Development and applications of three-dimensional gamma ray tomography system using ray casting volume rendering techniques

Abstract

Computed Tomography (CT) has made possible visualization of physical structures in the interior of an object in their real relative spatial position and orientation. Another important contribution of CT is to greatly improve abilities to distinguish regions with different gamma ray transmittance and to separate over-lying structures. The mathematical problem of CT imaging is that of estimating an image from its projections. In this work, the experimental setup was performed using the Mini Computerized Tomograph of Uniso (MTCU). This tomograph system operates with a gamma ray source of 241 Am (photons of 60 KeV and 100 mCi of intensity) and a NaI(Tl) solid state detector. The system features translation and rotation scanning modes, a 100 mm effective field of view, 1 mm of spatial resolution and 5 % to 10 % of density resolution. The image reconstruction problem can be solved using two different algorithms: Algebraic Reconstruction Techniques (ART) or Discrete Filtered Backprojection (FBP). The three-dimensional image reconstruction method discussed in this work, involves obtaining two-dimensional (2D) gamma ray tomography images and then combining these images into a threedimensional (3D) volume data. An opacity, shading and color is attributed to each volume element (voxel) and the resulting scene is projected in a picture plane to be display in a monitor. Our implementation was developed to be used with MTCU data and was based in the Ray casting volume rendering technique. The use of such technique for nondestructive evaluation is a powerful tool to enable a visual trip inside an object without physically opening or cutting it. Experimental and theoretical methods used are discussed and results of experiments using the 3D reconstruction techniques are presented. A particular use of this technique to study concrete properties, such as stones distributions, visualization of structural occurrences inside concrete samples is discussed.

Representative Gamma-ray Computed Tomography Calibration for Applications in Soil Physics

“…Pires et al [9,10] measured the range of the influence of tensiometer and solution extractor porous cups, its response power, and its operation in soil physical measurements and in another paper presented the use of 2-D tomographic images for the evaluation of the effect of core sampling devices in soil structure. Oliveira et al [11] presented the development and applications of 3-D gamma-ray tomography system using ray casting volume rendering techniques.…”

Caracterizacao De Materiais Usando Dados De Tomografia Computadorizada Por Transmissao De Raios Gama

“…Nesse trabalho, usando dados obtidos pelo Mini Tomógrafo Computadorizado de Raios-Gama, da Universidade de Sorocaba (MTCU), implementamos nova ferramenta, no programa TOMOGRA-FIA TRI-DIMENSIONAL -TTD (OLIVEIRA JR. et al, 2005), permitindo segmentar e classifi car automaticamente elementos, presentes em dados tomográfi cos, como a identifi cação de agregados grossos (britas), presentes no interior das amostras de concreto, permitindo também, calcular os volumes, as áreas de superfície; a posição, etc. Para mostrar as potencialidades da nova ferramenta, foram usadas amostras de concreto e imagens tomográfi cas de um trabalho anterior (OLIVEIRA JR. et al, 2005), desenvolvido por nosso grupo.…”

“…Para mostrar as potencialidades da nova ferramenta, foram usadas amostras de concreto e imagens tomográfi cas de um trabalho anterior (OLIVEIRA JR. et al, 2005), desenvolvido por nosso grupo. A segmentação dos elementos de interesse é obtida, usando-se uma versão modifi cada do programa TTD, que roda, em um computador pessoal (PC), com sistema operacional Windows; sendo que as informações fornecidas pelo programa TTD podem servir como mais um instrumento, para detectar e para quantifi car elementos de interesse, presentes em dados tomográfi cos. Assim, acreditamos que o uso da TC, mais as técnicas de visualização volumétrica, auxiliam a buscar informações precisas, podendo ser utilizadas, como por exemplo, no caso do concreto, para desenvolver novos materiais, baseados em cimento, contribuindo para surgirem técnicas de construção, mais baratas e seguras, tornando o uso do cimento mais racional (WANG de raios-gama até o detector.…”