Patent Publication Number: US-11042983-B1

Title: Automatic brain infarction detection system on magnetic resonance imaging and operation method thereof

Description:
RELATED APPLICATIONS 
     This application claims priority to Taiwan Patent Application No. 109112042, filed Apr. 9, 2020, the entirety of which is herein incorporated by reference. 
     BACKGROUND 
     Field of Invention 
     The present invention relates to systems and methods, and more particularly, automatic brain infarction detection systems on magnetic resonance imaging (MRI) and operating methods thereof. 
     Description of Related Art 
     After cerebral infarction, the energy metabolism of brain tissue is destroyed, and a large amount of extracellular water enters the cell. Thus, intracellular water molecules are increased, and extracellular water molecules are decreased, thereby resulting in limited diffusion. However, the amount of water in the ischemic area does not change, and only the water content inside and outside the cell changes, which limits the diffusion. Therefore, conventional MRI examinations, such as T1, T2, FLAIR, and so on, often fail to detection. 
     In view of above, there is an urgent need in the related field to provide an automatic brain infarction detection system and an operating method thereof. 
     SUMMARY 
     In one or more various aspects, the present disclosure is directed to automatic brain infarction detection systems on magnetic resonance imaging (MRI) and operating methods thereof. 
     An embodiment of the present disclosure is related to an automatic brain infarction detection system on magnetic resonance imaging (MRI). The automatic brain infarction detection system includes a memory circuit and a processor. The memory circuit is configured to store at least one instruction. The processor is coupled to the memory circuit, and the processor configured to access and execute the at least one instruction for: receiving a plurality of images corresponding to different slices of a brain of a subject from a MRI machine; performing an image mask process on a first image and a second image of the plurality of images; determining whether a cerebellum image intensity and a brain image intensity in the first image are matched; adjusting the cerebellum image intensity in the first image when the cerebellum image intensity and the brain image intensity are not matched; processing the first image through a nonlinear regression to obtain a third image; and utilizing a neural network to identify an infarct region by using the first, second and third images that are cut. 
     In one embodiment of the present disclosure, the first image is a diffusion-weighted image (DWI), and the second image is an apparent diffusion coefficient (ADC) map. 
     In one embodiment of the present disclosure, the plurality of images further includes a T1-weighted (T1w) image, the processor moves a position of the brain in the T1-weighted image to a center of the T1-weighted image based on an outline of the brain in the T1-weighted image, and then binarizes the T1-weighted image to find a most symmetrical rotation angle of the position of the brain in the T1-weighted image, so as to orientate the T1-weighted image, so that the T1-weighted image is positioned. 
     In one embodiment of the present disclosure, the processor uses the T1-weighted image that has been positioned as a basis of image registration for moving and orientating the DWI and the ADC map that have been binarized. 
     In one embodiment of the present disclosure, the image mask process filters out non-brain tissue from the DWI and the ADC map after the image registration. 
     Another embodiment of the present disclosure is related to an operation method of an automatic brain infarction detection system on MRI. The operation method includes steps of: receiving a plurality of images corresponding to different slices of a brain of a subject from a MRI machine; performing an image mask process on a first image and a second image of the plurality of images; determining whether a cerebellum image intensity and a brain image intensity in the first image are matched; adjusting the cerebellum image intensity in the first image when the cerebellum image intensity and the brain image intensity are not matched; processing the first image through a nonlinear regression to obtain a third image; and utilizing a neural network to identify an infarct region by using the first, second and third images that are cut. 
     In one embodiment of the present disclosure, the first image is a DWI, and the second image is an ADC map. 
     In one embodiment of the present disclosure, the plurality of images further comprises a T1-weighted image, and the operating method further includes: moving a position of the brain in the T1-weighted image to a center of the T1-weighted image based on an outline of the brain in the T1-weighted image, and then binarizing the T1-weighted image to find a most symmetrical rotation angle of the position of the brain in the T1-weighted image, so as to orientate the T1-weighted image, so that the T1-weighted image is positioned. 
     In one embodiment of the present disclosure, the operating method further includes: using the T1-weighted image that has been positioned as a basis of image registration for moving and orientating the DWI and the ADC map that have been binarized. 
     In one embodiment of the present disclosure, the image mask process filters out non-brain tissue from the DWI and the ADC map after the image registration. 
     Technical advantages are generally achieved, by embodiments of the present disclosure. With the technical solution of the present disclosure, the location of the lesion on the MRI can be accurately detected, so that clinicians can efficiently quantify the diagnosis of the MRI in the clinic. 
     Many of the attendant features will be more readily appreciated, as the same becomes better understood by reference to the following detailed description considered in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows: 
         FIG. 1  is a block diagram of an automatic brain infarction detection system on MRI according to one embodiment of the present disclosure; and 
         FIG. 2  is a flow chart of an operation method of the automatic brain infarction detection system according to one embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
     As used in the description herein and throughout the claims that follow, the meaning of “a”, “an”, and “the” includes reference to the plural unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the terms “comprise or comprising”, “include or including”, “have or having”, “contain or containing” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. As used in the description herein and throughout the claims that follow, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise. 
     It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
       FIG. 1  is a block diagram of an automatic brain infarction detection system  100  on MRI according to one embodiment of the present disclosure. As shown in  FIG. 1 , the automatic brain infarction detection system  100  includes a memory circuit  110 , a processor  120  and a display device  130 . For example, the memory circuit  110  can be a hard drive, a flash memory or another storage device, the processor  120  can be a central processing unit, and a display device  130  can be a built-in the display screen or an external screen. 
     In structure, the automatic brain infarction detection system  100  is coupled to a MRI machine  190 , and the processor  120  is coupled to the memory circuit  110  and the display device  130 . 
     In use, the memory circuit  110  store at least one instruction, the processor  120  is coupled to the memory circuit  110 , and the processor  120  accesses and executes the at least one instruction for: receiving a plurality of images corresponding to different slices of a brain of a subject from the MRI machine  190 ; performing an image mask process on a first image and a second image of the plurality of images; determining whether a cerebellum image intensity (e.g., the average intensity of a cerebellar image) and a brain image intensity (e.g., the average intensity of a brain image) in the first image are matched; when the cerebellum image intensity and the brain image intensity are not matched, adjusting the cerebellum image intensity in the first image; processing the first image through a nonlinear regression to obtain a third image; and utilizing a neural network to identify an infarct region by using the first, second and third images that are cut. 
     In one embodiment of the present disclosure, the first image is a diffusion-weighted image (DWI), and the second image is an apparent diffusion coefficient (ADC) map. It should be noted that after cerebral infarction, the energy metabolism of brain tissue is destroyed, and a large amount of extracellular water enters the cell. Thus, intracellular water molecules are increased, and extracellular water molecules are decreased, thereby resulting in limited diffusion. However, the amount of water in the ischemic area does not change, and only the water content inside and outside the cell changes, which limits the diffusion. Therefore, conventional MRI examinations, such as T1, T2, FLAIR, and so on, often fail to detection. Accordingly, the automatic brain infarction detection system  100  on MRI uses the DWI and ADC map with the most obvious infarction. 
     In one embodiment of the present disclosure, the plurality of images further comprises a T1-weighted image. The present disclosure uses T1-weighted image because the outline of the brain is clear, and the clear outline of the brain can be used for positioning, and thus the brain is placed in a fixed position in the image. In practice, the artifacts and infarction mainly on the image histogram have a large overlap, In addition, the image intensity of each patient does not have a fixed value, and the shape cannot be clearly distinguished. Therefore, the conventional method cannot directly separate the infarction and artifacts, and thus it is difficult for identification. Accordingly, the present disclosure is based on the position in the image to improve the judgment basis of the neural network. 
     Specifically, the processor  120  moves a position of the brain in the T1-weighted image to a center of the T1-weighted image based on an outline of the brain in the T1-weighted image, and then binarizes the T1-weighted image to find a most symmetrical rotation angle of the position of the brain in the T1-weighted image, so as to orientate the T1-weighted image, so that the T1-weighted image is positioned. 
     For example, the processor  120  is based on 50% of the histogram of T1-weighted image as a binarized threshold value. If the value is greater than this threshold value, it serves as 1. If the value is less than this threshold value, it serves as 0. In practice, the middle of a group of T1-weighted image can be selected as the basis of position. In the selected T1-weighted image, the cavity in the brain is filled by morphology dilation operation, and the size and contour of the brain are restored by morphology erosion operation. For example, the size of 5×5 is used as the size of dilation; the size of 5×5 is used as the size of erosion. 
     Since the human brain is symmetrical, it is necessary to find the symmetrical midline, which is the optimal rotation. The processor  120  rotates the T1-weighted image from −45 degrees to 45 degrees and shifts the 45 voxel points along each of X and Y axes. In each of above rotations or shifts, the image is divided into two halves, and the two halves are multiplied together, so as to find the maximum value of multiplication that corresponds to the optimal rotation. After the optimal rotation, the entire brain is positioned in the center of the image. 
     Then, the processor  120  uses the T1-weighted image that has been positioned as a basis of image registration for moving and orientating the DWI and the ADC map that have been binarized. 
     For example, the processor  120  is based on 60% of the histogram of DWI as a binarized threshold value. If the value is greater than this threshold value, it serves as 1. If the value is less than this threshold value, it serves as 0. In practice, the middle of a group of DWIs can be selected as the basis of position. In the selected DWI, the cavity in the brain is filled by morphology dilation operation, and the size and contour of the brain are restored by morphology erosion operation. For example, the size of 11×11 is used as the size of dilation; the size of 11×11 is used as the size of erosion. 
     The processor  120  takes the T1-weighted image as the target, rotates the DWI from −45 degrees to 45 degrees, and shifts the 45 voxel points along each of X and Y axes. In each of above rotations or shifts, the DWI is multiplied by the T1-weighted image, so as to find the maximum value of multiplication, so that the image registration of the DWI can be finished. 
     Since the ADC map is the post-production of the DWI, so that the processor  120  is based on the rotation angle and the shift of the DWI to rotate and shift the ADC map correspondingly. 
     In one embodiment of the present disclosure, the image mask process filters out non-brain tissue (e.g., noise, bones, etc.) from the DWI and the ADC map after the image registration. 
     As to determine the cerebellum image intensity and the brain image intensity, in one embodiment of the present disclosure, the processor  120  determines the average image intensities of the cerebellum (e.g., the slices before the ninth slice) and the brain (e.g., the slices after the ninth slice). If the average image intensity the cerebellum is too high, the processor  120  will reduce the average image intensity of the cerebellum to be similar to the average image intensity of the brain. For example, the average image intensity of the brain tissue is about 1000, the image intensity of the infarction is about 1500-2000, and the average image intensity of the cerebellum tissue is about 1800; the processor  120  reduces the average image intensity of the cerebellum to be 1000. 
     As to the nonlinear regression, in one embodiment of the present disclosure, the processor  120  uses the average image intensity of the brain and the average image intensity of each slice to find the nonlinear equation with the optimal threshold, and avoids the problem that the neural network recognizes the higher average image intensity as infarction. The nonlinear regression processes the DWI to generate the third image (i.e., a nonlinear regression image) to filter out normal brain tissue and noise. 
     As to image cutting, the inputted first, second and third images can be the DWI, the ADC map and the nonlinear regression image through the image mask process. The processor  120  takes a picture every time by moving 8 voxel points, where the size of the picture is 16×16 for example. The processor  120  cuts above three kinds of images at the same position and size, and superimposes the cut images. The position of the current patch, the average intensity of a whole brain image of the DWI, the average intensity of the single slice image of the DWI, and the number of slices are added at the top of the image matrix. 
     As to the number of samples of the neural network, for example, the number of patients is about 33, and the infarct size of each slice is different, so the number of sheets that can be cut is also different. Because the processor  120  cut each image into small pictures, after the cutting is completed, there are about 1300 infarct images and about 1000 artifact images; except for the infarction and artifacts, the rest parts are non-infarct and can be cut, so that the pictures that can be cut out can even reach tens of thousands. However, when difference of the amounts of respective data of the neural network is too large, the classification of the neural network may be biased to labels of too much data. The non-infarct pictures are more variable than the infarction and artifacts, so that the information required for can be much more than the infarction and artifacts, in which about 8000 non-infarct pictures are needed. The processor  120  select one-tenth of each of infarction, artifact and non-infarction images to be serve as test data and randomly shuffle the order of the test data; the processor  120  uses the rest images as training data and randomly shuffle the order of the training data. 
     As to the architecture of the neural network, for example, although Max pooling can greatly reduce the calculation speed, it loses tiny features. Because the additional information is added as above when cutting, this embodiment does not use Max pooling so as to improve the precision of the result. 
     For example, the neural network can have a total of 15 layers, where the second layer is a convolution layer, which uses 4×4 convolution kernels and has 16 random weighted convolution kernels, in which each convolution kernel convolves the original picture to get and gradually normalize 16 feature maps, in which ReLU is used to remove the lower values. The fifth layer is the convolution layer, which uses a 4×4 convolution kernel and has 32 convolution kernels, in which the convolution kernels convolve the results obtained by the previous layer to get 32 feature maps. The eighth layer is the convolution layer, which uses a 4×4 convolution kernel and has 64 convolutions kernels, in which the convolution kernels convolve the results obtained by the previous layer to get 64 feature maps. The eleventh layer can obtain 64 deeper feature maps as above manner, and use the softmax function to find out the possibility of each label, thereby finding the recognition result with the highest probability. 
     For a more complete understanding of an operating method of the automatic brain infarction detection system  100  on MRI, referring  FIGS. 1-2 ,  FIG. 2  is a flow chart of the operation method  200  of the automatic brain infarction detection system  100  according to one embodiment of the present disclosure. As shown in  FIG. 2 , the operation method  200  includes operations S 201 -S 211 . However, as could be appreciated by persons having ordinary skill in the art, for the steps described in the present embodiment, the sequence in which these steps is performed, unless explicitly stated otherwise, can be altered depending on actual needs; in certain cases, all or some of these steps can be performed concurrently. 
     The operation method  200  of the automatic brain infarction detection system  100  includes steps of: receiving a plurality of images corresponding to different slices of a brain of a subject from a MRI machine (operations S 201 -S 205 ); performing an image mask process on a first image and a second image of the plurality of images (operation S 206 ); determining whether a cerebellum image intensity and a brain image intensity in the first image are matched (operation S 207 ); when the cerebellum image intensity and the brain image intensity are not matched, adjusting the cerebellum image intensity in the first image (operation S 208 ); processing the first image through a nonlinear regression to obtain a third image (operation S 209 ); utilizing a neural network to identify an infarct region by using the first, second and third images that are cut (operations S 210 -S 211 ). 
     In one embodiment of the present disclosure, the first image is a DWI, and the second image is an ADC map. 
     In one embodiment of the present disclosure, the plurality of images further includes T1-weighted image (operation S 201 ). The operation S 204  further includes: moving a position of the brain in the T1-weighted image to a center of the T1-weighted image based on an outline of the brain in the T1-weighted image, and then binarizing the T1-weighted image to find a most symmetrical rotation angle of the position of the brain in the T1-weighted image, so as to orientate the T1-weighted image, so that the T1-weighted image is positioned (operation S 204 ). 
     In one embodiment of the present disclosure, operation S 205  further includes: using the T1-weighted image that has been positioned as a basis of image registration for moving and orientating the DWI and the ADC map that have been binarized. 
     In operation S 206 , the image mask process filters out non-brain tissue from the DWI and the ADC map after the image registration. 
     In view of above, technical advantages are generally achieved, by embodiments of the present disclosure. With the technical solution of the present disclosure, the location of the lesion on the MRI can be accurately detected, so that clinicians can efficiently quantify the diagnosis of the MRI in the clinic. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims.