Definition of regions of interest (ROI’s) in lateral gamma camera images.Superposition of the lateral gamma camera image with a representative sagittal CT slice in a healthy volunteer and definition of the different ROI’s: total nasal (TN), anterior upper (AU: frontal sinuses), anterior lower (AL: nostrils, nasal valve and first cm of inferior turbinate), posterior lower (PL: turbinates, nasal floor, hard and soft palate), and posterior upper (PU: upper posterior nasal cavity, middle turbinate, ethmoidal and sphenoidal sinuses), and sphenoidal sinuses (SS).