KR101462024B1 - Method and Apparatus for Controlling Output Power of Tranducer based on Blood Flow Change Information - Google Patents

Abstract

A method and apparatus for adjusting the output of an ultrasonic transducer based on information of change in blood flow volume. According to an aspect of the present invention, there is provided a method and an apparatus for adjusting the output of a transducer based on information of change in blood flow volume of a human body portion to which a transducer is contacted to prevent skin damage such as an image in the case of ultrasonic treatment or the like do.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method and apparatus for adjusting output of a transducer based on information on change in blood flow volume,

The present embodiment relates to a method and apparatus for adjusting the output of a high-intensity focused ultrasonic transducer based on information on the change in blood flow volume. More particularly, the present invention relates to a method of adjusting the output of a transducer based on information of change in blood flow volume in a human body region to which a transducer is contacted in order to prevent damage to skin such as an image during high intensity focused ultrasound (HIFU) And apparatus.

The contents described in this section merely provide background information on the present embodiment and do not constitute the prior art.

In general, the diagnosis and treatment of the human body using ultrasound is not limited to the incision due to the use of scalpel and the subsequent occurrence of surgical scar, and there is no fear of secondary infection, Examples of applications of ultrasound to the medical field include diagnostic fields such as fetal diagnosis and cancer tissue diagnosis, and therapeutic fields such as fat removal, cancer tissue or malignant tumor destruction.

Among them, high intensity focused ultrasound (hereinafter abbreviated as HIFU) treatment is performed by irradiating a lesion part such as a tumor, thrombus, or cerebral infarction with ultrasonic waves and denaturing (for example, cauterizing or destroying) the lesion part by heat It is a treatment to treat. HIFU therapy has been developed for the treatment of prostate cancer, but it has been gradually expanded to include non-solid tumors such as brain cancer, myoma, and arrhythmia, including solid tumors such as liver cancer, breast cancer and pancreatic cancer. In particular, HIFU treatment has shown excellent results in the treatment of pancreatic cancer which can not be treated with liver cancer and surgical operation.

The effects of HIFU treatment include thermal effects, cavitation effects, mechanical effects, tumor surrounding capillary damage, and immune effects. The heat effect induces vascular coagulation and necroses tumor cells to more than 65 degrees. The cavitation effect increases the pressure in the cell, denaturing the protein structure of the cell and destroying the tumor DNA. The mechanical effect is to destroy the chemical link between cancer cells. The destruction of the surrounding capillaries is to prevent tumor growth by destroying the surrounding capillaries that nourish the tumor as well as the therapeutic lesion. It means to recognize the destroyed tumor cells as an antigen and to increase immunity such as an increase in lymphocyte. Among these, HIFU treatment effect by heat effect is the most representative.

In the HIFU treatment described above, a considerable amount of energy is applied to the patient's body in order to heat the lesion. A side effect of heating the patient's skin due to the acoustic impedance mismatch between the patient's skin and the coupling agent (e.g., hydrogel) . These acoustic impedance mismatches cause the patient to be significantly heated on the surface of the skin, which sometimes makes the patient uncomfortable, and may cause burns to the skin or mucous membranes. Such side effects can be exacerbated by the bubbles that may be present between the skin and the coupling agent, or the fur of the skin. Therefore, HIFU treatment requires a method that can effectively prevent overheating of such patients' tissues (e.g., skin or mucosa).

There may be thermocouple monitoring and visual inspection of skin redness to monitor skin temperature. However, the thermocouple approach is incomplete in the case of HIFU treatment because the thermocouple electrode is acoustically opaque and can interfere with the acoustic path. Monitoring skin color changes is not a suitable way to monitor skin temperature during HIFU treatment. Not only does skin color differ from person to person, but skin color does not change until the patient's skin is damaged. In other words, after the redness of the skin tissue is found, the skin tissue is already burned. In addition, rapid feedback control of skin heating during HIFU treatment is not easy because the appearance of redness in the skin tissue against skin heating is a relatively slow reaction.

Photoplethysmography (PPG), on the other hand, is a simple and inexpensive optical technique that can be used non-invasively to observe changes in blood flow primarily in peripheral blood vessels. The PPG signal can be used to detect peripheral vascular disease that affects the arterial blood circulation by tracking the volume change of the arterial blood in the peripheral artery, to evaluate peripheral vascular and aortic elasticity, blood flow resistance of the vascular system, functional evaluation of blood pressure and cardiac output, Saturation measurement, and so on.

The principle of this measurement technique was first used by Hertzman (1938), in which the light source and photodetector are brought into contact with the skin and the change in the amount of light from the light source by transmission, reflection, dispersion, Voltage. The intensity of the detected light changes by factors such as solid tissue, skin, bone, total amount of blood vessels, and the like. Blood has a higher Absorption Coefficient than other tissue components. Thus, it is well known that pulse changes in blood volume in tissues can be observed from the transmission or reflection of light.

The main object of the present invention is to provide a method and an apparatus for adjusting the output of a transducer based on information on the change in blood flow volume of a human body portion to which a transducer is contacted in order to prevent skin damage such as an image during HIFU treatment.

According to an aspect of the present invention, there is provided an ultrasonic transducer including: an ultrasonic transducer having a plurality of transducer elements; a driving unit connected to the ultrasonic transducer for driving the plurality of transducer elements to emit ultrasonic waves to a target portion; And controlling the driving unit to adjust the output of some or all of the plurality of transducer elements in response to changes in blood flow in the skin tissue.

The controller may control the driving unit to stop the driving of some or all of the plurality of transducer elements or lower the intensity of the output when it is determined that the blood flow change is different from the steady state.

In addition, the controller may monitor the blood flow change using one or more photoplethysmography (PPG) signals.

In addition, the PPG signal may be measured in a region adjacent to the skin tissue that the ultrasound transmits, so as not to disturb the acoustic path of the ultrasonic waves radiated from the plurality of transducer elements.

Also, the controller may calculate a peak-to-peak value of an AC component included in the PPG signal, a peak value (DC Peak) of a DC component included in the PPG signal, and a DC component And a bottom value (DC Foot) of the calculated value, and monitor the change in the calculated value.

The control unit may control the driving unit to stop some or all of the plurality of transducer elements or lower the output intensity when it is determined that the change in the calculated value is different from the steady state .

In addition, the ultrasound therapy apparatus may include a plurality of PPG sensors coupled to a membrane or a housing of the ultrasound transducer to contact or contact the skin tissue during ultrasound therapy.

According to another aspect of the present invention, there is provided a method for measuring a blood flow of a skin tissue, the method comprising the steps of irradiating a focused ultrasound wave to a target site, monitoring a blood flow rate change of skin tissue permeated by the ultrasound wave, And adjusting the output of the ultrasonic wave radiated to the ultrasonic wave.

The process of monitoring the blood flow change may be one using at least one PPG signal measured in a region adjacent to the skin tissue that the ultrasound transmits.

The process of controlling the output of the ultrasonic wave may include stopping the emission of the ultrasonic wave corresponding to the measured region of the PPG signal showing a change of the state of the at least one PPG signal from the steady state and lowering the intensity of the radiated ultrasonic wave have.

As described above, according to the present embodiment, the blood flow rate of the capillary blood vessels in the tissue region in direct contact with the membrane of the ultrasound therapy apparatus during the ultrasound therapy can be monitored, and the ultrasound therapy can be controlled according to the monitoring result, .

In particular, the blood flow is very similar to the skin tissue directly transmitted by the ultrasonic wave and the adjacent skin tissue which is not directly transmitted. Therefore, by using the PPG information measured at the skin region which does not disturb the acoustic path of the ultrasonic wave, It is possible to estimate the blood flow of the skin tissue.

1 is a schematic view of an ultrasound therapy apparatus according to an embodiment of the present invention.
Figs. 2A, 2B and 2C are diagrams showing a schematic configuration of a typical PPG measurement system.
3 is a diagram illustrating a form of a PPG signal measured by a transmission method.
4 is a diagram illustrating an AC component and a DC component extracted from the PPG signal.
5 is a graph showing changes in PPG components measured in capillaries according to changes in temperature of skin tissue.
FIG. 6 is a flowchart schematically illustrating an ultrasonic treatment method according to an embodiment of the present invention.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference numerals whenever possible, even if they are shown in different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Throughout the specification, when an element is referred to as being "comprising" or "comprising", it means that it can include other elements as well, without excluding other elements unless specifically stated otherwise . In addition, '... Quot ;, " module ", and " module " refer to a unit that processes at least one function or operation, and may be implemented by hardware or software or a combination of hardware and software.

1 is a schematic view of an ultrasound therapy apparatus according to an embodiment of the present invention.

1, the ultrasound therapy apparatus includes an ultrasound transducer 110, a driving unit 120 connected to the ultrasonic transducer 110, and a controller 130 connected to the driving unit 120. As shown in FIG. do.

The ultrasonic transducer 110 is configured to emit an ultrasonic beam 140 toward the target tissue 151 in the body of the patient 150. The ultrasound beam 140 is used to treat target tissues such as tumors in organs or other tissues by methods such as coagulation, necrosis, and heating. The ultrasonic transducer 110 is mounted on the support 160 of the patient 150 by a mechanical link mechanism and the ultrasonic transducer 110 is mounted on the support 160 of the patient 150 The position can be adjusted. Alternatively, the ultrasonic transducer 110 may be mounted on a mechanical arm independent of the support 160 of the patient 150.

In the illustrated embodiment, the ultrasonic transducer 110 includes a structure 112 and a plurality of transducer elements 111 that are secured to the structure 112. This structure 112 is shown as having a curved shape. In other embodiments, it is also possible for the structure 112 to have a different shape, contour, or structure as long as it provides a surface on which the transducer element 111 can be fixed. In some cases, the ultrasonic transducer 110 may include a membrane (not shown) to remove heat from the transducer element 111 when the focused ultrasound beam is emitted, It may improve the acoustic impedance coupling between the skin of the skin 150.

The transducer element 111 is connected to the driving unit 120 and the control unit 130 so that generation and / or intensity of the irradiated ultrasonic beam 140 is controlled. For example, the driving unit 120 may generate one or more electrical driving signals controlled by the controller 130. The transducer element 111 converts the driving signal input from the driving unit 120 into ultrasonic energy. The control unit 130 and the driving unit 120 may be implemented as separate or integral parts.

The driving unit 120 may be configured as an electric oscillator and generates driving signals of a frequency spectrum of ultrasonic waves of about 50 KHz or 10 MHz, for example. When a driving signal is output to the transducer element 111, the transducer element 111 emits ultrasonic waves from the respective exposed surfaces.

The control unit 130 can control the intensity or the output of the ultrasonic wave radiated from the transducer element 111 by controlling the amplitude of the signal. The control unit 130 controls the shape or size of the focus area formed by the transducer element 111, for example, by controlling the phase component of the drive signal input to each transducer element 111, It is also possible to move the focus area to a desired position. For example, the control unit 130 may adjust the focal distance through phase shift of a driving signal.

In addition, the controller 130 may stop some or all of the plurality of transducer elements 111 or control the amplitude and / or phase of each transducer element 111 to lower the intensity of the ultrasonic waves radiated from some or all of the transducer elements 111 . Particularly, when the tissue damage due to an unintentional temperature rise in the skin tissue transmitted through the ultrasonic wave is predicted, the controller 130 stops the transducer element 111 so that the ultrasonic beam is not transmitted to the skin tissue, The driving unit 120 can be controlled so as to lower the intensity of the ultrasonic beam passing through the skin tissue. According to the embodiment, in order to increase the ultrasonic treatment efficiency in this case, other elements that emit ultrasonic waves to tissues other than the skin tissue can increase the intensity of the ultrasonic waves conversely.

In order to monitor the heating of the skin tissue that may cause tissue damage as described above, the controller 130 may use a photoplethysmography (PPG) signal measured from the skin tissue in the vicinity of the acoustic path through which ultrasonic waves are transmitted . Hereinafter, the measurement and analysis method of the PPG signal will be described in detail.

Figs. 2A, 2B and 2C are diagrams showing a schematic configuration of a typical PPG measurement system.

The PPG measurement system mainly consists of a photo detector (Photo Detector) that converts the light transmitted or reflected from the light source and the skin tissue into an electric current signal by using the photo detector, and a signal processing circuit that processes the output of the photo detector .

2A illustrates a light source composed of two light emitting devices 211 and 212 capable of operating in a red light and a near infrared light wavelength. The two light emitting devices 211 and 212 constituting the light source are a constant current source. 213 to output light having a constant luminance. Generally, a light source is a LED light emitting device that operates in red light and near infrared light.

2B shows a transimpedance amplifier 231 that converts the output current of the photodetector 220 to an amplifier output voltage. The photodetector 220 may be a photodiode (PD), which converts light energy into an electrical signal, or current. The converted current is converted into a DC voltage via the transimpedance amplifier 231 and then subjected to signal processing.

2C illustrates a signal processing circuit 230 of the PPG signal as a functional block. A low pass filter (LPF) having a predetermined cutoff frequency (for example, about 20 Hz) is connected to the output signal of the transimpedance amplifier 231, 232 are separated via a predetermined interface 236. Further, an AC component is extracted via a high pass filter 233 having a predetermined cutoff frequency (e.g., approximately 0.05 Hz). In case of the AC component, the amplified signal is amplified to a predetermined magnitude through an amplifier 234, and the amplified signal is inverted through an inverter / interface 235 and separated into a final AC component signal through a predetermined interface . The process of signal processing the PPG signal to extract the AC component and the DC component is a technique generally known in the art, and thus a detailed description thereof will be omitted.

In the method of measuring the PPG, there are a transmission method (transmission mode) in which light transmitted through the tissue among the light emitted from the light emitting element is detected by the photodetecting element on the opposite side, and light reflected from the tissue, And a reflection mode (detection mode) which is detected by the detecting element. In the transmissive system, the tissue (e.g., a finger) is positioned between the light source and the photodetector, and in the reflective mode, the light source and the photodetector are located side by side. Since ultrasound therapy usually targets a lesion in a human organ, unlike the case of measuring a PPG signal on a finger, a reflection method is more preferable. Usually, the PPG sensor refers to a device including a light emitting element and a light detecting element except a signal processing circuit.

3 is a diagram illustrating a form of a PPG signal measured by a transmission method.

As shown in FIG. 3, the electrical signal obtained from the photodetector is an AC component indicating absorption of pulsed arterial blood due to a heartbeat, and a DC component absorbed by arterial blood, venous blood, skin, bone, .

The AC component of the PPG signal represents the amount of dynamic blood change due to the heartbeat, which is caused by the flow of blood in the arterial blood vessel, which can reflect the arterial blood vessel status. The DC component of the PPG signal can also reflect the volume of static blood in the veins and capillaries as well as arterial blood vessels. Therefore, the change in the DC component has a direct inverse relationship with the blood volume.

4 is a diagram illustrating an AC component and a DC component extracted from the PPG signal.

As described above, the signal of the AC component extracted from the PPG signal represents the amount of blood change due to the heartbeat, and therefore, the AC Gap showing the peak-to-peak voltage in the AC component reflects the state of the arterial blood vessel . Also, the peak value (DC Peak) and the bottom value (DC Foot) of the DC component extracted from the PPG signal reflect the blood volume information of the measurement site.

5 is a graph showing changes in PPG components measured in capillaries according to changes in temperature of skin tissue.

As is well known, as the ultrasound energy is converted from skin tissue to thermal energy on the acoustic path, the temperature of the tissue rises and the function of the cell is enhanced. As the temperature of the tissue rises, the capillaries expand and the tissue blood flow increases. At the beginning of tissue temperature elevation, metabolism is promoted, but when the temperature rises above a certain limit, metabolism decreases. This is because the chemical reaction occurs as the temperature rises and the enzyme activity changes. Especially when the temperature of the tissue exceeds about 45 ° C, protein denaturation occurs.

In response to such metabolism of the tissue according to the temperature, the PPG signal measured from the tissue also changes according to the temperature of the tissue.

According to the experimentally obtained results, as shown in FIG. 5, the AC Gap value of the AC component included in the PPG signal increases as the tissue temperature rises. This is because the AC Gap value reflects the flowable blood flow at the site of measurement, that is, the state of the capillaries in the measurement site. In addition, the DC component of the PPG signal is decreased due to the capillary expansion due to the temperature rise and the increase of the blood flow. On the other hand, if the temperature of the tissue rises above a certain limit (approximately 40 ° C) beyond the normal metabolic range, the capillary blood flow decreases and the AC Gap value of the AC component contained in the PPG signal decreases rather The DC peak and DC foot of the DC component are increased.

Therefore, in the ultrasonic treatment, the abnormal temperature rise of the tissue located in the acoustic path through which the ultrasonic wave passes between the ultrasonic transducer and the target region, in particular, the skin tissue in direct contact with the ultrasonic transducer, is estimated. The AC Gap of the AC component included in the PPG signal, the DC peak of the DC component, or the change pattern of the DC foot can be used.

Referring to FIG. 1 again, the controller 130 can estimate an abnormal temperature rise of the skin tissue transmitted by the ultrasonic waves using the PPG signal measured in the vicinity of the skin tissue permeated by the ultrasonic waves. More specifically, the control unit 130 extracts the AC component and the DC component from the PPG signal measured in the vicinity of the skin tissue that the ultrasound transmits continuously during the ultrasound therapy, extracts the AC component and the DC component from the extracted AC component and the DC component, Peak, and DC Foot can be monitored. As a result, if it is determined that the change in the monitored value is different from the normal state, it can be judged that an abnormal temperature rise has occurred, which may damage the tissue. Accordingly, it is possible to control the driving unit 120 to stop some or all of the plurality of transducer elements 111, or to lower the output intensity of some or all of the plurality of transducer elements 111 to eliminate the abnormal temperature rise of the tissue.

It is preferable that the PPG sensor for measuring the PPG signal is located in an appropriate skin area in the vicinity of the skin tissue through which ultrasonic waves are transmitted so as not to interfere with the acoustic path of the ultrasonic wave. The PPG sensor may be in direct contact with the skin or in close proximity to the skin. In addition, the PPG sensor may be configured to be coupled to the membrane or the housing so that the membrane provided on the front surface of the ultrasonic transducer 110 can contact the skin at the same time when the membrane contacts the skin.

According to the embodiment, the controller 130 may be configured to determine whether a change in blood flow due to an abnormal temperature rise occurs in any part of the skin tissue transmitted through the ultrasonic waves using a plurality of PPG signals. That is, the PPG sensors are disposed in a plurality of sites near the skin tissue that the ultrasound transmits, and the controller 130 analyzes the PPG signals received from the plurality of PPG sensors, It is possible to selectively control only the transducer element 111. According to the embodiment, in order to increase the ultrasonic treatment efficiency in this case, other elements that emit ultrasonic waves to tissues other than the skin tissue can increase the intensity of the ultrasonic waves conversely. In another embodiment, it is also possible to step-up the output intensity of the transducer elements 111 when the temperature rise range of the skin tissue transmitted by the ultrasonic waves is within a normal range. That is, by adjusting the output intensity of the transducer elements 111 adaptively to the PPG signal, the efficiency of ultrasonic treatment can be improved without damaging the skin tissue.

FIG. 6 is a flowchart schematically illustrating an ultrasonic treatment method according to an embodiment of the present invention. The processes of FIG. 6 will be described together with the ultrasonic treatment apparatus of FIG.

As shown in FIG. 6, first, a plurality of transducer elements 111 are irradiated with ultrasound to the target region to treat the lesion (S610).

The control unit 130 continuously monitors the change in the blood flow of the skin tissue that is transmitted by the ultrasonic waves during the ultrasonic wave radiation (S620). That is, the change in the blood flow of the skin tissue is observed from the PPG signal measured in the vicinity of the skin tissue permeated by the ultrasonic waves. As described above, the control unit 130 can extract the AC component and the DC component from the PPG signal, and monitor the change in at least one of AC Gap, DC Peak, and DC Foot from the extracted AC and DC components .

If the blood flow change is different from the normal state (Yes in S630) as a result of monitoring the blood flow change of the skin tissue, the controller 130 controls the plurality of transducer elements 111 (Step S640). The control unit 120 controls the driving unit 120 so as to stop some or all of the output power. On the other hand, if the change in the blood flow rate is determined to be a normal state (NO in S630), the ultrasound treatment through the ultrasound emission is continuously performed on the target site while continuously monitoring the change in the blood flow rate of the skin tissue penetrated by the ultrasound waves.

Although it is described in FIG. 6 that the processes S610 to S640 are sequentially executed, this is merely illustrative of the technical idea of an embodiment of the present invention. In other words, those skilled in the art will recognize that the present invention can be implemented by changing the order described in FIG. 6 without departing from the essential characteristics of an embodiment of the present invention, or by executing one of steps S610 to S640 6 is not limited to the time-series order because it can be variously modified and modified by being executed in parallel.

The foregoing description is merely illustrative of the technical idea of the present embodiment, and various modifications and changes may be made to those skilled in the art without departing from the essential characteristics of the embodiments. Therefore, the present embodiments are to be construed as illustrative rather than restrictive, and the scope of the technical idea of the present embodiment is not limited by these embodiments. The scope of protection of the present embodiment should be construed according to the following claims, and all technical ideas within the scope of equivalents thereof should be construed as being included in the scope of the present invention.

As described above, the present embodiment is applied to a method and an apparatus for adjusting the output of a transducer based on information on the change in blood flow volume of a human body portion to which a transducer is contacted in the case of ultrasonic treatment or the like, It is a useful invention to do.

110: ultrasonic transducer 111: transducer element
112: Structure 120:
130: control unit 211:
212: light emitting element 213: constant current source
220: photodetector 231: transimpedance amplifier
232: Low-pass filter 233: High-pass filter
234: amplifier 235: inverting / interface
236: Interface

Claims (10)

An ultrasonic transducer having a plurality of transducer elements;
A driving unit connected to the ultrasonic transducer and driving the plurality of transducer elements to emit ultrasonic waves to a target portion; And
And a controller for controlling the driving unit to adjust the output of some or all of the plurality of transducer elements in response to changes in blood flow in the skin tissue that the ultrasound transmits,
Wherein the controller controls the driving unit to stop the driving of a part or the whole of the plurality of transducer elements or to lower the intensity of the output when the blood flow variation is determined to be different from the steady state. Treatment device. delete The method according to claim 1,
Wherein,
Wherein the blood flow monitoring unit monitors the blood flow change using at least one photoluminescence pulse signal (PPG) signal. The method of claim 3,
The PPG signal,
Wherein the ultrasonic wave is measured in a region adjacent to the skin tissue through which the ultrasonic waves are transmitted so as not to disturb the acoustic path of the ultrasonic waves radiated from the plurality of transducer elements. The method of claim 3,
Wherein,
A Peak-to-Peak value of an AC component included in the PPG signal, a peak value (DC Peak) of a DC component included in the PPG signal, and a floor value DC of a DC component included in the PPG signal Foot), and monitors the change in the calculated value. 6. The method of claim 5,
Wherein,
And controls the driving unit to stop some or all of the plurality of transducer elements or to reduce the intensity of the output when it is determined that the change in the calculated value is different from the steady state. Treatment device. The method according to claim 1,
The ultrasonic treatment apparatus comprises:
And at least one PPG sensor coupled to the membrane or housing of the ultrasonic transducer so as to be in proximity to or in contact with the skin tissue during ultrasonic treatment.

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