Oxygen enhanced lung MRI by simultaneous measurement of T1 and T2* during free breathing using ultrashort TE

PurposeTo provide a robust method for the simultaneous quantification of T-1 and T-2* in the human lung during free breathing. Breathing pure oxygen accelerates T-1 and T-2* relaxation in the lung. While T-1 shortening reflects an increased amount of dissolved molecular oxygen in lung tissue, T-2* shortening shows an increased concentration of oxygen in the alveolar gas. Therefore, both parameters reflect different aspects of the oxygen uptake and provide complementary lung functional information. Materials and MethodsA segmented inversion recovery Look-Locker multiecho sequence based on a multiecho 2D ultrashort TE (UTE) was employed for simultaneous T-1 and T-2* quantification. The radial projections follow a modified golden angle ordering, allowing for respiratory self-gating and thus the reconstruction of a series of differently T-1 and T-2*-weighted images in arbitrary breathing states. The method was evaluated in nine healthy volunteers while breathing room air and pure oxygen, with two volunteers examined at five oxygen concentrations. ResultsRelative differences of T-1 between 7.9% and 12.7% and of T-2* between 13.2% and 6.0% were found. ConclusionThe proposed method provides inherently coregistered, quantitative T-1 and T-2* maps in both expiration and inspiration from a single measurement acquired during free breathing and is thus well suited for clinical application.J. Magn. Reson. Imaging 2015;41:1708-1714. (c) 2014 Wiley Periodicals, Inc.