Prediction of Delayed Cerebral Ischemia After Subarachnoid Hemorrhage Using Dynamic 18F-FDG PET/CT

Inclusion Criteria: * written informed consent to participate in the study must be obtained from the subject or proxy/legal representative prior to enrollment. * males and females aged 18 years and older. * SAH proven by computed tomography (CT) and that has occurred within the last 72 hours. * ruptured saccular aneurysm angiographically confirmed by digital subtraction angiogram or CT angiogram, which has been successfully secured by surgical clipping or endovascular coiling. * high-risk subjects for DCI: "thick clot" on the hospital admission CT (grade 3 or grade 4 on the modified Fisher Scale). * a woman of childbearing potential is eligible only if the serum pregnancy test performed during the screening period is negative. Exclusion Criteria: * PET/CT contradications * MRI contradications * gadolinium or meglumine hypersensitivity * glomerular filtration rate \<30mL/min * SAH due to other causes than ruptured saccular aneurysm. * post-HSA cardiac arrest. * high sustained ICP ( \>20mmHg lasting \>20min) despite optimal treatment. * significant and concomitant organ failure amongst the following: hypotension with systolic blood pressure \<90mmHg refractory to treatment; unresolved pulmonary edema or pneumonia with severe hypoxia defined as PaO2/FiO2 \<150; severe cardiac failure requiring inotropic support. * patients with "do-not-resuscitate" orders, withdrawal of care situation, dying patient. * vulnerable patient populations (minor, legal vulnerability, prisoner) * pregnant and nursing mothers.