KEYWORDS: Data modeling, Computed tomography, Performance modeling, Blood, Feature extraction, Deep learning, Process modeling, Image classification, Deep convolutional neural networks
Accurately predicting the clinical outcome of patients with aneurysmal subarachnoid hemorrhage (aSAH) presents notable challenges. This study sought to develop and assess a Computer-Aided Detection (CAD) scheme employing a deep-learning classification architecture, utilizing brain Computed Tomography (CT) images to forecast aSAH patients' prognosis. A retrospective dataset encompassing 60 aSAH patients was collated, each with two CT images acquired upon admission and after ten to 14 days of admission. The existing CAD scheme was utilized for preprocessing and data curation based on the presence of blood clot in the cisternal spaces. Two pre-trained architectures, DenseNet-121 and VGG16, were chosen as convolutional bases for feature extraction. The Convolution Based Attention Module (CBAM) was introduced atop the pre-trained architecture to enhance focus learning. Employing five-fold cross-validation, the developed prediction model assessed three clinical outcomes following aSAH, and its performance was evaluated using multiple metrics. A comparison was conducted to analyze the impact of CBAM. The prediction model trained using CT images acquired at admission demonstrated higher accuracy in predicting short-term clinical outcomes. Conversely, the model trained using CT images acquired on ten to 14 days accurately predicted long-term clinical outcomes. Notably, for short-term outcomes, high sensitivity performances (0.87 and 0.83) were reported from the first scan, while the sensitivity of (0.65 and 0.75) was reported from the last scan, showcasing the viability of predicting the prognosis of aSAH patients using novel deep learning-based quantitative image markers. The study demonstrated the potential of integrating deep-learning architecture with attention mechanisms to optimize predictive capabilities in identifying clinical complications among patients with aSAH.
Applying computer-aided detection (CAD) generated quantitative image markers has demonstrated significant advantages than using subjectively qualitative assessment in supporting translational clinical research. However, although many advanced CAD schemes have been developed, due to heterogeneity of medical images, achieving high scientific rigor of “black-box” type CAD schemes trained using small datasets remains a big challenge. In order to support and facilitate research effort and progress of physician researchers using quantitative imaging markers, we investigated and tested an interactive approach by developing CAD schemes with interactive functions and visual-aid tools. Thus, unlike fully automated CAD schemes, our interactive CAD tools allow users to visually inspect image segmentation results and provide instruction to correct segmentation errors if needed. Based on users’ instruction, CAD scheme automatically correct segmentation errors, recompute image features and generate machine learning-based prediction scores. We have installed three interactive CAD tools in clinical imaging reading facilities to date, which support and facilitate oncologists to acquire image markers to predict progression-free survival of ovarian cancer patients undergoing angiogenesis chemotherapies, and neurologists to compute image markers and prediction scores to assess prognosis of patients diagnosed with aneurysmal subarachnoid hemorrhage and acute ischemic stroke. Using these ICAD tools, clinical researchers have conducted several translational clinical studies by analyzing several diverse study cohorts, which have resulted in publishing seven peer-reviewed papers in clinical journals in the last three years. Additionally, feedbacks from physician researchers also indicate their increased confidence in using new quantitative image markers and help medical imaging researchers further improve or optimize interactive CAD tools.
Radiomics and deep transfer learning have been attracting broad research interest in developing and optimizing CAD schemes of medical images. However, these two technologies are typically applied in different studies using different image datasets. Advantages or potential limitations of applying these two technologies in CAD applications have not been well investigated. This study aims to compare and assess these two technologies in classifying breast lesions. A retrospective dataset including 2,778 digital mammograms is assembled in which 1,452 images depict malignant lesions and 1,326 images depict benign lesions. Two CAD schemes are developed to classify breast lesions. First, one scheme is applied to segment lesions and compute radiomics features, while another scheme applies a pre-trained residual net architecture (ResNet50) as a transfer learning model to extract automated features. Next, the same principal component algorithm (PCA) is used to process both initially computed radiomics and automated features to create optimal feature vectors by eliminating redundant features. Then, several support vector machine (SVM)-based classifiers are built using the optimized radiomics or automated features. Each SVM model is trained and tested using a 10-fold cross-validation method. Classification performance is evaluated using area under ROC curve (AUC). Two SVMs trained using radiomics and automated features yield AUC of 0.77±0.02 and 0.85±0.02, respectively. In addition, SVM trained using the fused radiomics and automated features does not yield significantly higher AUC. This study indicates that (1) using deep transfer learning yields higher classification performance, and (2) radiomics and automated features contain highly correlated information in lesion classification.
Computer-aided detection and/or diagnosis (CAD) schemes typically include machine learning classifiers trained using handcrafted features. The objective of this study is to investigate the feasibility of identifying and applying a new quantitative imaging marker to predict survival of gastric cancer patients. A retrospective dataset including CT images of 403 patients is assembled. Among them, 162 patients have more than 5-year survival. A CAD scheme is applied to segment gastric tumors depicted in multiple CT image slices. After gray-level normalization of each segmented tumor region to reduce image value fluctuation, we used a special feature selection library of a publicly available Pyradiomics software to compute 103 features. To identify an optimal approach to predict patient survival, we investigate two logistic regression model (LRM) generated imaging markers. The first one fuses image features computed from one CT slice and the second one fuses the weighted average image features computed from multiple CT slices. Two LRMs are trained and tested using a leave-one-case-out cross-validation method. Using the LRM-generated prediction scores, receiving operating characteristics (ROC) curves are computed and the area under ROC curve (AUC) is used as index to evaluate performance in predicting patients’ survival. Study results show that the case prediction-based AUC values are 0.70 and 0.72 for two LRM-generated image markers fused with image features computed from a single CT slide and multiple CT slices, respectively. This study demonstrates that (1) radiomics features computed from CT images carry valuable discriminatory information to predict survival of gastric cancer patients and (2) fusion of quasi-3D image features yields higher prediction accuracy than using simple 2D image features.
Computer-Aided Diagnosis (CAD) schemes used to classify suspicious breast lesions typically include machine learning classifiers that are trained using features computed from either the segmented lesions or fixed regions of interest (ROIs) covering the lesions. Both methods have advantages and disadvantages. In this study, we investigate a new approach to train a machine learning classifier that fuses image features computed from both the segmented lesions and the fixed ROIs. We assembled a dataset with 2,000 mammograms. Based on lesion center, a ROI is extracted from each image. Among them, 1,000 ROIs depict verified malignant lesions and rest include benign lesions. An adaptive multilayer region growing algorithm is applied to segment suspicious lesions. Several sets of statistical features, texture features based on GLRLM, GLDM and GLCM, Wavelet transformed features and shape-based features are computed from the original ROI and segmented lesion, respectively. Three support vector machines (SVM) are trained using features computed from original ROIs, segmented lesions, and fusion of both, respectively, using a 10-fold cross-validation method embedded with a feature reduction method, namely a random projection algorithm. By applying the area under the ROC curve (AUC) as an evaluation index, our study results reveal no significant difference between AUC values computed using classification scores generated by two SVMs trained with features computed from original ROIs or segmented lesions. However, utilizing the fused features, AUC of SVM increases more than 10% (p<0.05). This study demonstrates that image features computed using the segmented lesions and the fixed ROIs contain complementary discriminatory information. Thus, fusing these features can significantly improve CAD performance.
Applications of artificial intelligence (AI) in medical imaging informatics have attracted broad research interest. In ophthalmology, for example, automated analysis of retinal fundus photography helps diagnose and monitor illnesses like glaucoma, diabetic retinopathy, hypertensive retinopathy, and cancer. However, building a robust AI model requires a large and diverse dataset for training and validation. While large number of fundus photos are available online, collecting them to create a clean, well-structured dataset is a difficult and manually intensive process. In this work, we propose a two-stage deep-learning system to automatically identify clean retinal fundus images and delete images with severe artifacts. In two stages, two transfer-learning models based the ResNet-50 architecture pre-trained using ImageNet data are built with Increased threshold values on SoftMax to reduce false positives. The first stage classifier identifies “easy” images, and the remaining “difficult” (or undetermined) images are further identified by the second stage classifier. Using the Google Search Engine, we initially retrieve 1,227 retinal fundus images. Using this two-stage deep-learning model yields a positive predictive value (PPV) of 98.56% for the target class compared to a single-stage model with a PPV of 95.74%. The two-stage model helps reduce by two-thirds the false positives for the retinal fundus image class. The PPV over all classes increases from 91.9% to 96.6% without compromising the number of images classified by the model. The superior performance of this two-stage model indicates that the building of an optimal training dataset can play an important role in increasing performance of deep-learning models.
Although volumetric assessment of intracerebral hemorrhage (ICH) plays a key role for clinicians to make optimal treatment decisions and predict prognosis of ICH patients, qualitative assessment of neuroradiologists in reading brain CT images is not accurate and has large interreader variability. To overcome this clinical challenge, this study develops and tests a new interactive computer-aided detection (ICAD) tool to quantitatively assess hemorrhage volumes. A retrospectively assembled dataset including 200 patients with ICH was collected for this study. After loading each case, the ICAD tool first segments intracranial brain volume, performs CT labelling of each voxel, then contour-guided image-thresholding techniques based on CT Hounsfield Unit is used to estimate and segment hemorrhage-associated voxels (ICH). Next, two experienced neurology residents examine and corrects the markings of ICH categorized into either intraparenchymal hemorrhage (IPH) or intraventricular hemorrhage (IVH) to obtain the true markings. Additionally, volumes and maximum two-dimensional diameter of each sub-type of hemorrhage were also computed for understanding ICH prognosis. The performance to segment hemorrhage regions between semi-automated ICAD and the verified neurology residents’ true markings was evaluated using dice similarity coefficient (DSC). Data analysis results show that median and [interquartile range] of DSC are 0.96 [0.91, 0.98], 0.97 [0.93, 0.99], 0.92 [0.83, 0.97] for ICH, IPH and IVH, respectively. Thus, this study demonstrates that the new ICAD tool enables to segment and quantify ICH and other hemorrhage volume with higher DSC, which has potential to quantify ICH in future clinical practice.
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.
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.
Brain computed tomography (CT) images have been routinely used by neuroradiologists in diagnosis of aneurysmal subarachnoid hemorrhage (aSAH). The purpose of this study is to develop a computer-aided detection (CAD) scheme to generate quantitative image markers computed from CT images to predict various clinical measures after aSAH. A CT image dataset involving 59 aSAH patients was retrospectively collected and used. For each patient, non-contrast CT acquired during admission into hospital is used for this study. From each CT image set, CAD scheme segments intracranial brain region, and labels each CT voxel into one of four regions namely, cerebrospinal fluid, white matter, grey matter, and leaked blood. For image slices above the level of the lateral ventricles, cerebrospinal fluid regions are also defined as sulci regions. Nest, CAD scheme computes 9 image features related to the volumes of the segmented sulci, blood, white and gray matter, as well as their ratios. We then built machine learning (ML) models by fusion of these features to predict 5 clinical measures including Delayed Cerebral Ischemia, Clinical Vasospasm, Ventriculoperitoneal Shunting, Modified Rankin Scale and Montreal Cognitive Assessment to assess prognosis of aSAH patients. Based on a leave-one-case-out cross-validation method, ML models yield performance of predicting the 5 selected clinical measures with the areas under ROC curves (AUC) ranging from 0.658 to 0.825. Study results demonstrate the promising feasibility of applying CAD-based image processing and machine learning method to generate valuably quantitative image markers and potential to assist clinicians optimally diagnosing and treating aSAH patients.
Developing radiomic based machine learning models has drawn considerable attention in recent years. However, identifying a small and optimal feature vector to build a robust machine learning models has always been a controversial issue. In this study, we investigated the feasibility of applying a random projection algorithm to create an optimal feature vector from the CAD-generated large feature pool and improve the performance of the machine learning model. We assemble a retrospective dataset involving abdominal computed tomography (CT) images acquired from 188 patients diagnosed with gastric cancer. Among them, 141 cases have peritoneal metastasis (PM), while 47 cases do not have PM. A computer-aided detection (CAD) scheme is applied to segment the gastric tumor area and computes 325 image features. Then, two Logistic Regression models embedded with two different feature dimensionality reduction methods, namely, the principal component analysis (PCA) and a random projection algorithm (RPA). Afterward, a synthetic minority oversampling technique (SMOTE) is used to balance the dataset. The proposed ML model is built to predict the risk of the patients having advanced gastric cancer (AGC). All Logistic Regression models are trained and tested using a leave-one-case-out cross-validation method. Results show that the logistic regression embedded with RPA yielded a significantly higher AUC value (0.69±0.025) than using PCA (0.62±0.014) (p<0.05). The study demonstrated that CT images of the gastric tumors contain discriminatory information to predict the risk of PM in AGC patients, and RPA is a promising method to generate optimal feature vector, improving the performance of ML models of medical images.
The purpose of this study is to assess feasibility of developing a new case-based computer-aided diagnosis (CAD) scheme of mammograms based on a tree-based analysis of SSIM characteristics of the matched bilateral local areas of left and right breasts to predict likelihood of cases being malignant. We assembled a dataset involving screening mammograms acquired from 1000 patients. Among them, 500 cases were positive with cancer detected and verified, while other 500 cases had benign masses. Both CC and MLO view of the mammograms were used for feature extraction in this study. A CAD scheme was applied to preprocess the bilateral mammograms of the left and right breasts, generate image maps in the special domain, compute SSIM-based image features between the matched bilateral mammograms, and apply a support vector machine model to classify between malignant and benign cases. For performance evaluation, CAD scheme was trained and tested using a 10-fold cross-validation method. The area under a receiving operating characteristic curve (AUC) was computed as an index of performance evaluation. Using the poll of 12 extracted SSIM features, the CAD scheme yielded a performance level of AUC = 0.84±0.016, which is significantly higher than using each individual SSIM feature for the classification purpose (p < 0.05), and an odds ratio of 19.0 with 95% confidence interval of [15.3, 29.8]. Thus, this study supports the feasibility of applying an innovative method to develop a new case-based CAD scheme without lesion segmentation and demonstrates higher performance of new CAD scheme to classify between malignant and benign mammographic cases.
Advent of advanced imaging technology and better neuro-interventional equipment have resulted in timely diagnosis and effective treatment for acute ischemic stroke (AIS) due to large vessel occlusion (LVO). However, objective clinicoradiologic correlate to identify appropriate candidates and their respective clinical outcome is largely unknown. The purpose of the study is to develop and test a new interactive decision-making support tool to predict severity of AIS prior to thrombectomy using CT perfusion imaging protocol. CT image data of 30 AIS patients with LVO assessed radiologically for their eligibility to undergo mechanical thrombectomy were retrospectively collected and analyzed in this study. First, a computer-aided scheme automatically categorizes images into multiple sequences followed by indexing each slice to specified brain location. Next, consecutive mapping is used for accurate brain region segmentation from skull. The brain is then split into left and right hemispheres, followed by detecting blood in each hemisphere. Additionally, visual tools including segmentation, blood correction, select sequence and index analyzer are implemented for deeper analysis. Last, comparison between blood-volume in each hemisphere over the sequences is made to observe wash-in and wash-out rate of blood flow to assess the extent of damaged and “at risk” brain tissue. By integrating computer-aided scheme into a user graphic interface, the study builds a unique image feature analysis and visualization tool to observe and quantify the delayed or reduced blood flow (brain “at-risk” to develop AIS) in the corresponding hemisphere, which has potential to assist radiologists to quickly visualize and more accurately assess extent of AIS.
Advent of advanced imaging technology and better neuro-interventional equipment have resulted in timely diagnosis and effective treatment for acute ischemic stroke (AIS) due to large vessel occlusion (LVO). However, objective clinicoradiologic correlate to identify appropriate candidates and their respective clinical outcome is largely unknown. The purpose of the study is to develop and test a new computer-aided detection algorithm to quantify region-specific AIS and “at risk” brain volumes prior to thrombectomy using CT perfusion imaging protocol. Fourteen patients with LVO related AIS and assessed radiologically for their eligibility to undergo mechanical thrombectomy was retrospectively analyzed for the study. First, the scheme automatically categorizes images into multiple series of scans acquired from a section of brain. Each image in series is labeled to a specified brain location. Next, image segmentation is performed to separate brain region from skull. The brain is then split into left and right hemispheres, followed by detecting amount of blood in each hemisphere. Last, comparison between amount of blood in each hemisphere over the series of scans is made to observe the wash-in and wash-out rate of blood to assess the extent of already damaged and “at risk” brain tissue. By integrating the scheme into a user graphic interface, the study builds a unique image feature analysis and visualization tool to observe and quantify the delayed or reduced blood flow (brain “at risk” to develop AIS) in the corresponding hemisphere, which has potential to assist radiologists to quickly visualize and more accurately assess the extent of AIS.
Currently, mammography is the only population based breast cancer screening modality. In order to improve efficacy of mammography and increase cancer detection yield, it has been recently attracting extensive research interest to identify new mammographic imaging markers and/or develop novel machine learning models to more accurately assess or predict short-term breast cancer risk. Objective of this study is to explore and test a new quantitative image marker based on the analysis of frequency domain correlation based features between the bilateral asymmetry of image characteristics to predict risk of women having or developing mammography detectable cancer in a short-term. For this purpose, we assembled an image dataset involving 1,042 sets of “prior” negative mammograms. In the next subsequent “current” mammography screening, 402 cases were positive with cancer detected and verified, while 642 cases remained negative. A special computer-aided detection (CAD) scheme was applied to pre-process two bilateral mammograms of the left and right breasts, generate image maps in frequency domain, compute image features, and apply a multi-feature fusion based support vector machine based classifier to predict short-term breast cancer risk. By using a 10-fold crossvalidation method, this CAD based risk model yielded a performance of AUC = 0.72±0.04 (area under a ROC curve) and an odds ratio of 5.92 with 95% confidence interval of [4.32, 8.11]. This study presented a new type of mammographic imaging marker or a machine learning prediction model and demonstrated its feasibility to help predict short-term risk of developing breast cancer using a large and diverse image dataset.
In order to improve the efficacy of cancer treatment, many new therapy methods have been proposed and tested. The purpose of this study is to investigate the feasibility and potential advantages of using a low-cost, portable and easy-touse ultrasound imaging modality to quantitatively assess treatment efficacy and/or identify optimal treatment methods. For this purpose, we developed a new interactive computer-aided detection (CAD) scheme based image segmentation and feature analysis scheme, which extracts quantitative image features from ultrasound images of athymic nude mice embedded with tumors. Twenty-three mice were involved in this study and treated using 7 different thermal therapy methods. The longitudinal ultrasound images of mice were taken pre- and post-treatment after 3-days of tumor embedment. A graphic user interface (GUI) of the CAD scheme allows manual segmentation of the tumor regions depicting on the images. Two CAD-computed tumor image feature pools were then established including the features computed from (1) pre-treatment images only and (2) difference between post- and pre-treatment images. Through data analysis, a number of top image features were identified to predict the effectiveness of treatment methods. Pearson Correlation coefficients between two top features selected from above two feature pools versus tumor size increase ratio were 0.373 and 0.552, respectively. Using an equally weighted fusion method of the top two features computed from pre- and post-treatment images, correlation coefficient increased to 0.679. Study results demonstrated the feasibility of extracting a new quantitative imaging marker from ultrasound images to assist in the evaluation of treatment efficacy or tumor response to the treatment.
Since conventional computer-aided detection (CAD) schemes of mammograms produce high false positive detection rates, radiologists often ignore CAD-cued suspicious regions, in particular, the mass-type regions, which reduces the application value of CAD in clinical practice. The objective of this study is to investigate a new hypothesis that CAD-generated detection results may be useful and have a positive association to the mammographic cases with a high risk of being positive for cancer. To test this hypothesis, a large and diverse image dataset including mammograms acquired from 2,349 women was retrospectively assembled. Among them, 882 are positive and 1,467 are negative. Each case involves 4 images of craniocaudal (CC) and mediolateral oblique (MLO) view of the left and right breasts. A CAD scheme was applied to process all mammograms. From CAD results, a number of bilateral difference features from the matched CC and MLO view images of right and left breasts were computed. We analyzed discriminatory power to predict the risk of cases being positive using the bilateral difference features and a multi-feature fusion based Logistic-Regression machine learning classifier. By using a leave-onecase- out cross-validation method, the area under the ROC curve of the classifier for the multi-feature fusion was AUC=0.660 ±0.012. By applying an operating threshold at 0.5, the overall prediction accuracy was 67% and the odds ratio was 4.794 with a statistically significant increasing trend (p<0.01). Study results indicated that from CAD-generated false-positives, we enabled to generate a new quantitative imaging marker to predict higher risk cases being positive and cue a case-based warning sign.
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.
By taking advantages of both mammography and breast MRI, contrast-enhanced digital mammography (CEDM) has emerged as a new promising imaging modality to improve efficacy of breast cancer screening and diagnosis. The primary objective of study is to develop and evaluate a new computer-aided detection and diagnosis (CAD) scheme of CEDM images to classify between malignant and benign breast masses. A CEDM dataset consisting of 111 patients (33 benign and 78 malignant) was retrospectively assembled. Each case includes two types of images namely, low-energy (LE) and dual-energy subtracted (DES) images. First, CAD scheme applied a hybrid segmentation method to automatically segment masses depicting on LE and DES images separately. Optimal segmentation results from DES images were also mapped to LE images and vice versa. Next, a set of 109 quantitative image features related to mass shape and density heterogeneity was initially computed. Last, four multilayer perceptron-based machine learning classifiers integrated with correlationbased feature subset evaluator and leave-one-case-out cross-validation method was built to classify mass regions depicting on LE and DES images, respectively. Initially, when CAD scheme was applied to original segmentation of DES and LE images, the areas under ROC curves were 0.7585±0.0526 and 0.7534±0.0470, respectively. After optimal segmentation mapping from DES to LE images, AUC value of CAD scheme significantly increased to 0.8477±0.0376 (p<0.01). Since DES images eliminate overlapping effect of dense breast tissue on lesions, segmentation accuracy was significantly improved as compared to regular mammograms, the study demonstrated that computer-aided classification of breast masses using CEDM images yielded higher performance.
Identifying and developing new mammographic imaging markers to assist prediction of breast cancer risk has been attracting extensive research interest recently. Although mammographic density is considered an important breast cancer risk, its discriminatory power is lower for predicting short-term breast cancer risk, which is a prerequisite to establish a more effective personalized breast cancer screening paradigm. In this study, we presented a new interactive computer-aided detection (CAD) scheme to generate a new quantitative mammographic imaging marker based on the bilateral mammographic tissue density asymmetry to predict risk of cancer detection in the next subsequent mammography screening. An image database involving 1,397 women was retrospectively assembled and tested. Each woman had two digital mammography screenings namely, the “current” and “prior” screenings with a time interval from 365 to 600 days. All “prior” images were originally interpreted negative. In “current” screenings, these cases were divided into 3 groups, which include 402 positive, 643 negative, and 352 biopsy-proved benign cases, respectively. There is no significant difference of BIRADS based mammographic density ratings between 3 case groups (p < 0.6). When applying the CAD-generated imaging marker or risk model to classify between 402 positive and 643 negative cases using “prior” negative mammograms, the area under a ROC curve is 0.70±0.02 and the adjusted odds ratios show an increasing trend from 1.0 to 8.13 to predict the risk of cancer detection in the “current” screening. Study demonstrated that this new imaging marker had potential to yield significantly higher discriminatory power to predict short-term breast cancer risk.
Breast density has been widely considered as an important risk factor for breast cancer. The purpose of this study is to examine the association between mammogram density results and background parenchymal enhancement (BPE) of breast MRI. A dataset involving breast MR images was acquired from 65 high-risk women. Based on mammography density (BIRADS) results, the dataset was divided into two groups of low and high breast density cases. The Low-Density group has 15 cases with mammographic density (BIRADS 1 and 2), while the High-density group includes 50 cases, which were rated by radiologists as mammographic density BIRADS 3 and 4. A computer-aided detection (CAD) scheme was applied to segment and register breast regions depicted on sequential images of breast MRI scans. CAD scheme computed 20 global BPE features from the entire two breast regions, separately from the left and right breast region, as well as from the bilateral difference between left and right breast regions. An image feature selection method namely, CFS method, was applied to remove the most redundant features and select optimal features from the initial feature pool. Then, a logistic regression classifier was built using the optimal features to predict the mammogram density from the BPE features. Using a leave-one-case-out validation method, the classifier yields the accuracy of 82% and area under ROC curve, AUC=0.81±0.09. Also, the box-plot based analysis shows a negative association between mammogram density results and BPE features in the MRI images. This study demonstrated a negative association between mammogram density and BPE of breast MRI images.
Predicting metastatic tumor response to chemotherapy at early stage is critically important for improving efficacy of clinical trials of testing new chemotherapy drugs. However, using current response evaluation criteria in solid tumors (RECIST) guidelines only yields a limited accuracy to predict tumor response. In order to address this clinical challenge, we applied Radiomics approach to develop a new quantitative image analysis scheme, aiming to accurately assess the tumor response to new chemotherapy treatment, for the advanced ovarian cancer patients. During the experiment, a retrospective dataset containing 57 patients was assembled, each of which has two sets of CT images: pre-therapy and 4-6 week follow up CT images. A Radiomics based image analysis scheme was then applied on these images, which is composed of three steps. First, the tumors depicted on the CT images were segmented by a hybrid tumor segmentation scheme. Then, a total of 115 features were computed from the segmented tumors, which can be grouped as 1) volume based features; 2) density based features; and 3) wavelet features. Finally, an optimal feature cluster was selected based on the single feature performance and an equal-weighed fusion rule was applied to generate the final predicting score. The results demonstrated that the single feature achieved an area under the receiver operating characteristic curve (AUC) of 0.838±0.053. This investigation demonstrates that the Radiomic approach may have the potential in the development of high accuracy predicting model for early stage prognostic assessment of ovarian cancer patients.
Accurate tumor segmentation is a critical step in the development of the computer-aided detection (CAD) based quantitative image analysis scheme for early stage prognostic evaluation of ovarian cancer patients. The purpose of this investigation is to assess the efficacy of several different methods to segment the metastatic tumors occurred in different organs of ovarian cancer patients. In this study, we developed a segmentation scheme consisting of eight different algorithms, which can be divided into three groups: 1) Region growth based methods; 2) Canny operator based methods; and 3) Partial differential equation (PDE) based methods. A number of 138 tumors acquired from 30 ovarian cancer patients were used to test the performance of these eight segmentation algorithms. The results demonstrate each of the tested tumors can be successfully segmented by at least one of the eight algorithms without the manual boundary correction. Furthermore, modified region growth, classical Canny detector, and fast marching, and threshold level set algorithms are suggested in the future development of the ovarian cancer related CAD schemes. This study may provide meaningful reference for developing novel quantitative image feature analysis scheme to more accurately predict the response of ovarian cancer patients to the chemotherapy at early stage.
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