Quantitative comparison of regional distributions of inhaled Tc-99m DTPA aerosol and Kr-81m gas in coal miners' lungs.

Regional distributions of deposited Tc-99m diethylenetriamine pentaacetate aerosol (DPTA) and of Kr-81m were compared in the upright lungs of 22 coal miners with nonembolic pulmonary disease. Pixel-by-pixel distributions of Kr-81m and DPTA corrected for lung volume, as well as DTPA/Kr-81m ratios, were determined by computer analysis in each lung and plotted against lung position. DTPA was preferentially deposited in the basal regions of 36/44 lungs. In the same lungs, Kr-81m was preferentially distributed in the apical regions of 18 lungs, bilaterally in six subjects. Similar DTPA and Kr-81m regional distributions throughout both lungs were obtained in only 11 (50%) subjects. No significant correlations were found between regional particle deposition and pulmonary function measurements. The effects of gravity-related lung pressure gradients and ventilation-related particle residence time on the deposition of DTPA may limit its usefulness when quantitative information is required to evaluate subtle changes in ventilation in nonembolic pulmonary patients and for basic studies of ventilation and perfusion.