Evolving a Radiological Protocol for Cochlear Duct Length Measurement: Three Audit Cycles

To develop an accurate protocol for measuring the Cochlear Duct Length (CDL) by using Multi Detector Computerized Tomography (MDCT) imaging of the temporal bones and thereby make the appropriate choice of electrode for cochlear implantation. 79 MED-EL® Cochlear implantees were divided into three cohorts in chronological order of their implantation. CDL was calculated from MDCT images and correlated with the CDL calculated using the existing Jolly's formula. Results of the CDL measured by unfurling the cochlea correlated well with the existing formula. In addition to CDL measurement, measuring diameter of each turn, especially the apical turn, helped in choosing the appropriate electrode for complete cochlear coverage. Having dedicated radiographers and neuro-radiologists can avoid inter-observer variations in CDL measurements. Measuring the CDL and the diameter of each turn helps in choosing an appropriate electrode thus minimizing intra-operative difficulties and achieving complete safe insertion.