Feature selection in proton magnetic resonance spectroscopy data of brain tumors

In cancer diagnosis, classification of the different tumor types is of great importance. An accurate prediction of different tumor types provides better treatment and may minimize the negative impact of incorrectly targeted toxic or aggressive treatments. Moreover, the correct prediction of cancer types using non-invasive information –e.g. 1H-MRS data– could avoid patients to suffer collateral problems derived from exploration techniques that require surgery. A Feature Selection Algorithm specially designed to be use in 1H-MRS Proton Magnetic Resonance Spectroscopy data of brain tumors is presented. It takes advantage of a highly distinctive aspect in this data: some metabolite levels are notoriously different between types of tumors. Experimental read- ings on an international dataset show highly competitive models in terms of accuracy, complexity and medical interpretability.Postprint (author’s final draft

Automatic relevance source determination in human brain tumors using Bayesian NMF.

The clinical management of brain tumors is very sensitive; thus, their non-invasive characterization is often preferred. Non-negative Matrix Factorization techniques have been successfully applied in the context of neuro-oncology to extract the underlying source signals that explain different tissue tumor types, for which knowing the number of sources to calculate was always required. In the current study we estimate the number of relevant sources for a set of discrimination problems involving brain tumors and normal brain. For this, we propose to start by calculating a high number of sources using Bayesian NMF and automatically discarding the irrelevant ones during the iterative process of matrices decomposition, hence obtaining a reduced range of interpretable solutions. The real data used in this study come from a widely tested human brain tumor database. Simulated data that resembled the real data was also generated to validate the hypothesis against ground truth. The results obtained suggest that the proposed approach is able to provide a small range of meaningful solutions to the problem of source extraction in human brain tumors

Ανάπτυξη συστημάτων τεχνητής νοημοσύνης για την υποβοήθηση διαφορικής διάγνωσης νόσων εγκεφάλου με χρήση μαγνητικής φασματοσκοπίας και τεχνικών διάχυσης και αιμάτωσης σε υψηλό πεδίο 3Τ

Σημείωση: διατίθεται συμπληρωματικό υλικό σε ξεχωριστό αρχείο

Méthodes d'apprentissage automatique pour la segmentation de tumeurs au cerveau

Abstract : Malignant brain tumors are the second leading cause of cancer related deaths in children under 20. There are nearly 700,000 people in the U.S. living with a brain tumor and 17,000 people are likely to loose their lives due to primary malignant and central nervous system brain tumor every year. To identify whether a patient is diagnosed with brain tumor in a non-invasive way, an MRI scan of the brain is acquired followed by a manual examination of the scan by an expert who looks for lesions (i.e. cluster of cells which deviate from healthy tissue). For treatment purposes, the tumor and its sub-regions are outlined in a procedure known as brain tumor segmentation . Although brain tumor segmentation is primarily done manually, it is very time consuming and the segmentation is subject to variations both between observers and within the same observer. To address these issues, a number of automatic and semi-automatic methods have been proposed over the years to help physicians in the decision making process. Methods based on machine learning have been subjects of great interest in brain tumor segmentation. With the advent of deep learning methods and their success in many computer vision applications such as image classification, these methods have also started to gain popularity in medical image analysis. In this thesis, we explore different machine learning and deep learning methods applied to brain tumor segmentation.Résumé: Les tumeurs malignes au cerveau sont la deuxième cause principale de décès chez les enfants de moins de 20 ans. Il y a près de 700 000 personnes aux États-Unis vivant avec une tumeur au cerveau, et 17 000 personnes sont chaque année à risque de perdre leur vie suite à une tumeur maligne primaire dans le système nerveu central. Pour identifier de façon non-invasive si un patient est atteint d'une tumeur au cerveau, une image IRM du cerveau est acquise et analysée à la main par un expert pour trouver des lésions (c.-à-d. un groupement de cellules qui diffère du tissu sain). Une tumeur et ses régions doivent être détectées à l'aide d'une segmentation pour aider son traitement. La segmentation de tumeur cérébrale et principalement faite à la main, c'est une procédure qui demande beaucoup de temps et les variations intra et inter expert pour un même cas varient beaucoup. Pour répondre à ces problèmes, il existe beaucoup de méthodes automatique et semi-automatique qui ont été proposés ces dernières années pour aider les praticiens à prendre des décisions. Les méthodes basées sur l'apprentissage automatique ont suscité un fort intérêt dans le domaine de la segmentation des tumeurs cérébrales. L'avènement des méthodes de Deep Learning et leurs succès dans maintes applications tels que la classification d'images a contribué à mettre de l'avant le Deep Learning dans l'analyse d'images médicales. Dans cette thèse, nous explorons diverses méthodes d'apprentissage automatique et de Deep Learning appliquées à la segmentation des tumeurs cérébrales

Evaluation of Traumatic Brain Injury Using Magnetic Resonance Spectroscopy

Traumatic brain injury (TBI) is responsible for a third of all injury-related deaths in the United States. With the lack of structural imaging biomarkers available for the detection and evaluation of TBI sequelae, unambiguous diagnosis and prognosis in TBI still remain a huge challenge. Furthermore, complications arising from TBI can lead to cognitive, social, emotional and behavioral defects later in life. Even in confirmed cases of head injury, computed tomography (CT) and conventional MR techniques are limited in their ability to predict the neuropsychological outcome of patients. While the initial trauma can induce structural impairment of brain tissue, the bulk of the cerebral dysfunction ensuing from TBI is due to alterations in cellular biochemical processes that occur in the days and weeks following the traumatic incident. There is therefore a need for advanced imaging modalities that are able to probe the more underlying cellular changes that are induced by TBI. Understanding such cellular changes will be useful in predicting patient outcome and designing interventions to alleviate the injury sequelae. Magnetic Resonance Spectroscopy (MRS) is a non-invasive imaging modality that is capable of detecting cellular metabolic changes in in vivo tissue. In this study we will assess the use of MRS as a clinically relevant tool in the diagnostic and prognostic evaluation of TBI. To this end, we have laid out the following specific aims: (i) To understand the nature and implications of neurometabolic sequelae in mild traumatic brain injury (mTBI) by carrying out cross-sectional comparisons of mTBI patients to neurologically healthy subjects at different stages of injury and to determine associations between early neurometabolic patterns and chronic neuropsychological performance in mTBI patients (ii) To develop novel MRS pulse sequence acquisition and data processing techniques that will enable a more thorough neurometabolic evaluation of TBI and enhance quantification of MRS data (iii) To develop automated classification systems in mTBI using early neurometabolic information that will aid discrimination between subjects with and without injury related sequelae and allow the prediction of symptomatic outcome at the later stages of injury. The research presented herein will help to enhance the utility of MRS in the evaluation of TBI

An automated classification system to determine malignant grades of brain tumour (glioma) in magnetic resonance images based on meta-trainable multiple classifier schemes

The accurate classification of malignant grades of brain tumours is crucial for therapeutic planning as it impacts on the tumour’s prognosis, where the higher the malignancy levels of the brain tumour are, the higher the mortality rate is. It is also essential to provide patients with appropriate clinical management that may prolong survival and improve their quality of life. Determining the malignant grade of a brain tumour is a critical challenge because different malignant grades of brain tumours, in some cases, have inconsistent and mixed morphological characteristics. Consequently, the visual diagnosis using only the naked eye is a very complex and challenging task. The most common type of brain tumour is glioma. According to the World Health Organisation, low-grade glioma, which includes grade I and grade II are the least malignant, slow growing, and respond well to treatment. While, high-grade gliomas, which include grade III and grade IV are extremely malignant, have a poor prognosis and may lead to a high mortality rate. Hence, the motivation to develop an automated classification system to predict the malignant grade of glioma is the aim of this research. To achieve this aim, several novel methods were developed and this includes new methods for the extraction of statistical measures, selection of the dominant predictors, and the fusion of multi-classification models. The integration of these stages generates an accurate and automated decision system to determine the malignant grade of glioma. The feature extraction starts from the viewpoint that the objective measure of the brain tumour descriptors in MR images lead to an accurate classification of malignant brain tumours. This work starts from the standpoint that meta-trainable fusion of multiple classifier models can offer a better classification accuracy to recognise the malignant grade of glioma in MR images. This study developed a novel strategy based on two stages of multiple classifier systems for glioma grades. In the first stage, different machine learning algorithms were used. In the second stage, a systematic trainable combiner was designed based on deep neural networks. This research was validated using four benchmark datasets of MR images, which are publicly available and confirmed with the histopathological diagnosis. The proposed system was also evaluated and compared against different traditional algorithms; the experimental results showed that the proposed system has successfully achieved better and optimal discrimination in glioma grades on all dataset

MR görüntüleri ve MR spektroskopi verileri ile yapay öğrenme tabanlı beyin tümörü tespit yöntemi ve uygulaması

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.Beyinde büyüyen ve gelişen kötü huylu tümörler son zamanlarda insan ölümlerinin en önde gelen nedenlerinden birisi olmaya başlamıştır. Beyin tümörleri için en uygun tedavi yönteminin belirlenmesi hekim tarafından tümörün türünün ve evresinin belirlenmesine bağlıdır. Beyin tümörünün tecrübeli radyologlar tarafından tam olarak teşhis edilebilmesi, Manyetik Rezonans (MR görüntüleri), MR spektroskopi verileri ve patolojik değerlendirmeleri içerisine alan karmaşık bir süreçtir. Genel olarak bir radyolog bu süreçle ilgili olarak önemli doğruluk ve hassaslıkta karar verebiliyor olsa da, hataları en aza indirebilmek için sürekli yeni yöntemler araştırılmaktadır. Bu yüzden radyolog ya da hekimlerin beyin tümörlerinin ayrımını yüksek oranda yapabilecek Bilgisayar Destekli Teşhis (Computer-Aided Detection, CAD / BDT) sistemlerinden yararlanması oldukça önemlidir. Bu tez çalışmasında, hem MR görüntüleri ile hem de MR Spektroskopi (MRS) verileri kullanarak, radyologların karar verme aşamalarında yardımcı olabilecek, beyin tümörlerinin tespitini başarılı bir şekilde yapan yeni bilgisayar destekli yaklaşımlar önerilmiştir. Tez kapsamında geliştirilen ilk yöntem MR görüntüleri üzerinde çalışmakta ve beyin tümörlerinin iyi/kötü huylu ayrımlarını görüntü işleme ve örüntü tanıma teknikleri ile gerçekleştirmektedir. Bu işlemi gerçekleştirmek amacıyla MR görüntüleri üzerinde kafatası kısmını çıkarma için yeni bir görüntü ön-işleme tekniği önerilmiştir. Ayrıca, tümör ayrımlarında sınıflandırıcı etkisini görebilmek için farklı sınıflandırıcıların başarımları kıyaslanmıştır. 188 adet MR görüntüsü üzerinde yapılan detaylı deney sonuçlarına göre, önerilen yöntem ile %96.81 doğruluk oranı ile beyin tümörlerinin iyi / kötü huylu ayrımı gerçekleştirilebilmiştir. Tez kapsamında önerilen bir diğer yöntemde ise, MR spektroskopi sinyalleri üzerinde çalışan ve Yapay Bağışıklık Sistemi (YBS) tabanlı yeni bir BDT yaklaşımı geliştirilmiştir. Önerilen yöntem ile MRS verileri kullanılarak iyi huylu / kötü huylu tümör ayrımı, beyin tümörünün evrelemesi, normal beyin dokusu ile beyin tümörünün ayrımı, metastaz beyin tümörleri ile birincil beyin tümörlerinin ayrımı ve sahte tümörlerin belirlenmesi yüksek başarımla mümkün olmuştur. Çok uluslu ve merkezli bir proje kapsamında elde edilen geniş bir veri seti ile gerçekleştirilen deney sonuçlarına göre sırasıyla %96.97, %100, %100, %98.33 ve %98.44 başarım elde edilmiştir.Malignant tumors growing and developing in the brain have recently become one of the leading causes of death in humans. Determination of the most suitable treatment for brain tumors depends on accurate detection of malignancy, type and grade of the tumor by the physician. Diagnosis of brain tumors by radiologists is a complex process which includes MR images, MR spectroscopy data and pathological assessments. Generally, a radiologist makes a decision with reasonable accuracy and specifity rates. However new methods have been investigated by the researchers to minimize the diagnosis mistakes. Therefore, it is crucial for radiologists or physicians to use a Computer-Aided Diagnosis (CAD) system which will help detection of brain tumors with high success rates. In this thesis, novel computer aided methods, which use MR images and MR Spectroscopy data, have been proposed for the detection of brain tumors to support decision process of the radiologists. The first method developed in the thesis differentiates brain tumors as benign or malignant by image processing and pattern recognition techniques on MR images. To perform this operation, a new image pre-processing technique has been proposed to strip the skull region. Moreover, to evaluate the effect of classifier performance on tumor differentiation, different classifiers have been compared. According to detailed test results performed on 188 MR images, benign or malignant differentiation of brain tumors can be detected with 96.81% accuracy rate by proposed method. In the second method, a novel Artificial Immune System (AIS) based computer-aided diagnosis system has been proposed. This system utilizes MR Spectroscopy signals to make a decision about brain tumors. The system can perform differentiation of benign / malign, metastatic / primary, pseudo / normal tumors and grading of brain tumors with high accuracy rates. According to the experimental results performed on large dataset obtained from an international and multi-center project, the detection performance has been achieved 96.97%, 100%, 100%, 98.33% and 98.44% success rates respectively