Room: Stars at Night Ballroom 1
Purpose: To determine the mechanical, radiation and imaging isocenters on 3-dimensional room laser coordinate system basis using motion capture cameras (MCC, Bonita B10, VICON, USA) system with an in-house developed phantom named â€˜Eagleâ€™
Methods: The Eagle has two modules. The first module called the Eagle-head is a trapezoid-shaped high-density polyethylene block where four infrared-reflective (IR) markers are attached. After inserting the module into the snout-holder of the proton nozzle, MCC track IR markers and record motion tracks while gantry rotates. By analyzing the data, the gantry mechanical isocenter can be determined in 3-dimensions (3D) nature. The second module called the Eagle-body consisted of three cube blocks determines radiation, imaging, and laser isocenters. Two cubes on which two films are attached with 8.0 cm separation in the y-direction, the z-direction can measure gantry, collimator radiation isocenters in 3D, respectively. The radiation isocenter was determined as the point at which the intersect between gantry, collimator radiation isocenters. A metal bead is embedded in the middle block of the Eagle-body and it indicates the imaging isocenter. A cross-hair are marked on the surface of the three blocks to align with the laser isocenter. Software that automatically registers the mechanical, radiation, imaging isocenter based on the laser isocenters was developed.
Results: The relative difference from the laser isocenter were measured in sub-millimeter unit which are (-0.289, -0.1886, -0.0959), (0.217, 0.836, 0.009), and (0.117, 0.546, 0.103) for mechanical, radiation and imaging isocenter, respectively.
Conclusion: The Eagle together with MCC system is useful for accurate measurement of the three isocenters in 3D nature enhancing the efficacy of quality assurance.
Funding Support, Disclosures, and Conflict of Interest: This research was supported by the National Research Foundation of Korea (2013M2A2A7043507).