Liu Xinmin, Alexander Daniel, Kayser Daniel, Speck Thomas, Wiersma Rodney D
Department of Radiation Oncology, UCLA, Los Angeles, California, USA.
Department of Radiation Oncology, University of Pennsylvania, Philadelphia, USA.
J Appl Clin Med Phys. 2025 Jul;26(7):e70138. doi: 10.1002/acm2.70138.
Optical 3D surface imaging is a technique that reconstructs a patient's surface without requiring external markers. This study aimed to evaluate the static and dynamic accuracy, as well as performance under varying conditions, including changes in skin surface color, ambient room lighting, and the size of the tracked region of interest (ROI), for a novel surface guided radiation therapy (SGRT) system (LUNA 3D).
The LUNA 3D consisted of three ceiling mounted camera pods, with each pod equipped with a pattern projector and two camera units. Blue 465 nm light projection, combined with narrow bandpass filters and advanced triggering, were used to improve tracking accuracy to surface color and ambient room light variations. GPU processing enabled surface acquisition at high speeds. To investigate static and dynamic accuracy, a 6-degree-of-freedom (6DoF) robot stage was used to move head phantoms to known positions in 6D space. A 6D infrared (IR) tracking camera was employed as a secondary verification tool.
When tracking a static head phantom with a clinically relevant ROI, the LUNA 3D demonstrated a translational noise root-mean-sqaured-error (RMSE) of approximately 0.04 mm LAT, 0.06 mm LNG, and 0.04 mm VRT and a rotational noise RMSE of 0.04 pitch, 0.04 roll, and 0.04 yaw. For varying surface colors, ambient light conditions, and ROI sizes, LUNA 3D's performance, when compared to the IR camera, exhibited a maximum difference of 0.14 mm. The measured frame rate remained approximately constant at 12.5 fps for all ROI sizes tested.
The LUNA 3D demonstrated high sub-millimeter and sub-degree tracking accuracy, comparable to or better than that of an IR tracking camera, while exhibiting minimal sensitivity to surface color and ambient lighting conditions. Additionally, it maintained stable and consistent frame rate tracking regardless of the tracked ROI size.
光学三维表面成像技术可在无需外部标记的情况下重建患者体表。本研究旨在评估一种新型表面引导放射治疗（SGRT）系统（LUNA 3D）的静态和动态精度，以及在包括皮肤表面颜色变化、室内环境光照和感兴趣的跟踪区域（ROI）大小改变等不同条件下的性能。
LUNA 3D由三个安装在天花板上的摄像头组件组成，每个组件配备一个图案投影仪和两个摄像头单元。采用465 nm蓝光投影，并结合窄带通滤波器和先进触发技术，以提高对表面颜色和室内环境光变化的跟踪精度。GPU处理实现了高速表面采集。为研究静态和动态精度，使用一个六自由度（6DoF）机器人平台将头部模型移至六维空间中的已知位置。采用一个六维红外（IR）跟踪摄像头作为辅助验证工具。
在跟踪具有临床相关ROI的静态头部模型时，LUNA 3D的横向平移噪声均方根误差（RMSE）约为0.04 mm，纵向为0.06 mm，垂直方向为0.04 mm，旋转噪声RMSE为0.04°俯仰、0.04°滚动和0.04°偏航。对于不同的表面颜色、环境光条件和ROI大小，与IR摄像头相比，LUNA 3D的性能最大差异为0.14 mm。在测试的所有ROI大小下，测得的帧率均保持在约12.5 fps基本恒定。
LUNA 3D表现出高亚毫米和亚度跟踪精度，与IR跟踪摄像头相当或更优，同时对表面颜色和环境光照条件敏感度极低。此外，无论跟踪的ROI大小如何，它都能保持稳定一致的帧率跟踪。
