Program Information
OSMS System Accuracy On a Rando Phantom with Open Face Mask
K Xue1 , X Song2 , R Li2 , N Deb2 , T Xue2*, (1) University Of Pennsylvania, Philadelphia, PA, (2) St Luke's University Health Network, Bethlehem, PA,
Presentations
SU-I-GPD-J-44 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: The position accuracy of SRS treatments should be within 1mm. OSMS (VisionRT) system with open face mask has been used for frameless SRS treatments. This is a study of OSMS system accuracy on a Rando phantom with an open face mask over all possible couch and gantry angles.
Methods: OSMS system uses three ceiling mounted camera pods to continuously monitor the patient surface. For SRS treatment, an open face mask is used to immobilize the patient. OSMS system only monitors the open area (ROI). The assumption is that the head of the patient is a rigid body. The accuracy of the OSMS system depends on the size and curvature of the ROI, the LINAC couch and gantry angles, and the isocenter positions. A Rando phantom head with the Q-fix open face mask is used for this study. With the Varian TrueBeam couch and gantry angles set to 0, we monitor the three translational coordinators with offsets from -5 mm to 5 mm and monitor the 3 angle coordinators with offsets from -2 degrees to 2 degrees. We also monitor the coordinator read outs for a subset of 5 gantry angles, 9 couch angles, and three isocenter positions.
Results: With the couch and gantry angles at 0 degrees, the OSMS accuracy is always better than 0.5mm/0.5 degree. Considering all of the gantry angles and couch angles, and three isocenter positions, the maximum translation error is 0.81 mm, and the maximum angle error is 0.5 degrees. The maximum translation error was 1.55 mm with the first VisionRT calibration board we received.
Conclusion: The OSMS system is accurate enough for frameless SRS treatments. Commissioning and routine quality assurance tests should be performed to make sure the OSMS system functions properly.
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