Influence of hilar deposition in the evaluation of the alveolar epithelial permeability on (99m)Tc-DTPA aerosol inhaled scintigraphy

PURPOSE: We investigated whether hilar radioaerosol deposition affects the clearance rate of technetium-99m-labeled diethylenetriaminepentaacetic acid ((99m)Tc-DTPA) from peripheral alveolar regions. MATERIALS AND METHODS: A total of 38 patients underwent (99m)Tc-DTPA inhalation lung scintigraphy. Six region of interest (ROI) patterns were adopted: ROI 1 was outlined around the entire hemithorax, and ROIs 2–6 were outlined around the hemithorax but excluded square ROIs of different size in the hilar region. Half-times (T(½)) were calculated with time-activity curves using onecompartment and two-compartment analyses. The T(½) of ROIs 1–5 were plotted against the T(½) of ROI 6, and regression lines were obtained with the least-squares method. The absolute values of the differences between surveyed values and regression line were calculated. The Wilcoxon test for trend and a single linear regression model were used to determine statistical significance. RESULTS: There were significant reductions in the absolute values of the differences between surveyed values and regression line from ROIs 1–5 by one-component analysis and the fast component of two-compartment analysis (P < 0.001). CONCLUSION: Our results suggest that the deposition of radioaerosol in the hilar region affects the clearance rate of (99m)Tc-DTPA from the alveoli in damaged lungs. The hilar region should be excluded from ROIs when alveolar epithelial permeability is evaluated.