Alzheimer's Disease Diagnosis Using Landmark-Based Features From Longitudinal Structural MR Images

Structural magnetic resonance imaging (MRI) has been proven to be an effective tool for Alzheimer’s disease (AD) diagnosis. While conventional MRI-based AD diagnosis typically uses images acquired at a single time point, a longitudinal study is more sensitive in detecting early pathological changes of AD, making it more favorable for accurate diagnosis. In general, there are two challenges faced in MRI-based diagnosis. First, extracting features from structural MR images requires time-consuming nonlinear registration and tissue segmentation, whereas the longitudinal study with involvement of more scans further exacerbates the computational costs. Moreover, the inconsistent longitudinal scans (i.e., different scanning time points and also the total number of scans) hinder extraction of unified feature representations in longitudinal studies. In this paper, we propose a landmark-based feature extraction method for AD diagnosis using longitudinal structural MR images, which does not require nonlinear registration or tissue segmentation in the application stage and is also robust to inconsistencies among longitudinal scans. Specifically, 1) the discriminative landmarks are first automatically discovered from the whole brain using training images, and then efficiently localized using a fast landmark detection method for testing images, without the involvement of any nonlinear registration and tissue segmentation; 2) high-level statistical spatial features and contextual longitudinal features are further extracted based on those detected landmarks, which can characterize spatial structural abnormalities and longitudinal landmark variations. Using these spatial and longitudinal features, a linear support vector machine (SVM) is finally adopted to distinguish AD subjects or mild cognitive impairment (MCI) subjects from healthy controls (HCs). Experimental results on the ADNI database demonstrate the superior performance and efficiency of the proposed method, with classification accuracies of 88.30% for AD vs. HC and 79.02% for MCI vs. HC, respectively

MRI-based prostate cancer detection with high-level representation and hierarchical classification

Extracting the high-level feature representation by using deep neural networks for detection of prostate cancer, and then based on high-level feature representation constructing hierarchical classification to refine the detection results

Automatic Craniomaxillofacial Landmark Digitization via Segmentation-Guided Partially-Joint Regression Forest Model and Multiscale Statistical Features

The goal of this paper is to automatically digitize craniomaxillofacial (CMF) landmarks efficiently and accurately from cone-beam computed tomography (CBCT) images, by addressing the challenge caused by large morphological variations across patients and image artifacts of CBCT images

Detecting Anatomical Landmarks for Fast Alzheimer’s Disease Diagnosis

Structural magnetic resonance imaging (MRI) is a very popular and effective technique used to diagnose Alzheimer’s disease (AD). The success of computer-aided diagnosis methods using structural MRI data is largely dependent on the two time-consuming steps: 1) nonlinear registration across subjects, and 2) brain tissue segmentation. To overcome this limitation, we propose a landmark-based feature extraction method that does not require nonlinear registration and tissue segmentation. In the training stage, in order to distinguish AD subjects from healthy controls (HCs), group comparisons, based on local morphological features, are first performed to identify brain regions that have significant group differences. In general, the centers of the identified regions become landmark locations (or AD landmarks for short) capable of differentiating AD subjects from HCs. In the testing stage, using the learned AD landmarks, the corresponding landmarks are detected in a testing image using an efficient technique based on a shape-constrained regression-forest algorithm. To improve detection accuracy, an additional set of salient and consistent landmarks are also identified to guide the AD landmark detection. Based on the identified AD landmarks, morphological features are extracted to train a support vector machine (SVM) classifier that is capable of predicting the AD condition. In the experiments, our method is evaluated on landmark detection and AD classification sequentially. Specifically, the landmark detection error (manually annotated versus automatically detected) of the proposed landmark detector is 2.41mm, and our landmark-based AD classification accuracy is 83.7%. Lastly, the AD classification performance of our method is comparable to, or even better than, that achieved by existing region-based and voxel-based methods, while the proposed method is approximately 50 times faster

Severity scoring approach using modified optical flow method and lesion identification for facial nerve paralysis assessment

The facial nerve controls facial movement and expression. Hence, a patient with facial nerve paralysis will experience affected social interactions, psychological distress, and low self-esteem. Upon the first presentation, it is crucial to determine the severity level of the paralysis and take out the possibility of stroke or any other serious causes by recognising the type of lesion in preventing any mistreatment of the patient. Clinically, the facial nerve is assessed subjectively by observing voluntary facial movement and assigning a score based on the deductions made by the clinician. However, the results are not uniform among different examiners evaluating the same patients. This is extremely undesirable for both medical diagnostic and treatment considerations. Acknowledging the importance of this assessment, this research was conducted to develop a facial nerve assessment that can classify both the severity level of facial nerve function and also the types of facial lesion, Upper Motor Neuron (UMN) and Lower Motor Neuron (LMN), in facial regional assessment and lesion assessment, respectively. For regional assessment, two optical flow techniques, Kanade-Lucas-Tomasi (KLT) and Horn-Schunck (HS) were used in this study to determine the local and global motion information of facial features. Nevertheless, there is a problem with the original KLT which is the inability of the Eigen features to distinguish the normal and patient subjects. Thus, the KLT method was modified by introducing polygonal measurements and the landmarks were placed on each facial region. Similar to the HS method, the multiple frames evaluation was proposed rather than a single frame evaluation of the original HS method to avoid the differences between frames becoming too small. The features of these modified methods, Modified Local Sparse (MLS) and Modified Global Dense (MGD), were combined, namely the Combined Modified Local-Global (CMLG), to discover both local (certain region) and global (entire image) flow features. This served as the input into the k-NN classifier to assess the performance of each of them in determining the severity level of paralysis. For the lesion assessment, the Gabor filter method was used to extract the wrinkle forehead features. Thereafter, the Gabor features combined with the previous features of CMLG, by focusing only on the forehead region to evaluate both the wrinkle and motion information of the facial features. This is because, in an LMN lesion, the patient will not be able to move the forehead symmetrically during the rising eyebrows movement and unable to wrinkle the forehead due to the damaged frontalis muscle. However, the patient with a UMN lesion exhibits the same criteria as a normal subject, where the forehead is spared and can be lifted symmetrically. The CMLG technique in regional assessment showed the best performance in distinguishing between patient and normal subjects with an accuracy of 92.26% compared to that of MLS and MGD, which were 88.38% and 90.32%, respectively. From the results, some assessment tools were developed in this study namely individual score, total score and paralysis score chart which were correlated with the House-Brackmann score and validated by a medical professional with 91.30% of accuracy. In lesion assessment, the combined features of Gabor and CMLG on the forehead region depicted a greater performance in distinguishing the UMN and LMN lesion of the patient with an accuracy of 89.03% compared to Gabor alone, which was 78.07%. In conclusion, the proposed facial nerve assessment approach consisting of both regional assessment and lesion assessment is capable of determining the level of facial paralysis severity and recognising the type of facial lesion, whether it is a UMN or LMN lesion

Doku tanımada şekil bilgisi kullanarak yeni özniteliklerin elde edilmesi

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Bu tezde, doku tanımada başarılı bir şekilde kullanılan yerel ikili örüntüler (Local Binary Pattern - LBP) öznitelik çıkarım yönteminin komşuluk topolojisi üzerinde çalışılmıştır. LBP, görüntünün gri seviye değerlerini kullanan basit bir öznitelik çıkarım yöntemidir. Görüntüdeki her piksel referans piksel olarak belirlenir ve etrafındaki komşuları dairesel bir topoloji ile seçilir. Bu tez çalışması kapsamında LBP yöntemi ile farklı spiral topolojilere sahip komşuluklar kullanılarak daha anlamlı özniteliklerin elde edilmesi amaçlanmıştır. Ayrıca, özniteliklerin ayırt edici özelliklerini arttırmak amacıyla, spiral topoloji kullanan LBP kodları ile görüntünün kenar bilgileri birleştirilmiştir. Histogram tabanlı öznitelik vektörlerinin sınıflandırılmasında genellikle benzerlik ölçütleri kullanılmaktadır. Yapılan tezde, doku tanımada sınıflandırma aşamasında altuzay tabanlı yöntemler ile tanıma başarımının artırılması hedeflenmiştir. Önerilen öznitelik çıkarım yöntemi, doku tanımada CURet ve UIUC doku veritabanları, yüz tanımada ise AR ve ORL yüz veritabanları üzerinde çeşitli deneyler ile test edilmiştir. Yapılan deneyler sonucunda, CURet doku veritabanında % 99,6'lara varan bir tanıma oranı elde edilmiştir. Farklı LBP varyasyonları ile karşılaştırıldığında, daha iyi sınıflandırma başarımları elde edilmiştir. Ayrıca geliştirdiğimiz öznitelik çıkarım yöntemi ile elde edilen öznitelik vektör boyutunu azaltmak amacıyla yeni bir öznitelik seçim algoritması önerilmiştir. Önerilen yöntemde sınıflar arası varyansın olabildiğince yüksek hale getirilmesi amaçlanmaktadır. Önerilen öznitelik seçimi yönteminin başarımı doku tanımada test edilmiştir. Deney sonuçlarına göre, öznitelik vektörünün boyutu %99'a kadar azaldığında tanıma oranı sadece %0,06 azalmaktadır.In this thesis, neighborhood topology of Local Binary Pattern (LBP) which is used successfully applied in texture recognition is studied. LBP is a simple feature extraction method that uses the gray-level values of an image. Each pixel in the image is determined as the reference pixel and its surrounding neighbors are selected over a circular topology. In this thesis work, by using the LBP method, it is aimed to obtain more meaningful features, by using neighbors with different spiral topologies. In addition, the LBP codes which use spiral topology is concatenated with the edge information of the image to enhance the distinctive characteristics of the features. Similarity measures are generally used to classify histogram-based feature vectors. In this thesis, it is aimed to increase the recognition performance with subspace based methods in the classification stage of texture recognition. Proposed feature extraction method is tested with several experiments on CURet and UIUC texture database in texture recognition, AR and ORL face database in face recognition. As a result of the experiments, the recognition rate is acquired up to %99,6 on CURet texture database. Better classification performances are achieved when compared to the several LBP variations. In addition, a new feature selection algorithm is proposed to reduce the dimension of the feature vectors obtained by the proposed feature extraction method. In the proposed method, it is aimed to make the between-class variance as high as possible. The performance of the proposed feature selection method is tested in texture recognition. The experimental results suggest that, the recognition rate is reduced by only 0.06% when the dimension of the feature vector is reduced up to 99%