title: Retention of soluble 99mTc-DTPA in the human lung: 24-h postdeposition.
abstract: Clearance of low-molecular-weight solutes, e.g., radiolabeled chelate diethylenetriaminepentaacetate (DTPA), across epithelial surfaces of distal airways and the lung parenchyma is a broadly used technique to assess epithelial integrity. It has been generally assumed that clearance of solute follows a simple first-order process and that DTPA clearance through the respiratory epithelium and into blood and lymphatic channels is complete within a few hours. Using gamma-camera imaging and a radiolabeled aerosol of 99mTc-labeled DTPA, we observed in eight healthy subjects lung retention of radioisotope approximately 24 h postdeposition of the 99mTc-DTPA. Residual lung retention at the 24-h end point averaged 6.0 +/- 1.8 (SD)% of the amount of radioisotope initially deposited in the lung. This suggests that for normal healthy subjects a small amount of the 99mTc radioisotope, either in a dissociated or chelated form, is nonpermeable or slowly cleared from respiratory tisssues.
authors.affiliation: Department of Environmental Health Sciences, School of Hygiene and Public Health, The Johns Hopkins University, Baltimore, Maryland 21205, USA. mfoster@welchlink.welch.jhu.edu
authors.forename: W M
authors.initials: WM
authors.lastname: Foster
authors.forename: P T
authors.initials: PT
authors.lastname: Stetkiewicz
authors.forename: A N
authors.initials: AN
authors.lastname: Freed
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D000336:Aerosols; D004848:Epithelium / Q000378:metabolism; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000378:metabolism*; D008297:Male; D008863:Microspheres; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000008:administration & dosage / Q000493:pharmacokinetics*; D012115:Residual Volume; D016284:Technetium Tc 99m Pentetate / Q000008:administration & dosage / Q000493:pharmacokinetics*
chemical_list: D000336:Aerosols; D019275:Radiopharmaceuticals; D016284:Technetium Tc 99m Pentetate