The research of IMRT plan optimization on dose limitation of sub regional auditory organ / 中华放射肿瘤学杂志

Objective To investigate the effects of reducing the auditory organ dose by limitation of sub regional auditory organ in IMRT plan. Methods Total 223 cases of nasopharyngeal carcinoma patients were divided into group A and group B. In group A, the IMRT plans of 114 patients were designed by limiting overall auditory organ dose. In group B, the IMRT plans of 109 patients were designed by limiting sub regional auditory organ dose. According to the Clinical prescription, the IMRT plans were designed. Paried t?test was difference between groups. Results By comparing the two groups of auditory organ dose, in all stages, the tympanic cavity Dmean average in group B decreased by T1 vs. 17?? 7%,T2 vs. 22?? 4%,T3 vs. 15?? 7% and T4 vs. 14?? 2% ( P= 0?? 000,0?? 000,0?? 000,0?? 000);cochlea Dmean average decreased by T1 vs. 11?? 0%, T2 vs. 20?? 1%, T3 vs. 10?? 0% and T4 vs. 9?? 0%(P= 0?? 004,0?? 000,0?? 007,0?? 036);vestibule Dmean average decreased by T1 vs. 22?? 6%, T2 vs. 31?? 8%, T3 vs. 20?? 6% and T4 vs. 21?? 4%, significantly less than in group A (P= 0?? 000,0?? 000,0?? 000,0?? 000). The bony portion of eustachian tube Dmean average in group B decreased were not significantly less than in group A (decreased by 3?? 4%,6?? 8%,3?? 6%,0?? 1%;P= 0?? 291, 0?? 006,0?? 155,0?? 963). Conclusions In IMRT plan, optimization on dose limitation of sub regional auditory organs were used to reduce the auditory organ dose and decrease the radiation damage to auditory organ.

Effects of dose limitation and increased protective weight on dose distribution in auditory organs during intensity-modulated radiotherapy for nasopharyngeal carcinoma / 中华放射肿瘤学杂志

Objective To investigate the protective effects of reducing average radiation dose and increasing protective weight on the auditory system (tympanic cavity,the bony portion of eustachian tube,vestibule,and cochlea) during intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC).Methods The planning system (ADAC Pinnacle3 8.0m) with direct machine parameter optimization was used to optimize the IMRT planning for 40 patients with NPC (stage Ⅰ + Ⅱ:20 patients ;stage Ⅲ + Ⅳ:20 patients).Without reducing the radiation dose for target volume,the IMRT planning was optimized by limiting the average dose administered to the auditory system or increasing the protective weight for the protected organs in auditory system.The protective effects were assessed by analyzing the average dose received by the auditory system.Results After limiting the average dose administered to the auditory system without reducing the radiation dose for target volume,the average dose received by the auditory system was significantly reduced (3855.5-5391.3 Gy vs 2960.3-4559.6 Gy,P =0.000 for all) ; when the protective weight for the auditory system was increased,the average dose received by the auditory system was even more reduced (3855.5-5391.3 Gy vs 2725.4-4271.4 Gy,P =0.000 for all).For all three regimens,the average dose was significantly higher in stage Ⅲ + Ⅳ patients than in stage Ⅰ + Ⅱ patients (P =0.000 for all).Conclusions For the IMRT planning for NPC,limiting the average dose administered to the auditory system can greatly reduce the average dose received by the auditory system,and increasing the protective weight for the auditory system can further reduce the average dose received by the auditory system.However,the protective effect on the auditory system may be reduced as the stage of NPC increases.