Influence of hilar deposition in the evaluation of the alveolar epithelial permeability on 99mTc-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(1/2) were calculated with time-activity curves using one-compartment and two-compartment analyses. The T(1/2) of ROIs 1-5 were plotted against the T(1/2) 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.