This thesis presents a three-dimensional computed tomography (3D-CT) analysis of craniofacial morphology and growth changes in Malaysian Malay subjects. A large number of CT scans (n=205) from birth to adulthood were gathered for this purpose. CT scans were obtained using a GE Lightspeed Plus Scanner. Craniofacial morphology has been analysed based on cephalometric landmarks located in three-dimensions, using specially-designed computer software. The main aims were to produce new 3D normative reference data for selected craniofacial variables in Malaysian Malays and to study growth changes in different craniofacial regions. The specific areas of investigation included: 1. Construction of craniofacial growth references (in tabular and graphical formats) for Malaysian Malays; 2. Quantitative analysis of growth changes in the craniofacial complex using linear and angular measurements derived from landmark data; 3. Comparison of craniofacial measurements between males and females to determine the extent of sexual dimorphism; 4. Quantitative analysis of the nature and extent of directional asymmetry of selected craniofacial regions; 5. Comparisons of selected variables with published data from other ethnic groups. Craniofacial morphology and growth changes were analysed using 3D osseous landmarks. A computer program, PERSONA, was used to locate and analyse the three-dimensional cephalometric landmarks. The accuracy of landmark location was assessed using double determinations. Selected measurements were derived from the landmark data to describe the morphology of different craniofacial regions, e.g. facial skeleton, cranial base and cranial vault. Normative reference data for a large number of variables covering the skull, cranial base and face at selected age categories for males and females were constructed. These data were presented in tables and scatter plots of variables against age. From the normative data collected, patterns of growth changes of different craniofacial regions in three-dimensions were also investigated. Generally, each craniofacial region showed a unique growth pattern as observed from differential growth patterns. All measurements showed size increase from infancy to adulthood. Periods of increased size differences were also noted for most variables in all regions that corresponded to the timing of mid- and adolescent growth spurts. These extensive normative reference data, specific for age categories and sexes, provide normal references against which the craniofacial morphology of individuals with craniofacial abnormalities can be compared. Clinical applications of this quantitative approach to the craniofacial skeleton should facilitate the management of craniofacial abnormalities. Following the construction of normative data and description of growth changes for different craniofacial regions, intra-populational differences were studied. This included analysis of sexual dimorphism of the craniofacial structures and an investigation of asymmetry between paired left and right measurements. Sexual dimorphism was observed for linear variables in this study. Differences in size between males and females were not very obvious during infancy as only a few variables showed significant differences. The number of variables that showed sexual dimorphism in size increased from infancy to adulthood. Sexual dimorphism in the craniofacial region was most evident during adulthood with 46% of variables displaying significant differences between the sexes. During infancy, only 3% of the variables showed significant size differences between the sexes, increasing to 7% during childhood. Magnitudes of sexual dimorphism were calculated to highlight the pattern of dimorphism in different craniofacial regions and across different ages. A small degree of directional asymmetry was noted in all of the craniofacial regions investigated. Asymmetry analysis revealed that the cranial base, face and mandible tended to be larger on the right side than the left. Other regions exhibited asymmetry but without any clear trend in direction. Asymmetry percentages were also calculated to enable the patterns and magnitudes of asymmetry in different craniofacial regions to be compared. Generally, the amount of asymmetry exhibited in the craniofacial structures for Malaysian Malays was small. Having established that differences existed within the Malay sample, craniofacial data for Malays were compared with published data for two Caucasian populations. This analysis revealed that differences exist in craniofacial morphology between different ethnic groups. Some of the differences can be discerned from childhood but many variables only display differences during adulthood. Craniofacial structures tended to be smaller in Malays than in Caucasians. The intent of this investigation has been to provide clinicians with normative values of measurements that will be useful in diagnosis, treatment planning and post-operative care of patients with craniofacial abnormalities. Important treatment goals include producing balanced cranial and facial form to approximate that of unaffected people and also improving the quality of life of patients. Therefore, it is important for clinicians to be able to recognise the nature and extent of normal variation in craniofacial structures and also appreciate the growth changes that may occur over time, before investigating these changes in patients with craniofacial abnormalities. Comparisons of measurements of affected patients with well-characterised referent data can facilitate diagnosis and overall patient management. Moreover, quantification based on three-dimensional data provides new insights into craniofacial growth changes and morphology compared with conventional 2D approaches. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1280892 / Thesis (Ph.D.) -- Dental School, 2007.

Thesis (M.C.S.)--Miami University, Dept. of Computer Science and Systems Analysis, 2007. / Title from first page of PDF document. Includes bibliographical references (p. 86-88).

University of Macau / Faculty of Science and Technology / Department of Electromechanical Engineering

Silicon alternatives to quartz crystal based oscillators to electronic system clocking are explored. A study of clocking requirements reveals widely different specifications for different applications. Traditional CMOS oscillator-based solutions are optimized for low-cost fully integrated micro-controller clock applications. The frequency variability of these clock generators is studied and techniques to compensate for this variability are proposed. The efficacy of these techniques in reducing variability is proven theoretically and experimentally. MEMS-resonator based oscillators, due to their exceptional quality factors, are identified as suitable integrated replacements to quartz based oscillators for higher accuracy applications such as data converter clocks. The frequency variation in these oscillators is identified and techniques to minimize the same are proposed and demonstrated. The sources of short-term variation (phase noise) in these oscillators are discussed and an inclusive theory of phase noise is developed. Techniques to improve phase noise are proposed. Findings from this research indicate that MEMS resonator based oscillators, may in future, outperform quartz based solutions in certain applications such as voltage controlled oscillators. The implications of these findings and potential directions for future research are identified.

In this thesis, we propose and evaluate two novel scale-based decomposable representations of shape for the segmentation and morphometric analysis of anatomical structures in medical imaging. We propose two representations that are adapted to a particular class of anatomical structures and allow for a richer shape description and a more fine-grained control over the deformation of models based on these representations, when compared to previous techniques. In the first part of this thesis, we introduce the concept of a scale-space shape filter for implicit shape representations that measures the deviation from a tubular shape in a local neighborhood of points, given a particular scale of analysis. We use these filters for the segmentation of blood vessels, and introduce the notion of segmentation with a soft shape prior, where the segmented model is not globally constrained to a predefined shape space, but is penalized locally if it deviates strongly from a tubular structure. Using this filter, we derive a region-based active contour segmentation algorithm for tubular structures that penalizes leakages. We present results on synthetic and real 2D and 3D datasets. In the second part of this thesis, we present a novel multi-scale parametric shape representation using spherical wavelets. Our proposed shape representation encodes shape variations in a population at various scales to be used as prior in a probabilistic segmentation framework. We derive a probabilistic active surface segmentation algorithm using the multi-scale prior coefficients as parameters for our optimization procedure. One nice benefit of this algorithm is that the optimization method can be applied in a coarse-to-fine manner. We present results on 3D sub-cortical brain structures. We also present a novel method of statistical surface-based morphometry based on the use of non-parametric permutation tests and the spherical wavelet shape representation. As an application, we analyze two sub-cortical brain structures, the caudate nucleus and hippocampus.

Not available / text

Η CT αγγειογραφία εγκεφάλου (CTA) είναι μέθοδος καθιερωμένη για την διερεύνηση και την θεραπεία των ενδοκρανιακών ανευρυσμάτων. Σκοπός της μελέτης μας ήταν η σύγκριση των ευρημάτων της ψηφιακής αγγειογραφίας (DSA) με αυτά της CTA και με τα χειρουργικά ευρήματα σε ασθενείς με οξεία υπαραχνοειδή αιμορραγία, καθώς επίσης και η αξιολόγηση της κλινικής χρησιμότητας της μεθόδου. Κατά την διάρκεια τριών ετών, 82 ασθενείς προσήλθαν με κλινική εικόνα και σημειολογία συμβατή με υπαραχνοειδή αιμορραγία. Η CTA έγινε αμέσως μετά την απλή CT, ενώ η DSA εντός των πρώτων 48 ωρών από την εισαγωγή. Όλα τα ανευρύσματα που ευρέθησαν με τις δύο μεθόδους υπεβλήθησαν σε χειρουργική αποκατάσταση ή ενδαγγειακό εμβολισμό. Σε όσους ασθενείς βρέθηκε αρνητικό αποτέλεσμα και με τις δύο μεθόδους, έγινε επαναληπτική DSA 15 ημέρες μετά το επεισόδιο με σκοπό την επιβεβαίωση της απουσίας ανευρύσματος. Οι CTA εξετάσεις καθώς και οι κλασσικές αγγειογραφίες μελετήθηκαν από μια ομάδα δύο ακτινολόγων για κάθε τεχνική, οι οποίοι έπρεπε να καταγράψουν την ύπαρξη ή μη ανευρύσματος, να περιγράψουν τα χαρακτηριστικά του και να αξιολογήσουν την μέθοδο. Χειρουργική ή και ενδαγγειακή θεραπεία έγινε σε 45 ασθενείς και ανευρέθησαν 53 ανευρύσματα. Χρησιμοποιώντας την CTA, ευρέθησαν 47 ανευρύσματα σε 42 ασθενείς. Η DSA ανίχνευσε 43 ανευρύσματα σε 39 ασθενείς. Η ευαισθησία της CTA για τον εντοπισμό όλων των ανευρυσμάτων με βάση το χειρουργικό/θεραπευτικό αποτέλεσμα ήταν 88,7%, η ειδικότητα 100%, η θετική προβλεπτική αξία (PPV) 100%, η αρνητική προβλεπτική αξία (NPV) 80,7% και η ακρίβεια 92,3%. Αντίστοιχα, η ευαισθησία της DSA ήταν 87,8%, η ειδικότητα 98%, η PPV 97,7%, η NPV 89,1% και η ακρίβεια 92,9%. Όσον αφορά στα ανευρύσματα ≥3 mm, η CTA είχε ευαισθησία που κυμαινόταν μεταξύ 93,3 έως 100%, ίση με αυτή της DSA. Η CTA εμφάνισε τα ίδια ποσοστά ευαισθησίας με αυτά της DSA σε ανευρύσματα ≥3 mm. Εμφάνισε επίσης 100% ποσοστό ανίχνευσης σε ανευρύσματα της πρόσθιας αναστομωτικής και του διχασμού της μέσης εγκεφαλικής αρτηρίας, ενώ μερικές εντοπίσεις όπως η οπίσθια αναστομωτική αρτηρία παραμένουν προβληματικές. 80 Κατά την διάρκεια της παρούσας μελέτης προσπαθήσαμε να δημιουργήσουμε μια τεχνική προσομοίωσης της διεγχειρητικής εικόνας των ραγέντων ενδοκρανιακών ανευρυσμάτων, με τη χρήση volume rendering techniques σε εικόνες που προκύπτουν από CT αγγειογραφία. Η τρισδιάστατη κατασκευή των εικόνων προέκυψε από την συνεργασία μιας ομάδας αποτελούμενης από τέσσερις ακτινολόγους, έναν νευροχειρουργό και έναν ιατρικό φυσικό. Το αποτέλεσμα αυτής της συνεργασίας ήταν η παραγωγή μιας εικόνας οριοθετημένης στο χώρο, με οδηγά σημεία που εύκολα μπορούσαν να αναπαραχθούν κατά την διάρκεια του χειρουργείου. Οι εικόνες χειρουργικής προσομοίωσης ενός ανευρύσματος είναι πιθανώς χρήσιμο εργαλείο για τον προεγχειρητικό σχεδιασμό των ενδοκρανιακών ανευρυσμάτων. / Cerebral CT angiography is an established method applied to both the detection and treatment planning of intracranial aneurysms. The aim of our study was to compare DSA to CTA findings and with the surgical results mainly in patients with acute SAH and to evaluate the clinical usefulness of CTA. During the last three years, 82 consecutive patients were admitted under clinical symptoms and signs suggestive of harbouring an intracranial aneurysm. CT angiography performed immediately afterwards the plain CT, while DSA was performed within the first 48 hours of admission. All aneurysms detected, were confirmed during surgery or endovascular embolization. Repeat DSA was performed in all patients having both the initial CTA and the DSA 15 days after the onset of symptoms negative. CT angiograms and conventional angiographies were studied by a consensus of two radiologists for each technique, who performed aneurysm detection, morphological features characterization and evaluation of the technique. Surgical or/and endovascular treatment was performed in 45 patients and 53 aneurysms were confirmed. Using 3D-CT angiography we detected 47 aneurysms in 42 patients. Conventional angiography depicted 43 aneurysms in 39 patients. The sensitivity of CTA for the detection of all aneurysms versus surgery was 88.7%, the specificity 100%, the positive predictive value (PPV) 100%, the negative predictive value (NPV) 80.7% and the accuracy 92.3%. Consequently, the sensitivity of DSA was 87.8%, the specificity 98%, the PPV 97.7%, the NPV 89.1% and the accuracy 92.9%. Considering the aneurysms ≥ 3 mm, CTA showed a sensitivity ranging from 93.3% to 100%, equal to that of DSA. Cerebral CT angiography has an equal sensitivity to DSA in the detection of intracranial aneurysms greater than 3 mm. It has also 100% detection rate in AcoA and MCA bifurcation aneurysms, while some locations like posterior communicating artery aneurysms remain problematic. The delineating features of each aneurysm are better depicted with CTA due to 3D visualization. The use of Digital Subtraction Angiography as a diagnostic tool can be limited in equivocal cases. A supplement to the above work is our effort to describe a technique for simulating the surgical view of ruptured intracranial aneurysms, using volume 82 rendering techniques in spiral CT angiography data. The 3D rendered images were assessed by a team consisted of four radiologists, one neurosurgeon and one medical physicist. The resultant ‘surgical view’ image was standardized in space using a three-dimensional coordinate system, which allowed for its reproduction in the operating theatre. The surgical views are easily reproducible and αποτελούν a useful tool for the surgical planning of intracranial aneurysms.

Thesis (M.S.)--Florida State University, 2006. / Advisor: Piyush Kumar, Florida State University, College of Arts and Sciences, Dept. of Computer Science. Title and description from dissertation home page (viewed June 7, 2006). Document formatted into pages; contains viii, 45 pages. Includes bibliographical references.

Thesis (MSc (Mathematical Sciences))--Stellenbosch University, 2008. / A novel implementation exploiting modern hardware is explored and found to be a significant improvement over current methods used. A 50 times performance increase in the computation time of DRRs is achieved over the conventional ray casting approach and image registration is performed in under a minute.

Introdução: A amputação transtibial é uma das amputações de membros inferiores mais frequentemente realizada. Objetivo: Este trabalho teve por objetivo comparar, através da análise tridimensional da marcha, as alterações de marcha de pacientes com amputação transtibial, previamente treinados, que utilizavam próteses com encaixe Kondylen Bettung Münster (KBM) e a vácuo. Metodologia: Foram avaliados voluntários com amputação transtibial que utilizavam encaixe KBM ou a vácuo disponibilizados pelos Sistema Único de Saúde (SUS). A amostra final foi de 12 participantes no grupo “KBM” e 5 no grupo “vácuo”. Todos eles passaram por um exame físico, que constou de goniometria, teste de força muscular e coleta de dados antropométricos. Eles também realizaram análise tridimensional (3D) da marcha. Para tal, eles foram paramentados com marcadores reflexivos em pontos anatômicos e os correspondentes da prótese, de acordo com o modelo Helen Hayes e caminharam por uma pista de 10 metros com uma velocidade auto selecionada. O sistema de captura consistiu em 6 câmeras Hawk e software Cortex versão 1.1.4.368, de captura e edição das caminhadas, ambos da Motion Analysis Corporation. A comparação entre os dois grupos foi realizada através da Pontuação do Perfil da Marcha (GPS), das Pontuações das Variáveis da Marcha (GVS) e dos parâmetros de tempo e espaço da marcha. Além disso, foi testada a correlação entre a GPS e as GVS e entre a GPS e os parâmetros de tempo e espaço da marcha. Resultados: Os dois grupos obtiveram velocidade da marcha significativamente menores, período de apoio significativamente maior e o tempo de apoio simples menor que o normal. Nos dois grupos ainda, os valores de GPS e GVS foram maiores que o normal, porém o “KBM” apresentou maiores desvios que o “vácuo”. Os maiores desvios do grupo do encaixe KBM foram nas GVS flexão/extensão dos quadris, flexão/extensão dos joelhos e dorsi/plantiflexão do tornozelo MIP, podendo assim caracterizar este como o padrão de desvio do Perfil de Análise do Movimento (MAP) deste grupo. O grupo “vácuo” teve os principais desvios nas GVS dorsi/plantiflexão dos tornozelos, flexão/extensão do joelho MIP e rotação pélvica, sendo este o padrão de desvio do MAP deste grupo. Encontraram-se, portanto, padrões diferentes de desvio nos dois grupos. Os dois grupos apresentaram desvios no MICL, os quais representam as compensações realizadas neste membro para possibilitar uma marcha mais funcional com a prótese. Os participantes que utilizaram o encaixe a vácuo apresentaram marcha mais simétrica que os participantes que utilizavam encaixe KBM. O grupo que utilizava o encaixe a vácuo obteve menores valores de GPS e de algumas GVS que o grupo “KBM”, entre elas estão a flexão/extensão do quadril MIP e MICL, flexão/extensão do joelho MIP e a flexão/extensão do joelho MICL, que foi a única diferença estatisticamente significante entre os grupos de encaixe. O mesmo grupo teve velocidade da macha maior que o grupo “KBM” e, apesar desta diferença não ter sido significativa, sugere uma maior funcionalidade da marcha com o encaixe a vácuo. Conclusão: Pode-se concluir que os indivíduos que utilizaram encaixe a vácuo apresentaram um padrão de marcha mais funcional e com menores desvios que aqueles que utilizaram encaixe KBM, quando comparados através da GPS, das GVS e dos parâmetros de tempo e espaço. / Introduction: Transtibial amputation is one of the lower limb amputations more often performed. Objective: The aim of this study was to compare, using 3D gait analysis, gait deviations of patients with transtibial amputation, previously trained, using KBM and vacum prosthetic fittings. Methodology: Transtibial amputees that used Kondylen Bettung Münster (KBM) and vacuum prosthetic fitting waived by the Sistema Único de Saúde (SUS) were evaluated. The final sample consisted of 12 participants in the "KBM" group and 5 in the "vacuum" group. They all underwent a physical examination, which consisted of goniometry, muscle strength testing and anthropometric data. They also performed three-dimensional (3D) gait analysis. For this, they were vested with reflexive markers on anatomical and prosthetic corresponding landmarkers according to the Helen Hayes and walked across a 10-m walk-way at their self-selected speed. The capture system consisted of 6 cameras Hawk and the Cortex software version 1.1.4.368 for capturing and editing the trials, both from Motion Analysis Corporation. The Gait Profile Scores (GPS), Gait Variable Score (GVS) and temporal-spatial parameters performed the comparison between the two groups. In addition, we tested the correlation between GPS and GVS and between GPS and temporal-spatial parameters. Results: The two groups had significantly lower gait speed, significantly longer period of support and shorter time of single support than normal. In both groups, GPS and GVS values were higher than normal, but the "KBM" showed greater deviations than the "vacuum". The largest deviations from the KBM group was in the GVS hips flexion / extension, knees flexion / extension and ankle dorsi / plantarflexion MIP and can thus characterize this as the deviation pattern of the Movement Analysis Profile (MAP) for this group. The "vacuum" group had major deviations of the GVS ankles dorsi / platarflexion, knee flexion / extension MIP and pelvic rotation, the deviation pattern of MAP in this group. There were, therefore, different deviation patterns I the two groups. Both groups showed deviations in MICL, which represent the compensation made by this limb to enable a more functional gait with prosthesis. Participants who used vacuum prosthetic fitting showed more a symmetrical gait than participants that used KBM prosthetic fitting. The group that used vacuum prosthetic fitting had lower values of GPS and some GVS than "KBM" group; these include hips flexion / extension, MIP knee flexion / extension and MICL knee flexion / extension, which was the only statistically significant difference between the groups. The same group had greater walking speed than the "KBM" group and, although this difference was not significant, it suggests more functionality of gait with vacuum prosthetic fitting. Conclusion: It can be concluded that individuals who used the vacuum prosthetic fitting showed more functional gait pattern and smaller deviations than those that used KBM prosthetic fitting, compared by GPS, GVS and temporal-spatial parameters.