MR grid-tagging using hyperpolarized helium-3 for regional quantitative assessment of pulmonary biomechanics and ventilation

A new technique is demonstrated in six healthy human subjects that combines grid-tagging and hyperpolarized helium-3 MRI to assess regional lung biomechanical function and quantitative ventilation. 2D grid-tagging, achieved by applying sine-modulated RF-pulse trains along the frequency- and phase-encoding directions, was followed by a multislice fast low-angle shot (FLASH)-based acquisition at inspiration and expiration. The displacement vectors, first and second principal strains, and quantitative ventilation were computed, and mean values were calculated for the upper, middle, and lower lung regions. Displacements in the lower region were significantly greater than those in either the middle or upper region (P < 0.005), while there were no significant differences between the three regions for the two principal strains and quantitative ventilation (P = 0.11-0.92). Variations in principal strains and ventilation were greater between subjects than between lung zones within individual subjects. This technique has the potential to provide insight into regional biomechanical alterations of lung function in a variety of lung diseases.