Visualization and manual segmentation of the post-mortem human amygdala subnuclei using ultra high field magnetic resonance imaging
Abstract
The human amygdala is composed of 13 functionally and anatomically distinct subnuclei. Because most nuclei are difficult to distinguish at the microanatomical level, they are also challenging to discern macroscopically. In low field strength magnetic resonance imaging (MRI) studies, the amygdala can be identified only in its entirety. Higher resolution scans can be acquired by employing ultra-high field strength MRI acquisition techniques. We present a step-by-step guide for the manual segmentation of the amygdala subnuclei at ultra-high field 9.4T MRI. Post-mortem human brain specimen amygdala prosections fit for the 9.4T MRI bore allowed for the collection of high resolution T2-weighted images and visualization of all subnuclei. Intra and inter-rater reliability results suggest this yields a precise protocol leading to greater amygdala subnuclei labelling accuracy applicable for future research investigating substructure functions. The aforementioned ex-vivo neuroimaging methodologies can be implemented in the investigation of other subcortical brain structures.