Cone beam reconstruction

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For microtomography,x-ray scanners typically use 2 methods for scanning:

  • Fan beam reconstruction
  • Cone beam reconstruction.
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Cone beam set-up
Cone beam set-up

Cone beam reconstruction uses a 2 Dimensional approach of using a normal black and white camera that is coated with a scintillator which converts x-rays to visible light. An x-ray source, normally electronic generated, is sending x-rays towards a target sample which creates shadow images on the scintillator. Depending on the scanner type, either the target sample is rotated or the camera – (x-rays) source systems is rotated.

Close-up to show the shadow image
Close-up to show the shadow image

The reason why it is called cone-beam reconstruction is that the x-rays are sent in a cone shape. The images taken are called projection images or are also known as shadow images. The more x-rays-dense the object is the less x-rays will hit the scintillator and the less light it produces. So the camera sees a dark point. This way we know the density of this object according to this line of sight from the projected point towards the x-rays source point.

By taking multiple projection images around the rotation axis of the sample, we can reconstruct the cross section of that object. Unlike Fan Beam reconstruction, we have a lot of mathematics to reconstruct one cross-section so we need a lot of processing power of the computer(s) that does this.

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