Quality Improvements for Cone-Beam CT Using Beam Hardening and Scattering Correction

S Kasperl, M Franz, Dr R Hanke, Dr U Hassler, S Schröpfer

FhG, Am Weichselgarten 34, 91058 Erlangen Germany, ksp@iis.fhg.de

ABSTRACT

The non-destructive inspection of castings for process optimisation is an important task in the foundry industry. The requirements contain a fast verification of dimensional accuracy and the analysis of the deviation of the real geometry from target data. The most adequate NDT method for this purpose is 3D CT.

In first order, the x-ray beam attenuation follows an exponential law, i.e. ideal linear run of the attenuation characteristics. Real system characteristics have non-linear dependencies caused by effects like beam hardening, Compton scattering and non-linearity of the detector. These effects are reflected as artefacts in the reconstructed slices and reduce the image quality vastly.

We present a multistage process, called Iterative Artefact Reduction (IAR) to correct beam hardening and Compton scattering. The method is based on 3D image processing steps and is independent of any reference object.

Keywords X-ray, cone-beam CT, beam hardening, scattering