JP7015640B2 - Ultrasonic diagnostic equipment and its control method - Google Patents

Description

The present invention receives a reflected ultrasonic wave while scanning the inside of a subject with an ultrasonic beam to obtain a received signal, generates a plurality of time-series frame images based on the received signal, and is derived from the frame image. The present invention relates to an ultrasonic diagnostic apparatus for displaying a tomographic image (so-called B-mode image) in a subject and a control method thereof .

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

One important theme in this ultrasonic diagnostic apparatus is how to generate and display a tomographic image with less noise such as speckle noise and artifacts.

Regarding the reduction of speckle noise, the so-called frequency compound method is known as one technique for realizing it. In this frequency compound method, when the ultrasonic beam transmitted into the subject is a pulse wave, for example, when the center frequency f0 is f0 = 3.5 MHz, the frequency f of the ultrasonic beam is f = 2.0 MHz or more. Utilizing the fact that it extends to a range of about 5.0 MHz, the receiving side is divided into, for example, a frequency band of f = 2.0 MHz to 3.5 MHz and a frequency band of f = 3.5 MHz to 5.0 MHz. It is a technology that cancels speckle noise by receiving signals simultaneously in each band and adding the signals generated for each band to each other.

However, this conventional frequency compound method requires a circuit having twice the scale as compared with the case where this frequency compound method is not adopted, and the scale of hardware is large and the cost is high.

Japanese Unexamined Patent Publication No. 2014-144113

In view of the above circumstances, the present invention is an ultrasonic diagnostic apparatus capable of generating and displaying a tomographic image in which noise such as speckle noise and artifacts is reduced with less hardware restrictions as compared with the frequency compound method. The purpose is to provide the control method .

The ultrasonic diagnostic apparatus of the present invention that achieves the above object is
While scanning the inside of the subject with an ultrasonic beam, the reflected ultrasonic wave is received to obtain a received signal, a time-series frame image is generated based on the received signal, and a tomography in the subject derived from the frame image is generated. It is an ultrasonic diagnostic device that displays an image.
The frequency of the ultrasonic beam transmitted into the subject is changed frame by frame according to an ordered frequency set consisting of a plurality of predetermined frequencies, and the frequency change is circulated for each frame. A scanning control unit that repeats scanning inside the subject with an ultrasonic beam,
A frame compositing unit that sequentially repeats a compositing process of a plurality of frame images arranged in time series for a time-series frame image generated based on the received signal.
It is characterized by including a display unit for displaying a tomographic image composed of a frame image after a frame composition process in the frame composition unit.

According to the ultrasonic diagnostic apparatus of the present invention, a plurality of tomographic images generated by transmission / reception of a plurality of ultrasonic waves having different frequencies are frame-synthesized, so that a tomographic image with reduced speckle noise is generated and displayed. be able to.

Further, according to the ultrasonic diagnostic apparatus of the present invention, by frame-synthesizing a plurality of tomographic images generated by transmitting and receiving a plurality of ultrasonic waves having different frequencies, a plurality of faults are formed on the axis of each ultrasonic beam. The main lobes in the image are overlapped and enhanced, and the gratin gloves on both sides of the axis of each ultrasound beam are leveled due to the different distribution positions for tomographic images obtained at different frequencies. As a result, according to the ultrasonic diagnostic apparatus of the present invention, it is possible to obtain an effect that cannot be obtained by the conventional frequency compound method, that is, a tomographic image having good contrast and reduced artifacts is generated.

Here, it is preferable that the ultrasonic diagnostic apparatus of the present invention further includes a setting unit for freely adjusting a plurality of frequencies constituting the frequency set.

By freely setting the frequency of the transmitted and received ultrasonic waves, it is possible to set the frequency according to the purpose of the examination at that time, such as adjusting the frequency to suit the purpose of the examination.

Further, in the ultrasonic diagnostic apparatus of the present invention, the scanning control unit changes the transmission / reception frequency of ultrasonic waves for each frame based on the frequency set, and circulates the change of the transmission / reception frequency for each frame. Further, it is also a preferable embodiment that the higher the transmission / reception frequency is, the more the scanning in the subject is repeated with the ultrasonic beam in which the transmission side focal position of the ultrasonic beam transmitted into the subject is set to the shallow transmission side focal position.

The higher the frequency of the ultrasonic wave, the higher the resolution of the tomographic image. However, ultrasonic waves with high frequencies are severely attenuated and are not suitable for examination in deep areas. Therefore, the transmission frequency of the ultrasonic wave and the focal position on the transmitting side are linked, and the lower the transmitting frequency of the ultrasonic wave is, the deeper the focal position on the transmitting side is set. By setting it on the shallow side, the pennetration in the deep region is enhanced to obtain a tomographic image that can be observed in the deep region, and the artifacts in the shallow region are reduced and the resolution is also improved.

Further, in the ultrasonic diagnostic apparatus of the present invention, the frame synthesizing unit is based on a weighting function according to the transmission / reception frequency of the attenuation ultrasonic waves in the depth direction in the subject, which compensates for the attenuation in the depth direction in the subject. Weighting is also a preferred embodiment.

High frequency ultrasonic waves are more attenuated than low frequency ultrasonic waves. Therefore, by performing weighting to compensate for this attenuation, the effect of the frequency compound can be enhanced even in a deep region.

Further, in the ultrasonic diagnostic apparatus of the present invention, the scanning control unit controls to change the maximum scanning deflection angle for each frame, and the frame having a higher ultrasonic transmission frequency according to the frequency set is smaller. Setting the maximum scanning deflection angle is also one of the preferred embodiments.

High-frequency ultrasonic waves have larger artifacts when the scanning deflection angle is large than low-frequency ultrasonic waves. Therefore, by setting the scan deflection maximum angle to a smaller frame as the ultrasonic wave transmission frequency is higher, the artifact of the generated tomographic image is reduced.

According to the above invention, there are few hardware restrictions as compared with the conventional frequency compound method, and an ultrasonic diagnostic apparatus capable of generating and displaying a tomographic image with reduced noise such as speckle noise and artifacts. And its control method are realized.

It is a block diagram which shows the structure of the ultrasonic diagnostic apparatus as one Embodiment of this invention. It is a figure which showed the 1st example of a frequency set. It is an image diagram of a plurality of time-series frames representing a tomographic image. It is explanatory drawing of the frame composition processing in a frame composition part. It is a figure which showed the 2nd example of a frequency set. It is an image diagram of a plurality of time-series frames representing a tomographic image. It is explanatory drawing of the frame composition processing in 2nd example. It is a figure which showed the weighting function about the focal position on the transmitting side. It is a figure which showed the 3rd example of a frequency set. It is an image diagram of a plurality of time-series frames representing a tomographic image. It is explanatory drawing of the frame composition processing in 3rd example. It is a figure which superposed the seven frames used for one frame composition processing.

Hereinafter, embodiments of the present invention will be described.

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

The ultrasonic diagnostic apparatus 100 shown in FIG. 1 is provided with an ultrasonic probe 1. The ultrasonic probe 1 is detachably replaced, and an ultrasonic probe suitable for the diagnosis site, diagnosis content, etc. of the living body 30 is used. In the ultrasonic probe 1, an oscillator (not shown) such as piezoelectric ceramics is arranged at the tip of the living body 30 on the side where it is applied to the body surface. Further, the transmitting unit 2 and the receiving unit 3 are connected to the ultrasonic probe 1.

The transmission unit 2 includes a pulse generator that generates a rate pulse that gives a repeat transmission cycle (for example, 4 KHz). The transmitter 2 has, for example, a 64-channel pulse driver and a delay circuit. The pulse driver generates a vibration pulse having a period determined by a set transmission frequency (for example, 2.5 MHz) at the timing of the rate pulse and applies it to the vibrator of the ultrasonic probe 1. The delay circuit converges the ultrasonic beam and gives a predetermined delay to the pulse generation timing for each channel in order to give directivity. As a result, the directional ultrasonic beam is transmitted in a pulse shape in the living body 30. In this way, the ultrasonic probe 1 sequentially transmits an ultrasonic beam extending into the living body 30 along each of, for example, 256 scanning lines at a rate pulse period, and scanning for one frame is completed. do.

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

The received signal output from the B mode signal processing unit 7 is input to the frame correlation unit 8. In the frame correlation unit 8, a first-order IIR filter process is performed between the input current frame signal and the frame signal input immediately before the input current frame signal. However, in some cases, it is 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 this DSC 10, the set of one frame of the received signal for each scanning line 1a is converted into a signal suitable for display on the display screen of the display unit 11 by the coordinate conversion processing and the linear interpolation processing. A signal suitable for display on the display screen of the display unit 11 generated by signal conversion in 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 tomographic image based on it is displayed.

Next, the frame composition unit 5, the frame composition setting unit 51, and the frequency setting unit 21 will be described.

In the frame composition setting unit 51, the number of frames for which one frame composition process is performed is set. In the frequency setting unit 21, a frequency set having the same number of frequencies as the number of frames in one frame composition process set in the frame composition setting unit 51 is set.

FIG. 2 is a diagram showing a first example of a frequency set.

Here, it is assumed that the number of frames for which one frame composition process is performed by the frame composition setting unit 51 is set to "3". In that case, the frequency set 22 is composed of three frequencies, as shown in FIG. Here, the frequencies f1, f2, and f3 are f1> f2> f3, the frequency f1 is the highest frequency among these three, the frequency f2 is a medium frequency, and the frequency f3 is. It is the lowest frequency of these three. These three frequencies f1, f2, and f3 are preset to appropriate values for the entire area from the shallow region to the deep region in the tomographic image to be examined.

FIG. 3 is an image diagram of a plurality of time-series frames representing a tomographic image.

Here, it is assumed that an ultrasonic probe for linear scanning is attached as the ultrasonic probe 1 and that the linear scan is controlled by the scanning control unit 31. Here, the linear scan refers to a scanning method in which each scanning line 1a (traveling direction of each ultrasonic beam) extends in parallel with each other and shifts in the lateral direction.

3 (a) to 3 (f) show the received signals for each frame generated in time series. Here, the received signals for each frame shown in FIGS. 3A to 3F are referred to as frames a to frame f, respectively.

When the frame a is generated, the pulse generator of the transmission unit 2 transmits a vibration pulse having a period corresponding to the frequency f1 so that the ultrasonic wave of the first frequency f1 of the frequency set 22 shown in FIG. 2 is transmitted. To generate. Further, here, the delay circuit of the transmission unit 2 adjusts the pulse generation timing for each channel so that the focus on the transmission side is located substantially in the center in the depth direction, which is indicated by the reference numeral “d2” in FIG. Even when each frame below the frame b is generated, the focal position on the transmitting side is fixed at d2.

Similarly, when the frame b is generated, the pulse generator of the transmission unit 2 generates a vibration pulse having a period corresponding to the second frequency f2 of the frequency set 22 shown in FIG. 2, and the frame c is generated. At this time, the pulse generator of the transmission unit 2 generates a vibration pulse having a period corresponding to the third frequency f3 of the frequency set 22 shown in FIG. Further, when the next frame d is generated, the pulse generator of the transmission unit 2 returns to the beginning of the frequency set 22 and generates a vibration pulse having a period corresponding to the frequency f1. That is, here, the period of the vibration pulse is changed for each frame so that the frequencies are cyclically f1, f2, and f3. In this way, not only the 6 frames of the frames a to f shown in FIG. 3 but also a large number of frames are repeatedly generated. The frames a, b, c, ... Generated in this way are sequentially stored in the frame memory 4. The frame memory 4 has a memory capacity that does not hinder the execution of the frame composition process described below, but when the frame memory 4 becomes full, the frames are overwritten in order from the previously stored frame.

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

In the example shown here, the number of frames in one compositing process is set to "3" in the frame compositing setting unit 51. Therefore, the frame composition setting unit 51 first sets the weight function FW for each transmission / reception frequency for the three frames a to c shown in FIG. That is, here, the signal values of the points corresponding to each other in the three frames a to c are weighted and averaged, and the averaged signal values are associated with the points. The weighting function FW for each transmission frequency may be the function FW (i) at the depth position (i). Details will be described later.

When the frame composition processing of the three frames a to c is completed, the frame composition processing for the three frames b to d shifted by one is next executed. Next, the frame composition process is executed for the three frames c to e that are further offset by one.

In this way, the frame synthesizing unit 5 sequentially executes the frame synthesizing process for each of the three frames. The frame generated by this frame composition process is a tomographic image obtained by synthesizing received signals having three frequencies of f1, f2, and f3, in which noise such as speckle noise and artifacts is efficiently reduced.

The processing after passing through the frame synthesizing unit 5 is as described above.

FIG. 5 is a diagram showing a second example of the frequency set.

Similar to the first example described above, in this second example as well, it is assumed that the number of frames for which one frame composition process is performed by the frame composition setting unit 51 is set to "3". In that case, the frequency set 22 is composed of three frequencies, as shown in FIG. Here, the frequencies f1, f2, and f3 are f1> f2> f3, the frequency f1 is the highest frequency among these three, the frequency f2 is a medium frequency, and the frequency f3 is. It is the lowest frequency of these three. These three frequencies f1, f2, and f3 are preset to values suitable for examining the entire area from the shallow region to the deep region in the tomographic image. The frequency can be changed by the user, such as adopting f1 instead of the frequency f3 of 3.

Further, the frequency set 23 shown in FIG. 5 also records a set of focal positions d1, d2, and d3 on the transmitting side. The focal positions d1, d2, and d3 on the transmitting side are d1 <d2 <d3. That is, the highest frequency f1 among the three frequencies f1, f2, f3 set in the frequency set 23 is located at the shallowest position in the living body 30 among the three transmitting side focal positions d1, d2, d3. A certain transmitting side focal position d1 is associated with it. Further, the medium frequency f2 is associated with the transmitting side focal position d2 at the medium depth position, and the lowest frequency f3 is associated with the transmitting side focal position d3 at the deepest position. There is. This is because the higher the frequency, the higher the resolution can be obtained, but on the other hand, the higher the frequency, the more severe the attenuation, and it is difficult to obtain an image in a deep region. These three frequencies f1, f2, f3 and the three transmitting side focal positions d1, d2, d3 are preset to appropriate values for examining the entire area from the shallow region to the deep region in the tomographic image. However, it is also possible for the user to change the focal position on the transmitting side.

FIG. 6 is an image diagram of a plurality of time-series frames representing a tomographic image.

Here, as in the first example described above, it is assumed that the ultrasonic probe 1 for linear scan is mounted as the ultrasonic probe 1, and that the scan control unit 31 controls the linear scan. ..

6 (a) to 6 (f) show the received signals for each frame generated in time series. Here, the received signals for each frame shown in FIGS. 6A to 6F are referred to as frames a to frame f, respectively.

When the frame a is generated, the pulse generator of the transmission unit 2 generates a vibration pulse having a period corresponding to the first frequency f1 of the frequency set 23 shown in FIG. At the same time, in the delay circuit of the transmission unit 2, the pulse generation timing for each channel is adjusted so as to be the first transmission side focal position d1 of the frequency set 23 shown in FIG. Similarly, when the frame b is generated, the pulse generator of the transmission unit 2 generates a vibration pulse having a period corresponding to the second frequency f2 of the frequency set 23, and the delay circuit of the transmission unit 2 generates a vibration pulse. It is adjusted so that it is the second transmission side focal position d2 of the frequency set 23, and when the frame c is generated, a vibration pulse having a period corresponding to the third frequency f3 of the frequency set 23 is generated and the transmission unit is generated. In the delay circuit of 2, the frequency set 23 is adjusted to be the third transmission side focal position d3. Further, when the next frame d is generated, the frequency set 23 is returned to the beginning, and the pulse generator of the transmission unit 2 generates a vibration pulse having a period corresponding to the first frequency f1 of the frequency set 23 and transmits the vibration pulse. In the delay circuit of the unit 2, adjustment is made so that the focal position on the transmitting side is d1. That is, here, vibration pulses having different periods are generated so that the ultrasonic frequency is cyclically f1, f2, f3, and the transmission side focal position is cyclically d1, d2, d3. The transmission delay pattern is changed for each frame. In this way, not only the 6 frames of the frames a to f shown in FIG. 6 but also a large number of frames are repeatedly generated. The frames a, b, c, ... Generated in this way are sequentially stored in the frame memory 4. The frame memory 4 has a memory capacity that does not hinder the execution of the frame composition process described below, but when the frame memory 4 becomes full, the frames are overwritten in order from the previously stored frame.

FIG. 7 is an explanatory diagram of the frame composition process in the second example.

Also in the second example shown here, the number of frames in one compositing process is set to "3" in the frame compositing setting unit 51. Therefore, in the frame synthesizing unit 5, first, the frame synthesizing process is performed on the three frames a to c shown in FIG. That is, here, the signal values of the points corresponding to each other in the three frames a to c are weighted and averaged, and the averaged signal values are associated with the points.

However, in the frame composition processing here, two types of weighting, a weighted FW for the transmission frequency and a weighted DW for the focal position on the transmitting side, are adopted. Both FW and DW are functions of depth (i).

FIG. 8 is a diagram showing a weighting function for the focal position on the transmitting side.

Regarding the weighting function DW for the transmission side focus position, for the frame a, the weighting of the region D1 near the transmission side focus position d1 is increased as compared with the other regions D2 and D3 away from the transmission side focus position d1. .. Here, as an example, the signal value of each point (i) in the region D1 is tripled. On the other hand, each point (i) in the other regions D2 and D3 is linearly reduced from three times the signal value of that point to obtain a weight function DW1 (i) in the depth direction. Similarly, for the frame b, the weighting of the region D2 near the transmission side focal position d2 is increased as compared with the other regions D1 and D3 away 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, for each point (i) in the other regions D1 and D3, the weight is linearly reduced from 3, and the function DW2 (i) in the depth direction is used. Further, with respect to the frame c, the weighting of the region D3 in the vicinity of the focal position d3 on the transmitting side is increased as compared with the other regions D1 and D2 away from the focal position d3 on the transmitting side. Here, as an example, the signal value of each point (i) in the region D3 is tripled. On the other hand, for each point (i) in the other regions D1 and D2, the weight is linearly reduced from 3, and the function DW3 (i) in the depth direction is used.

Further, the function form of the weighting function for the frequency is determined for each frequency f1, f2, f3 so that the attenuation for each frequency f1, f2, f3 depth (i) is compensated. Here, the functional forms for each frequency f1, f2, and f3 are FW1 (i), FW2 (i), and FW3 (i), respectively.

Specifically, when the signal values of the points corresponding to each other in the three frames a to c are Sa (i), Sb (i), and Sc (i),
Mean value S (i) = (Sa (i) × DW1 (i) × FW1 (i) + Sb (i) × DW2 (i) × FW2 (i) + Sc (i) × DW3 (i) × FW3 (i) / (DW1 (i) x FW1 (i) + DW2 (i) x FW2 (i) + DW3 (i) x FW3 (i))
Therefore, the average value S (i) is calculated and associated with the point (i).

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

In this way, the frame composition process of three frames is sequentially executed. The frame generated by this frame composition process is a frame in which three frames having three different frequencies f1, f2, and f3 are combined, speckle noise and artifacts are reduced, and three transmissions of d1, d2, and d3 are transmitted. Focusing on the lateral focal position, the tomographic image has high resolution for shallow areas in the tomographic image and enhanced pennetration for deep areas.

The processing after passing through the frame composition processing unit 5 is as described above.

FIG. 9 is a diagram showing a third example of the frequency set.

Here, it is assumed that the number of frames to be combined once by the frame composition setting unit 51 is set to "7". In that case, as shown in FIG. 9, the frequency set 24 is composed of seven frequencies that allow overlap. As in the case of FIGS. 2 and 5, again, the frequencies f1, f2, and f3 are f1> f2> f3, the frequency f1 is the highest frequency among these three, and the frequency f2 is medium. The frequency is about, and the frequency f3 is the lowest of these three frequencies. These three frequencies f1, f2, and f3 are preset to appropriate values for the entire tomographic image to be examined.

Here, in the frequency set 24 shown in FIG. 9, f1 appears twice, f2 appears three times, and f3 appears twice. That is, the example shown here is set with a little emphasis on the tomographic image of medium frequency.

Further, in the frequency set 24 shown in FIG. 9, a set of focal positions d1, d2, and d3 on the transmitting side is also recorded. The focal positions d1, d2, and d3 on the transmitting side are d1 <d2 <d3. That is, the highest frequency f1 among the three frequencies f1, f2, f3 set in the frequency set 24 is located at the shallowest position in the living body 30 among the three transmitting side focal positions d1, d2, d3. A certain transmitting side focal position d1 is associated with it. Further, the medium frequency f2 is associated with the transmitting side focal position d2 at the medium depth position, and the lowest frequency f3 is associated with the transmitting side focal position d3 at the deepest position. There is. This is because the higher the frequency, the higher the resolution can be obtained, but on the other hand, the higher the frequency, the more severe the attenuation, and it is difficult to obtain an image in a deep region. These three frequencies f1, f2, f3 and the three transmitting side focal positions d1, d2, d3 are preset to appropriate values for the entire tomographic image to be examined.

FIG. 10 is an image diagram of a plurality of time-series frames representing a tomographic image.

Here, it is assumed that the scanning control unit 31 controls to realize a frame composition method called a spatial compound method in which the scanning deflection angles of each frame are different.

Here, the spatial compound method refers to a technique of sequentially synthesizing frames arranged in time series while cyclically switching the scanning deflection angle of the ultrasonic beam between frames. This spatial compound method is used for the examination of tissues that are hidden behind hard tissues such as bones and do not appear on the tomographic image from directly above. Here, an example in which the spatial compound method is combined with the feature of the present embodiment that the frequency of the ultrasonic wave is cyclically changed and the focal positions on the transmitting side are sequentially set at a plurality of locations will be described.

10 (a) to 10 (n) show the received signals for each frame generated in time series. Here, the received signals for each frame shown in FIGS. 10A to 10N are referred to as frames a to frame n, respectively. Here, FIGS. 10 (h) to 10 (n) are shown small due to the space in the drawings, but FIGS. 10 (h) to 10 (n) are the same as FIGS. 10 (a) to 10 (g), respectively. It is a figure expressing the contents.

When the frame a is generated, the ultrasonic beam is generated so that the scanning line 1a at the left end is tilted 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 scanning lines 1a in the middle of the left and right gradually change from 15 ° to 0 ° from the left end to the right end. Further, when the frame a is generated, the ultrasonic pulse of the first frequency f3 of the frequency set 24 shown in FIG. 9 is transmitted, and the ultrasonic pulse is set to the first transmission side focal position d3 of the frequency set 24. In addition, the pulse generation timing for each channel is adjusted.

Further, when the next frame b is generated, the ultrasonic beam is generated so that the scanning line 1a at the left end is tilted 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 scanning lines 1a in the middle of the left and right gradually change from 10 ° to 0 ° from the left end to the right end. Further, when the frame b is generated, the ultrasonic pulse of the second frequency f2 of the frequency set 24 shown in FIG. 9 is transmitted, and the ultrasonic pulse is set to the second transmission side focal position d2 of the frequency set 24. In addition, the pulse generation timing for each channel is adjusted.

Further, when the next frame c is generated, the ultrasonic beam is generated so that the scanning line 1a at the left end is tilted by 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 scanning lines 1a in the middle of the left and right gradually change from 5 ° to 0 ° from the left end to the right end. Further, when the frame c is generated, the ultrasonic pulse of the third frequency f1 of the frequency set 24 shown in FIG. 9 is transmitted, and the ultrasonic pulse is set to the third transmission side focal position d1 of the frequency set 24. In addition, the pulse generation timing for each channel is adjusted.

Further, when the next frame d is generated, the ultrasonic beam is generated so that all the scanning lines 1a are vertical (0 °). Further, when the frame d is generated, the ultrasonic pulse of the fourth frequency f2 of the frequency set 24 shown in FIG. 9 is transmitted, and the ultrasonic pulse is set to the fourth transmission side focal position d2 of the frequency set 24. In addition, the pulse generation timing for each channel is adjusted.

Further, when the next frame e is generated, 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 tilted by 5 °. In the case of the example shown here, the inclination of each scanning line 1a is adjusted so that the scanning lines 1a in the middle of the left and right gradually change from 0 ° to 5 ° from the left end to the right end. Further, when the frame e is generated, the ultrasonic pulse of the fifth frequency f1 of the frequency set 24 shown in FIG. 9 is transmitted, and the ultrasonic pulse is set to the fifth transmission side focal position d1 of the frequency set 24. In addition, the pulse generation timing for each channel is adjusted.

Further, when the next frame f is generated, 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 tilted by 10 °. In the case of the example shown here, the inclination of each scanning line 1a is adjusted so that the scanning lines 1a in the middle of the left and right gradually change from 0 ° to 10 ° from the left end to the right end. Further, when the frame f is generated, the ultrasonic pulse of the sixth frequency f2 of the frequency set 24 shown in FIG. 9 is transmitted, and the ultrasonic pulse is set to the sixth transmission side focal position d2 of the frequency set 24. In addition, the pulse generation timing for each channel is adjusted.

Further, when the next frame g is generated, 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 tilted by 15 °. In the case of the example shown here, the inclination of each scanning line 1a is adjusted so that the scanning lines 1a in the middle of the left and right gradually change from 0 ° to 15 ° from the left end to the right end. Further, when the frame g is generated, the ultrasonic pulse of the 7th frequency f3 of the frequency set 24 shown in FIG. 9 is transmitted, and the ultrasonic pulse is set to the 7th transmission side focal position d3 of the frequency set 24. In addition, the pulse generation timing for each channel is adjusted.

Further, when the next frame h is generated, the delay circuit of the transmission unit 2 returns to the beginning of the frequency set 24 and adjusts so that the frequency is f3 and the focal position on the transmission side is d3. That is, here, the frequency and the focal position on the transmitting side are (f3, d3) → (f2, d2) → (f1, d1) → (f2, d2) → (f1, d1) → (f2, d2) → ( The frequency and transmission delay pattern are changed for each frame so that the patterns of f3 and d3) are cyclically repeated. In this way, not only the 14 frames of the frames a to n shown in FIG. 10 but also a large number of frames are repeatedly generated. The frames a, b, c, ... Generated in this way are sequentially stored in the frame memory 4. The frame memory 4 has a memory capacity that does not hinder the execution of the moving average process described below, but when the frame memory 5 becomes full, the frames are overwritten in order from the previously stored frame.

FIG. 11 is an explanatory diagram of the frame composition process in the third example.

In the third example shown here, the number of frames for one average processing is set to "7" in the frame composition setting unit 51. Therefore, in the frame synthesizing unit 6, first, the synthesizing process is performed on the seven frames a to g. That is, here, the signal values of the points corresponding to each other in the seven frames a to g are synthesized, and the combined signal values are associated with the points. However, in the case of the third example shown here, since the slope of the scanning line 1a is different for each frame, the weighting function AW for the maximum scanning deflection angle is defined, and the weighting function FW for each frequency and each transmission described above are defined. The frame composition process is performed by multiplying by the weighting function DW for the side focal position.

Regarding the frame a, the weighted DW3 is used for the region D3 in the vicinity of the focal position d3 on the transmitting side, which is heavier than the other regions D1 and D2 away from the focal position d3 on the transmitting side. Further, since this frame a has a scanning deflection angle of 15 °, the AW15 having the smallest weight as compared with the scanning deflection angles of 10 °, 5 °, and 0 ° is used. Further, since the frequency of the frame a is f3, the weighting function FW3 corresponding to the frequency f3 is adopted. Similarly, for the frame b, the weighted DW2 is set in the vicinity of the transmitting side focal position d2 with a weight increased as compared with the other regions D1 and D3 away from the transmitting side focal position d2. Further, since this frame b has a scanning deflection angle of 10 °, the AW10 has an increased weight as compared with the scanning deflection angle of 15 °. Further, since the frequency of the frame b is f2, the weighting function FW2 corresponding to the frequency f2 is adopted. Similarly, for the frame c, the weighted DW1 is used for the region D1 in the vicinity of the focal position d1 on the transmitting side, which is weighted more than the other regions D2 and D3 away from the focal position d1 on the transmitting side. Further, since this frame c has a scanning deflection angle of 5 °, the AW5 has an increased weight as compared with the scanning deflection angle of 10 °. Further, since the frequency of the frame c is f1, the weighting function FW1 corresponding to the frequency f1 is adopted. Similarly, for the frame d, the weighted DW2 is set in the vicinity of the transmitting side focal position d2 with a weight increased as compared with the other regions D1 and D3 away from the transmitting side focal position d2. Further, since the scanning deflection angle is 0 °, the weight of the AW0 is increased as compared with the scanning deflection angle of 5 °. Further, the FW2 corresponds to the frequency f2. The same applies to frames e to n.

Specifically, when the signal values of the points (i) corresponding to each other in the seven frames a to g are Sa (i), Sb (i), ..., Sg (i),
Mean value S (i) = (Sa (i) × DW3 (i) × AW15 × FW3 (i) + Sb (i) × DW2 (i) × AW10 × FW2 (i) + Sc (i) × DW1 (i) × AW5 x FW1 (i) + Sd (i) x DW2 (i) x AW0 x FW2 (i) + Se (i) x DW1 (i) x AW5 x FW1 (i) + Sf (i) x DW2 (i) x AW10 x FW2 (i) + Sg (i) x DW3 (i) x AW15 x FW3 (i) / (2 x DW3 (i) x AW15 x FW3 (i) + 2 x DW2 (i) x AW10 x FW2 (i) + 2 x DW1 (i) x AW5 x FW1 (i) + DW2 (i) x AW0 x FW2 (i))
Therefore, the average value S (i) is calculated and associated with the point (i).

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

FIG. 12 is a diagram showing seven frames used for one frame composition process superimposed.

Here, as shown in FIG. 10, the scanning area is different for each frame. Therefore, in the frame composition process, a common region of frames a to g is extracted. That is, the region shown by the alternate long and short dash line in FIG. 12 is truncated and the rectangular region shown by the solid line is extracted.

The explanation will be continued by returning to FIG.

When the frame composition processing of the first seven frames a to g is completed, the frame composition processing of the seven frames b to h shifted by one is executed next. The weighting for the frames b to g is as described above, and the weighting for the frame h is the same as the weighting for the frame a. Next, the frame composition process of seven frames c to i shifted by one is executed. The weighting for the frames c to h is as described above, and the weighting for the frame i is the same as the weighting for the frame b. Further, the weighting for the frames j to n is the same as the weighting for the frames c to g, respectively.

In this way, the frame composition process of seven frames is sequentially executed at one time.

The frame generated by this frame composition process is a frame in which seven frames consisting of three different frequencies f1, f2, and f3 are combined, and speckle noise and artifacts on the tomographic image are offset to reduce noise. In addition, a high-resolution tomographic image is obtained over the entire tomographic image, focusing on the three transmission-side focal positions of d1, d2, and d3.

The processing after passing through the frame synthesizing unit 5 is as described above.

Here, an example in which the number of frames for which one frame composition process is performed is 3 frames and an example for 7 frames are shown, but the number of frames for which one frame composition process is performed is limited to these number of frames. However, it may be any plurality in the light of need. In addition, here, examples of three frequencies, three transmission side focal positions d1, d2, d3, and scanning deflection angles of 15 °, 10 °, 5 °, 0 °, -5 °, -10 °, and -15 °. However, these may also be any plurality in the light of need. However, the number of transmission frequencies, transmission side focal positions, and scanning deflection angles is limited to the same number as or less than the number of frames for which one frame composition process is performed.

Further, as shown in FIG. 1, an example in which the frame synthesizing unit 5 is placed before the logarithmic compression unit 6 has been described, but the frame synthesizing unit 5 does not necessarily have to be placed here, and the logarithmic compression unit 5 is not necessarily placed here. It may be placed at a position later than 6.

1 Ultrasonic probe 1a Scan line 2 Transmitter 21 Frequency setting unit 3 Receiver 31 Scanning control unit 4 Frame memory 5 Frame composition unit 51 Frame composition setting unit 6 Logarithmic compression unit 7 B mode signal processing unit 8 Frame correlation unit 9 Cine Memory 10 Digital Scan Converter (DSC)
11 Display unit 30 Living body 100 Ultrasonic diagnostic device

Claims (9)

While scanning the inside of the subject with an ultrasonic beam, the reflected ultrasonic wave is received to obtain a received signal, a time-series frame image is generated based on the received signal, and a tomography in the subject derived from the frame image is generated. It is an ultrasonic diagnostic device that displays an image.
The frequency of the ultrasonic beam transmitted into the subject is changed frame by frame according to an ordered frequency set consisting of a plurality of predetermined frequencies, and the frequency change is circulated for each frame. A scanning control unit that repeats scanning inside the subject with an ultrasonic beam,
A frame compositing unit that sequentially repeats a compositing process of a plurality of frame images arranged in time series for a time-series frame image generated based on the received signal.
It is provided with a display unit for displaying a tomographic image composed of a frame image after frame composition processing in the frame composition unit.
The frame synthesizing unit performs a synthesizing process by weighting and averaging the signal values of the corresponding points of the plurality of frame images to be synthesized by applying weights according to the depth positions of the corresponding points. An ultrasonic diagnostic apparatus characterized in that a weight corresponding to a depth position is determined for each frame image according to the distance from the transmission side focal position of the ultrasonic beam at the time of acquiring the frame image . The ultrasonic diagnostic apparatus according to claim 1, further comprising a setting unit for freely setting a plurality of frequencies constituting the frequency set. The scanning control unit changes the transmission / reception frequency of ultrasonic waves for each frame based on the frequency set and circulates the change of the transmission / reception frequency for each of the plurality of frames. The ultrasonic diagnostic apparatus according to claim 1 or 2, wherein scanning in the subject is repeated with an ultrasonic beam in which the transmitting side focal position of the ultrasonic beam transmitted to the inside is set to a shallow transmitting side focal position. The frame synthesizing unit sets the signal values of the corresponding points of the plurality of frame images to be synthesized, the depth position of the corresponding points, the transmission / reception frequency of the ultrasonic beam at the time of acquiring the frame image, and the focal position on the transmitting side. The ultrasonic diagnostic apparatus according to claim 3, wherein a synthetic process is performed by applying a corresponding weight and weighting and averaging. The ultrasonic diagnostic apparatus according to claim 4, wherein the weight with respect to the transmission / reception frequency is determined so as to compensate for the ultrasonic attenuation according to the corresponding transmission side focal position. The ultrasonic diagnostic apparatus according to any one of claims 3 to 5, wherein the plurality of frequencies included in the frequency set include the same frequency. The scanning control unit controls to change the maximum scanning deflection angle for each frame, and is characterized in that the frame having a higher ultrasonic transmission / reception frequency according to the frequency set is set to a smaller maximum scanning deflection angle. The ultrasonic diagnostic apparatus according to any one of claims 1 to 6. While scanning the inside of the subject with an ultrasonic beam, the reflected ultrasonic wave is received to obtain a received signal, a time-series frame image is generated based on the received signal, and a tomography in the subject derived from the frame image is generated. It is a control method executed by an ultrasonic diagnostic device that displays an image.
The frequency of the ultrasonic beam transmitted into the subject is changed frame by frame according to an ordered frequency set consisting of a plurality of predetermined frequencies, and the frequency change is circulated for each frame. A scanning control process that repeats scanning inside the subject with an ultrasonic beam,
A frame synthesizing step in which a synthesizing process of a plurality of frame images arranged in chronological order is sequentially repeated for a time-series frame image generated based on the received signal.
It has a display step of displaying a tomographic image composed of a frame image after the frame synthesis process in the frame synthesis step on a display device.
In the frame synthesizing step, the signal values of the corresponding points of the plurality of frame images to be combined are weighted and averaged by applying weights according to the depth positions of the corresponding points to perform the synthesizing process. A control method for an ultrasonic diagnostic apparatus, characterized in that a weight according to a depth position is determined for each frame image according to a distance from the transmission side focal position of the ultrasonic beam used for acquiring the frame image. .. A program for causing a computer included in the ultrasonic diagnostic apparatus to execute each step of the control method of the ultrasonic diagnostic apparatus according to claim 8.

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