A preliminary study on using reverberant shear wave fields in optical coherence elastography to examine mice brain ex vivo

A number of approaches employ optical coherence tomography (OCT) to obtain the mechanical properties of biological tissue. These are generally referred to as optical coherence elastography (OCE), and have demonstrated promising applications with studies in cornea, breast, muscle, skin, and other soft tissues. A particular application of interest is the brain, in which changes in local and global elastic properties may correlate with the onset and progression of degenerative brain diseases. In this preliminary study, mice brains are studied ex vivo and in situ with preservation of the brain/skull anatomical architecture. A small 6 mm diameter portion of the skull is replaced with a glass cap to allow for OCT imaging. Various permutations of source placement for generating shear waves and modes of excitation are evaluated to optimize the experimental setup. The use of reverberant shear wave fields, which takes advantage of inevitable reflections from boundaries and tissue inhomogeneities, allow for estimation of the shear wave speed, which is directly related to the elastic modulus of soft tissues. Preliminary estimates for the shear wave speed in brains of recently deceased mice are obtained. This study demonstrates potential applications in brain OCE ex vivo and in vivo.