An improved method for calibrating the gantry angles of linear accelerators.
Linear particle accelerators (linacs) are widely used in radiotherapy procedures; therefore, accurate calibrations of gantry angles must be performed to prevent the exposure of healthy tissue to excessive radiation. One of the common methods for calibrating these angles is the spirit level method. In this study, a new technique for calibrating the gantry angle of a linear accelerator was examined. A cubic phantom was constructed of Styrofoam with small lead balls, embedded at specific locations in this foam block. Several x-ray images were taken of this phantom at various gantry angles using an electronic portal imaging device on the linac. The deviation of the gantry angles were determined by analyzing the images using a customized computer program written in ImageJ (National Institutes of Health). Gantry angles of 0, 90, 180, and 270 degrees were chosen and the results of both calibration methods were compared for each of these angles. The results revealed that the image method was more precise than the spirit level method. For the image method, the average of the measured values for the selected angles of 0, 90, 180, and 270 degrees were found to be -0.086 ± 0.011, 90.018 ± 0.011, 180.178 ± 0.015, and 269.972 ± 0.006 degrees, respectively. The corresponding average values using the spirit level method were 0.2 ± 0.03, 90.2 ± 0.04, 180.1 ± 0.01, and 269.9 ± 0.05 degrees, respectively. Based on these findings, the new method was shown to be a reliable technique for calibrating the gantry angle.
*Bloomsburg University of Pennsylvania, Department of Physics and Engineering Technology, Hartline Science Center, 400 East 2nd Street, Bloomsburg, PA 17815; †Geisinger Medical Health Center, Radiation Oncology, 100 North Academy Avenue, Danville, PA 17822.
Kyle
K
Higgins
Jared
J
Treas
Andrew
A
Jones
Naz Afarin
NA
Fallahian
David
D
Simpson
D002138:Calibration / Q000592:standards; D006801:Humans; D009369:Neoplasms / Q000532:radiotherapy; D010315:Particle Accelerators / Q000592:standards*; D019047:Phantoms, Imaging; D011878:Radiotherapy / Q000379:methods* / Q000592:standards; D061089:Radiotherapy, Image-Guided / Q000379:methods / Q000592:standards