Precise evaluation of the postoperative cochlear duct length by flat-panel volume computed tomography - Application of secondary reconstructions

Objective There is still a lack in precise postoperative evaluation of the cochlea because of strong artifacts. This study aimed to improve accuracy of postoperative two-turn (2TL) and cochlear duct length (CDL) measurements by applying flat-panel volume computed tomography (fpVCT), secondary reconstruction (fpVCT(SECO)) and three-dimensional curved multiplanar reconstruction. Methods First, 10 temporal bone specimens with or without electrode were measured in multi-slice computed tomography (MSCT), fpVCT and fpVCT(SECO) and compared to high-resolution micro-CT scans. Later, pre- and postoperative scans of 10 patients were analyzed in a clinical setting. Results Concerning 2TL, no statistically significant difference was observed between implanted fpVCT(SECO) and nonimplanted micro-CT in 10 temporal bone specimens. In contrast, there was a significant discrepancy for CDL (difference: -0.7 mm, P = 0.004). Nevertheless, there were no clinically unacceptable errors (+/- 1.5 mm). These results could be confirmed in a clinical setting. Using fpVCT(SECO), CDL was slightly underestimated postoperatively (difference: -0.5 mm, P = 0.002) but without any clinically unacceptable errors. Conclusion fpVCT(SECO) can be successfully applied for a precise measurement of the cochlear lengths pre- and postoperatively. However, users must be aware of a slight systematic underestimation of CDL postoperatively. These results may help to refine electrode selection and frequency mapping.

Automated summary

The study aimed to improve the accuracy of cochlear measurements postoperatively using fpVCT(SECO) technique. Results showed no significant difference in 2TL measurements, while there was a slight underestimation in CDL postoperatively. These findings can provide guidance for electrode selection and frequency mapping.