Method and system for rapidly eliminating steam effect in tumor ablation

Abstract

The invention discloses a method and a system for quickly eliminating a steam effect in tumor ablation, and belongs to the field of tumor ablation. According to the method, steam microbubbles generated in the radio frequency or microwave ablation process are eliminated, so that the time needed for waiting for natural dissipation of the steam microbubble cloud after ablation is shortened, a special ultrasonic wave waveform sequence is created during ablation and / or after ablation, the special waveform sequence is emitted to the position where the steam cloud is located, and the steam microbubbles generated in the radio frequency or microwave ablation process are eliminated. The special waveform has a negative-phase sparse section with prolonged time, so that bubbles are more easily scattered. According to the system, a special user interface is provided, a user is allowed to locate the focus position of a special waveform sequence to the steam cloud, the steam cloud effect is rapidly eliminated, and therefore the purpose of rapidly evaluating the tumor ablation effect is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of tumor ablation, and more specifically, relates to a method and system for rapidly eliminating steam effect in tumor ablation. Background Art

[0002] In minimally invasive treatment, the radiofrequency or microwave tumor ablation process is always associated with the steam burst phenomenon, which produces a steam cloud filled with steam microbubbles, causing strong ultrasonic echoes under ultrasound imaging conditions. Because the steam microbubble cloud reflects most of the ultrasonic waves back to the direction of the ultrasound probe, the ultrasonic waves cannot reach the steam microbubble cloud, forming a steam cloud shadow area, and the tissue in the shadow area cannot generate tissue echoes. In addition, because the steam microbubbles echo too strongly under ultrasound, the detailed information of the tumor site covered by them cannot be observed and is often missed. Doctors need to wait 10-15 minutes for the steam microbubbles to dissipate before observing the tissue ablation at the ablation site and observing the tissue under the steam bubbles again under ultrasound. This is a serious problem because doctors often want to quickly evaluate the efficacy of the ablation effect and quickly start the next patient. At the end of the operation, doctors generally use the ablation function to close the needle insertion entrance, and thus generate a large number of steam microbubbles to fill the entire needle insertion channel. This also produces a strong shielding effect, making it impossible to clearly observe the tissue under the entire needle channel with ultrasound. As mentioned above, echogenic steam clouds and hyperechoic needle paths are common around tumors during radiofrequency or microwave ablation of tumors. The echogenic shadows they create block information about the underlying tissue that can be seen with ultrasound. Worse still, studies have shown that steam pops may be associated with tumor recurrence.

[0003] There needs to be a way to quickly eliminate the steam microbubbles in the tumor site and the steam diffusion area so that doctors can quickly restore normal ultrasound imaging capabilities for the ablated tissue. This can help doctors avoid shadows under the strong echoes of the steam cloud and normal tissue covered by strong echoes. Currently, it usually takes 10-15 minutes for the steam microbubbles produced by ablation to dissolve naturally. 10-15 minutes is an important time because most liver tumors are ablated below 3cm, so the ablation process usually takes less than 5 minutes. Too much time is wasted waiting after ablation. Summary of the invention

[0004] 1. Problem to be solved

[0005] In view of the problem that the prior art cannot quickly restore the normal ultrasonic imaging capability of the ablated tissue, the present invention provides a method and system for quickly eliminating the steam effect in tumor ablation.

[0006] 2. Technical solution

[0007] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0008] A method for quickly eliminating the steam effect in tumor ablation of the present invention designs an ultrasound transmission waveform sequence with multiple pulse cycles, wherein the ultrasound transmission waveform sequence is composed of one or more basic transmission waveforms, and the one or more basic transmission waveforms have at least one extended half-cycle negative pressure pulse; and the ultrasound transmission waveform sequence is transmitted into a steam cloud formed by steam microbubbles generated during microwave and radio frequency ablation to quickly disperse the steam cloud.

[0009] Preferably, the basic transmission waveform is composed of 1.5 to more normal waveforms plus a negative pressure pulse with a prolonged negative half cycle.

[0010] Preferably, the ultrasound transmission waveform sequence includes one or more basic transmission waveforms, which are composed of multiple repetitions of the basic transmission waveform.

[0011] Preferably, the length of the extended negative half cycle in the basic transmission waveform is an integer or non-integer multiple of the negative half cycle of the normal waveform.

[0012] The present invention provides an ultrasound imaging system with a steam removal function, which includes a waveform generator capable of generating a special ultrasound transmission waveform having at least one extended half-cycle negative pressure pulse; and a user interface to allow a user to set the transmission focus of the special ultrasound transmission waveform at the center of the steam cloud generated by ablation through a mouse, and the user can manually or automatically turn on and off the function of eliminating the steam cloud using the special ultrasound transmission waveform.

[0013] Preferably, after the user locates the emission focus of the special emission waveform, the user adjusts the size of a rectangular area centered on the focus, and the system will emit a special ultrasonic emission waveform in the rectangular area to disperse the steam cloud according to the user's on or off instructions.

[0014] Preferably, after the user locates the focus of the special transmission waveform, the system allows the user to directly turn on the steam cloud removal function to transmit a special ultrasonic transmission waveform at the focus position to disperse the steam cloud.

[0015] 3. Beneficial effects

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) A method of the present invention for rapidly eliminating the steam effect in tumor ablation, eliminating steam microbubbles generated during radiofrequency or microwave ablation, thereby reducing the time required to wait for the steam microbubble cloud to naturally dissipate after ablation. The method creates a special ultrasound waveform sequence during and / or after ablation, and transmits the special waveform sequence to the tissue ablation site covered by the steam cloud to tear the steam microbubbles and eliminate the steam cloud diffused at the ablation site and the surrounding area;

[0018] (2) A system for rapidly eliminating the steam effect in tumor ablation of the present invention includes an ultrasonic imaging system that implements the method of the present invention. The system provides a proprietary user interface that automatically allows the user to enter this special steam cloud removal mode. The user can select the location where the steam cloud should be removed, so that the system can transmit a special ultrasonic waveform sequence to the location and start the steam cloud removal operation. After eliminating the steam effect, the user can exit this special mode and resume normal imaging;

[0019] (3) The system of the present invention can quickly eliminate the steam effect during tumor ablation, and can eliminate the steam cloud in less than a few minutes, which is significantly shorter than the 10-15 minutes that doctors have to wait for the steam to dissipate during current radiofrequency or microwave ablation procedures. The steam elimination function can also be used in real time during the ablation process to better monitor the ablation process, helping clinicians to understand the ablation effect more quickly and accurately, and is expected to achieve huge clinical benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of a special waveform sequence for vapor cloud microbubble elimination;

[0021] Figure 2 a is the state of microbubbles under the action of normal ultrasonic pulse sequence;

[0022] Figure 2 b is the state of microbubbles under the action of special ultrasonic waveform pulse sequence;

[0023] Figure 3 ac is a special basic waveform of a special waveform sequence;

[0024] Figure 4 Schematic diagram of pulse sequence construction based on basic waveform;

[0025] Figure 5 Schematic diagram of a special waveform sequence transmitted at 100Hz PRF;

[0026] Figure 6 Ultrasonic imaging system designed specifically for eliminating steam cloud microbubbles;

[0027] Figure 7 a is a user interface of an intervention page for selecting a steam cloud clearing function;

[0028] Figure 7 b is a special waveform pulse sequence formed by repeating the basic special waveform twice;

[0029] Figure 7 c is a special waveform pulse sequence formed by repeating the basic special waveform three times;

[0030] Figure 7d is a special waveform pulse sequence formed by repeating the basic special waveform four times;

[0031] Figure 8 Schematic diagram of the area selected for vapor cloud removal;

[0032] Fig. 9 Schematic diagram of the spatial arrangement of the acoustic beams transmitting special waveforms for the steam cloud clearance area;

[0033] Fig.10 Schematic diagram of the time series of ultrasonic waveform emission in the steam cloud clearing function;

[0034] Fig.11 The overall process for removing the vapor cloud through the vapor cloud removal function;

[0035] Fig.12 A schematic flow chart of another method for dispersing steam microbubbles using a special waveform sequence. DETAILED DESCRIPTION

[0036] The present invention is further described below in conjunction with specific embodiments.

[0037] The present invention generates special emission waveforms and waveform sequences to eliminate steam microbubbles generated by steam bursting during radio frequency or microwave ablation. Steam bursting caused by rapid steam expansion during ablation causes a large number of tiny steam bubbles to cover the ablation area. These steam bubbles gather together to form a dense steam cloud that makes it impossible for imaging ultrasound to penetrate, resulting in an ultrasound shadow area that cannot be observed in the ablation area. To disperse these large numbers of tiny steam bubbles, the key is to break up these steam bubbles and decompose them into smaller microbubbles so that they can be quickly absorbed and dissolved by the surrounding tissues. Since bubbles are more fragile in the negative pressure expansion stage than in the positive pressure compression stage, the waveform generated by the method has a longer negative pressure rarefaction time, so that the steam bubbles can be easily torn apart.

[0038] like Figure 1 As shown, a method of the present invention for rapidly eliminating the steam effect in tumor ablation is achieved by designing a special waveform. Figure 1 A special waveform sequence 100 designed to destroy vapor bubbles is shown. In this special waveform sequence 100, the Figure 1The basic waveform 101 shown by the dotted line is composed of a normal waveform 102 and an extended negative pressure pulse 103. The special basic waveform is repeated many times to form a special waveform sequence 100. Here, the waveform 102 is a normal 1.5 cycle sine wave, and the negative pressure pulse 103 is an extended negative pressure half cycle pulse. The length of the negative pressure pulse is twice the negative half cycle of the normal waveform 102. The purpose of the extended negative pressure pulse 103 is to form a long negative pressure expansion phase so that the steam bubble cannot maintain the surface tension and breaks into small pieces. In the pulse sequence 100, every 2 normal waveform cycles contain a negative pressure expansion half cycle pulse 103 with an extended time, which makes the bubble expand more under the action of ultrasonic waves. Figure 2 ab compares the response of microbubbles to normal ultrasound sequences and special ultrasound sequences. Figure 2 In a, when a normal ultrasonic pulse sequence 200 acts on a steam bubble, the positive pressure compression stage 201 is shown as the upper half cycle indicated by the diagonal line, compressing the bubble to the minimum size shown by 203, corresponding to the maximum pressure that the pulse can reach. Figure 2 The negative pressure expansion half cycle 202 in a is filled with a grid, which can expand the steam bubble to a larger size by negative pressure, such as Figure 2 As shown in 204 in a. This is a normal situation.

[0039] Figure 2 b illustrates the case where a special waveform sequence 300 similar to the waveform sequence 100 described above is applied to steam bubbles. It can be seen that under the action of the positive pressure half-cycle pulse 301 in the diagonal strip filling area, the bubble is compressed into a smaller size 304. In the normal negative pressure rarefaction expansion stage 302, as shown in FIG. Figure 2 The grid shown in b is filled with negative half-cycle pulses, and the bubble expands to size 305. Assuming similar bubbles and waveforms, the bubbles of size 304 and size 305 are Figure 2 The size of 203 and 204 of a is the same. When the waveform is in the negative pressure extended pulse region 303 filled with vertical bars, the bubble can reach a larger expanded size 306.

[0040] Since the special waveform can be repeated many times to form a pulse sequence, the bubbles can be easily broken up into smaller bubbles or dissolved, and then the vapor cloud will disappear and ultrasound imaging will restore the ability to image tissues.

[0041] There are three methods for constructing the special waveform sequence in the present invention. One method is to adjust the basic special waveform. For example, the basic special waveform can have different numbers of normal wave pulses. Figure 3 a shows the Figure 1 The basic waveform 101 extracted from the waveform 102 has a normal pulse portion of 1.5 cycles. In the basic special waveform, the number of cycles of the normal waveform can be different, such as Figure 3b waveform 400, wherein the normal waveform 401 represented by the dotted line has 2.5 cycles, Figure 3 c waveform 410, wherein the normal waveform 411 represented by the dotted line has 3.5 cycles. Figure 3 In ac, the elongated negative pressure half-cycle pulses 103, 403 and 413 are only half cycles, and the area covered by these negative pressure half-cycle pulses is twice the area covered by the normal negative pressure half-cycle. Of course, this negative pressure half-cycle can also be other multiples of the normal negative pressure half-cycle, such as 3 times, 4 times, 1.5 times, etc. It should be noted that the basic waveform shown here is only an example, it can be a normal waveform with 2 cycles or 3 cycles, or other formats of forming waveforms.

[0042] Another method for waveform sequence construction is to adjust the number of repetitions of the basic waveform 101, 400 or 410 in the sequence. In order to improve the ability to dissipate steam, a special waveform can be repeated multiple times to form a long pulse sequence, such as Figure 1 As shown. Further, Figure 4 As shown, Figure 3 The basic special waveform 410 in b is repeated 4 times to form a long pulse train 500.

[0043] A third method of special waveform sequence construction is to control the pulse repetition frequency (PRF) of the waveform sequence. For example, at a user selected transmit focus position, the PRF can be varied from 10 Hz to 10 kHz. Figure 5 An example is given in which a special waveform sequence 600 is sent to tissue at a specific location at intervals of every 10 ms, so the PRF is at 100 Hz.

[0044] In order to be able to generate, control and transmit special waveform pulse sequences into the human body, the present invention proposes a specially designed ultrasound imaging system 700. In this special imaging system 700, there is a new component 701, namely a special waveform sequence generator, which generates special waveform pulse sequences, such as the above-mentioned sequences 100, 200, 300, 500 and 600. The generated special waveform sequence is then sent to the transmit wave forming component 702, where the actual waveform is created. In the transmit beamformer 703, the waveform generated on each signal channel is delayed accordingly according to the selected transmit focus position, and then sent to the transmit pulser 704 to form a real electronic waveform. The waveform then passes through the transmit / receive (T / R) switch 705 and is sent to the ultrasound sensor, i.e., the probe 710, which is converted into mechanical vibrations by the ultrasound probe and transmitted into the human body. The tissue echo received by the ultrasound probe is converted into electronic waves. It passes through the T / R switch 705 again, and then is amplified by the analog front-end amplifier 706, converted into a digital signal by the A / D converter 707, and then the dynamic receive beamforming function module 708, where the signals received from all signal channels are formed into radio frequency (RF) data by the beamforming module 708 through delay accumulation, and then sent to the receive intermediate processing block 709 for demodulation, filtering, threshold and other processing. The processed data passes through the receive post-processing block 710, in which the intermediate processed data is further envelope detected, edge enhanced, and becomes a b-mode black and white tissue image or becomes a blood flow signal after phase information extraction, and then sent to the display unit 711 for final display. However, it must be pointed out that the ultrasound echo of the special waveform sequence generated may not need to be displayed at all because its special pulse shape has no spatial resolution. The system control unit 712 controls all functional blocks, as well as the user interface functional block 718. The user interface allows the user to select the steam cloud elimination function and adjust the waveform, and further, allows the user to turn off this steam bubble elimination function at any time.

[0045] The ultrasonic imaging system of the present invention provides a user with an interface for implementing a vapor bubble removal function, also referred to herein as a vapor removal function, and a method for locating the emission focus of a special waveform pulse sequence at the location of a vapor cloud. As a detailed implementation, Figure 7 An explanation is given. Figure 7In a, a user interface is shown. During tumor ablation, the user can enter the intervention function page 800. On the intervention function page 800, the user can enable or disable the steam cloud elimination function by pressing the steam clear button 801, and then select one of the Easy802, Normal803, and Hard 804 buttons. Each of the Easy802, Normal803, and Hard 804 buttons corresponds to a different special waveform sequence. For example, the Easy 802 button corresponds to a special waveform sequence 812 in which the basic waveform 101 is repeated twice, the Normal 803 button corresponds to a special waveform sequence 813 consisting of the basic waveform 101 repeated three times, and the Hard 804 button corresponds to a special waveform sequence 814 consisting of the basic waveform 101 repeated 4 times, as shown in FIG. Figure 7 d. The longer the special waveform pulse sequence is, the stronger its ability to break up steam bubbles and eliminate steam effects is. After the user selects the desired steam cloud removal function, the system will allow the user to use the mouse to locate the center point of the steam bubble elimination pulse emission focus, such as Figure 8 Note that even though the Easy 802, Normal 803, and Hard 804 functions described here are associated with a particular waveform pulse train length, they can also be associated with a different transmit frequency of the basic waveform or the length of the basic waveform. Typically, the center frequency of the basic waveform should be within the ultrasound probe transducer bandwidth.

[0046] Figure 8 An example of selecting a steam cloud clearing area on an ultrasound imaging plane is shown. The ultrasound imaging plane 900 is an ultrasound cross-section of human liver tissue. In the upper left corner of the figure, there is a tumor 901, and an ablation needle 902 is inserted into the tumor 901 from the upper right corner. During the ablation process, microwave or radiofrequency ablation treatment generates a steam cloud 903 around the tip area of ​​the needle 902, which covers the tumor 901 and the underlying tissue. When the user enables the steam clearing function, the system allows the user to place a cursor 904 at the center of the steam cloud 903, and then the user can adjust the size of a rectangular frame 905 centered on the cursor 904. The rectangular area 905 is where the special waveform sequence is applied.

[0047] Fig. 9 It is shown how to apply the special waveform of vapor removal in the rectangular area 905. The invented imaging system will transmit multiple acoustic beams in the rectangular vapor removal area 905. For each acoustic beam, the transmission focus is designed as an ellipsoidal volume focus area 907, which can cover most of the depth range of the rectangular area 905. The number of special waveform acoustic beams used to fill the area in the horizontal direction is calculated as follows:

[0048] Number of sound beams = rectangle width / sound beam focal area width,

[0049] In this way, the specially shaped beam transmitted can cover the entire width of the rectangular area.

[0050] like Fig. 9 As shown, there are 10 beams to fill the width of the rectangular area 905. The transmission sequence can be the same as the normal ultrasound blood flow imaging beam transmission sequence, with a predefined PRF, such as Fig.10 As shown. Fig.10 In , 8 special waveform beams are assigned to fill the corresponding rectangular area selected by the user. The 8 special beams are repeatedly transmitted in a time-staggered manner. Fig.10 In the example, Shot 1, Shot 1', and Shot 1" are all fired at the same spatial location, as are other beams with the same value, such as Shot 3, Shot 3', and Shot 3". The time between Shot 1 and Shot 1' is 1 / PRF, where PRF is the user-defined transmit PRF. The PRF can also be set by Figure 7 The function buttons shown in a are used to select predefined values ​​such as easy 802, Normal 803, and hard 804. The user can override the default PRF values ​​by manually selecting the available PRF values ​​for each setting. The system transmits beams 1, 2, 3, ... from the left side to the right side of the rectangular area 905, then returns to the spatial position to transmit 1 again, and repeats the transmission sequence in space, transmitting 1', 2', ..., 8', and then returns again to transmit 1", 2", ..., 8". This process is repeated until the number of transmissions at each position reaches a predetermined value. As with CF imaging, conventional B-mode imaging and this steam removal mode can be interleaved like the B / CF imaging mode.

[0051] The user selects the correct steam removal mode, places the steam removal rectangular box at the location of the steam cloud, and the ultrasound imaging system will begin to transmit a special waveform pulse sequence. When the steam cloud is almost gone or no longer affects the normal monitoring of the tumor status, the user can stop the process. Fig.11 The overall sequence of this process 920 is given.

[0052] After the system begins imaging at 921, the user begins and completes a tumor ablation procedure 922, which produces a vapor cloud. The user then enters vapor purge mode at process 923 and moves a cursor to the center of the vapor cloud at process 924. After adjusting the rectangular vapor purge area to fit the size of the vapor cloud at process 925, the user can turn on the vapor purge function, sending a special waveform sequence to break up the vapor microbubbles produced at process 926. After the vapor cloud dissipates at process 927, the user can return to normal imaging mode.

[0053] Another way to implement the steam elimination function is to apply a special waveform sequence to only the sound beam located at the cursor position, such as Figure 8 In 904, the acoustic beam is emitted with a predefined PRF or a PRF dynamically defined by the user. The whole process is similar to the above Fig.11 The difference is that after the user places the cursor at the center of the steam cloud in process 924, there is no rectangular area to be adjusted as in the above process 925. Instead, the user will directly use the steam bubble elimination function to eliminate the cursor position such as Fig.12 The bubbles are depicted in process 928, where the entire process is defined as process 930. When the vapor bubbles at the location of the acoustic beam are cleared, the user can manually move the acoustic beam to another location to continue. Fig.12 The steam removal in step 929 shown in FIG. 1 will continue until the user determines that the steam cloud no longer obstructs the evaluation of the tumor ablation efficacy. The user will then turn off the steam removal function and return to the Fig.12 The normal imaging mode of process 927, with Fig.11 same.

[0054] Please note that in the above design, although the user is allowed to manually place the cursor at the location of the steam cloud and focus the special waveform sequence to eliminate the steam bubble, this process can be done automatically by artificial intelligence. The steam cloud can be automatically identified by artificial intelligence, and then the system places the special waveform sequence focus position to the location where the steam cloud is.

[0055] It is further noted that although the present invention describes a new basic waveform with an extended negative pressure expansion phase to eliminate bubbles, a normal waveform can also be selected as the basic waveform as long as a longer pulse sequence is formed to deliver sufficient energy where steam is eliminated.

[0056] The present invention and its implementation methods are described schematically above, and the description is not restrictive. The data used is only one of the implementation methods of the present invention, and the actual data combination is not limited thereto. Therefore, if a person skilled in the art is inspired by it and does not deviate from the purpose of the invention, the implementation methods and embodiments similar to the technical solution without creative design should all fall within the protection scope of the present invention.

Claims

1. A method for quickly eliminating the steam effect in tumor ablation, designing an ultrasound transmission waveform sequence with multiple pulse cycles, wherein the ultrasound transmission waveform sequence is composed of one or more basic transmission waveforms, and the one or more basic transmission waveforms have at least one extended half-cycle negative pressure pulse; and the ultrasound transmission waveform sequence is emitted into a steam cloud formed by steam microbubbles generated during microwave and radiofrequency ablation to quickly disperse the steam cloud.

2. A method for rapidly eliminating the steam effect in tumor ablation according to claim 1, characterized in that: The basic transmitting waveform is composed of 1.5 to more normal waveforms plus a negative pressure pulse with a negative half cycle extended.

3. A method for rapidly eliminating the steam effect in tumor ablation according to claim 1, characterized in that: The ultrasonic transmission waveform sequence includes one or more basic transmission waveforms, and the composition mode is that the basic transmission waveform is repeated multiple times.

4. A method for rapidly eliminating the steam effect in tumor ablation according to claim 2, characterized in that: The length of the extended negative half cycle in the basic transmission waveform is an integer or non-integer multiple of the negative half cycle of the normal waveform.

5. An ultrasonic imaging system with steam removal function, characterized in that: The system includes a waveform generator capable of generating a special ultrasonic transmission waveform having at least one extended half-cycle negative pressure pulse; and a user interface to allow a user to set the transmission focus of the special ultrasonic transmission waveform at the center of the steam cloud generated by ablation through a mouse, and the user can manually or automatically turn on and off the function of eliminating the steam cloud using the special ultrasonic transmission waveform.

6. The ultrasonic imaging system with steam removal function according to claim 5, characterized in that: After the user locates the emission focus of the special emission waveform, the user adjusts the size of a rectangular area centered on the focus. The system will emit a special ultrasonic emission waveform in the rectangular area to disperse the steam cloud according to the user's on or off instructions.

7. The ultrasonic imaging system with steam removal function according to claim 5, characterized in that: After the user locates the focus of the special transmission waveform, the system allows the user to directly turn on the steam cloud removal function to transmit a special ultrasonic transmission waveform at the focus position to disperse the steam cloud.

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