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Motion-related spiral artefact. (a) and (b) Axial processed arterial spin labelling (ASL) images acquired with background suppression in an uncooperative paediatric patient. Severe head motion has led to spirals of high signal intensity due to the spiral three-dimensional read-out mode, inherent to these sequences. (c)–(e) Sequential axial source images of the same patient. Diagnostic quality images were re-obtained with patient sedation (images not shown).
