Comparison Between Transimpedance Matrix (TIM) Measurement and X-ray Fluoroscopy for Intraoperative Electrode Array Tip Fold-Over Detection

Abstract

Objective: The aim of this study was to compare Transimpedance Matrix (TIM-) measurement and X-ray fluoroscopy for the intraoperative detection of electrode array tip foldover in cochlear implant recipients. Study design: Retrospective agreement study. Setting: Tertiary referral hospital. Patients: Forty-two patients (47 ears) consecutively implanted with the Slim Modiolar Electrode. Interventions: Five raters, with different levels of clinical experience, individually retrospectively evaluated the TIMheatmaps and X-ray fluoroscopy images of all patients included in this study for electrode array tip fold-over. Main Outcome Measures: Agreement between raters' individual evaluation and the diagnosis given during clinical intraoperative evaluation for both modalities, as well as the inter-method agreement between TIM-measurement and fluoroscopy, and the inter-rater agreement for both modalities. Results: A tip fold-over was found in three of the fortyseven implantations (6.4%) included in this study. The average agreement between raters' evaluation and the intraoperative evaluation was 88% (Cohens k ¼ 0.378) for fluoroscopy and 99% (Cohens k ¼ 0.915) for TIM-measurement. Two raters misdiagnosed at least one tip fold-over as being correctly positioned when evaluating the fluoroscopy images (1/3 and 3/3, respectively). Each of the raters correctly detected all three tip fold-overs using the TIMheatmaps. The inter-rater agreement for fluoroscopy was classified as ''fair'' (Fleiss' k ¼ 0.286), while the inter-rater agreement for TIM-measurement was classified as ''nearperfect'' (Fleiss' k ¼ 0.850). Conclusions: TIM-measurement has a high potential to replace X-ray fluoroscopy for intraoperatively detecting electrode array tip fold-over in cochlear implantation, especially in patients implanted with flexible, precurved arrays.

Detection of Tip Fold‐Over of the Slim Modiolar Electrode Using Intraoperative Mobile Cone‐Beam Computed Tomography

“…Several electrophysiological and imaging tests have been reported to be more effective for detecting electrodes with tip fold‐over. Transimpedance matrix (TIM) measurement 27,28 and spread of excitation (SOE) 21,27 are available using the telemetry functions of the electrodes. The specificities of TIM and SOE were 97.89% and 98.93%, respectively, and the sensitivity of the combination of these 2 modalities was 100% 27 .…”

“…Fluoroscopy has the disadvantage of a high irradiation dose, and its sensitivity is less than that of TIM. 28 Unlike conventional CT, CBCT captures images on a flat panel, which is not only isotropic and advantageous for image reconstruction but also has fewer metal artifacts. Furthermore, CBCT images can determine the insertion depth and position of the cochlear implant electrode array in the cochlea 14,30 and can be used for the detection of electrode tip fold-over.…”

“…CT is a reliable test; however, conventional fan‐beam CT requires a dedicated room, which is not practical for an intraoperative test. Fluoroscopy has the disadvantage of a high irradiation dose, and its sensitivity is less than that of TIM 28 …”

Predictive Value of Transimpedance Matrix Measurements to Detect Electrode Tip Foldover

“…The transimpedance matrix (TIM), available through CustomSound EP (Cochlear Ltd., Sydney, Australia), is a system to measure spread of excitation. In a proof-of-concept study, it was demonstrated to have the potential to accurately detect tip foldovers (11).…”

An optically-guided cochlear implant sheath for real-time monitoring of electrode insertion into the human cochlea

“…Furthermore, studies reported that electrode insertion trauma is often not accompanied by an increased resistance or mechanical forces, making it currently an unreliable parameter for insertion monitoring 25 , 26 . Intraoperative X-ray plain film fluoroscopy and transimpedance matrix measurements can help detect electrode fold-over, but do not prevent it and provide no information on the actual position of the electrode inside the ST with respect to the cochlear walls at risk for trauma 27 . Robotic electrode insertion based on preoperative imaging may reduce the risk of electrode translocation, but the value of the preoperative imaging is limited.…”