A Model of Magnetization and Relaxation of Ferrimagnetic Particles in the Lung

Based on the previous experimental data on Fe3O4 particles in the lungs, a mathematical model has been developed of the dynamic behavior of these particles. The model treats magnetized particles in the lungs as permanent magnetic dipoles in a fluid medium, and is an extension of the classical theory of paramagnetism. Although the model is based on simple assumptions, it gives results which approximate the observed phenomena. Interpretation of our experimental data with this model gives an estimate of the energy responsible for randomizing the orientations of particles of approximately 10-18 J. We estimate the apparent viscosity of the surrounding medium to be approximately 100°N . s/M2. The model calculation and experimental results indicate that the randomizing process of the particle orientations is caused by some intracellular processes in alveolar macrophages.