Fast scanning in chest CT: Investigating clinical and technical image quality features

The main objective of this study was to investigate how ultra-fast CT scanning influences cardiac pulsation artefacts and image quality in low dose chest CT, clinically and in a non-moving 3D resolution phantom.

30 patients underwent two non-contrast chest CT examinations within 6 months using one ultra-fast and one standard speed protocol. Three radiologists scored general image quality and motion artefacts (ascending aorta, superior aortic recess, left ventricle, lung tissue) using a 4-point Likert scale. Lung parenchyma, pulmonary fissures, segmental bronchi, pleuromediastinal border, carina and pulmonary vessels were compared between ultra-fast and standard speed scans. Volumetric resolution was measured with an image quality phantom containing a 3D resolution wave module to assess the non-motion resolution on both protocols.

With ultra-fast scans 59-70% of the investigated areas in 30 patients were scored as having no artefacts versus 10-29% of the standard speed scans (p < 0,001). General image quality was scored excellent or good in 94% of the cases with ultra-fast scans and in 59% of the cases with standard speed scans (p < 0,001). Comparing anatomical structures, ultra-fast scans were considered equal or better than standard speed scans in 78%/90%/93%/92%/91%/74% of the examinations (lung parenchyma/pulmonary fissures/segmental bronchi/pleuromediastinal border/carina/pulmonary vessels). Phantom scans showed a slight reduction in volumetric resolution MTF_xyz, and no change in in-plane resolution, MTF_xy.

In this study, ultra-fast scans reduce motion artefacts and increase image quality in low dose non-contrast chest CT when compared to standard speed scans, despite a possible slight degradation in resolution in non-moving objects.