Pulmonary relaxometry with inversion recovery ultra-fast steady-state free precession at 1.5T.

PURPOSE To present a technique for simultaneous mapping of T1 , T2 , and relative spin density (M0 ) in human lung using inversion recovery ultra-fast steady-state free precession (IR-ufSSFP) imaging. METHODS Pulmonary relaxometry with IR-ufSSFP is based on an interleaved time series acquisition of 2D images acquired at 1.5T. The technique was tested in a phantom and in four healthy volunteers using breath-hold and electrocardiogram triggering. Typically, 30 transient state images were acquired in a single breath-hold within < 10 s. From the signal time course, voxel-wise nonlinear fitting yielded T1 , T2 , and M0 parameter maps. Furthermore, off-resonance and B1 effects were investigated in a phantom. RESULTS In the phantom, the observed T1 of 829 ± 2 ms and T2 of 105 ± 4 ms were in agreement with the reference T1 of 858 ± 1 ms and T2 of 104 ± 1 ms using spin echo methods. In volunteers, the average T1 of 1375 ± 102 ms and T2 of 66 ± 26 ms of lung tissue were in good agreement with the literature and were observed to be independent of the respiratory phase. Overall, high reproducibility was shown in a volunteer, yielding coefficient of variations of 0.03 for M0 , 0.004 for T1 , and 0.04 for T2 measurements. CONCLUSION IR-ufSSFP allows for fast and simultaneous quantitative mapping of the human lung. Magn Reson Med 77:74-82, 2017. © 2016 International Society for Magnetic Resonance in Medicine.