JP2018175478A - Ultrasonic diagnosis device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate and display a tomogram image of high resolution without degrading a frame rate.SOLUTION: A transmission-side focus position is changed per frames according to a focus position set including the ordered and predefined plurality of transmission-side focus position of an ultrasonic beam to be transmitted into a biological body, and the change of the transmission-side focus position is cycled per said predefined plurality of focus positions so as to repeat scanning of the ultrasonic beam into the subject. In chronological frame images generated based on received signal, a frame-synthesis of the chronologically-aligned plurality of frame images is repeated. Accordingly, a tomogram image including the frame images after the frame-synthesis is displayed.SELECTED DRAWING: Figure 4

Description

  The present invention receives a reflected ultrasonic wave while scanning the inside of an object with an ultrasonic beam to obtain a received signal, generates a plurality of time-sequential frame images based on the received signal, and generates an object derived from the frame image. The present invention relates to an ultrasonic diagnostic apparatus that displays a tomogram (so-called B mode image) in a sample.

  The above ultrasonic diagnostic apparatus is known (see, for example, Patent Document 1), and is widely used in hospitals and the like.

  One important theme in this ultrasonic diagnostic apparatus is how to generate and display a high-resolution tomogram.

  As a technique for generating and displaying high-resolution tomograms, a technique called dynamic focusing is used for the receiving side when transmitting an ultrasound beam into a subject and receiving reflected ultrasound. Be done. This dynamic focusing is performed by advancing to a shallow position in the subject, reflecting at the shallow position, returning ultrasound, and advancing to a deep position in the subject and reflecting at the deep position and returning ultrasound. It is a technology to change the receiving side focal point position in the time direction in the depth direction by making use of the time difference between them.

  However, on the transmitting side, this dynamic focusing technique can not be adopted, and an ultrasonic beam having the transmitting side focus at one predetermined depth position is to be transmitted. Therefore, even if a tomogram with relatively high resolution is obtained for a depth region near the transmission side focal point of the tomogram, a relatively low resolution tomogram is obtained for a depth region away from the transmission side focal point . For this reason, in order to obtain a tomogram to be examined over a wide region in the depth direction, it has been practiced to broaden the focus on the transmission side without narrowing the focus.

  In order to obtain a uniform beam in the depth direction with high resolution also on the transmitting side, for example, a tomographic image obtained by transmitting an ultrasonic beam with the transmitting focal position set at a shallow position, and the transmitting focal position A plurality of tomograms obtained by transmitting the ultrasonic beam by setting the focal point on the transmission side to each of a plurality of positions in the depth direction, such as a tomographic image obtained by transmitting an ultrasonic beam set at a deep position; It is called multi-stage focusing that obtains one high-resolution tomogram over a wide range in the depth direction by cutting out and connecting areas near each of the high-resolution transmission-side focal points of these multiple tomograms. Technology is known. However, if this technique is adopted to synthesize one high resolution tomographic image from, for example, n tomographic images, another problem arises that the frame rate is reduced to 1 / n. The frame rate is the number of tomograms per unit time, and if the frame rate is low, tomograms with smooth motion can not be displayed.

JP, 2014-144113, A

  An object of the present invention is to provide an ultrasonic diagnostic apparatus capable of generating and displaying a high resolution tomogram without lowering the frame rate.

An ultrasonic diagnostic apparatus of the present invention which achieves the above object is
While scanning the inside of the subject with an ultrasound beam, the reflected ultrasound is received to obtain a received signal, and a time-sequential frame image is generated based on the received signal, and a tomographic image in the subject derived from the frame image An ultrasonic diagnostic apparatus for displaying an image,
The transmitting focal position is changed for each frame according to a set of focal positions consisting of a plurality of predetermined, predetermined transmitting focal positions of the ultrasound beam to be transmitted into the object, and the transmission focal position is changed A scan control unit that repeats scanning of the inside of the subject with the ultrasonic beam while circulating each of the plurality.
A frame combining unit that sequentially repeats combining processing of the plurality of frame images arranged in time series with respect to time-series frame images generated based on the received signal;
And a display unit for displaying a tomogram composed of a frame image after the combining process in the frame combining unit.

  According to the ultrasonic diagnostic apparatus of the present invention, high-resolution tomograms can be generated and displayed without lowering the frame rate because the synthesis processing of a plurality of tomograms having different transmission-side focal positions is sequentially repeated. it can.

  Here, in the ultrasonic diagnostic apparatus according to the present invention, the frame synthesizing unit is a far-field area apart from the transmission-side focal point for each frame image in the near-field area of the transmission-side focal point for each frame image. It is preferable to perform a weighting process using a weighting function whose weight is increased compared to.

  In performing the frame synthesis process, the resolution of the tomogram to be generated is further enhanced by performing the weighting process using the weighted function on the region near the transmission-side focal position.

  Further, in the ultrasonic diagnostic apparatus according to the present invention, it is also preferable to further include a setting unit that adjustably sets a plurality of transmission-side focus positions constituting the focus position set.

  By setting the transmitting focus position to be adjustable, the transmitting focus can be further enhanced to further improve the resolution of the specific depth region when the region to be examined on the tomographic image is in a partial depth region. It becomes possible to set up according to the subject of the examination every time, such as adjusting the position.

  Furthermore, in the ultrasonic diagnostic apparatus according to the present invention, the scan control unit performs control to change the scan deflection maximum angle for each frame, and sets the transmission-side focal position to a deeper position according to the focal position set. It is preferable to set the scanning deflection maximum angle as large as the number of frames.

  When the transmitting focal position is at a deep position in the subject, artifacts are suppressed even if the deflection angle is large, as compared with the case where the transmitting focal position is at a shallow position.

  Furthermore, in the ultrasonic diagnostic apparatus according to the present invention, the scan control unit changes the transmission focal position for each frame according to the focal position set and circulates the transmission focal position changes for each of the plurality. It is also a preferred embodiment to repeat the scanning within the subject with ultrasonic waves of higher frequency as the transmission side focal position is shallower.

  The higher the frequency of the ultrasound, the higher the resolution of the tomogram. However, high-frequency ultrasound is highly attenuated and is not suitable for examination in deep regions. Therefore, by making the frequency of the ultrasonic wave interlock with the transmission-side focal position and adopting a higher frequency ultrasonic wave as the transmission-side focal position is shallower, it is possible to further improve the resolution in a particularly shallow region of the tomographic image.

  According to the present invention as described above, an ultrasonic diagnostic apparatus capable of generating and displaying a high resolution tomogram without lowering the frame rate is realized.

It is a block diagram showing the composition of the ultrasonic diagnostic equipment as one embodiment of the present invention. It is a figure showing the 1st example of a focal point set. It is an image figure of a time-sequential several frame showing a tomogram. It is explanatory drawing of the frame compositing process in a frame compositing part. It is a figure showing the definition of the weighting function for each transmitting side focal position. It is a figure showing the 2nd example of a focal point set. It is an image figure of a time-sequential several frame showing a tomogram. It is explanatory drawing of the frame compositing process in a frame compositing part. It is the figure which accumulated and showed seven frames used for one frame synthetic | combination processing.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 1 is a block diagram showing the configuration of an ultrasonic diagnostic apparatus according to an embodiment of the present invention.

  The ultrasound diagnostic device 100 shown in FIG. 1 is provided with an ultrasound probe 1. The ultrasonic probe 1 is detachably replaced, and an ultrasonic probe suitable for the diagnostic region, diagnostic content, etc. of the living body 30 is used. In the ultrasonic probe 1, transducers (not shown) such as piezoelectric ceramics are arranged at the tip of the side that is applied to the body surface of the living body 30. Further, the transmitter unit 2 and the receiver unit 3 are connected to the ultrasound probe 1.

  The transmitter 2 includes a pulse generator that generates a rate pulse giving a repetition cycle of transmission (for example, 4 KHz). The transmission unit 2 has, for example, 64 channels of pulse drivers and delay circuits. The pulse driver generates an oscillating pulse of a cycle determined by the set transmission frequency (for example, 2.5 MHz) at the timing of the rate pulse, and applies it to the transducer of the ultrasonic probe 1. The delay circuit focuses the ultrasonic beam and gives a predetermined delay to the pulse generation timing for each channel in order to provide directivity. As a result, an ultrasonic beam having directivity is transmitted in a pulsed manner into the living body 30. In this manner, ultrasound beams extending along the scanning line, for example, each of 256 scanning lines extending into the living body 30 are sequentially transmitted from the ultrasound probe 1 at a rate pulse period, and scanning for one frame is completed. Do.

  On the other hand, the ultrasonic wave reflected by the discontinuous surface of the acoustic impedance in the living body 30 is received for each channel by the receiver 3 via the ultrasonic probe 1 and converted into a reception signal. The receiving unit 3 includes a preamplifier, an A / D conversion circuit, a delay circuit, an addition circuit, a quadrature detection circuit, and an amplitude calculation circuit. The received signal is amplified by the preamplifier, converted into a digital received signal by the A / D conversion circuit, given a predetermined delay for each channel by the delay circuit, and added by the addition circuit. In the quadrature detection circuit, the output signal from the addition circuit is converted into an in-phase signal (I signal, I: In-phase) and a quadrature signal (Q signal, Q: Quadrature-phase) in the baseband band, and an amplitude calculation circuit Calculate the amplitude with. Thereby, the reflected ultrasound from the direction in which the ultrasound beam is transmitted is sequentially received for each scanning line 1a. The received signal output from the receiving unit 3 is logarithmically compressed by the logarithmic compression unit 4, subjected to B mode signal processing by the B mode signal processing unit 5, and temporarily stored in the frame memory 6 sequentially for each frame. Then, the reception signals for a predetermined number of frames stored in the frame memory 6 are read out, and the frame synthesis unit 7 performs frame synthesis processing. The frame combining process in the frame combining unit 7 will be described later.

  The received signal after the frame synthesis process is input to the frame correlation unit 8. In the frame correlation unit 8, first-order IIR filtering is performed between the current frame signal input and the frame signal input immediately before that. However, depending on the case, it is also possible to omit the processing in the frame correlation unit 8. The output signal from the frame correlation unit 8 is stored in the cine memory 9.

  The received signal stored in the cine memory 9 is further input to the digital scan converter (DSC) 10. In the DSC 10, a set of one frame worth of received signals for each scanning line 1a is converted to a signal suitable for display on the display screen of the display unit 11 by coordinate conversion processing and linear interpolation processing. A signal suitable for display on the display screen of the display unit 11 generated by signal conversion by the DSC 10 is input to the display unit 11, and the signal sent from the DSC 10 is displayed on the display screen of the display unit 11. The tomogram based on it is displayed.

  Next, the frame combining unit 7, the frame combining setting unit 71, and the focus position setting unit 21 will be described.

  The frame synthesis setting unit 71 sets the number of frames to be subjected to one frame synthesis process. The focal position setting unit 21 sets a focal position set including the same number of transmission focal positions as the number of frames in one frame synthesis processing set by the frame synthesis setting unit 71.

  FIG. 2 is a diagram showing a first example of the focal position set.

  Here, it is assumed that the number of frames on which frame composition processing is performed once is set to "3" in the frame composition setting unit 71. In that case, the focal position set 22 is composed of three transmitting focal positions as shown in FIG. Here, the transmission-side focal positions d1, d2 and d3 are d1 <d2 <d3, and the transmission-side focal position d1 is at the shallowest position in the living body 30 among these three, and the transmission-side focal position d2 Is at the middle depth position, and the transmitting focal position d3 is at the deepest position among these three. These three transmission focus positions d1, d2 and d3 are preset to values suitable for examining the entire area from the shallow area to the deep area in the tomogram generated this time, but the depth is determined by the user. It can move in the longitudinal direction.

  FIG. 3 is an image diagram of a plurality of chronological frames representing a tomogram.

  Here, it is assumed that an ultrasonic probe for linear scanning is mounted as the ultrasonic probe 1, and control of linear scanning is performed by the scanning control unit 31. Here, the linear scan refers to a scanning method in which the scanning lines 1a (the traveling directions of the ultrasonic beams) extend in parallel with each other and shift in the lateral direction.

  FIGS. 3A to 3F show reception signals of one frame each generated in time series. Here, the reception signals for one frame shown in FIGS. 3A to 3F are referred to as frame a to frame f, respectively.

  When the frame a is generated, the delay circuit of the transmission unit 2 adjusts the pulse generation timing for each channel so as to be the first transmission-side focal position d1 of the focal position set 22 shown in FIG. Similarly, when the frame b is generated, the delay circuit of the transmission unit 2 adjusts the transmission position of the focal position set 22 so as to be the second transmission side focal position d2, and when the frame c is generated, the transmission unit In the second delay circuit, adjustment is made to be the third transmission focal position d3 of the focal position set 22. Further, at the time of generation of the next frame d, the delay circuit of the transmission unit 2 returns to the top of the focal position set 22 and adjusts so as to be the transmission focal position d1. That is, here, the delay pattern is changed for each frame so that the transmission-side focal position cyclically becomes d1, d2, d3. Thus, generation of not only six frames of frame a to frame f shown in FIG. 3 but also a large number of frames is repeated. The frames a, b, c,... Thus generated are sequentially stored in the frame memory 6. The frame memory 6 has a memory capacity to such an extent that there is no hindrance to the execution of the frame composition process to be described next. However, when the frame memory 6 is full, the frame memory 6 is overwritten in order from the previously stored frame.

  FIG. 4 is an explanatory diagram of a frame combining process in the frame combining unit.

  In the example shown here, the frame combining setting unit 71 sets the number of frames in one combining process to “3”. Therefore, in the frame combining unit 7, first, frame combining processing is performed on the three frames a to c shown in FIG. That is, here, the signal values of corresponding points of three frames a to c are averaged, and the averaged signal values are associated with the points.

  However, weighted average processing is employed in the frame synthesis processing here.

  FIG. 5 is a diagram showing the definition of the weighting function for each transmission-side focal position.

  For the frame a, the neighborhood area D1 of the transmission-side focal position d1 is weighted more than the other areas D2 and D3 far from the transmission-side focal position d1. Here, as an example, the signal value of each point (i) in the region D1 is tripled. On the other hand, for each point (i) in the other regions D2 and D3, the weighting value DW1 (i) in the depth direction is linearly reduced from three times the signal value of that point. Similarly, with regard to the frame b, weighting is performed on the vicinity area D2 of the transmission-side focal position d2 with an increased weight compared to other areas D1 and D3 far from the transmission-side focal position d2. Here, as an example, the signal value of each point (i) in the region D2 is tripled. On the other hand, the weight of each point (i) in the other areas D1 and D3 is linearly reduced from 3 to be a function DW2 (i) in the depth direction. Further, with regard to the frame c, weighting is performed to increase the weight in the vicinity area D3 of the transmission-side focal position d3 compared to other areas D1 and D2 far from the transmission-side focal position d3. Here, as an example, the signal value of each point (i) in the region D3 is tripled. On the other hand, the weight of each point (i) in the other areas D1 and D2 is linearly reduced from 3 to be a function DW3 (i) in the depth direction.

Specifically, when the signal values of the corresponding points (i) of the three frames a to c are Sa (i), Sb (i) and Sc (i),
Average value S (i) = (Sa (i) × DW1 (i) + Sb (i) × DW2 (i) + Sc (i) × DW3 (i)) / (DW1 (i) + DW2 (i) + DW3 (i) )
Thus, the average value S (i) is calculated and associated with the point (i).

  When the frame composition process of the three frames a to c is completed, next, the frame composition process of the three frames b to d shifted by one is performed. The weighting for frames b and c is as described above, and the weighting for frame d is the same as the weighting for frame a. Further, next, frame composition processing of three frames c to e further shifted is executed. The weighting for frames c and d is as described above, and the weighting for frame e is the same as the weighting for frame b. Also, the weighting for frame f is the same as the weighting for frame c.

  In this way, frame composition processing for three frames at a time is sequentially performed. A frame generated by this frame synthesis processing is a high resolution tomogram over the entire tomogram, focusing on the three transmission side focal positions of d1, d2 and d3.

  The processing after passing through the frame combining unit 7 is as described above.

  FIG. 6 is a diagram showing a second example of a focal position set including a plurality of transmission focal positions.

  Here, it is assumed that the number of frames to be subjected to one averaging process is set to “7” by the frame combining setting unit 71. In this case, as shown in FIG. 6, the focal position set 23 includes seven transmitting focal positions that allow overlapping of the same transmitting focal position. As in the case of FIG. 2, here too, the transmission side focal positions d1, d2 and d3 are d1 <d2 <d3, and the transmission side focal position d1 is at the shallowest position in the living body 30 among these three. The transmission focal position d2 is at a medium depth position, and the transmission focal position d3 is at the deepest position among these three. These three transmission focus positions d1, d2 and d3 are preset to values suitable for examining the entire area of the tomogram this time, but can be moved in the depth direction by the user. Also, the number of transmitting focal positions is not limited to three, and it is possible to set different transmitting focal positions by the same number as the number of frames to be subjected to one averaging process at the maximum (here, “7”). .

  Here, in the focus position set 23 shown in FIG. 6, d1 appears twice, d2 three times, and d3 twice. That is, the example shown here is set to place a slight emphasis on the middle depth position.

  Further, in the focus position set 23 shown in FIG. 6, a set of the frequencies f1, f2 and f3 of ultrasonic waves is also recorded. The frequencies f1, f2 and f3 are f1> f2> f3. That is, among the three transmission-side focal positions d1, d2 and d3 set in the focal position set 23, the transmission-side focal position d1 at the shallowest position in the living body 30 has three frequencies f1, f2 and f3. The highest frequency f1 of the two is associated. In addition, the medium frequency f2 is associated with the transmission focal position d2 at the medium depth position, and the lowest frequency f3 is correlated with the transmission focal position d3 at the deepest position. There is. This is because the higher the frequency, the higher the resolution, but the higher the frequency, the attenuation is severe and the penetration is lowered, and it is difficult to generate a tomogram in a deep region. These three frequencies f1, f2 and f3 are preset to values appropriate for examining the entire area from the shallow area to the deep area in the tomographic image, but can be adjusted by the user. Furthermore, although three frequencies f1, f2 and f3 are adopted here, the same frequency may be adopted in all the frames as in the first example (see FIG. 2) described above, or two different ones may be adopted. Frequency may be adopted.

  Further, in the focus position set 23 shown in FIG. 6, the maximum scanning deflection angle for each frame is also recorded. The scanning deflection angle refers to an angle at which the ultrasonic beam is obliquely generated in the living body 30, as shown in FIG. For example, in the frame of FIG. 7 (a), the maximum scan deflection angle is 15 °.

  Here, three frequencies f1, f2, and f3 are associated with the three transmission-side focal positions d1, d2, and d3 set in the focal position set 23 shown in FIG. 6, respectively, and these three frequencies f1 , F2 and f3 are associated with a small scanning deflection angle of 5 °. Further, the medium frequency f2 is associated with the medium scanning deflection angle 10 °, and the lowest frequency f3 is associated with the largest scanning deflection angle 15 °. However, a medium frequency f2 is associated with a frame with a scanning deflection angle of 0 °.

  As described above, although high frequency tomograms with high resolution can be obtained as described above, high frequency produces a large artifact when adopting a large scanning deflection angle as compared with low frequency. Therefore, when the frequency is high, a small scanning deflection angle is adopted. On the other hand, when the frequency is low, the resolution is reduced compared to when the frequency is high, but the penetration is good and suitable for generating a tomogram in a deep region, and the scanning deflection angle is compared with when the frequency is high. Is large, but the artifact is small.

  The scan deflection angle for each of these frames can also be changed by the user.

  FIG. 7 is an image diagram of a plurality of chronological frames representing a tomogram.

  Here, it is assumed that the control to realize the frame composition method of spatial compound in which the scan deflection angle of each frame is different is performed by the scan control unit 31.

  Here, the space compounding method refers to a technology of sequentially synthesizing frames sequentially arranged in time series while cyclically switching the scanning deflection angle of the ultrasonic beam between the frames. This space compounding method is used for examination of tissue hidden behind the hard tissue such as bone and not appearing on a tomogram from right above. Here, an example will be described in which this space compounding method is combined with the feature of the present embodiment in which the transmission-side focal position is set to a plurality of places sequentially.

  FIGS. 7A to 7N show reception signals of one frame each generated in time series. Here, the reception signals of one frame each shown in FIGS. 7A to 7N are referred to as frame a to frame n, respectively. Here, although (h) to (n) in FIG. 7 are shown to be small because of the space of the drawing, (h) to (n) in FIG. 7 are the same as (a) to (g) in FIG. It is the figure which expressed the content.

  At the time of generation of the frame a, an ultrasonic beam is generated so that the leftmost scanning line 1a is inclined by 15 °. The rightmost scanning line 1a is vertical (0 °). In the case of the example shown here, the inclination of each scanning line 1a is adjusted so that the middle scanning line 1a on the left and right gradually changes from 15 ° to 0 ° from the left end to the right end. Further, at the time of generation of this frame a, in the delay circuit of the transmission unit 2, the pulse generation timing for each channel is adjusted so that it becomes the first transmission side focal position d3 of the focal position set 23 shown in FIG. And an ultrasonic pulse of frequency f3 is transmitted.

  In addition, at the time of generation of the next frame b, an ultrasonic beam is generated so that the leftmost scanning line 1a is inclined by 10 °. The rightmost scanning line 1a is vertical (0 °). In the case of the example shown here, the inclination of each scanning line 1a is adjusted so that the middle scanning line 1a on the left and right gradually changes from 10 ° to 10 ° from the left end to the right end. In addition, when the frame b is generated, the delay circuit of the transmission unit 2 adjusts the pulse generation timing for each channel so as to be the second transmission-side focal position d2 of the focal position set 23 shown in FIG. And an ultrasonic pulse of frequency f2 is transmitted.

  Further, at the time of generation of the next frame c, an ultrasonic beam is generated so that the leftmost scanning line 1a is inclined 5 °. The rightmost scanning line 1a is vertical (0 °). In the case of the example shown here, the inclination of each scanning line 1a is adjusted so that the middle scanning line 1a on the left and right gradually changes from 5 ° to 0 ° from the left end to the right end. In addition, at the time of generation of this frame c, the delay circuit of the transmission unit 2 adjusts the pulse generation timing for each channel so as to be the third transmission side focal position d1 of the focal position set 23 shown in FIG. And an ultrasonic pulse of frequency f1 is transmitted.

  Further, at the time of generation of the next frame d, an ultrasonic beam is generated so that all the scanning lines 1a are vertical (0 °). In addition, at the time of generation of this frame d, in the delay circuit of the transmission unit 2, the pulse generation timing for each channel is adjusted so as to be the fourth transmission side focal position d2 of the focal position set 23 shown in FIG. And an ultrasonic pulse of frequency f2 is transmitted.

  Further, at the time of generation of the next frame e, the ultrasonic beam is generated so that the scanning line 1a at the left end is vertical (0 °) and the scanning line 1a at the right end is inclined 5 °. In the case of the example shown here, the inclination of each scanning line 1a is adjusted so that the middle scanning line 1a on the left and right gradually changes from 0 ° to 5 ° from the left end to the right end. In addition, at the time of generation of the frame e, the delay circuit of the transmission unit 2 adjusts the pulse generation timing for each channel so as to be the fifth transmission side focal position d1 of the focal position set 23 shown in FIG. And an ultrasonic pulse of frequency f1 is transmitted.

  Further, at the time of generation of the next frame f, the ultrasonic beam is generated so that the scanning line 1a at the left end is vertical (0 °) and the scanning line 1a at the right end is inclined 10 °. In the case of the example shown here, the inclination of each scanning line 1a is adjusted so that the middle scanning line 1a on the left and right gradually changes from 0 ° to 10 ° from the left end to the right end. In addition, at the time of generation of this frame f, the delay circuit of the transmission unit 2 adjusts the pulse generation timing for each channel so that it becomes the sixth transmission side focal position d2 of the focal position set 23 shown in FIG. And an ultrasonic pulse of frequency f2 is transmitted.

  Furthermore, at the time of generation of the next frame g, the ultrasonic beam is generated so that the scanning line 1a at the left end is vertical (0 °) and the scanning line 1a at the right end is inclined 15 °. In the case of the example shown here, the inclination of each scanning line 1a is adjusted so that the middle scanning line 1a on the left and right gradually changes from 0 to 15 ° from the left end to the right end. Further, at the time of generation of this frame g, the delay circuit of the transmission unit 2 adjusts the pulse generation timing for each channel so that it becomes the seventh transmission side focal position d3 of the focal position set 23 shown in FIG. And an ultrasonic pulse of frequency f3 is transmitted.

  Further, at the time of generation of the next frame h, the delay circuit of the transmission unit 2 returns to the top of the focal position set 23, and adjusts so as to be the transmission focal position d3 and the frequency f3. That is, here, the transmission side focal position and frequency are (d3, f3) → (d2, f2) → (d1, f1) → (d2, f2) → (d1, f1) → (d2, f2) → (( The delay pattern and frequency are changed for each frame so that the pattern of d3, f3) is cyclically repeated. Thus, generation of not only 14 frames of frame a to frame n shown in FIG. 7 but also a large number of frames is repeated. The frames a, b, c,... Thus generated are sequentially stored in the frame memory 6. The frame memory 6 has a memory capacity that does not hinder the execution of the frame synthesis process, but when the frame memory 6 is full, the frame memory 6 is overwritten in order from the previously stored frame.

  FIG. 8 is an explanatory diagram of frame combining processing in the frame combining unit.

  In the second example shown here, in the frame combining setting unit 71, the number of frames in one frame combining process is set to “7”. Therefore, in the frame combining unit 7, first, frame combining processing is performed on the seven frames a to g shown in FIG. That is, here, signal values of corresponding points of seven frames a to g are combined, and the combined signal values are associated with the points. However, in the case of the second example shown here, since the scanning deflection maximum angle is different for each frame, a weighting function AW having the scanning deflection maximum angle as a variable is defined, corresponding to each of the transmission side focal positions described above And the weighting function DW (see FIG. 5).

  For the frame a, DW3 in which the weight is increased in the vicinity area D3 of the transmission-side focal position d3 compared to the other areas D1 and D2 farther from the transmission-side focal position d3. Further, since the frame a has a scanning deflection angle of 15 °, AW 15 which has the smallest weight compared with the scanning deflection angles of 10 °, 5 ° and 0 ° is adopted for the weighting function AW. In the same manner, for the frame b, the weight DW2 is increased in the vicinity area D2 of the transmission-side focal position d2 compared to the other areas D1 and D3 farther from the transmission-side focal position d2. Further, since the frame b has a scanning deflection angle of 10 °, the weighting function AW is set to AW10 in which the weight is increased compared to the scanning deflection angle of 15 °. Further, with regard to the frame c, the weighting DW1 is made such that the weight is increased in the vicinity area D1 of the transmission-side focal position d1 compared to the other areas D2 and D3 far from the transmission-side focal position d1. Further, since the frame c has a scanning deflection angle of 5 °, it is assumed that the weight is increased as compared with the scanning deflection angle of 10 °. Further, with regard to the frame d, in the vicinity area D2 of the transmission-side focal position d2, weighting DW2 is obtained by increasing the weight compared to the other areas D1 and D3 distant from the transmission-side focal position d2. Further, since the frame d has a scanning deflection angle of 0 °, AW0 is obtained with an increased weight compared to the scanning deflection angle of 5 °. The same applies to the frames e to n.

Specifically, when the signal values of corresponding points (i) of seven frames a to g are represented by Sa (i), Sb (i),..., Sg (i),
Average value S (i) = (Sa (i) × DW3 (i) × AW15 + Sb (i) × DW2 (i) × AW10 + Sc (i) × DW1 (i) × AW5 + Sd (i) × DW2 (i) × AW0 + Se (i) i) x DW 1 (i) x AW 5 + Sf (i) x DW 2 (i) x AW 10 + Sg (i) x DW 3 (i) x AW 15 / (2 x DW 3 (i) x AW 15 + 2 x DW 2 (i) x AW 10 + 2 x DW 1 (i) ) × AW5 + DW2 (i) × AW0)
Thus, the average value S (i) is calculated and associated with the point (i).

  Here, although the weighting function AW is a fixed value for each frame, the weighting function AW may be a function of the scanning deflection maximum angle and a function of the depth position (i).

  FIG. 9 is a diagram showing seven frames used for one frame synthesis process in an overlapping manner.

  Here, as shown in FIG. 7, the scanning deflection maximum angle is different for each frame. Therefore, in the weighted averaging process, the common area of the frames a to g is extracted. That is, the area indicated by the alternate long and short dash line in FIG. 9 is truncated, and the rectangular area indicated by the solid line is extracted.

  Returning to FIG. 8, the description will be continued.

  When the frame composition processing of the first seven frames a to g is completed, frame composition processing of seven frames b to h shifted by one is performed next. The weighting for frames b to g is as described above, and the weighting for frame h is the same as for frame a. Furthermore, the weighted average processing of seven frames c to i further shifted by one is performed. The weightings for frames c through h are as described above, and the weighting for frame i is the same as the weighting for frame b. Also, the weights for frames j to n are the same as the weights for frames c to g, respectively.

  In this way, frame composition processing for seven frames at a time is sequentially performed.

  A frame generated by this frame synthesis processing is a high resolution tomogram over the entire tomogram, focusing on the three transmission side focal positions of d1, d2 and d3.

  The processing after passing through the frame combining unit 7 is as described above.

  In this example, the number of frames for one frame synthesis process is three and seven frames, but the number of frames for one frame synthesis process is limited to these frames. Rather, it may be any of a plurality in light of the need. Furthermore, here, three transmission-side focal positions d1, d2, d3, three frequencies f1, f2, f3, and scanning deflection angles of 15 °, 10 °, 5 °, 0 °, -5 °, -10 °,- Although the 15 ° example has been described, these may also be any of several in light of the need. However, the number of focal positions on the transmission side, the number of frequencies, and the number of scanning deflection angles are limited to the same number as or less than the number of frames on which one frame synthesis process is performed.

  Further, although the example in which the frame combining unit 7 is placed between the B mode signal processing unit 5 and the frame correlation unit 8 as shown in FIG. 1 has been described here, the frame combining unit 7 is not necessarily limited to the B mode. The signal processing unit 5 and the frame correlation unit 8 do not have to be placed, and may be placed before the logarithmic compression unit 4.

Reference Signs List 1 ultrasound probe 1a scanning line 2 transmitting unit 21 focal position setting unit 3 receiving unit 31 scanning control unit 4 logarithmic compression unit 5 B mode signal processing unit 6 frame memory 7 frame combining unit 71 frame combining setting unit 8 frame correlation unit 9 cine memory 10 Digital scan converter (DSC)
11 display unit 30 living body 100 ultrasonic diagnostic apparatus

Claims (5)

While scanning the inside of the subject with an ultrasound beam, the reflected ultrasound is received to obtain a received signal, and a time-sequential frame image is generated based on the received signal, and a tomographic image in the subject derived from the frame image An ultrasonic diagnostic apparatus for displaying an image,
The transmission focal position is changed frame by frame in accordance with a focal position set consisting of a plurality of predetermined predetermined transmission focal positions of an ultrasonic beam to be transmitted into the object, and the transmission focal position is changed A scan control unit that repeats scanning of the inside of the subject with the ultrasonic beam while circulating each of the plurality.
A frame combining unit that sequentially repeats combining processing of a plurality of frame images arranged in time series with respect to time-series frame images generated based on the received signal;
An ultrasonic diagnostic apparatus comprising: a display unit for displaying a tomogram composed of a frame image after the combining process in the frame combining unit.   The frame combining unit is configured to use a weighting function in which an area near the transmission-side focal point of each frame image is weighted more than a distance area distant from the transmission-side focal point of each frame image The ultrasonic diagnostic apparatus according to claim 1, wherein the processing is performed.   The ultrasonic diagnostic apparatus according to claim 1, further comprising: a setting unit that adjustably sets a plurality of transmission-side focal positions constituting the focal position set.   The scan control unit performs control to change the scan deflection maximum angle on a frame-by-frame basis, and sets the scan deflection maximum angle to a frame that sets the transmission-side focus position deeper according to the focus position set. The ultrasonic diagnostic apparatus according to any one of claims 1 to 3, characterized in that:   The scan control unit changes the transmission-side focal position for each frame according to the focal position set and circulates the changes of the transmission-side focal position for each of the plurality, and the higher the frequency is, the shallower the transmission-side focal position. The ultrasonic diagnostic apparatus according to any one of claims 1 to 4, wherein scanning within the subject is repeated with sound waves.

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