Learning Objectives: 1) An introduction to CBCT imaging 2) A review of the relevant literature 3) A proposal of two models of cone beam imaging in cochlear implantation practice 4) To demonstrate these models using high quality images and explanations.
Introduction: Traditional methods of imaging in cochlear implantation practice include pre-operative MRI and high-resolution CT, to examine detailed anatomical structures and to define bony detail respectively, with post-operative modified Stenver's radiography to confirm electrode placement.
CBCT offers several potential advantages, including reduced radiation dose and minimal metal artefact compared to standard CT scanning. Additionally, there is evidence that electrode position may influence auditory outcome, hence the superior anatomical detail in CBCT offers a distinct advantage over plain radiography.
Methods: A review of the literature, and a summary of the potential uses of CBCT in cochlear implantation practice, as well as our department's current practice and experience, are presented.
Results: A number of studies have assessed the potential of cone beam imaging in determining cochlear implant electrode position in human cadaveric temporal bones.
CBCT offers distinct advantage over standard CT in the form of reduced radiation, reduced metal artefact and superior bony anatomical definition. However it is not suitable for use in young children or babies due to the need to sit upright and still.
Conclusions: Two models of CBCT usage in cochlear implantation practice are explained; both are currently being trialled by cochlear implantation units in the UK:
CBCT of the temporal bone both pre- and post-operatively in cochlear implant recipients offers high quality imaging for the assessment of both bony anatomy and electrode placement. MRI scanning is still required pre-operatively in many cases. Young children cannot be reliably imaged using CBCT due to movement artefact.
An alternative use of CBCT is in the pre- and post-operative assessment of selected cochlear implantation patients, including those with complicated pathology or anatomy, in whom a detailed analysis of anatomy and electrode position is advantageous in terms of their management and prognosis.
