Inclusion Criteria:  children aged between 2 and 10 years, undergoing outpatient anaesthesia for elective MRI under sedation, classified as American Society of Anesthesiologists (ASA) grade I-II.  Exclusion Criteria:  difficult airway, allergies to the study drugs, asthma, severe central nervous system disease (eg, brain tumour, uncontrolled seizures), mental motor retardation, the application of another procedure after MRI sedation, whose parents declined to participate in the study.