Gradient-echo-based 3D submillisecond echo time pulmonary MR imaging: a preliminary usability study on clinical and preclinical MR scanners

Abstract

Objective: To preliminarily investigate a technical feasibility of a submillisecond echo time concurrent-dephasing-and-excitation (CODE) sequence for pulmonary MRI on clinical and preclinical MR scanners Methods: CODE imaging (echo time, 0.14 similar to 0.18 ms) was performed with American College of Radiology phantom at 3 T, 7 healthy volunteers at 1.5 and 3 T, 10 rabbits at 3 T, and 2 rodents at 9.4 T. Signal-to-noise ratio was compared in phantom. Image quality of human MRI was visually assessed on a 5-point scale for comparison between CODE and conventional lung MRI sequences. Visibility of bronchi, subcentimeter nodules, and MR air-bronchogram were assessed in animal studies. Results: In phantom study, signal-to-noise ratio was higher with CODE than with original three-dimensional ultrashort-echo time sequence (106.71 +/- 4.32 vs 91.66 +/- 3.54; p < 0.001). Image quality of human MRI was better with CODE than with conventional MRI sequences (p <= 0.002).Bronchi remained traceableup to the filth bronchial generation in CODE images in rabbits and rodents. 95.2% of metastatic nodules (diameter, 1.5 +/- 0.4 mm) and 93.8% of MR air-bronchogram (diameter, 0.9 +/- 0.2 mm) in rabbits. Conclusion: Submillisecond echo time pulmonary MRI was technically feasible by using CODE on various MR scanners. Advances in knowledge: CODE can be a practical alternative for lung MRI on both clinical and pre-clinical scanners, without challenges of free-induction-decay-based ultrashort-echo time sequences © 2018 The Authors. Published by the British Institute of Radiology