14Intra-operative imaging & fluoroscopy
Most insertions are confirmed afterwards by the implant's own objective measures, but some need to be watched as they happen. When the electrically-evoked responses are unreliable — a malformed or ossified cochlea, a revision, a suspected misplacement or tip fold-over — intra-operative plain film or, better, real-time C-arm fluoroscopy lets the surgeon see the array going in and correct it on the spot. It is at its most valuable in the malformed ear, where a wide communication with the internal auditory canal can let the electrode stray out of the cochlea entirely; catching that drift allows a withdrawal and antero-superior reinsertion before the wound is closed. Used with discipline — short bursts, a beam centred on the cochlea — the radiation cost is small. This module covers imaging on the table.
Imaging note
Representative CT and MRI images for this chapter are being added soon. The interactive figures here are original schematic teaching diagrams; to respect copyright we do not reproduce third-party radiographs.
TWhen to image in theatre
Intra-operative plain X-ray or C-arm fluoroscopy confirms placement when objective ECAP measurements are unreliable — malformed or ossified cochleae, revisions, suspected misplacement, or tip fold-over (Objective Measures chapter).[2022]
CReal-time fluoroscopy
Real-time fluoroscopy visualises insertion as it happens, aiding cochleostomy localisation and array trajectory — especially valuable in malformed ears (e.g. common cavity) to avoid IAC insertion and maximise the intracochlear electrode count. In IP3 and Balkany IIIb, where the wide IAC– cochlea communication lets the array migrate, fluoroscopy catches it so the surgeon can withdraw and reinsert antero-superiorly.
CTechnique
The beam is directed in an anti-Stenvers view from beneath the table; narrowing and centring it on the cochlea both magnifies the image and minimises dose. A simple intra-operative AP transorbital plain film confirms scalar entry — advised before leaving the OR when round-window anatomy is ambiguous, particularly for straight arrays.
CRadiation safety
Keep total exposure under 2 Gy (200 rad); modern units deliver <0.1 Gy/min, and a typical cochlear-implant case is 1–3 minutes of short bursts (lens dose ~20% of the skin entrance dose). Lead aprons, thyroid shields and avoiding direct orbital penetration complete the ALARA discipline. Intra-operative imaging is the safety net that turns a difficult insertion into a confirmed one before the patient leaves the table.
What helps in real time?
When is intra-operative fluoroscopy most useful?
What does fluoroscopy allow in a common-cavity malformation?