Evaluation of New MRI Sequences Including 3D-FGAPSIR for the Optimization of Inflammatory Spinal Cord Lesions Research

* verification of inclusion and non-inclusion criteria * information and collection of consent * standard imaging protocol prescribed as part of the usual treatment: sagittal T1 and T2 slices after injection of contrast product (Gadolinium), 3D STIR and 3D PSIR sequence. * 3D FGAPSIR sequence at the level of the cervical cord for the duration of the additional sequence is 10 minutes, for a total examination time of 40 minutes (instead of 30 minutes)