Magnetic stimulation coil arrangement

A Magnetic Stimulation (MS) coil arrangement which utilises the effect of the positioning a ferromagnetic material to enhance the magnetic field on the patient side of the coil and reduce acoustic noise associated with the addition of ferromagnetic material. The invention comprises a distortion arrangement 34 for distorting a magnetic field produced by first and second coil windings and is at least partially positioned adjacent to the rearward side of the coil windings. The distortion arrangement comprises at least one ferromagnetic distortion formation in the form of a loop comprising a first loop portion and a second loop portion positioned such that the first loop portion is adjacent the rearward side of the first winding and the second loop portion is adjacent the rearward side of the second winding. The first and second coil windings comprise a peripheral edge portion intermediate the forward and rearward sides, and wherein the first and second loop portions extend adjacent and around the peripheral edge portion.