Volume 1 Supplement 1
Quantification and accuracy of clinical [11C]-PiB PET/MRI: the effect of MR-based attenuation correction
© Law et al; licensee Springer 2014
Published: 29 July 2014
The Dixon-Water-Fat segmentation (DWFS) method is a standard attenuation correction (AC) method in PET/MRI on the Siemens mMR and has demonstrated a systematic quantitative bias in [18F]-FDG-PET/MRI studies of the brain compared to PET/CT. The aim of this study was to evaluate the impact of DWFS-AC in a hybrid PET/MR scanner on regional and global quantitation of [11C]-PiB cerebral amyloid imaging of the brain and in the clinical reading.
Twenty-eight healthy volunteers, 6 with mild cognitive impairment (MCI), 4 with Alzheimers disease (AD), and 6 other dementia cases underwent a simultaneous PET/MRI (Siemens mMR) acquisition 40 min pi of (170-709) MBq [11C]-PiB. A single 30 min frame was reconstructed twice (OSEM-3D, 21it 4 sub, 5 mm Gauss) with the only difference being the AC calculation. AC was performed using either the standard DWFS or a head low-dose CT scan acquired independently on the same day. Activity concentration (Bq/mL) was sampled on AC-PET from symmetrically delineated ROI’s. Ratios of region-to-cerebellar grey matter (SUVr) were calculated. Amyloid uptake was considered abnormal at cortical SUVr >1.5 or increased amyloid uptake in two or more grey matter regions on visual evaluation.
The average activity concentration in all ROI’s was biased by -18 % in DWFS-AC compared to CT-AC. Although the visual categorization of both, amyloid-positive (n=11) and -negative (n=33) scans was unaffected by DWFS-AC, 3 healthy subjects were quantitatively reclassified as amyloid positive. The SUVr values were overestimated by 0.11 in the caudate nuclei and 0.04 in lateral cortical ROI’s in DWFS-AC compared to CT-AC.
The visual and quantitative consequences of MR-AC using DWFS in the brain with [11C]-PiB exhibit a noticeable radially variable bias. Although robust in visual evaluation, the quantitative diagnostic criteria (SUVr) using this biomarker with DWFS-AC may need to be modified.
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.