Gupta Abhishek, Kharbanda Om Prakash, Balachandran Rajiv, Sardana Viren, Kalra Shilpa, Chaurasia Sushma, Sardana Harish Kumar
Academy of Scientific and Innovative Research (AcSIR), CSIR-Central Scientific Instruments Organisation (CSIO) Campus, Chandigarh, India.
Centre for Dental Education and Research; Division of Orthodontics and Dentofacial Deformities, All India Institute of Medical Sciences, New Delhi, India.
Am J Orthod Dentofacial Orthop. 2017 Jan;151(1):118-131. doi: 10.1016/j.ajodo.2016.06.027.
The objective of this study was to evaluate the effect of the orientation of cone-beam computed tomography (CBCT) images on the precision and reliability of 3-dimensional cephalometric landmark identification.
Ten CBCT scans were used for manual landmark identification. Volume-rendered images were oriented by aligning the Frankfort horizontal and transorbital planes horizontally, and the midsagittal plane vertically. A total of 20 CBCT images (10 as-received and 10 oriented) were anonymized, and 3 random sets were generated for manual landmark plotting by 3 expert orthodontists. Twenty-five landmarks were identified for plotting on each anonymized image independently. Hence, a total of 60 images were marked by the orthodontists. After landmark plotting, the randomized samples were decoded and regrouped into as-received and oriented data sets for analysis and comparison. Means and standard deviations of the x-, y-, and z-axis coordinates were calculated for each landmark to measure the central tendency. Intraclass correlation coefficients were calculated to analyze the interobserver reliability of landmark plotting in the 3 axes in both situations. Paired t tests were applied on the mean Euclidean distance computed separately for each landmark to evaluate the effect of 3-dimensional image orientation.
Interobserver reliability (intraclass correlation coefficient, >0.9) was excellent for all 25 landmarks for the x-, y-, and z-axes on both before and after orientation of the images. Paired t test results showed insignificant differences for the orientation of volume-rendered images for all landmarks except 3: R1 left (P = 0.0138), sella (P = 0.0490), and frontozygomatic left (P = 0.0493). Also midline structures such as Bolton and nasion were plotted more consistently or precisely than bilateral structures.
Orientation of the CBCT image does not enhance the precision of landmark plotting if each landmark is defined properly on multiplanar reconstruction slices and rendered images, and the clinician has sufficient training. The consistency of landmark identification is influenced by their anatomic locations on the midline, bilateral, and curved structures.
本研究的目的是评估锥束计算机断层扫描（CBCT）图像的方向对三维头影测量标志点识别的精度和可靠性的影响。
使用十次CBCT扫描进行手动标志点识别。通过将法兰克福水平面和眶平面水平对齐，以及矢状面垂直对齐来对容积再现图像进行定向。总共20幅CBCT图像（10幅原始图像和10幅定向图像）进行匿名处理，并由3位正畸专家生成3组随机图像用于手动标志点绘制。在每幅匿名图像上独立识别25个标志点进行绘制。因此，正畸专家总共标记了60幅图像。标志点绘制完成后，对随机样本进行解码并重新分组为原始图像和定向图像数据集进行分析和比较。计算每个标志点在x、y和z轴坐标的均值和标准差以测量集中趋势。计算组内相关系数以分析两种情况下标志点绘制在三个轴上的观察者间可靠性。对每个标志点分别计算的平均欧几里得距离应用配对t检验，以评估三维图像方向的影响。
在图像定向前后，x、y和z轴上所有25个标志点的观察者间可靠性（组内相关系数，>0.9）均极佳。配对t检验结果显示，除了三个标志点：左侧R1（P = 0.0138）、蝶鞍（P = 0.0490）和左侧额颧点（P = 0.0493）外，容积再现图像的方向对所有标志点均无显著差异。此外，中线结构如Bolton点和鼻根点的绘制比双侧结构更一致或更精确。
如果在多平面重建切片和再现图像上正确定义每个标志点，并且临床医生经过充分培训，CBCT图像的定向不会提高标志点绘制的精度。标志点识别的一致性受其在中线、双侧和弯曲结构上的解剖位置影响。
