Small but systematic bias introduced by EEG electrodes in PET imaging
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Purpose
Attenuation correction (AC) of PET images is essential for accurate quantification. Brain PET studies comprising simultaneous EEG (PET EEG ) may suffer from metal artifacts in CT images (CT EEG ), or improper correction when electrodes are not present in the CT (CT 0 ). As these influences are not well-characterized, we aim to compare metal artifact reduction (MAR) techniques for CT EEG images, and evaluate differences between attenuated-corrected PET EEG using CT 0 and CT EEG with MAR, synthetically placed electrodes (CT EEG-synth ) and extended Hounsfield unit (HU) range.
Methods
19 healthy participants underwent two total-body PET/CT scans with [ 18 F]FDG, with and without 32 EEG scalp electrodes, respectively. We evaluated five MARs to reduce streaks caused by the EEG electrodes in the CT EEG . Finally, CT 0 , CT EEG with (CT EEG-iMAR-Ext ) and without extended HU range (CT EEG-iMAR ) and CT EEG-synth were used to perform attenuation correction of PET EEG . We compared our results to PET 0 /CT 0 scan using relative differences.
Results
CT EEG and CT EEG-iMAR showed the smallest differences to CT 0 . PET EEG /CT EEG-iMAR-Ext exhibited the lowest differences to PET 0 /CT 0 (average bias across all regions of −0.46%), followed by similar performance of PET EEG /CT EEG-iMAR (−0.73%) and PET EEG /CT EEG (−0.76%). Conversely, PET EEG /CT 0 demonstrated the largest average differences (−1.81%), with values reaching −2.71% in the parietal lobe. These differences were consistent across subjects, yielding significant effects in most of the brain (p FWE < 0.05). CT EEG-synth performed not as good as CT EEG (−1.21%).
Conclusions
CT EEG with extended HU range is most suitable for attenuation correction of PET EEG images, with MAR correction offering little additional improvement.
