Device for researching relation between HIFU transducer electrical impedance and tissue temperature

Abstract

A device for studying the relation between the electrical impedance and the tissue temperature of an HIFU transducer comprises a tissue and transducer placing container, a transducer driving signal source, a power amplifier, a transducer impedance and tissue temperature detection subsystem and an auxiliary heating and heat preservation subsystem, and is mainly characterized in that the tissue temperature and the electrical impedance of the HIFU transducer under different working frequencies can be measured synchronously; under the condition that the transducer cannot provide enough sound power, the thermal power can be supplemented through auxiliary heating and heat preservation of the water bath kettle, and the test research of the relation between the tissue temperature and the electrical impedance of the transducer is very convenient.

Description

Technical Field

[0001] This invention relates to an apparatus for studying the relationship between the impedance of a HIFU transducer and tissue temperature.

[0002] HIFU (high-intensity focused ultrasound), also known as ultrasonic scalpel, is a thermotherapy method whose focal zone temperature needs to be monitored. Too low a temperature will not achieve the desired effect, while too high a temperature will inevitably increase trauma and pain. Monitoring tissue focal zone temperature based on changes in transducer impedance during HIFU operation is a research direction that has received considerable attention in the industry. The fundamental scientific questions involved are whether and how tissue temperature changes are related to changes in the impedance of the HIFU transducer, requiring a dedicated device for investigation. Background Technology

[0003] Reference [1] constructed a real-time detection platform for transducer voltage and current. The HIFU irradiation platform was the HIFU knife focused ultrasound tumor treatment system (JC200D type, developed by Chongqing HIFU Medical Technology Co., Ltd.). The transducer voltage and current were connected to a PC oscilloscope (Picoscope 2000a, 2407B) through an oscilloscope probe and a current transformer, respectively. The sampling accuracy of the Picoscope was 8 bits. The relationship between the transducer electrical parameters and the tissue focal state was studied. This set of implementation devices was built based on HIFU clinical products and oscilloscopes. It did not measure tissue temperature or the electrical parameters of the transducer at different operating frequencies. Obviously, it was not convenient to use it for the study of the relationship between tissue temperature and transducer impedance.

[0004] References

[0005] [1] Qian Jun, Xie Wei, Zhou Xiaowei, Tan Jianwen, Wang Zhibiao, Du Yonghong, Li Yanhao: Real-time monitoring of focal domain damage by high-intensity focused ultrasound based on transducer drive signal characteristics, Acta Physica Sinica, Vol. 71, No. 3 (2022), 037201-1~9

[0006] [2] Zhao Peng, Research on Temperature Distribution Detection and Prediction of Biological Tissues under High Intensity Focused Ultrasound, Doctoral Dissertation, Changchun University of Technology, May 2024 Summary of the Invention

[0007] Purpose of the invention

[0008] A device is proposed for studying the relationship between the impedance of a HIFU transducer and tissue temperature. It can simultaneously measure tissue temperature and the impedance of the HIFU transducer at different operating frequencies. When the transducer cannot provide sufficient acoustic power, thermal power can be supplemented by auxiliary heating and insulation to facilitate the study of the relationship between tissue temperature and transducer impedance.

[0009] Technical solution

[0010] A device for studying the relationship between the impedance of a HIFU transducer and tissue temperature, comprising a tissue and transducer placement container, a transducer drive signal source and power amplifier, a transducer impedance and tissue temperature detection subsystem, and an auxiliary heating and insulation subsystem, characterized in that: (1) the tissue and transducer placement container holds the tissue to be tested, a thermocouple sensor for measuring tissue temperature, and a HIFU transducer; (2) the HIFU transducer and its drive signal source and power amplifier provide acoustic power to heat the tissue to be tested; when sufficient thermal power cannot be provided, the auxiliary heating and insulation subsystem can supplement the thermal power; (3) the transducer impedance and tissue temperature detection subsystem monitors the tissue temperature and the impedance of the transducer in real time, using a single chip... The data acquisition board with the microcontroller as the core transmits the acquired data to the host computer. (4) The auxiliary heating and heat preservation subsystem uses a water bath for heating and heat preservation. The water bath is equipped with electric heating tubes and water temperature measurement sensors. The control circuit board with the microcontroller as the core controls the heating, water temperature testing and heat preservation of the water in the water bath. The host computer configures the heating and heat preservation scheme for the microcontroller. (5) The tissue and transducer placement container is placed on the shelf in the water bath. The control circuit board of the auxiliary heating and heat preservation subsystem, the detection circuit board of the transducer impedance and tissue temperature detection subsystem, and the transducer drive signal source are placed in the same measurement and control box. One end of the measurement and control box is connected to the water bath and the tissue and transducer placement container, and the other end is connected to the host computer. The device block diagram is as follows. Figure 1 As shown.

[0011] According to the above-described apparatus for studying the relationship between HIFU transducer impedance and tissue temperature, the apparatus includes a tissue and transducer placement container, a thermocouple sensor for measuring tissue temperature, and the HIFU transducer. Its features are: (a) the HIFU transducer is fixed to the side wall of the container, allowing the tissue to fill the entire container as much as possible, with degassed water filling any gaps; (b) the thermocouple sensor is inserted into the focal region of the tissue to measure the tissue temperature. A schematic diagram of the tissue and transducer placement container is shown below. Figure 2 As shown.

[0012] According to the above-described apparatus for studying the relationship between HIFU transducer impedance and tissue temperature, the HIFU transducer, its driving signal source, and power amplifier are characterized in that: (a) when the power amplification factor is insufficient or it is inconvenient to use a power amplifier, the signal source can be directly connected to the transducer to supplement the tissue heating through an auxiliary heating and heat preservation subsystem, which makes it easier to support the study of the relationship between tissue temperature change and transducer impedance change; (b) the frequency of the signal source can be arbitrarily set by the host computer within a certain range, including 10Hz to 2MHz.

[0013] According to the above-described device for studying the relationship between HIFU transducer impedance and tissue temperature, the transducer impedance and tissue temperature detection subsystem monitors the tissue temperature and transducer impedance in real time. The data acquisition board with a microcontroller as the core transmits the acquired data to the host computer. Its features are: (a) the impedance spectrum tested at each tissue temperature, including the resistance spectrum and the reactance spectrum, can cover the frequency range of 10Hz to 2MHz; (b) when the thermocouple tests the tissue temperature, it measures one voltage signal between the two poles of the thermocouple probe and simultaneously measures one signal related to the cold junction temperature to compensate for and calculate the accurate tissue temperature value.

[0014] According to the above-described device for studying the relationship between the impedance of a HIFU transducer and tissue temperature, the auxiliary heating and insulation subsystem uses a water bath for heating and insulation. The water bath is equipped with electric heating tubes and water temperature measurement sensors. A control circuit board with a microcontroller as the core controls the heating of the water in the water bath, realizes water temperature testing and water insulation. The host computer configures the heating and insulation scheme to the microcontroller. Its features are: (a) the setting of several water temperature control points and the insulation time of each water temperature point are provided by a comprehensive heating and insulation scheme provided by the host computer. It is a programmable temperature control, rather than manual temperature control like a general water bath; (b) the heating rod is controlled by the microcontroller and relays to turn on and off, and the heating power is adjustable in the range of 0 to 2 kW.

[0015] According to the above-described apparatus for studying the relationship between HIFU transducer impedance and tissue temperature, the tissue and transducer placement container are placed on a shelf in a water bath. The control circuit board of the auxiliary heating and insulation subsystem, and the data acquisition board of the transducer impedance and tissue temperature detection subsystem are all centrally located in the same control box. One end of the control box is connected to the water bath and the transducer and tissue placement container, and the other end is connected to a host computer. The apparatus is characterized by: (a) the rear panel of the control box has one 220V AC power input and one 220V AC power output socket. The input socket is connected to a relay inside the control box, and the output of the relay passes through the output socket to the heating rod in the water bath. There is also one water temperature probe interface. (b) the front panel of the control box includes five interfaces: one for inputting the transducer impedance measurement voltage signal, two for inputting the thermocouple voltage and its cold junction temperature voltage signals respectively, and two communication interfaces for communication with the host computer. A schematic diagram of the control box is shown below. Figure 3 As shown.

[0016] Beneficial effects

[0017] The prototype device developed according to this technical solution is detailed in the following embodiments. Experimental studies have shown that the device developed according to this technical solution can be used to study the relationship between the impedance of the HIFU transducer and tissue temperature. Even without the use of a power amplifier, it can still reliably supplement the heat power of the auxiliary heating and heat preservation subsystem to complete the study on the relationship between the impedance of the HIFU transducer and tissue temperature.

[0018] Fresh, isolated porcine liver tissue was used in the experiment. The tissue and transducer were housed in an acrylic box with an inner diameter of 60mm × 60mm × 55mm. The transducer center was 25mm from the upper inner surface of the acrylic box. Thermocouples were vertically inserted into the tissue and fixed at the focal point. The maximum power of the heating rod was set to 1kW, and the water level in the water bath reached the lower top surface of the acrylic container. The transducer was directly connected to a signal source, with the operating frequency set to a center frequency of 1.02MHz. The water temperature control points were set to integer temperatures within the range of 26-98℃. Data was collected when the actual water temperature differed from the set water temperature by within 0.1℃.

[0019] The tested tissue was heated from 22℃ to 74℃, and the relationship between the impedance amplitude of the HIFU transducer and the tissue temperature was obtained as follows: Figure 4 As shown, the transducer impedance amplitude initially decreased slowly with increasing tissue temperature, but dropped sharply at 61°C, followed by violent fluctuations. It can be inferred that at this temperature, coagulative necrosis of the tissue cells and tissue degeneration led to significant changes in the tissue's acoustic properties, thus further causing violent fluctuations in the transducer impedance amplitude. Attached Figure Description

[0020] Figure 1 This application contains a structural block diagram of a research device for studying the relationship between temperature and transducer impedance.

[0021] Figure 2 This application presents a schematic diagram of the tissue and transducer placement container. The HIFU transducer is secured in the groove. (Using pig liver tissue as an example.)

[0022] Figure 3 The diagram shows the front and rear panels of the control box in this application. One panel has three interfaces: a 220V AC INPUT, a 220V AC OUTPU, and a temperature control thermometer, used for the water bath heating and insulation subsystem. The other panel has three interfaces: a cold junction thermometer, a thermocouple thermometer, and a HIFU transducer, used for the transducer impedance and tissue temperature detection subsystem. There are also two host computer communication interfaces: a detection USB and a temperature control USB, used for communication between the measurement subsystem and the heating and insulation subsystem, respectively.

[0023] Figure 4 A schematic diagram showing the relationship between the impedance amplitude of a HIFU transducer and tissue temperature. Detailed Implementation

[0024] Example

[0025] Based on the above technical solution, a device was developed for studying the relationship between HIFU transducer impedance and tissue temperature. The device includes a tissue and transducer placement container, a transducer drive signal source and power amplifier, a transducer impedance and tissue temperature detection subsystem, and an auxiliary heating and insulation subsystem. Specific implementation features are as follows:

[0026] (1) The tissue and transducer container is made of acrylic material. The thermocouple sensor for measuring tissue temperature is a T-type thermocouple (accuracy 0.5℃). The HIFU transducer is a concave spherical focusing transducer (center frequency 1.02MHz, focal length 25mm). The HIFU transducer is fixed to the side wall of the container, allowing the tissue to fill the entire container as much as possible. Gaps are filled with degassed water. The thermocouple sensor is inserted into the focal region of the tissue to measure tissue temperature. See [link to relevant documentation]. Figure 2 As shown;

[0027] (2) The transducer and its driving signal source and power amplifier are used to provide acoustic power for HIFU. The signal source used is 9833. The frequency of the signal source can be set arbitrarily by the host computer within a certain range, including 10Hz~2MHz. In practice, in order to facilitate the signal source to be directly connected to the transducer, the tissue is supplemented by the auxiliary heating and heat preservation subsystem. This can be used to study the relationship between tissue temperature change and transducer impedance change.

[0028] (3) Transducer impedance and tissue temperature detection subsystem: Real-time monitoring of tissue temperature and transducer impedance. The data acquisition board with microcontroller as the core transmits the acquired data to the host computer. The impedance spectrum tested at each tissue temperature, including resistance spectrum and reactance spectrum, can cover the frequency range of 10Hz to 2MHz. When the thermocouple tests the tissue temperature, it measures the voltage signal between the two poles of the thermocouple probe and measures the signal related to the cold junction temperature. Based on the LMT70 chip, the cold junction temperature is converted into a voltage signal to compensate for the calculation of accurate tissue temperature value.

[0029] (4) The auxiliary heating and heat preservation subsystem adopts a water bath for heating and heat preservation. The water bath is equipped with electric heating tubes and water temperature test sensors. The control circuit board with the microcontroller as the core controls the heating, water temperature test and water heat preservation of the water in the water bath. The host computer configures the heating and heat preservation scheme to the microcontroller. The number of water temperature control points and the heat preservation time of each water temperature point are provided by the host computer in a comprehensive heating and heat preservation scheme, that is, programmable temperature control, rather than manual temperature control as in a general water bath. The water temperature probe is based on the tmpl17 chip. The heating rod is controlled by the microcontroller and relays to turn on and off. The heating power is adjustable in the range of 0 to 2kW.

[0030] (5) The tissue and transducer placement container is placed in the water bath via a shelf. The control circuit board of the auxiliary heating and heat preservation subsystem, the detection circuit board of the tissue temperature and transducer impedance detection subsystem, and the transducer drive signal source are placed in the same control box. One end of the control box is connected to the water bath and the tissue and transducer placement container, and the other end is connected to the host computer. The rear panel of the control box has one 220V AC power input and one output socket. The input socket is connected to the relay in the control box. The output socket of the relay is connected to the heating rod in the water bath. There is also a water temperature probe interface. The front panel of the control box includes five interfaces: one for inputting the transducer impedance measurement voltage signal, two for inputting the thermocouple voltage and its cold junction temperature voltage signal respectively, and two communication interfaces for communication with the host computer.

Claims

1. An apparatus for studying the relationship between the impedance of a HIFU transducer and tissue temperature, comprising a tissue and transducer placement container, a transducer drive signal source and power amplifier, a transducer impedance and tissue temperature detection subsystem, and an auxiliary heating and insulation subsystem, characterized in that, (1) The tissue and transducer placement container is used to place the tissue to be tested, thermocouple sensors for measuring tissue temperature, and HIFU transducers. (2) The HIFU transducer and its drive signal source and power amplifier provide acoustic power to heat the tissue to be tested. When it cannot provide enough heat power, the auxiliary heating and heat preservation subsystem can be used to supplement the heat power. (3) The transducer impedance and tissue temperature detection subsystem monitors the tissue temperature and transducer impedance in real time. The data acquisition board with the microcontroller as the core transmits the collected data to the host computer. (4) The auxiliary heating and heat preservation subsystem uses a water bath for heating. The water bath is equipped with electric heating tubes and water temperature measurement sensors. The control circuit board with the microcontroller as the core controls the heating, water temperature testing and water insulation of the water bath. The host computer configures the heating and insulation scheme for the microcontroller. (5) The tissue and transducer placement container is placed on the shelf in the water bath. The control circuit board of the auxiliary heating and insulation subsystem, the detection circuit board of the transducer impedance and tissue temperature detection subsystem, and the transducer drive signal source are placed in the same measurement and control box. One end of the measurement and control box is connected to the water bath and the tissue and transducer placement container, and the other end is connected to the host computer.

2. The apparatus for studying the relationship between HIFU transducer impedance and tissue temperature according to claim 1, wherein the tissue and transducer are placed in a container, and the thermocouple sensor and HIFU transducer are arranged to measure the tissue temperature, characterized in that, (a) The HIFU transducer is fixed to the side wall of the container, allowing the tissue to fill the entire container as much as possible, and the gaps are filled with degassed water; (b) Thermocouple sensors are inserted into the focal zone of the tissue to measure the tissue temperature.

3. The apparatus for studying the relationship between the impedance of a HIFU transducer and tissue temperature according to claim 1, comprising the HIFU transducer, its driving signal source, and its power amplifier, characterized in that... (a) When the power amplification factor is insufficient or it is inconvenient to use a power amplifier, the signal source can be directly connected to the transducer and the tissue can be supplemented with heating through the auxiliary heating and insulation subsystem. This makes it easier to support the study of the relationship between tissue temperature change and transducer impedance change; (b) The frequency of the signal source can be arbitrarily set by the host computer within a certain range, including 10Hz to 2MHz.

4. The device for studying the relationship between HIFU transducer impedance and tissue temperature according to claim 1, wherein the transducer impedance and tissue temperature detection subsystem monitors the tissue temperature and transducer impedance in real time, and the data acquisition board with a microcontroller as the core transmits the acquired data to the host computer, characterized in that, (a) The electrical impedance spectrum, including the resistance spectrum and the reactance spectrum, is measured at each tissue temperature and can cover the frequency range of 10 Hz to 2 MHz. (b) When testing tissue temperature with a thermocouple, one voltage signal between the two poles of the thermocouple probe is measured, and one signal related to the cold junction temperature is measured at the same time to compensate for and calculate the accurate tissue temperature value.

5. The apparatus for studying the relationship between HIFU transducer impedance and tissue temperature according to claim 1, wherein the auxiliary heating and insulation subsystem employs a water bath for heating and insulation, the water bath is equipped with electric heating tubes and a water temperature measuring sensor, a control circuit board with a microcontroller as its core controls the heating of the water in the water bath, realizes water temperature testing and water insulation, and the host computer configures the heating and insulation scheme to the microcontroller, characterized in that, (a) The setting of several water temperature control points and the duration of heat preservation at each water temperature point are provided by a comprehensive heating and heat preservation scheme provided by the host computer. It is a programmable temperature control, rather than a manual temperature control like a typical water bath. (b) The heating rod is controlled by a microcontroller and a relay to turn on and off, and the heating power is adjustable in the range of 0 to 2 kW.

6. The apparatus for studying the relationship between HIFU transducer impedance and tissue temperature according to claim 1, wherein the tissue and transducer placement container are placed on a shelf in a water bath, the control circuit board of the auxiliary heating and insulation subsystem, and the data acquisition board of the transducer impedance and tissue temperature detection subsystem are centrally placed in the same measurement and control box, one end of the measurement and control box is connected to the water bath and the transducer and tissue placement container, and the other end is connected to the host computer, characterized in that, (a) The rear panel of the control box has one 220V AC power input and one output socket. The input socket is connected to the relay inside the control box. The output of the relay is connected to the heating rod in the water bath through the output socket. There is also a water temperature probe interface. (b) The front panel of the control box includes 5 interfaces: one for inputting the voltage signal of the transducer impedance measurement, two for inputting the voltage signal of the thermocouple and its cold junction temperature, and two communication interfaces for communication with the host computer.

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