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Ce mémoire est une étude d’un cas de rapprochement entre deux pays. Pendant la guerre de Crimée, la Grande-Bretagne s’allia à la France du Second Empire. Ennemie traditionnelle, la France est toujours considérée comme une menace. La coopération forcée entre les deux pays, résultat des circonstances, est à la base de la présente recherche. Des milliers de militaires et de civils des deux pays travaillèrent ensemble pendant deux ans. Les correspondances britanniques révèlent une fraternisation plus importante que ce qui est relevé dans l’historiographie. D’après les théories de Gordon Allport sur la diminution des préjugés, toutes les conditions nécessaires à un rapprochement se retrouvaient en Crimée. Les étapes, définies par Allport, qui mènent à cette fraternisation se perçoivent aussi dans les lettres personnelles. Ce rapprochement eut des conséquences sous-estimées : les Britanniques se comparèrent aux Français et leur fierté céda la place à une importante autocritique. Cela déclencha des controverses dans l’armée et dans les journaux dès le début de la guerre, longtemps avant les scandales de l’hiver 1854-1855. / In the Crimean war, Great-Britain made an alliance with the Second French Empire, the traditional enemy, still considered as a threat; this cooperation, forced by circumstances, forms the basis of this research. Thousands of soldiers and civilians from both countries worked together for two years. The British personal letters reveal a fraternization between both cultures that is more important than the one mentioned in the historiography. According to Gordon Allport’s theories on the diminution of prejudices, all the necessary conditions for reconciliation could be found in Crimea. The steps leading to the fraternization, defined by Allport, are also perceptible in the personal letters. This reconciliation had under-estimated consequences: British soldiers and civilians started comparing themselves with the French and their pride gave place to an important self-criticism. This led to scandals in the army and the newspapers from the very beginning of the war, long before the scandals of the winter 1854-1855.

Grâce aux concepts développés par l’histoire du genre et des femmes, ce mémoire cherche à jeter un regard nouveau sur le parcours de la courtisane libertine du XVIIe siècle Anne de Lenclos, surnommée Ninon. C’est que l’image qui a été véhiculée de Ninon depuis le XVIIIe siècle ne rend pas compte de la complexité du personnage : elle ne met l’accent que sur sa liberté sexuelle, ou au contraire, sur son intelligence et son rôle dans la vie littéraire du Grand Siècle. Une relecture de la correspondance de la courtisane et des documents notariés (actes économiques, testament et inventaire après-décès) la concernant permet cependant de mettre au jour le portrait d’une femme de tête bien différente de celle qui avait jusqu’alors été décrite, réussissant à concilier les transgressions qu’elle n’a cessé de commettre contre l’ordre établi jusqu’à la fin de sa vie à la réputation d’une salonnière admirée et respectée. / Thanks to the concepts developed by the gender history, this Master's thesis seeks to re-evaluate the life of the seventeenth century libertine courtesan Anne de Lenclos, known as Ninon. The courtesan’s image promoted since the eighteenth century doesn’t reveal the complexity of the character: it only focuses on Ninon’s sexual behaviours or on her intellectual abilities and her role in the literary life of the “Grand Siècle”. A new reading of the courtesan’s correspondence and notarial acts (economical acts, testament, post-mortem inventory) allows us to gain a new understanding of the figure of Ninon. Indeed, our research demonstrates how the courtesan succeeded conciliate transgressions against the established order with an admired and respected “salonnière” reputation.

全球智慧型手機的出貨量持續提升，且熱門市集的App下載次數紛紛突破500億次。而在iOS和Android手機App市集中，App的評價和評論對App在市集的排序有很大的影響；對於App開發者而言，透過評論確實可掌握使用者的需求，並在產生抱怨前能快速反應避免危機。然而，每日多達上百篇的評論，透過人力逐篇查看，不止耗費時間，更無法整合性的瞭解使用者的需求與問題。 文字情感分析通常會使用監督式或非監督式的方法分析文字評論，其中監督式方法被證實透過簡單的文件量化方法就可達到很高的正確率。但監督式方法有無法預期未知趨勢的限制，且需要進行耗費人力的文章類別標注工作。 本研究透過情感傾向和熱門關注議題兩個面向來分析App評論，提出一個混合非監督式與監督式的中文情感分析方法。我們先透過非監督式方法標注評論類別，並作視覺化整理呈現，最後再用監督式方法建立分類模型，並驗證其效果。 在實驗結果中，利用中文詞彙網路所建立的情感詞集，確實可用來判斷評論的正反情緒，唯判斷負面評論效果不佳需作改善。在議題擷取方面，嘗試使用兩種不同分群方法，其中使用NPMI衡量字詞間關係強度，再配合社群網路分析的Concor方法結果有不錯的成效。最後在使用監督式學習的分類結果中，情感傾向的分類正確率達到87%，關注議題的分類正確率達到96%，皆有不錯表現。 本研究利用中文詞彙網路與社會網路分析，來發展一個非監督式的中文類別判斷方法，並建立一個中文情感分析的範例。另外透過建立全面性的視覺化報告來瞭解使用者的正反回饋意見，並可透過分類模型來掌握新評論的內容，以提供App開發者在市場上之競爭智慧。 / While the number of smartphone shipment is continuesly growing, the number of App downloads from the popular app markets has been already over 50 billion. By Apple App Store and Google Play, ratings and reviews play a more important role in influencing app difusion. While app developers can realize users’ needs by app reviews, more than thousands of reviews produced by user everday become difficult to be read and collated. Sentiment Analysis researchs encompass supervised and unsupervised methods for analyzing review text. The supervised learning is proven as a useful method and can reach high accuracy, but there are limits where future trend can not be recognized and the labels of individual classes must be made manually. We concentrate on two issues, viz Sentiment Orientation and Popular Topic, to propose a Chinese Sentiment Analysis method which combines supervised and unsupervised learning. At First, we use unsupervised learning to label every review articles and produce visualized reports. Secondly, we employee supervised learning to build classification model and verify the result. In the experiment, the Chinese WordNet is used to build sentiment lexicon to determin review’s sentiment orientation, but the result shows it is weak to find out negative review opinions. In the Topic Extraction phase, we apply two clustering methods to extract Popular Topic classes and its result is excellent by using of NPMI Model with Social Network Analysis Method i.e. Concor. In the supervised learning phase, the accuracy of Sentiment Orientation class is 87% and the accuracy of Popular Topic class is 96%. In this research, we conduct an exemplification of the unsupervised method by means of Chinese WorkNet and Social Network Analysis to determin the review classes. Also, we build a comprehensive visualized report to realize users’ feedbacks and utilize classification to explore new comments. Last but not least, with Chinese Sentiment Analysis of this research, and the competitive intelligence in App market can be provided to the App develops.

This dissertation, Hugh MacDiarmid and Sorley MacLean: Modern Makars, Men of Letters, transcribes and annotates 76 letters (65 hitherto unpublished), between MacDiarmid and MacLean. Four additional letters written by MacDiarmid’s second wife, Valda Grieve, to Sorley MacLean have also been included as they shed further light on the relationship which evolved between the two poets over the course of almost fifty years of friendship. These letters from Valda were archived with the unpublished correspondence from MacDiarmid which the Gaelic poet preserved. The critical introduction to the letters examines the significance of these poets’ literary collaboration in relation to the Scottish Renaissance and the Gaelic Literary Revival in Scotland, both movements following Ezra Pound’s Modernist maxim, “Make it new.” The first chapter, “Forging a Friendship”, situates the development of the men’s relationship in terms of each writer’s literary career, MacDiarmid already having achieved fame through his early lyrics and with the 1926 publication of A Drunk Man Looks at the Thistle when they first met. MacLean, on the other hand, was a recent university graduate, young teacher, and fledgling poet when he began to provide translations of eighteenth-, nineteenth-, and twentieth-century Gaelic poetry for MacDiarmid to versify in English with the odd Scots or Gaelic word. This assistance was essential to MacDiarmid’s compilation of The Golden Treasury of Scottish Poetry, which he wished to be representative of Scotland’s literary traditions in Scots, Gaelic, English, and Latin. The work resulting from MacDiarmid and MacLean’s literary collaboration further reinforced MacDiarmid’s credibility as a nationalist poet well versed in each of these traditions. Chapter two, “Cultural Nationalism – Politics and Poetry” discusses the significance of each writer’s stance on language in relation to Scottish literature and explores their success in avoiding the ideological antagonisms which plagued the literary and language revivals in early twentieth-century Ireland. “Modern Makars” scrutinizes MacDiarmid and MacLean’s renderings of several Gaelic poems in The Golden Treasury, particularly in relation to the implications of the term “translations”. The final chapter, “Epistolary Discourse and the Legacy of the Letters” sums up the significance of MacDiarmid and MacLean’s collaboration and long-standing friendship, as revealed through their letters, and addresses these writers’ subsequent influence on both writing and cultural life in Scotland. The letters are followed by two appendices. Appendix A includes a transcription of Michael Davitt’s interview with Sorley MacLean for the Irish journal Innti in 1986 wherein MacLean discusses such issues as his political views, the influences on his poetry, and his relationship with MacDiarmid. The interview is provided in its original Irish text and accompanied by a translation into English. Appendix B is a transcription of the Times Literary Supplement’s 4 January 1936 review of MacDiarmid’s translation of The Birlinn of Clanranald as it was originally published in The Modern Scot. Sorley MacLean served as the ghost writer of MacDiarmid’s response to this critique of his work. This research, conducted both here in Victoria and in Edinburgh, Scotland, provides the first book-length study of the literary collaboration of these influential Scottish poets and the first critical discussion of their collected letters.

Image registration is a fundamental problem that can be found in a diverse range of fields within the research community. It is used in areas such as engineering, science, medicine, robotics, computer vision and image processing, which often require the process of developing a spatial mapping between sets of data. Registration plays a crucial role in the medical imaging field where continual advances in imaging modalities, including MRI, CT and PET, allow the generation of 3D images that explicitly outline detailed in vivo information of not only human anatomy, but also human function. Mutual Information (MI) is a popular entropy-based similarity measure which has found use in a large number of image registration applications. Stemming from information theory, this measure generally outperforms most other intensity-based measures in multimodal applications as it does not assume the existence of any specific relationship between image intensities. It only assumes a statistical dependence. The basic concept behind any approach using MI is to find a transformation, which when applied to an image, will maximise the MI between two images. This thesis presents research using MI in three major topics encompassed by the computer vision and medical imaging field: rigid image registration, stereo vision, and non-rigid image registration. In the rigid domain, a novel gradient-based registration algorithm (MIGH) is proposed that uses Parzen windows to estimate image density functions and Gauss-Hermite quadrature to estimate the image entropies. The use of this quadrature technique provides an effective and efficient way of estimating entropy while bypassing the need to draw a second sample of image intensities (a procedure required in previous Parzen-based MI registration approaches). It is possible to achieve identical results with the MIGH algorithm when compared to current state of the art MI-based techniques. These results are achieved using half the previously required sample sizes, thus doubling the statistical power of the registration algorithm. Furthermore, the MIGH technique improves algorithm complexity by up to an order of N, where N represents the number of samples extracted from the images. In stereo vision, a popular passive method of depth perception, new extensions have been pro- posed in order to increase the robustness of MI-based stereo matching algorithms. Firstly, prior probabilities are incorporated into the MI measure to considerably increase the statistical power of the matching windows. The statistical power, directly related to the number of samples, can become too low when small matching windows are utilised. These priors, which are calculated from the global joint histogram, are tuned to a two level hierarchical approach. A 2D match surface, in which the match score is computed for every possible combination of template and matching windows, is also utilised to enforce left-right consistency and uniqueness constraints. These additions to MI-based stereo matching significantly enhance the algorithms ability to detect correct matches while decreasing computation time and improving the accuracy, particularly when matching across multi-spectra stereo pairs. MI has also recently found use in the non-rigid domain due to a need to compute multimodal non-rigid transformations. The viscous fluid algorithm is perhaps the best method for re- covering large local mis-registrations between two images. However, this model can only be used on images from the same modality as it assumes similar intensity values between images. Consequently, a hybrid MI-Fluid algorithm is proposed to compute a multimodal non-rigid registration technique. MI is incorporated via the use of a block matching procedure to generate a sparse deformation field which drives the viscous fluid algorithm, This algorithm is also compared to two other popular local registration techniques, namely Gaussian convolution and the thin-plate spline warp, and is shown to produce comparable results. An improved block matching procedure is also proposed whereby a Reversible Jump Markov Chain Monte Carlo (RJMCMC) sampler is used to optimally locate grid points of interest. These grid points have a larger concentration in regions of high information and a lower concentration in regions of small information. Previous methods utilise only a uniform distribution of grid points throughout the image.

This dissertation, Hugh MacDiarmid and Sorley MacLean: Modern Makars, Men of Letters, transcribes and annotates 76 letters (65 hitherto unpublished), between MacDiarmid and MacLean. Four additional letters written by MacDiarmid’s second wife, Valda Grieve, to Sorley MacLean have also been included as they shed further light on the relationship which evolved between the two poets over the course of almost fifty years of friendship. These letters from Valda were archived with the unpublished correspondence from MacDiarmid which the Gaelic poet preserved. The critical introduction to the letters examines the significance of these poets’ literary collaboration in relation to the Scottish Renaissance and the Gaelic Literary Revival in Scotland, both movements following Ezra Pound’s Modernist maxim, “Make it new.” The first chapter, “Forging a Friendship”, situates the development of the men’s relationship in terms of each writer’s literary career, MacDiarmid already having achieved fame through his early lyrics and with the 1926 publication of A Drunk Man Looks at the Thistle when they first met. MacLean, on the other hand, was a recent university graduate, young teacher, and fledgling poet when he began to provide translations of eighteenth-, nineteenth-, and twentieth-century Gaelic poetry for MacDiarmid to versify in English with the odd Scots or Gaelic word. This assistance was essential to MacDiarmid’s compilation of The Golden Treasury of Scottish Poetry, which he wished to be representative of Scotland’s literary traditions in Scots, Gaelic, English, and Latin. The work resulting from MacDiarmid and MacLean’s literary collaboration further reinforced MacDiarmid’s credibility as a nationalist poet well versed in each of these traditions. Chapter two, “Cultural Nationalism – Politics and Poetry” discusses the significance of each writer’s stance on language in relation to Scottish literature and explores their success in avoiding the ideological antagonisms which plagued the literary and language revivals in early twentieth-century Ireland. “Modern Makars” scrutinizes MacDiarmid and MacLean’s renderings of several Gaelic poems in The Golden Treasury, particularly in relation to the implications of the term “translations”. The final chapter, “Epistolary Discourse and the Legacy of the Letters” sums up the significance of MacDiarmid and MacLean’s collaboration and long-standing friendship, as revealed through their letters, and addresses these writers’ subsequent influence on both writing and cultural life in Scotland. The letters are followed by two appendices. Appendix A includes a transcription of Michael Davitt’s interview with Sorley MacLean for the Irish journal Innti in 1986 wherein MacLean discusses such issues as his political views, the influences on his poetry, and his relationship with MacDiarmid. The interview is provided in its original Irish text and accompanied by a translation into English. Appendix B is a transcription of the Times Literary Supplement’s 4 January 1936 review of MacDiarmid’s translation of The Birlinn of Clanranald as it was originally published in The Modern Scot. Sorley MacLean served as the ghost writer of MacDiarmid’s response to this critique of his work. This research, conducted both here in Victoria and in Edinburgh, Scotland, provides the first book-length study of the literary collaboration of these influential Scottish poets and the first critical discussion of their collected letters.

Στη γραμμική εκδοχή της γενικής θεωρίας της σχετικότητας, θεωρεί κανείς τις διαταραχές κάποιας μετρικής γύρω από κάποιο χωροχρονικό υπόβαθρο. Κρατώντας όρους διαταραχών μέχρι και πρώτης τάξεως, οδηγείται κανείς στις γραμμικές εξισώσεις Einstein. Σε αυτό το πλαίσιο αποδεικνύεται μια σχέση δυισμού ανάμεσα στα διάφορα στοιχεία του τανυστή Weyl, αντίστοιχη με το δυισμό ανάμεσα στην ηλεκτρική και τη μαγνητική ροή της ηλεκτρομαγνητικής θεωρίας του Maxwell. Στην εργασία αυτή κάνουμε μία ανασκόπηση της έρευνας που έχει γίνει μέχρι τώρα αναφορικά με αυτές τις σχέσεις δυισμού. Πιο συγκεκριμένα, εξετάζουμε την ισχύ των σχέσεων στον Anti-de Sitter χωρόχρονο και επισημαίνουμε το τρόπο με τον οποίο κατασκευάζει κανείς δυικές δομές από τις εκφράσεις για τις διαταραχές. Επίσης, χρησιμοποιώντας τη τεχνική της ολογραφικής επανακανονικοποίησης, εξετάζουμε το σύμμορφο σύνορο του χωροχρόνου. Βρίσκουμε εκεί μια σχέση δυισμού ανάμεσα στα στοιχεία του τανυστή ενέργειας-ορμής και του τανυστή Cotton της αντίστοιχης Chern - Simons θεωρίας, η οποία αποδεικνύεται ότι είναι άμεση συνέπεια του δυισμού στο AdS υπόβαθρο. Τέλος, εφαρμόζουμε την ίδια συλλογιστική στο Schwarzschild - Anti-de Sitter υπόβαθρο, όπου η παρουσία της μελανής οπής διαφοροποιεί τις συνοριακές συνθήκες του προβλήματος. Λόγω αυτού του γεγονός δεν μπορεί να πει κανείς με σιγουριά εάν μπορούν να διατυπωθούν σχέσεις δυισμού σε αυτή τη περίπτωση. Παρόλα αυτά βρίσκουμε ότι ισχύουν σχέσεις δυισμού στο σύμμορφο σύνορο παρόμοιες με αυτές του AdS υποβάθρου, πράγμα που σημαίνει ότι στο σύστημα παραμένει κάποια συμμετρία από τη γραμμική θεωρία. Η εργασία καταλήγει σε σχόλια και μία εκτενή συζήτηση για τις πιθανές μελλοντικές κατευθύνσεις. / In the linear version of the general theory of relativity, one considers metric perturbations around a fixed background. Keeping terms up to first order of perturbation leads to the linearized Einstein equations. In this framework it has been proved that a duality between the various elements of the Weyl tensor holds. This duality is similar to the one between the electric and magnetic fluxes of Maxwell's electromagnetism. In the present work we review the status of these dualities for non trivial backgrounds. We examine the Anti-de Sitter background, where we point out the way to explicitly construct dual configurations using the metric perturbation expressions. Using the holographic renormalization technique, we examine the conformal boundary where a duality between the components of the energy-momentum tensor and the Cotton tensor of the corresponding Chern - Simons theory holds. It is then proved that this duality is a direct consequence of the electric/magnetic duality in the bulk, in the case of the AdS background. Finally, we apply same procedure to the Schwarzschild - Anti-de Sitter background, where the presence of the black hole changes the boundary conditions of the problem. This simple fact makes it impossible say whether such a duality exists in this case. Nevertheless, we find that a duality similar to that of the AdS background still holds for the conformal boundary, which means that there is a remnant of symmetry from the linear theory. We conclude with comments and a extensive discussion on possible future directions.

Η αυτόματη ταυτοποίηση εικόνων δακτυλικών αποτυπωμάτων αποτελεί ένα δύσκολο και πολυδιάστατο πρόβλημα, το οποίο έχει απασχολήσει πλήθος ερευνητών και για το οποίο έχει αναπτυχθεί μεγάλος αριθμός τεχνικών. Η δυσκολία του προβλήματος έγκειται στο γεγονός ότι οι εικόνες των αποτυπωμάτων είναι σε μεγάλο ποσοστό αλλοιωμένες ή ακόμα σε κάποιες περιπτώσεις δεν είναι διαθέσιμη η πλήρης εικόνα του αποτυπώματος, αλλά μόνο ένα μέρος αυτής. Στη συγκεκριμένη διατριβή, προτείνονται δύο μέθοδοι αυτόματης ταυτοποίησης δακτυλικών αποτυπωμάτων: α) η μέθοδος ταυτοποίησης δακτυλικών αποτυπωμάτων με χρήση τεχνικών ευθυγράμμισης και β) μέθοδος ταυτοποίησης δακτυλικών αποτυπωμάτων από το συνδυασμό του Δικτύου Αυτό-Οργανούμενων Δικτύων του Kohonen και του ορισμού των σημείων μικρολεπτομερειών των αποτυπωμάτων ως νευρώνων του δικτύου. Επιπλέον, ιδιαίτερη βαρύτητα δόθηκε στην προεπεξεργασία των εικόνων των δακτυλικών αποτυπωμάτων βάσει της ανάπτυξης και εφαρμογής κατάλληλων τεχνικών επεξεργασίας εικόνων προκειμένου να προκύψει βελτίωση της ποιότητας της εικόνας του δακτυλικού αποτυπώματος και να εξαχθούν οι μικρολεπτομέρειες που χρησιμοποιούνται για την ταύτιση των δακτυλικών αποτυπωμάτων. Στο πλαίσιο της παρούσας διατριβής, χρησιμοποιήθηκαν δεδομένα δακτυλικών αποτυπωμάτων από τις βάσεις VeriFingerSample_DB της Neurotechnology και η DB3 του διαγωνισμού δακτυλικών αποτυπωμάτων FVC2004. Για την ποσοτική αποτίμηση της απόδοσης των προτεινόμενων μεθόδων χρησιμοποιήθηκε το κριτήριο της Αναλογίας Ίσου Σφάλματος (EqualErrorRate – EER). Σύμφωνα με το κριτήριο αυτό, η μέθοδος ταυτοποίησης δακτυλικών αποτυπωμάτων βάσει του Δικτύου Αυτό-Οργανούμενων Δικτύων παρείχε καλύτερα αποτελέσματα σε σύγκριση με οποιαδήποτε μέθοδο ευθυγράμμισης που εφαρμόστηκε. / Automatic Fingerprint Identification is a difficult and multidimensional problem. For this reason, the number of papers and techniques regarding this issue is numerous. The hardness of the problem lies with the fact that there is a large percentage of corrupted and partial fingerprint images. Throughout this Thesis, two methods were proposed for the Automatic Fingerprint Identification: a) the Automatic Fingerprint Identification based on registration techniques and b) the Automatic Fingerprint Identification based on the theory of Self Organizing Maps of Kohonen, setting the minutiae of the fingerprint images as input neurons of the Map. Furthermore, an important step prior to the application of the proposed automatic fingerprint identification methods is the pre-processing of these images by the development and implementation of a series of image processing techniques in order to enhance the image quality and to extract the minutiae which are then used for the fingerprint identification. In this Thesis, a substantial number of fingerprint images were used from the database VeriFingerSample_DB kai from the database DB3 of the competition FVC2004. The quantitative evaluation of both proposed automatic fingerprint identification methods were based on the Equal Error Rate (EER) criterion. According to this, the Automatic Fingerprint Identification based on the Self Organizing Maps outperformed against any other method based on registration techniques.

Σκοπός της παρούσας διδακτορικής διατριβής είναι η ανάπτυξη αλγορίθμων επεξεργασίας ιατρικής εικόνας για την ενσωμάτωση τους σε ιατρικές εφαρμογές ακτινοθεραπευτικού ενδιαφέροντος. Οι αλγόριθμοι αυτοί στηρίζονται στην αρχή λειτουργίας των χαρτών αυτο-οργάνωσης Kohonen και αξιοποιούν την πληροφορία που περιέχεται σε περιοχές των εικόνων γύρω από σημεία ενδιαφέροντος, ώστε να εντοπίσουν αυτόματα, με ακρίβεια και αξιοπιστία, αντιστοιχίες μεταξύ των εικόνων. Πιο συγκεκριμένα, ένας επαναληπτικός αλγόριθμος προτείνεται για την αυτόματη εύρεση αντίστοιχων σημείων σε ιατρικές εικόνες δύο διαστάσεων. Ο προτεινόμενος αλγόριθμος προϋποθέτει την εύρεση σημείων ενδιαφέροντος μόνο στη μια από τις δύο εικόνες και εντοπίζει τα αντίστοιχα σημεία στη δεύτερη εικόνα μέσα από μια επαναληπτική διαδικασία, η οποία προσομοιάζει τη φάση εκπαίδευσης του νευρωνικού δικτύου. Με βάση τα ζεύγη των αντίστοιχων σημείων, υπολογίζονται στη συνέχεια οι παράμετροι ενός μετασχηματισμού, κατάλληλου για να περιγράψει τη σχέση μεταξύ των δεδομένων εικόνων. Ο αλγόριθμος ευθυγράμμισης εφαρμόζεται σε δεδομένες εικόνες ηλεκτρονικής πυλαίας απεικόνισης (Electronic Portal Images), που λαμβάνονται πριν από κάθε συνεδρία της ακτινοθεραπείας, για τον υπολογισμό του σφάλματος τοποθέτησης του ασθενούς. Το ζήτημα της επαλήθευσης της θέσης του ασθενούς στην ακτινοθεραπεία αντιμετωπίζεται επίσης με τη βοήθεια μιας αυτόματης μεθόδου εύρεσης αντίστοιχων σημείων σε τρισδιάστατα δεδομένα, η οποία εφαρμόζεται για την ευθυγράμμιση της αξονικής τομογραφίας του σχεδιασμού της ακτινοθεραπείας και μιας αξονικής τομογραφίας επαλήθευσης, που λαμβάνεται πριν την πρώτη συνεδρία της ακτινοθεραπείας. Ο προτεινόμενος αλγόριθμος εντοπίζει αντίστοιχα σημεία ενδιαφέροντος στις δεδομένες τομογραφικές εικόνες και υπολογίζει τις παραμέτρους ενός μη γραμμικού μετασχηματισμού ευθυγράμμισης. Μετά την ευθυγράμμιση των δύο τομογραφιών, υπολογίζεται η μετατόπιση του ισοκέντρου στην τομογραφία επαλήθευσης σε σχέση με τη θέση του ισοκέντρου που προβλέπεται στην αρχική τομογραφία του σχεδιασμού. Με την ενσωμάτωση αυτής της μεθόδου ευθυγράμμισης στη διαδικασία της ακτινοθεραπείας, ικανοποιούνται δύο ανάγκες της κλινικής πρακτικής. Αφενός, η μετατόπιση του ισοκέντρου, όπως υπολογίζεται από την προτεινόμενη μέθοδο, παρέχει μια αξιόπιστη ένδειξη για τη μετατόπιση του ασθενούς που απαιτείται πριν τη χορήγηση της ακτινοβολίας. Αφετέρου, επιχειρείται η καλύτερη αξιοποίηση των πόρων του τμήματος της ακτινοθεραπείας με τη διαδικασία της εύρεσης του ισοκέντρου της ακτινοθεραπείας να λαμβάνει χώρα στην αίθουσα του αξονικού τομογράφου και να μειώνεται συνεπώς ο χρόνος που απαιτείται για την προετοιμασία του ασθενούς στον γραμμικό επιταχυντή κατά την πρώτη συνεδρία της ακτινοθεραπείας. / Aim of the present thesis is the development of image processing algorithms for radiotherapy applications. These algorithms are based on the principles of Kohonen Self Organizing Maps and exploit the information contained in image regions around distinctive points of interest, in order to determine image correspondences in an automatic, accurate and robust way. In particular, an iterative algorithm is proposed for automatic detection of point correspondences in two-dimensional medical images. The proposed algorithm requires the extraction of interest points only in one image and detects the homologous points in the second image through an iterative procedure, respective to the training phase of a neural network. Subsequently, the parameters of an appropriate registration transformation are computed to describe the mapping between the two images. The computation is based on the detected point correspondence. The proposed registration algorithm is applied to Electronic Portal Images, acquired prior to the radiotherapy treatment delivery, in order to estimate the setup error of the patient. The issue of patient position verification in radiotherapy is also addressed in the present thesis by developing an algorithm for automatic detection of point correspondences in three-dimensional medical data. The algorithm is used to register the CT data of radiotherapy planning to an additional verification CT, acquired prior to the first treatment fraction. The proposed algorithm detects corresponding points in the two CT images and computes the parameters of a non-rigid registration transformation. After the registration of the two CT images, the isocenter displacement of the verification CT is calculated with respect to the ideal isocenter position, defined in the planning CT. By integrating the proposed registration procedure in the clinical practice, two needs are met. Firstly, the isocenter displacement, calculated by the proposed method, provides a reliable indication of the patient shift, needed before the treatment delivery, for optimization of the dose delivery. Secondly, an improvement of the radiotherapy department efficiency is attempted by performing the procedure of isocenter marking in the CT scanner room and, consequently, reducing the time expenditure of the patient in the LINAC during the first radiotherapy fraction.