目的 研究皮肤剂量在头颈部6 MV X射线均整(FF)与非均整(FFF)模式分别联合固定野调强放疗(IMRT)和旋转调强放疗(VAMT)中的剂量学差异.方法 选取青岛市市立医院2019-07-03-2022-11-29收治的15例头颈部肿瘤放疗患者,以身体结构为外界内收3 mm,利用勾画运算方法形成一个厚度为3 mm的新结构,并命名为皮肤结构(SS).结合身体结构外扩技术(EBCT),基于15例患者的CT图像,IMRT与VMAT分别联合FF与FFF模式制定4种放疗计划,分别命名为IMRT-FF、IMRT-FFF、VMAT-FF和VMAT-FFF,共60例计划.通过剂量体积直方图(DVH)统计靶区和危及器官剂量值,进行剂量学比较.结果 在FF与FFF模式下,VMAT靶区Dmax值均高于IMRT,分别为[6 485.90(73.85)cGy vs 6 343.35(61.63)cGy,P=0.001]和[6 483.90(56.88)cGy vs 6 355.15(35.55)cGy,P=0.002];IMRT靶区 V100值均高于 VMAT,分别为[98.26％(0.41％)vs 96.56％(0.85％),P=0.002]和[98.22％(0.20％)vs 96.10％(0.74％),P=0.001].VMAT 靶区 HI 值均高于 IMRT,分别为[0.07(0.01)vs 0.05(0.00),P=0.001]和[0.07(0.01)vs 0.05(0.00),P＜0.001].在 FF 与 FFF 模式下,VMAT 皮肤 Dmax 值均高于 IMRT,分别为 5 960.00(863.98)cGy vs 5 794.95(575.70)cGy 和 5 944.85(625.22)cGy vs 5 863.50(557.05)cGy;但 VMAT 皮肤 Dmean和 V30值均低于 IMRT,皮肤 Dmean值分别为[2 000.60(853.20)cGy vs 2 073.70(792.60)cGy,P=0.046]和[2 023.05(830.08)cGy vs 2 094.80(789.73)cGy,P=0.004];皮肤 V30值分别为[22.44％(14.61％)vs 24.40％(15.60％),P=0.030]和[22.41％(14.78％)vs 25.02％(15.28％),P=0.001].脊髓 Dmax 值 VMAT 均高于 IMRT,分别为[3 813.10(193.90)cGy vs 3 710.15(127.22)cGy,P=0.007]和[3 862.70(132.88)cGy vs 3 715.95(130.75)cGy,P=0.012].结论 4 种放疗计划均可以满足靶区及危及器官的临床剂量要求.VMAT-FF与VMAT-FFF计划质量相当,在靶区各参数方面,IMRT-FF与IMRT-FFF计划较VMAT-FF与VMAT-FFF具有一定剂量学优势;VMAT-FF计划较IMRT-FF计划对控制皮肤平均剂量和V30具有优势.
Dosimetric study of skin dose in flattened and flattening filter-free radiotherapy based on EBCT in head and neck neoplasms patients
Objective To study the dosimetric differences of skin dose in head and neck between 6 MV X-ray fixed field in-tensity modulated(IMRT)and volumetric modulated arc therapy(VAMT)combined with/without flattening filter mode,respectively.Methods Totally 15 head and neck neoplasms patients who received radiotherapy from July 3,2019 to No-vember 29,2022 in Qingdao Municipal Hospital were selected.Contracting 3 mm from the Body structure,and then a new structure with a thickness of 3 mm,which was called skin structure(SS)was formed using the contouring operation method.Fixed field intensity modulated and volumetric modulated arc therapy combined with/without flattening filter,based on the 15 patients CT images,four types of treatment plans were formulated by combining Body Structure Expan-sion Technique(EBCT),namely IMRT-FF,IMRT-FFF,VMAT-FF and VMAT-FFF,respectively,totally 60 plans.The dose volume histograms was used to count the dose of the target area and organs at risk.Results The results showed that in both FF and FFF modes,the Dmax of PTV,VMAT was higher than IMRT,which were[6 485.90(73.85)cGy vs 6 343.35(61.63)cGy,P=0.001]and[6 483.90(56.88)cGy vs 6 355.15(35.55)cGy,P=0.002],respectively.The V100 of PTV,IMRT was higher than VMAT,which were[98.26％(0.41％)vs 96.56％(0.85％),P=0.002]and[98.22％(0.20％)vs 96.10％(0.74％),P=0.001],respectively.The HI of PTV,VMAT was higher than IMRT,which were[0.07(0.01)vs 0.05(0.00),P=0.001]and[0.07(0.01)vs 0.05(0.00),P＜0.001],respectively.In both FF and FFF modes,the Dmax of skin,VMAT was higher than IMRT,with values of 5 960.00(863.98)cGy vs 5 794.95(575.70)cGy and 5 944.85(625.22)cGy vs 5 863.50(557.05)cGy,respectively.However,the Dmean and V30 of skin,VMAT was lower than IMRT,the skin Dmean were[2 000.60(853.20)cGy vs 2 073.70(792.60)cGy,P=0.046]and[2 022.05(830.08)cGy vs 2 094.80(789.73)cGy,P=0.004],respectively.And the skin V30 were[22.44％(14.61％)vs 24.40％(15.60％),P=0.030]and[22.41％(14.78％)vs 25.02％(15.28％),P=0.001],respectively.The Dmax of spinal cord,VMAT was higher than IMRT,which were[3 813.10(193.90)cGy vs 3 710.15(127.22)cGy,P=0.007]and[3 862.70(132.88)cGy vs 3 715.95(130.75)cGy,P=0.012],respectively.Conclusions The target and organs at risk dose of all four radiotherapy plans can meet the clinical dose requirements.The quality of VMAT-FF and VMAT-FFF plans is equivalent,however,in terms of various parameters of the target,the IMRT-FF and IMRT-FFF plans have certain dosimetric advantages compared to VMAT-FF and VMAT-FFF.The VMAT-FF has significant advantages over the IMRT-FF in controlling average dose and V30 of skin.
head and neck neoplasmsskin doseradiotherapyuniform modefixed field intensity-modulated radiothera-pyrotational intensity-modulated radiotherapy
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