LAUSR

Background: Planar gamma scintigraphy is a powerful tool in therapeutic aerosol studies to evaluate inhaled drug delivery to the lungs. Alas, different laboratories use different approaches for analysing and quantifying aerosol lung deposition and its airway distribution, making it difficult to compare data. Aim: To compare the most common analysis approaches, assess total and regional deposition of inhaled aerosol and highlight similarities and differences. The eventually aim is to draw nearer to a consensus on standardized methodology for defining lung regions of interest so that data from different laboratories may be compared. Method: The six most frequently reported methods in the literature to define lung regions of interest were compared. The primary index to evaluate differences between the six methods was penetration index (PI); a measure of regional lung distribution expressed as the central to peripheral deposition ratio for inhaled therapeutic aerosols normalised by the same ratio for a Krypton gas scan. Data from 12 mild asthmatic patients (FEV1=86. %pred) inhaling monodisperse albuterol aerosols of particle size 1.5, 3, and 6 µm(total of 47 gamma scintigraphy images each to be analysed by 6 methods) were analysed using the HERMES Nuclear Medicine data analysis software (Hermes Medical Solutions, Stockholm, Sweden). Results: PI values were generated for the three droplet sizes of aerosol (1.5, 3 and 6 µm) in all subjects in all methods. PI values show greater variability between methods 1, 2, and 4, but were more consistent between methods 3, 5, and 6.