Dual-Layer Spectral Computed Tomografy: Reduction of metallic artefacts from posterior spinal fusions using virtual monoenergetic imaging

Zielsetzung:

To evaluate the clinical potential of virtual monoenergetic images (monoE) generated with a dual-layer spectral Computed Tomografy (CT) system and determine the optimal settings for reduction of metal artifacts from posterior spinal fusions of diverse extent and different spine levels.

Material und Methodik:

Twenty patients with posterior spinal fusion who underwent a spectral CT scan (IQon Spectral CT, Philips Healthcare, USA) for various clinical indications were included into this study. Two independent readers evaluated axial 0.9 mm slides with a window center of 50 HU and width of 380 HU. Image quality of the conventional scan was compared with monoE images at 40, 60, 80, 100, 120, 140, 160, 180 and 200 keV. A four point Likert-scale was used to document subjective impression of diagnostic image quality and the Hounsfield unit of the area with the most pronounced streak artefact was documented for every keV-setting. Additionally, the optimal monoE (OPTkeV) setting for all patients was determined.

Ergebnisse:

Quantitative and qualitative analysis showed statistically significant artefact reduction for higher monoE levels and especially for the OPTkeV compared to conventional images. Optimal keV-settings ranged from 120 to 140 keV. Our results reveal high inter-reader agreement for quantitative and qualitative evaluations.

Schlussfolgerungen:

Virtual monoenergetic images of higher energy levels (120 – 140 keV) provide significant reduction of metallic artefacts from posterior spinal fusions compared to conventional scans. Compared to previous results, with dual-layer spectral CT our findings can be applied to the whole field-of-view and to all patients without any compromises.