Echo Time-Dependent Observed Lung T(1) in Patients With Chronic Obstructive Pulmonary Disease in Correlation With Quantitative Imaging and Clinical Indices

BACKGROUND: There is a clinical need for imaging-derived biomarkers for the management of chronic obstructive pulmonary disease (COPD). Observed pulmonary T(1) (T(1) (TE)) depends on the echo-time (TE) and reflects regional pulmonary function. PURPOSE: To investigate the potential diagnostic value of T(1) (TE) for the assessment of lung disease in COPD patients by determining correlations with clinical parameters and quantitative CT. STUDY TYPE: Prospective non-randomized diagnostic study. POPULATION: Thirty COPD patients (67.7 ± 6.6 years). Data from a previous study (15 healthy volunteers [26.2 ± 3.9 years) were used as reference. FIELD STRENGTH/SEQUENCE: Study participants were examined at 1.5 T using dynamic contrast-enhanced three-dimensional gradient echo keyhole perfusion sequence and a multi-echo inversion recovery two-dimensional UTE (ultra-short TE) sequence for T(1) (TE) mapping at TE(1-5)  = 70 μsec, 500 μsec, 1200 μsec, 1650 μsec, and 2300 μsec. ASSESSMENT: Perfusion images were scored by three radiologists. T(1) (TE) was automatically quantified. Computed tomography (CT) images were quantified in software (qCT). Clinical parameters including pulmonary function testing were also acquired. STATISTICAL TESTS: Spearman rank correlation coefficients (ρ) were calculated between T(1) (TE) and perfusion scores, clinical parameters and qCT. A P-value <0.05 was considered statistically significant. RESULTS: Median values were T(1) (TE(1-5) ) = 644 ± 78 msec, 835 ± 92 msec, 835 ± 87 msec, 831 ± 131 msec, 893 ± 220 msec, all significantly shorter than previously reported in healthy subjects. A significant increase of T(1) was observed from TE(1) to TE(2) , with no changes from TE(2) to TE(3) (P = 0.48), TE(3) to TE(4) (P = 0.94) or TE(4) to TE(5) (P = 0.02) which demonstrates an increase at shorter TEs than in healthy subjects. Moderate to strong Spearman's correlations between T(1) and parameters including the predicted diffusing capacity for carbon monoxide (DLCO, ρ < 0.70), mean lung density (MLD, ρ < 0.72) and the perfusion score (ρ > -0.69) were found. Overall, correlations were strongest at TE(2) , weaker at TE(1) and rarely significant at TE(4) -TE(5) . DATA CONCLUSION: In COPD patients, the increase of T(1) (TE) with TE occurred at shorter TEs than previously found in healthy subjects. Together with the lack of correlation between T(1) and clinical parameters of disease at longer TEs, this suggests that T(1) (TE) quantification in COPD patients requires shorter TEs. The TE-dependence of correlations implies that T(1) (TE) mapping might be developed further to provide diagnostic information beyond T(1) at a single TE. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY: Stage 1.

• Triphan, S. M. F.
• Weinheimer, O.
• Gutberlet, M.
• Heußel, C. P.
• Vogel-Claussen, J.
• Herth, F.
• Vogelmeier, C. F.
• Jörres, R. A.
• Kauczor, H. U.
• Wielpütz, M. O.
• Biederer, J.
• Jobst, B. J.