Objective To investigate the effects of hippocampal⁃sparing intensity⁃modulated radiotherapy ( IMRT) on dose distribution of target volume and organs at risk ( OARs) in locally advanced nasopharyngeal carcinoma. Methods A retrospective dosimetric analysis was performed among 11 patients with locally advanced nasopharyngeal carcinoma. The MONACO � v5. 10 Treatment Planning System was used to design three treatment plans:routine volumetric modulated arc therapy ( VMAT ) , hippocampal⁃sparing VMAT, and nine fixed⁃fields IMRT. The D98%, D50%, D2%, Dmean , conformity index ( CI ) , and homogeneity index (HI) of planning target volume (PTV) and PTVnx as well as dose distribution of the hippocampus and OARs were evaluated. Using single factor analysis of variance,two group comparative was LSD or paired t⁃test. Results For the above three plans,the D2% values of PTVnx were ,7 513,and 7 462 cGy,respectively (P=0. 016);the D98% values of PTV were 5837,5812,and 5914 cGy,respectively (P=0. 029);the average D2% values of PTV were 7 399,7 380,and 7 333 cGy,respectively ( P=0. 047);the HI values of PTV were 0. 239,0. 241,and 0. 220,respectively (P=0. 016);the V10 values of the brain stem were 97. 2%,88. 1%,and 90. 3%,respectively ( P=0. 001);the V20 values of the brain stem were 74. 2%, 62. 3%,and 67. 1%,respectively ( P=0. 032);the V30 values of the brain stem were 50. 9%,35. 8%,and 45. 5%, respectively ( P= 0. 020 );the V40 values of brain stem were 24. 4%, 14. 4%, and 23. 3%, respectively ( P=0. 018);the Dmean values of hippocampus were 1 518,899,and 896 cGy,respectively ( P=0. 000);the D40% values of hippocampus were 1 379,642,and 639 cGy,respectively ( P=0. 000);the V10 values of the hippocampus were 54. 1%,25. 1%,and 3. 8%,respectively ( P=0. 000);the V20 values of the hippocampus were 26. 2%, 12. 6%, and 12. 0%, respectively ( P=0. 001 ) . Conclusions Hippocampal⁃sparing VMAT and nine fixed⁃fields IMRT can significantly reduce the dose to the hippocampus without affecting dose distribution of target volume and OARs. VMAT may be superior to IMRT because VMAT can simultaneously reduce the dose to the brain stem.%目的：研究局部晚期鼻咽癌保护海马的IMRT计划对靶区及OAR剂量的影响。方法对2015年间的11例局部晚期鼻咽癌患者做回顾性剂量分析研究。 MONACO�5.10TPS设计常规VMAT、保护海马VMAT和9个野IMRT计划。评价PTV及PTVnx的D98％、D50％、D2％、Dmean、CI、HI值及海马和OAR剂量。单因素方差分析，两两比较LSD法或配对t检验。结果常规VMAT、保护海马VMAT、9个野IMRT计划PTVnx的D2％分别为7542、7513、7462 cGy （ P＝0.016）；PTV的D98％分别为5837、5812、5914 cGy （P＝0.029），D2％分别为7399、7380、7333 cGy （P＝0.047），HI 分别为0.239、0.241、0.220（ P＝0.016）；脑干 V10分别为97.2％、88.1％、90.3％（ P＝0.001）， V20分别为74.2％、62.3％、67.1％（ P＝0.032），V30分别为50.9％、35.8％、45.5％（ P＝0.020），V40分别为24.4％、14.75424％、23.3％（ P＝0.018）；海马Dmean分别为1518、899、896 cGy （ P＝0.000），D40％分别为1379、642、639 cGy （P＝0.000），V10分别为54.1％、25.1％、3.8％（P＝0.000），V20分别为26.2％、12.6％、12.0％（ P＝0.001）。结论保护海马的VMAT和9个固定野IMRT比常规VMAT可降低海马剂量，并不影响靶区及OAR剂量分布。保护海马的VMAT计划可同时降低脑干剂量，优势更明显。
展开▼
