Metal artifact reduction by virtual monoenergetic reconstructions from spectral brain CT

Helena Mellander; Veronica Fransson; Kristina Ydström; Jimmy Lätt; Teresa Ullberg; Johan Wassélius; Birgitta Ramgren

doi:10.1016/j.ejro.2023.100479

Metal artifact reduction by virtual monoenergetic reconstructions from spectral brain CT

Eur J Radiol Open. 2023 Feb 3:10:100479. doi: 10.1016/j.ejro.2023.100479. eCollection 2023.

Authors

Helena Mellander^{1

2}, Veronica Fransson^{2

3}, Kristina Ydström^{2

3}, Jimmy Lätt¹, Teresa Ullberg^{1

2}, Johan Wassélius^{1

2}, Birgitta Ramgren^{1

2}

Affiliations

¹ Department of Medical Imaging and Physiology, Skåne University Hospital, Lund, Sweden.
² Department of Clinical Sciences, Lund University, Lund, Sweden.
³ Radiation Physics, Department of Hematology, Oncology and Radiation Physics, Skåne University Hospital, Lund, Sweden.

Abstract

Purpose: Conventional computed tomography (CT) images are severely affected by metal artifacts in patients with intracranial coils. Monoenergetic images have been suggested to reduce metal artifacts.The aim of this study was to assess metal artifacts in virtual monoenergetic images (VMIs) reconstructed from spectral brain CT.

Methods: Thirty-two consecutive patients with intracranial coils examined by spectral non contrast brain CT (NCCT) at our center between November 2017 and April 2019 were included. Attenuation and standard deviations were measured in regions of interest (ROIs) at predefined areas in artifact-free and artifact-affected areas. Measurements were performed in conventional polyenergetic images (CIs) and the corresponding data for VMIs were retrieved through spectral diagrams for the each ROI. Subjective analysis was performed by visual grading of CIs and specific VMIs by two neuroradiologists, independently.

Results: In artefact-affected image areas distal from the metal objects, the attenuation values decreased with higher energy level VMIs. The same effect was not seen for artefact-affected image areas close to the metal.Subjective rating of the artefact severity was significantly better in VMIs at 50 keV for one of the two reviewers compared to the CIs. Overall image quality and tissue differentiation scores were significantly higher for both reviewers in VMIs at 60 and 70 keV compared to CIs.

Conclusion: Our quantitative and qualitative image analysis shown that there is a small significant reduction of intracranial coils artifacts severity by all monoenergetic reconstructions from 50 to 200 keV with preserved or increased overall subjective image quality compared to conventional images.

Keywords: Aneurysm; CIs, conventional images; CSF, cerebrospinal fluid; CT, computed tomography; DECT, dual energy computed tomography; DLP, dose length product; DSA, digital subtraction angiography; Diagnostic imaging; HU, Hounsfield units; IQR, interquartile range; MRI, magnetic resonance imaging; Metal artifacts; Monoenergetic imaging; PACS, Picture Archiving and Communication System; ROI, region of interest; SD, standard deviation; SNR, signal-to-noise ratio; VMIs, virtual monoenergetic images; WM, white matter; X-ray computed tomography; keV, kiloelectron volt.