Basic MicroCT

Computed tomography is a form of 3D X-ray. X-rays are generated by focusing electrons produced in a cathode at a target. The target produces X-rays which are then directed to the sample of interest. X-rays travel through the sample to a detector. Denser samples absorb more X-rays, whereas less dense samples absorb fewer X-rays. For optimal imaging, it is necessary that the object partially absorbs X-rays (some X-rays are absorbed while some pass through) as well as differentially absorbs X-rays (if there are no density differences then the object will show as uniformly grey). The unabsorbed X-rays are recorded by a detector to produce a projection image. The sample is then rotated and another projection image is taken. The process is repeated until the object has rotated either 180° or 360° producing a stack of projection images. The projection images are then transformed using computer algorithms into a series of 2D cross-sectional images. The spatial resolution of the resulting 2D images is dependent on the size of the object under investigation, its distance from the X-ray source, as well as the size of the detector panel.