Martin John Graves

Dear Editor, We thank Dr Steckner for his important comments regarding MR safety and for identifying an error in our paper that we think arose either from us imbibing too much Christmas sherry, or a naughty elf messing with the manuscript. Our reference to the “5 gauss line” is incorrect. The actual value at which the armchair experienced independent movement was over 200mT. The red line shown in Figures 1 and 3 should be identified as the 200mT line.

Warning signs are usually visible from the registration areas to the changing areas, and even on the door of the magnet room. Staff members also routinely check if patients are carrying magnetic or metallic objects before entering the MRI room. At our institutions, physical checklists must be signed by a trained member of staff before the patient is allowed to enter the magnet room.

Abstract It is around 20 years since the first commercial 3 T MRI systems became available. The theoretical promise of twice the signal-to-noise ratio of a 1.5 T system together with a greater sensitivity to magnetic susceptibility-related contrast mechanisms, such as the blood oxygen level dependent effect that is the basis for functional MRI, drove the initial market in neuroradiology.