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.
Highlights
Worldwide collaborative efforts [1,2] are underway to develop a comprehensive functional annotation of the mouse genome, which will serve as a rich resource for elucidating human gene function
We present two protocols for mouse embryo diffusion microscopic MRI (mMRI), together with guidelines for embryo preparation and imaging setup, which can be readily implemented to achieve a reasonable timeframe for data acquisition, making it suitable as a supplementary methodology for mouse embryo imaging and hopefully enabling more widespread use within the phenotyping community
We have developed two protocols for whole-body diffusion mMRI, which provided diffusion tensor imaging (DTI) data in 24 min per direction at 75 mm isotropic resolution, enabling preliminary and detailed screening in $ 3 h (6 directions plus one unweighted measurement) and $ 19 h (42 directions plus six unweighted measurements) per embryo, respectively
Summary
Worldwide collaborative efforts [1,2] are underway to develop a comprehensive functional annotation of the mouse genome, which will serve as a rich resource for elucidating human gene function. A dedicated screening pipeline will facilitate general mouse embryo phenotyping studies, such as investigations of the genetic causes of congenital abnormalities, and provide primary evidence to justify detailed follow-up studies This will give insight into the functional and structural consequences of gene inactivation in developmental processes, as well as better models of human diseases and novel therapies. Imaging platforms that enable detailed phenotyping include optical projection tomography (OPT) [6,7], microscopic computed tomography (mCT) [8,9], microscopic MRI (mMRI) [10,11] and high-resolution episcopic microscopy (HREM) [12,13] These modalities will most likely form the backbone of the screening pipeline as a complement to conventional optical histological examination, enabling acquisition of digital, high-resolution, three-dimensional (3D) data. To supplement this pool of techniques, advanced methodologies that enable visualization of novel tissue contrast will be essential for in-depth screening and assessment of specific pathologies
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