Modeling the nuclear magnetic resonance behavior of lung: From electrical engineering to critical care medicine

The present article reviews the basic principles of a new approach to the c haracterization of pulmonary disease. This approach is based on the unique nuclear magnetic resonance (NMR) properties of the lung and combines experi mental measurements (using specially developed NMR techniques) with theoret ical simulations. The NMR signal from inflated lungs decays very rapidly co mpared with the signal from completely collapsed (airless) lungs. This phen omenon is due to the presence of internal magnetic field inhomogeneity prod uced by the alveolar ah-tissue interface (because air and water have differ ent magnetic susceptibilities). The air-tissue interface effects can be det ected and quantified by magnetic resonance imaging (MRI) techniques using t emporally symmetric and asymmetric spin-echo sequences. Theoretical models developed to explain the internal (tissue-induced) magnetic held inhomogene ity in aerated lungs predict the NMR lung behavior as a function of various technical and physiological factors (e.g., the level of lung inflation) an d simulate the effects of various lung disorders tin particular, pulmonary edema) on this behavior. Good agreement has been observed between the predi ctions obtained from the mathematical models and the results of experimenta l NMR measurements in normal and diseased lungs. Our theoretical and experi mental data have important pathophysiological and clinical implications, es pecially with respect to the characterization of acute lung disease (e.g., pulmonary edema) and the management of critically ill patients. Bioelectrom agnetics 20:110-119, 1999. (C) 1999 Wiley-Liss. Inc.