Effects of the use of multiple scanners and of scanner upgrade in longitudinal voxel‐based morphometry studies

PURPOSE: To evaluate the effects of inter-scanner variability (bias) and of scanner upgrade on longitudinal changes in regional gray matter volume. MATERIALS AND METHODS: A total of 215 normal subjects were scanned twice, at an interval of approximately 1 year, using two 3.0 Tesla (T) scanners of the exact same model. Both scanners were simultaneously upgraded during the study period. The subjects were divided into four groups according to the combination of scanners used at the two time points. Using VBM, we evaluated longitudinal changes in regional gray matter volume in each group and the effects of scanner upgrade on longitudinal changes. RESULTS: The use of different scanners at two time points significantly influenced longitudinal changes in regional gray matter volume. Regional gray matter volumes were relatively stable within the same scanner, but significantly different between the two scanners. Scanner upgrade had effects comparable to those of using different scanners at the two time points. CONCLUSION: The results of our study indicate that, even with scanners of the exact same model, the use of different scanners at different time points significantly influences longitudinal morphometric results, and that scanner upgrade has effects comparable to those of using different scanners at different time points.