Application of Simulator for position calibration in conformal and IMRT of head and neck cancer

Objective:To evaluate the value of position verification in intensity modulated radiation therapy (IMRT) by utilizing simulators in head and neck cancer.Methods:Thirty-six cases with head and neck cancer treated with intensity modulated radiotherapy were taken calibration films using simulator for position calibration,and then taken verification films in the same position on the accelerator chipbefore radiotherapy.Select the typical signs of bone as a reference point for comparison,we analyzed the displacement of iso centers of simulator and accelerator chipcalibration and verification films and the digitally reconstructed images from pinnacle3 treatment system in X axis,Y axis,Z axis.Results:Thirty-six patients with head and neck intensity modulated radiation therapy film Xaxis calibration(left),Y-axis(first leg),Z-axis(front) of the average error was(0.72 0.57),(0.41 0.41),(0.86 0.65)mm;accelerator verification films X-axis,Y axis,Z-axis the average error was(0.77 0.58),(0.49 0.44),(0.84 0.62) mm,the difference between two sets did not statistically significant(P＞0.05).Conclusions:The simulator for position calibration can reduce the positioning error in positioning is an effective and convenient location verification.