WO2013055129A2

WO2013055129A2 - Method and device for removing an hifu interference signal

Info

Publication number: WO2013055129A2
Application number: PCT/KR2012/008275
Authority: WO
Inventors: 장진호; 송재희; 유양모; 송태경; 이유화
Original assignee: 서강대학교 산학협력단
Priority date: 2011-10-13
Filing date: 2012-10-11
Publication date: 2013-04-18
Also published as: WO2013055129A3; CN103974665A; CN103974665B

Abstract

The present invention relates to a method of removing an HIFU interference signal. The method of the present invention is characterized by transmitting ultrasonic image signals while transmitting at least two HIFU signals out of phase, receiving ultrasonic signals including reflected HIFU signals and ultrasonic image signals when at least two HIFU signals and ultrasonic image signals are reflected from an object, summing the received ultrasonic signals, and removing basic frequency components and harmonic frequency components from HIFU signals in the received ultrasonic signals. The method of the present invention may acquire a monitor image from which HIFU interference is removed regardless of an HIFU length because a pulse inversion technique is used.

Description

HIFU interference cancellation method and device

The present invention relates to a method for removing an HIFU interference signal, and more particularly, to a method for removing an HIFU interference signal by using a pulse inversion technique to obtain a monitor image by removing HIFU interference regardless of the length of the HIFU.

During the HIFU treatment, the reaction of the treatment area is continuously observed to confirm that lesions are formed at a desired position, and the clinician is provided with information to determine whether the treatment is continued by adjusting the dose of HIFU. It is necessary to monitor the treatment site in real time. In addition, tracking and compensating for such movements is also necessary because the organs may be affected by the patient's breathing or heart rhythm to move the treatment area out of the HIFU focal point.

Although an ultrasound imaging system may provide an image of a treatment area in real time, image quality of the image may be greatly degraded due to interference of a strong HIFU signal. Various techniques have been developed to minimize the effects of interfering signals, and can be classified into short burst mode and long burst mode according to HIFU duty cycle.

In the short burst mode, since only a part of the image is affected by the interference signal, a technique of synchronizing the HIFU irradiation point with the ultrasound image acquisition point is used to prevent the ROI from interfering. Low HIFU utilization can increase treatment time and is difficult to apply in applications that use small HIFU transducers, such as the prostate, but the treatment area can be observed in real time.

In long burst mode, where the length of the HIFU pulse is long, most areas are interfering, so the interference signal must be removed directly. Among them, interleaving technique can acquire continuous monitor image by adjusting pulse repetition frequency (PRF), but cannot maintain real-time. The method using a fixed notch filter and a barker code showed that the interference signal can be minimized by suppressing the interference signal and increasing the energy of the image signal. However, it is necessary to optimize the filter according to the characteristics of the interference signal and complicated hardware to recover the code signal. To solve this problem, an interference cancellation method based on adaptive noise cancellation has also been proposed.

Therefore, in order to confirm the formation of the lesion at the desired position, the progress of the treatment, and to observe and compensate for the movements occurring during the treatment, it is necessary to monitor the treatment site using real-time images.

The first problem to be solved by the present invention is to provide a HIFU interference cancellation method that can obtain a monitor image by removing the HIFU interference irrespective of the length of the HIFU because the pulse inversion technique is used.

The second problem to be solved by the present invention is to provide a HIFU interference removal device that can observe in real time the process of lesion formation by removing the HIFU interference because the signal to obtain a monitor image at the same time as the HIFU signal will be.

The third problem to be solved by the present invention is to provide a method for setting the center frequency of the image ultrasonic signal.

Further, the present invention provides a computer-readable recording medium having recorded thereon a program for executing the above method on a computer.

In order to achieve the first object, the present invention comprises the steps of: transmitting at least two or more HIFU signals while the phase difference from each other, transmitting the image ultrasound signal; If the at least two HIFU signals and the image ultrasound signal are reflected from an object, receiving an ultrasound signal including the reflected HIFU signal and the image ultrasound signal; And summing the received ultrasonic signals to remove fundamental frequency components and harmonic frequency components of the HIFU signal included in the received ultrasonic signals.

According to an embodiment of the present disclosure, the transmitting of the image ultrasound signal may include transmitting an image ultrasound signal while transmitting two HIFU signals with a 180 degree phase difference.

In addition, the center frequency of the image ultrasound signal may be either an odd harmonic frequency or an even harmonic frequency of the HIFU signal.

According to another exemplary embodiment of the present disclosure, the removing of the fundamental frequency component and the harmonic frequency component of the HIFU signal included in the received ultrasonic signal may include adding the received ultrasonic signal to the received ultrasonic signal. The fundamental frequency component and the odd harmonic frequency component of the HIFU signal may be removed.

The transmitting of the image ultrasound signal may include transmitting an image ultrasound signal while transmitting an HIFU signal having a phase of 0 degrees, an HIFU signal having a phase of 180 degrees, and an HIFU signal having a phase of 0 degrees.

Meanwhile, by passing the received ultrasonic signal through a band cut filter or a notch filter, one or more of even-numbered harmonic frequency components of the HIFU signal included in the received ultrasonic signal may be removed, and the received ultrasonic signal may be The image ultrasonic signal may be selected by passing a band pass filter having a frequency band of the image ultrasonic signal as a bandwidth.

According to another embodiment of the present invention, the HIFU signal and the image ultrasound signal is synchronized to the ultrasound image frame, synchronization using the ultrasound image frame is the image ultrasound signal and the HIFU signal of the previous frame in any one frame HIFU signal with 180 degree phase difference can be transmitted and received together.

In addition, the HIFU signal and the image ultrasound signal is synchronized with the scan line of the ultrasound image, the synchronization using the scan line, the image ultrasound signal of any one image scan line, and the HIFU signal of the previous scan line phase 180 degrees You can send and receive HIFU signals that differ.

Furthermore, in order to achieve the first object, the step of transmitting the HIFU signal while transmitting two image ultrasound signals 180 degrees out of phase; If the image ultrasound signal and the HIFU signal are reflected from an object, receiving an ultrasound signal including the reflected image ultrasound signal and a HIFU signal; And calculating a difference between the received ultrasonic signals and removing the fundamental frequency components and the harmonic frequency components of the HIFU signal included in the received ultrasonic signals.

The present invention to achieve the second object, HIFU signal transmission unit for transmitting at least two or more HIFU signal to be out of phase with each other; An image ultrasonic signal transmitter for transmitting an image ultrasonic signal; An ultrasound signal receiver configured to receive an ultrasound signal including the reflected HIFU signal and the image ultrasound signal when the at least two HIFU signals and the image ultrasound signal are reflected from an object; And a signal adder configured to sum the received ultrasonic signals and remove a fundamental frequency component and a harmonic frequency component of the HIFU signal included in the received ultrasonic signal.

In addition, to achieve the second object, HIFU signal transmission unit for transmitting a HIFU signal; An image ultrasound signal transmitter configured to transmit an image ultrasound signal that transmits two image ultrasound signals to be 180 degrees out of phase; An ultrasound signal receiver configured to receive an ultrasound signal including the reflected HIFU signal and an image ultrasound signal when the HIFU signal and the image ultrasound signal are reflected from an object; And a signal adder configured to calculate a difference between the received ultrasonic signals and remove a fundamental frequency component and a harmonic frequency component of the HIFU signal included in the received ultrasonic signal.

In order to achieve the third object, the present invention includes the steps of transmitting and receiving a HIFU signal 180 degrees out of phase difference; Removing the fundamental frequency component and the odd harmonic frequency component of the HIFU signal by summing the two received HIFU signals; And setting one of odd-numbered harmonic frequencies of the removed HIFU signal as a center frequency of the image ultrasonic signal.

In order to solve the above other technical problem, the present invention provides a computer readable recording medium having recorded thereon a program for executing the above-described method for removing the HIFU interference signal in a computer.

According to the present invention, since the pulse inversion technique is used, the HIFU interference may be removed regardless of the length of the HIFU, thereby obtaining a monitor image.

In addition, according to the present invention, since the signal for acquiring the monitor image simultaneously with the HIFU signal is transmitted, the process of lesion formation can be observed in real time by eliminating the HIFU interference. In order to check the progress and observe and compensate for movements occurring during treatment, the treatment site may be monitored using real-time images.

Furthermore, according to the present invention, it is possible to calculate the center frequency of the ultrasound image signal that can minimize the interference of the HIFU signal in the ultrasound image signal, it is possible to generate a B-mode image of good image quality.

1 is a block diagram of a HIFU interference cancellation apparatus according to an embodiment of the present invention.

Figure 2 shows the frequency spectrum of the HIFU interference signal and the ultrasound image signal, a case where the 0 ° phase HIFU signal is transmitted.

Figure 3 shows the frequency spectrum of the HIFU interference signal and the ultrasound image signal, a case where a 180 ° phase HIFU signal is transmitted.

Figure 4 shows the frequency spectrum of the signal from which the first, third and fifth harmonic signals of HIFU are removed by pulse inversion.

5 is a frequency spectrum of an ultrasound image signal obtained after removing HIFU interference.

FIG. 6 illustrates an experimental environment for removing HIFU interference signals using a single element ultrasonic transducer.

7 shows a block diagram of a HIFU real-time monitoring experiment environment using a commercial ultrasonic imaging apparatus.

8 illustrates a time waveform and a frequency spectrum of a signal obtained by transmitting and receiving a phantom using a single element ultrasonic transducer.

Figure 9 shows a photo (a) and the structure (b) of the phantom produced in the present invention.

10 shows the time waveform and frequency spectrum of the HIFU signal causing interference.

Figure 11 shows the time waveform and frequency spectrum of the signal from which the fundamental frequency of the HIFU signal and the third and fifth harmonic signals are removed using pulse inversion.

FIG. 12 shows the time waveform and frequency spectrum of the signal from which the second and fourth harmonic signals of the HIFU signal are removed using a band pass filter.

FIG. 13 is a comparison of HIFU interference cancellation results. FIG. 13 (a) is compared with a reference signal and FIG. 13 (b) is compared with a reference signal to which a band pass filter is applied.

14 is a photograph of a phantom including lesions according to HIFU usage.

FIG. 15 illustrates a reference image when the HIFU utilization rate is 10%, an HIFU interference image, an image to which pulse inversion is applied, and an image to which a band pass filter is applied.

FIG. 16 illustrates a reference image, a HIFU interference image, an image in which pulse inversion is applied, and an image in which a band pass filter is applied when the HIFU utilization rate is 30%.

FIG. 17 illustrates a reference image when the HIFU utilization rate is 50%, an HIFU interference image, an image to which pulse inversion is applied, and an image to which a band pass filter is applied.

18 illustrates a reference image when the HIFU utilization rate is 70%, an HIFU interference image, an image to which pulse inversion is applied, and an image to which a band pass filter is applied.

19 illustrates a reference image when the HIFU utilization rate is 90%, an HIFU interference image, an image to which pulse inversion is applied, and an image to which a band pass filter is applied.

20 illustrates a conceptual diagram of inter-PRI interference according to HIFU usage rate.

21 is a conceptual diagram of a transmission and reception method for removing residual HIFU interference.

FIG. 22 illustrates an image in which residual HIFU interference is removed at a HIFU utilization rate of 90%.

23 is a flowchart illustrating a method for removing an HIFU interference signal according to an exemplary embodiment of the present invention.

24 illustrates an HIFU interference cancellation apparatus according to another embodiment of the present invention.

25 is a flowchart of a method for canceling an HIFU interference signal according to another embodiment of the present invention.

FIG. 26 is a graph illustrating the HIFU interference cancellation method of FIG. 25.

FIG. 27 illustrates an image according to the method of removing the HIFU interference signal of FIG. 25 before and after the HIFU interference signal is removed.

HIFU interference cancellation method using a pulse inversion according to an embodiment of the present invention in the phase modulation (phase modulation) method of the pulse inversion (PI: pulse inversion) and the bandpass (bandpass) filter or band-pass filter in real time interference You can remove the signal. That is, the HIFU signal is transmitted in phases of 0 ° and 180 °, and then pulse inversion is applied to remove odd-order harmonics of the interference signal, and band-pass filter for even-order harmonics existing outside the frequency band of the video signal. Remove with.

Hereinafter, the present invention will be described in more detail with reference to preferred examples.

Prior to the description of the specific contents of the present invention, for the convenience of understanding, the outline of the solution of the problem to be solved by the present invention or the core of the technical idea will be presented first.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, these examples are intended to illustrate the present invention in more detail, it will be apparent to those skilled in the art that the scope of the present invention is not limited thereby.

The configuration of the invention for clarifying the solution to the problem to be solved by the present invention will be described in detail with reference to the accompanying drawings based on the preferred embodiment of the present invention, the same in the reference numerals to the components of the drawings The same reference numerals are given to the components even though they are on different drawings, and it is to be noted that in the description of the drawings, components of other drawings may be cited if necessary. In addition, in describing the operation principle of the preferred embodiment of the present invention in detail, when it is determined that the detailed description of the known function or configuration and other matters related to the present invention may unnecessarily obscure the subject matter of the present invention, The detailed description is omitted.

In addition, throughout the specification, when a part is 'connected' to another part, it is not only 'directly connected' but also 'indirectly connected' with another element in between. Include. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, “comprises” and / or “comprising” refers to the presence of one or more other components, steps, operations and / or elements. Or does not exclude additions.

Referring to FIG. 1, the HIFU interference cancellation apparatus according to the present embodiment includes an ultrasonic transceiver 100, a signal adder 110, a filter 120, and an ultrasonic image processor 130.

The ultrasonic transceiver 100 includes a HIFU signal transmitter 101, an image ultrasonic signal transmitter 102, and an ultrasonic signal receiver 103.

The HIFU signal transmitter 101 transmits at least two or more HIFU signals to be out of phase with each other. The HIFU signal is preferably a nonlinear chirp signal. A nonlinear chirp signal may be used as the HIFU signal to secure a wider image window in the frequency domain. In case of using the linear chirp signal, there is a disadvantage in that the frame rate decreases and a motion defect occurs. However, by using the nonlinear chirp signal, frequency overlap can be effectively reduced, and the disadvantage of the linear chirp signal can be solved.

According to an embodiment of the present disclosure, the HIFU signal transmitter 101 may transmit two HIFU signals to have a 180 degree phase difference.

The image ultrasound signal transmitter 102 transmits an image ultrasound signal.

The image ultrasound signal may be any one of a short pulse, a barker code, a golay code, and a chirp code. In the non-invasive treatment using the HIFU signal, the image ultrasound signal transmitter 102 transmits an image ultrasound signal to the treatment target to obtain an internal image of the treatment target. The center frequency of the image ultrasonic signal is one of the odd harmonic frequencies of the HIFU. The interference of the HIFU can be minimized by using one of the odd-numbered harmonic frequencies of the HIFU as the center frequency of the image ultrasonic signal. The beam is focused through a beamformer to transmit an image ultrasonic signal to a target to be photographed through an image transducer. Short pulse can be used as an image ultrasonic signal. However, the short pulse has a disadvantage in that it is difficult to use for diagnosing deeply located organs due to limited penetration. Barker, Golay, or linear Chirp codes can be used to overcome limited penetration. By using coding, the signal-to-noise ratio (SNR) is improved by improving the transmission energy by 15 to 20 dB without increasing the transmission peak voltage. By using the linear chirp code, the length and bandwidth of the video signal can be adjusted.

As another example, when the HIFU signal transmitter 101 transmits an HIFU signal having a phase of 0 degrees, an HIFU signal having a phase of 180 degrees, and an HIFU signal having a phase of 0 degrees, the image ultrasonic signal transmitter 102 may generate an image ultrasonic signal. Send. The HIFU signal and the image ultrasonic signal may be transmitted sequentially or simultaneously.

The center frequency of the image ultrasound signal may be any one of an odd harmonic frequency and an even harmonic frequency of the HIFU signal.

The HIFU signal transmitting unit 101 and the image ultrasonic signal transmitting unit 102 may be synchronized with an ultrasonic image frame, and the synchronization using the ultrasonic image frame may be performed using the image ultrasonic signal and the HIFU signal of the previous frame in one frame. Synchronization is achieved by transmitting and receiving HIFU signals with phase differences.

Meanwhile, the HIFU signal transmitter 101 and the image ultrasound signal transmitter 102 may be synchronized with the scan line of the ultrasound image, and the synchronization using the scan line may include the image ultrasound signal of one image scan line and the previous scan line. Synchronization is achieved by transmitting and receiving a HIFU signal 180 degrees out of phase with the HIFU signal.

When the at least two HIFU signals and the image ultrasound signal are reflected from the object, the ultrasound signal receiver 103 receives an ultrasound signal including the reflected HIFU signal and the image ultrasound signal. The ultrasonic signal includes a HIFU signal component and an image ultrasonic component. The ultrasound signal received through the transducer is beam focused through a beamformer.

The signal summing unit 110 adds the received ultrasonic signal to remove the fundamental frequency component and the harmonic frequency component of the HIFU signal included in the received ultrasonic signal. In particular, it is preferable to remove the fundamental frequency components and odd-numbered harmonic frequency components of the HIFU signal included in the received ultrasonic signal.

The received ultrasonic signal includes a high magnitude HIFU signal component. The HIFU signal interferes with imaging the ultrasound signal. The HIFU signal transmitter 101 transmits the HIFU signal twice so that there is a 180 degree phase difference. The received ultrasonic signal includes two types of HIFU signal components having a 180 degree phase difference. The ultrasonic signals including the two types of HIFU signal components are summed. The sum of the ultrasonic signals removes the fundamental frequency component and the odd harmonic frequency component of the HIFU signal. By using one of the frequencies of the odd-numbered harmonic frequency components of the HIFU signal as the center frequency of the image ultrasonic signal, an image ultrasonic signal may be obtained without interference of the HIFU signal. When the signal storage unit stores the signal received by the ultrasonic signal receiver 103 and the signal of the next frame is received by the ultrasonic signal receiver 103, the signal adder 110 receives the previous frame signal and the newly received signal from the signal storage unit. Take the signal and add the two signals together. The two signals include HIFU signal components having a 180 degree phase difference from each other, and by adding the two signals, the fundamental frequency component and the odd harmonic frequency component of the HIFU signal are removed.

The filter unit 120 removes one or more of even-numbered harmonic frequency components of the HIFU signal included in the received ultrasonic signal by passing the ultrasonic signal summed by the signal adding unit 110 through a band cut filter or a notch filter. .

As another example, the image ultrasound signal may be selected by passing the ultrasound signal summed by the signal adding unit 110 through a band pass filter having a frequency band of the image ultrasound signal as a bandwidth.

The ultrasound image processor 130 generates a B mode image from the ultrasound signal from which the fundamental frequency component and the harmonic frequency component are removed.

The ultrasound image processor 130 generates an image using the ultrasound signal from which the interference of the HIFU signal is removed by the signal summing of the signal summing unit 110. By passing the received ultrasonic signal through a band cut filter or a notch filter, one or more of even-numbered harmonic frequency components of the HIFU signal may be removed from the ultrasonic signal. The image ultrasonic signal may be selected by passing the received ultrasonic signal through a band pass filter having a frequency band of the image ultrasonic signal as a bandwidth. When the ultrasonic signal is transmitted and received using the transducer, only a signal having a specific bandwidth may pass according to the performance of the transducer. However, when the bandwidth of the ultrasonic signal passing through the transducer is larger than the bandwidth required to obtain an ultrasound image, by selecting the image ultrasonic signal by passing the ultrasonic signal through a band pass filter to obtain only the bandwidth for obtaining an ultrasound image, The video signal quality can be improved. A B-mode image is generated from the selected ultrasonic signal. The B-mode image is an image of a cross section of a subject using ultrasound. The strong and weak reflected echoes are represented by the difference in brightness. In other words, the B-mode image is a black and white anatomical image. The B-mode image is generated by analyzing the ultrasonic signal. The B-mode image may be generated from the ultrasound signal by using one or more of short pulse, barker, golay, and chirp codes.

In addition, the signal storage unit and the control unit may further include.

The signal storage unit stores the ultrasonic signal until the ultrasonic image processing unit 130 receives the signal of the next frame to add the signals. When the next frame of the stored signal is received, the stored signal is input to the ultrasound image processor 130. It can be implemented using memory. The control unit controls the HIFU signal transmitter 101 to transmit the HIFU signal twice so that the HIFU signal transmitter 101 has a 180 degree phase difference. In addition, the video ultrasonic signal transmission unit 102 also controls the video ultrasonic signal transmission. Further, the signal storage unit stores the signal and controls the input of the signal to the signal summing unit 110. It may be implemented as a processor.

As the ultrasonic signal travels through the nonlinear medium, harmonic components are produced. Harmonic imaging has been used clinically because it has the effect of improving the resolution and contrast than when using the fundamental frequency component. In this case, a band pass filter or a phase modulation technique is used to selectively extract desired harmonic components from the received signal. Among them, the pulse reversal method is to detect the second harmonic signal, and transmits two pulses with 180 ° phase difference in the same place, and then removes the fundamental frequency and odd harmonic components by adding the two received signals. .

Hereinafter, the ultrasonic transceiver 100, the signal adder 110, and the filter 120 will be described in more detail.

The ultrasonic transceiver 100 transmits and receives two pulses each having a 180 ° phase difference in the same place to remove the HIFU interference signal by using pulse inversion.

When the HIFU signal h (t) of the HIFU signal transmitting unit 101 and the image signal u (t) of the image ultrasonic signal transmitting unit 102 are simultaneously transmitted, the signal r (t) received by the ultrasonic signal receiving unit 103 may be expressed as follows. As shown in Equation 1, harmonic signals including the fundamental frequency, the second order and the third order of the HIFU signal and the image signal are included.

Equation 1

Since the ultrasonic image transducer has the characteristics of a band pass filter, considering the center frequency and bandwidth of the HIFU transducer and the ultrasonic image transducer, the image signal is received only from the fundamental frequency component, and the HIFU signal is received from the fundamental frequency to the fifth harmonic component. The received signal r (t) may be expressed as in Equation 2.

Equation 2

In general, since the amplitude of the HIFU signal is greater than the amplitude of the video signal, H (t) present in the received signal must be removed because it serves as an interference signal that degrades the quality of the monitor image. Therefore, two signals h ₁ (t) and h ₂ (t) with a 180 ° phase difference are used as HIFU signals to remove the interference signal using the pulse reversal technique.

Equation 3

Where f ₀ is the center frequency of the HIFU signal. At this time, the received signals r ₁ (t) and r ₂ (t) may be expressed as Equation 4 below, and have a spectrum as shown in FIGS. 2 and 3 in terms of frequency, respectively.

Equation 4

The sign of the fundamental frequency and odd-order harmonic components at r ₂ (t) is reversed because the fundamental and odd-order harmonic components are phase shifted by 180 °, while the even-order harmonic components are phase shifted by 360 °. to be. Therefore, by adding the two signals, it is possible to remove the fundamental frequency and odd harmonic signals as shown in Equation 5.

Equation 5

Thereafter, if the remaining second and fourth harmonic signals are removed using a band pass filter, a signal similar to the original ultrasonic image signal u _f (t) can be obtained as shown in Equation 6, and FIG. Frequency spectrum of an ultrasound image signal obtained after removing HIFU interference.

Equation 6

An experiment was performed to confirm that the HIFU interference signal can be removed using pulse inversion, and the experimental environment at this time is shown in FIG. 6.

The single-element HIFU transducer used in the experiment has a 20 mm center open for image acquisition, a center frequency of 1.1 MHz, and a geometric focusing distance of 62.6 mm. Using the arbitrary waveform editor, two pulses used for pulse inversion were generated at a pulse repetition interval, and then input to a function generator. The signal amplified with a gain of 49 dB in the high frequency amplifier is transmitted to the phantom in the tank through an impedance matching network that resonates around 1.1 MHz. The water in the tank was boiled and then cooled to room temperature to remove bubbles, and an ultrasonic sound absorber was installed at the bottom of the tank to remove the reverberation signal from the bottom of the tank. The ultrasonic pulser / receiver Synchronized at the time of HIFU signal generation, a short pulse was delivered to the 3.5 MHz single-element ultrasonic transducer. The signal received through the ultrasonic transducer was sampled at 100 MHz using a high-speed digitizer and stored in internal memory. After data acquisition, it was transferred to PC and necessary signal processing was performed using MATLAB. The phantom used in the experiment was prepared using agar and glass beads having an average diameter of 25 μm.

In order to show that the HIFU interference cancellation method according to the present invention is not limited to the HIFU utilization rate, the experiment was performed while varying the utilization rate to 10%, 30%, 50%, 70%, and 90%. Same as FIG. 7. Ultrasound imaging system, curver linear transducer, and bovine serum albumin gel phantom were used instead of single-element ultrasonic transducer and ultrasonic pulser / receiver to obtain monitor images of lesion formation. Phantom was prepared by incorporating BSA and scatterer agar into polyacrylamide at concentrations of 5% and 0.4% in w / v, respectively, and then hardening it into gel. In order to use the pulse reversal, the ultrasonic imaging system as well as the HIFU must transmit ultrasonic waves twice at the same point, so the pulse transmission and reception process was modified using the Texo software development kit (SDK). At the time of HIFU transmission, the ultrasound imaging system was synchronized to generate the scan line, and the received beam focused signal was stored in the system internal memory, and then transmitted to a PC for signal processing on MATLAB.

Referring to FIG. 8, a time waveform and a frequency spectrum of a reference signal obtained by transceiving a phantom with a single element ultrasonic transducer are shown.

Large echo signals near 60 μs and 240 μs are reflected from the top and bottom surfaces of the phantom, respectively. The manufactured phantom is about 14 cm high and is composed of two layers, as shown in FIG. The second layer increases the concentration of the scatterers by about 10%, increasing the attenuation coefficient there, suppressing strong signals reflected from the bottom.

When a large amplitude HIFU is transmitted for lesion formation, as shown in FIG. 10 due to the HIFU signal and its harmonic signal, a relatively small amplitude video signal may interfere with the image to obscure the HIFU signal. . As a result of applying pulse inversion to detect an image signal from the received signal, as shown in FIG. 11, it can be seen that the fundamental frequency and the third and fifth harmonics of HIFU disappeared. Thereafter, the remaining second and fourth harmonic signals are removed as shown in FIG. 12 using a band pass filter.

To evaluate the performance of the method according to the invention, the signal from which the HIFU interference has been removed is compared with a reference signal. As can be seen in Figure 12, the signal obtained using the method according to the present invention is the low-frequency and high-frequency components are removed by the band pass filter to limit the bandwidth of the signal. As a result, as shown in FIG. 13 (a), the energy of the entire signal was decreased, thereby reducing the amplitude of the signal.

In order to evaluate the degree to which the HIFU signal is removed using the HIFU interference cancellation method according to the present invention, a band pass filter is applied to a reference signal, and then compared with an image signal obtained through the proposed method. As a result, as shown in Figure 13 (b), since the two signals are very similar it can be determined that the interference signal by the HIFU has been removed. Also, to evaluate quantitatively, Equation 8 was used to obtain correlation coefficients between the image signal and the reference signal after the HIFU interference was removed, and then the maximum values were compared. The maximum value of the correlation coefficient increased significantly from 0.0685 to 0.9838 after HIFU interference was removed. This means that the HIFU interference cancellation method according to the present invention effectively removes the HIFU interference signal.

Equation 7

14 is a photograph of a phantom including lesions according to HIFU usage.

Referring to Figure 14, it shows that the HIFU lesion formed according to the HIFU utilization. It can be seen that when the utilization rate is 30% or less, the applied energy is small and no lesion is formed.

15 to 19 are obtained by applying a reference image obtained when the HIFU utilization rate is 10%, 30%, 50%, 70% and 90%, interference image by HIFU, image to which pulse inversion is applied, and band pass filter, respectively. Show an image. It can be confirmed that the monitor image can be obtained by removing the HIFU interference using the proposed method through each image.

Referring to the image to which the BPF is applied in FIG. 15, it can be seen that the echo around the HIFU focus area is increased compared to the reference image. This is believed to be due to the increased echo of the ultrasound image signal by the microbubbles formed by the HIFU, which may be used to confirm that the energy of the HIFU is being delivered where desired during treatment.

However, when the utilization rate is 70% and 90%, it can be seen that HIFU interference remains in front of the final image. This is a phenomenon that appears because the signal reflected from the ultrasonic flaw present in the bottom of the phantom is not removed by the proposed method, which can be explained with reference to FIG.

As shown in FIG. 20 (a), when the length of the HIFU pulse is short, even the signal reflected from the farthest point is received within the corresponding pulse repetition interval (PRI), so that no interference between PRIs occurs. As a result, the effect of pulse inversion can be obtained by adding the HIFU received signal with phase 0 ° and the HIFU received signal with phase 180 °.

However, when the length of the pulse becomes more than 50% of the PRI as shown in FIG. 20 (b), interference between the PRI of the HIFU signal occurs. The HIFU signal with interference between PRIs cannot be eliminated by pulse inversion because the signal with a phase difference of 180 ° is not present in the same PRI and appears in the image. For this reason, the method shown in FIG. 21 is used to remove the remaining HIFU interference signal.

First, the HIFU signals of phase 0 ° and 180 ° are transmitted and received, and then the HIFU signals of phase 0 ° are transmitted and received again. In addition, the HIFU signal having a phase of 180 ° is also subjected to PRI interference, so the effect of pulse inversion can be obtained by adding the second and third transmitted and received signals.

As shown in FIG. 22, even when the HIFU utilization rate is 90%, all HIFU interference may be removed and a monitor image may be obtained. Existing methods have limited HIFU usage to obtain monitor images, while the proposed method has the advantage of shortening the treatment time since it is theoretically possible to use 100% usage.

Referring to FIG. 23, the HIFU interference canceling method according to the present exemplary embodiment includes steps that are processed in time series in the HIFU interference canceling apparatus illustrated in FIG. 1. Therefore, even if omitted below, the above descriptions regarding the HIFU interference cancellation apparatus shown in FIG. 1 also apply to the HIFU interference cancellation method according to the present embodiment.

In step 2300, the HIFU interference canceling device transmits an image ultrasonic signal while transmitting at least two or more HIFU signals to be out of phase with each other.

In this case, the center frequency of the image ultrasound signal is preferably one of an odd harmonic frequency or an even harmonic frequency of the HIFU signal.

In particular, while transmitting two HIFU signals 180 degrees out of phase, the image ultrasound signal can be transmitted. Furthermore, the image ultrasonic signal may be transmitted while transmitting the HIFU signal having a phase of 0 degrees, the HIFU signal having a phase of 180 degrees, and the HIFU signal having a phase of 0 degrees.

In operation 2310, when at least two HIFU signals and the image ultrasound signal are reflected from the object, the HIFU interference cancellation apparatus receives an ultrasound signal including the reflected HIFU signal and the image ultrasound signal.

In operation 2320, the HIFU interference canceling apparatus may add the received ultrasonic signals to remove the fundamental frequency component and the harmonic frequency components of the HIFU signal included in the received ultrasonic signal.

At this time, it is preferable to remove the fundamental frequency component and the odd harmonic frequency component of the HIFU signal included in the received ultrasonic signal by summing the received ultrasonic signals.

In step 2330, the HIFU interference cancellation apparatus passes the received ultrasonic signal through a band cut filter or a band pass filter.

By passing the received ultrasonic signal through a band cut filter or a notch filter, one or more of even-numbered harmonic frequency components of the HIFU signal included in the received ultrasonic signal may be removed, and the received ultrasonic signal is converted into the image ultrasonic wave. The image ultrasonic signal may be selected by passing a band pass filter having a frequency band of the signal as a bandwidth.

In step 2340, the HIFU interference cancellation apparatus generates a B mode image from the ultrasound signal from which the fundamental frequency component and the harmonic frequency component are removed.

As described above, according to the present invention, since the signal for acquiring the monitor image is transmitted simultaneously with the HIFU signal, the process of lesion formation can be observed in real time by removing the HIFU interference. In addition, an increase in echo due to the formation of lesions in the HIFU focal region can be observed over time.

The method for setting the center frequency of the ultrasonic signal according to an embodiment of the present invention can be implemented by the following steps 2410 to 2440.

In step 2410, the HIFU signal is transmitted and received twice so that there is a 180 degree phase difference.

More specifically, the HIFU signal is transmitted and the HIFU signal is transmitted once more so that there is a 180 degree phase difference. The beam is focused through the beamformer and the HIFU signal is transmitted to the target to be treated through the HIFU treatment transducer. Thereafter, the HIFU signal having a phase difference of 180 degrees with the transmitted HIFU signal is once again transmitted. In addition, an echo of the transmitted HIFU signal is received. The received signal has two signals having a 180 degree phase difference, and the two signals are received through the image transducer.

Step 2420 is a step of removing the fundamental frequency components and odd-numbered harmonic frequency components of the HIFU signal by summing the two received HIFU signals.

More specifically, the HIFU signals received in step 2410 are added up. By summing up HIFU signals that are 180 degrees apart, the fundamental and odd harmonic frequency components of the HIFU signal are removed. The signals containing the two types of HIFU signal components are summed. Summing up the signals removes the fundamental frequency components and odd-numbered harmonic frequency components of the HIFU signal. When the received signal is stored and the signal of the next frame is received, the previous frame signal and the newly received signal are summed. The two signals include HIFU signal components having a 180 degree phase difference from each other, and by adding the two signals, the fundamental frequency component and the odd harmonic frequency component of the HIFU signal are removed.

In operation 2430, one of the odd-numbered harmonic frequencies of the removed HIFU signal is set as the center frequency of the ultrasound image signal.

More specifically, one of the odd harmonic frequencies of the HIFU signal removed in step 2410 is set as the center frequency of the image ultrasonic signal. The odd-numbered harmonic frequency component of the HIFU signal is removed by the method of steps 2410 to 2420, and the odd-numbered harmonic frequency of the removed HIFU signal is used as the center frequency of the image ultrasonic signal, thereby being used for the image ultrasonic signal. Bandwidth can be obtained. Accordingly, one of the odd harmonic frequencies of the HIFU signal is set as the center frequency of the image ultrasonic signal so that the bandwidth can be used for the image ultrasonic signal. The first harmonic frequency may be set as the center frequency of the image ultrasonic signal, or the other odd harmonic frequency may be set as the center frequency of the image ultrasonic signal. The most efficient odd-numbered harmonic frequency may be set as the center frequency of the image ultrasonic signal in consideration of the frequency of the transmittable image ultrasonic wave of the apparatus for transmitting the image ultrasonic signal. The frequency with the least interference from HIFU can be used as the center frequency of the ultrasonic signal. That is, a frequency having the highest intensity may be used within the frequency of the transmittable image ultrasonic wave of the apparatus for transmitting the image ultrasonic signal. By setting the center frequency of the image ultrasonic signal as described above, it is possible to minimize the interference of the HIFU signal, and to know the waveform of the accurate image ultrasonic signal, it is possible to obtain a good image quality image.

HIFU interference cancellation apparatus according to another embodiment of the present invention is composed of a HIFU signal transmitter 2401, an image ultrasonic signal transmitter 2402, an ultrasonic signal receiver 2403, and a signal difference calculator 2410, ultrasonic image The processor 2420 may be further included.

The HIFU signal transmitter 2401 transmits a HIFU signal.

More specifically, the HIFU signal is transmitted without phase difference toward the object. The HIFU signal transmitter 2401 has the same configuration as the HIFU signal transmitter 101 of FIG. 1 except for the configuration of transmitting the HIFU signal without phase difference, and the description of the other components is described with respect to the HIFU signal transmitter 101 of FIG. 1. Instead of

The image ultrasonic signal transmitter 2402 transmits the image ultrasonic signal for transmitting the two image ultrasonic signals to have a 180 degree phase difference.

More specifically, two projection ultrasound signals are transmitted to have a 180 degree phase difference using an inverted pulse technique. Except for the configuration of transmitting two image ultrasonic signals to have a 180 degree phase difference, the configuration is the same as that of the image ultrasonic signal transmitter 102 of FIG. 1, and the description of the other components will be described with reference to the image ultrasonic signal transmitter 102 of FIG. 1. Replace with description.

When the HIFU signal and the image ultrasound signal are reflected from the object, the ultrasound signal receiver 2403 receives an ultrasound signal including the reflected HIFU signal and the image ultrasound signal.

More specifically, the HIFU signal transmitter 2401 and the image ultrasonic signal transmitter 2402 transmit an ultrasonic signal including the reflected HIFU signal and the image ultrasonic signal. A detailed description of the ultrasonic signal receiver 2403 is the same as that of the ultrasonic signal transmitter 103 of FIG. 1, and a description of another configuration is replaced with the description of the ultrasonic signal transmitter 103 of FIG. 1.

The signal difference calculator 2401 calculates a difference between the received ultrasound signals and removes a fundamental frequency component and a harmonic frequency component of the HIFU signal included in the received ultrasound signal.

More specifically, the ultrasonic signals received by the ultrasonic signal receiver 2403 are two kinds of signals. The HIFU signal included in both types of signals is the same type. The image ultrasonic signal is a reflection of the image ultrasonic signal transmitted by the image ultrasonic signal transmitter 2402 so that the phase difference is 180 degrees. The two types of image ultrasonic signals have a phase difference of 180 degrees. The difference between the two types of ultrasonic signals is calculated. When the difference between the two types of ultrasonic signals is calculated, the HIFU signal portion has the same phase and the same magnitude and is removed, and the image ultrasonic signal portion having the 180 degree phase difference has twice the size. As such, by calculating the difference between the received ultrasonic signals, the fundamental frequency component and the harmonic frequency component of the HIFU signal included in the received ultrasonic signal may be removed. As such, by calculating the difference between the two types of ultrasonic signals, it is possible to remove both the fundamental frequency component and the harmonic frequency component of the HIFU signal without a separate band pass filter. As a result, there is an effect that axial resolution can be preserved.

In step 2500, the HIFU signal is transmitted while transmitting two image ultrasound signals to be 180 degrees out of phase.

More specifically, the HIFU signal is transmitted without phase difference, and the image ultrasound signal is transmitted twice so as to have a 180 degree phase difference. The pulse inversion technique is used to make the image ultrasonic signal 180 degrees out of phase. The detailed description of this step corresponds to the detailed description of the HIFU signal transmitter 2401 and the image ultrasonic signal transmitter 2402 of FIG. 24, and the HIFU signal transmitter 2401 and the image ultrasonic signal transmitter 2402 of FIG. 24. Replace with the detailed description of.

In operation 2510, when the image ultrasound signal and the HIFU signal are reflected from the object, an ultrasound signal including the reflected image ultrasound signal and the HIFU signal is received.

In operation 2520, the difference between the received ultrasonic signals is calculated to remove the fundamental frequency component and the harmonic frequency components of the HIFU signal included in the received ultrasonic signal.

Since the ultrasound signal received in step 2510 has a 180 degree phase difference between the image ultrasound signals transmitted in step 2500, there is a part corresponding to the same HIFU signal and a part corresponding to the image ultrasound signal having a 180 degree phase difference. Accordingly, when the difference between the two types of ultrasonic signals is calculated, the fundamental frequency component and the harmonic frequency component of the HIFU signal corresponding to the HIFU signal may be removed. The detailed description of this step corresponds to the detailed description of the signal difference calculator 2401 of FIG. 24, and is replaced with the detailed description of the signal difference calculator 2401 of FIG. 24.

In step 2530, the HIFU interference canceling device generates a B mode image from the ultrasonic signal from which the fundamental frequency component and the harmonic frequency component are removed.

The two kinds of ultrasonic signals received by the ultrasonic signal receiver 2403 have the same portion corresponding to the HIFU signal, and the portions corresponding to the image ultrasonic signals have a 180 degree phase difference. The difference between the two ultrasonic signals is calculated to remove the fundamental frequency component and the harmonic frequency component of the HIFU signal corresponding to the HIFU signal.

(a) is before the HIFU interference signal is removed, and (b) is after the HIFU interference signal is removed. By removing the HIFU interference signal, an ultrasound image may be generated, and through this, ultrasound image diagnosis may be performed.

Embodiments of the present invention can be implemented in the form of program instructions that can be executed by various computer means and recorded in a computer readable medium. The computer readable medium may include program instructions, data files, data structures, etc. alone or in combination. Program instructions recorded on the media may be those specially designed and constructed for the purposes of the present invention, or they may be of the kind well-known and available to those having skill in the computer software arts. Examples of computer readable recording media include magnetic media such as hard disks, floppy disks and magnetic tape, optical media such as CD-ROMs, DVDs, and magnetic disks such as floppy disks. Magneto-optical media, and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like. The hardware device described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

Although the present invention has been described above with reference to the embodiments, it will be understood by those skilled in the art that various modifications and changes of the present invention can be made without departing from the spirit and scope of the present invention. I can understand. Therefore, the present invention is not limited to the above-described embodiment, and the present invention will include all embodiments within the scope of the following claims.

Since the embodiments of the present invention use a pulse reversal technique, the HIFU interference is eliminated regardless of the length of the HIFU to obtain a monitor image, and the HIFU interference is transmitted because a signal for acquiring the monitor image is transmitted simultaneously with the HIFU signal. By removing, the process of lesion formation can be observed in real time, and the treatment site is monitored using real-time images to confirm the formation of the lesion at the desired position, the progress of treatment, and to observe and compensate for the movements occurring during the treatment. can do.

Claims

Transmitting at least two HIFU signals, the image ultrasonic signals being out of phase with each other;

If the at least two HIFU signals and the image ultrasound signal are reflected from an object, receiving an ultrasound signal including the reflected HIFU signal and the image ultrasound signal; And

Summing the received ultrasonic signals to remove a fundamental frequency component and a harmonic frequency component of the HIFU signal included in the received ultrasonic signal.
The method of claim 1,

And a center frequency of the image ultrasonic signal is any one of an odd harmonic frequency and an even harmonic frequency of the HIFU signal.
The method of claim 1,

The transmitting of the image ultrasound signal may include:

And transmitting the image ultrasound signal while transmitting two HIFU signals with a 180 degree phase difference.
The method of claim 3, wherein

Removing the fundamental frequency component and the harmonic frequency component of the HIFU signal included in the received ultrasonic signal,

Summing the received ultrasonic signals to remove the fundamental frequency components and odd-numbered harmonic frequency components of the HIFU signal included in the received ultrasonic signals.
The method of claim 3, wherein

The transmitting of the image ultrasound signal may include:

And transmitting an image ultrasonic signal while transmitting a HIFU signal having a phase of 0 degrees, a HIFU signal having a phase of 180 degrees, and a HIFU signal having a phase of 0 degrees.
The method of claim 3, wherein

And removing one or more of even-numbered harmonic frequency components of the HIFU signal included in the received ultrasonic signal by passing the received ultrasonic signal through a band cut filter or a notch filter.
The method of claim 3, wherein

And selecting the video ultrasound signal by passing the received ultrasound signal through a band pass filter having a frequency band of the video ultrasound signal as a bandwidth.
The method of claim 1,

And generating a B mode image from the ultrasonic signal from which the fundamental frequency component and the harmonic frequency component have been removed.
The method of claim 1,

The HIFU signal and the image ultrasound signal are synchronized with the ultrasound image frame,

The synchronization using the ultrasound image frame is HIFU interference cancellation method characterized in that for transmitting and receiving the image ultrasound signal and a HIFU signal 180 degrees out of phase with the HIFU signal of the previous frame in one frame.
The method of claim 1,

The HIFU signal and the image ultrasound signal are synchronized with the scan line of the ultrasound image,

Synchronization using the scan line, HIFU interference cancellation method characterized in that for transmitting and receiving the image ultrasound signal of any one image scan line and the HIFU signal 180 degrees out of phase with the HIFU signal of the previous scan line.
The method of claim 1,

And the HIFU signal is a nonlinear chirp signal.
The method of claim 1,

The image ultrasonic signal may be any one of a short pulse, a barker code, a golay code, and a chirp code.
Transmitting and receiving the HIFU signal twice so as to have a 180 degree phase difference;

Removing the fundamental frequency component and the odd harmonic frequency component of the HIFU signal by summing the two received HIFU signals; And

And setting one of odd-numbered harmonic frequencies of the removed HIFU signal as a center frequency of the image ultrasonic signal.
Transmitting a HIFU signal while transmitting two image ultrasound signals with a 180 degree phase difference;

If the image ultrasound signal and the HIFU signal are reflected from an object, receiving an ultrasound signal including the reflected image ultrasound signal and a HIFU signal; And

Calculating a difference between the received ultrasonic signals and removing a fundamental frequency component and a harmonic frequency component of the HIFU signal included in the received ultrasonic signal.
A non-transitory computer-readable recording medium having recorded thereon a program for executing the method of claim 1.
A HIFU signal transmitter for transmitting at least two or more HIFU signals to be out of phase with each other;

An image ultrasonic signal transmitter for transmitting an image ultrasonic signal;

An ultrasound signal receiver configured to receive an ultrasound signal including the reflected HIFU signal and the image ultrasound signal when the at least two HIFU signals and the image ultrasound signal are reflected from an object; And

And a signal adder configured to add the received ultrasonic signals to remove fundamental frequency components and harmonic frequency components of the HIFU signal included in the received ultrasonic signals.
The method of claim 16,

And a center frequency of the image ultrasound signal is any one of an odd harmonic frequency and an even harmonic frequency of the HIFU signal.
The method of claim 16,

The HIFU signal transmitting unit HIFU interference removing device, characterized in that for transmitting two HIFU signal 180 degrees out of phase.
The method of claim 18,

The signal summing unit

And summing the received ultrasonic signals to remove fundamental frequency components and odd-numbered harmonic frequency components of the HIFU signal included in the received ultrasonic signals.
The method of claim 18,

When the HIFU signal transmitter transmits a HIFU signal having a phase of 0 degrees, a HIFU signal having a phase of 180 degrees, and a HIFU signal having a phase of 0 degrees, the image ultrasonic signal transmitter transmits an image ultrasonic signal. Removal device.
The method of claim 16,

And an ultrasonic image processing unit for generating a B-mode image from the ultrasonic signal.
A HIFU signal transmitter for transmitting a HIFU signal;

An image ultrasound signal transmitter configured to transmit an image ultrasound signal that transmits two image ultrasound signals to be 180 degrees out of phase;

An ultrasound signal receiver configured to receive an ultrasound signal including the reflected HIFU signal and an image ultrasound signal when the HIFU signal and the image ultrasound signal are reflected from an object; And

And a signal difference calculator configured to calculate a difference between the received ultrasonic signals and remove a fundamental frequency component and a harmonic frequency component of the HIFU signal included in the received ultrasonic signal.