JP2006230504A - Method for measuring intracranial pressure and system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a precise and safe method for measuring an intracranial pressure to solve problems caused by a conventional technique, and a system. <P>SOLUTION: The method for measuring an intracranial pressure which is applied to an intracranial region where a plurality of micro-bubbles are formed by injecting a contrast medium includes a step of (A) emitting ultrasound emission signals in a certain frequency band to the region, a step of (B) detecting reflected signals from the micro-bubbles, a step of (C) subjecting the reflected signals to a spectral analysis and acquiring a low-frequency response with a bandwidth close to the bandwidth of the emission signals, a step of (D) calculating a resonance frequency of the micro-bubbles by utilizing characteristics of the low-frequency response, and a step of (E) calculating dimensions of the micro-bubbles and a pressure value of the region based on the resonance frequency and the properties of the contrast medium. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for measuring intracranial pressure and, more particularly, to a non-intrusive intracranial pressure measuring method and system using an ultrasonic contrast agent and signal processing technology.

  When suffering from diseases such as traumatic intracranial hematoma, intracranial tumor, hemorrhagic cerebrovascular disorder, meningitis, congenital cranial malformation, intracranial pressure increases and brain membranes, blood vessels or nerves are compressed, headache, vomiting, etc. In addition to the above symptoms, optic disc edema can lead to blindness. Therefore, it goes without saying that it is important to detect and treat an increase in intracranial pressure at an early stage.

  Intracranial pressure is measured clinically by referring to symptoms such as headache and vomiting, and often by a precise measurement method. In general, (1) Cerebrospinal fluid is obtained and analyzed by lumbar puncture, (2) Examination of cerebral indentation, suture detachment, intracranial thinning, increased Turkish fistula, etc. by X-ray imaging, or (3) Methods such as brain ultrasonography are used.

  Among them, (1) is an invasive measurement and there are problems of infection and patient adaptability, and (2) is a non-invasive measurement, but the effect is not constant. The brain ultrasonography (3) has a drawback that the response signal is weak because of the shielding by the skull.

  In order to improve the ultrasonic examination, a method for inspecting by injecting a contrast medium into blood or lymph has been developed. The method enhances signal quality by using microbubbles to enhance echo.

  Please refer to FIG. It is analyzed that the echo of echocardiography using the contrast agent has a fundamental response 11, a second harmonic response 12, and a subharmonic response 13. The second harmonic response 12 and the subharmonic response 13 exhibit a non-linear response to microbubble generation, and higher sound pressure is required to generate microbubbles. Of these, the sound pressure required by the subharmonic response 13 is the highest.

  Since basic responses can also be found in the bloodstream or surrounding tissues, they cannot be used for comparison and discrimination.

  The second harmonic response has a high frequency and is significantly attenuated when it passes through the skull. In addition, in the case of mammals, the second harmonic response can be found from the tissue, so it is not suitable for distinguishing blood, lymph and surrounding tissues.

  For subharmonic responses, the US Pat. No. 6,302,845, in conjunction with conventional ultrasound systems, lists methods for determining heart or portal vein pressure using contrast agents. In this patent, the pressure value is determined based on the difference in subharmonic response due to microbubbles associated with various pressures. However, if the sound pressure is increased to generate a subharmonic response, the microbubbles are likely to burst. Therefore, if this method is used for measuring the intracranial pressure, the safety of the examination is not without problems.

  In order to solve the above-mentioned problems, an object of the present invention is to provide a precise and safe method and system for measuring intracranial pressure.

  The present invention provides an intracranial pressure measurement method that is performed on a region inside the skull in which a plurality of microbubbles are formed by contrast medium injection. The method includes (A) emitting an ultrasonic emission signal in a certain frequency band in the region, (B) detecting an echo signal from a microbubble, (C) performing spectrum analysis on the echo signal, Obtains a low-frequency response close to that of the emission signal, (D) calculates the resonant frequency of the microbubble using the characteristics of the low-frequency response, and (E) microbubbles based on the resonant frequency and the nature of the contrast agent Calculating the dimensions and pressure values of the region.

  The present invention further provides an intracranial pressure measurement system for an internal region of the skull in which a plurality of microbubbles are formed by contrast medium injection. The system includes a launch module that emits an ultrasonic emission signal in a certain frequency band in the region, a reception module that detects an echo signal from a microbubble, and a signal processing module connected to the reception module. Among them, the signal processing module performs spectrum analysis on the reverberant signal, and obtains a low frequency response whose bandwidth is close to that of the emission signal, and the resonance frequency of the microbubble using the characteristics of the low frequency response. And a pressure calculation unit for calculating the microbubble size and the region pressure value based on the resonance frequency and the properties of the contrast agent.

  The present invention further provides an ultrasonic pressure measurement method performed on a target region in which a plurality of microbubbles are formed by contrast medium injection. The method includes (A) emitting an ultrasonic emission signal in a certain frequency band in a target area, (B) detecting an echo signal from a microbubble, (C) performing spectrum analysis on the echo signal, Obtains a low-frequency response close to that of the emission signal, (D) calculates the resonant frequency of the microbubble using the characteristics of the low-frequency response, and (E) microbubbles based on the resonant frequency and the nature of the contrast agent Calculating the dimensions and the pressure value of the target area.

  The present invention further provides an ultrasonic pressure measurement system for a target region in which a plurality of microbubbles are formed by contrast medium injection. The system includes a launch module that emits an ultrasonic emission signal in a fixed frequency band in a target area, a reception module that detects an echo signal from a microbubble, and a signal processing module connected to the reception module. Among them, the signal processing module performs spectrum analysis on the reverberant signal, and obtains a low frequency response whose bandwidth is close to that of the emission signal, and the resonance frequency of the microbubble using the characteristics of the low frequency response. And a pressure calculation unit for calculating the microbubble size and the region pressure value based on the resonance frequency and the properties of the contrast agent.

  The method and apparatus according to the present invention provides a means for measuring the intracranial pressure that minimizes the shielding of the skull, prevents the bursting of microbubbles by taking only the low frequency response of the reverberation, and is safer, more accurate and more economical than the prior art. provide.

  In order to detail the features of such a method and apparatus, a specific example is given and described below with reference to the drawings.

  Please refer to FIG. In the method according to the present invention, a contrast medium is injected by intravenous injection to generate microbubbles in the blood in the internal region of the skull, and thus the pressure in the region is measured. The intracranial pressure measurement system includes an ultrasonic probe 21, a firing module 22 connected to the ultrasonic probe 21, a receiving module 23, and a signal processing module 20 connected to the receiving module 23. The signal processing module 20 includes a filter unit 24, a low frequency acquisition unit 25, a resonance frequency calculation unit 26, and a pressure calculation unit 27.

  Please refer to FIG. The intracranial pressure measurement method according to the present invention is as follows.

  Step 31: The firing module 22 generates a drive signal and transmits it to the ultrasonic probe 21. The ultrasonic probe 21 is in contact with any part of the head.

  Step 32: The ultrasonic probe 21 generates an ultrasonic emission signal in response to the drive signal. The firing signal passes through the skull and reaches the blood vessels in the skull. The fire signal does not have to be a high sound pressure, and its center frequency can be 2-10 MHz in general and the signal bandwidth can be 10-40% of the center frequency. In this embodiment, the center frequency is 3.25 MHz, and the bandwidth is 20% of the center frequency.

  Step 33: The ultrasonic probe 21 detects a microbubble echo signal and transmits it to the receiving module 23.

  Step 34: The receiving module 23 transmits the reverberation signal to the filter unit 24 of the signal processing module 20 and filters it to improve the quality of the reverberation signal.

  Step 35: Refer to FIG. The low frequency acquisition unit 25 receives the echo signal from the filter unit 24 and performs spectrum analysis. Based on the frequency distribution of the reverberant signal, a basic response 41 corresponding to the center frequency and bandwidth of the emission frequency and a low-frequency response 42 close to a direct current portion are acquired, and a low-frequency response 42 is acquired using a bandpass filter. The bandwidth of the low frequency response 42 is close to the bandwidth of the basic response 41.

  Step 36: The resonance frequency calculation unit 26 of the signal processing module 20 calculates the resonance frequency of the microbubble using the following equation 1 using the bandwidth, strength, etc. of the low frequency response as parameters.

  Formula 1

そのうちＰ＝ｐ_Ｌ／ｐ_Ｆ（ｐ_Ｌ：低周波応答強度、ｐ_Ｆ：基本応答強度ピーク値）、即ち正規化された低周波応答強度である。

Among them, P = p _L / p _F (p _L : low frequency response intensity, p _F : basic response intensity peak value), that is, normalized low frequency response intensity.

  p: Launch sound pressure

（ｆ_０：共振周波数、Δｆ：帯域幅）
Ｂｅ＝Δｆ／ｆ_ｃ（ｆ_ｃ：基本応答の中心周波数）、即ち正規化された低周波応答帯域幅である。

式１によって図５のような共振周波数―帯域幅関係図を作成することができる。図において横軸は共振周波数ｆ_０を示し、その単位はＭＨｚであり、縦軸は正規化された帯域幅Ｂｅを示す。閉鎖的な等高曲線は正規化強度Ｐを示す。

(F ₀ : resonance frequency, Δf: bandwidth)
_{Be = Δf / f c (f} c: the center frequency of the fundamental response), i.e. a normalized low frequency response band width.

The resonance frequency-bandwidth relationship diagram as shown in FIG. In the figure, the horizontal axis indicates the resonance frequency f _0, the unit is MHz, and the vertical axis shows the bandwidth Be normalized. A closed contour curve shows the normalized strength P.

  According to FIG. 5, when the bandwidth is 20% of the center frequency, the resonance frequency of the microbubble can be calculated from the intensity of the low frequency response 42 of the echo.

Step 37: The pressure calculation unit 27 of the signal processing module 20 calculates the size of the microbubble using the following equation 2 according to the resonance frequency calculated in Step 36.
Formula 2

そのうちｆ_０は共振周波数を示し、その単位はＭＨｚであり、Ｒ_０はマイクロバブルの直径を示し、その単位はμｍである。

Of these, f ₀ represents the resonance frequency, the unit of which is MHz, R ₀ represents the diameter of the microbubble, and the unit thereof is μm.

Equation 2 is due to the nature of the contrast agent. If the contrast agent listed in this example is used, the product of the diameter of the microbubbles and the resonance frequency is equal to 3.2. The value of this product varies depending on the type of contrast agent.

Step 38: Since the size of the microbubble changes depending on the environmental pressure, the pressure calculation unit 27 of the signal processing module 20 calculates the pressure value in the intracranial region based on the size of the microbubble calculated in step 37.

  In summary, the intracranial pressure measuring method and system according to the present invention has the following features.

  (1) Since the method according to the present invention is a non-invasive measurement, there is no problem of postoperative wound or infection, and it is suitable for all types of patients.

  (2) The method according to the present invention requires no other auxiliary equipment, and can be measured only by using a conventional ultrasonic system.

  (3) Since only the low frequency response is taken, the skull is shielded to the minimum. Therefore, the ultrasonic probe according to the present invention is not limited to the conventional orbit and temple, and can be used for any part of the head.

  (4) Since the low frequency response of reverberation occurs only by low sound pressure emission, there is no problem of bursting microbubbles, and safety can be guaranteed.

  (5) Taking the low-frequency response of reverberation is not only easier to distinguish blood flow and surrounding tissue than the conventional fundamental response and second-harmonic response, but also has a low visible range due to its low frequency. Deeper than before. Compared with the subharmonic response, the microbubble maintenance period is long, which is advantageous for observation.

  Note that the contrast agent is not limited to being injected into a blood vessel, and even if it is injected into the lymph through muscles, the pressure in the region through which the lymph passes can be measured. Furthermore, since the low frequency response used by the present invention does not require high sound pressure and has a very low attenuation rate, it can be used for measuring the pressure of mammalian hearts and portal veins. It can also be used for building and marine fish detection.

  The above is a preferred embodiment of the present invention and does not limit the scope of the present invention. Therefore, any modifications or changes that can be made by those skilled in the art, which are made within the spirit of the present invention and have an equivalent effect on the present invention, shall belong to the scope of the claims of the present invention. To do.

  As described above, the present invention provides an intracranial pressure measuring means that is safer, more accurate and more economical than the prior art.

It is a spectrum figure of the ultrasonic echo signal by a prior art. It is a block diagram of the intracranial pressure measuring system by this invention. It is a flowchart of the intracranial pressure measuring method by this invention. It is a spectrum figure of the ultrasonic echo signal by this invention. It is a related figure of the resonance frequency of a micro bubble, the bandwidth of an echo signal, and intensity.

Explanation of symbols

11, 41 Basic response 12 Second harmonic response 13, 42 Subharmonic response 20 Signal processing module 21 Ultrasonic probe 22 Emitting module 23 Reception module 24 Filter unit 25 Low frequency acquisition unit 26 Resonance frequency calculation unit 27 Pressure calculation unit

Claims (24)

A method for measuring intracranial pressure with respect to an intracranial region formed by a plurality of microbubbles by contrast medium injection,
(A) emitting an ultrasonic emission signal in a certain frequency band in the region;
(B) Detect echo signals from microbubbles,
(C) perform spectral analysis on the reverberant signal to obtain a low frequency response with a bandwidth close to that of the launch signal;
(D) Calculate the resonant frequency of the microbubble using the characteristics of the low frequency response,
(E) A method for measuring intracranial pressure, comprising calculating a microbubble size and a region pressure value based on a resonance frequency and a property of a contrast agent.   2. The intracranial pressure measuring method according to claim 1, wherein the step (D) further calculates the resonant frequency of the microbubbles using the relational expression using the bandwidth and intensity of the low frequency response as parameters.   3. The method of measuring intracranial pressure according to claim 2, wherein the bandwidth parameter is normalized by dividing the bandwidth by the center frequency of the firing signal.   3. The method of measuring intracranial pressure according to claim 2, wherein the intensity parameter is normalized by dividing the low frequency response by the maximum intensity of the firing signal.   2. The intracranial pressure measurement method according to claim 1, wherein the step (E) calculates the size of the microbubble based on the relationship between the resonance frequency and the size of the microbubble under the condition of the contrast agent.   6. The intracranial pressure measurement method according to claim 5, wherein a product of the resonance frequency and the one-dimensional dimension of the microbubble is a constant value. An intracranial pressure measurement system for an intracranial region formed by a plurality of microbubbles by contrast medium injection,
A launch module that emits an ultrasound firing signal in a certain frequency band in the region;
A receiving module that detects echo signals from microbubbles;
A signal processing module connected to the receiving module, of which the signal processing module is
A low frequency acquisition unit that performs spectral analysis on the reverberant signal and acquires a low frequency response with a bandwidth close to that of the emission signal;
A resonance frequency calculation unit that calculates the resonance frequency of the microbubbles using the characteristics of the low frequency response;
An intracranial pressure measurement system comprising: a pressure calculation unit for calculating a microbubble size and a region pressure value based on a resonance frequency and a property of a contrast medium.   8. The intracranial pressure measurement system according to claim 7, wherein the resonance frequency calculation unit further calculates a resonance frequency of the microbubble using a relational expression using the bandwidth and intensity of the low frequency response as parameters.   9. The intracranial pressure measurement system of claim 8, wherein the bandwidth parameter is normalized by dividing the bandwidth by the center frequency of the firing signal.   9. The intracranial pressure measurement system of claim 8, wherein the intensity parameter is normalized by dividing the low frequency response by the maximum intensity of the firing signal.   8. The intracranial pressure measurement system according to claim 7, wherein the pressure calculation unit calculates the size of the microbubble based on the relationship between the resonance frequency and the size of the microbubble under the condition of the contrast agent.   12. The intracranial pressure measurement system according to claim 11, wherein the product of the resonance frequency and the one-dimensional dimension of the microbubble is a constant value. An ultrasonic pressure measurement method for a target region formed by a plurality of microbubbles by contrast medium injection,
(A) emitting an ultrasonic emission signal in a certain frequency band in a target area;
(B) Detect the echo signal from the microbubble,
(C) perform spectral analysis on the reverberant signal to obtain a low frequency response with a bandwidth close to that of the launch signal;
(D) Calculate the resonant frequency of the microbubble using the characteristics of the low frequency response,
(E) A method for measuring an ultrasonic pressure characterized by including a step of calculating a microbubble size and a pressure value in a target region based on a resonance frequency and a property of a contrast agent.   14. The ultrasonic pressure measuring method according to claim 13, wherein the step (D) further calculates the resonant frequency of the microbubble using a relational expression using the bandwidth and intensity of the low frequency response as parameters.   The method of claim 14, wherein the bandwidth parameter is normalized by dividing the bandwidth by the center frequency of the firing signal.   The method of claim 14, wherein the intensity parameter is normalized by dividing the low frequency response by the maximum intensity of the firing signal.   14. The ultrasonic pressure measuring method according to claim 13, wherein the step (E) calculates the size of the microbubble based on the relationship between the resonance frequency and the size of the microbubble under the condition of the contrast agent.   18. The ultrasonic pressure measuring method according to claim 17, wherein a product of the resonance frequency and the one-dimensional dimension of the microbubble is a constant value. An ultrasonic pressure measurement system for a target region formed by a plurality of microbubbles by contrast medium injection,
A launch module that emits an ultrasound firing signal in a constant frequency band in a target area;
A receiving module that detects echo signals from microbubbles;
A signal processing module connected to the receiving module, of which the signal processing module is
A low frequency acquisition unit that performs spectral analysis on the reverberant signal and acquires a low frequency response with a bandwidth close to that of the emission signal;
A resonance frequency calculation unit that calculates the resonance frequency of the microbubbles using the characteristics of the low frequency response;
An ultrasonic pressure measurement system comprising a pressure calculation unit for calculating a microbubble size and a region pressure value based on a resonance frequency and a property of a contrast agent.   The ultrasonic pressure measurement system according to claim 19, wherein the resonance frequency calculation unit further calculates a resonance frequency of the microbubbles using a relational expression using the bandwidth and intensity of the low frequency response as parameters.   21. The ultrasonic pressure measurement system of claim 20, wherein the bandwidth parameter is normalized by dividing the bandwidth by the center frequency of the firing signal.   21. The ultrasonic pressure measurement system of claim 20, wherein the intensity parameter is normalized by dividing the low frequency response by the maximum intensity of the firing signal.   The intracranial pressure measurement system according to claim 19, wherein the pressure calculation unit calculates the size of the microbubble based on the relationship between the resonance frequency and the size of the microbubble under the condition of the contrast agent.   The ultrasonic pressure measurement system according to claim 23, wherein a product of the resonance frequency and the one-dimensional dimension of the microbubble is a constant value.

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