TIME DELAY EVALUATION AND DOSE REPRODUCIBILITY USING THE VARIAN BREATHING PHANTOM WITH DIFFERENT GATING INTERVALS FROM THE TRUEBEAM STX LINEAR ACCELERATOR

In current radiotherapy the tendency to hypofraction brings the need to increase treatment accuracy and use imaging methods to localize the treatment region. One approach to increasing treatment accuracy is to consider intrafraction movements. The present work analyzes the Time Delay which would be the time between the system detecting that the beam should be turned on / off in the Gating system and the beam actually being turned on / off, the dose reproducibility, if really the planned dose is being delivered to us. defined gating intervals. TrueBeam STx Linear Accelerator (AL) was evaluated using automatic Varian Breathing Phantom (VBP) motion. Time Delay was obtained for both MV images with different energies with and without Flattening Filter (FF) and for images. For reproducibility, direct field planes, Volumetric Modulated Arc Therapy (VMAT – RapidArc ) and dynamic conformational arc with different gating intervals were used. The results were satisfactory, showing that the measured delay is in agreement with the values found in the literature and that the method used is adequate. The dose reproducibility obtained at different gating intervals was also satisfactory. One approach to increase treatment accuracy is to consider intrafraction movements. The present work analyzes the Time Delay which would be the time between the system detecting that the beam should be turned on / off in the Gating system and the beam actually being turned on / off, the dose reproducibility, if really the planned dose is being delivered to us. defined gating intervals. TrueBeam STx Linear Accelerator (AL) was evaluated using the automatic Varian Breathing Phantom (VBP) object movement, using an accessible equipment. Time Delay was obtained for images using different energy MV with and without Flattening Filter (FF) and kV for reproducibility, direct field planes, Volumetric Modulated Arc Therapy (VMAT – RapidArc ) and dynamic conformational arc were used. , with different gating intervals. The results were satisfactory, showing that the measured delay is in agreement with the values found in the literature and that the method used is adequate. The dose reproducibility obtained at different gating intervals was also satisfactory.