title: Remanent magnetic fields for measuring particle retention and distribution in the lungs.
abstract: A relatively inexpensive method for the noninvasive in vivo detection of ferrimagnetic particles within the lungs of a large laboratory animal, viz., the donkey, is described. The particles were neutron activated prior to inhalation, which permitted a comparison of two different retention measurements for the same particles, i.e., a well-characterized radiological-detection method concurrent with the newer magnetic-field technique. The long-term clearance of the particles from the lung was monitored in terms of the reduction in initial remanent field following magnetization, and the reduction in gamma-ray flux reaching the collimated scintillation detectors. Comparison of the measurements confirmed that the reduction of the initial remanent-field values with time was due to particle clearance rather than a change of the iron state to a nonmagnetic form. This validates previous reports that particle clearance studies can be performed using remanent magnetic-field measurement techniques. However, remanent magnetic-field measurements require careful design and interpretation, since they are highly sensitive to the distribution of the particles within the effective viewing field.
mesh_terms: D000336:Aerosols; D000818:Animals; D004391:Dust; D004574:Electromagnetic Fields; D055590:Electromagnetic Phenomena; D005290:Ferric Compounds / Q000378:metabolism*; D052203:Ferrosoferric Oxide; D007501:Iron / Q000378:metabolism*; D007504:Iron Radioisotopes; D008168:Lung / Q000378:metabolism*; D010087:Oxides; D010527:Perissodactyla; D013997:Time Factors
chemical_list: D000336:Aerosols; D004391:Dust; D005290:Ferric Compounds; D007504:Iron Radioisotopes; D010087:Oxides; C001215:ferrite; D007501:Iron; D052203:Ferrosoferric Oxide