Epilepsy child brain oxygen monitoring method based on near-infrared gating ICCD imaging technology

Abstract

The invention discloses an epilepsy child brain oxygen monitoring method based on a near-infrared gating ICCD imaging technology, and belongs to the technical field of medical monitoring and brain function imaging. Pulse is transmitted to the head of an epilepsy child through a laser, and photons return again after reaching brain tissue; setting an acquisition interval of the near-infrared gating ICCD detector to acquire a plurality of brain frame images; acquiring the light intensity of each pixel point in the plurality of brain frame images, and establishing a light intensity response curve; photon flight parameters are extracted to invert an absorption coefficient and a scattering coefficient corresponding to each pixel point; fitting oxyhemoglobin concentration and reduced hemoglobin concentration corresponding to each pixel point, and calculating oxygen saturation; and generating a brain oxygen saturation image for brain oxygen monitoring. The space coverage range, the imaging efficiency and the quantitative accuracy of brain oxygen monitoring are remarkably improved, and a powerful visual tool is provided for epilepsy focus positioning and preoperative brain function evaluation of child epilepsy.

Description

Technical Field

[0001] This invention relates to the field of medical monitoring technology, specifically to a method for monitoring brain oxygenation in children with epilepsy based on near-infrared gated ICCD imaging technology. Background Technology

[0002] Epilepsy is one of the most common chronic neurological disorders in childhood. For children with drug-resistant epilepsy, surgical resection of the epileptogenic focus is an important treatment. The key to its success lies in the precise preoperative localization of the epileptogenic focus and the clear delineation of important brain functional areas. Functional near-infrared spectroscopy (fNIRS), as a non-invasive, safe, and relatively insensitive optical brain imaging technique to head movements, has unique advantages in the preoperative evaluation of children with epilepsy, especially suitable for infants and children with low cooperation levels. By monitoring changes in hemoglobin concentration in the cerebral cortex, fNIRS can effectively monitor the cortical hemodynamic response triggered by epileptic seizures and interictal epileptiform discharges, providing hemodynamic information different from electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) for epileptogenic focus localization and brain functional area mapping.

[0003] However, applying existing fNIRS technology to precise brain oxygenation monitoring and imaging in children with epilepsy still faces a series of inherent and interconnected technical bottlenecks. First, regarding spatial resolution and sampling density, the mainstream clinical continuous wave (CW-fNIRS) system essentially relies on sparsely arranged discrete fiber optic probes for measurement, making it difficult to achieve high-density, full-coverage continuous two-dimensional cortical imaging. This may lead to the omission of subtle local blood oxygenation abnormalities related to the epileptogenic focus. Second, regarding signal quality and quantitative accuracy, CW-fNIRS technology only measures light intensity attenuation and cannot effectively separate tissue absorption and scattering effects. Its measurement results are easily interfered with by superficial physiological noise such as scalp blood flow, affecting the extraction of epilepsy-specific blood oxygenation signals. Although time-domain fNIRS (TD-fNIRS) systems based on time-correlated single-photon counting technology can improve quantitative and depth discrimination capabilities through photon time-of-flight distribution, traditional TD systems are limited by single-point or low-channel scanning modes, generally suffering from low sampling rates, complex and bulky systems, and sparse head coverage, making it difficult to meet the clinical needs for rapid, large-area bedside imaging. Finally, in terms of technology development and system integration, the single-photon avalanche diode (SPAD) array technology, which aims to increase the number of channels, faces challenges in practical applications such as the surge in data volume brought about by the single-photon counting mode, high real-time processing complexity, and great difficulty in system integration.

[0004] In summary, there is an urgent need in the field of brain oxygenation monitoring for children with epilepsy to develop an fNIRS system that possesses high photon arrival time resolution, can express time response in two-dimensional image form, and also has high spatial resolution, non-contact measurement, and real-time imaging characteristics, in order to achieve rapid, accurate, and visualized assessment of whole-brain blood oxygenation dynamics in children with epilepsy. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for monitoring brain oxygenation in children with epilepsy based on near-infrared gated ICCD imaging technology. This method utilizes a near-infrared gated ICCD detector and a laser. The laser emits pulses towards the head of the child with epilepsy; photons reach the brain tissue and then return. Multiple brain frame images are acquired at a set acquisition interval using the near-infrared gated ICCD detector. The light intensity of each pixel in the multiple brain frame images is obtained to establish a light intensity response curve. Photon flight parameters are extracted to invert the absorption and scattering coefficients corresponding to each pixel. The oxyhemoglobin and deoxyhemoglobin concentrations corresponding to each pixel are fitted, and oxygen saturation is calculated. A brain oxygen saturation image is generated for brain oxygen monitoring. This invention significantly improves the spatial coverage, imaging efficiency, and quantitative accuracy of brain oxygen monitoring, providing a powerful visualization tool for locating epileptogenic foci and preoperative brain function assessment in children with epilepsy.

[0006] The present invention adopts the following technical solution: a method for monitoring brain oxygenation in children with epilepsy based on near-infrared gated ICCD imaging technology, wherein the brain oxygenation monitoring method is based on a near-infrared gated ICCD detector and a laser; The brain oxygen monitoring method includes: By setting the acquisition interval of the near-infrared gated ICCD detector, multiple brain frame images of the child with epilepsy are obtained by acquiring photons that return after the laser emits a pulse to the head of the child with epilepsy. The light intensity of each pixel in multiple brain frame images is obtained, and the light intensity response curve of each pixel is established. Gaussian fitting is performed on the light intensity response curve of each pixel to extract the photon flight parameters corresponding to each pixel. Based on the photon flight parameters, the absorption coefficient and scattering coefficient corresponding to each pixel are inverted using a time distribution model combined with diffusion approximation theory. The oxygenated hemoglobin concentration and deoxyhemoglobin concentration corresponding to each pixel are fitted based on the absorption coefficient and scattering coefficient; The oxygen saturation of each pixel is calculated based on the oxygenated hemoglobin concentration and the deoxyhemoglobin concentration. An oxygen saturation image of the brain of a child with epilepsy is generated based on the oxygen saturation corresponding to each pixel; brain oxygenation is monitored based on the oxygen saturation image.

[0007] Furthermore, the photon flight parameters include: The average arrival time of photons, the half-width at half-maximum (FWHM) of the intensity response curve, and the area enclosed by the intensity response curve and the coordinate axes.

[0008] Furthermore, based on the aforementioned photon flight parameters, the absorption coefficient and scattering coefficient corresponding to each pixel are inverted using a time distribution model combined with the diffusion approximation theory, specifically as follows: A diffusion equation for photon propagation is established based on the diffusion approximation theory; The simulated absorption coefficient and simulated scattering coefficient are set, and the diffusion equation is solved by forward simulation using a time distribution model to obtain the simulated parameters of photon flight. An objective function is constructed based on photon flight parameters and photon flight simulation parameters; An optimization algorithm is used to iteratively update the simulated absorption coefficient and simulated scattering coefficient; Calculate the objective function value after each iteration until the objective function converges, and obtain the absorption coefficient and scattering coefficient corresponding to each pixel.

[0009] Furthermore, the oxyhemoglobin concentration and deoxyhemoglobin concentration corresponding to each pixel are fitted based on the absorption coefficient and scattering coefficient, specifically as follows: The absorption coefficient and scattering coefficient corresponding to each pixel were fitted using a dual-wavelength method. The optical path of each pixel is corrected based on the scattering coefficient. Based on the corrected optical path length and the absorption coefficient, a dual-wavelength absorption equation is established based on the Beer-Lambert law. The dual-wavelength absorption equation is solved to obtain the oxyhemoglobin concentration and deoxyhemoglobin concentration corresponding to each pixel.

[0010] Furthermore, the method for calculating the oxygen saturation of each pixel based on the oxyhemoglobin concentration and the deoxyhemoglobin concentration is as follows: The total hemoglobin concentration for each pixel is obtained by summing the oxyhemoglobin concentration and the deoxyhemoglobin concentration for each pixel. The oxygen saturation of each pixel is obtained by calculating the ratio of oxyhemoglobin concentration to total hemoglobin concentration.

[0011] Furthermore, after generating an oxygen saturation image of the brain of a child with epilepsy based on the oxygen saturation corresponding to each pixel, the process also includes: Regions of interest were defined in brain oxygen saturation images of children with epilepsy. Spatial registration of brain oxygen saturation images of children with epilepsy is performed based on the set region of interest to generate brain region oxygen saturation mapping images of children with epilepsy.

[0012] The beneficial effects of this invention are as follows: This invention achieves multi-channel parallel acquisition and generates whole-brain frame images through a near-infrared gated ICCD detector, thereby replacing the traditional single-point detector and significantly improving the spatial coverage and imaging efficiency of brain image acquisition; This invention extracts high-precision photon flight parameters based on Gaussian fitting, and combines the absorption coefficient and scattering coefficient with the time distribution model and diffusion equation to improve the temporal resolution to the picosecond level, enhancing the accuracy of brain tissue parameter calculation; The invention establishes a corrected optical path dual-wavelength absorption equation using the dual-wavelength method, which can accurately separate the concentrations of oxyhemoglobin and deoxyhemoglobin, and calculate oxygen saturation through the ratio method, effectively eliminating measurement errors caused by scattering interference; When generating brain oxygen saturation images, it can also support spatial registration of regions of interest, thereby outputting brain region oxygen saturation mapping maps, intuitively locating blood oxygen abnormalities related to epileptic activity, and providing important functional imaging evidence for preoperative localization and surgical planning of epileptogenic foci; In summary, this invention uses a software and hardware co-optimization method to achieve non-contact, high frame rate acquisition, which is suitable for head movement scenarios that may occur in children with epilepsy, improving its practicality for use in neurophysiological monitoring rooms or bedside applications. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of a method for monitoring brain oxygenation in children with epilepsy based on near-infrared gated ICCD imaging technology, according to an embodiment of the present invention. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] The brain oxygen monitoring method for children with epilepsy provided in this embodiment of the invention is based on the cooperation of an imaging probe composed of a near-infrared gated ICCD detector, an optical collection system, and a laser. The laser sends picosecond-level near-infrared pulse laser light to the scalp surface of the child with epilepsy. The photons enter the scalp tissue and cortex and undergo scattering and absorption. Some of the scattered photons return to the scalp surface after passing through the tissue and are collected by the optical collection system. The collected photons are converted into multiple frames of images through a time-delay acquisition method, and then the multiple frames of images are analyzed and processed to realize brain oxygen monitoring for children with epilepsy.

[0017] Specifically, a flowchart illustrating a method for monitoring brain oxygenation in children with epilepsy based on near-infrared gated ICCD imaging technology according to an embodiment of the present invention is shown below. Figure 1 As shown, it includes: By setting the acquisition interval of the near-infrared gated ICCD detector, multiple brain frame images of the child with epilepsy are obtained by acquiring photons that return after the laser emits a pulse to the head of the child with epilepsy. The near-infrared gated ICCD detector used in this embodiment of the invention is a picosecond-gated ICCD detector that combines ultra-high-speed time resolution with high-sensitivity photon detection. It controls the "on-off" time window (gated width) of the image intensifier via electrical signals, achieving picosecond-level precision. This is equivalent to precisely filtering photons arriving at specific times in the time dimension. In this embodiment, the acquisition interval is set to 100 picoseconds. After the pulsed laser emitted by the laser enters the brain, the photons undergo elastic scattering and absorption with the brain tissue. The returning photons typically fall into two categories: ballistic photons, which undergo little or no scattering and return along an approximately straight line, generally carrying structural information from the superficial layers of brain tissue; and diffuse photons, which are returned after multiple scatterings and generally carry functional information from the deeper layers of brain tissue. By setting a picosecond-gated acquisition interval, this embodiment of the invention continuously acquires returning photons and selectively acquires different types of returning photons, thereby reconstructing brain images. Through continuous acquisition, multiple brain frames of children with epilepsy can be obtained.

[0018] The light intensity of each pixel in multiple brain frame images is obtained, and the light intensity response curve of each pixel is established. In this embodiment of the invention, by extracting the light intensity of the same pixel in multiple brain frame images, a light intensity response curve of each pixel changing over time can be established. For specific extraction methods, any one of the methods disclosed in the prior art can be referred to.

[0019] Gaussian fitting is performed on the light intensity response curve of each pixel to extract the photon flight parameters corresponding to each pixel. In this embodiment of the invention, Gaussian fitting is used to extract photon flight parameters from the light intensity response curve. The extracted photon flight parameters include: average photon arrival time, half width at half maximum (FWHM) of the light intensity response curve, and the area enclosed by the light intensity response curve and the coordinate axes.

[0020] Specifically, this embodiment of the invention first performs preprocessing on the light intensity response curve of each pixel to suppress noise data in the light intensity response curve. Then, it aligns the data in the light intensity response curve, that is, aligns the time axis with the light intensity value to avoid fitting errors caused by time offset. Since the light intensity response curve usually conforms to a single-peak or multi-peak Gaussian distribution, a Gaussian function can be used to fit the light intensity response curve. After fitting, the photon flight parameters can be directly calculated from the parameters of the Gaussian function. For example, the average time from photon emission to reception can be directly represented by the Gaussian mean, that is, the average arrival time of photons in the photon flight parameters. The half-width and height parameters of the light intensity response curve can be obtained by reading the peak value of the curve and calculating the width corresponding to the peak value and half of the peak value. The area enclosed by the light intensity response curve and the coordinate axis can be calculated by calculus. By using the Gaussian fitting method for mathematical modeling, the complex light intensity response curve is simplified into an analytical parameter.

[0021] In another embodiment of the present invention, the photon flight parameters corresponding to each pixel can also be extracted by polynomial fitting.

[0022] Based on the photon flight parameters, the absorption coefficient and scattering coefficient corresponding to each pixel are inverted using a time distribution model combined with the diffusion approximation theory. In this embodiment of the invention, a diffusion equation for photon propagation is established based on the diffusion approximation theory; a simulated absorption coefficient and a simulated scattering coefficient are set, and a time distribution model is used to perform a forward simulation solution of the diffusion equation to obtain photon flight simulation parameters; an objective function is constructed based on the photon flight parameters and the photon flight simulation parameters; an optimization algorithm is used to iteratively update the simulated absorption coefficient and the simulated scattering coefficient; the objective function value after each iteration is calculated until the objective function converges, and the absorption coefficient and scattering coefficient corresponding to each pixel are obtained.

[0023] Specifically, the diffusion approximation theory refers to the approximation of photon propagation in a medium as a diffusion process under certain conditions. The diffusion equation established by this is a mathematical equation used to describe the diffusion and propagation of photons in a medium. It uses the absorption coefficient and scattering coefficient as parameters and can describe the spatial and temporal distribution of photons in the medium. The temporal distribution model is the analytical solution of the diffusion equation. In this embodiment of the invention, simulated absorption coefficient and simulated scattering coefficient are further set, and the diffusion equation is solved by forward simulation through the temporal distribution model, i.e., forward modeling, to obtain the photon flight simulation parameters. Then, an objective function is constructed based on the difference between the photon flight parameters and the photon flight simulation parameters. In this embodiment, the objective function can be constructed in the form of mean square error or absolute error. The smaller the value of the objective function, the closer the value of the photon flight simulation parameters is to the true value. The objective function is optimized by iteratively updating the values ​​of the simulated absorption coefficient and simulated scattering coefficient. When the objective function converges, the simulated absorption coefficient and simulated scattering coefficient at this time are the absorption coefficient and scattering coefficient required in this embodiment of the invention.

[0024] The concentrations of oxyhemoglobin and deoxyhemoglobin corresponding to each pixel are fitted based on the absorption coefficient and scattering coefficient. In this embodiment of the invention, the absorption coefficient and scattering coefficient corresponding to each pixel are fitted using a dual-wavelength method; the optical path length corresponding to each pixel is corrected based on the scattering coefficient; a dual-wavelength absorption equation is established based on the Beer-Lambert law according to the corrected optical path length and absorption coefficient; the dual-wavelength absorption equation is solved to obtain the oxyhemoglobin concentration and deoxyhemoglobin concentration corresponding to each pixel.

[0025] Specifically, in this embodiment of the invention, two light sources of specific wavelengths are selected, for example... and The wavelengths are 660nm and 805nm, respectively, corresponding to the characteristic absorption peaks of oxyhemoglobin and deoxyhemoglobin. The light intensity data of each pixel at the two wavelengths is obtained, and then the absorption coefficient and scattering coefficient corresponding to each pixel are obtained based on the dual-wavelength light intensity data. When the laser is emitted towards brain tissue, the light deviates from straight-line propagation due to scattering. At this time, the optical path of the pixel is usually greater than the thickness of the brain tissue. Therefore, this embodiment of the invention uses the scattering coefficient to correct the optical path of each pixel, thereby obtaining a more accurate optical path. Then, based on the corrected optical path and absorption coefficient, a dual-wavelength absorption equation is established based on the Beer-Lambert law. The specific establishment method can refer to existing research on the Beer-Lambert law, which is existing technology. By simultaneously solving the dual-wavelength equations, the concentrations of oxyhemoglobin and deoxyhemoglobin corresponding to each pixel can be obtained.

[0026] The oxygen saturation of each pixel is calculated based on the concentrations of oxyhemoglobin and deoxyhemoglobin. In this embodiment of the invention, after obtaining the oxyhemoglobin concentration and the deoxyhemoglobin concentration, the total hemoglobin concentration corresponding to each pixel is first calculated by summing the oxyhemoglobin concentration and the deoxyhemoglobin concentration. Then, the oxygen saturation corresponding to each pixel can be obtained by the ratio of the oxyhemoglobin concentration to the total hemoglobin concentration. By calculating the oxygen saturation corresponding to all pixels, an oxygen saturation image of the brain of a child with epilepsy is generated.

[0027] An oxygen saturation image of the brain of a child with epilepsy is generated based on the oxygen saturation corresponding to each pixel; brain oxygenation is monitored based on the oxygen saturation image.

[0028] In this embodiment of the invention, after acquiring the oxygen saturation data corresponding to each pixel, these data are presented in the form of an image, which is the oxygen saturation image of the brain of a child with epilepsy. The generated oxygen saturation image is used to monitor the oxygen supply to the brain of a child with epilepsy, thereby assisting doctors in locating abnormal blood oxygenation areas related to epileptic seizures or interictal discharges by observing the image, assessing the blood flow and metabolic status of the epileptogenic focus, and providing a basis for preoperative assessment.

[0029] In this embodiment of the invention, after generating an oxygen saturation image of the brain of a child with epilepsy based on the oxygen saturation corresponding to each pixel, a region of interest (ROI) is further set in the oxygen saturation image of the child's brain. The ROI can be a region of epileptogenic focus initially suspected based on electrophysiological or imaging examinations, or a key brain function area such as language or motor function to be evaluated. The oxygen saturation image of the child's brain is spatially registered according to the set ROI, and the image is adjusted and matched so that the various parts in the image can accurately correspond in space, generating a brain region oxygen saturation mapping image of the child's brain. This more intuitively reflects the differences in oxygen saturation in the target brain region, helping doctors to more accurately locate the epileptogenic focus and plan surgery.

[0030] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for monitoring brain oxygenation in children with epilepsy based on near-infrared gated ICCD imaging technology, characterized in that, The brain oxygen monitoring method is based on a near-infrared gated ICCD detector and a laser; The brain oxygen monitoring method includes: By setting the acquisition interval of the near-infrared gated ICCD detector, multiple brain frame images of the child with epilepsy are obtained by acquiring photons that return after the laser emits a pulse to the head of the child with epilepsy. The light intensity of each pixel in multiple brain frame images is obtained, and the light intensity response curve of each pixel is established. Gaussian fitting is performed on the light intensity response curve of each pixel to extract the photon flight parameters corresponding to each pixel. Based on the photon flight parameters, the absorption coefficient and scattering coefficient corresponding to each pixel are inverted using a time distribution model combined with diffusion approximation theory. The oxygenated hemoglobin concentration and deoxyhemoglobin concentration corresponding to each pixel are fitted based on the absorption coefficient and scattering coefficient; The oxygen saturation of each pixel is calculated based on the oxygenated hemoglobin concentration and the deoxyhemoglobin concentration. An oxygen saturation image of the brain of a child with epilepsy is generated based on the oxygen saturation corresponding to each pixel; brain oxygenation is monitored based on the oxygen saturation image.

2. The method for monitoring brain oxygenation in children with epilepsy based on near-infrared gated ICCD imaging technology according to claim 1, characterized in that: The photon flight parameters include: The average arrival time of photons, the half-width at half-maximum (FWHM) of the intensity response curve, and the area enclosed by the intensity response curve and the coordinate axes.

3. The method for monitoring brain oxygenation in children with epilepsy based on near-infrared gated ICCD imaging technology according to claim 1, characterized in that: Based on the aforementioned photon flight parameters, the absorption and scattering coefficients corresponding to each pixel are retrieved using a time distribution model combined with the diffusion approximation theory, specifically as follows: A diffusion equation for photon propagation is established based on the diffusion approximation theory; The simulated absorption coefficient and simulated scattering coefficient are set, and the diffusion equation is solved by forward simulation using a time distribution model to obtain the simulated parameters of photon flight. An objective function is constructed based on photon flight parameters and photon flight simulation parameters; An optimization algorithm is used to iteratively update the simulated absorption coefficient and simulated scattering coefficient; Calculate the objective function value after each iteration until the objective function converges, and obtain the absorption coefficient and scattering coefficient corresponding to each pixel.

4. The method for monitoring brain oxygenation in children with epilepsy based on near-infrared gated ICCD imaging technology according to claim 1, characterized in that: The oxygenated hemoglobin concentration and deoxyhemoglobin concentration corresponding to each pixel are fitted based on the absorption coefficient and scattering coefficient, specifically as follows: The absorption coefficient and scattering coefficient corresponding to each pixel were fitted using a dual-wavelength method. The optical path of each pixel is corrected based on the scattering coefficient. Based on the corrected optical path length and the absorption coefficient, a dual-wavelength absorption equation is established based on the Beer-Lambert law. The dual-wavelength absorption equation is solved to obtain the oxyhemoglobin concentration and deoxyhemoglobin concentration corresponding to each pixel.

5. A method for monitoring brain oxygenation in children with epilepsy based on near-infrared gated ICCD imaging technology according to claim 1, characterized in that: The method for calculating the oxygen saturation of each pixel based on the oxyhemoglobin concentration and the deoxyhemoglobin concentration is as follows: The total hemoglobin concentration for each pixel is obtained by summing the oxyhemoglobin concentration and the deoxyhemoglobin concentration for each pixel. The oxygen saturation of each pixel is obtained by calculating the ratio of oxyhemoglobin concentration to total hemoglobin concentration.

6. The method for monitoring brain oxygenation in children with epilepsy based on near-infrared gated ICCD imaging technology according to claim 1, characterized in that: After generating an oxygen saturation image of the brain of a child with epilepsy based on the oxygen saturation corresponding to each pixel, the process also includes: Regions of interest were defined in brain oxygen saturation images of children with epilepsy. Spatial registration of brain oxygen saturation images of children with epilepsy is performed based on the set region of interest to generate brain region oxygen saturation mapping images of children with epilepsy.

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