Resolution enhancement in MRI of laser polarized 3He by control of diffusion.

Diffusion of atoms or molecules in presence of magnetic field gradients not only attenuates the NMR signal but also leads to distortions close to restricting boundaries. This phenomenon is most evident in imaging with laser polarized (LP) noble gases. Diffusion of gases can be manipulated, however, by admixing inert gases of different molecular weight. In this work we analyze the effect of mixing LP-(3)He with SF(6) on the image quality of a phantom consisting of an arrangement of capillaries with different diameters. Admixing buffer gases of higher molecular weight changes the contrast and offers a means to record images with high spatial and time resolution. Additionally we demonstrate how distortions due to edge enhancement can be reduced even for long timed MRI-sequences.