Intervention Planning and Anatomical Training for Cochlear Implants: Cochlear Implant Wizard

The Challenge

A cochlear implant (CI) is an electronic hearing aid, which is surgically implanted into the human inner ear (lat. cochlea) in order to restore the hearing capabilities.

As the surgical field contains high-risk structures such as the facial nerve and the tympanic chord and is furthermore characterized by a limited intra-operative visibility, Computed Tomography (CT) scans depicting all anatomical structures are routinely made before each intervention. These scans provide detailed overview information of the middle and inner ear and are used by the surgeons to plan their access strategy to the anatomy of a specific patient.

Our Solution: CI-Wizard

In order to support surgeons to plan the individual intervention based on the available CT data, the “CI-Wizard“ has been implemented. The “CI-Wizard“ is a novel software-tool for the interactive assessment of CT scans of the human ear.

With a tight user guidance and clear instructions in the “CI-Wizard“, a physician can segment multiple structures of the ear in approximately 15 minutes. During the process the user is guided through the patient's anatomy and provided with a deeper understanding of the individual patient´s anatomy. The orthogonal slice views of the CT datasets used for planning have been enriched by an intuitive segmentation process as well as various 3D views of the anatomical structures.

The “CI-Wizard“ easily guides medical experts without technical background through a segmentation of different ear structures for cochlear implant planning. Segmentation is encapsulated in an easy-to-use software, resulting in an efficient workflow for cochlear implant planning.

The Process

CI-Wizard Anatomical Structures
© Fraunhofer IIS
CI-Wizard Anatomical Structures

The “CI-Wizard“ encapsulates complex image processing methods in efficient segmentation corrections, formulated in medical language. Most anatomical structures in the inner and middle ear are embedded in bony tissue. Therefore, inter-patient variations in shape, relative position and volume of structures are limited. This knowledge is used in the “CI-Wizard“ to restrict the search space for segmentation parameters and speed up the segmentation process.

The “CI-Wizard“ deals with the anatomical structures step by step and segments the following structures:

  • Acoustic Canal: Overview Structure, also boundary to anterior. Risk structure, as the bony boundary to the acoustic canal needs to be preserved
  • Ossicles: Incus and Malleus are segmented together as the ossicles. In most cases the stapes is not displayed in the data. Short crus of malleus directs to the facial nerve
  • Tympanic Cavity: Overview structure
  • Facial Nerve: Main risk structure, hurting it leads to facial paralysis
  • Tympanic chord (of facial nerve): Risk structure, hurting it leads to loss of taste. Together with the facial nerve, forms the chorda facial angle, which restricts access and insertion angle of the cochlear implant
  • Round window: Target structure, through a small incision the CI in inserted into the cochlea. From the tympanic cavity the tympanic sinus leads to the round window, it is surrounded by bony tissue that is removed during surgery.
  • Cochlea: Target structure which determines the insertion angle of the CI (angle of first coil of the cochlea)
  • Semicircular canals: Overview structures that enhances orientation due to their distinctive shape

The Benefits

“CI-Wizard“ standardizes intervention planning for cochlear implantations. “CI-Wizard“ prepares surgeons for the patient specific anatomy and patient specific risks, in order to reduce time in the operation room and to reduce risks during CI intervention. “CI-Wizard“ trains medical personnel on ear anatomy in CT images.

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