Reproducibility and comparison of oxygen-enhanced T$$_1$$ quantification in COPD and asthma patients

Please always quote using this URN: urn:nbn:de:bvb:20-opus-171833
• T$$_1$$ maps have been shown to yield useful diagnostic information on lung function in patients with chronic obstructive pulmonary disease (COPD) and asthma, both for native T$$_1$$ and ΔT$$_1$$, the relative reduction while breathing pure oxygen. As parameter quantification is particularly interesting for longitudinal studies, the purpose of this work was both to examine the reproducibility of lung T$$_1$$ mapping and to compare T$$_1$$ found in COPD and asthma patients using IRSnapShotFLASH embedded in a full MRI protocol. 12 asthma and 12T$$_1$$ maps have been shown to yield useful diagnostic information on lung function in patients with chronic obstructive pulmonary disease (COPD) and asthma, both for native T$$_1$$ and ΔT$$_1$$, the relative reduction while breathing pure oxygen. As parameter quantification is particularly interesting for longitudinal studies, the purpose of this work was both to examine the reproducibility of lung T$$_1$$ mapping and to compare T$$_1$$ found in COPD and asthma patients using IRSnapShotFLASH embedded in a full MRI protocol. 12 asthma and 12 COPD patients (site 1) and further 15 COPD patients (site 2) were examined on two consecutive days. In each patient, T$$_1$$ maps were acquired in 8 single breath-hold slices, breathing first room air, then pure oxygen. Maps were partitioned into 12 regions each to calculate average values. In asthma patients, the average T$$_{1,RA}$$ = 1206ms (room air) was reduced to T$$_{1,O2}$$ = 1141ms under oxygen conditions (ΔT$$_1$$ = 5.3%, p < 5⋅10$$^{−4})$$, while in COPD patients both native T$$_{1,RA}$$ = 1125ms was significantly shorter (p < 10$$^{−3})$$ and the relative reduction to T$$_{1,O2}$$ = 1081ms on average ΔT$$_1$$ = 4.2%(p < 10$$^{−5}$$). On the second day, with T$$_{1,RA}$$ = 1186ms in asthma and T$$_{1,RA}$$ = 1097ms in COPD, observed values were slightly shorter on average in all patient groups. ΔT$$_1$$ reduction was the least repeatable parameter and varied from day to day by up to 23% in individual asthma and 30% in COPD patients. While for both patient groups T$$_1$$ was below the values reported for healthy subjects, the T$$_1$$ and ΔT$$_1$$ found in asthmatics lies between that of the COPD group and reported values for healthy subjects, suggesting a higher blood volume fraction and better ventilation. However, it could be demonstrated that lung T$$_1$$ quantification is subject to notable inter-examination variability, which here can be attributed both to remaining contrast agent from the previous day and the increased dependency of lung T$$_1$$ on perfusion and thus current lung state.