Monocular Microscope to CT Registration using Pose Estimation of the
  Incus for Augmented Reality Cochlear Implant Surgery
Yike Zhang Eduardo Davalos Dingjie Su Ange Lou Jack H. Noble
For those experiencing severe-to-profound sensorineural hearing loss, the
cochlear implant (CI) is the preferred treatment. Augmented reality (AR) aided
surgery can potentially improve CI procedures and hearing outcomes. Typically,
AR solutions for image-guided surgery rely on optical tracking systems to
register pre-operative planning information to the display so that hidden
anatomy or other important information can be overlayed and co-registered with
the view of the surgical scene. In this paper, our goal is to develop a method
that permits direct 2D-to-3D registration of the microscope video to the
pre-operative Computed Tomography (CT) scan without the need for external
tracking equipment. Our proposed solution involves using surface mapping of a
portion of the incus in surgical recordings and determining the pose of this
structure relative to the surgical microscope by performing pose estimation via
the perspective-n-point (PnP) algorithm. This registration can then be applied
to pre-operative segmentations of other anatomy-of-interest, as well as the
planned electrode insertion trajectory to co-register this information for the
AR display. Our results demonstrate the accuracy with an average rotation error
of less than 25 degrees and a translation error of less than 2 mm, 3 mm, and
0.55% for the x, y, and z axes, respectively. Our proposed method has the
potential to be applicable and generalized to other surgical procedures while
only needing a monocular microscope during intra-operation.