Accuracy in gamma camera measurements of point source velocities

Mucociliary clearance is impaired in many diseases of the respiratory syste m. We have developed a method for measuring tracheal mucus velocity by the dynamic study of a single point source of radioactivity deposited in the tr achea by cricothyroid injection. Preliminary results suggest that patients with airways disease have very low tracheal mucus velocities (<2 mm.min(-1) ). The aim of this experiment was to explore the ability of current scintil lation detection systems to track a single point as it moves in a dynamic s tudy in small increments and at low velocity (movements of the order of 1 m m). Background noise was estimated to contribute an error in positioning of 0.16 mm (1 standard deviation). Overall errors in velocity were estimated at 0.2 mm.min(-1). This suggests that standard instrumentation in use in mo st nuclear medicine departments has the capacity to measure accurately velo cities as low as 1 mm.min(-1) ((C) 2000 Lippincott Williams & Wilkins).