The purpose of this study is to develop a machine learning model with the optimal features computed from mammograms to classify suspicious regions as benign and malignant. To this aim, we investigate the benefits of implementing a machine learning approach embedded with a random projection algorithm to generate an optimal feature vector and improve classification performance. A retrospective dataset involving 1,487 cases is used. Among them, 644 cases depict malignant lesions, while the rest 843 cases are benign. The locations of all suspicious regions have been annotated by radiologists before. A computer-aided detection scheme is applied to pre-process the images and compute an initial set of 181 features. Then, three support vector machine (SVM) models are built using the initial feature set and embedded with two feature regeneration methods, namely, principal component analysis and random projection algorithm, to reduce dimensionality of feature space and generate smaller optimal feature vectors. All SVM models are trained and tested using the leave-one-case-out cross-validation method to classify between malignant and benign cases. The data analysis results show that three SVM models yield the areas under ROC curves of AUC = 0.72±0.02, 0.79±0.01 and 0.84±0.018, respectively. Thus, this study demonstrates that applying a random projection algorithm enables to generate optimal feature vectors and significantly improve machine learning model (i.e., SVM) performance (p<0.02) to classify mammographic lesions. The similar approach can also been applied to help more effectively train and improve performance of machine learning models applying to other types of medical image applications.
Developing a computer-aided diagnosis (CAD) scheme to classify between malignant and benign breast lesions can play an important role in improving MRI screening efficacy. This study demonstrates that extracting features from both spatial and frequency domains, and applying an efficient combination of data reduction and classifier methods, had the potential to significantly improve accuracy in classifying between malignant and benign breast masses. By applying our CAD scheme to the testing dataset, we obtained an accuracy of 83.1% for the best combination of data reduction and classification (DNE-SVM).
As the rapid spread of coronavirus disease (COVID-19) worldwide, X-ray chest radiography has also been used to detect COVID-19 infected pneumonia and assess its severity or monitor its prognosis in the hospitals due to its low cost, low radiation dose, and broad accessibility. However, how to more accurately and efficiently detect COVID-19 infected pneumonia and distinguish it from other community-acquired pneumonia remains a challenge. In order to address this challenge, we in this study develop and test a new computer-aided detection and diagnosis (CAD) scheme. It includes pre-processing algorithms to remove diaphragms, normalize X-ray image contrast-to-noise ratio, and generate three input images, which are then linked to a transfer learning based convolutional neural network (VGG16 model) to classify chest X-ray images into three classes of COVID-19 infected pneumonia, other community-acquired pneumonia and normal (non-pneumonia) cases. To this purpose, a publicly available dataset of 8,474 chest X-ray images is used, which includes 415 confirmed COVID-19 infected pneumonia, 5,179 community-acquired pneumonia, and 2,880 non-pneumonia cases. The dataset is divided into two subsets with 90% and 10% of images to train and test the CNN-based CAD scheme. The testing results achieve 93.9% of overall accuracy in classifying three classes and 98.6% accuracy in detecting COVID-19 infected pneumonia cases. The study demonstrates the feasibility of developing a new deep transfer leaning based CAD scheme of chest X-ray images and providing radiologists a potentially useful decision-making supporting tool in detecting and diagnosis of COVID-19 infected pneumonia.
The purpose of this investigation is to verify the feasibility of using deep learning technology to generate an image marker for accurate stratification of cervical cancer patients. For this purpose, a pre-trained deep residual neural network (i.e. ResNet-50) is used as a fixed feature extractor, which is applied to the previously identified cervical tumors depicted on CT images. The features at average pooling layer of the ResNet-50 are collected as initial feature pool. Then discriminant neighborhood embedding (DNE) algorithm is employed to reduce the feature dimension and create an optimal feature cluster. Next, a k-nearest neighbors (k-NN) regression model uses this cluster as input to generate an evaluation score for predicting patient’s response to the planned treatment. In order to assess this new model, we retrospectively assembled the pre-treatment CT images from a number of 97 locally advanced cervical cancer (LACC) patients. The leave one out cross validation (LOOCV) strategy is adopted to train and optimize this new scheme and the receiver operator characteristic curve (ROC) is applied for performance evaluation. The result shows that this new model achieves an area under the ROC curve (AUC) of 0.749 ± 0.064, indicating that the deep neural networks enables to identify the most effective tumor characteristics for therapy response prediction. This investigation initially demonstrates the potential of developing a deep learning based image marker to assist oncologists on categorizing cervical cancer patients for precision treatment.
The purpose of this study is to assess feasibility of applying a new quantitative mammographic imaging marker to predict short-term breast cancer risk. An image dataset involving 1,044 women was retrospectively assembled. Each woman had two sequential “current” and “prior” digital mammography screenings with a time interval from 12 to 18 months. All “prior” images were originally interpreted negative by radiologists. In “current” screenings, 402 women were diagnosed with breast cancer and 642 remained negative. There is no significant difference of BIRADS based mammographic density ratings between three case groups (p >0.6). A new computer-aided image processing scheme was applied to process negative mammograms acquired from the “prior” screenings and compute image features related to the bilateral mammographic density or tissue asymmetry between the left and right breasts. A group of 30 features related to GLCM texture features and a conventional computer-aided detection scheme generated results are extracted from both CC and MLO views. Using a leave-one-case-out cross-validation method, a support vector machine model was developed to produce a new quantitative imaging marker to predict the likelihood of a woman having mammography-detectable cancer in the next subsequent (“current”) screening. When applying the model to classify between 402 positive and 642 negative cases, area under a ROC curve is 0.70−0.02 and the odds ratios is 6.93 with 95% confidence interval of [4.80,10.01]. This study demonstrated feasibility of applying a quantitative imaging marker to predict short-term cancer risk, which aims to help establish a new paradigm of personalized breast cancer screening.
Deep convolutional neural networks (CNNs) based transfer learning is an effective tool to reduce the dependence on hand-crafted features for handling medical classification problems, which may mitigate the problem of the insufficient training caused by the limited sample size. In this study, we investigated the discrimination power of the features at different CNN levels for the task of classifying epithelial and stromal regions on digitized pathologic slides which are prepared from breast cancer tissue. We extracted the low level and high level features from four different deep CNN architectures namely, AlexNet, Places365-AlexNet, VGG, and GoogLeNet. These features are used as input to train and optimize different classifiers including support vector machine (SVM), random forest (RF), and k-nearest neighborhood (KNN). A number of 15000 regions of interest (ROIs) acquired from the public database are employed to conduct this study. The result was observed that the low-level features of AlexNet, Places365-AlexNet and VGG outperformed the high-level ones, but the situation is in the opposite direction when the GoogLeNet is applied. Moreover, the best accuracy was achieved as 89.7% by the relatively deep layer of max pool 4 of GoogLeNet. In summary, our extensive empirical evaluation may suggest that it is viable to extend the use of transfer learning to the development of high-performance detection and diagnosis systems for medical imaging tasks.
Both conventional and deep machine learning has been used to develop decision-support tools applied in medical imaging informatics. In order to take advantages of both conventional and deep learning approach, this study aims to investigate feasibility of applying a locally preserving projection (LPP) based feature regeneration algorithm to build a new machine learning classifier model to predict short-term breast cancer risk. First, a computer-aided image processing scheme was used to segment and quantify breast fibro-glandular tissue volume. Next, initially computed 44 image features related to the bilateral mammographic tissue density asymmetry were extracted. Then, an LLP-based feature combination method was applied to regenerate a new operational feature vector using a maximal variance approach. Last, a k-nearest neighborhood (KNN) algorithm based machine learning classifier using the LPP-generated new feature vectors was developed to predict breast cancer risk. A testing dataset involving negative mammograms acquired from 500 women was used. Among them, 250 were positive and 250 remained negative in the next subsequent mammography screening. Applying to this dataset, LLP-generated feature vector reduced the number of features from 44 to 4. Using a leave-onecase-out validation method, area under ROC curve produced by the KNN classifier significantly increased from 0.62 to 0.68 (p < 0.05) and odds ratio was 4.60 with a 95% confidence interval of [3.16, 6.70]. Study demonstrated that this new LPP-based feature regeneration approach enabled to produce an optimal feature vector and yield improved performance in assisting to predict risk of women having breast cancer detected in the next subsequent mammography screening.
Objective of this study is to develop and test a new computer-aided detection (CAD) scheme with improved region of interest (ROI) segmentation combined with an image feature extraction framework to improve performance in predicting short-term breast cancer risk. A dataset involving 570 sets of "prior" negative mammography screening cases was retrospectively assembled. In the next sequential "current" screening, 285 cases were positive and 285 cases remained negative. A CAD scheme was applied to all 570 "prior" negative images to stratify cases into the high and low risk case group of having cancer detected in the "current" screening. First, a new ROI segmentation algorithm was used to automatically remove useless area of mammograms. Second, from the matched bilateral craniocaudal view images, a set of 43 image features related to frequency characteristics of ROIs were initially computed from the discrete cosine transform and spatial domain of the images. Third, a support vector machine model based machine learning classifier was used to optimally classify the selected optimal image features to build a CAD-based risk prediction model. The classifier was trained using a leave-one-case-out based cross-validation method. Applying this improved CAD scheme to the testing dataset, an area under ROC curve, AUC = 0.70±0.04, which was significantly higher than using the extracting features directly from the dataset without the improved ROI segmentation step (AUC = 0.63±0.04). This study demonstrated that the proposed approach could improve accuracy on predicting short-term breast cancer risk, which may play an important role in helping eventually establish an optimal personalized breast cancer paradigm.
Higher recall rates are a major challenge in mammography screening. Thus, developing computer-aided diagnosis (CAD) scheme to classify between malignant and benign breast lesions can play an important role to improve efficacy of mammography screening. Objective of this study is to develop and test a unique image feature fusion framework to improve performance in classifying suspicious mass-like breast lesions depicting on mammograms. The image dataset consists of 302 suspicious masses detected on both craniocaudal and mediolateral-oblique view images. Amongst them, 151 were malignant and 151 were benign. The study consists of following 3 image processing and feature analysis steps. First, an adaptive region growing segmentation algorithm was used to automatically segment mass regions. Second, a set of 70 image features related to spatial and frequency characteristics of mass regions were initially computed. Third, a generalized linear regression model (GLM) based machine learning classifier combined with a bat optimization algorithm was used to optimally fuse the selected image features based on predefined assessment performance index. An area under ROC curve (AUC) with was used as a performance assessment index. Applying CAD scheme to the testing dataset, AUC was 0.75±0.04, which was significantly higher than using a single best feature (AUC=0.69±0.05) or the classifier with equally weighted features (AUC=0.73±0.05). This study demonstrated that comparing to the conventional equal-weighted approach, using an unequal-weighted feature fusion approach had potential to significantly improve accuracy in classifying between malignant and benign breast masses.
The objective of this study is to investigate the performance of global and local features to better estimate the characteristics of highly heterogeneous metastatic tumours, for accurately predicting the treatment effectiveness of the advanced stage ovarian cancer patients. In order to achieve this , a quantitative image analysis scheme was developed to estimate a total of 103 features from three different groups including shape and density, Wavelet, and Gray Level Difference Method (GLDM) features. Shape and density features are global features, which are directly applied on the entire target image; wavelet and GLDM features are local features, which are applied on the divided blocks of the target image. To assess the performance, the new scheme was applied on a retrospective dataset containing 120 recurrent and high grade ovary cancer patients. The results indicate that the three best performed features are skewness, root-mean-square (rms) and mean of local GLDM texture, indicating the importance of integrating local features. In addition, the averaged predicting performance are comparable among the three different categories. This investigation concluded that the local features contains at least as copious tumour heterogeneity information as the global features, which may be meaningful on improving the predicting performance of the quantitative image markers for the diagnosis and prognosis of ovary cancer patients.
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