Purpose: To assess the efficacy of virtual monoenergetic images (VMI) from Spectral Detector Computed Tomography (SDCT) in reducing the effect of metal artifacts in chest and abdominal CT examinations.
Materials and Methods: The study population consisted of 59 consecutive patients with metal devices (pacemakers, ports, screws or prosthetic joints) that underwent routine chest and/or abdominal CT examination on a dual-layer SDCT. Only patients with metal artifact affecting muscular tissue were included. No special metal artifact reduction software was used. The area of maximal hypodensity in the artifact was compared to a control area – an area that was not affected by the artifact in the same muscle or in a counterpart muscle on the opposite side. The attenuation values of these areas were recorded from the conventional images and the VMI of 80keV, 100keV, 110keV, 120keV, 130keV, 140keV, 160keV, 180 keV and 200 keV. In addition, two radiologists evaluated the general image quality and the artifact intensity on the conventional images and on the 9 different monoenergetic levels mentioned above, using a 5 point Likert scale. They were also asked to choose an optimal monoenergetic level in which the artifact is least prominent.
Results: The metallic artifact improved significantly on the high monoenergetic images in all the patients (p=0.000), according to the quantitative analysis. The attenuation value of the artifact area approached the value of the selected control area in 39 patients (66.1%). High monoenergetic images (100keV or higher) significantly improved the general image quality and reduced the artifact intensity in all the patients (p=0.000) compared to the conventional images, on the subjective analysis. In 35 patients (59.3%) the artifact intensity decreased to a minimal level using the high monoenergetic images. The optimal monoenergetic level selected by the readers was 110keV or higher for all patients, with a median of 140keV.
Conclusion: High monoenergetic images from SDCT reduce metal artifacts in routine chest and abdominal CT examinations, without the need for a special examination protocol or pre-planning.
