurality of index data representing the state of the delay processing after and the addition process before the plurality of elements received signal, the distance from the transmission focusing point to a reception focusing point, based on, included in the received signal after the addition processing and suppression processing means for executing processing for suppressing unnecessary signal component that Re,
An ultrasonic diagnostic apparatus comprising: The apparatus of claim 1.
The ultrasonic diagnostic apparatus according to claim 1, wherein the index data is sign data indicating whether an amplitude value is positive or negative. The apparatus according to claim 1 or 2,
The ultrasonic diagnostic apparatus according to claim 1, wherein the suppression processing means reduces the suppression effect of the unnecessary signal component as the distance from the transmission focus point to the reception focus point increases. The apparatus of claim 3.
The suppression processing unit is configured such that the suppression effect of the unnecessary signal component is weakened as the distance from the transmission focus point to the reception focus point is increased, and the depth of the reception focus point is increased as the distance is increased. An ultrasonic diagnostic apparatus characterized in that the suppression effect of unnecessary signal components is weakened. The apparatus of claim 1.
The suppression processing means calculates a gain coefficient to be multiplied with the received signal;
An ultrasonic diagnostic apparatus. A plurality of vibration elements for transmitting and receiving ultrasonic waves;
Delay processing means for performing delay processing on a plurality of element reception signals from the plurality of vibration elements;
Addition processing means for generating a reception signal by addition processing of a plurality of element reception signals after the delay processing;
Based on a plurality of index data, a transmission focus point, and a reception focus point representing a state of a plurality of element reception signals after the delay processing and before the addition processing, unnecessary signal components included in the reception signal after the addition processing are suppressed. Suppression processing means for executing processing to perform,
Including
The suppression processing means includes
A first coefficient generation unit that generates a first coefficient that changes in accordance with a degree of variation of the plurality of element reception signals based on the plurality of index data;
A second coefficient generation unit that generates a second coefficient that changes in accordance with the transmission focus point and the reception focus point ; and
A gain coefficient calculator that calculates a gain coefficient to be multiplied with respect to the received signal based on the first coefficient and the second coefficient;
An ultrasonic diagnostic apparatus comprising: The device according to claim 5 or 6,
Means for performing one-dimensional smoothing or two-dimensional smoothing of the gain factor,
An ultrasonic diagnostic apparatus.

Images