Mouse brain fixation to preserve in vivo manganese enhancement for ex vivo manganese-enhanced MRI

Abstract

Purpose To develop a tissue fixation method that preserves in vivo manganese enhancement for ex vivo magnetic resonance imaging (MRI). The needs are clear, as conventional in vivo manganese-enhanced MRI (MEMRI) applied to live animals is time-limited, hence limited in spatial resolution and signal-to-noise ratio (SNR). Ex vivo applications can achieve superior spatial resolution and SNR through increased signal averaging and optimized radiofrequency coil designs. A tissue fixation method that preserves in vivo Mn2+ enhancement postmortem is necessary for ex vivo MEMRI. Materials and Methods T1 measurements and T1-weighted MRI were performed on MnCl2-administered mice. The mice were then euthanized and the brains were fixed using one of two brain tissue fixation methods: aldehyde solution or focused beam microwave irradiation (FBMI). MRI was then performed on the fixed brains. Results T1 values and T 1-weighted signal contrasts were comparable between in vivo and ex vivo scans on aldehyde-fixed brains. FBMI resulted in the loss of Mn 2+ enhancement. Conclusion Aldehyde fixation, not FBMI, maintained in vivo manganese enhancement for ex vivo MEMRI. © 2013 Wiley Periodicals, Inc. Copyright © 2013 Wiley Periodicals, Inc.