Image quality improvements in high energy CT applications using the IAR method

Böhnel, Michael; Fraunhofer EZRT; Germany

Böhnel, M.; Fraunhofer Institute for Integrated Circuits IIS; Germany
Reims, N.; Fraunhofer Institute for Integrated Circuits IIS; Germany
Kasperl, S.; Fraunhofer Institute for Integrated Circuits IIS; Germany
Salamon, M.; Fraunhofer Institute for Integrated Circuits IIS; Germany

ID: ECNDT-0362-2018
Download: PDF
Session: CT-Methods 2
Room: G3
Date: 2018-06-12
Time: 13:50 - 14:10

In the field of non-destructive testing (NDT) computed tomography (CT) based on conventional X-ray tubes is widely used. Nevertheless, the increasing demand in scanning of larger volume parts or specimen with high density materials requires the use of high energy X-ray sources in the MeV regime, e.g. linear accelerators, to cope with the requirements of higher penetration capabilities.

Commonly high energy CT systems are using line detector arrays (LDA) as preferred detector systems. These LDAs provide a high detection efficiency as well as the possibility to strongly collimate the sensor system to reduce the negative effects on image quality caused by the greater amount of scattered radiation produced in the specimen compared to conventional X-ray tube energies.
In contradiction to LDAs common 2D flat panel detector arrays (FPA) provide much higher scanning speeds but lack of the possibility to collimate against scattered radiation.
To benefit from the higher scanning speed but to obtain better image quality in FPA measurements, there exist some methods for scatter correction. These methods are mostly based on deconvolution approaches that require additional measurement efforts with beam stop arrays, reference objects or collimation stages to acquire correction data for the post processing; hence the overall mechanical efforts and the measurement time is negatively affected.

Our approach at the high energy facility of the Fraunhofer EZRT regarding image quality improvement of FPA CT measurements is to apply the Iterative Artefact Reduction (IAR) method. The IAR is basically a signal linearization approach mainly intended to deal with the reduction of beam hardening artefacts – that might as well occur in high energy applications with high density objects – but also has shown a positive side effect on the reduction of scatter artefacts in high energy applications. The IAR works on the originally acquired CT projections and no further data or prior knowledge is needed. In our contribution we will present results of the IAR method in high energy FPA CT applications.