Print version ISSN 0122-7483
AGULLES-PEDROS, Luis; ACOSTA, Rodolfo H.; BLUMLER, Peter and SPIESS, Hans W.. Diffusion influence on gas magnetic resonance imaging. Univ. Sci. [online]. 2008, vol.13, n.3, pp. 281-289. ISSN 0122-7483.
Resolution of nuclear magnetic resonance (NMR) experiments with gases employing magnetic field gradients is greatly reduced due to their rapid diffusion. In this paper, we present a solution to this problem based on a mixture of gases hyperpolarized with laser (LP) (3He or Xe) with other heavier and lighter buffer gases. In this way the diffusion coefficient can be modified up to one order of magnitude. The signal of 1D images of 3He is described as a function of the concentration in a binary mixture of gases, and we show the existence of an optimum concentration for some image resolution parameters. Experiments show that with this concentration, the signal can gain an increase of up to 10 times the signal with pure 3He, in agreement with the theory of non-restricted diffusion. Finally, the method is illustrated with 2D images of LP-3He mixed with several gases in a lung containing restrictive cavities with different sizes.
Keywords : gas MRI; restricted diffusion; lung; buffer gas; contrast; hyperpolarized gases.