Transcranial ultrasonic multi-frequency acoustic holographic lens design method and system

Abstract

The invention discloses a transcranial ultrasonic multi-frequency acoustical holographic lens design method and system. The method comprises the following steps: setting a plurality of different focus points; using a k-wave toolbox in Matlab, respectively setting a plurality of different focus points as sound sources by using a time reversal method, respectively adopting a plurality of driving frequencies to carry out simulation experiments, capturing the phase of the plane where the ultrasonic transducer is placed, and obtaining a plurality of acoustic holograms; according to the method, effective information of a plurality of acoustical holograms is extracted and integrated into a multi-frequency acoustical hologram, and after a transcranial multi-frequency acoustical hologram is obtained, phase information of the multi-frequency acoustical hologram is extracted and converted into the height of each pixel of the acoustical hologram lens. Multi-frequency transcranial focusing based on the multi-frequency acoustical holographic lens is realized by extracting effective information of a plurality of acoustical holographic lenses which are focused at different positions and have different working frequencies and integrating the effective information into one multi-frequency acoustical holographic lens, and corresponding focuses are reconstructed on a focusing plane according to different driving frequencies, so that flexibility in transcranial focusing is realized, and the focusing precision is improved. The application potential is improved.

Description

Technical Field

[0001] The present invention belongs to the field of medical imaging technology, and in particular relates to a transcranial ultrasonic multi-frequency acoustic holographic lens design method and system. Background Art

[0002] Transcranial focused ultrasound has the advantages of being non-invasive and having a high penetration depth, so it is widely used in the biomedical field. However, when ultrasound is focused in a non-invasive way, the sound waves need to pass through the skull. Due to the complexity of the material and structure of the skull itself, it will cause very strong ultrasound scattering and attenuation, causing serious distortion and distortion of the sound field passing through the skull. To solve this problem, a sound field control technology based on ultrasonic holographic lenses has emerged. At present, this technology has been able to reversibly open the blood-brain barrier in the skull of mice to control drug delivery, and can focus on specific areas in an in vitro human skull model, which has great potential in practical applications. However, the existing transcranial focusing methods based on acoustic holographic lenses still face application problems. A single acoustic holographic lens can often only store and reconstruct a single sound field, which lacks flexibility in practical application scenarios. Summary of the invention

[0003] In order to solve the above problems, the purpose of the present invention is to provide a transcranial ultrasound multi-frequency acoustic holographic lens design method and system, by extracting effective information from multiple acoustic holographic lenses with different working frequencies focused on different positions, and integrating it into a multi-frequency acoustic holographic lens, thereby realizing multi-frequency transcranial focusing based on a single multi-frequency acoustic holographic lens. The multi-frequency acoustic holographic lens designed and manufactured based on the method proposed in the present invention can reconstruct the corresponding focus on the focusing plane according to different driving frequencies, thereby improving the flexibility of the multi-frequency acoustic holographic lens in the application of transcranial focusing and enhancing its application potential.

[0004] The technical solution provided by the present invention is: a method for designing a transcranial ultrasound multi-frequency acoustic holographic lens, comprising the following steps:

[0005] Step S1, setting a plurality of different focusing points;

[0006] Step S2, using the k-wave toolbox in Matlab, using the time inversion method to set the multiple different focal points as sound sources respectively, using multiple driving frequencies to perform simulation experiments respectively, capturing the phase at the plane where the ultrasonic transducer is placed, and obtaining multiple acoustic holograms;

[0007] Step S3, extracting effective information of multiple acoustic holograms, integrating them into a multi-frequency acoustic hologram, and after obtaining the transcranial multi-frequency acoustic hologram, extracting the phase information of the multi-frequency acoustic hologram and converting it into the height of each pixel of the acoustic holographic lens.

[0008] Preferably, step S1 further comprises:

[0009] First input or select the basic parameters of the acoustic lens including the size, shape and material properties of the lens in the software, and set two different focusing points T1 and T2.

[0010] Preferably, step S2 further comprises:

[0011] The k-wave toolbox was used in Matlab to simulate ultrasonic propagation. The time inversion method was used to set the multiple different focal points as sound sources. The emitted ultrasonic driving frequencies were 1 MHz and 2 MHz, respectively. The phases at the holographic surface were captured to obtain multiple acoustic holograms, where the grid pixel size was 250 um and the Courant number was set to 0.2.

[0012] Preferably, step S3 extracts effective information of the plurality of acoustic holograms and integrates them into a multi-frequency acoustic hologram H(x,y) further comprises:

[0013] Define the cost function:

[0014] C=E(|p f (x,y)|)-α(std(|p f (x,y)|))-βS

[0015]

[0016] Among them, E(|p f (x,y)|) is the average pressure value received on the holographic surface under the preset frequency drive, std(|p f (x,y)|) is the standard deviation of the pressure value received on the holographic surface under the preset frequency drive, S is the smoothing term obtained by the second-order accurate finite difference approximation of the Laplace operator, and α and β are weight parameters;

[0017] Initialize the multi-frequency acoustic hologram H(x,y) to 0, traverse each pixel value in turn from the beginning, assign a value of the corresponding pixel of the multiple acoustic holograms to each pixel value to maximize the cost function in the pixel point, and then repeat this operation until all pixels are updated;

[0018] The iteration is repeated and terminated when the number of pixels changed compared to the previous iteration is less than 0.5% of the total pixels on the surface.

[0019] Preferably, step S3 extracts the effective information of the plurality of acoustic holograms and integrates them into a multi-frequency acoustic hologram H(x,y) further comprises:

[0020] In the initial iteration, β is set to 0, and β is updated after each iteration so that E(|p n|)=-0.5βS, the variable α is always set to 0.3. After obtaining the transcranial multi-frequency acoustic hologram, the following formula is used to convert the extracted phase information into the height of each pixel of the acoustic holographic lens:

[0021] h(i,j)=w(i,j).c water .c lens / 2πf.(c lens -c water )

[0022] Where w(i,j) is the phase corresponding to pixel (i,j), c water and c l ens is the speed of sound in water and in the holographic lens material, f is the average of the two frequencies set, and the acoustic holographic lens is finally obtained.

[0023] Preferably, the method further comprises step S4, performing a transcranial focusing simulation experiment based on the multi-frequency acoustic hologram, and comparing the obtained focus with the multiple different focus points:

[0024] In the simulation, the distance between the focusing plane and the plane where the ultrasonic transducer is located is 50 mm. The skull phantom is placed between the focusing plane and the ultrasonic transducer, 10 mm away from the focusing plane. The focus of the multi-frequency acoustic holographic lens after reconstructing is obtained on the focusing plane by exciting with different driving frequencies, and the PSNR between the focal position of the multi-frequency acoustic holographic lens and the multiple different focusing points is compared.

[0025] Preferably, step S4 further includes:

[0026] The calculation formula for the evaluated PSNR is:

[0027]

[0028] Where MAX represents the maximum value of the image pixel, and MSE represents the mean square error between the reconstructed focus and the target focus.

[0029] Based on the same concept, the present invention also provides a transcranial ultrasound multi-frequency acoustic holographic lens design system, comprising:

[0030] A reading module, used for acquiring a plurality of different focus points that are set;

[0031] A phase information capture module is used to use the k-wave toolbox in Matlab, use the time inversion method to set the multiple different focal points as sound sources respectively, use multiple driving frequencies to perform simulation experiments respectively, capture the phase at the plane where the ultrasonic transducer is placed, and obtain multiple acoustic holograms;

[0032] The multi-frequency information synthesis module is used to extract effective information of multiple acoustic holograms and integrate them into a multi-frequency acoustic hologram. After obtaining the transcranial multi-frequency acoustic hologram, the phase information of the multi-frequency acoustic hologram is extracted and converted into the height of each pixel of the acoustic holographic lens.

[0033] Based on the same concept, the present invention also provides an electronic device, comprising:

[0034] A memory, the memory being used to store a processing program;

[0035] A processor, wherein when executing the processing program, the processor implements any one of the above-mentioned transcranial ultrasound multi-frequency acoustic holographic lens design methods.

[0036] Based on the same concept, the present invention also provides a readable storage medium, on which a processing program is stored. When the processing program is executed by a processor, any one of the above-mentioned transcranial ultrasound multi-frequency acoustic holographic lens design methods is implemented.

[0037] Due to the adoption of the above technical solution, the present invention has the following advantages and positive effects compared with the prior art:

[0038] By extracting effective information from multiple acoustic holographic lenses with different working frequencies that focus on different positions, and integrating them into a multi-frequency acoustic holographic lens, multi-frequency transcranial focusing based on a single multi-frequency acoustic holographic lens can be achieved. The multi-frequency acoustic holographic lens designed and manufactured based on the method proposed in the present invention can reconstruct the corresponding focus on the focusing plane according to different driving frequencies, and generate different focuses with accurate positions through the skull phantom under the excitation of ultrasound of different frequencies, thereby improving the flexibility of the multi-frequency acoustic holographic lens in the application of transcranial focusing and enhancing its application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings, wherein:

[0040] Figure 1 This is a flow chart of a method for designing a transcranial ultrasound multi-frequency acoustic holographic lens according to an embodiment of the present invention;

[0041] Figure 2 This is a schematic diagram of a transcranial ultrasound multi-frequency acoustic holographic lens according to an embodiment of the present invention;

[0042] Figure 3 Comparison between the focus and target image after transcranial reconstruction at different driving frequencies through the multi-frequency acoustic holographic lens. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that the drawings are all in a very simplified form and use non-precise ratios, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0044] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0045] First embodiment

[0046] like Figure 1 As shown, the transcranial ultrasound multi-frequency acoustic holographic lens design method in this embodiment includes the following steps:

[0047] Step S1, setting two different groups of focus points, namely T1 and T2. In this embodiment, setting two different groups of focus points is taken as an example, but the concept of the present invention is applicable to setting multiple groups of different focus points.

[0048] Step S2, using the k-wave toolbox in Matlab to simulate ultrasonic propagation, using the time inversion method, setting T1 and T2 as sound sources, the emitted ultrasonic frequencies are 1 MHz and 2 MHz, respectively, and capturing the phases H1(x, y) and H2(x, y) at the holographic surface. The specific simulation settings are as follows: Figure 2 In the simulation of this embodiment, the grid pixel size is 250 um, and the Courant number (CFL number) is set to 0.2.

[0049] Step S3, extract the effective information of the two sets of acoustic holograms and integrate them into a multi-frequency acoustic hologram H(x,y). Define the following cost function:

[0050] C=E(|p f (x,y)|)-α(std(|p f (x,y)|))-βS

[0051]

[0052] Among them, E(|p f (x,y)|) is the average pressure value received on the holographic surface under a certain frequency drive, std(|p f(x,y)|) is the standard deviation of the pressure value received on the holographic surface under a certain frequency drive. S is a smoothing term obtained by the second-order accurate finite difference approximation of the Laplace operator, and α and β are weight parameters. First, initialize the multi-frequency hologram H(x,y) to 0. Start from the beginning and traverse each pixel value in turn, assigning a value from H1(x,y) and H2(x,y) to each pixel value to maximize the cost function within the pixel point, and then repeat this operation until all pixels are updated. Repeat the iteration. The iteration is terminated when the number of pixels changed compared to the previous iteration is less than 0.5% of the total pixels on the surface.

[0053] In the initial iteration, β is set to 0, and β is updated after each iteration so that E(|p n |)=-0.5βS, and the variable α is always set to 0.3. After obtaining the transcranial acoustic hologram, the following formula is used to convert the extracted phase information into the height of each pixel of the acoustic holographic lens:

[0054] h(i,j)=w(i,j).c water .c lens / 2πf.(c lens -c water )

[0055] Where w(i,j) is the phase corresponding to pixel (i,j), c water and c lens is the speed of sound in water and in the holographic lens material. f is the average of the two frequencies set. The final acoustic holographic lens is as follows: Figure 2 shown.

[0056] Step S4, in the simulation, the multi-frequency acoustic hologram obtained is used to perform a transcranial focusing simulation experiment. The simulation environment is consistent with step S1. In the simulation, the distance between the focusing plane and the plane where the ultrasonic transducer is located is 50 mm. The skull phantom is placed between the focusing plane and the ultrasonic transducer, 10 mm away from the focusing plane. The reconstructed focus is obtained on the focusing plane by exciting at different frequencies. The contrast between the reconstructed focus and the target image is as follows: Figure 3 The quality of the transcranial multi-frequency acoustic holographic lens is evaluated by comparing the PSNR (Peak signal-to-noise ratio) between the focal position and the generated focal point and T1 and T2. The PSNR calculation formula is as follows:

[0057]

[0058] Among them, MAX represents the maximum value of the image pixel, MSE represents the mean square error between the reconstructed focus and the target focus, and the higher the PSNR value, the better the image reconstruction quality.

[0059] In one embodiment, under the frequency excitation of 2 MHz, the average PSNR of the transcranial focus reconstructed by the multi-frequency acoustic holographic lens is 40.01, and under the frequency excitation of 1 MHz, the average PSNR of the transcranial focus reconstructed by the multi-frequency acoustic holographic lens is 30.78. The higher PSNR indicates that the lens can generate different high-quality focuses through the skull under the excitation of different frequencies.

[0060] By extracting effective information from multiple acoustic holographic lenses with different working frequencies that focus on different positions, and integrating it into a multi-frequency acoustic holographic lens, multi-frequency transcranial focusing based on a single multi-frequency acoustic holographic lens can be achieved. The multi-frequency acoustic holographic lens designed and manufactured based on the method proposed in the present invention can reconstruct the corresponding focus on the focusing plane according to different driving frequencies, thereby improving the flexibility of the multi-frequency acoustic holographic lens in the application of transcranial focusing and enhancing its application potential.

[0061] Second embodiment

[0062] Based on the same concept, the present invention also provides a transcranial ultrasound multi-frequency acoustic holographic lens design system, comprising:

[0063] A reading module, used for acquiring a plurality of different focus points that are set;

[0064] A phase information capture module is used to use the k-wave toolbox in Matlab, use the time inversion method to set the multiple different focal points as sound sources respectively, use multiple driving frequencies to perform simulation experiments respectively, capture the phase at the plane where the ultrasonic transducer is placed, and obtain multiple acoustic holograms;

[0065] The multi-frequency information synthesis module is used to extract effective information of multiple acoustic holograms and integrate them into a multi-frequency acoustic hologram. After obtaining the transcranial multi-frequency acoustic hologram, the phase information of the multi-frequency acoustic hologram is extracted and converted into the height of each pixel of the acoustic holographic lens.

[0066] Based on the same concept, the present invention also provides an electronic device, comprising: a memory, the memory being used to store a processing program; and a processor, the processor implementing any one of the above-mentioned transcranial ultrasound multi-frequency acoustic holographic lens design methods when executing the processing program.

[0067] Based on the same concept, the present invention also provides a readable storage medium, on which a processing program is stored. When the processing program is executed by a processor, any one of the above-mentioned transcranial ultrasound multi-frequency acoustic holographic lens design methods is implemented.

[0068] If the transcranial ultrasound multi-frequency acoustic holographic lens design method is implemented in the form of program instructions and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this embodiment is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of software. The computer software is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present disclosure. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM), random access memory (RAM), disk or optical disk, etc., and other media that can store program codes.

[0069] Those skilled in the art can clearly understand that, for the sake of convenience and brevity in description, the identification content specifically executed by the above-described system and device can refer to the corresponding process in the aforementioned method embodiment.

[0070] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they still fall within the protection scope of the present invention.

Claims

1. A transcranial ultrasound multi-frequency acoustic holographic lens design method, characterized in that: The following steps are involved: Step S1, setting a plurality of different focusing points; Step S2, using the k-wave toolbox in Matlab, using the time inversion method to set the multiple different focal points as sound sources respectively, using multiple driving frequencies to perform simulation experiments respectively, capturing the phase at the plane where the ultrasonic transducer is placed, and obtaining multiple acoustic holograms; Step S3, extracting effective information of multiple acoustic holograms, integrating them into a multi-frequency acoustic hologram, and after obtaining the transcranial multi-frequency acoustic hologram, extracting the phase information of the multi-frequency acoustic hologram and converting it into the height of each pixel of the acoustic holographic lens.

2. The transcranial ultrasound multi-frequency acoustic holographic lens design method according to claim 1, characterized in that: Step S1 further comprises: First input or select the basic parameters of the acoustic lens including the size, shape and material properties of the lens in the software, and set two different focusing points T1 and T2.

3. The transcranial ultrasound multi-frequency acoustic holographic lens design method according to claim 1, characterized in that: Step S2 further comprises: The k-wave toolbox was used in Matlab to simulate ultrasonic propagation. The time inversion method was used to set the multiple different focal points as sound sources. The emitted ultrasonic driving frequencies were 1 MHz and 2 MHz, respectively. The phases at the holographic surface were captured to obtain multiple acoustic holograms, where the grid pixel size was 250 um and the Courant number was set to 0.

2.

4. The transcranial ultrasound multi-frequency acoustic holographic lens design method according to claim 1, characterized in that: Step S3 extracts the effective information of the multiple acoustic holograms and integrates them into a multi-frequency acoustic hologram H(x,y) further comprising: Define the cost function: C=E(|p f (x,y)|)-α(std(|p f (x,y)|))-βS Among them, E(|p f (x,y)|) is the average pressure value received on the holographic surface under the preset frequency drive, std(|p f (x,y)|) is the standard deviation of the pressure value received on the holographic surface under the preset frequency drive, S is the smoothing term obtained by the second-order accurate finite difference approximation of the Laplace operator, and α and β are weight parameters; Initialize the multi-frequency acoustic hologram H(x,y) to 0, traverse each pixel value in turn from the beginning, assign a value of the corresponding pixel of the multiple acoustic holograms to each pixel value to maximize the cost function in the pixel point, and then repeat this operation until all pixels are updated; The iteration is repeated and terminated when the number of pixels changed compared to the previous iteration is less than 0.5% of the total pixels on the surface.

5. The transcranial ultrasound multi-frequency acoustic holographic lens design method according to claim 4, characterized in that: Step S3 extracts the effective information of the plurality of acoustic holograms and integrates them into a multi-frequency acoustic hologram H(x,y), further comprising: In the initial iteration, β is set to 0, and β is updated after each iteration so that E(|p n |)=-0.5βS, the variable α is always set to 0.

3. After obtaining the transcranial multi-frequency acoustic hologram, the following formula is used to convert the extracted phase information into the height of each pixel of the acoustic holographic lens: h(i,j)=w(i,j).c water .c lens / 2πf.(c lens -c water ) Where w(i,j) is the phase corresponding to pixel (i,j), c water and c l ens is the speed of sound in water and in the holographic lens material, f is the average of the two frequencies set, and the acoustic holographic lens is finally obtained.

6. The transcranial ultrasound multi-frequency acoustic holographic lens design method according to claim 1, characterized in that: The method further comprises step S4 of performing a transcranial focusing simulation experiment based on the multi-frequency acoustic hologram, and comparing the obtained focus with the multiple different focus points: In the simulation, the distance between the focusing plane and the plane where the ultrasonic transducer is located is 50 mm. The skull phantom is placed between the focusing plane and the ultrasonic transducer, 10 mm away from the focusing plane. The focus of the multi-frequency acoustic holographic lens after reconstructing is obtained on the focusing plane by exciting with different driving frequencies, and the PSNR between the focal position of the multi-frequency acoustic holographic lens and the multiple different focusing points is compared.

7. The transcranial ultrasound multi-frequency acoustic holographic lens design method according to claim 6, characterized in that: Step S4 further includes: The calculation formula for the evaluated PSNR is: Where MAX represents the maximum value of the image pixel, and MSE represents the mean square error between the reconstructed focus and the target focus.

8. A transcranial ultrasound multi-frequency acoustic holographic lens design system, characterized in that: include: A reading module, used for acquiring a plurality of different focus points that are set; A phase information capture module is used to use the k-wave toolbox in Matlab, use the time inversion method to set the multiple different focal points as sound sources respectively, use multiple driving frequencies to perform simulation experiments respectively, capture the phase at the plane where the ultrasonic transducer is placed, and obtain multiple acoustic holograms; The multi-frequency information synthesis module is used to extract effective information of multiple acoustic holograms and integrate them into a multi-frequency acoustic hologram. After obtaining the transcranial multi-frequency acoustic hologram, the phase information of the multi-frequency acoustic hologram is extracted and converted into the height of each pixel of the acoustic holographic lens.

9. An electronic device, characterized in that: include: A memory, the memory being used to store a processing program; A processor, wherein when executing the processing program, the processor implements the transcranial ultrasound multi-frequency acoustic holographic lens design method as described in any one of claims 1 to 7.

10. A readable storage medium, characterized in that: The readable storage medium stores a processing program, and when the processing program is executed by the processor, the transcranial ultrasound multi-frequency acoustic holographic lens design method according to any one of claims 1 to 7 is implemented.

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