Measurement of pulmonary clearance of radioaerosol using a portable sodium iodide probe.
To determine whether a portable sodium iodide (NaI) probe could provide a valid measure of the pulmonary half-life (T1/2) of aerosolized technetium-99m-diethylenetriaminepentaacetate (99mTc-DTPA, mol wt = 492) in small chests, we measured pulmonary clearance in rabbits using a gamma-scintillation camera and the portable probe. In 10 experiments the lungs of New Zealand White rabbits were insufflated with aerosolized 99mTc-DTPA (0.6 mum aerodynamic mass median diameter) and then simultaneously imaged with the gamma-camera and the probe positioned over the upper right lung. In an additional 12 experiments, alveolar-capillary membrane permeability was increased by either intratracheal instillation of 0.1 N hydrochloric acid (HCl) or intravenous injection of 100 mg/kg of oleic acid. All animals tolerated the procedure. There was a significant decrease in pulmonary T1/2 in both the HCl group (53.4 +/- 10.4 min, mean +/- SE) and the oleic acid group (14.7 +/- 2.3 min) when compared with control (127.5 +/- 18.1 min). When we compared the T 1/2 of the right lung determined by the gamma-camera with that measured by the probe, the correlation coefficient was 0.95. Potential nonpulmonary contributions to thoracic radioactivity were not significant. We conclude that a portable NaI probe is a valid means of determining T 1/2 of 99mTc-DTPA in small chests when compared with a gamma-camera and can detect increases in the permeability of the alveolar-capillary membrane to small solutes.
D000336:Aerosols; D000818:Animals; D005069:Evaluation Studies as Topic; D006851:Hydrochloric Acid / Q000494:pharmacology; D007454:Iodides; D008168:Lung / Q000000981:diagnostic imaging / Q000378:metabolism*; D019301:Oleic Acid; D009829:Oleic Acids / Q000494:pharmacology; D004369:Pentetic Acid / Q000378:metabolism*; D011817:Rabbits; D011877:Radionuclide Imaging; D012974:Sodium Iodide; D013667:Technetium / Q000378:metabolism*; D016284:Technetium Tc 99m Pentetate
D000336:Aerosols; D007454:Iodides; D009829:Oleic Acids; D019301:Oleic Acid; D013667:Technetium; D004369:Pentetic Acid; D012974:Sodium Iodide; D006851:Hydrochloric Acid; D016284:Technetium Tc 99m Pentetate