The purpose of this paper was to note a potential source of error in magnet
ic resonance(MR) imaging. Magnetic resonance images were acquired for stere
otactic planning for GKS of a vestibular schwannoma in a female patient. Th
e images were acquired using three-dimensional sequence, which has been sho
wn to produce minimal distortion effects. The images were transferred to th
e planning workstation, but the coronal images were rejected.
By examination of the raw data and reconstruction of sagittal images throug
h the localizer side plate, it was clearly seen that the image of the squar
e localizer system was grossly distorted.
The patient was returned to the MR imager for further studies and a metal c
lasp on her brassiere was identified as the cause of the distortion.