Pneumologie 2015; 69 - A23
DOI: 10.1055/s-0035-1556615

Echo-time dependence of observed lung T1 in COPD patients: preliminary results

S Triphan 1, 2, M Wielpütz 1, 2, CP Heussel 2, 3, J Biederer 1, 2, HU Kauczor 1, 2, P Jakob 4, B Jobst 1, 2
  • 1University Hospital Heidelberg
  • 2Translational Lung Research Center Heidelberg (TLRC), Heidelberg
  • 3Thoraxklinik at University of Heidelberg
  • 4University of Würzburg

T1-quantification in the lungs has been demonstrated as a functional tool, especially for oxygen-enhanced imaging. Recently, free-breathing UTE-based methods were introduced to improve lung T1-quantification. This revealed a TE-dependency of measured lung T1, which was attributed to compartimentalisation effects more complex than previously assumed. Since this effect, which is seen best using UTE, reflects tissue composition, it may be of value in the diagnosis of diseases which affect the lung parenchyma. The purpose of this work was to examine this effect in COPD patients.

20 patients with COPD were examined using a free-breathing inversion recovery multi-gradient-echo 2D UTE sequence. Informed consent was ensured and the study was approved by the institutional ethics committee. Images were acquired at 5 TEs between 70µs and 2.3 ms. The total acquisition time for each measurement was 2 min. Respiratory motion was compensated using dc-gating, using 50% of projections for expiratory states. T1 maps at TE1 – 5 were calculated using per-pixel fits. T1 d maps from the difference in signal between the first and following echoes were also calculated.

For all examined patients the total average T1 in the lungs were T1 (70µs) = 646 ± 83 ms, T1 (0.5 ms) = 860 ± 98 ms, T1 (1.2 ms)= 858 ± 88 ms, T1 (1.65 ms) = 867 ± 118 ms, T1 (2.3 ms) = 843 ± 188 ms. The difference-T1 from the first and later echoes were T1 d (0.5 ms) = 462 ± 63 ms, T1 d (1.2 ms) = 545 ± 66 ms, T1 d (1.65 ms)= 589 ± 69 ms, T1 d (2.3 ms) = 634 ± 73 ms.

The T1 values were significantly shorter in COPD patients than those reported in healthy volunteers, which was expected from previous work. T1 d is also much shorter than in healthy volunteers. As shorter T1 are likely to indicate a reduced blood volume fraction, T1 mapping at different TE might help to differentiate hypoxic pulmonary vasoconstriction from combined tissue and perfusion loss in emphysema. The characteristic T1 and T1 d may also be useful to detect parenchymal destruction in emphysema and to discriminate airway- and emphysema-predominant phenotypes of COPD.

*Presenting author