The root-mean-square error between the extrapolated topography and true extended topography at various diameters was then compared.

However, that study was performed outside the MR scanner, and the root-mean-square error in the head position measurement was 0.7 mm.

Results: The root-mean-square errors in the outer extrapolated region ranged from 30 to 220 microm, depending on the fit function used.