Comparison of oxygen-15 PET and transcranial Doppler CO2-reactivity measurements in identifying haemodynamic compromise in patients with symptomatic occlusion of the internal carotid artery

Background Transcranial Doppler (TCD) CO 2 -reactivity and oxygen-15 positron emission tomography (PET) have both been used to measure the cerebral haemodynamic state in patients who may have a compromised blood flow. Our purpose was to investigate whether PET and TCD identify the same patients with an impaired flow state of the brain in patients with internal carotid artery (ICA) occlusion. Methods Patients with recent transient ischaemic attack or minor ischaemic stroke associated with ICA occlusion underwent TCD with measurement of CO 2 -reactivity and oxygen-15 PET within a median time interval of 6 days. Results We included 24 patients (mean age 64 ± 10 years). Seventeen (71%) patients had impaired CO 2 -reactivity (≤20%), of whom six had absent reactivity (0%) or steal (