Apparatus and method for controlling the density difference between cortical bone and cancellous bone in the skull high intensity focused ultrasound

Abstract

The present invention discloses a device for controlling the density difference between cortical bone and cancellous bone within the skull for focused ultrasound treatment. According to the present invention, a density difference control device is provided comprising: an ultrasound probe that irradiates ultrasound; and a signal control unit that controls the amplitude and frequency of the ultrasound so that the ultrasound increases the density of the cancellous bone so that the density of the cancellous bone relative to the density of the cortical bone becomes 0.5 or greater, and the ultrasound is attenuated before penetrating the brain region.

Description

Technology Field

[0001] The present invention relates to a method and apparatus for controlling the density difference between cortical bone and cancellous bone within the skull for focused ultrasound therapy. Background Technology

[0002] High Intensity Focused Ultrasound (HIFU) works on a principle similar to a magnifying glass by focusing ultrasound waves onto a single point to raise the temperature and destroy necessary biological tissues. In particular, HIFU treatment is a non-invasive method that has proven effective in removing abnormal biological tissues, such as cancer.

[0003] Recently, a method of treating essential tremor, also known as hand tremor, and Parkinson's tremor by using HIFU to generate heat in the affected area has been proposed.

[0004] However, for this treatment to be effective, the density of cancellous bone (or trabeculae bone, the porous bone tissue inside the skull) relative to the density of cortical bone (the hard bone tissue on the outside) on the surface of the skull must be greater than a certain ratio.

[0005] However, no method has yet been proposed to reduce the density difference between cortical bone and cancellous bone. Prior art literature

[0006] Republic of Korea Published Patent Application 10-2024-0150940 The problem to be solved

[0007] To solve the problems of the aforementioned prior art, the present invention proposes a method and apparatus for controlling the density difference between cortical bone and cancellous bone within the skull for focused ultrasound therapy, which can enhance the therapeutic effect of HIFU by reducing the density difference between cortical bone and cancellous bone on the skull, which is necessary for the treatment of hand tremors and Parkinson's disease. means of solving the problem

[0008] In order to achieve the above-mentioned purpose, according to one embodiment of the present invention, a density difference control device is provided for controlling the density difference between cortical bone and cancellous bone for focused ultrasound treatment, comprising: an ultrasound probe that irradiates ultrasound; and a signal control unit that controls the amplitude and frequency of the ultrasound so that the ultrasound increases the density of the cancellous bone so that the density of the cancellous bone relative to the density of the cortical bone becomes 0.5 or more, and the ultrasound is attenuated before penetrating the brain region.

[0009] The above ultrasound may include one of Low Intensity Pulsed Ultrasound (LIPUS) and Low Intensity Continuous Ultrasound (LICU).

[0010] The above signal modulator can determine the amplitude and frequency of the ultrasound using the thickness of the cortical bone and cancellous bone measured by the imaging device, the difference in intensity between the ultrasound irradiated by the ultrasound probe and the ultrasound reflected from the boundary surface of the cortical bone and cancellous bone, the frequency of the ultrasound, the known attenuation coefficient of the cortical bone and cancellous bone, and an attenuation phenomenon formula to which porous elasticity theory is applied.

[0011] The signal control unit can calculate the attenuation coefficient of the cortical bone using the thickness of the cortical bone, the intensity difference, and the frequency of the ultrasound, correct the previously known attenuation coefficient of the cancellous bone using the difference between the calculated attenuation coefficient of the cortical bone and the previously known attenuation coefficient of the cortical bone and the thickness of the cancellous bone, and apply the corrected attenuation coefficient of the cancellous bone to the attenuation phenomenon formula to determine the amplitude and frequency of the ultrasound so that the ultrasound transmitted through the cancellous bone is extinguished within the cancellous bone.

[0012] The above signal modulator can determine the amplitude and frequency of the ultrasound using the attenuation coefficient formula defined below and the attenuation coefficient of the corrected cancellous bone.

[0013] [Mathematical Formula]

[0014]

[0015] Here, is the attenuation factor of a slow waveform (unit is 1 / m), and when converted to decibels (dB), it is converted to a dimensionless logarithmic value, which is the definition of dB. is the frequency (Hz), is the velocity of ultrasound transmitted into the cancellous bone, and is the velocity of the slow waveform in the porous material calculated through the above damping phenomenon formula.

[0016] The above porous elasticity theory can be expressed by the following mathematical formula.

[0017] [Mathematical Formula]

[0018]

[0019] [Mathematical Formula]

[0020]

[0021] [Mathematical Formula]

[0022]

[0023] Here, N, R, Q, and A are the porous elastic modulus, and u and U are the displacement and variable of the fluid and solid, respectively. Is , here ε is the viscosity of the fluid, and Kp is the permeability of the fluid, is permittivity, ε represents porosity, Gp represents the correlation coefficient between electric current and electrical potential, and is charge density, is electric potential

[0024] The porous modulus, P=A+N, Q, and R can be defined as follows.

[0025] [Mathematical Formula]

[0026]

[0027] [Mathematical Formula]

[0028]

[0029] [Mathematical Formula]

[0030]

[0031] Here, is the bulk modulus of cancellous bone containing porosity, and is the bulk modulus of pure bone tissue, ε is the bulk modulus of the interstitial fluid, and G is the shear modulus of the bone tissue.

[0032] The actual speed and imaginary transmission speed of the slow waveform included in the above attenuation coefficient mathematical formula can be defined as follows.

[0033] [Mathematical Formula]

[0034]

[0035] [Mathematical Formula]

[0036]

[0037] Here

[0038] lim

[0039] Using the velocity of the slow waveform calculated using the above damping coefficient formula and the actual velocity of the above slow waveform, the porosity of the above cancellous bone The amplitude and frequency of the ultrasound can be determined so that it becomes 0.5 or less.

[0040] The bulk modulus of the above cancellous bone can be calculated using the following mathematical formula.

[0041] [Mathematical Formula]

[0042]

[0043] The initial velocity of the above ultrasound can be calculated using the following mathematical formula.

[0044] [Mathematical Formula]

[0045]

[0046] is the Young's modulus of the cortical bone, is the density of cortical bone measured through a bone density test.

[0047] The reflection coefficient, which is the ratio at which the amplitude of the above ultrasound attenuates, can be defined by the following mathematical formula.

[0048] [Mathematical Formula]

[0049]

[0050] Here is the speed of ultrasound irradiated from the ultrasound probe, is the speed of the transmitted ultrasound, is the density of cancellous bone, and is the density of compact bone.

[0051] The transmission coefficient of the above ultrasound is defined by the following mathematical formula when the amplitude is displacement, and

[0052] [Mathematical Formula]

[0053]

[0054] If the amplitude is stress or pressure, it can be defined by the following mathematical formula.

[0055] [Mathematical Formula]

[0056]

[0057] According to another aspect of the present invention, a density difference control device is provided for controlling the density difference between cortical bone and cancellous bone within a skull for focused ultrasound treatment, comprising: a processor; and a memory connected to the processor, wherein the memory stores program instructions executed by the processor to calculate the attenuation coefficient of the cortical bone using the thickness of the cortical bone, the difference in intensity between the ultrasound irradiated from the ultrasound probe and the ultrasound reflected from the boundary between the cortical bone and the cancellous bone, and the frequency of the ultrasound, correct the attenuation coefficient of the cancellous bone using the difference between the calculated attenuation coefficient of the cortical bone and a previously known attenuation coefficient of the cortical bone and the thickness of the cancellous bone, and apply the corrected attenuation coefficient of the cancellous bone to the attenuation phenomenon formula so that the ultrasound increases the density of the cancellous bone so that the density of the cancellous bone relative to the density of the cortical bone becomes 0.5 or greater, and to determine the amplitude and frequency of the ultrasound so that the ultrasound attenuates before penetrating the brain region.

[0058] According to another aspect of the present invention, a density difference correction method is provided for controlling the density difference between cortical bone and cancellous bone within the skull for focused ultrasound treatment, comprising: a step of calculating a cortical bone attenuation coefficient using the thickness of the cortical bone, the difference in intensity between ultrasound irradiated from an ultrasound probe and ultrasound reflected from the boundary between the cortical bone and the cancellous bone, and the frequency of the ultrasound; a step of correcting a known attenuation coefficient of the cancellous bone using the difference between the calculated attenuation coefficient of the cortical bone and a known attenuation coefficient of the cortical bone and the thickness of the cancellous bone; and a step of determining the amplitude and frequency of the ultrasound so that the ultrasound increases the density of the cancellous bone so that the density of the cancellous bone relative to the density of the cortical bone becomes 0.5 or greater, and the ultrasound attenuates before penetrating the brain region. Effects of the invention

[0059] According to the present invention, the frequency and amplitude range of ultrasound can be determined to increase the density of cancellous bone while preventing penetration into the brain region, thereby further enhancing the HIFU treatment effect. Brief explanation of the drawing

[0060] FIG. 1 is a diagram illustrating the configuration of a device for controlling the density difference between cortical bone and cancellous bone within the skull for focused ultrasound treatment according to a preferred embodiment of the present invention. Figure 2 is a diagram showing the change in charge density on the surface of the cancellous bone trabeculae according to wavenumber and frequency. FIG. 3 is a flowchart of the process for determining ultrasound amplitude and frequency that can increase the density of cancellous bone while preventing penetration of the brain region according to the present embodiment. Figure 4 shows the bone tissue structure of the skull. Specific details for implementing the invention

[0061] The present invention is capable of various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the invention to specific embodiments, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0062] When it is stated that one component is "connected" or "connected" to another component, it should be understood that while it may be directly connected or connected to that other component, there may also be other components in between. On the other hand, when it is stated that one component is "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between.

[0063] Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. These terms are used solely for the purpose of distinguishing one component from another. For example, terms such as "first threshold," "second threshold," etc., to be described later may be pre-designated as thresholds that are substantially different or partially identical; however, since there is a possibility of confusion when expressed using the same word "threshold," the terms "first," "second," etc., will be used together for the convenience of distinction.

[0064] The terms used herein are merely for describing specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “comprising” or “having” are intended to indicate the presence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0065] Furthermore, the components of the embodiments described with reference to each drawing are not limited to the respective embodiments and may be implemented to be included in other embodiments within the scope of maintaining the technical spirit of the present invention. It is also obvious that multiple embodiments may be re-implemented as a single embodiment that integrates multiple embodiments, even if a separate description is omitted.

[0066] Furthermore, in the description referring to the attached drawings, identical components are assigned the same or related reference numerals regardless of drawing symbols, and redundant descriptions thereof are omitted. In describing the present invention, if it is determined that a detailed description of related prior art could unnecessarily obscure the essence of the present invention, such detailed description is omitted.

[0067] FIG. 1 is a diagram illustrating the configuration of a device for controlling the density difference between cortical bone and cancellous bone within the skull for focused ultrasound treatment according to a preferred embodiment of the present invention.

[0068] As illustrated in FIG. 1, the device according to the present embodiment may include an ultrasonic transducer (100) and a signal modulator (102).

[0069] The ultrasound probe (100) irradiates ultrasound onto the patient's skull, and the signal control unit (102) determines the amplitude and frequency of the ultrasound irradiated from the ultrasound probe (100) so that the ultrasound increases the density of the cancellous bone so that the density of the cancellous bone relative to the density of the cortical bone is 0.5 or higher, while at the same time attenuating the ultrasound before it penetrates the brain region.

[0070] In order to treat essential tremor and Parkinson's disease using focused ultrasound, the density difference between cortical bone and cancellous bone must be reduced. In this embodiment, ultrasound of a predetermined amplitude and frequency is irradiated to increase the density of cancellous bone while controlling the degree of attenuation as described above.

[0071] The ultrasound used to reduce density difference can be one of Low Intensity Pulsed Ultrasound (LIPUS) and Low Intensity Continuous Ultrasound (LICU).

[0072] LICU is a new concept presented in this embodiment and is not commercially available as a product.

[0073] In addition, according to the present embodiment, a rest time is provided between the waveforms of low-intensity pulsed ultrasound and low-intensity continuous ultrasound to reduce heat generation.

[0074] The amplitude and frequency of the ultrasound are not fixed for each patient but can be repeatedly adjusted as the density of the cancellous bone changes. To achieve this, the thickness of the cortical bone and cancellous bone measured by an imaging device, the difference in intensity between the ultrasound irradiated by the ultrasound probe (100) and the ultrasound reflected from the boundary between the cortical bone and the cancellous bone, the frequency of the ultrasound, the known attenuation coefficient of the cortical bone and the cancellous bone, and the attenuation phenomenon formula to which porous elasticity theory is applied are used.

[0075] In addition, the signal control unit (102) according to the present embodiment may be implemented as a computing device including a processor and a memory that executes program instructions executed by the processor.

[0076] Here, the processor may include a CPU (central processing unit) capable of executing computer programs or other virtual machines.

[0077] Memory may include non-volatile storage devices such as fixed hard drives or removable storage devices. Removable storage devices may include Compact Flash Units, USB memory sticks, etc. Memory may also include volatile memory such as various random access memories and may be defined as a computer-readable recording medium.

[0078] Below, the theoretical background of the present embodiment and the process of setting the frequency of the ultrasound are explained in detail.

[0079] Osteoblasts, which generate new bone tissue, respond to low-frequency stimulation. In this case, the movement of water within the bone tissue triggers the stimulation; however, when the frequency increases to high, water movement is almost non-existent due to its inertia. The theoretical background regarding the generation of electric charge in the case of high-frequency stimulation is as follows.

[0080] Bones respond to low-amplitude and high-frequency mechanical stimulation. When low-intensity whole-body vibration therapy (30 Hz, 0.3 g) is provided daily to young women (15–20 years) with low bone density, the low-magnitude mechanical stimulation anabolizes the bone matrix, and the low-magnitude whole-body vibration increases the cross-sectional area of ​​the paravertebral muscle tissue. Quantitative CT image analysis showed that low-intensity whole-body vibration therapy increased the area of ​​the lumbar cancellous bone and the interfemoral cortical bone. Low-magnitude mechanical stimulation prevents bone loss due to disuse caused by suspending the hind legs and increases the strength of the cancellous bone.

[0081] Many researchers have used the concepts of poroelasticity and piezoelectricity to analyze the mechanical properties of cancellous bone and the mechanical transformation of cortical bone, but as in this embodiment, no research has been conducted to date that considers the effects of charge ions on wave propagation through bone or vibration.

[0082] If the term containing charge density is inserted into the equation of porous elasticity theory and solved numerically using the material properties of the cancellous bone, it is as follows.

[0083]

[0084]

[0085]

[0086] Here, N, R, Q, and A are the porous modulus, and u and U represent the displacements of the fluid and solid, respectively.

[0087] variable Is and, here represents the viscosity of the fluid, and Kp is the permeability of the fluid.

[0088] and, is permittivity, ε represents porosity, and Gp represents the correlation coefficient between electric current and electrical potential.

[0089] is charge density, represents electric potential.

[0090] The porous modulus, P=A+N, Q, and R are defined as follows.

[0091]

[0092]

[0093]

[0094] Here, is the bulk modulus of cancellous bone containing porosity, and is the bulk modulus of pure bone tissue (cortical bone), and G is the bulk modulus of the interstitial fluid, and G is the shear modulus of the cortical bone.

[0095] The density used in the above mathematical formula is defined as follows.

[0096]

[0097] ,

[0098]

[0099] Here, the density of the cortical bone, 1960 , and the density of interstitial fluid is 1000 . Bulk modulus of interstitial fluid is set to 2.3 GPa, and the tortuosity t of the cortical bone is calculated from the following equation.

[0100]

[0101] Figure 2 is a diagram illustrating the change in charge density on the surface of cancellous bone trabeculae according to wavenumber and frequency. Figure 2 shows that as the frequency increases, the amount of charge on the surface of the bone tissue increases.

[0102] Ultrasound generates two longitudinal waves (fast compression wave and slow compression wave) in porous materials.

[0103] Charge ions accumulate on the surface of the trabeculae due to fast compression waves (fast waveforms). Charge density increases significantly as the frequency increases and the wavenumber decreases. While slow compression waves (slow waveforms) cause relative motion between the solid bone matrix and the fluid within the pores, fast compression waves appear to cause the charge to exist on the surface of the trabeculae because the solid bone matrix remains stationary along with the fluid.

[0104] The charge generated on the surface of bone tissue by high-frequency stimulation has the following effects on osteoblasts. It is known experimentally that positively charged hydrogels attract a large number of osteoblasts to their surface, and similarly, many osteoblasts can attach to the surface of cancellous bone. Negative charges promote the production of osteopontin, thereby inhibiting the growth of hydroxyapatite crystals; however, interestingly, while negative charges are effective for fracture healing, positive charges have no such effect. Therefore, it is concluded that whether the generated charge is positive or negative, it affects the regeneration of bone tissue.

[0105] In this embodiment, during the process of regenerating bone tissue inside the skull using ultrasound, that is, increasing the density of cancellous bone, the ultrasound frequency range is set so that the ultrasound does not penetrate a part of the brain and stimulate the brain's function, but acts solely on bone tissue generation.

[0106] The relationship between ultrasonic velocities can be expressed by the following equation.

[0107]

[0108] Here is the speed of the ultrasound irradiated from the ultrasound probe (100), and It is the speed of the reflected ultrasound, and ε is the velocity of the transmitted ultrasound. Using the transmitted velocity, the attenuation in the cancellous bone can be calculated.

[0109] The previously known attenuation coefficient of cortical bone is 6.9 and the known damping coefficient of cancellous bone is 9.94 am.

[0110] However, in cortical bone, only a single waveform exists due to low porosity, whereas upon entering cancellous bone with high porosity, both fast and slow waveforms are generated. In this embodiment, since the amplitude of the slow waveform is relatively larger than that of the fast waveform, the attenuation of ultrasound for the slow waveform is primarily considered, which will be described in detail below.

[0111] FIG. 3 is a flowchart of the process for determining ultrasound amplitude and frequency that can increase the density of cancellous bone while preventing penetration of the brain region according to the present embodiment.

[0112] Referring to FIG. 3, the device according to the present embodiment receives the thickness of the patient's cortical bone and cancellous bone measured through an imaging device (step 300).

[0113] Next, the difference in intensity between the ultrasound irradiated from the ultrasound probe (100) and the ultrasound reflected from the interface between the cortical bone and the cancellous bone is measured (step 302).

[0114] The attenuation coefficient of the cortical bone is calculated using the thickness of the cortical bone that the ultrasound can travel back and forth, the difference in intensity between the transmitted and reflected ultrasound, and the ultrasound frequency, which is measured in step 300 (step 304).

[0115] According to the present embodiment, the attenuation coefficient of the cortical bone calculated in step 304 is a previously known 6.9 Check how much of a difference there is, and use that difference to find 9.94, known as the damping coefficient of cancellous bone. The value is corrected (step 306). At this time, a correction factor is calculated by proportionally adjusting the experimentally calculated value to the given value. The correction is made by taking into account the attenuation caused by the reflection coefficient occurring at the interface between the cortical bone and the cancellous bone.

[0116] In step 306, for cancellous bone with porous characteristics, the damping coefficient of the cancellous bone according to the formula based on porous elasticity theory is the given value of 9.94 It is calculated using a relative method after correction by comparison.

[0117] Using the attenuation coefficient of the cancellous bone corrected in step 306, the amplitude and frequency of the ultrasound that can be attenuated in the cancellous bone are determined (step 308).

[0118] According to the present embodiment, to reduce the density difference between cortical bone and cancellous bone, FDA-approved LIPUS (Low Intensity Pulsed Ultrasound) may be used, or Low Intensity Continuous Ultrasound may be used. Low Intensity Continuous Ultrasound is referred to as LICU in this specification.

[0119] Solving porous elasticity theory such as mathematical equations 1 to 3 yields two damping coefficients for cancellous bone, class This results in a value that can be expressed as follows. In this case, the given value is given as a continuous form of ultrasound that takes the form of a continuous sine or cosine.

[0120]

[0121]

[0122] Here is the speed of a fast waveform, and represents the speed of a slow waveform. In porous materials, two waveforms are generated because the solid and liquid parts are combined.

[0123] Due to the reason that slow waveform signals have a larger amplitude than fast waveforms, the following explanation focuses on slow waveform speeds.

[0124] The values ​​expressed in mathematical formulas 10 and 11 are as follows.

[0125]

[0126]

[0127]

[0128] Here

[0129] am.

[0130] According to the present embodiment, the porosity of the cancellous bone is obtained by using the velocity of the slow waveform calculated using Equation 11 and the actual velocity of the slow waveform of Equation 13. The amplitude and frequency of the ultrasound are determined such that the ratio of the density of the cortical bone to the density of the cancellous bone is 0.5 or less (assuming the porosity of the cortical bone is 0), that is, the ratio of the density of the cortical bone to the density of the cancellous bone is 0.5 or more.

[0131] According to the present embodiment, the amplitude and frequency of the initial ultrasound are determined through the patient's cortical bone attenuation coefficient in the initial state, and this is applied to the patient.

[0132] As in step 306 of Fig. 3, when using the damping coefficient of the corrected cancellous bone and Equation 11, the velocity of the slow waveform is calculated, and when the velocity of the slow waveform is applied to Equation 13, porous It can be calculated. Porosity of cancellous bone Determine the amplitude and frequency of the ultrasound by checking the degree of change.

[0133] In the case of LIPUS, rather than providing a continuous, repetitive ultrasound waveform, it sends pulsed ultrasound and then provides another pulsed ultrasound waveform after a short time. In this case, using a Fourier series, the repetitive pulsed ultrasound waveform can be represented in the form of sine and cosine. However, the resulting value is not as simple as the equation above and has several different wave numbers. Nevertheless, while the frequency changes for bone tissue of the same material when the wave number changes, the transmission speed remains the same because it is the same material. Therefore, it can be assumed that the above equation can also be applied to LIPUS.

[0134] In the case of cortical bone, the bulk modulus having porosity The bulk modulus of bone tissue If we assume that it is the same, then the porous modulus P, Q, and R in mathematical equations 4 through 6 become very simple. In the case of cancellous bone, the physical properties resulting from porosity can be obtained using the rule of mixture described below.

[0135] The bulk modulus of cancellous bone according to the ratio using a proportional equation ε is the bulk modulus of bone tissue, in this case, the bulk modulus of cortical bone and the bulk modulus of interstitial fluid It can be represented as follows.

[0136]

[0137] The following describes the process of calculating the frequency required for bone tissue regeneration.

[0138] As shown in Figure 2, it was confirmed that increasing the frequency of ultrasound generates charge density, which can induce the regeneration of bone tissue.

[0139] Therefore, using the attenuation formula described above, it is possible to set the frequency that induces bone tissue regeneration within the cancellous bone after the ultrasound passes through the cortical bone outside the skull. In this process, it is essential to consider that the ultrasound must attenuate before entering the brain region. Generally, since attenuation becomes stronger as the frequency increases, the frequency range can be determined using the attenuation formula for cancellous bone. However, as higher frequencies generate heat, it is necessary to adjust the usage time.

[0140] When regeneration of cancellous bone tissue is achieved using LIPUS or LICU, frequency recalibration using imaging devices is required due to the increase in density (generally, a decrease in porosity). Otherwise, the reduced porosity would allow ultrasound to penetrate into the brain region.

[0141] The speed of the ultrasound irradiated from the ultrasound probe (100) and the bulk modulus of cortical bone The method for calculating is as follows.

[0142] Generally, when using nanoindentation, the Young's modulus of bone tissue It can be obtained. Young's modulus of the cranial cortical bone at ages 51 and 77. It is known to be 13 GPa.

[0143] The following equation By using this, the initial velocity of the ultrasound irradiated onto the ultrasonic probe (100) can be determined. The relationship between Young's modulus and the bulk modulus, Calculate the bulk modulus of cortical bone using [this].

[0144] Generally, the Poisson ratio of cortical bone in nano-indentation experiments It is considered as. At this time, the density of the cortical bone, It is measured using bone densitometry. The reflection coefficient occurring at the boundary between cortical bone and cancellous bone is calculated as follows. This reflection coefficient represents the rate at which the amplitude of the ultrasound is attenuated by reflection at the boundary.

[0145]

[0146] Using this, the speed of ultrasound reflected from the boundary It becomes possible to express it as. is the density of cancellous bone, and is the density of compact bone. However, in the case of the transmission coefficient, the value varies depending on whether the amplitude of the ultrasound is displacement or stress or pressure. In the case of displacement, it is as follows.

[0147]

[0148] When the amplitude is stress or pressure, it is as follows.

[0149]

[0150] The transmission coefficient also represents the rate at which the amplitude of ultrasound decreases as it passes through the interface.

[0151] Figure 4 shows the bone tissue structure of the skull.

[0152] Generally, the trabecular meshwork of cancellous bone is aligned with the thickness direction of the skull. This indicates that the LIPUS ultrasound method promotes bone tissue regeneration according to the method of the present embodiment, and theoretically explains that bone tissue regeneration is also promoted when using a continuous ultrasound waveform (LICU).

[0153] According to the present embodiment, a helmet or safety helmet is molded so that an ultrasound probe (100) can be inserted into the location to be treated using HIFU. Then, a solid gel for ultrasound is attached to the inside, and the helmet is placed on the patient's head to irradiate ultrasound (LIPUS or LICU) for a certain period of time to regenerate the bone tissue of the cancellous bone within the skull, thereby reducing the density difference between the cortical bone and the cancellous bone. Clinically, when the density difference between the cortical bone and the cancellous bone becomes 0.5 or less, treatment for hand tremors or Parkinson's disease using HIFU can be performed.

[0154] The embodiments of the present invention described above are disclosed for illustrative purposes only, and those skilled in the art with ordinary knowledge of the present invention may make various modifications, changes, and additions within the spirit and scope of the present invention, and such modifications, changes, and additions should be considered to fall within the scope of the following claims.

Claims

Claim 1 A density difference control device comprising: an ultrasound probe that irradiates ultrasound, as a device for controlling the density difference between cortical bone and cancellous bone for focused ultrasound treatment; and a signal control unit that controls the amplitude and frequency of the ultrasound so that the ultrasound increases the density of the cancellous bone so that the density of the cancellous bone relative to the density of the cortical bone becomes 0.5 or greater, and the ultrasound is attenuated before penetrating a brain region. Claim 2 A density difference control device according to claim 1, wherein the ultrasound comprises one of Low Intensity Pulsed Ultrasound (LIPUS) and Low Intensity Continuous Ultrasound (LICU). Claim 3 In claim 1, the signal control unit is a density difference control device that determines the amplitude and frequency of the ultrasound using the thickness of the cortical bone and cancellous bone measured by an imaging device, the difference in intensity between the ultrasound irradiated by the ultrasound probe and the ultrasound reflected from the interface between the cortical bone and the cancellous bone, the frequency of the ultrasound, a known attenuation coefficient of the cortical bone and the cancellous bone, and an attenuation phenomenon formula to which porous elasticity theory is applied. Claim 4 In paragraph 3, the signal control unit calculates the attenuation coefficient of the cortical bone using the thickness of the cortical bone, the intensity difference, and the frequency of the ultrasound, corrects the previously known attenuation coefficient of the cancellous bone using the difference between the calculated attenuation coefficient of the cortical bone and the previously known attenuation coefficient of the cortical bone and the thickness of the cancellous bone, and applies the corrected attenuation coefficient of the cancellous bone to the attenuation phenomenon formula to determine the amplitude and frequency of the ultrasound so that the ultrasound transmitted through the cancellous bone is extinguished within the cancellous bone. Claim 5 In paragraph 4, the signal modulator is a density difference modulator that determines the amplitude and frequency of the ultrasound using the attenuation coefficient formula defined below and the attenuation coefficient of the corrected cancellous bone.[Mathematical Formula] Here, is the attenuation factor of a slow waveform (unit is 1 / m), and when converted to decibels (dB), it is converted to a dimensionless logarithmic value, which is the definition of dB. is the frequency (Hz), is the velocity of ultrasound transmitted into the cancellous bone, and is the velocity of the slow waveform in the porous material calculated through the above damping phenomenon formula. Claim 6 In paragraph 5, the above porous elasticity theory is a density difference control device expressed by the following mathematical formula.[Mathematical Formula] [Mathematical Formula] [Mathematical Formula] Here, N, R, Q, and A are the porous elastic modulus, and u and U are the displacement and variable of the fluid and solid, respectively. Is , here ε is the viscosity of the fluid, and Kp is the permeability of the fluid, is permittivity, ε represents porosity, Gp represents the correlation coefficient between electric current and electrical potential, and is charge density, is electric potential Claim 7 In Clause 6, the density difference control device, P=A+N, Q, and R, is defined as follows. [Mathematical Formula] [Mathematical Formula] [Mathematical Formula] Here, is the bulk modulus of cancellous bone containing porosity, and is the bulk modulus of pure bone tissue, ε is the bulk modulus of the interstitial fluid, and G is the shear modulus of the bone tissue. Claim 8 In claim 7, the actual speed and imaginary transmission speed of the slow waveform included in the above damping coefficient mathematical formula are defined as follows in the density difference control device.[Mathematical Formula] [Mathematical Formula] Here lim Claim 9 In claim 8, the porosity of the cancellous bone using the velocity of the slow waveform calculated using the above damping coefficient formula and the actual velocity of the above slow waveform A density difference control device in which the amplitude and frequency of the ultrasound are determined so that α becomes 0.5 or less. Claim 10 In claim 9, the density difference control device wherein the bulk modulus of the above-mentioned cancellous bone is calculated using the following mathematical formula.[Mathematical Formula] Claim 11 In Clause 10, the density difference control device wherein the initial velocity of the above-mentioned ultrasound is calculated using the following mathematical formula. [Mathematical Formula] is the Young's modulus of the cortical bone, is the density of cortical bone measured through a bone density test. Claim 12 In Clause 11, the density difference control device wherein the reflection coefficient, which is the ratio at which the amplitude of the ultrasound is attenuated, is defined by the following mathematical formula.[Mathematical Formula] Here is the speed of ultrasound irradiated from the ultrasound probe, is the speed of the transmitted ultrasound, is the density of cancellous bone, and is the density of compact bone. Claim 13 In Clause 12, the transmission coefficient of the above ultrasound is defined by the following mathematical formula when the amplitude is displacement [Mathematical Formula] A density difference control device defined by the following mathematical formula when the amplitude is stress or pressure.[Mathematical Formula] Claim 14 A density difference control device for controlling the density difference between cortical bone and cancellous bone within the skull for focused ultrasound treatment, comprising: a processor; and a memory connected to the processor, wherein the memory stores program instructions executed by the processor to calculate the attenuation coefficient of the cortical bone using the thickness of the cortical bone, the difference in intensity between the ultrasound irradiated from the ultrasound probe and the ultrasound reflected from the boundary between the cortical bone and the cancellous bone, and the frequency of the ultrasound, correct the attenuation coefficient of the cancellous bone using the difference between the calculated attenuation coefficient of the cortical bone and a previously known attenuation coefficient of the cortical bone and the thickness of the cancellous bone, and apply the corrected attenuation coefficient of the cancellous bone to the attenuation phenomenon formula so that the ultrasound increases the density of the cancellous bone so that the density of the cancellous bone relative to the density of the cortical bone becomes 0.5 or greater, and to determine the amplitude and frequency of the ultrasound so that the ultrasound is attenuated before penetrating the brain region. Claim 15 A density difference correction method for controlling the density difference between cortical bone and cancellous bone within the skull for focused ultrasound treatment, comprising: a step of calculating a cortical bone attenuation coefficient using the thickness of the cortical bone, the difference in intensity between ultrasound irradiated from an ultrasound probe and ultrasound reflected from the boundary between the cortical bone and the cancellous bone, and the frequency of the ultrasound; a step of correcting a known attenuation coefficient of the cancellous bone using the difference between the calculated attenuation coefficient of the cortical bone and a known attenuation coefficient of the cortical bone and the thickness of the cancellous bone; and a step of determining the amplitude and frequency of the ultrasound so that the ultrasound increases the density of the cancellous bone so that the density of the cancellous bone relative to the density of the cortical bone becomes 0.5 or greater, and the ultrasound attenuates before penetrating the brain region.

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