The MHI-TM2000 system configuration and its coordinate system. The positive x-axis direction is defined as being from left to right when facing the O-ring gantry. The positive y-axis direction is defined as being toward the O-ring gantry and the positive z-axis direction is defined as being from the floor toward the ceiling. The positive angles are expressed as clockwise rotation.
The cube phantom with a steel ball and acquired images of the phantom: (a) photograph of the cube phantom, (b) MV X-ray image acquired by EPID with a square field (30 × 30 mm), (c) kV X-ray image, and (d) kV-CBCT image.
The appearance of phantom set-up. The IR markers were attached to the anterior surface of the phantom. (a) The rotational and translational changes in phantom position were monitored by IR camera system. (b) The phantom was positioned to the isocenter by alignment of the lasers with the marks on the phantom.
Isocenter accuracy of the MV treatment beam with gantry and ring rotation. The displacement of the center of the steel ball positioned at laser isocenter from the center of the radiation field was determined from the 2D portal images.
The isocenter alignment in the kV X-ray imaging subsystem with gantry and ring rotation. The displacement between the 3D coordinates of the isocenters of MV beam and kV imaging system was calculated.
The geometrical error of the isocenter in the kV-CBCT for each FPD and imaging direction.
The geometrical accuracy of the coordinate axes of the kV X-ray and CBCT images.
Target localization accuracy using the ExacTrac image-fusion software.
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