Comparison of clinical data sets acquired on different tomographs using 6-F-18-L-dopa

Longitudinal positron emission tomography (PET) studies of 6-F-18-L-dopa up take in the striatum are used to assess the progression of Parkinson's dise ase or the survival of neuronal cells grafted in parkinsonian patients, The se studies are performed over several years, and data analysis may suffer f rom the change from old tomographs to new machines with better sensitivity and spatial resolution. Furthermore, such studies on parkinsonian patients may be accomplished in either 2D or 3D acquisition mode. The aforementioned improvements offer gnat benefits for the study of neurodegenerative diseas es, especially those affecting the striatum. However, direct comparison of data is not straightforward owing to variation in scanner characteristics. In this study, we assessed the feasibility of comparing the 6-F-18-L-dopa s triatal uptake values (K-c) measured in two groups of healthy subjects usin g two tomographs of different generations. We re-studied and compared acqui sitions performed on 14 healthy subjects using 6-F-18-L-dopa. Half of these studies had been performed in 2D acquisition mode using an ECAT 953B. The other half had been performed in 3D acquisition mode using an ECAT EXACT HR +. Different reconstruction protocols were used and the K-c values obtained were statistically compared. The results showed that lowering the transver se spatial resolution of images obtained with the scanner having the better spatial resolution, so that it more closely marched that of the other mach ine, allowed similar K-c values to be obtained in healthy subjects, This st udy shows that quantitative results of 6-F-18-L-dopa scans can be matched b etween different scanners with different intrinsic resolutions. This can be accomplished using adequate modifications of the reconstruction parameters . Such modifications can be used to help in the longitudinal monitoring of parkinsonian patients using different tomographs.