title: Impact of metal artefacts due to EEG electrodes in brain PET/CT imaging.
abstract: The goal of this study is to investigate the impact of electroencephalogram (EEG) electrodes on the visual quality and quantification of (18)F-FDG PET images in neurological PET/CT examinations. For this purpose, the scans of 20 epilepsy patients with EEG monitoring were used. The CT data were reconstructed with filtered backprojection (FBP) and with a metal artefact reduction (MAR) algorithm. Both data sets were used for CT-based attenuation correction (AC) of the PET data. Also, a calculated AC (CALC) technique was considered. A volume of interest (VOI)-based analysis and a voxel-based quantitative analysis were performed to compare the different AC methods. Images were also evaluated visually by two observers. It was shown with simulations and phantom measurements that from the considered AC methods, the MAR-AC can be used as the reference in this setting. The visual assessment of PET images showed local hot spots outside the brain corresponding to the locations of the electrodes when using FBP-AC. In the brain, no abnormalities were observed. The quantitative analysis showed a very good correlation between PET-FBP-AC and PET-MAR-AC, with a statistically significant positive bias in the PET-FBP-AC images of about 5-7% in most brain voxels. There was also good correlation between PET-CALC-AC and PET-MAR-AC, but in the PET-CALC-AC images, regions with both a significant positive and negative bias were observed. EEG electrodes give rise to local hot spots outside the brain and a positive quantification bias in the brain. However, when diagnosis is made by mere visual assessment, the presence of EEG electrodes does not seem to alter the diagnosis. When quantification is performed, the bias becomes an issue especially when comparing brain images with and without EEG monitoring.
authors.affiliation: Department of Nuclear Medicine and Medical Imaging Center, University Hospital Gasthuisberg and Katholieke Universiteit Leuven, Leuven, Belgium.
authors.forename: Catherine
authors.initials: C
authors.lastname: Lemmens
authors.forename: Marie-Louise
authors.initials: ML
authors.lastname: Montandon
authors.forename: Johan
authors.initials: J
authors.lastname: Nuyts
authors.forename: Osman
authors.initials: O
authors.lastname: Ratib
authors.forename: Patrick
authors.initials: P
authors.lastname: Dupont
authors.forename: Habib
authors.initials: H
authors.lastname: Zaidi
mesh_terms: D016477:Artifacts; D001921:Brain / Q000000981:diagnostic imaging*; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000295:instrumentation*; D004827:Epilepsy / Q000000981:diagnostic imaging; D006801:Humans; D008670:Metals; D049268:Positron-Emission Tomography / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D008670:Metals