The use of 2D pixel detectors in micro- and nano-CT applications
Computed Tomography or CT is a non-destructive imaging technique that uses penetrating radiation (mostly X-rays) to visualize the internal structure of a sample. The best known example is the CAT scanner which has become a standard diagnostic tool in medical science, providing detailed views of the body with spatial resolutions below one millimeter. In recent years another type of CT scanners has been developed for mostly industrial and scientific applications, namely micro-CT scanners. These made spatial resolutions possible of the order of tens of microns to even a few microns.
During 2005 the Radiation Physics research group (Dept. of Subatomic and radiation physics) and the Sedimentary Geology and Engineering Geology research group (Department of Geology and soil science) of the Ghent University jointly developed a modular micro-CT setup. The two main goals were to achieve a spatial resolution of below one micrometer and to have a very versatile tool providing high-quality images. We opted for a so-called dual-head X-ray tube with 1) a transmission type head with a nominal focal spot size of 900 nm below 40 kV tube voltage for high resolution applications and 2) a directional high power head (up to 160 keV, up to 150 Watts) which enables us to scan larger samples. A six-axis sample manipulator system was assembled. The crucial component in this is an ultra high precision air-bearing rotation stage to keep all motion errors during rotation well below 1 micrometer.
Depending on the application we have the choice between a number of detectors, each with their own advantages in terms of size, pixel resolution, energy sensitivity, dynamic range, noise etc. Different detector technologies are available including an amorphous silicon flat panel, a 11 Megapixel CCD camera, CMOS flat panel detectors and an image intensifier. All this results in a wide range of experimental conditions (10-160 kV, sample size from sub-mm up to 20 cm, spatial resolutions from 1 mm down to 1 micrometer). Some applications are: species description of fossil inclusions in amber, statistical analysis of pore size distributions in rocks and soils, providing 3D CAD models of objects for input into finite element tools for simulation of stress or fluid flow, structural analysis of foams etc.
This talk will give a detailed description of the setup, an overview of some typical applications and the available hard- and software-tools. Finally we will describe the potential of future detector technologies in micro-CT applications.
