Real-time intracochlear imaging of automated cochlear implant insertions in whole decalcified cadaver cochleas using ultrasound

Objectives: This study aimed to determine the feasibility of combining high-frequency ultrasound imaging, automated insertion, and force sensing to yield more information about cochlear implant insertion dynamics. Methods: An apparatus was developed combining these aspects along with software to control implant and imaging probe positions. Decalcified unfixed human cochleas were implanted at various speeds, insertion sites, and implant models while imaging near the implant tip throughout insertion and recording force data from the cochlea mounting stage. Ultrasound video data were also captured. Results: The basilar membrane (BM) was frequently penetrated by the implant in either the mid-basal or lower middle turn. Measurements were also performed of apical BM motion in response to upstream implant movement at varying insertion speeds. Increasing insertion speed resulted in greater BM displacement. Discussion: Multiple insertions per cochlea increase the volume of data per specimen while also reducing variability due to differences between cochleas. However, to image inside the cochlea with ultrasound, the bone had to be decalcified, which likely had a significant effect upon the response of tissue to contact by the implant. As calcified bone strongly reflects ultrasound, we also found ultrasound imaging to be an excellent method for easily assessing bone decalcification progress. Conclusion: This technique may be very useful for some studies, although the confounding effects of bone decalcification may make results of other studies too difficult to generalize. The approach could be adapted to other real-time imaging modalities, such as optical coherence tomography.

研究目标：本研究旨在探究结合高频超声成像（high-frequency ultrasound imaging）、自动植入技术与力传感（force sensing）技术，以获取更多关于人工耳蜗植入（cochlear implant）过程动力学特性信息的可行性。
研究方法：本研究研发了一套集成上述技术的实验装置，并配套控制软件以调节植入体与成像探头的位置。实验采用脱钙未固定的人耳蜗标本，在不同植入速度、植入位点及植入体型号条件下开展植入实验，于植入全程对植入体尖端附近区域进行成像，并记录来自耳蜗安装台的力数据，同时采集超声视频数据。
研究结果：植入体常于中底回或中下部回穿透基底膜（basilar membrane，BM）。本研究同时测量了不同植入速度下，上游植入体运动引发的顶区基底膜运动情况，结果显示植入速度越高，基底膜位移量越大。
讨论分析：单耳蜗多次植入可提升每个标本的数据采集量，同时降低因耳蜗个体差异带来的实验变异。但需注意，若要通过超声对耳蜗内部进行成像，需对骨质进行脱钙处理，该处理可能会显著改变组织对植入体接触的响应特性。由于钙化骨质可强烈反射超声信号，本研究同时发现超声成像是一种可便捷评估骨质脱钙进程的优异方法。
研究结论：本研究采用的技术方案对部分研究场景具有较高应用价值，但骨质脱钙带来的混杂效应可能使得部分研究结果难以推广至实际应用场景。该方案还可适配其他实时成像模态，例如光学相干断层成像（optical coherence tomography）。