High-resolution MRI for human embryos with isotropic 10 μm resolution at 9.4 T

Magnetic resonance (MR) microscopy of human embryos has contributed significantly to the development of human embryology. Higher-resolution MR microscopy will have obvious benefits, for example, in visualizing small structures that are blurred or lost in lower-resolution images, providing detailed information on the development and growth of various organs, and improving the accuracy of MR volumetry. However, high-resolution MR microscopy has yet to be realized because of many technical challenges. In this study, therefore, we have performed high-resolution MR microscopy for human embryos with isotropic resolutions of (12 μm)³ at full sampling and (10 μm)³ at compressed sensing, which far exceeds the resolution of previous embryonic MR studies. The hardware and the pulse sequence were improved to achieve higher spatial resolution. Line profile, signal-to-noise ratio, and histogram analysis using phantom images were performed to verify that the resolution and the voxel size were identical. Comparison with optical microscopy images of embryo specimens at the same developmental stage was performed to confirm that the microstructures were well delineated. Our results show that imaging at this high resolution effectively depicts the microstructures of human embryos. This technology is the cornerstone for constructing an unprecedented high-quality atlas that will contribute to the development of human embryology.