Basic principles of computed tomography (CT)

The CT process involves several steps:

  1. Scanning
  2. Reconstruction
  3. Visualisation
  4. Data collection

Micro- and nano-CT scanners produce 2D representations of a slice of an object based on material density, measured by X-ray transmissions

The resulting slice is made up of 3D pixels, known as ‘voxels’. Each voxel is assigned a CT (grey) value derived from a linear attenuation coefficient that relates to the density of the materials being scanned.

Since a CT scan is a mathematical representation of an object rather than a true image, it is suited to quantitative analysis of structure and geometry.

Scan resolution

The resolution of a scan is largely determined by the size of the voxels. It is in the order of:

  • 3-125μm for micro-CT
  • 0.2-2μm for nano-CT