基于EBCT皮肤剂量在均整和非均整模式头颈部肿瘤放疗中的剂量学研究

Dosimetric study of skin dose in flattened and flattening filter-free radiotherapy based on EBCT in head and neck neoplasms patients

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[6485.90(73.85)cGy vs 6343.35(61.63)cGy,P=0.001]和[6483.90(56.88)cGy vs 6355.15(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5960.00(863.98)cGy vs 5794.95(575.70)cGy和5944.85(625.22)cGy vs 5863.50(557.05)cGy;但VMAT皮肤Dmean和V30值均低于IMRT,皮肤Dmean值分别为[2000.60(853.20)cGy vs 2073.70(792.60)cGy,P=0.046]和[2023.05(830.08)cGy vs 2094.80(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[3813.10(193.90)cGy vs 3710.15(127.22)cGy,P=0.007]和[3862.70(132.88)cGy vs 3715.95(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。

Objective To study the dosimetric differences of skin dose in head and neck between 6MV X-ray fixed field intensity modulated(IMRT)and volumetric modulated arc therapy(VAMT)combined with/without flattening filter mode,respectively.Methods Totally 15head and neck neoplasms patients who received radiotherapy from July 3,2019to November 29,2022in Qingdao Municipal Hospital were selected.Contracting 3mm from the Body structure,and then a new structure with a thickness of 3mm,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 15patients CT images,four types of treatment plans were formulated by combining Body Structure Expansion Technique(EBCT),namely IMRT-FF,IMRT-FFF,VMAT-FF and VMAT-FFF,respectively,totally 60plans.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 Dmaxof PTV,VMAT was higher than IMRT,which were[6485.90(73.85)cGy vs 6343.35(61.63)cGy,P=0.001]and[6483.90(56.88)cGy vs 6355.15(35.55)cGy,P=0.002],respectively.The V100of 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 Dmaxof skin,VMAT was higher than IMRT,with values of 5960.00(863.98)cGy vs 5794.95(575.70)cGy and 5944.85(625.22)cGy vs 5863.50(557.05)cGy,respectively.However,the Dmeanand V30of skin,VMAT was lower than IMRT,the skin Dmeanwere[2000.60(853.20)cGy vs 2073.70(792.60)cGy,P=0.046]and[2022.05(830.08)cGy vs 2094.80(789.73)cGy,P=0.004],respectively.And the skin V30were[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 Dmaxof spinal cord,VMAT was higher than IMRT,which were[3813.10(193.90)cGy vs 3710.15(127.22)cGy,P=0.007]and[3862.70(132.88)cGy vs 3715.95(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 VMATFFF 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 V30of skin.