Three-dimensional whole-heart T₂ mapping at 3T

Purpose Detecting variations in myocardial water content with T₂ mapping is superior to conventional T₂-weighted MRI since quantification enables direct observation of complicated pathology. Most commonly used T₂ mapping techniques are limited in achievable spatial and/or temporal resolution, both of which reduce accuracy due to partial-volume averaging and misregistration between images. The goal of this study was to validate a novel free breathing T₂ mapping sequence that overcomes these limitations. Methods The proposed technique was made insensitive to heart rate variability through the use of a saturation prepulse to reset magnetization every heartbeat. Respiratory navigator-gated, differentially T₂-weighted volumes were interleaved per heartbeat, guaranteeing registered images and robust voxel-by-voxel T₂ maps. Free breathing acquisitions removed limits on spatial resolution and allowed short diastolic windows. Accuracy was quantified with simulations and phantoms. Results Homogeneous three-dimensional (3D) T₂ maps were obtained from normal human subjects and swine. Normal human and swine left ventricular T₂ values were 42.3±4.0 and 43.5±4.3 ms, respectively. The T₂ value for edematous myocardium obtained from a swine model of acute myocardial infarction was 59.1±7.1 ms. Conclusion Free-breathing accurate 3D T₂ mapping is feasible and may be applicable in myocardial assessment in lieu of current clinical black blood, T₂-weighted techniques. Magn Reson Med 74:803-816, 2015.