Usefulness of Non EPI-DWI-MRI / CT 3D Static Co-registration Prior to Surgery of Cholesteatomas

Cholesteatoma is a destructive and expanding pathologic condition consisting of keratin pearl arising from a squamous epithelium in the middle ear and/or mastoid process. Evolution consists in a destruction of the ossicles as well as their possible spread through the base of the skull into the brain. Surgical treatment is required to prevent infectious or functional complications. A recurrence after surgery occurs in approximately 10% of patients and rarely affects initial site. Surgical treatment is the only care option for recurrent cholesteatoma. Various locations such as surgical approach cavity, mastoid, hypotympanum are seen. Temporal bone CT is performed prior to surgery for added information on bone erosions especially of ossicules, tegmen tympani, facial nerve canal of internal ear. Due high anatomical resolution and complex anatomy, temporal bone CT is usually displayed with Magnetic Resonance Imaging (MRI) in operating room to help surgical guidance . Imaging especially using MRI is the cornerstone for diagnosis in asymptomatic patients. Since 2006, non echo planar imaging (EPI) Diffusion weighted imaging (DWI) Magnetic resonance imaging (MRI) (sequences has shown high accuracy to depict recurrent cholesteatoma. If EPI sequences had a high rate of diffeomorphic atefacts whereas non EPI sequences using either HAlf-Fourier acquisition Single-shot Turbo spin-Echo (HASTE) or Fast-spin-echo demonstrates less magnetic susceptibility artifacts. Multimodality fusion between NonEPI-DWI-MRI and computerized tomography (CT) is a rational promising tool to rise the performance for cholesteatomas delineation. The performances of NonEPI-DWI-MRI in assessing lesion spread and volume are still unknown and needs further investigations. The aim of the study is to assess the DWI-MRI/CT fusion feasibility, reproducibility and the accuracy prior to surgery propectively compared to surgical findings.