Automatic planning of a safe drilling path to be used in cochlear implantation surgery using image registration techniques

Abstract

The procedure currently used for cochlear implantation can be improved with the aid of techniques developed in medical imaging. A suitable path accessing the cochlea can be determined before the operation by locating a point in the facial recess and another point in the basal turn of the cochlear on the CT image of the patient’s ear. Outlines of those two structures are drawn by a qualified surgeon creating an atlas that is used to identify the same structures in the patients’ ears. By registering the atlas image to the patient image and tracking the deformations applied to the labeled voxels in the atlas, the location of those structures can be determined. A 12 parameter affine registration is performed first using mutual information as a similarity measure. After that a non rigid registration algorithm (Adaptive Bases Algorithm) is applied to register the ear in the atlas to the patient’s ear. The structures outlined in the atlas are deformed using the computed transformations and the resulting intensity centroids are used to draw the required safe path. The developed algorithm succeeded in finding a suitable path in all of the nine ears it was tested on.