Aerosolised radionuclides for functional imaging in COPD/asthma

Abstract

Radiolabelled aerosols provide a versatile means of studying the pathophysiology of lung disease. If aerosols consisting of small particles are used, a qualitative image of the distribution of ventilation is obtained. Larger particles are deposited by inertial impaction, mainly in larger airways. This mechanism is related to changes in the direction and velocity of airflow rather than to ventilation and is therefore very sensitive to airway narrowing. Measurements of aerosol deposition can therefore identify very early changes in the airways in chronic obstructive pulmonary disease (COPD) and asthma. Aerosols of solid particles can, when deposited on the ciliated mucosa, be used for assessment of mucociliary clearance and are useful for evaluation of therapeutic measures in COPD and asthma. Soluble tracers delivered as aerosols may be absorbed from the lungs into the bloodstream and provide a measure of the permeability of the alveolar–capillary barrier. Finally, radioactive aerosols are extensively used in the development of devices and formulations for inhaled pharmaceuticals.