Three-dimensional, in vivo MRI with self-gating and image coregistration in the mouse.

Motion during magnetic resonance imaging (MRI) scans routinely results in undesirable image artifact or blurring. Since high-resolution, three-dimensional (3D) imaging of the mouse requires long scan times for satisfactory signal-to-noise ratio (SNR) and image quality, motion-related artifacts are likely over much of the body and limit applications of mouse MRI. In this investigation, we explored the use of self-gated imaging methods and image coregistration for improving image quality in the presence of motion. Self-gated signal results from a modified 3D gradient-echo sequence showed detection of periodic respiratory and cardiac motion in the adult mouse-with excellent comparison to traditional measurements, sensitivity to respiration-induced tissue changes in the brain, and even detection of embryonic cardiac motion in utero. Serial image coregistration with rapidly-acquired, low-SNR volumes further enabled detection and correction of bulk changes in embryo location during in utero imaging sessions and subsequent reconstruction of high-quality images. These methods, in combination, are shown to expand the range of applications for 3D mouse MRI, enabling late-stage embryonic heart imaging and introducing the possibility of longitudinal developmental studies from embryonic stages through adulthood.