Optical Surface Monitoring System Preparation
The DICOM data of the planning CT with skin contour and the isocenter coordinate were sent to the AlignRT workstation. A ROI of the external skin of the treatment area (unstable regions such as axillar were avoided) was selected to serve as the setup reference image. The tolerances were determined for real-time deltas of the on-treatment breath-hold ROI surface to the planned surface as 6-dimensional translation and rotation errors of 3 mm and 3°.