Functional Lung MRI in Chronic Obstructive Pulmonary Disease: Comparison of T1 Mapping, Oxygen-Enhanced T1 Mapping and Dynamic Contrast Enhanced Perfusion

Abstract

PurposeMonitoring of regional lung function in interventional COPD trials requires alternative endpoints beyond global parameters such as FEV1. T1 relaxation times of the lung might allow to draw conclusions on tissue composition, blood volume and oxygen fraction. The aim of this study was to evaluate the potential value of lung Magnetic resonance imaging (MRI) with native and oxygen-enhanced T1 mapping for the assessment of COPD patients in comparison with contrast enhanced perfusion MRI.Materials and Methods20 COPD patients (GOLD I-IV) underwent a coronal 2-dimensional inversion recovery snapshot flash sequence (8 slices/lung) at room air and during inhalation of pure oxygen, as well as dynamic contrast-enhanced first-pass perfusion imaging. Regional distribution of T1 at room air (T1), oxygen-induced T1 shortening (ΔT1) and peak enhancement were rated by 2 chest radiologists in consensus using a semi-quantitative 3-point scale in a zone-based approach.ResultsAbnormal T1 and ΔT1 were highly prevalent in the patient cohort. T1 and ΔT1 correlated positively with perfusion abnormalities (r = 0.81 and r = 0.80; p&0.001), and with each other (r = 0.80; p<0.001). In GOLD stages I and II ΔT1 was normal in 16/29 lung zones with mildly abnormal perfusion (15/16 with abnormal T1). The extent of T1 (r = 0.45; p<0.05), ΔT1 (r = 0.52; p<0.05) and perfusion abnormalities (r = 0.52; p<0.05) showed a moderate correlation with GOLD stage.ConclusionNative and oxygen-enhanced T1 mapping correlated with lung perfusion deficits and severity of COPD. Under the assumption that T1 at room air correlates with the regional pulmonary blood pool and that oxygen-enhanced T1 reflects lung ventilation, both techniques in combination are principally suitable to characterize ventilation-perfusion imbalance. This appears valuable for the assessment of regional lung characteristics in COPD trials without administration of i.v. contrast.

Influence of age and sex on the longitudinal relaxation time, T1, of the lung in healthy never‐smokers

“…One MRI method which has gained interest for application in the lung is quantification of the water proton longitudinal relaxation time T1 (T1‐mapping), and T1‐mapping as the read‐out for oxygen enhanced MRI, which has been shown to reflect the lung diffusing capacity . T1‐mapping and T1‐mapping of oxygen enhancement in the lung have been applied to study healthy subjects, diffuse lung disease, cystic fibrosis, asthma, pulmonary hypertension, chronic lung allograft dysfunction and in particular chronic obstructive pulmonary disease (COPD) . Considering that COPD alone is the third largest cause of death globally, surpassed only by cardio‐ and cerebrovascular disease, the interest in this noninvasive imaging technique is easy to appreciate.…”

“…3,4 T1-mapping and T1-mapping of oxygen enhancement in the lung have been applied to study healthy subjects, [5][6][7][8][9] diffuse lung disease, 10 cystic fibrosis, 11,12 asthma, 13,14 pulmonary hypertension, 15 chronic lung allograft dysfunction 16 and in particular chronic obstructive pulmonary disease (COPD). [17][18][19][20] Considering that COPD alone is the third largest cause of death globally, surpassed only by cardio-and cerebrovascular disease, 21 the interest in this noninvasive imaging technique is easy to appreciate. However, even though lung T1 has already been used as a read-out in clinical studies of for example COPD, 20 no detailed data have been presented for a well-defined healthy cohort.…”

“…22 A similar change in lung tissue compliance occurs in pulmonary emphysema which has already been shown to yield decreased lung T1. 10 Several studies of COPD 17,19,20 have compared patients and control groups, where severe disease is often associated with a high age. If T1 is correlated to age, this will introduce a statistical bias, possibly obscuring important findings.…”

Early detection and sensitive monitoring of CF lung disease: Prospects of improved and safer imaging

“…In addition, T1 mapping based on regional quantification of T1 relaxation times has emerged as another promising approach for the characterization of lung tissue and distribution of blood volume in the lungs . Emerging studies using T1 mapping in patients with CF demonstrated inhomogeneous T1 distribution that correlated with perfusion abnormalities, suggesting that reduced T1 relaxation times are at least partially related to reduced blood volume in affected areas .…”

“…Further, oxygen can be used as a volatile contrast agent to enhance signal from ventilated lung regions because of its paramagnetic properties and T1 time reduction . However, the added value of oxygen‐enhanced imaging may be limited in chronic airways disease, when T1 relaxation is already reduced in areas of impaired perfusion due to hypoxic pulmonary vasoconstriction …”