Diagnostic Performance of the Resistance Index (RI) for the Assessment of Cerebral Vasoreactivity in Transcranial Doppler

Inclusion Criteria: * The patient must have given their free and informed consent and signed the consent form * The patient must be a member or beneficiary of a health insurance plan * Stenosis ≥ 70% in diameter reduction in NASCET equivalent or occlusion of atheromatous origin of the cervical internal carotid artery, asymptomatic or symptomatic. * Presence of a temporal window sufficient to record the homolateral and contralateral middle cerebral artery. * Patient of legal age with free and informed consent. * Patient who has signed the consent form. * Patient affiliated or beneficiary of a health insurance plan. Exclusion Criteria: * The subject is participating in an interventional study, or is in a period of exclusion determined by a previous study * The subject refuses to sign the consent * It is impossible to give the subject informed information * The patient is under safeguard of justice or state guardianship * Contraindication to Acetazolamide Diamox® injection. * Absence of temporal acoustic window (non visualization of the cerebral parenchyma, no recordable intracranial vessel). * Insufficient temporal window (visualizable brain parenchyma, no recordable MCA) * Internal or common carotid artery stenosis ≥70% or occlusion, contralateral to the primary lesion. * Stenosis ≥50% of the middle cerebral artery homolateral or contralateral to the cervical lesion. * Patient in exclusion period determined by another study. * Patient under court protection, guardianship, or conservatorship. * Patient refusing to sign the consent form. * Patient unable to express his or her will (dementia, disturbed consciousness, etc.) * Patient for whom it is impossible to give informed information for health reasons or because of a language barrier. * Pregnant, parturient, or breastfeeding patient.