T1 mapping of the entire lung parenchyma: Influence of the respiratory phase in healthy individuals

Purpose: To determine the effect of respiratory phase on the T I values of the entire lung. Materials and Methods: We calculated T1 relaxation time on a pixel-by-pixel analysis of a series of Snapshot FLASH tomograms acquired after a single inversion pulse. Two sets of coronal T1 maps were acquired, one in full suspended inspiration and one in suspended expiration. Results: The average of the mean T1 values over the entire lung in inspiration was 1199 +/- 117 msec, the average of the mean T1 values in expiration was 1333 +/- 167 msec. This difference was statistically significant, at P = 0.005. In inspiration the average coefficient. of variation was 182 56 msec, in expiration it was 153 +/- 41 msec. This difference was not statistically significant. Conclusion: T1 measurements of the entire lung are feasible. Our findings underline the need for a close monitoring of the inspirational status during MR examinations of the thorax, notably when T1 measurements of the lung are performed.