A novel and adaptable method to prepare samples for postmortem imaging with artifact reduction

Postmortem MRI enables ultra-high-resolution image acquisition and subsequent biomarker validation. This approach requires that postmortem specimens be suspended in solution, which is not required for in vivo MRI. Susceptibility artifacts occur at surface-air interfaces and around air bubbles that remain in and around the sample, leading to image distortions.

We set forth our protocol, the Seven Seals Method, whereby we prepare brain specimens for MRI scanning, with special attention to removing artifact-causing air bubbles. This protocol evolved over twenty years of ex vivo imaging experience. The method uses freezer bags to create a custom-shaped container for brain samples with a temporary reservoir pocket that collects air for removal. The protocol provides step by step instructions with diagrams and videos, a history of experimentation, and a troubleshooting guide.

We have successfully applied this method to whole brains, brain hemispheres and blocked brain specimens, and have prepared samples in a variety of solutions.

The strengths of the Seven Seals Method include its high adaptability for shape and size fit, proven air bubble removal techniques, and inexpensive packing materials that do not require the use of a 3D printer. The tailored container minimizes motion and allows for closer proximity of the specimen to the coil elements than when using hard sided plastic containers, which yields better signal-to-noise ratio for structure visualization.

We anticipate this rigorous protocol will enable other groups to optimize their ex vivo scans for validation studies.