SPIRAL CT IMAGE DEBLURRING FOR COCHLEAR IMPLANTATION

Cochlear implantation is the standard treatment for profound hearing l ass. Preimplantation and postinplantation spiral computed tomography ( CT) is essential in several key clinical and research aspects. The max imum image resolution with commercial spiral CT scanners is insufficie nt to define clearly anatomical features and implant electrode positio ns in the inner ear. In this paper, we develop an expectation-maximiza tion (EM)-like iterative deblurring algorithm to achieve spiral CT ima ge super-resolution for cochlear implantation, assuming a spatially in variant linear spiral CT system with a three-dimensional (3-D) separab le Gaussian point spread function (PSF), We experimentally validate th e 3-D Gaussian blurring model via phantom measurement and profile fitt ing. The imaging process is further expressed as convolution of an iso tropic 3-D Gaussian PSF and a blurred underlying volumetric image, Und er practical conditions, an oblique reconstructed section is approxima ted as convolution of an isotropic two-dimensional (2-D) Gaussian PSP and the corresponding actual cross section. The spiral CT image deblur ring algorithm is formulated with sieve and resolution kernels for sup pressing noise and edge artifacts. A typical cochlear cross section is used for evaluation, demonstrating a resolution gain up to 30%-40% ac cording to the correlation criterion. Physical phantoms, preimplantati on and postimplantation patients are reconstructed into volumes of 0.1 -mm cubic voxels, The patient images are digitally unwrapped along the central axis of the cochlea and the implanted electrode array respect ively, then oblique sections orthogonal to the central axis formed. Af ter deblurring, representation of structural features is substantially improved in all the cases.