3D surface reconstruction for lower limb prosthetic model using modified radon transform

Computer vision has received increased attention for the research and innovation on three-dimensional surface reconstruction with aim to obtain accurate results. Although many researchers have come up with various novel solutions and feasibility of the findings, most require the use of sophisticated devices which is computationally expensive. Thus, a proper countermeasure is needed to resolve the reconstruction constraints and create an algorithm that is able to do considerably fast reconstruction by giving attention to devices equipped with appropriate specification, performance and practical affordability. This thesis describes the idea to realize three-dimensional surface of the residual limb models by adopting the technique of tomographic imaging coupled with the strategy based on multiple-views from a digital camera and a turntable. The surface of an object is reconstructed from uncalibrated two-dimensional image sequences of thirty-six different projections with the aid of Radon transform algorithm and shape-from-silhouette. The results show that the main objective to reconstruct three-dimensional surface of lower limb model has been successfully achieved with reasonable accuracy as the starting point to reconstruct three-dimensional surface and extract digital reading of an amputated lower limb model where the maximum percent error obtained from the computation is approximately 3.3 % for the height whilst 7.4%, 7.9% and 8.1% for the diameters at three specific heights of the objects. It can be concluded that the reconstruction of three-dimensional surface for the developed method is particularly dependent to the effects the silhouette generated where high contrast two-dimensional images contribute to higher accuracy of the silhouette extraction. The advantage of the concept presented in this thesis is that it can be done with simple experimental setup and the reconstruction of three-dimensional model neither involves expensive equipment nor require any service by an expert to handle sophisticated mechanical scanning system

Usinagem de próteses para cranioplastia a partir de imagens tomográficas

Orientador: Dalberto Dias da CostaDissertação (mestrado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduação em Engenharia Mecânica. Defesa: Curitiba, 2004Inclui bibliografiaResumo: A fabricação de próteses para substituição de tecidos duros (ossos) tem sido um tema recorrente em diversos trabalhos científicos na área de bioengenharia. Recentemente, com o avanço das técnicas de digitalização e processamento de imagens, vários pesquisadores vêm defendendo o implante de próteses pré-fabricadas como uma alternativa para redução do tempo de cirurgia, da morbidade, da dor pós-operatória, do risco de infecções e rejeições, além de apresentar melhores resultados estéticos. Dentre as alternativas para a fabricação de próteses sob medida, destaca-se o uso das tecnologias CAD (Computer-Aided Design), CAM (Computer-Aided Manufacturing) e CNC (Comando Numérico Computadorizado). Entretanto, existem ainda alguns obstáculos, no que se refere à integração da informação (imagens) obtida por tomografia aos sistemas CAD/CAM/CNC comerciais. O objetivo deste trabalho é apresentar e discutir duas diferentes abordagens para essa integração e mostrar os resultados da fabricação, por usinagem, de uma prótese para fins médicos. Várias imagens tomográficas de um crânio humano seco foram utilizadas como fonte primária de informação. Utilizando-se tanto softwares dedicados ao processamento de informações médicas como os de uso geral, para conversão e vetorização de imagens, foi reconstruída uma região de interesse do crânio digitalizado. Essa região modelada foi avaliada e depois convertida em um formato apropriado aos sistemas CAM’s, os quais permitiram a simulação e geração de um programa CN para a usinagem de uma possível prótese dessa região. Esta prótese foi fresada em acrílico e depois inspecionada visual e dimensionalmente. A principal conclusão deste trabalho é que a usinagem direta propicia excelentes resultados estéticos enquanto alternativa para a fabricação de implantes para cranioplastia. Palavras-chave: usinagem; superfícies complexas; imagens tomográficas; próteses sob medida; cranioplastia.ABSTRACT The use of prosthesis, for replacement of hard tissues (bones), has been a recurrent subject in a huge variety of scientific works in the field of bioengineering. Lately, with the advancement in digitalizing and image processing, researchers have pointed out the application of pre-fabricated implants as an alternative way for reduction of the time, morbidity, postsurgery pain, the risk of infections and rejections, besides presenting better aesthetic results. Among the alternatives for tailored prosthesis, the technologies CAD (Computer-Aided Design), CAM (Computer-Aided Manufacturing) and CNC (Computerized Numeric Control) are mandatory. However, there are still some difficulties concerning the integration of the information acquired from CT images to the commercial CAD/CAM/CNC systems. The purpose of this research is to present and discuss two differents methodologies for this integration and show the machining results of a milled PMMA prosthesis. Several CT images of a dry human skull were taken as primary source of information. Specialized medical softwares and general purpose systems, for image processing, were evaluated as a two methods for vetorizing and 3D reconstruction of a separated region from the CT images. The modeled region was evaluated and converted to readable CAM formats for machining simulation and NC code generation for a similar prosthesis. An acrilic blank was milled according to planed prosthesis and visualy inspected and measured. The main conclusion of this work is concerned to the good aesthetic results obtained by direct machining for cranioplasty. Keywords: Milling; sculptured surfaces; CT images; individual implants; cranioplasty