MAGNETIC RESONANCE IMAGE SYSTEM, Models and records: SEE CUSTOMER LETTER. ///. This fix applies to units of the following GE Healthcare IRM systems: Discovery MR450, Discovery MR750, Signa HDx, Signa HDxt, Signa HDi, GE 1.5T Signa HDe, Optima MR360, Brivo MR355, Signa Excite-HD 1.5T & 3T , Signa Excite 3.0T, Signa Contour / I, Signa OpenSpeed, Vectra, MR Max, Optima MR450w GEM, Discovery MR750W GEM, Optima MR450w, Signa Profile and Signa Ovation.