Dose Verification Model for Intensity Modulated Radiotherapy

Objective To establish one two-parameter exponential model to verify dose of intensity modulated radiotherapy(IMRT),and ensure the accurateness IMRT treatment plan.Methods Percentage Depth Dose(PDD) and relative output factor of 6 MV X-ray were measured in Siemens Primus linear accelerator.According to CT imaging of patient obtained by the CT simulator,IMRT treatment plans were designed by TPS and planted in phantom.Dose distribution of phantom central points was gotten;Dose in the center axis was measured by the Capintec 0.65cc PR-06C Farmer ionization chamber,which was compared with the predicted dose by the model and treatment planning system prediction.Results The average difference between model's prediction and treatment planning system prediction was found to be less than 3.0%,which agreed with a target dose uniformity lower than 5% recommended by ICRU Report No.24.Conclusion The model is shown to provide a reliable independent check of planning system monitor units of IMRT.