Experimental Investigation of the Limits of Validity of the Physical Basis of a Method for in Vivo Lung Morphometry with 3He Diffusion MRI

Juan Parra-Robles¹, Salma Ajraoui¹, Martin H. Deppe¹, Steven R. Parnell¹, Jim M. Wild¹

In this work, the limits of validity of physical basis of a model of ³He MR lung diffusion are investigated experimentally in simple geometric models. The experimental results have highlighted limitations of the cylinder model. Breakdown of the Gaussian phase approximation was experimentally demonstrated for gradient strengths commonly used in lung ADC experiments, as the localized diffusion regime is approached. The physical assumptions of the cylinder model are only valid if the localized diffusion regime and its neighboring intermediate regimes are avoided.