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Quantitative MRI measurement of lung density must account for the change in T 2 * with lung inflation
Author(s) -
Theilmann Rebecca J.,
Arai Tatsuya J.,
Samiee Ahsan,
Dubowitz David J.,
Hopkins Susan R.,
Buxton Richard B.,
Prisk G. Kim
Publication year - 2009
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.21866
Subject(s) - lung , lung volumes , functional residual capacity , nuclear medicine , medicine
Purpose To evaluate lung water density at three different levels of lung inflation in normal lungs using a fast gradient echo sequence developed for rapid imaging. Materials and Methods Ten healthy volunteers were imaged with a fast gradient echo sequence that collects 12 images alternating between two closely spaced echoes in a single 9‐s breathhold. Data were fit to a single exponential to determine lung water density and T 2 * . Data were evaluated in a single imaging slice at total lung capacity (TLC), functional residual capacity (FRC), and residual volume (RV). Analysis of variance for repeated measures was used to statistically evaluate changes in T 2 *and lung water density across lung volumes, imaging plane, and spatial locations in the lung. Results In normal subjects (n = 10), T 2 *(and [lung density/water density]) was 1.2 ± 0.1 msec (0.10 ± 0.02), 1.8 ± 0.2 ms (0.25 ± 0.04), and 2.0 ± 0.2 msec (0.27 ± 0.03) at TLC, FRC, and RV, respectively. Results also show that there is a considerable intersubject variability in the values of T 2 * . Conclusion Data show that T 2 *in the lung is very short, and varies considerably with lung volume. Thus, if quantitative assessment of lung density within a breathhold is to be measured accurately, then it is necessary to also determine T 2 * . J. Magn. Reson. Imaging 2009. © 2009 Wiley‐Liss, Inc.