Diffusion microscopic MRI of the mouse embryo: Protocol and practical implementation in the splotch mouse model

Abstract

PurposeAdvanced methodologies for visualizing novel tissue contrast are essential for phenotyping the ever‐increasing number of mutant mouse embryos being generated. Although diffusion microscopic MRI (μMRI) has been used to phenotype embryos, widespread routine use is limited by extended scanning times, and there is no established experimental procedure ensuring optimal data acquisition.MethodsWe developed two protocols for designing experimental procedures for diffusion μMRI of mouse embryos, which take into account the effect of embryo preparation and pulse sequence parameters on resulting data. We applied our protocols to an investigation of the splotch mouse model as an example implementation.ResultsThe protocols provide DTI data in 24 min per direction at 75 μm isotropic using a three‐dimensional fast spin‐echo sequence, enabling preliminary imaging in 3 h (6 directions plus one unweighted measurement), or detailed imaging in 9 h (42 directions plus six unweighted measurements). Application to the splotch model enabled assessment of spinal cord pathology.ConclusionWe present guidelines for designing diffusion μMRI experiments, which may be adapted for different studies and research facilities. As they are suitable for routine use and may be readily implemented, we hope they will be adopted by the phenotyping community. Magn Reson Med 73:731–739, 2015. © 2014 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the originalwork is properly cited.

Experimental assessment of cardiovascular physiology in the chick embryo

“…Beyond high resolution imaging of soft tissues, flow μ-MRI is a modality used to measure blood flows, and was previously adapted for imaging mouse embryos. [103][104][105] Noting that the above techniques described in this short review were all also adapted from mouse embryo protocols, it is probable that flow μ-MRI techniques will be adapted for chick embryos. Further improvements in technology and software enhanced spatial resolution to enable investigators to quantify several cardiac variables (in ovo).…”

“…Indeed, the resolution and applications suggest that this powerful technique can be used for chick embryo cardiac research. Beyond high resolution imaging of soft tissues, flow μ‐MRI is a modality used to measure blood flows, and was previously adapted for imaging mouse embryos 103‐105 . Noting that the above techniques described in this short review were all also adapted from mouse embryo protocols, it is probable that flow μ‐MRI techniques will be adapted for chick embryos.…”

Recent Progress in Magnetic Resonance Imaging of the Embryonic and Neonatal Mouse Brain

“…It is necessary to note that, for diffusion MRI, Gd-based contrast agents should be added at lower concentration than conventional T 1 /T 2 -weighted MRI (~ 2 mM for Gd-DTPA vs. 20 mM for ProHance as in Petiet et al, 2008 ) due to the fact that high concentration of Gd-based contrast agent can shorten tissue T 2 values to the extent that signal attenuation due to spin-spin relaxation during the diffusion encoding time will cancel the gain from shortened T 1 . Norris et al reported an optimized for ex vivo diffusion MRI of the embryonic mouse brain (Norris et al, 2015 ). Fast imaging can be achieved using the modified diffusion weighted sequence, such as diffusion weighted fast spin echo or gradient-and-spin echo (GRASE) sequences (Aggarwal et al, 2010 ; Norris et al, 2013a ).…”