Modelling and Correction of Scatter in a Switched Source Multi-Ring Detector X-ray CT machine

  • Nicola Wadeson

Student thesis: Phd


The RTT80 cone beam x-ray computed tomography system, developed by Rapiscan Systems Ltd, uses switched x-ray sources and fixed offset detector rings to remove the time consuming mechanical rotations of earlier imaging systems. This system produces three-dimensional images in real time. A Geant4 Monte Carlo simulation has been developed to investigate scattered radiation in the uncollimated detector machine, showing high levels of scatter behind highly attenuating objects.A new scatter correction method is proposed which estimates scatter to each detector, in each projection, from 1cm$^{3}$ voxels of the computerised object. The scatter distributions from different materials are pre-determined using a Geant4 Monte Carlo simulation. The intensity of scatter from each voxel is based on measured data. The method is applied to two simulated test objects, a water box simulated with a monoenergetic input spectrum and a test suitcase simulated with a polyenergetic spectrum. The test suitcase is broken down into separate components to analyse the method further. The results show that the method performs well for low attenuating objects, but the results are sensitive to the intensity values. However, the method provides a good basis for a scatter correction method.
Date of Award1 Aug 2011
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorWilliam Lionheart (Supervisor)


  • Scatter correction
  • Geant4
  • Monte Carlo
  • RTT
  • X-ray cone beam CT

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