Department of Otorhinolaryngology, Head and Neck Surgery "Otto Körner", Rostock University Medical Center, Doberaner Strasse 137-139, D-18057, Rostock, Germany.
MED-EL, Fürstenweg 77a, A-6020, Innsbruck, Austria.
Eur Radiol. 2022 Feb;32(2):1014-1023. doi: 10.1007/s00330-021-08189-x. Epub 2021 Aug 31.
Knowledge about cochlear duct length (CDL) may assist electrode choice in cochlear implantation (CI). However, no gold standard for clinical applicable estimation of CDL exists. The aim of this study is (1) to determine the most reliable radiological imaging method and imaging processing software for measuring CDL from clinical routine imaging and (2) to accurately predict the insertion depth of the CI electrode.
Twenty human temporal bones were examined using different sectional imaging techniques (high-resolution computed tomography [HRCT] and cone beam computed tomography [CBCT]). CDL was measured using three methods: length estimation using (1) a dedicated preclinical 3D reconstruction software, (2) the established A-value method, and (3) a clinically approved otosurgical planning software. Temporal bones were implanted with a 31.5-mm CI electrode and measurements were compared to a reference based on the CI electrode insertion angle measured by radiographs in Stenvers projection (CDL).
A mean cochlear coverage of 74% (SD 7.4%) was found. The CDL showed significant differences to each other method (p < 0.001). The strongest correlation to the CDL was found for the otosurgical planning software-based method obtained from HRCT (CDL; r = 0.87, p < 0.001) and from CBCT (CDL; r = 0.76, p < 0.001). Overall, CDL was underestimated by each applied method. The inter-rater reliability was fair for the CDL estimation based on 3D reconstruction from CBCT (CDL; intra-class correlation coefficient [ICC] = 0.43), good for CDL estimation based on 3D reconstruction from HRCT (CDL; ICC = 0.71), poor for CDL estimation based on the A-value method from HRCT (CDL; ICC = 0.29), and excellent for CDL estimation based on the A-value method from CBCT (CDL; ICC = 0.87) as well as for the CDL (ICC = 0.94), CDL (ICC = 0.94) and CDL (ICC = 0.87).
All approaches would have led to an electrode choice of rather too short electrodes. Concerning treatment decisions based on CDL measurements, the otosurgical planning software-based method has to be recommended. The best inter-rater reliability was found for CDL, for CDL, for CDL, and for CDL.
• Clinically applicable calculations using high-resolution CT and cone beam CT underestimate the cochlear size. • Ten percent of cochlear duct length need to be added to current calculations in order to predict the postoperative CI electrode position. • The clinically approved otosurgical planning software-based method software is the most suitable to estimate the cochlear duct length and shows an excellent inter-rater reliability.
了解耳蜗管长度（CDL）有助于在人工耳蜗植入（CI）中选择电极。然而，目前还没有临床适用的 CDL 估计的金标准。本研究的目的是（1）确定最可靠的影像学方法和影像学处理软件，用于从临床常规影像学中测量 CDL；（2）准确预测 CI 电极的插入深度。
对 20 个人类颞骨进行了不同的截面成像技术（高分辨率计算机断层扫描[HRCT]和锥形束计算机断层扫描[CBCT]）检查。使用三种方法测量 CDL：（1）使用专用的临床前 3D 重建软件，（2）采用已建立的 A 值方法，（3）使用临床认可的耳科手术规划软件进行长度估计。将 31.5mm 的 CI 电极植入颞骨，并根据 Stenvers 投影中通过 X 光片测量的 CI 电极插入角度（CDL）进行比较。
发现耳蜗覆盖率平均为 74%（SD 7.4%）。CDL 与每种其他方法均存在显著差异（p < 0.001）。从 HRCT 获得的基于耳科手术规划软件的方法（CDL；r = 0.87，p < 0.001）和从 CBCT 获得的方法与 CDL 相关性最强（CDL；r = 0.76，p < 0.001）。总体而言，每种应用方法均低估了 CDL。基于 CBCT 的 3D 重建的 CDL 估计的组内相关系数（ICC）为 0.43，具有适度的可靠性；基于 HRCT 的 3D 重建的 CDL 估计的 ICC 为 0.71，具有良好的可靠性；基于 HRCT 的 A 值方法的 CDL 估计的 ICC 为 0.29，可靠性较差；基于 CBCT 的 A 值方法的 CDL 估计的 ICC 为 0.87，可靠性极佳；基于 CBCT 的 A 值方法的 CDL 估计的 ICC 为 0.94，以及 CDL 估计的 ICC 为 0.94，均具有极好的可靠性。
所有方法都可能导致电极选择偏短。关于基于 CDL 测量的治疗决策，建议使用基于耳科手术规划软件的方法。CDL、CDL、CDL 和 CDL 的组内相关系数最高。
使用高分辨率 CT 和锥形束 CT 进行临床适用的计算会低估耳蜗的大小。
为了预测术后 CI 电极位置，需要将当前计算中的 10%的耳蜗管长度添加到计算中。
基于临床认可的耳科手术规划软件的方法是最适合估计耳蜗管长度的方法，并且具有极好的组内可靠性。
