Monitoring of T2 with Application of Diffusion Gradients to Remove Microcirculation Contributions to Signal for Optimisation of Diffusion Protocols and Generation of Flow-Free T2 Maps

Neil P. Jerome¹, James A. d'Arcy¹, Matthew R. Orton¹, Thorsten Feiweier², Dow-Mu Koh³, Martin O. Leach¹, David John Collins¹

Diffusion-weighted MRI in the body must account for a microcirculation fraction, separate to self-diffusion, within imaging voxels. Explicit control of diffusion pulse length and delay allows reproducible application of diffusion gradients with varying echo times; calculation of mono-exponential T2 estimates with applied gradients of b=0 and b=200 s/mm² shows significant changes observed in liver, kidney and spleen. This suggests that the microcirculation component, with its own distinct T2, is being removed, allowing the generation of flow-free T2 maps more robustly estimating tissue T2s. This approach enables appropriate b-value choices when considering diffusion models that include or exclude microcirculation contribution.