Abstract
PurposeIn order to achieve comparability of image quality, harmonisation of PET system performance is imperative. In this study, prototype harmonisation criteria for PET brain studies were developed.MethodsTwelve clinical PET/CT systems (4 GE, 4 Philips, 4 Siemens, including SiPM-based “digital” systems) were used to acquire 30-min PET scans of a Hoffman 3D Brain phantom filled with ~ 33 kBq·mL−1 [18F]FDG. Scan data were reconstructed using various reconstruction settings. The images were rigidly coregistered to a template (voxel size 1.17 × 1.17 × 2.00 mm3) onto which several volumes of interest (VOIs) were defined. Recovery coefficients (RC) and grey matter to white matter ratios (GMWMr) were derived for eroded (denoted in the text by subscript e) and non-eroded grey (GM) and white (WM) matter VOIs as well as a mid-phantom cold spot (VOIcold) and VOIs from the Hammers atlas. In addition, left-right hemisphere differences and voxel-by-voxel differences compared to a reference image were assessed.ResultsSystematic differences were observed for reconstructions with and without point-spread-function modelling (PSFON and PSFOFF, respectively). Normalising to image-derived activity, upper and lower limits ensuring image comparability were as follows: for PSFON, RCGMe = [0.97–1.01] and GMWMre = [3.51–3.91] for eroded VOI and RCGM = [0.78–0.83] and GMWMr = [1.77–2.06] for non-eroded VOI, and for PSFOFF, RCGMe = [0.92–0.99] and GMWMre = [3.14–3.68] for eroded VOI and RCGM = [0.75–0.81] and GMWMr = [1.72–1.95] for non-eroded VOI.ConclusionsTo achieve inter-scanner comparability, we propose selecting reconstruction settings based on RCGMe and GMWMre as specified in “Results”. These proposed standards should be tested prospectively to validate and/or refine the harmonisation criteria.
Highlights
In clinical brain PET studies, images often are compared longitudinally or with a reference database
The growing need for multi-centre collaborations and data sharing in clinical brain research [2, 3] further highlights the need for image comparability between PET systems across multiple clinical centres
The recovery coefficients derived from the phantom PET image should yield RCGM = 1 and RCWM = 0.25
Summary
In clinical brain PET studies, images often are compared longitudinally or with a reference database. Rigorous quality control and assurance are required in order to prevent that variability and differences between PET systems with regard to image quality, can affect research conclusions or patient diagnostics. This is especially the case when the effects studied are small The growing need for multi-centre collaborations and (raw) data sharing in clinical brain research [2, 3] further highlights the need for image comparability between PET systems across multiple clinical centres. Since imaging system vendors use proprietary software, selecting apparently equivalent acquisition and reconstruction settings will not necessarily yield equivalent results (if equivalent settings are available at all)
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