Improving Awakening Prognostication After Non Anoxic Coma Using PET-MRI in Intensive Care Unit

18Fluoro-Desoxy-Glucose's infusion for PET (glucose neural metabolism assessment, with quantitative information permitted by radioactivity monitoring through arterial catheter ; dosage = 1,5 MBq/Kg + 18,5 MBq as loading dose 5 min= Outside the scanner, Installation and movement management: Curare+/- sedative injection with standardized routine care protocol 10 min= Outside the scanner, Starting PET continuous acquisitionT= 0, Morphological MRI sequences- 3DT1, 3DFlair, T2SE, T2 HR on brainstem, Susceptibility and simple Diffusion Weighted Imaging-Specifically dedicated MR sequences based upon clinical issues 25 min, MRI in Resting state N°1 (global short-term functional connectivity)13 min, MRI DTI acquisition, 64 directions, sensitive to white matter injury 8 min, IRM in 2D-Arterial Spin Labelling:Quantitative Cerebral blood flow information (no Gadolinium)-\>8 min, IRM in Resting state 2 (repeated occurrence to assess stationarity) 13 min, End of PET continuous acquisition