Introduction:The implementation of spatial-covariance [18F]fluorodeoxyglucose positron emissiontomography–based disease-related metabolic brain patterns as biomarkers has been hampered by in-tercenter imaging differences. Within the scope of the JPND-PETMETPAT working group, we illus-trate the impact of these differences on Parkinson’s disease–related pattern (PDRP) expressionscores.Methods:Five healthy controls, 5 patients with idiopathic rapid eye movement sleep behavior dis-order, and 5 patients with Parkinson’s disease were scanned on one positron emission tomography/computed tomography system with multiple image reconstructions. In addition, one Hoffman 3DBrain Phantom was scanned on several positron emission tomography/computed tomography sys-tems using various reconstructions. Effects of image contrast on PDRP scores were also examined.Results:Human and phantom raw PDRP scores were systematically influenced by scanner andreconstruction effects. PDRP scores correlated inversely to image contrast. A Gaussian spatial filterreduced contrast while decreasing intercenter score differences.Discussion:Image contrast should be considered in harmonization efforts. A Gaussian filter mayreduce noise and intercenter effects without sacrificing sensitivity. Phantom measurements will beimportant for correcting PDRP score offsets.