CN113398498B - An MRI-compatible flexible high-intensity focused ultrasound device - Google Patents

Abstract

The present invention provides an MRI-compatible flexible high-intensity focused ultrasound device and a method for using the same. The device includes a gridded flexible substrate, an ultrasonic piezoelectric wafer, a strap, a matching circuit, a power amplifier, a switch, and a signal generator. The ultrasonic piezoelectric chip is fixed in the grid of the flexible substrate; the ultrasonic piezoelectric chip is connected to the output port a of the matching circuit, and the input port b of the matching circuit is connected to the output end of the power amplifier; the output end of the switch is connected to the power amplifier. The input end of the amplifier is connected with each other, and the input end of the switch is connected with the input end of the signal generator and the single-chip microcomputer. The invention does not need to adjust the probe by mechanical means to adapt to the focus position of the treatment, and is directly attached to the skin surface. The focus energy comes from a plurality of piezoelectric chips at different positions, and the micro piezoelectric chips are controlled to turn on and off according to the difference between the piezoelectric chips and the focus position. Turn off the timing to effectively reduce the risk of near-field thermal deposition and out-of-focus areas damaging other tissues.

Description

An MRI-compatible flexible high-intensity focused ultrasound device

technical field

The invention relates to the technical field of high-intensity focused ultrasound, in particular to an MRI-compatible high-intensity focused ultrasound device.

Background technique

High-intensity focused ultrasound (HIFU) therapy, as a non-invasive, non-ionizing radiation-free hyperthermia technology, has received extensive attention in scientific research and clinical applications. High-intensity focused ultrasound generally adopts a single vibration source, a bowl-shaped self-focusing probe or a phased array method, uses a high-power amplifier to drive high-intensity ultrasound, and focuses the ultrasound to a small area, so that the area can be used in a very short time. When the internal temperature rises above 60°C, irreversible coagulation tissue necrosis occurs in the focus area, and the coagulation necrosis tissue is absorbed by the surrounding normal tissue to achieve the purpose of treatment.

Magnetic resonance imaging (MRI) has many advantages: MRI can perform cross-sectional imaging in any direction, so it can easily display and observe anatomical structures or lesions; MRI can image fine structures such as soft tissue imaging well, with a wide imaging field of view and good spatial resolution. ; The parameters that can be used for MRI imaging are rich, so it can provide various valuable diagnostic information; MRI images do not produce bone artifacts and there is no ionizing radiation damage, which is relatively safer for the human body.

In the current HIFU treatment process, the high-intensity ultrasound emitted by a single high-power ultrasound probe needs to penetrate different media such as water, skin, subcutaneous fat, and soft tissue to reach the lesion location. Due to the small aperture angle of the opening of the focused ultrasound probe, the interface acoustic impedance, inter-tissue absorption coefficient, thermal conductivity coefficient, specific heat capacity and other physical and physiological parameters such as water-skin, skin-subcutaneous fat, subcutaneous fat-soft tissue, and soft tissue-bone on the ultrasonic path are significantly affected. Differences, the ultrasound dose received by the tissues on the ultrasound path is relatively large, which is easy to cause side effects such as inaccurate focus and excessive heat deposition in non-focal areas, thereby damaging normal tissues; during the treatment process, the probe position needs to be adjusted in real time according to the size of the lesion; During the treatment process, the human body's physiological movement or involuntary local movement will cause the actual focus to deviate from the lesion area, causing damage to normal tissues and other problems. In addition, a large amount of additional equipment is required, such as degassed water for coupling and cooling, mechanical devices for adjusting the probe position, etc. The above problems limit the wide application of ultrasound therapy in clinical and scientific research.

SUMMARY OF THE INVENTION

The present invention provides an MRI-compatible flexible high-intensity focused ultrasound device and a method for using the same. It is not necessary to adjust the probe mechanically to adapt to the treatment focus position. The micro piezoelectric chip controls the timing of opening and closing the micro piezoelectric chip according to the difference between the piezoelectric chip and the focal position, which effectively reduces the risk of near-field thermal deposition and the risk of damage to other tissues in the focus area.

The technical solution of the present invention is realized in the following manner: an MRI-compatible flexible high-intensity focused ultrasound device, comprising a gridded flexible substrate, an ultrasonic piezoelectric wafer, a strap, a matching circuit, a power amplifier, a switch, a signal The ultrasonic piezoelectric chip is fixed in the grid of the flexible substrate; the ultrasonic piezoelectric chip is connected to the output port a of the matching circuit, and the input port b of the matching circuit is connected to the output end of the power amplifier; The output end is connected with the input end of the power amplifier, and the input end of the switch is connected with the input end of the signal generator and the single-chip microcomputer;

The signal generator is used to provide the acoustic wave signal; the power amplifier amplifies the small signal output by the signal generator to drive the ultrasonic piezoelectric chip to oscillate and generate ultrasonic waves; the single-chip microcomputer is used to control the switch to realize the ultrasonic piezoelectric chip of different groups. on and off.

The flexible substrate is a polyimide or polyethylene naphthalene substrate.

Preferably, the single-chip microcomputer receives 2D or 3D magnetic resonance image information of MRI; identifies the area to be ultrasounded according to the MRI image, divides the area according to the grid of the flexible substrate, determines the focal coordinates of the tissue, and selects the acoustic coupling The center of each grid imaged by the agent is the coordinate of the corresponding ultrasonic piezoelectric wafer; the single-chip microcomputer calculates the distance l _i between each micro piezoelectric wafer and the focus coordinates according to the image; l _i is the ith ultrasonic piezoelectric wafer. and the distance between the focal points, select the shortest distance l _min in l _i as the reference distance, subtract it from l _min , record the distance difference Δl _i =l _i -l _min , use the acoustic wave transmission formula Δt=Δl _i /c, calculate the i-th The delay time of a micro piezoelectric chip, where c is the average sound speed of ultrasound propagating in human tissues; Calculate the number, power and working time parameters of the piezoelectric wafers that need to work, select an allowable minimum error range ε, and divide the micro piezoelectric wafers whose delay difference is less than the error range ε into a group, and all the micro piezoelectric crystals are divided into different The number of different groups; the single-chip microcomputer controls the switch to realize the on-off of each group of ultrasonic piezoelectric wafers, and finally realizes that the ultrasonic waves generated on the ultrasonic piezoelectric wafers are focused to the same focal area at the same time, so that the temperature of the area rises.

A method for using an MRI-compatible flexible high-intensity focused ultrasound device, comprising the following steps:

(1) Fixing the device: Before the magnetic resonance scan, two pairs of elastic straps are used to fix the flexible substrate on the human body, and an acoustic couplant is applied between the flexible substrate and the human skin;

(2) Focus positioning: use MRI to perform magnetic resonance scanning, obtain 2D or 3D magnetic resonance images, determine the focus area, and select the focus position according to the size of the area;

(3) Parameter calculation: According to the focus and the position of each ultrasonic piezoelectric chip, calculate the delay time of each ultrasonic piezoelectric chip to emit sound waves; the simulation calculates the number of chips or chip groups to be used, the required power and work time;

(4) Array division: The delay is grouped, and an allowable quantization time ε is taken, and the micro piezoelectric chips whose delay difference is less than ε are divided into a group, and the working sequence of each group of piezoelectric chips is adjusted according to the delay.

In the present invention, a miniature ultrasonic piezoelectric wafer is fixed on a gridded flexible substrate to form an array of ultrasonic probes. When using, apply acoustic couplant to the focal site, closely fit the ultrasound probe array to its surface, and then perform magnetic resonance imaging on the site. Determine the size of the corresponding area and the focus of thermal ablation according to the image, calculate the distance from the focus to each micro piezoelectric chip, calculate the delay time of each micro piezoelectric chip to emit sound waves according to the distance, and control the pressure at different positions through a high-speed switch. The turn-on sequence of the electro-chip realizes multi-point time-sharing ultrasonic emission and precise focusing, and improves the shortcomings of near-field overheating and time-consuming and inaccurate mechanical focusing caused by the current bowl-shaped self-focusing probe treatment.

Description of drawings

FIG. 1 is a structural diagram of the device of the present invention.

FIG. 2 is a schematic diagram of the connection of the matching circuit.

FIG. 3 is a working flow chart of the method of use of the present invention.

FIG. 4 is a schematic diagram illustrating the simulation of sound pressure distribution under the excitation condition of the ultrasonic device of the present invention.

FIG. 5 is a schematic diagram illustrating the simulation of sound pressure distribution under the excitation condition of the ultrasonic device in the prior art.

Among them: flexible substrate 1, ultrasonic piezoelectric chip 2, strap 3, matching circuit 4, power amplifier 5, switch 6, signal generator 7, single chip 8.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

As shown in Figure 1, an MRI-compatible flexible high-intensity focused ultrasound device includes a gridded flexible substrate 1, an ultrasonic piezoelectric wafer 2, a strap 3, a matching circuit 4, a power amplifier 5, a switch 6, a signal The generator 7 and the single-chip microcomputer 8, the ultrasonic piezoelectric chip 2 is fixed in the grid of the flexible substrate 1; the ultrasonic piezoelectric chip 2 is connected to the output port a of the matching circuit 4, the input port b of the matching circuit 4 and the power amplifier 5 The output terminal is connected; the output terminal of the switch 6 is connected with the input terminal of the power amplifier 5, and the input terminal of the switch switch 6 is connected with the input terminal of the signal generator 7 and the single-chip microcomputer 8;

The signal generator 7 is used to provide acoustic wave signals; the power amplifier 5 amplifies the small signal output by the signal generator 7 to drive the ultrasonic piezoelectric wafer 2 to oscillate to generate ultrasonic waves; the single-chip microcomputer 8 is used to control the switch 6 to realize the On and off of different groups of ultrasonic piezoelectric wafers.

In this application, the material of the flexible substrate 1 can be selected from polyimide (PI), polyethylene naphthalene (PEN), etc., but is not limited to these materials; a miniature ultrasonic piezoelectric chip 2 is fixed on the flexible substrate 1 Each ultrasonic piezoelectric chip is connected to the output port a of the matching circuit 4, and the input port b of the matching circuit is connected to the output end of the power amplifier 5; Composition, output port a and input port b; switch 6 is used to switch one or more micro piezoelectric chips, MAX14979E of MAXIM company or CH440DS1 chip of Qinheng Microelectronics can be selected, but not limited to the two. Ultrasonic piezoelectric wafers can be made of piezoelectric ceramics such as lead zirconate titanate (PZT), piezoelectric polymers such as polyvinylidene fluoride (PVDF), and piezoelectric composite materials, which can be prepared into large-area piezoelectric films. The piezoelectric chip used is non-magnetic, has good mechanical properties, is not easy to be broken and broken, the dielectric loss tangent tanδ is as small as possible, the mechanical quality factor Q _m is as large as possible, the frequency range is controlled within 50KHz-2MHz, and the time-sharing or simultaneous work ; Programmable signal generator 7 provides the set acoustic wave small signal for the normal operation of the device; Power amplifier 5 (using multi-channel radio frequency power amplifier) amplifies the small signal output by signal generator 7 to drive ultrasonic piezoelectric wafer 2 to oscillate, Ultrasonic waves are generated; the single-chip microcomputer 8 is used to control the switch 6 to realize the on-off of the micro-piezoelectric chips of different groups. The strap 3 is composed of two pairs of elastic straps arranged on the flexible substrate, and one end of the straps is provided with a Velcro to facilitate adhesion.

In the present invention, the single-chip microcomputer 8 is used to receive 2D or 3D magnetic resonance image information of MRI; the area to be ultrasound is identified according to the MRI image, and the area is divided according to the grid of the flexible substrate 1 to determine the focus of the tissue Coordinates, select the center of each grid imaged by the acoustic couplant as the coordinates of the corresponding ultrasonic piezoelectric wafer 2;

The single-chip microcomputer calculates the distance l _i between each micro piezoelectric chip and the focus coordinate according to the image; l _i is the distance between the ith ultrasonic piezoelectric chip and the focus, and the shortest distance l _min in l _i is selected as the reference distance, which is the same as l _min Subtract, record the distance difference Δl _i =l _i -l _min , use the acoustic wave transmission formula Δt=Δl _i /c to calculate the delay time of the ith micro piezoelectric chip, where c is the propagation of ultrasound in human tissue Average speed of sound; Combined with the focus determined on the magnetic resonance image and the different ultrasonic paths formed by the ultrasonic piezoelectric chip 2, simulate and calculate the number of piezoelectric chips that need to work, power and working time parameters, and select an allowable minimum error The range ε, the micro piezoelectric crystals whose time delay difference is less than the error range ε are divided into one group, and all the micro piezoelectric crystals are divided into different numbers of different groups;

The single-chip microcomputer controls the switch 6 to turn on and off each group of ultrasonic piezoelectric wafers 2, and finally realizes that the ultrasonic waves generated on the ultrasonic piezoelectric wafers 2 are focused to the same focus area at the same time, so that the temperature of the area rises.

The method of using an MRI-compatible flexible high-intensity focused ultrasound device includes the following steps:

(1) Fixing the device: Before the magnetic resonance scan, two pairs of elastic straps 3 are used to fix the flexible substrate 1 on the human body, and an acoustic couplant is applied between the flexible substrate 1 and the human skin;

(2) Focus positioning: use MRI to perform magnetic resonance scanning, obtain 2D or 3D magnetic resonance images, determine the focus area, and select the focus position according to the size of the area;

(3) Parameter calculation: According to the focus and the position of each ultrasonic piezoelectric chip, calculate the delay time of each ultrasonic piezoelectric chip to emit sound waves; the simulation calculates the number of chips or chip groups to be used, the required power and work time;

(4) Array division: The delay is grouped, and an allowable quantization time ε is taken, and the micro piezoelectric chips whose delay difference is less than ε are divided into a group, and the working sequence of each group of piezoelectric chips is adjusted according to the delay.

In the present invention, the flexible substrate adopts a grid design, and the grid size is the same as that of the micro piezoelectric chip, which is convenient to install and fix the micro piezoelectric chip. The ultrasonic piezoelectric chips are fixed on the flexible substrate in the order and number, and the wiring port group of the piezoelectric chips is reserved on the back of the flexible substrate to facilitate the connection of matching circuits.

The MRI-compatible flexible high-intensity focused ultrasound device of the present invention, used in conjunction with MRI, can be used as a high-intensity focused ultrasound (HIFU) treatment device, and its use method is shown in 3, including the following steps:

(1) Select a water-soluble acoustic couplant that can be visualized by magnetic resonance imaging to cooperate with the device;

(2) Fixing the entire present invention on the area to be treated in the human body, such as the buttocks, evenly applying acoustic couplant between the buttocks and the flexible substrate, compacting to remove possible air, and sending the treated area into the center of the magnet;

(3) Select an appropriate MRI scan sequence for imaging to obtain a clear 2D or 3D magnetic resonance image;

(4) Identify the lesion area according to the MRI image, divide the lesion tissue according to grids, determine the focus coordinates of the treatment, and select the center of each grid imaged by the acoustic couplant as the coordinates of the corresponding piezoelectric wafer, Calculate the distance between each micro piezoelectric chip and the treatment focus of the lesion tissue according to the image;

(5) The distance l _i between the i-th miniature piezoelectric chip and the focal point, select the shortest distance l _min in l _i as the reference distance, subtract it from l _min , record the distance difference Δl _i =l _i -l _min , use acoustic wave transmission The formula Δt=Δl _i /c calculates the delay time of the i-th micro piezoelectric chip, where c is the average sound speed of ultrasonic propagation in human tissue;

(6) Combined with the focus determined by the lesion area on the magnetic resonance image and the different ultrasonic paths formed by the position of the ultrasonic wafer, simulate and calculate the parameters such as the number, power and working time of the micro piezoelectric wafers that need to work. Select an allowable minimum error range ε, divide the micro piezoelectric wafers whose delay difference is less than the error range ε into one group, and divide all the micro piezoelectric crystals into different numbers of different groups;

(7) The single-chip microcomputer controls the multi-channel high-speed switching switch to realize the on and off of each group of micro piezoelectric chips, and finally realize that the ultrasonic waves generated on the micro piezoelectric chips are focused to the same focal area at the same time, so that the temperature of the area rises to achieve ablation the purpose of the organization.

Figures 4 and 5 are the sound pressure distribution diagrams under different conditions obtained from the simulation code written in matlab, and X and Y are the spatial coordinates in the plane. The simulation results of the sound pressure distribution under the same probe excitation conditions show that the flexible phased array ultrasonic probe of the present invention is more suitable for the bone shape. Fig. 4 shows that the device of the present invention is close to the surface of the tissue, and the sound pressure distribution is simulated and calculated under the condition that it fits the shape of the bone. It can be seen that the sound pressure is stronger than that of the non-fitting method, and the actual focus and theoretical focus The dots in the figure are basically consistent; Figure 5 shows that the ultrasonic probe with a fixed shape in the prior art is wrapped on the surface of the bone, and the sound pressure distribution is simulated and calculated. It can be seen that when the ultrasonic probe does not fit closely with the bone, the sound pressure is weak. And it deviates from the theoretical focus (dots in the figure), and its distortion is more obvious as the distance between the ultrasound probe and the bone increases.

The foregoing has shown and described the basic principles, main features and advantages of the present invention. The technical personnel of this industry should understand that the present invention is not limited by the above embodiments. The above embodiments and instructions are only preferred by the invention, and they are not used to limit the invention. Under the premise, there will be various changes and improvements of the present invention, and these changes and improvements will fall into the scope of the invention required for protection. The claimed scope of the present invention is defined by the appended claims and their equivalents.

Claims (2)

1. An MRI compatible flexible high intensity focused ultrasound device characterized by: the ultrasonic wave sensor comprises a meshed flexible substrate (1), an ultrasonic piezoelectric wafer (2), a binding band (3), a matching circuit (4), a power amplifier (5), a selector switch (6), a signal generator (7) and a single chip microcomputer (8), wherein the ultrasonic piezoelectric wafer (2) is fixed in meshes of the flexible substrate (1); the ultrasonic piezoelectric wafer (2) is connected with an output port a of the matching circuit (4), and an input port b of the matching circuit (4) is connected with an output end of the power amplifier (5); the output end of the change-over switch (6) is connected with the input end of the power amplifier (5), and the input end of the change-over switch (6) is connected with the input end of the signal generator (7) and the singlechip (8);

the signal generator (7) is used for providing sound wave signals; the power amplifier (5) amplifies the small signal output by the signal generator (7) to drive the ultrasonic piezoelectric wafer (2) to oscillate and generate ultrasonic waves; the singlechip (8) is used for controlling the selector switch (6) to realize the on-off of the ultrasonic piezoelectric wafers of different groups;

the single chip microcomputer (8) receives 2D or 3D magnetic resonance image information of MRI; identifying an area to be subjected to ultrasound according to the MRI image, dividing the area according to grids of the flexible substrate (1), determining a focus coordinate of a tissue, and selecting the center of each grid imaged by the acoustic coupling agent as the coordinate of the corresponding ultrasonic piezoelectric wafer (2);

the singlechip calculates the distance l between each miniature piezoelectric chip and the focal point coordinate according to the image _i ；l _i Selecting the distance between the ith ultrasonic piezoelectric wafer and the focal point _i Middle and shortest distance l _min As a reference distance, with l _min Subtracting, recording the difference Δ l _i ＝l _i -l _min Using the acoustic transmission formula Δ t = Δ l _i Calculating the delay time of the ith miniature piezoelectric chip, wherein c is the average speed of sound of ultrasound propagating in human tissues; combining different ultrasonic paths formed by the determined focus and the position of the ultrasonic piezoelectric wafer (2) on the magnetic resonance image, simulating, calculating the number, power and working time parameters of the piezoelectric wafers needing to work, selecting an allowable minimum error range epsilon, dividing the miniature piezoelectric wafers with the delay difference smaller than the error range epsilon into a group, and dividing all the miniature piezoelectric crystals into different groups with different numbers;

the single chip microcomputer controls the change-over switch (6) to realize the on-off of each group of ultrasonic piezoelectric wafers (2), and finally, the ultrasonic waves generated on the ultrasonic piezoelectric wafers (2) are focused to the same focal region at the same time, so that the temperature of the region is increased.

2. The MRI compatible flexible high intensity focused ultrasound device according to claim 1, wherein: the flexible substrate (1) is a polyimide or polyethylene naphthalate substrate.

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