Evaluation of metal artefacts reduction by application of monoenergetic extrapolation of dual-energy CT: A phantom study with different metal implants

The aim of this study was to evaluate the application of monoenergetic (ME) extrapolation technique of dual-energy computed tomography (DECT) for metal artefact reduction using phantom study. This study involved phantom study with a customized phantom consisting different types of metal implant such as titanium and stainless steel. The phantom was scanned using a single-source DECT scanner (SOMATOM Definition AS+, Siemens Healthcare, Germany) with dual-energy mode of 140/80 kV spectrum. The commercially available post-processing software (Syngo DE, Siemens) was applied to generate ME image datasets with different extrapolated energies ranged from 55 to 160 keV. The reduction of artefacts was measured qualitatively and quantitatively using region of interests (ROIs) statistical analysis. The results show 60% of metal streak regions were reduced significantly at higher extrapolated energy which is 160 keV. Quantitative analysis also resulted in lower HU readings within the region of artefact for 160 keV. However, higher extrapolated energy resulted in higher noise and lower signal-to-noise (SNR) value. ME images at 160 keV appear noisier while ME images at 64, 70 and 80 keV appear smoother. Metal artefacts induced by both metal implants were reduced significantly using DECT ME extrapolation and diagnostic quality of CT images also improved. It can be achieved by using higher ME of DECT. However, image noise is higher, and SNR is reduced with higher ME extrapolated energy.