JP4897459B2 - Ultrasonic diagnostic equipment - Google Patents

Description

  The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to an ultrasonic diagnostic apparatus that transmits and receives ultrasonic waves in a plurality of transmission / reception modes.

  In the ultrasonic diagnostic apparatus, as a technique for transmitting and receiving ultrasonic waves in a plurality of transmission / reception modes, a technique of time-division multi-stage focus transmission and simultaneous multi-focus transmission is known. For example, in multistage focus transmission, transmission / reception is performed a plurality of times per transmission / reception direction, and the transmission focus is set at a plurality of different depths. A plurality of reception signals obtained by a plurality of transmissions / receptions are combined to form a reception beam for one transmission / reception direction, and an ultrasound image is formed from the reception beams for a plurality of transmission / reception directions.

  As described above, in multi-stage focus transmission, a reception beam is formed by combining a plurality of reception signals. For example, there is a possibility that a seam appears in a combined portion of the reception signal and the reception signal. Against this background, a technique for weighted addition of a plurality of received signals has been proposed in order to reduce seams on images (see Patent Document 1).

JP 2002-58671 A

  By the weighted addition as described above, the joints on the image are alleviated. However, in the past, it has been necessary to evaluate the degree of relaxation of the joints and the like by humans. In human evaluation, for example, there are problems such as depending on the evaluator's subjectivity and requiring a lot of adjustment time.

  Under such circumstances, the inventor of the present application has conducted research on evaluation relating to the synthesis processing of a plurality of received signals.

  The present invention has been made in the course of its research, and an object thereof is to provide an evaluation technique relating to a synthesis process of a plurality of received signals.

  In order to achieve the above object, an ultrasonic diagnostic apparatus according to a preferred aspect of the present invention includes: a transmission / reception unit that obtains a reception signal for each transmission / reception mode by transmitting / receiving ultrasonic waves in a plurality of transmission / reception modes; A received signal combining unit that obtains a combined received signal for each combined pattern by combining a plurality of received signals corresponding to a plurality of transmission / reception modes based on each of the combined patterns; and a plurality of received signals that correspond to the combined patterns Each of the received composite signals is approximated by an Nth order polynomial to obtain a plurality of polynomials corresponding to the plurality of received composite signals, and based on one or more order coefficients included in each polynomial. And a synthesis pattern evaluation unit that evaluates a plurality of synthesis patterns corresponding to the plurality of polynomials by comparing the plurality of polynomials.

  In the above-described configuration, the plurality of transmission / reception modes include, for example, time-division multistage focal transmission, simultaneous multiple focal transmission, and the like in which ultrasonic waves are transmitted with a plurality of focal points. The reception signal to be combined is, for example, an RF signal, a signal after detection processing, a signal after logarithmic compression processing, or the like. According to the above configuration, it is possible to evaluate a composite pattern by comparing a plurality of polynomials. Therefore, for example, the synthesis process can be quantitatively evaluated based on comparison of a plurality of polynomials.

  In a desirable aspect, the transmission / reception unit acquires a reception signal for each focus of the multi-stage focus transmission method by transmitting and receiving ultrasonic waves by a multi-stage focus transmission method, and the reception signal synthesizing unit applies each combination pattern to each synthesis pattern. Based on the corresponding weight coefficient data, a plurality of reception signals corresponding to a plurality of focal points of the multi-stage focal point transmission method are combined to obtain a plurality of combined reception signals corresponding to the plurality of weight coefficient data, and the polynomial The computing unit is characterized by approximating each of a plurality of combined reception signals corresponding to a plurality of weight coefficient data with an Nth order polynomial.

  In a preferred aspect, the composite pattern evaluation unit compares a plurality of polynomials based on a second-order or higher-order coefficient included in each polynomial. In a desirable mode, the synthetic pattern evaluation unit calculates an evaluation value corresponding to the coefficient size of each polynomial based on a coefficient of the second or higher order included in each polynomial, and based on the evaluation value of each polynomial An optimum synthesis pattern is selected by comparing the magnitudes of coefficients of a plurality of polynomials.

  According to the present invention, an evaluation technique related to a combination process of a plurality of received signals is provided. For example, a preferred aspect of the present invention allows quantitative evaluation of a synthesis process based on a comparison of a plurality of polynomials.

  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 functional block diagram showing the overall configuration thereof.

  The probe 10 is an ultrasonic probe that transmits and receives ultrasonic waves, and includes a plurality of vibration elements. For example, the plurality of vibration elements are arranged in a line and electronically controlled to transmit and receive ultrasonic waves in a two-dimensional plane. In addition, ultrasonic waves may be transmitted and received three-dimensionally by arranging a plurality of vibration elements in a two-dimensional manner in a lattice form and being electronically controlled.

  The transmission beam former 14 outputs a transmission signal corresponding to each of the plurality of vibration elements included in the probe 10. The transmission beamformer 14 applies a delay process or the like corresponding to the vibration element to the transmission signal of each vibration element. The transmission signal output from the transmission beam former 14 is supplied to each vibration element of the probe 10 via the transmitter 12. In this way, each vibration element is driven in accordance with the transmission signal formed by the transmission beam former 14, and an ultrasonic transmission beam is formed, and the transmission beam is subjected to scanning control.

  The reception beam former 18 forms a reception beam based on reception signals of a plurality of vibration elements included in the probe 10. Reception signals output from the plurality of vibration elements of the probe 10 are supplied to the reception beamformer 18 via the receiver 16. The reception beamformer 18 applies a delay process or the like corresponding to the vibration element to the reception signal of each vibration element, and adds the reception signals obtained from the plurality of vibration elements. That is, the reception beamformer 18 performs phasing addition processing on reception signals output from a plurality of vibration elements. The reception signal after the phasing addition output from the reception beam former 18 is supplied to the reception signal synthesis unit 20.

  In the present embodiment, transmission / reception of ultrasonic waves is performed by a multi-stage focus transmission method. That is, the transmission beamformer 14 transmits ultrasonic waves multiple times with different transmission focal points in each beam transmission direction. For example, transmission is performed using a short-distance focus with a focus set at a position relatively close to the probe 10 and transmission with a long-range focus set with a focus set at a position relatively far from the probe 10. Of course, not only the two focal points of the short distance and the long distance but also three or more focal points may be set.

  In the multistage focus transmission method, the reception beamformer 18 forms a plurality of reception signals corresponding to each of a plurality of focal points for each beam transmission direction. For example, a reception signal corresponding to transmission by a short-distance focus and a reception signal corresponding to transmission by a long-distance focus are formed. Thus, for each beam transmission direction, two reception signals corresponding to the short-distance focus and the long-distance focus are formed, and these two reception signals are combined by the reception signal combining unit 20, whereby each beam transmission direction Received beam data corresponding to is formed.

  FIG. 2 is a diagram illustrating two received signals after logarithm compression corresponding to the short-distance focus and the long-distance focus. In FIG. 2, the horizontal axis indicates the depth in the beam direction, and the vertical axis indicates the magnitude (luminance) of the received signal. The near-focus received signal has a peak luminance near the near-focus position (depth), while the far-focus received signal is near the far-focus position (depth). The brightness is at its peak. In this way, the near-focus received signal and the far-focus received signal have different peak luminance positions and profile curves. Therefore, when combining these two received signals, a weighting coefficient corresponding to each received signal is used.

  FIG. 3 is a diagram for explaining weighting coefficients for two received signals. In FIG. 3, the horizontal axis indicates the depth in the beam direction, and the vertical axis indicates the magnitude of the coefficient. The weighting coefficient for the short distance focus has a coefficient value of 1 from the depth 0 to the position of the short distance focus, for example. When the position of the near focal point is exceeded, the weighting coefficient for the short distance focal point decreases linearly as the depth increases, and the coefficient value becomes zero.

  On the other hand, the weighting coefficient for the long-distance focus has a coefficient value of 0 to the position of the short-distance focal point, for example, and increases linearly as the depth increases from the position of the short-distance focal point. The coefficient value is 1 at the position of the focal point. Thereafter, the weighting coefficient for the long distance focus maintains the coefficient value 1 even if the depth increases.

  FIG. 4 is a diagram illustrating a combined received signal obtained by combining two received signals. In FIG. 4, the horizontal axis indicates the depth in the beam direction, and the vertical axis indicates the magnitude (luminance) of the received signal. The synthesized received signal shown in FIG. 4 is obtained by synthesizing two received signals corresponding to the short-distance focus and the far-distance focus shown in FIG. 2 using the weighting coefficients shown in FIG.

  As shown in FIG. 4, as a result of using the weighting coefficient, two reception signals corresponding to the short distance focus and the long distance focus are connected relatively smoothly to form a combined reception signal. However, since the luminance value of the synthesized received signal varies finely when viewed microscopically, it is difficult to quantitatively evaluate the smoothness of the synthesized received signal itself. Therefore, in this embodiment, the smoothness of the combined received signal is evaluated using an Nth order polynomial.

  FIG. 5 is a diagram showing an approximate curve by a polynomial of the combined received signal. FIG. 5 is a graph in which a polynomial approximation curve of the combined received signal is superimposed on FIG. 4 showing the combined received signal.

  For example, if the Nth order polynomial is a fifth order polynomial, it is expressed as follows.

  Considering the mathematical meaning of this approximate expression, if this curve is smooth, the number of inflection points of the polynomial is reduced. For example, as the coefficient value of the third or higher order is closer to 0, the degree of undulation of the approximate curve becomes smaller and the curve becomes smoother. Furthermore, if the secondary coefficient is small, the degree of unevenness of the approximate curve becomes gentle. That is, it is considered that the magnitude of the second-order or higher-order coefficients (a, b, c, d) of the polynomial shown in Equation 1 is one of the evaluation indexes representing the smoothness of the curve.

  FIG. 6 shows a polynomial approximation curve of the combined received signal when the weighting coefficient is changed in five stages (A to E). FIG. 7 is a diagram showing the magnitudes of the second-order coefficients of the polynomial approximation curve of the five stages (A to E) in FIG. FIG. 7 shows that the quadratic coefficient of the approximate curve C is the smallest. Then, comparing the approximate curves of the five stages (A to E) in FIG. 6, it can be seen that the degree of unevenness of the approximate curve C is relatively gentle.

  In this embodiment, when a synthesis parameter such as a weighting coefficient of a plurality of received signals is changed, a polynomial approximation coefficient of the synthesized received signal is calculated accordingly, and the smoothness of the synthesis process is calculated based on the coefficient. evaluate.

  FIG. 8 is a flowchart for explaining a synthesis processing evaluation method according to this embodiment. First, the parameter α [i] of the synthesis process is changed (S801), and a synthesized reception signal (luminance profile) is obtained for each parameter (S802). In other words, a composite reception signal is calculated in the reception signal synthesis unit (reference numeral 20 in FIG. 1) for each synthesis parameter by changing a synthesis parameter such as a weighting coefficient of the reception signal.

  Next, each composite received signal (luminance profile) is approximated by an Nth order polynomial (S803). That is, an Nth order polynomial is calculated for each combined received signal by the polynomial calculation unit (reference numeral 22 in FIG. 1). In this way, the coefficients of the order of 2 to 5 are calculated for each polynomial approximation.

FIG. 9 is a diagram showing coefficients of respective orders of the polynomial obtained for each synthesis parameter. FIG. 9 shows coefficients a, b, c, and d of the order up to the second to fifth orders of the polynomial corresponding to each synthesis parameter α [i] (i = 0 to M−1). Further, FIG. 9 shows maximum values a _Max , b _Max , c _Max , and d _Max of the coefficients for each order.

  Returning to FIG. 8, when the coefficients of the order of 2 to 5 are calculated for each polynomial approximation, the synthesis process evaluation unit (reference numeral 24 in FIG. 1) orders 2 to 5 for each polynomial approximation. Are normalized within the variable range of the parameters (S804). Then, for each parameter, the sum of the order coefficients up to the second to fifth orders after normalization is calculated (S805). In this way, the synthesis processing evaluation unit (reference numeral 24 in FIG. 1) compares a plurality of parameters based on the sum calculated for each parameter, and selects the parameter with the smallest sum.

FIG. 10 is a diagram for explaining normalization and summation of coefficients. FIG. 10 shows coefficients of orders up to the second to fifth orders of the polynomial corresponding to each synthesis parameter α [i] (i = 0 to M−1). In FIG. 10, each coefficient is normalized by the maximum value (a _Max , b _Max , c _Max , d _Max ) of the coefficient.

  Furthermore, FIG. 10 shows the sum β [i] (i = 0 to M−1) of coefficients after normalization from the fifth order to the second order for each synthesis parameter α [i]. In the present embodiment, the smallest β [i] is selected from the plurality of sums β [i], and a synthesis parameter (for example, a weighting factor of the synthesis process) corresponding to the β [i] is determined as the optimum parameter. The

  Thus, in FIG. 1, when the optimum synthesis parameter is selected by the synthesis processing evaluation unit 24, the selection result is supplied to the received signal synthesis unit 20. The reception signal combining unit 20 forms reception beam data by executing a combination process of two reception signals corresponding to the short-distance focus and the long-distance focus for each beam direction according to the optimal combination parameter.

  Then, the ultrasonic image forming unit 26 forms an ultrasonic image based on the received beam data for a plurality of beam directions. For example, a two-dimensional B-mode image or the like is formed, and the formed image is displayed on the display 28.

  The preferred embodiment of the present invention has been described above. According to the above-described embodiment, it is possible to quantitatively evaluate the parameters of the synthesis process based on the sum of the normalized coefficients. In addition, embodiment mentioned above and its effect are only illustrations in all the points, and do not limit the scope of the present invention. The present invention includes various modifications without departing from the essence thereof.

1 is a functional block diagram showing an overall configuration of an ultrasonic diagnostic apparatus according to the present invention. It is a figure which shows two received signals corresponding to a short distance focus and a long distance focus. It is a figure for demonstrating the weighting coefficient with respect to two received signals. It is a figure which shows the synthetic | combination reception signal which synthesize | combined two reception signals. It is a figure which shows the approximated curve by the polynomial of a synthetic | combination received signal. It is a figure which shows the approximated curve of the synthetic | combination received signal at the time of changing a weighting coefficient. It is a figure which shows the magnitude | size of the secondary coefficient of a polynomial approximated curve. It is a figure for demonstrating the evaluation method of the synthetic | combination process in this embodiment. It is a figure which shows the coefficient of each degree of the polynomial obtained for every synthetic | combination parameter. It is a figure for demonstrating the normalization and sum total of a coefficient.

Explanation of symbols

  10 probe, 14 transmission beamformer, 18 reception beamformer, 20 reception signal synthesis unit, 22 polynomial arithmetic unit, 24 synthesis processing evaluation unit.

Claims (4)

A transmission / reception unit that obtains a reception signal for each transmission / reception mode by transmitting / receiving ultrasonic waves in a plurality of transmission / reception modes;
A received signal combining unit that obtains a combined received signal for each combined pattern by combining a plurality of received signals corresponding to a plurality of transmission / reception modes based on each of the combined patterns;
A polynomial arithmetic unit that obtains a plurality of polynomials corresponding to the plurality of combined received signals by approximating each of the plurality of combined received signals corresponding to the plurality of combined patterns with a second-order or higher order polynomial;
A composite pattern evaluation unit that evaluates a plurality of composite patterns corresponding to the plurality of polynomials by comparing the plurality of polynomials based on one or a plurality of degree coefficients included in each polynomial;
Having
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
The transmission / reception unit obtains a reception signal for each focus of the multistage focus transmission method by transmitting and receiving ultrasonic waves by the multistage focus transmission method,
The reception signal combining unit supports a plurality of weight coefficient data by combining a plurality of reception signals corresponding to a plurality of focal points of the multistage focus transmission method based on the weight coefficient data corresponding to each combination pattern. Obtain multiple composite received signals,
The polynomial calculation unit approximates each of a plurality of combined reception signals corresponding to a plurality of weight coefficient data with a second-order or higher-order polynomial.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 2,
The composite pattern evaluation unit compares a plurality of polynomials based on a second-order or higher-order coefficient included in each polynomial.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 3.
The composite pattern evaluation unit calculates an evaluation value corresponding to the coefficient size of each polynomial based on the coefficients of the second or higher order included in each polynomial, and the plurality of polynomials based on the evaluation value of each polynomial. Select the optimal composite pattern by comparing the magnitudes of the coefficients.
An ultrasonic diagnostic apparatus.

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