The effect of energy selection to the dose distribution of inverse planning intensity-modulated radiation therapy

Abstract

Objective To study the dose distribution of the intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) inverse plans with different energy X-ray, to provide a reference of energy options for radiation therapy. Methods Eight cases with different disease were chosen, the plan for each case were finished with 1Arc (360°) VMAT, 9 fields IMRT and 5 fields IMRT.For each plan project, the energy selections were 4 MV, 6 MV, 8 MV and 15 MV. In the evaluation,homogeneity index ( HI), conformity index ( CI ) and external volume index ( EVI ) of target, the average dose ( Dmean) and 2％ volume in dose volume histogram ( D2 ) of serial organs at risk ( OARs), the average dose ( Dmean ) and a dose level volume ( Vx ) of parallel OARs were chosen and compared . Results Statistical analysis showed that: For the target, the result of HI were F=0. 13,0. 51,0. 09, P=0. 939,0.679,0.965,CI were F=0. 13,0.51,0.09,P=0.939,0.679,0.965, EVI were F=0. 15,0.31,0. 15,P =0. 930,0. 818,0. 931, respectively ; For the OARs of each patient, F ＜ 0. 20, P ＞ 0. 05. All results indicated there was little difference in option of energy for the same field p8roject. Conclusions The results indicate that the middle and low energy X-ray (6 MV or 8 MV) can satisfy the needs of IMRT and VMAT radiotherapy. Compared with middle and low energy, the high energy X-ray (15 MV ) showed little advantage in dose distribution. Key words: Inverse treatment plans; Energy of X-ray; Intensity modulated radiotherapy; Volumetric modulated arc therapy