In current practice, it is common in medical diagnosis or treatment monitoring for a patient to require multiple examinations using different imaging techniques. Magnetic resonance (MR) imaging and computed tomography (CT) are good at providing anatomical information. Three-dimensional functional information about tissues and organs is often obtained with radionuclide imaging modalities: positron emission tomography (PET) and single photon emission tomography (SPET). In nuclear medicine, such techniques must contend with poor spatial resolution, poor counting statistics of functional images and the lack of correspondence between the distribution of the radioactive tracer and anatomical boundaries. Information gained from anatomical and functional images is usually of a complementary nature. Since the patient cannot be relied on to assume exactly the same pose at different times and possibly in different scanners, spatial alignment of images is needed. In this thesis, a general framework for image registration is presented, in which the optimum alignment corresponds to a maximum of a similarity measure. Particular attention is drawn to entropy-based measures, and variance-based measures. These similarity measures include mutual information, normalized mutual information and correlation ratio which are the ones being considered in this study. In multimodality image registration between functional and anatomical images, these measures manifest superior performance compared to feature-based measures. A common characteristic of these measures is the use of the joint-intensity histogram, which is needed to estimate the joint probability and the marginal probability of the images. A novel similarity measure is proposed, the symmetric correlation ratio (SCR), which is a simple extension of the correlation ratio measure. Experiments were performed to study questions pertaining to the optimization of the registration process. For example, do these measures produce similar registration accuracy in the non-brain region as in the brain? Does the performance of SPET-CT registration depend on the choice of the reconstruction method (FBP or OSEM)? The joint-intensity based similarity measures were examined and compared using clinical data with real distortions and digital phantoms with synthetic distortions. In automatic SPET-MR rigid-body registration applied to clinical brain data, a global mean accuracy of 3.9 mm was measured using external fiducial markers. SCR performed better than mutual information when sparse sampling was used to speed up the registration process. Using the Zubal phantom of the thoracic-abdominal region, SPET projections for Methylenediphosponate (MDP) and Gallium-67 (67Ga) studies were simulated for 360 degree data, accounting for noise, attenuation and depth-dependent resolution. Projection data were reconstructed using conventional filtered back projection (FBP) and accelerated maximum likelihood reconstruction based on the use of ordered subsets (OSEM). The results of SPET-CT rigid-body registration of the thoracic-abdominal region revealed that registration accuracy was insensitive to image noise, irrespective of which reconstruction method was used. The registration accuracy, to some extent, depended on which algorithm (OSEM or FBP) was used for SPET reconstruction. It was found that, for roughly noise-equivalent images, OSEM-reconstructed SPET produced better registration than FBP-reconstructed SPET when attenuation compensation (AC) was included but this was less obvious for SPET without AC. The results suggest that OSEM is the preferable SPET reconstruction algorithm, producing more accurate rigidbody image registration when AC is used to remove artifacts due to non-uniform attenuation in the thoracic region. Registration performance deteriorated with decreasing planar projection count. The presence of the body boundary in the SPET image and matching fields of view were shown not to affect the registration performance substantially but pre-processing steps such as CT intensity windowing did improve registration accuracy. Non-rigid registration based on SCR was also investigated. The proposed algorithm for non-rigid registration is based on overlapping image blocks defined on a 3D grid pattern and a multi-level strategy. The transformation vector field, representing image deformation is found by translating each block so as to maximize the local similarity measure. The resulting sparsely sampled vector field is interpolated using a Gaussian function to ensure a locally smooth transformation. Comparisons were performed to test the effectiveness of SCR, MI and NMI in 3D intra- and inter-modality registration. The accuracy of the technique was evaluated on digital phantoms and on patient data. SCR demonstrated a better non-rigid registration than MI when sparse sampling was used for image block matching. For the high-resolution MR-MR image of brain region, the proposed algorithm was successful, placing 92% of image voxels within less than or equal to 2 voxels of the true position. Where one of the images had low resolution (e.g. in CT-SPET, MR-SPET registration), the accuracy and robustness deteriorated profoundly. In the current implementation, a 3D registration process takes about 10 minutes to complete on a stand alone Pentium IV PC with 1.7 GHz CPU and 256 Mbytes random access memory on board.

Object recognition is one of the most important problems in computer vision. Traditional object recognition techniques are usually performed on optical images that are 2D projections of the 3D world. Information about the depth of objects in the scene is not provided explicitly in these images and thus, it makes 2D object recognition techniques sensitive to changes in illumination and shadowing. As surface acquisition methods such as LADAR or range scanners are becoming more popular, there is an increasing interest in the use of three-dimensional geometric data in object recognition to overcome these limitations. However, the matching of 3D free-form surfaces is also a difficult problem due to the shape and topological complexity of 3D surfaces. In addition, the problem is further complicated by other issues such as variations in surface sampling resolution, occlusion, clutter and sensor noise. The huge amount of information required to describe a 3D surface is also another challenge that 3D surface matching techniques have to deal with. This thesis investigates the problems of 3D surface matching that include 3D surface registration and object recognition from range images. It focuses on developing a novel and efficient framework for aligning 3D surfaces in different coordinate systems and from this, recognizing 3D models from scenes with high levels of occlusion and clutter using multi-scale local features. The first part of the thesis presents two different schemes for extracting salient geometric features from 3D surfaces using surface curvature measures known as the curvedness and shape index. By deriving the scale-space representation of the input surface, surface positions with high local curvature or high local shape variations are selected as features at various degrees of scale. One advantage of the proposed approaches is their applicability to both 3D meshes with connectivity information and unstructured point clouds. In the second part of the thesis, an application of the multi-scale feature extraction framework to 3D surface registration and object recognition is proposed. A Delaunay tetrahedrization is performed on the features extracted from each input range image to obtain a set of triangles. Possible correspondences are found by matching all possible pairs of triangles between the scene and model surfaces. From these correspondences, possible transformations between the two surfaces can be hypothesized and tested. In order to increase the accuracy and efficiency of the algorithm, various surface geometric and rigidity constraints are applied to prune unlikely correspondences. By finding the match that aligns the largest number of features between the two surfaces, the best transformation can be estimated. In the case of surface registration, this transformation can be used to coarse-align two different views of the same object. In the case of 3D object recognition, it provides information about the possible pose (location and orientation) of the model in the scene surface. Experimental results on a variety of 3D models and real scenes are shown to verify the effectiveness and robustness of the approach. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1474505 / Thesis (M.App.Sc.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2009

Final Project (M.A.)--John F. Kennedy University, 2003. / "August 25, 2003"--T.p. Includes bibliographical references (p. 104-113).

Thesis (doctoral)--Universität Erlangen.

We formulate and interpret several multi-modal registration methods inthe context of a unified statistical and information theoretic framework. A unified interpretation clarifies the implicit assumptionsof each method yielding a better understanding of their relativestrengths and weaknesses. Additionally, we discuss a generativestatistical model from which we derive a novel analysis tool, the"auto-information function", as a means of assessing and exploiting thecommon spatial dependencies inherent in multi-modal imagery. Weanalytically derive useful properties of the "auto-information" aswell as verify them empirically on multi-modal imagery. Among theuseful aspects of the "auto-information function" is that it canbe computed from imaging modalities independently and it allows one todecompose the search space of registration problems.

Em radioterapia externa, uma nova técnica chamada terapia de radiação de intensidade modulada - IMRT - permite delinear a dose de radiação em imagens de 2 ou 3 dimensões, delimitando de forma bastante precisa e não necessariamente uniforme a região a ser irradiada. Assim, ao mesmo tempo que o tumor é irradiado, é possível evitar a irradiação aos tecidos vizinhos íntegros (sãos), limitando os efeitos secundários do tratamento. Para que a radioterapia externa tenha sucesso usando a técnica IMRT, é fundamental delinear previamente de forma precisa o tumor e os órgãos sãos que devem ser protegidos da radiação, garantindo assim a dose exata de radiação nos volumes alvos. O objetivo desta tese é fornecer ferramentas que sejam adequadas ao delineamento automático de estruturas de interesse e à radioterapia adaptativa para tumores da região da cabeça e do pescoço. Atualmente, a segmentação de estruturas de interesse, tais como os órgãos em risco e as regiões de propagação tumoral, é feita manualmente. Esta é uma tarefa que demanda bastante tempo de um especialista, além de ser tediosa. Além do mais, o planejamento em radioterapia é feito baseado na imagem adquirida na semana do pré-tratamento, onde é calculada a dose. Normalmente o tratamento ocorre em várias semanas, porém a dose estimada no início do tratamento é a mesma para todas as outras semanas do tratamento. Calcular a dose e mantê-la nas demais semanas é uma simplificação que não corresponde à realidade, já que ocorrem mudanças anatômicas no paciente ao longo do tratamento. Estas mudanças ocorrem devido ao encolhimento do tumor e ao possível emagrecimento do paciente, provocando alterações anatômicas locais e globais. As contribuições desta tese visam solucionar e avançar nestes problemas e são apresentadas em dois eixos. No primeiro eixo, é proposta uma metodologia para escolher uma anatomia que seja representativa da população, anatomia esta chamada de atlas. O registro do atlas na imagem do paciente permite que estruturas de interesse sejam segmentadas automaticamente, acelerando o processo de delineamento e tornando-o mais robusto. A segunda contribuição desta tese é voltada à radioterapia adaptativa. Para que a dose estimada na primeira semana seja adaptada às modificações anatômicas, é necessária a utilização de métodos de registro não-rígidos. Portanto, nesta etapa é feita uma avaliação e adaptação dos métodos de registros de forma que a região do tumor esteja bem alinhada. / Intensity Modulated Radiotherapy (IMRT) is a new technique enabling the delineation of the 3D radiation dose. It allows to delineate a radiation zone of almost any shape and to modulate the beam intensity inside the target. If IMRT enables to constrain the radiation plan in the beam delivery as well as in the protection of important functional areas (e.g. spinal cord), it also raises the issues of adequacy and accuracy of the selection and delineation of the target volumes. The purpose of this thesis is to provide tools to automatic delineation of the regions of interest and also to adaptive radiotherapy treatment for tumors located in the head and neck region. The delineation in the patient computed tomography image of the tumor volume and organs to be protected is currently performed by an expert who delineates slice by slice the contours of interest. This task is highly time-consuming and requires experts’ knowledge. Moreover, the planning process in radiotherapy typically involves the acquisition of a unique set of computed tomography images in treatment position on which target volumes (TVs) and normal structures are delineated, and which are used for dose calculation. Restricting the delineation of these regions of interest based solely on pre-treatment images is an oversimplification as it is only a snapshot of the patient´s anatomy at a given time. Shrinkage of the tumor and modification of the patient anatomy at large (e.g. due to weight loss) may indeed occur within the several weeks’ duration of a typical treatment. The main contributions of this thesis aim to advance in the solution to these issues and are presented in two axes. In the first one, it is proposed a methodology to choose an image with the most representative anatomy of a population; such image is called Atlas. The registration of the atlas into a new image of the patient allows to automatically segment the structures of interest, speeding up the delineation process and making it more robust. The second contribution of this thesis is focused on the adaptive radiotherapy. In order to adjust the estimated dose to the anatomical modifications, it is fundamental to have non-rigid registration algorithms. So, the evaluation and adaptation of non-rigid registration methods are required, addressing especially the alignment of the tumor’s region among different moments of the treatment.

No description available.

Em radioterapia externa, uma nova técnica chamada terapia de radiação de intensidade modulada - IMRT - permite delinear a dose de radiação em imagens de 2 ou 3 dimensões, delimitando de forma bastante precisa e não necessariamente uniforme a região a ser irradiada. Assim, ao mesmo tempo que o tumor é irradiado, é possível evitar a irradiação aos tecidos vizinhos íntegros (sãos), limitando os efeitos secundários do tratamento. Para que a radioterapia externa tenha sucesso usando a técnica IMRT, é fundamental delinear previamente de forma precisa o tumor e os órgãos sãos que devem ser protegidos da radiação, garantindo assim a dose exata de radiação nos volumes alvos. O objetivo desta tese é fornecer ferramentas que sejam adequadas ao delineamento automático de estruturas de interesse e à radioterapia adaptativa para tumores da região da cabeça e do pescoço. Atualmente, a segmentação de estruturas de interesse, tais como os órgãos em risco e as regiões de propagação tumoral, é feita manualmente. Esta é uma tarefa que demanda bastante tempo de um especialista, além de ser tediosa. Além do mais, o planejamento em radioterapia é feito baseado na imagem adquirida na semana do pré-tratamento, onde é calculada a dose. Normalmente o tratamento ocorre em várias semanas, porém a dose estimada no início do tratamento é a mesma para todas as outras semanas do tratamento. Calcular a dose e mantê-la nas demais semanas é uma simplificação que não corresponde à realidade, já que ocorrem mudanças anatômicas no paciente ao longo do tratamento. Estas mudanças ocorrem devido ao encolhimento do tumor e ao possível emagrecimento do paciente, provocando alterações anatômicas locais e globais. As contribuições desta tese visam solucionar e avançar nestes problemas e são apresentadas em dois eixos. No primeiro eixo, é proposta uma metodologia para escolher uma anatomia que seja representativa da população, anatomia esta chamada de atlas. O registro do atlas na imagem do paciente permite que estruturas de interesse sejam segmentadas automaticamente, acelerando o processo de delineamento e tornando-o mais robusto. A segunda contribuição desta tese é voltada à radioterapia adaptativa. Para que a dose estimada na primeira semana seja adaptada às modificações anatômicas, é necessária a utilização de métodos de registro não-rígidos. Portanto, nesta etapa é feita uma avaliação e adaptação dos métodos de registros de forma que a região do tumor esteja bem alinhada. / Intensity Modulated Radiotherapy (IMRT) is a new technique enabling the delineation of the 3D radiation dose. It allows to delineate a radiation zone of almost any shape and to modulate the beam intensity inside the target. If IMRT enables to constrain the radiation plan in the beam delivery as well as in the protection of important functional areas (e.g. spinal cord), it also raises the issues of adequacy and accuracy of the selection and delineation of the target volumes. The purpose of this thesis is to provide tools to automatic delineation of the regions of interest and also to adaptive radiotherapy treatment for tumors located in the head and neck region. The delineation in the patient computed tomography image of the tumor volume and organs to be protected is currently performed by an expert who delineates slice by slice the contours of interest. This task is highly time-consuming and requires experts’ knowledge. Moreover, the planning process in radiotherapy typically involves the acquisition of a unique set of computed tomography images in treatment position on which target volumes (TVs) and normal structures are delineated, and which are used for dose calculation. Restricting the delineation of these regions of interest based solely on pre-treatment images is an oversimplification as it is only a snapshot of the patient´s anatomy at a given time. Shrinkage of the tumor and modification of the patient anatomy at large (e.g. due to weight loss) may indeed occur within the several weeks’ duration of a typical treatment. The main contributions of this thesis aim to advance in the solution to these issues and are presented in two axes. In the first one, it is proposed a methodology to choose an image with the most representative anatomy of a population; such image is called Atlas. The registration of the atlas into a new image of the patient allows to automatically segment the structures of interest, speeding up the delineation process and making it more robust. The second contribution of this thesis is focused on the adaptive radiotherapy. In order to adjust the estimated dose to the anatomical modifications, it is fundamental to have non-rigid registration algorithms. So, the evaluation and adaptation of non-rigid registration methods are required, addressing especially the alignment of the tumor’s region among different moments of the treatment.

Made available in DSpace on 2014-06-11T19:22:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-05-27Bitstream added on 2014-06-13T19:48:45Z : No. of bitstreams: 1 lopes_rf_me_prud.pdf: 5197639 bytes, checksum: 1c8da2ba222153e72f0e411a1ff89f69 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A utilização de imagens adquiridas por sensores CCD de médio formato, em plataformas aéreas, é uma alternativa para a redução de custos em projetos de aerolevantamento. Porém, alguns inconvenientes, como a pequena área de cobertura e a limitação às bandas do visível restringem algumas aplicações. Para resolver estes problemas podem ser usados vários sensores CCD simultaneamente, sendo necessária uma etapa posterior de fusão e registro destas imagens. Neste trabalho foram utilizados dois sistemas compostos por múltiplas câmaras, o Sistema de Aquisição e Pós-Processamento de Imagens Tomadas com Câmaras Digitais (SAAPI) e o Sistema de Câmaras Fuji. O sistema SAAPI permite diferentes configurações entre os sensores que o compõem, podendo estar nos modos duplooblíquo ou nadiral à área fotografada. A metodologia desenvolvida no trabalho trata duas questões envolvidas com a configuração de sistemas de múltiplas câmaras: o registro entre imagens IR e RGB e a fusão entre imagens RGB oblíquas, tendo como objetivo o aumento da resolução espectral e geométrica da imagem final produzida. Para isto são utilizados processos como a retificação e reamostragem de imagens. Estes, por sua vez, necessitam dos dados de calibração do sistema de câmaras, pois os parâmetros de orientação interior e exterior (POI e POE) são imprescindíveis para corrigir os efeitos das distorções nas imagens e o efeito da inclinação do sistema de câmaras. Experimentos realizados com imagens áreas, utilizando a metodologia proposta, demonstram que a discrepância nas coordenadas de pontos comuns às imagens registradas foi menor que 1 pixel. Este resultado é dependente da qualidade da calibração do sistema de câmaras / The use of images acquired by medium format CCD sensors from aerial platforms, is a cost effective alternative for aerial surveying projects. However, some drawbacks, as small coverage area and limitation to the visible spectrum bands restrict some applications. To solve these problems multiple CCD sensors can be used simultaneously, requiring a later stage for registration and fusion of these images. In this study, two systems with multiple cameras, the System for Airborne Acquisition and Processing of Digital Images (SAAPI) and Fuji Camera System were used. The SAAPI system allows different configurations between the sensors that can be either double-oblique or nadir to the area photographed. The methodology developed in this study approached two issues involved with systems with multiple cameras: the registration between IR and RGB images and oblique RGB images fusion, aiming at increasing the geometric and spectral resolution of the final image to be produced. There were used processes such as rectification and images resampling. These processes require the previous camera and system calibration, because inner and exterior orientation parameters (IOP and EOP) are essential to correct the effects of distortions in the images and the effect of camera convergence within the system. Experiments performed with real terrestrial and aerial images using the proposed methodology, showed that the discrepancy in the coordinates of common points in the registered images were less than 1 pixel. This result is dependent on the quality of the system and camera calibration

M.Comm. / Stakeholders in the process of transfer of immovable property often argue that transfers take too long. This perception impacts unfavourably on investments in property, as well as on the effective management by conveyancing attorneys of their practices. Different views exist, however, as to how long transfers actually take in practice and as regards the period of time that would constitute a reasonable duration for a typical transfer. The purpose of the study is firstly to establish, by means of empirical research, how long transfers should take, given the factors that influence their duration, and secondly to determine how long transfers actually take in practice. The study identifies the factors that influence the duration of transfers. Based on the observations of practising conveyancers, it then proceeds to establish that typical transfers (transfers resulting from certain defined property transactions) should be registered within 6 to 12 weeks (42 to 84 days) from the date of sale. Some conveyancers prefer to express the duration of transfers in months rather than weeks, and state that two to three months (60 to 90 days) represent a normal spectrum of duration for typical transfers. A model is then developed, based on PERT (Programme Evaluation and Review Techniques), that determines the minimum and maximum duration that could reasonably be expected with regard to typical transfers. These periods are calculated as 35 days and 97 days respectively. A reasonable, "average" period for typical transfers is calculated as 63 days. Based on the above findings, the study recommends a duration of 60 to 70 days as a reasonable time span for typical transfers. This period constitutes a theoretical benchmark against which the duration of typical transfers may be measured. The thesis then proceeds to calculate the real duration of typical transfers, based on information regarding transfers that had actually been registered in South African deeds offices over a period of seven years and ten months. With the aid of electronic data it is calculated that typical transfers take an average of 90.15 days from conclusion of sale to date of registration. The median of duration is determined as 85 days and the mode as 70 days. A ten day incrementalX analysis reflects the ten day category of 61 to 70 days as the category in which the most typical transfers occur. Certain trends regarding the duration of transfers are established. Sectional title transfers are on average registered 1. 7 days faster than freehold transfers. A year-on-year comparison shows a reduction in the figure for average duration of typical transfers during the years 1995 to 1999, but average duration increases substantially in 2000 and 2001. In some deeds registries transfers are on average registered faster than in others, but no relationship is found between the volume of registrations in a particular deeds office and the average duration of these transfers. A relationship is found to exist, however, between the price bracket of a property and the duration of the transfer. Broadly speaking it can be said that the higher the price, the shorter the duration of the transfer. At first glance it appears that, generally speaking, transfers actually take as long -or ·as short- as they are in theory supposed to take. Further analysis show, however, that a mere 35.28% of typical transfers are registered within 70 days or less. Only 54.46% of typical transfers take 90 days or less to register. The fact that so many actual registrations fail to meet the theoretical standards described in the study leads to tre conclusion that the unfavourable perception about the duration of transfers has some merit. The thesis recommends that conveyancers use the findings of the study as management tools in the day to day management of their conveyancing practices. A follow- on study that addresses the unfavourable perception about the duration of transfers in more detail is also recommended.