The Influence of Diffusion Time on the Measurement of the Short-Range 3He Diffusivity in Human Lungs

Juan Parra-Robles¹, Martin H. Deppe¹, Xiaojun Xu¹, Helen Marshall¹, Jim M. Wild¹

In this work, the effect of diffusion time on 3He ADC is investigated through experiments with healthy human volunteers. The results of this work show that the short-range ADC of 3He gas in human lungs decreases with increasing diffusion time, while its degree of non-monoexponentiality remained constant in the range 1.4-2.5 ms. The results demonstrate that the cylinder model produces inaccurate estimates of the airway dimensions as a consequence of incompletely accounting for the diffusion-time dependence in the model equations.