Fast spin-echo for multiple mouse magnetic resonance phenotyping

High-resolution magnetic resonance imaging is emerging as a powerful tool for phenotyping mice in biologic studies of genetic expression, development, and disease progression. In several applications, notably random mutagenesis trials, large cohorts of mice must be examined for abnormalities that may occur in any part of the body. In the aim of establishing a protocol for imaging multiple mice simultaneously in a standardized high-throughput fashion, this study investigates variations of a three-dimensional fast spin-echo sequence that implements driven equilibrium, modified refocusing, and partial excitation pulses. Sequence variations are compared by simulated and experimental measurements in phantoms and mice. Results indicate that when using a short repetition time (TR <= T-1) a sequence employing a partial excitation tip angle provides both improved signal and good T-2 contrast compared with standard fast spin-echo imaging. This sequence is used to simultaneously acquire four live mouse head images at 100 mu m isotropic resolution with a scan time under 3 h at 7 T.