Iyaniwura John E, Elfarnawany Mai, Riyahi-Alam Sadegh, Sharma Manas, Kassam Zahra, Bureau Yves, Parnes Lorne S, Ladak Hanif M, Agrawal Sumit K
*Biomedical Engineering Graduate Program †Department of Otolaryngology-Head and Neck Surgery ‡Department of Medical Imaging §Department of Medical Biophysics ||Department of Electrical and Computer Engineering, Western University, London, Ontario, Canada.
Otol Neurotol. 2017 Jul;38(6):828-832. doi: 10.1097/MAO.0000000000001411.
The cochlear A-value measurement exhibits significant inter- and intraobserver variability, and its accuracy is dependent on the visualization method in clinical computed tomography (CT) images of the cochlea.
An accurate estimate of the cochlear duct length (CDL) can be used to determine electrode choice, and frequency map the cochlea based on the Greenwood equation. Studies have described estimating the CDL using a single A-value measurement, however the observer variability has not been assessed.
Clinical and micro-CT images of 20 cadaveric cochleae were acquired. Four specialists measured A-values on clinical CT images using both standard views and multiplanar reconstructed (MPR) views. Measurements were repeated to assess for intraobserver variability. Observer variabilities were evaluated using intra-class correlation and absolute differences. Accuracy was evaluated by comparison to the gold standard micro-CT images of the same specimens.
Interobserver variability was good (average absolute difference: 0.77 ± 0.42 mm) using standard views and fair (average absolute difference: 0.90 ± 0.31 mm) using MPR views. Intraobserver variability had an average absolute difference of 0.31 ± 0.09 mm for the standard views and 0.38 ± 0.17 mm for the MPR views. MPR view measurements were more accurate than standard views, with average relative errors of 9.5 and 14.5%, respectively.
There was significant observer variability in A-value measurements using both the standard and MPR views. Creating the MPR views increased variability between experts, however MPR views yielded more accurate results. Automated A-value measurement algorithms may help to reduce variability and increase accuracy in the future.
耳蜗A值测量在观察者间和观察者内均表现出显著的变异性，其准确性取决于耳蜗临床计算机断层扫描（CT）图像的可视化方法。
准确估计耳蜗管长度（CDL）可用于确定电极选择，并根据格林伍德方程对耳蜗进行频率映射。已有研究描述了使用单一A值测量来估计CDL，但尚未评估观察者变异性。
获取了20个尸体耳蜗的临床和显微CT图像。四名专家使用标准视图和多平面重建（MPR）视图在临床CT图像上测量A值。重复测量以评估观察者内变异性。使用组内相关性和绝对差异评估观察者变异性。通过与相同标本的金标准显微CT图像进行比较来评估准确性。
使用标准视图时观察者间变异性良好（平均绝对差异：0.77±0.42 mm），使用MPR视图时为中等（平均绝对差异：0.90±0.31 mm）。标准视图的观察者内变异性平均绝对差异为0.31±0.09 mm，MPR视图为0.38±0.17 mm。MPR视图测量比标准视图更准确，平均相对误差分别为9.5%和14.5%。
使用标准视图和MPR视图进行A值测量时，观察者变异性均显著。创建MPR视图增加了专家之间的变异性，然而MPR视图产生了更准确的结果。自动化A值测量算法可能有助于在未来降低变异性并提高准确性。
