  In order to improve realism in middle ear (ME) finite element modeling (FEM),
comprehensive and precise morphological data are needed. To date, micro-scale
X-ray computed tomography (\mu CT) recordings have been used as geometric input
data for FEM models of the ME ossicles. Previously, attempts were made to
obtain this data on ME soft tissue structures as well. However, due to low
X-ray absorption of soft tissue, quality of these images is limited. Another
popular approach is using histological sections as data for 3D models,
delivering high in-plane resolution for the sections, but the technique is
destructive in nature and registration of the sections is difficult. We combine
data from high-resolution \mu CT recordings with data from high-resolution
orthogonal-plane fluorescence optical-sectioning microscopy (OPFOS), both
obtained on the same gerbil specimen. State-of-the-art \mu CT delivers
high-resolution data on the three-dimensional shape of ossicles and other ME
bony structures, while the OPFOS setup generates data of unprecedented quality
both on bone and soft tissue ME structures. Each of these techniques is
tomographic and non-destructive, and delivers sets of automatically aligned
virtual sections. The datasets coming from different techniques need to be
registered with respect to each other. By combining both datasets, we obtain a
complete high-resolution morphological model of all functional components in
the gerbil ME. The resulting three-dimensional model can be readily imported in
FEM software and is made freely available to the research community. In this
paper, we discuss the methods used, present the resulting merged model and
discuss morphological properties of the soft tissue structures, such as muscles
and ligaments.
