Room: AAPM ePoster Library
Purpose: To Determine the Effect of Gantry and Couch Angles on Patient Position Obtained with an Optical Surface Monitoring System (OSMS) Equipped with the Advanced Camera Calibration Feature.
Methods: The EDGE® Frameless stereotactic radiosurgery (SRS) delivery system utilizes a dedicated OSMS for patient positioning and monitoring during treatment. The effect of gantry and couch angles on OSMS monitoring accuracy was studied with an anthropomorphic head Phantom. The phantom was placed on the treatment unit’s couch and then centered at the treatment isocenter by moving the couch, with the gantry and couch both at 0 degrees. The phantom surface was captured then for use as a reference surface. The couch was then moved to a series of couch angles, and for each couch angle the phantom position as obtained by the OSMS system was recorded. With the couch at each of a series of angles the gantry was moved through an arc of about 90 degrees starting at 0 degree. For each arc the maximum deviation of the reported phantom position from the position at a gantry angle of 0 was recorded.
Results: With the gantry at zero and couch moving the maximum deviations for the vert, long, and lateral directions were respectively: 0.2mm, 0.4mm, and -0.2mm, and the maximum deviations for the Rotation, Roll, and Pitch were, respectively: 0.1, -0.2, and -0.3 degrees. With the couch at a fixed angle and the gantry angles varied, the maximum deviation for the LONG was: 0.2mm, obtained at the 0 degree couch angle; 0.3mm obtained at 270, 45, and 90 degrees; and 0.1mm obtained at 15 degrees.
Conclusion: The position of the gantry angle has minimal effect on the position of the phantom obtained through OSMS with the Advanced Camera Calibration. The observed effect from couch rotation could partly arise from couch walkout.
Not Applicable / None Entered.