T1 mapping of the entire lung parenchyma: Influence of respiratory phase and correlation to lung function test results in patients with diffuse lung disease.

The T(1) values of lung parenchyma of 25 patients with fibrosis and emphysema were measured in the entire lung, and the effect of inspiration and expiration was investigated. T(1) map acquisition was based on a snapshot-fast low-angle shot (FLASH) sequence. Lung function and blood gas tests were measured. The study documents reverse respiratory phase dependence of T(1) measurements of the entire lung parenchyma in patients with emphysema and fibrosis. Furthermore, expiratory measurements showed higher and reverse differences between patient groups compared to inspiratory measurements. For the emphysema group, the average T(1) value in inspiration was 1033 +/- 74 ms. The average of the mean T(1) values in expiration was 982 +/- 56 ms. For the patients with fibrosis, the average T(1) value in inspiration was 996 +/- 103 ms. Compared to that, the average T(1) value in expiration was 1282 +/- 170 ms. Linear regression of T(1) vs. lung function parameters showed the highest regression coefficients for total lung capacity (TLC) and residual volume (RV) in expiration, the values were inversely proportionally dependent on the pooled expiratory T(1) values. These findings underline the strong but nonuniform influence of the inspirational status during T(1) measurements of the lung. T(1) maps in both emphysema and fibrosis should preferably be acquired at expiration if reliable data are to be obtained.