In vivo comparison of 2D and 3D T2* in the rat lung using hyperpolarized helium-3 MRI at 1.5 T

The transverse relaxation time, T2, of hyperpolarized helium-3 in the lungs is a measure of the MR signal duration and it is an important parameter for pulse sequence optimization and image contrast. The T2 has also shown promise in characterizing lung microstructure due to its sensitivity to local gradients caused by gas-tissue interfaces, whose abundance per unit volume changes with lung inflation and pathological modification [1,2,3]. Despite the lung’s three-dimensional, folded, extensible structure, most measurements of helium-3 T2 have been performed using 2D projection imaging which inherently neglects the effects of the complex microstructure on T2. This work uses five rats in vivo to compare the T2 in a 2D projection image with true 3D imaging with 3, 6, and 12 slices.