Monaco系统计算网格尺寸对T_(4)期鼻咽癌的剂量学影响

The effects of different dose calculation grid size by Monaco planning system on the dosimetry of T_(4)nasopharyngeal carcinoma

目的分析Monaco系统不同剂量计算网格尺寸对T4期鼻咽癌靶区及靶区周围重要危及器官(OAR)的物理和生物剂量学的影响。方法选取2020年10月至2022年4月在云南省肿瘤医院放疗科进行放疗的18例T4期鼻咽癌患者,在Monaco 5.11.03系统中完成靶区和OAR的勾画,以靶区优先的优化模式在3 mm网格制定容积弧形调强放疗(VMAT)计划;复制3 mm网格组计划,不改变其他的任何参数,分别在1、2、4和5 mm网格重新制定物理计划,再将5个计划归一到处方剂量包绕95%的靶区体积。比较各网格组靶区的计划时间、D_(2%)、D_(50%)、D_(98%)、适形度指数(CI)、均匀性指数(HI)、靶区梯度指数(GI)、计算靶区的肿瘤控制率(TCP)以及靶区周围重要OAR的D2%、Dmean值。结果计划大体肿瘤靶区(PGTVp):1、2、3、4、5 mm组的D2%分别为(76.94±0.66)、(75.98±0.76)、(75.56±0.67)、(75.67±0.73)、(75.94±0.85)Gy,差异有统计学意义(F=9.86,P<0.001);1、2、3、4、5 mm组的CI分别为0.75±0.05、0.78±0.04、0.78±0.05、0.79±0.04、0.78±0.04,差异有统计学意义(F=2.61,P=0.041);各分组间D50%、D98%、HI、等效均匀剂量(EUD)和肿瘤控制率(TCP)的差异均有统计学意义(H=17.14,P=0.002;F=9.35,P<0.001;H=25.43,P<0.001;F=5.85,P<0.001;H=17.65,P=0.001),各分组间GI差异无统计学意义(P>0.05)。两两比较发现,2、3、4、5 mm组D_(2%)与1 mm组相比,5 mm组D50%与2、3 mm组相比,4 mm组D_(98%)与1、2 mm组相比,5 mm组D98%与1、2、3 mm组相比,5 mm组CI与1 mm组相比,2、3、4、5 mm组HI与1 mm组相比,3 mm组EUD与1 mm组相比,5 mm组EUD与2、3 mm组相比,3 mm组TCP与1 mm组相比,5 mm组TCP与3 mm组相比,差异均有统计学意义(均P<0.05)。计划大体肿瘤淋巴结靶区(PGTVn):1、2、3、4、5 mm组的D_(2%)分别为(76.36±0.59)、(75.36±0.62)、(75.04±0.68)、(75.25±0.72)、(75.39±0.77)Gy,差异有统计学意义(F=10.32,P<0.001);1、2、3、4、5 mm组的HI分别为1.08(1.08,1.08)、1.07(1.06,1.07)、1.06(1.06,1.07)、1.06(1.06,1.07)、1.06(1.06,1.08),差异有统计学意义(H=22.00,P<0.001);各分组间D50%、D98%和EUD的差异均有统计学意义(H=11.79,P=0.019;H=20.49,P<0.001;F=12.14,P=0.016);各分组间CI、GI差异均无统计学意义(均P>0.05)。两两比较发现,2、3、4、5 mm组D_(2%)与1 mm组相比,4 mm组D98%与1 mm组相比,5 mm组D98%与1、2 mm组相比,2、3、4 mm组HI与1 mm组相比,3 mm组EUD与1 mm组相比,差异均有统计学意义(均P<0.05)。计划原发肿瘤临床靶区1(PCTVp1):1、2、3、4、5mm组的D_(2%)分别为(76.59±0.63)、(75.64±0.65)、(75.64±0.98)、(75.41±0.70)、(75.71±0.84)Gy,差异有统计学意义(F=9.53,P<0.001);1、2、3、4、5 mm组的D50%分别为(72.09±0.34)、(71.85±0.39)、(71.82±0.45)、(72.04±0.56)、(72.43±0.66)Gy,差异有统计学意义(F=4.20,P=0.019);其余各指标组间差异均无统计学意义(均P>0.05)。两两比较发现,2、3、4、5 mm组D_(2%)与1 mm组相比,5 mm组D_(50%)与2、3 mm组相比,差异均有统计学意义(均P<0.05)。计划淋巴结临床靶区1(PCTVn1):各指标组间差异均无统计学意义(均P>0.05)。计划临床靶区2(PCTV2):1、2、3、4、5 mm组的D2%分别为(75.57±0.50)、(74.87±0.67)、(74.51±0.51)、(74.61±0.63)、(75.00±0.74)Gy,差异有统计学意义(F=8.27,P<0.001);其余指标各组间差异均无统计学意义(均P>0.05)。两两比较发现,2、3、4 mm组D2%与1 mm组相比,差异均有统计学意义(均P<0.05)。1、2、4、5 mm组物理计划计算时间分别为987.00(848.00,1091.00)、120.50(99.75,134.00)、26.00(24.00,34.25)、21.50(18.75,34.75)s,差异有统计学意义(H=61.62,P<0.001),两两比较发现,4 mm组与1、2 mm组,5 mm组与1、2 mm组的计划计算时间相比,差异均有统计学意义(均P<0.05)。靶区周围OAR的剂量学参数各指标组间差异均无统计学意义(均P>0.05)。结论T4期鼻咽癌在制定放疗物理计划时,靶区及靶区周围重要OAR的物理剂量和生物剂量随剂量计算网格尺寸的改变而改变。综合考虑物理计划质量及计算时间,在Monaco系统制定T4期鼻咽癌患者的VMAT计划时,可先在3 mm计算网格进行计划优化,并将计划复制到1 mm计算网格重新计算。

Objective To analyze the effects of different dose calculation grid size of Monaco system on the physical and biological dosimetry of target area and organ at risk(OAR)in T4 nasopharyngeal carcinoma.Methods A total of 18 patients with stage T4 nasopharyngeal carcinoma who received radiotherapy in the Department of Radiotherapy of Yunnan Cancer Hospital from October 2020 to April 2022 were selected to complete the delineation of target areas and OAR in the Monaco 5.11.03 system,and the volumetric intensity modulated arc therapy(VMAT)plan was developed on the 3 mm grid with the optimization mode of target area priority.The 3 mm grid group plan was replicated without changing any other parameters,and the physical plan was re-established on the 1,2,4 and 5 mm grids,and then the five plans were normalized to the prescription dose to cover 95% of the target volume.The planning time,D_(2%),D_(50%),D_(98%),conformity index(CI),homogeneity index(HI),gradient index(GI),tumor control probability(TCP),D_(2%)and Dmean of important OAR around the target area were calculated and statistically analyzed.Results Planning primary tumor gross target volume(PGTVp):The D2% of 1,2,3,4 and 5 mm groups were(76.94±0.66),(75.98±0.76),(75.56±0.67),(75.67±0.73)and(75.94±0.85)Gy,respectively,with a statistically significant difference(F=9.86,P<0.001).The CI of 1,2,3,4 and 5 mm groups were 0.75±0.05,0.78±0.04,0.78±0.05,0.79±0.04 and 0.78±0.04,respectively,with a statistically significant difference(F=2.61,P=0.041).There were statistically significant differences in D_(50%),D_(98%),HI,equivalent uniform dose(EUD)and tumor control probability(TCP)among the groups(H=17.14,P=0.002;F=9.35,P<0.001;H=25.43,P<0.001;F=5.85,P<0.001;H=17.65,P=0.001).There was no statistically significant difference in GI among the groups(P>0.05).Pairwise comparison showed that D2%in 2,3,4,5 mm groups compared with 1 mm group,D50%in 5 mm group compared with 2,3 mm groups,D98%in 4 mm group compared with 1,2 mm groups,D98%in 5 mm group compared with 1,2,3 mm groups,CI in 5 mm group compared with 1 mm group,HI in 2,3,4,5 mm groups compared with 1 mm group,EUD in 3 mm group was compared with 1 mm group,EUD in 5 mm group compared with 2,3 mm groups,TCP in 3 mm group compared with 1 mm group,and TCP in 5 mm group compared with 3 mm group,there were statistically significant differences(all P<0.05).Planning nodal gross target volume(PGTVn):The D_(2%)of 1,2,3,4 and 5 mm groups were(76.36±0.59),(75.36±0.62),(75.04±0.68),(75.25±0.72)and(75.39±0.77)Gy,respectively,with a statistically significant difference(F=10.32,P<0.001).The HI of 1,2,3,4 and 5 mm groups were 1.08(1.08,1.08),1.07(1.06,1.07),1.06(1.06,1.07),1.06(1.06,1.07),1.06(1.06,1.07),1.06(1.06,1.08),respectively,with a statistically significant difference(H=22.00,P<0.001);There were statistically significant differences in D50%,D98% and EUD among the groups(H=11.79,P=0.019;H=20.49,P<0.001;F=12.14,P=0.016).Pairwise comparison showed that there were statistically significant differences in D2%between 2,3,4,5 mm groups and 1 mm group,D98%between 4 mm group and 1 mm group,D98% between 5 mm group and 1,2 mm groups,HI between 2,3,4 mm groups and 1 mm group,and EUD between 3 mm group and 1 mm group(all P<0.05).Planning primary tumor clinical target volume 1(PCTVp1):The D_(2%)of 1,2,3,4 and 5 mm groups were(76.59±0.63),(75.64±0.65),(75.64±0.98),(75.41±0.70)and(75.71±0.84)Gy,respectively,with a statistically significant difference(F=9.53,P<0.001).The D50%of 1,2,3,4,5 mm groups were(72.09±0.34),(71.85±0.39),(71.82±0.45),(72.04±0.56),(72.43±0.66)Gy,respectively,with a statistically significant difference(F=4.20,P=0.019).There was no statistically significant difference in the other indexes among the groups(all P>0.05).Pairwise comparison showed that there were statistically significant differences in D_(2%)between 2,3,4,5 mm groups and 1 mm group,and in D_(50%)between 2,3 mm groups and 1 mm group(all P<0.05).Planning nodal clinical target volume 1(PCTVn1):There were no statistically significant differences in all indexes among the groups(all P>0.05).Planning clinical target volume 2(PCTV2):The D_(2%)of 1,2,3,4 and 5 mm groups were(75.57±0.50),(74.87±0.67),(74.51±0.51),(74.61±0.63)and(75.00±0.74)Gy,respectively,with a statistically significant difference(F=8.27,P<0.001).Pairwise comparison showed that the D_(2%)of the 2,3,4 mm groups were significantly different from that of the 1 mm group(all P<0.05).The calculation time of physical plan in 1,2,4 and 5 mm groups was 987.00(848.00,1091.00),120.50(99.75,134.00),26.00(24.00,34.25)and 21.50(18.75,34.75)s,respectively,with a statistically significant difference(H=61.62,P<0.001).Pairwise comparison showed that there were statistically significant differences in the calculation time between 4 mm group and 1,2 mm groups,5 mm group and 1,2 mm groups(all P<0.05).There was no statistically significant difference in the dosimetric parameters of OAR around the target area among the groups(all P>0.05).Conclusion The physical dose and biological dose of the important OAR around the target area and the target area change with the change of dose calculation grid size when formulating the physical plan of radiotherapy for T4 nasopharyngeal carcinoma.Considering the quality of the physical plan and the calculation time,when the Monaco system formulates the VMAT plan for T4 nasopharyngeal carcinoma patients,the plan can be optimized on the 3 mm computing grid and copied to the 1 mm computing grid for recalculation.