Visualization, measurement and modelling of the cochlea using rotating midmodiolar slice planes.

PURPOSE: Cross-sectional visualization of anatomical structures in DICOM viewers is usually presented in parallel slices. For visualizing the inner ear, this concept is unfavourable due to the spiral shape of the cochlea. Radial slicing through its central axis (known as midmodiolar view) is advantageous. Therefore, a custom DICOM viewer was developed, which allows the visualization of the cochlea in a midmodiolar slice plane that rotates around the central axis of the cochlea, always cutting the latter radially.

METHODS: The program was written in C++ using the open-source libraries ITK, VTK, GDCM and Qt. The rotation axis is defined by placing two points in the modiolus within a conventional slice visualization of the dataset. A midmodiolar visualization is calculated based on this axis. Scrolling the mouse wheel rotates slice plane around the axis, displaying midmodiolar slices at variable angles. Measurement options are provided as well as interactive placement of marker points whose coordinates can be exported for post-processing in other programs.

RESULTS: The program can be used in multiple applications including the determination of cochlear dimensions, especially its length, and post-operative positions of cochlear implant (CI) electrode carriers. Computer-aided design models of the cochlea can be generated from exported marker points.

CONCLUSION: The proposed DICOM viewer directly focuses on the needs of cochlear visualization, thus making it a valuable tool in CI related research. The ease of use facilitates future clinical use, e.g. for pre-operative selection of optimal CI electrode carrier length based on the patient's cochlear length.