Fast and robust 3D T 1 mapping using spiral encoding and steady RF excitation at 7 T: application to cardiac manganese enhanced MRI (MEMRI) in mice

Mapping longitudinal relaxation times in 3D is a promising quantitative and non‐invasive imaging tool to assess cardiac remodeling. Few methods are proposed in the literature allowing us to perform 3D T 1 mapping. These methods often require long scan times and use a low number of 3D images to calculate T 1 . In this project, a fast 3D T 1 mapping method using a stack‐of‐spirals sampling scheme and regular RF pulse excitation at 7 T is presented. This sequence, combined with a newly developed fitting procedure, allowed us to quantify T 1 of the whole mouse heart with a high spatial resolution of 208 × 208 × 315 µm 3 in 10–12 min acquisition time. The sensitivity of this method for measuring T 1 variations was demonstrated on mouse hearts after several injections of manganese chloride (doses from 25 to 150 µmol kg −1 ). T 1 values were measured in vivo in both pre‐ and post‐contrast experiments. This protocol was also validated on ischemic mice to demonstrate its efficiency to visualize tissue damage induced by a myocardial infarction. This study showed that combining spiral gradient shape and steady RF excitation enabled fast and robust 3D T 1 mapping of the entire heart with a high spatial resolution. Copyright © 2015 John Wiley & Sons, Ltd.