Three-dimensional strain fields in human brain resulting from formalin fixation.

Before investigating human brains post mortem, the first preparation step is often formalin fixation of the brain. As the brain consists of inhomogeneous tissues, the fixation leads to a three-dimensional strain field within the tissue. During the single case MR-based investigation of the brain, first, the starting point with the brain post mortem but still within the cranium, was examined. Then 13 MR data sets were acquired over a fixation period of 70 days and compared to the initial data set. Based on affine registration of the data sets, the global volume shrinkage was found to be 8.1%. By means of a non-rigid registration additional maximal local volume strains of 32% were determined.