Tissue oxygenation mapping by combined chemical shift and T₁ magnetic resonance imaging

Purpose To propose a method for determining tissue oxygenation via the measurement of fat T 1 . The method is based on a 2D fat/water chemical shift‐encoded and T 1 ‐weighted acquisition. Theory and Methods A 2D data set was acquired with a fast spin echo sequence with several echo asymmetries and repetition times, wherein one dimension is related to the fat/water phase modulation and the other to the T 1 saturation recovery. A joint magnitude‐based process of phase modulation and T 1 evolution allowed for the collection of the fat fraction and T 1 maps with resolved fat or water dominance ambiguity while avoiding the phased error problem. Results In vitro imaging allowed for the attribution of fat content for different water/oil emulsions that demonstrated longitudinal relaxation rate (R 1 ) sensitivity to the oxygenated emulsion environment. The fat R 1 values were subsequently compared to reference values, which were measured using low receiver bandwidth acquisition to enhance water and fat signal separations. In vivo feasibility of tissue oxygenation assessment was demonstrated by investigating interscapular brown adipose tissue modifications during an air/carbogen challenge in rats. Conclusion The proposed method offers a precise and robust estimate of tissue oxygenation illustrated by the method's ability to detect‐brown adipose tissue oxygenation modifications. Magn Reson Med 79:1981–1991, 2018.