Inclusion Criteria:  Children of both sexes, aged 6 months to 6 years, ASA score I to IV, Requiring standard magnetic resonance imaging due to clinical condition, regardless of underlying pathology, Sedation performed by an anesthesiologist, Written informed consent in accordance with the ICH-GCP and local legislation prior to trial entry.  Exclusion Criteria:  Contraindications to MRI (cardiac pacemaker, neurostimulator, ferromagnetic implant), Sedation carried out by a non-anesthesiologist, Emergency MRI, Presence of head trauma, Presence of nasal congestion or upper respiratory tract infection on the day of sedation, Multiple procedures during the same sedation (operating room, evoked potentials, etc.), Children with pathologies requiring airway safety, Any known allergic or hypersensitivity reaction to dexmedetomidine, Any known allergic or hypersensitivity reaction to benzodiazepines, Concomitant use of negative chronotropes, as Digoxine, Patient known with chronic respiratory failure or myasthenia, Patient known with anatomical abnormality of the airway, lung disease or sleep apnea syndrome Patient with known cardiac rhythm abnormality or cardio-vascular disease, Patient with known hepatic disorder or chronic kidney disease, Patient with hypotension or bradycardia on the day of the examination, Patient with a BMI > 97th percentile (which corresponds to overweight, including obesity).