Optimization of Look-Locker Turbo-Field Echo-Planar Imaging and Evaluation of Its Accuracy in Head and Neck 3D T₁ Mapping

Abstract

Purpose: We present a sequence for T₁ relaxation-time mapping that enables a rapid and accurate measuring. The sequence is based on the Look-Locker method by employing turbo-field echo-planar imaging (TFEPI) acquisitions and time to free relaxation after constant application of the radiofrequency (RF) pulses. We optimized the sequence, and then evaluated the accuracy of the method in imaging of head and neck.
Materials and Methods: The method was implemented on a standard clinical scanner, and the accuracy of the T₁ value was evaluated against that with the two-dimensional (2D) inversion recovery method.
Results: The percentage errors of the T₁ value, as validated by phantom imaging measurements, were 3.1% for slow-relaxing compartments (T₁ = 2736 msec) and 1.1% for fast-relaxing compartments (T₁ = 264.2 msec).
Conclusion: We demonstrated a fast 3D sequence to obtain multiple slices, based on the Look-Locker method for T₁ measurement, which provided a rapid and accurate way of measuring the spin-lattice relaxation time. An acquisition time of approximately 5 min was achieved for T₁ mapping; in principle, this can provide head and neck coverage with 15 slices.