Wissel Tobias, Bruder Ralf, Schweikard Achim, Ernst Floris
Institute for Robotics and Cognitive Systems, University of Luebeck, Ratzeburger Allee 160, 23562 Luebeck, Germany ; Graduate School for Computing in Medicine and Life Sciences, University of Luebeck, Ratzeburger Allee 160, 23562 Luebeck, Germany.
Biomed Opt Express. 2013 Jun 14;4(7):1176-87. doi: 10.1364/BOE.4.001176. Print 2013 Jul 1.
Immobilization and marker-based motion tracking in radiation therapy often cause decreased patient comfort. However, the more comfortable alternative of optical surface tracking is highly inaccurate due to missing point-to-point correspondences between subsequent point clouds as well as elastic deformation of soft tissue. In this study, we present a proof of concept for measuring subcutaneous features with a laser scanner setup focusing on the skin thickness as additional input for high accuracy optical surface tracking. Using Monte-Carlo simulations for multi-layered tissue, we show that informative features can be extracted from the simulated tissue reflection by integrating intensities within concentric ROIs around the laser spot center. Training a regression model with a simulated data set identifies patterns that allow for predicting skin thickness with a root mean square error of down to 18 µm. Different approaches to compensate for varying observation angles were shown to yield errors still below 90 µm. Finally, this initial study provides a very promising proof of concept and encourages research towards a practical prototype.
放射治疗中的固定和基于标记的运动跟踪常常会降低患者的舒适度。然而，光学表面跟踪这种更舒适的替代方法由于后续点云之间缺少点对点对应关系以及软组织的弹性变形而极不准确。在本研究中，我们展示了一种概念验证，即使用激光扫描仪设置测量皮下特征，重点关注皮肤厚度，作为高精度光学表面跟踪的额外输入。通过对多层组织进行蒙特卡洛模拟，我们表明通过在激光光斑中心周围的同心感兴趣区域内积分强度，可以从模拟的组织反射中提取信息特征。用模拟数据集训练回归模型可识别出能够预测皮肤厚度的模式，均方根误差低至18微米。已表明不同的补偿不同观察角度的方法产生的误差仍低于90微米。最后，这项初步研究提供了一个非常有前景的概念验证，并鼓励开展针对实用原型的研究。
