CN112037231A - Medical image liver segmentation post-processing method based on feature classifier - Google Patents

Medical image liver segmentation post-processing method based on feature classifier Download PDF

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CN112037231A
CN112037231A CN202010751090.3A CN202010751090A CN112037231A CN 112037231 A CN112037231 A CN 112037231A CN 202010751090 A CN202010751090 A CN 202010751090A CN 112037231 A CN112037231 A CN 112037231A
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tumor
algorithm
classifier
segmentation
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王伟林
丁元
孙忠权
卜佳俊
顾静军
陈以宁
丁昊
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Zhejiang University ZJU
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    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00Image analysis
    • G06T7/10Segmentation; Edge detection
    • G06T7/11Region-based segmentation
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06FELECTRIC DIGITAL DATA PROCESSING
    • G06F18/00Pattern recognition
    • G06F18/20Analysing
    • G06F18/21Design or setup of recognition systems or techniques; Extraction of features in feature space; Blind source separation
    • G06F18/214Generating training patterns; Bootstrap methods, e.g. bagging or boosting
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06FELECTRIC DIGITAL DATA PROCESSING
    • G06F18/00Pattern recognition
    • G06F18/20Analysing
    • G06F18/24Classification techniques
    • G06F18/241Classification techniques relating to the classification model, e.g. parametric or non-parametric approaches
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00Indexing scheme for image analysis or image enhancement
    • G06T2207/10Image acquisition modality
    • G06T2207/10072Tomographic images
    • G06T2207/10081Computed x-ray tomography [CT]
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00Indexing scheme for image analysis or image enhancement
    • G06T2207/30Subject of image; Context of image processing
    • G06T2207/30004Biomedical image processing
    • G06T2207/30096Tumor; Lesion

Abstract

The invention discloses a medical image liver segmentation post-processing method based on a feature classifier, which judges whether a corresponding tumor block is a real tumor or not by extracting morphological features of the tumor block identified by an algorithm and inputting the morphological features into the classifier, and comprises the following specific steps: s1, extracting morphological characteristics of the interior of the tumor region after algorithm segmentation; s2, training a corresponding classifier; and S3, performing post-processing on the result of the deep learning algorithm recognition by using the trained classifier. The method can be effectively used in the post-processing of the deep learning algorithm on the semantic segmentation recognition of the tumor, and filters out the wrong tumor, thereby improving each index of the recognition result, and simultaneously improving the effect of the algorithm segmentation on the auxiliary diagnosis.

Description

Medical image liver segmentation post-processing method based on feature classifier
Technical Field
The invention belongs to the technical field of energy storage, and particularly relates to a medical image liver segmentation post-processing method based on a feature classifier.
Background
The identification of diseases is often done medically by means of medical images, and the diagnosis assisted by medical images based on artificial intelligence method can assist doctors in the diagnosis of diseases by an algorithm model trained on a large amount of labeled data. The semantic segmentation means that a target region is segmented from an image in a pixel point classification mode, the current artificial intelligence methods such as deep learning are widely applied to semantic segmentation of medical images, and a liver or a pathological change region in the medical images can be extracted in a mode of training a neural network.
However, in the existing deep learning method, some wrong segmentation regions may exist after prediction, that is, some positions which are not tumors are mistakenly identified as tumors. When the number of wrong tumors identified by the algorithm is too large, the effect of the algorithm on the auxiliary identification of doctors is greatly influenced. Improving the recognition accuracy of the deep learning algorithm can reduce the number of recognized error tumors, but this method needs time and labor consuming to conceive a better model and needs stronger calculation for training.
Disclosure of Invention
In order to solve the above problems, the present invention provides a medical image liver segmentation post-processing method based on a feature classifier, which comprises the steps of extracting morphological features of tumor blocks identified by an algorithm, inputting the morphological features into the classifier to judge whether the corresponding tumor blocks are real tumors, and specifically comprises the following steps:
s1, extracting morphological characteristics of the interior of the tumor region after algorithm segmentation;
s2, training a corresponding classifier;
and S3, performing post-processing on the result of the deep learning algorithm recognition by using the trained classifier.
Preferably, the step S1 includes:
s101, training a semantic segmentation deep learning algorithm to identify a liver region and a tumor region in a CT image;
s102, predicting the data of the training set once to obtain a tumor label of the training set, namely whether the tumor is a wrong prediction or not;
s103, extracting the sizes of the tumors in the residual tumor blocks and the corresponding characteristics of all the tumors in the CT;
and S104, if the multi-stage CT exists, aligning the multi-stage CT by using an alignment algorithm, extracting the CT distribution characteristics of the position of the tumor block in each stage, and splicing the characteristics to obtain the characteristic vector of each tumor. And the morphological characteristics of multiple stages are fused and input into a classifier to identify whether the tumor block is a true tumor, and better classification effect can be obtained by using the characteristic data of multiple stages.
Preferably, the corresponding features include CT distribution features such as an average value, a maximum value, a minimum value, a standard deviation, and a skewness of CT pixel values inside the tumor block, an average value of distances from each layer of the tumor block to left, right, upper, and lower boundaries of the liver, and the number of layers corresponding to the upper and lower boundaries of the liver and the number of layers corresponding to the tumor block. The distribution of the CT values of the real tumor generally falls within the corresponding organ, and the CT values within the block contain a certain rule, so that the shape, size and position of the tumor can be used to distinguish whether the tumor is the real tumor.
Preferably, the specific step of S2 is:
s201, classifying the tumor blocks obtained in the S1 and the corresponding labels thereof by using an xgboost algorithm; the xgboost algorithm trains the corresponding model by minimizing the loss function, and the minimizing loss function of the xgboost model is defined as the weighted sum of the loss between the predicted label and the real label of the model on the multiple base classifiers, and the specific formula is as follows:
Figure BDA0002610011810000031
wherein: penalty term
Figure BDA0002610011810000032
T is the number of leaf nodes of the decision tree, ωIs the weight of each node of the tree, and
Figure BDA0002610011810000033
then, the difference loss function between the predicted label and the real label is calculated, and here, we select a binary logistic regression loss function:
Figure BDA0002610011810000034
s202, increasing the scale _ pos _ weight parameter of the algorithm to increase the weight for correctly classifying the positive samples, wherein the specific formula is as follows:
Figure BDA0002610011810000035
the main influence of the parameter on the operation result is to increase the weight of the positive sample after prediction, thereby increasing the influence of the positive sample during the gradient replay; the recall rate of the classifier can be improved as much as possible by increasing the parameters, so that the classifier retains more tumors with correct segmentation.
Preferably, the S3 includes: and (3) extracting corresponding characteristics of each tumor block in the segmentation result output by the algorithm by using a trained classifier, judging whether the tumor block is wrongly segmented, and performing post-processing to remove the tumor block if the tumor block is wrongly segmented to obtain a final segmentation result.
Compared with the prior art, the invention has the beneficial effects that: the method can be effectively used in the post-processing of the deep learning algorithm on the semantic segmentation recognition of the tumor, and the wrong tumor is filtered, so that various indexes of the recognition result such as the dice score are improved, and meanwhile, the effect of the algorithm segmentation on the auxiliary diagnosis can be improved.
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FIG. 1 is a flow chart of the present invention;
FIG. 2 is a detailed algorithmic flow chart of the present invention;
FIG. 3 is a sample effect of the mis-segmentation identification of the present invention FIG. 1;
FIG. 4 is a sample effect of the miscut identification of the present invention FIG. 2;
FIG. 5 is a sample effect of the miscut identification of the present invention FIG. 3;
FIG. 6 is a sample effect of the segmentation error recognition of the present invention in FIG. 4.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention.
As shown in fig. 1 to 6, the present embodiment provides a method for processing after medical image liver segmentation based on a feature classifier, which extracts morphological features of a tumor block identified by an algorithm, inputs the morphological features into the classifier to determine whether the corresponding tumor block is a real tumor, and specifically includes the following steps:
s1, extracting morphological characteristics of the interior of the tumor region after algorithm segmentation;
s2, training a corresponding classifier;
s3, performing post-processing on the result of the deep learning algorithm recognition by using the trained classifier; and (3) extracting corresponding characteristics of each tumor block in the segmentation result output by the algorithm by using a trained classifier, judging whether the tumor block is wrongly segmented, and performing post-processing to remove the tumor block if the tumor block is wrongly segmented to obtain a final segmentation result. Fig. 3 to 6 show the effect diagrams of the cases of the erroneous segmentation recognition near the liver boundary.
The specific method for implementing step S1 in this embodiment includes:
s101, training a semantic segmentation deep learning algorithm to identify a liver region and a tumor region in a CT image;
s102, predicting the data of the training set once to obtain a tumor label of the training set, namely whether the tumor is a wrong prediction or not;
s103, extracting the sizes of the tumors in the residual tumor blocks and the corresponding characteristics of all the tumors in the CT;
and S104, if the multi-stage CT exists, aligning the multi-stage CT by using an alignment algorithm, extracting the CT distribution characteristics of the position of the tumor block in each stage, and splicing the characteristics to obtain the characteristic vector of each tumor.
In order to improve the effect of deep learning and identification and remove redundant erroneous tumors, this task may be regarded as a classification task, and for each tumor, a label of 1 in this embodiment indicates that the tumor is a true tumor, and a label of 0 indicates that the tumor is an erroneously identified tumor. There are many methods to process the classification task, and because the tumors identified by the deep learning algorithm are different in size, this point brings great difficulty to accurately judge whether the tumor block is true, so this embodiment adopts the feature extraction algorithm to classify, and reduces the influence of the tumor size by extracting the morphological statistical features in the region. Under the condition that multi-stage CT (computed tomography) such as a flat scanning stage, a venous stage and an arterial stage exists, a corresponding pixel block in the multi-stage CT can be extracted aiming at a tumor block by combining a multi-stage CT alignment algorithm, the morphological characteristics of the multi-stage CT are fused, and the fused pixel block is input to a classifier to identify whether the tumor block is a true tumor.
The corresponding characteristics comprise CT distribution characteristics such as the average value, the maximum value, the minimum value, the standard deviation, the skewness and the like of CT pixel values in the tumor block, the distance average value of each layer of the tumor block from the left, right and upper boundaries of the liver, the number of layers corresponding to the upper and lower boundaries of the liver and the number of layers corresponding to the tumor block. The distribution of the CT values of the real tumor generally falls within the corresponding organ, and the CT values within the block contain a certain rule, so that the shape, size and position of the tumor can be used to distinguish whether the tumor is the real tumor. Under the condition of multi-stage CT, after alignment, CT characteristics on corresponding positions are extracted from the three stages simultaneously, so that whether the tumor is a real tumor or not can be better identified.
The method adopted by the invention extracts the morphological characteristics of the tumor blocks identified by the algorithm and inputs the morphological characteristics into the xgboost classifier to judge whether the corresponding tumor blocks are real tumors.
The specific operation of training the corresponding classifier in this embodiment is as follows:
s201, classifying the tumor blocks obtained in the S1 and the corresponding labels thereof by using an xgboost algorithm; the xgboost algorithm trains the corresponding model by minimizing the loss function, and the minimizing loss function of the xgboost model is defined as the weighted sum of the loss between the predicted label and the real label of the model on the multiple base classifiers, and the specific formula is as follows:
Figure BDA0002610011810000061
wherein: penalty term
Figure BDA0002610011810000062
T is the number of leaf nodes of the decision tree, ω is the weight of each node of the tree, and
Figure BDA0002610011810000063
then, the difference loss function between the predicted label and the real label is calculated, and here, we select a binary logistic regression loss function:
Figure BDA0002610011810000071
s202, increasing the scale _ pos _ weight parameter of the algorithm to increase the weight for correctly classifying the positive samples, wherein the specific formula is as follows:
Figure BDA0002610011810000072
the main influence of the parameter on the operation result is that the weight of the positive sample after prediction is increased, so that the influence of the positive sample during gradient replay is increased, the recall rate of the classifier can be improved as much as possible by increasing the parameter, and the classifier can keep more tumors with correct segmentation.
It is to be understood that the described embodiments are merely some embodiments of the invention and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Claims (5)

1. The medical image liver segmentation post-processing method based on the feature classifier is characterized in that morphological features of tumor blocks identified by an algorithm are extracted and input into the classifier to judge whether the corresponding tumor blocks are real tumors or not, and the specific steps comprise:
s1, extracting morphological characteristics of the interior of the tumor region after algorithm segmentation;
s2, training a corresponding classifier;
and S3, performing post-processing on the result of the deep learning algorithm recognition by using the trained classifier.
2. The method for post-processing liver segmentation of medical image based on feature classifier as claimed in claim 1, wherein the step S1 includes:
s101, training a semantic segmentation deep learning algorithm to identify a liver region and a tumor region in a CT image;
s102, predicting the data of the training set once to obtain a tumor label of the training set, namely whether the tumor is a wrong prediction or not;
s103, extracting the sizes of the tumors in the residual tumor blocks and the corresponding characteristics of all the tumors in the CT;
and S104, if the multi-stage CT exists, aligning the multi-stage CT by using an alignment algorithm, extracting the CT distribution characteristics of the position of the tumor block in each stage, and splicing the characteristics to obtain the characteristic vector of each tumor.
3. The method of claim 2, wherein the corresponding features include CT distribution features of mean, maximum, minimum, standard deviation and skewness of CT pixel values inside the tumor block, mean distance between each layer of the tumor block and left, right and upper and lower boundaries of the liver, and the number of layers corresponding to the upper and lower boundaries of the liver and the number of layers corresponding to the tumor block.
4. The method for post-processing medical image liver segmentation based on the feature classifier as claimed in claim 1, wherein the step S2 comprises the steps of:
s201, classifying the tumor blocks obtained in the S1 and the corresponding labels thereof by using an xgboost algorithm: the xgboost algorithm trains the corresponding model by minimizing the loss function, and the minimizing loss function of the xgboost model is defined as the weighted sum of the loss between the predicted label and the real label of the model on the multiple base classifiers, and the specific formula is as follows:
Figure FDA0002610011800000021
wherein: penalty term
Figure FDA0002610011800000022
T is the number of leaf nodes of the decision tree, ω is the weight of each node of the tree, and
Figure FDA0002610011800000023
then, the difference loss function of the predicted label and the real label is calculated, and a binary logistic regression loss function is selected:
Figure FDA0002610011800000024
s202, increasing the scale _ pos _ weight parameter of the algorithm to increase the weight for correctly classifying the positive sample, wherein the main influence of the parameter on the operation result is to increase the weight of the positive sample after prediction, so that the influence of the positive sample during gradient replay is increased, and the specific formula is as follows:
Figure FDA0002610011800000025
5. the method for post-processing liver segmentation of medical image based on feature classifier as claimed in claim 1, wherein the step S3 includes: and (3) extracting corresponding characteristics of each tumor block in the segmentation result output by the algorithm by using a trained classifier, judging whether the tumor block is wrongly segmented, and performing post-processing to remove the tumor block if the tumor block is wrongly segmented to obtain a final segmentation result.
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CN110188788A (en) * 2019-04-15 2019-08-30 浙江工业大学 The classification method of cystic Tumor of Pancreas CT image based on radiation group feature
CN110837844A (en) * 2019-09-26 2020-02-25 浙江工业大学 Pancreatic cystic tumor benign and malignant classification method based on CT image dissimilarity characteristics
US20200074632A1 (en) * 2017-04-12 2020-03-05 Kheiron Medical Technologies Ltd Assessment of density in mammography
KR20200082660A (en) * 2018-12-31 2020-07-08 주식회사 메디픽셀 Pathological diagnosis method and apparatus based on machine learning

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20200074632A1 (en) * 2017-04-12 2020-03-05 Kheiron Medical Technologies Ltd Assessment of density in mammography
CN109493362A (en) * 2018-09-03 2019-03-19 李磊 A kind of human body foreground segmentation algorithm of neural network jointing edge detection
KR20200082660A (en) * 2018-12-31 2020-07-08 주식회사 메디픽셀 Pathological diagnosis method and apparatus based on machine learning
CN110188788A (en) * 2019-04-15 2019-08-30 浙江工业大学 The classification method of cystic Tumor of Pancreas CT image based on radiation group feature
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