Cardiac phenotyping in ex vivo murine embryos using µ MRI

Microscopic MRI ( µ MRI) is an emerging technique for high‐throughput phenotyping of transgenic mouse embryos, and is capable of visualising abnormalities in cardiac development. To identify cardiac defects in embryos, we have optimised embryo preparation and MR acquisition parameters to maximise image quality and assess the phenotypic changes in chromodomain helicase DNA‐binding protein 7 ( Chd7 ) transgenic mice. µ MRI methods rely on tissue penetration with a gadolinium chelate contrast agent to reduce tissue T 1 , thus improving signal‐to‐noise ratio (SNR) in rapid gradient echo sequences. We investigated 15.5 days post coitum (dpc) wild‐type CD‐1 embryos fixed in gadolinium‐diethylene triamine pentaacetic acid (Gd‐DTPA) solutions for either 3 days (2 and 4 mM) or 2 weeks (2, 4, 8 and 16 mM). To assess penetration of the contrast agent into heart tissue and enable image contrast simulations, T 1 and T were measured in heart and background agarose. Compared to 3‐day, 2‐week fixation showed reduced mean T 1 in the heart at both 2 and 4 mM concentrations ( p