Flattening filter-free(FFF) beams generated by medical linear particle accelerators(linacs) have recently been used in radiotherapy clinical practice.FFF beams have fundamental physical parameter differences with resp...Flattening filter-free(FFF) beams generated by medical linear particle accelerators(linacs) have recently been used in radiotherapy clinical practice.FFF beams have fundamental physical parameter differences with respect to standard flattening filter(FF) beams,such that the generally used dosimetric parameters and definitions are not always viable.This study investigates dosimetric parameters for use in the quality assurance of FFF beams generated by medical linacs in radiotherapy.The main characteristics of the photon beams are analyzed using specific data generated by a Varian True Beam linac having both FFF and FF beams of 6 and 10 MV(megavolt) energy,respectively.Definitions for dose profile parameters are suggested,starting from the renormalization of the FFF with respect to the corresponding FF beam.From this point,the flatness concept is translated into one of "un-flatness",and other definitions are proposed,maintaining a strict parallelism between FFF and FF parameter concepts.The quality controls used in establishing a quality assurance program when introducing FFF beams into the clinical environment are given,maintaining similarity to those used for standard FF beams,and recommendations for the introduction of FFF beams into clinical radiotherapy application for breast cancer patients are provided as an example for comparison between FFF and FF for dose distribution and coverage for a target volume.Although there are many advantages of using a FFF beam,especially for advanced radiotherapy techniques,there are a few limitations(e.g.,using a relatively higher energy photon beam for stereotactic radiotherapy(SRT),limited speed of current multileaf collimators(MLCs),and off-axis distance-dependent modulation in intensitymodulated radiation therapy(IMRT)) as well as challenges(e.g.,criteria for beam quality evaluation and penumbra,establishment of dosimetry methods,and consequences of photon target burn-up) that need to be addressed for establishing the FFF beam as a viable alternative to the FF beam.展开更多
Objective The aim of the study was to compare flattening filter-free(FFF) beams and conventional flattening filter(FF) beams in volumetric modulated arc therapy(VMAT) for cervical cancer after surgery, through a retro...Objective The aim of the study was to compare flattening filter-free(FFF) beams and conventional flattening filter(FF) beams in volumetric modulated arc therapy(VMAT) for cervical cancer after surgery, through a retrospective planning study.Methods VMAT plans of FFF beams and normal FF beams were designed for a cohort of 15 patients. The prescribed dose was 45 Gy to 1.8 Gy per fraction, and at least 95% of the planning target volume received this dose. Doses were computed with a commercially available treatment planning system using a Monte Carlo(MC) algorithm. Plans were compared according to dose-volume histogram analysis in terms of planning target volume homogeneity and conformity indices(HI and CI), as well as organs at risk(OAR) dose and volume parameters. Results FFF-VMAT was similar to FF-VMAT in terms of CI, but inferior to FF-VMAT considering HI. No statistically differences were observed between FFF-VMAT and FF-VMAT in following organ at risks including pelvic bone marrow, small bowel, bladder, rectum, and normal tissue(NT)..Conclusion For patients with cervical cancer after hysterectomy, the FFF beam achieved target and OAR dose distribution similar to that of the FF beam. Reduction of beam-on time in cervical cancer is beneficial.展开更多
<strong>Background:</strong><span><span><span style="font-family:""><span style="font-family:Verdana;"> Postoperative irradiation for brain tumor in pregnan...<strong>Background:</strong><span><span><span style="font-family:""><span style="font-family:Verdana;"> Postoperative irradiation for brain tumor in pregnant women is a matter of concern. </span><b><span style="font-family:Verdana;">Aim:</span></b><span style="font-family:Verdana;"> We aimed to assess the safety of radiotherapy for brain tumors in pregnancy. We here report a successful treatment for anaplastic astrocytoma during pregnancy: surgery + postoperative irradiation. We wish to emphasize how we devised irradiation procedure to achieve both therapeutic effectiveness and safety to the fetus/infant. </span><b><span style="font-family:Verdana;">Case Presentation: </span></b><span style="font-family:Verdana;">A 34-year-old pregnant woman suffered with brain anaplastic astrocytoma. Tumor resection under craniotomy was performed with success. We decided to conduct postoperative radiotherapy at 25 weeks of gestation to reduce the risk of recurrence. We used a flattening filter-free volumetric arc therapy (FFF-VMAT) technique, which can achieve lower out-of-field dose than VMAT with a flattening filter or helical tomotherapy. We prescribed 60 Gy over 30 fractions. During actual beam delivery, surface and rectal dose to the patient (mother) were measured. The total fetal dose was estimated at 0.006 - 0.018 Gy, which is under the threshold set by the ICRP. A male healthy infant was born vaginally at the 37th week of pregnancy. The patient (mother) and the infant are healthy at the time of writing.</span><b><span style="font-family:Verdana;"> Conclusion: </span></b><span style="font-family:Verdana;">FFF-VMAT is a good choice for brain tumors during pregnancy</span></span></span></span><span style="font-family:Verdana;">.</span>展开更多
There is increasing interest in the clinical use of flattening filter-free(FFF) beams.In this study,we aimed to investigate the dosimetric characteristics of volumetric modulated arc radiotherapy(VMAT) with FFF beams ...There is increasing interest in the clinical use of flattening filter-free(FFF) beams.In this study,we aimed to investigate the dosimetric characteristics of volumetric modulated arc radiotherapy(VMAT) with FFF beams for nasopharyngeal carcinoma(NPC).Ten NPC patients were randomly selected to undergo a RapidArc plan with either FFF beams(RA-FFF) or conventional beams(RA-C).The doses to the planning target volumes(PTVs),organs at risk(OARs),and normal tissues were compared.The technical delivery parameters for RapidArc plans were also assessed to compare the characteristics of FFF and conventional beams.Both techniques delivered adequate doses to PTVs.For PTVs,RA-C delivered lower maximum and mean doses and improved conformity and homogeneity compared with RA-FFF.Both techniques provided similar maximum doses to the optic nerves and lenses.For the brain stem,spinal cord,larynx,parotid glands,oral cavity,and skin,RA-FFF showed significant dose increases compared to RA-C.The dose to normal tissue was lower in RA-FFF.The monitor units(MUs) were(536 ± 46) MU for RA-FFF and(501± 25) MU for RA-C.The treatment duration did not significantly differbetween plans.Although both treatment plans could meet clinical needs,RA-C is dosimetrically superior to RA-FFF for NPC radiotherapy.展开更多
Objective This study aimed to analyze the dosimetric parameters of volumetric modulated arc therapy(VMAT) and dynamic multileaf collimator(DMLC) plans with lumbosacral spine(LS) and pelvic bone marrow(PBM) sparing in ...Objective This study aimed to analyze the dosimetric parameters of volumetric modulated arc therapy(VMAT) and dynamic multileaf collimator(DMLC) plans with lumbosacral spine(LS) and pelvic bone marrow(PBM) sparing in the flattening filter-free(FFF) model.Methods Thirty patients with cervical cancer were selected for analysis.For each patient,four plans with different strategies were generated:VMAT_FF,VMAT_FFF,DMLC_FF,and DMLC_FFF.Dose volumes for organs at risk,conformity index,heterogeneity index(HI),and total number of machine unit(MU) were compared by paired t-test.Result Compared with plans in the FF model,the irradiated dose to LS significantly decreased both VMAT_FFF and DMLC_FFF plans in the FFF model while the MU increased.The mean dose of LS decreased by 107.2 cGy(P<0.05) in the VMAT_FFF plan.In comparison with the VMAT plans in both models of FF and FFF,the DMLC plans reduced the dose volume of 10 Gy by 5.9%(P<0.05),and the mean dose of LS was 189.6-293.1 cGy.The PBM volume receiving 40 Gy showed a decrease of 0.5%-1.1%(P<0.05) as well.The HI increased in the VMAT plans by approximately 0.053 and 0.039.Conclusion The DMLC plans exhibited the best sparing of the PBM and LS in both FF and FFF models and increased the HI.The plans in the FFF model could limit the volume dose of LS but increase the MU.展开更多
目的比较肺癌立体定向放射治疗有无均整器模式下容积旋转调强(VMAT)计划,评估两种模式计划的剂量学和计划执行效率差异。方法选择行立体定向放射治疗的非小细胞肺癌患者20例,其中男性14例,女性6例;年龄42~83岁,中位年龄62岁;TNM分期T_(1...目的比较肺癌立体定向放射治疗有无均整器模式下容积旋转调强(VMAT)计划,评估两种模式计划的剂量学和计划执行效率差异。方法选择行立体定向放射治疗的非小细胞肺癌患者20例,其中男性14例,女性6例;年龄42~83岁,中位年龄62岁;TNM分期T_(1)N0M0_(7)例,T2N0M013例;病理诊断类型,腺癌15例,鳞状细胞癌5例。基于Monte Carlo算法设计有均整器(FF)模式和无均整器(FFF)模式的VMAT计划,计划靶区(PTV)给予相同的处方剂量50 Gy/5F照射,在满足临床要求的情况下,比较两种计划在剂量学、机器跳数、出束时间及计划验证通过率的差异。结果FFF模式PTV的适形指数(CI)优于FF模式,差异有统计学意义(0.87±0.21 vs 0.84±0.04。P<0.05),梯度指数(GI)差异亦有统计学意义(5.22±0.09 vs 5.95±0.17。P<0.05),靶区D_(98%)、D2%、D_(2cm)两者比较,差异均无统计学意义(P>0.05);FFF模式在食管平均剂量保护上优于FF模式[(5.02±1.34)Gy vs(5.81±0.76)Gy。P<0.05],在脊髓的D0.25cc、心脏D150cc、双肺D1000cc、D1500cc、Dmean及皮肤D10cc两者比较,差异无统计学意义(P>0.05);FFF模式的机器总跳数相对于FF模式增加,出束总时间较FF模式缩短,两种模式间差异均有统计学意义[4072.72±273.04 vs 3638.79±255.35、(303.52±137.20)s vs(429.95±158.04)s。P<0.05]。两种模式基于TH=10%、3%/2 mm的条件下伽马分析,验证率均大于95%,差异无统计学意义(P>0.05)。结论基于Monte Carlo算法下有无均整器模式肺癌立体定向放射治疗均能满足临床需求,FFF模式的肺癌立体定向放射治疗能提升靶区的适形度并降低靶区GI,较FF模式有一定的剂量优势;FFF模式下,计划执行效率有所提升。展开更多
国际原子能机构(International Atomic Energy Agency,IAEA)与美国医学物理学家协会(American Association of Physicists in Medicine,AAPM)联合制定的外照射光子束小野静态射野剂量学操作规程(TRS-483)中提供的小野射野输出修正因子(k...国际原子能机构(International Atomic Energy Agency,IAEA)与美国医学物理学家协会(American Association of Physicists in Medicine,AAPM)联合制定的外照射光子束小野静态射野剂量学操作规程(TRS-483)中提供的小野射野输出修正因子(k_(Qclin,Qref)^(fclin,fref))未考虑均整模式(Flattening Filter,FF)、非均整模式(Flattening Filter Free,FFF)束流间差异,对于电离室在相同射野条件下测量的小野射野输出因子(Ω^(fclin,fref) _(Qclin,Qref))给出相同修正系数,可能引入超过1%的偏差。据此,提出利用蒙特卡罗模拟细化电离室k_(Qclin,Qref)^(fclin,fref)的方法,对FF、FFF束流下电离室小野测量数据进行分别修正,进一步提升临床小野剂量测量准确性。基于EGSnrc构建Elekta Synergy加速器机头模型,建立电离室k_(Qclin,Qref)^(fclin,fref)模拟方法。通过电离室在FF束流不同射野条件下Ω^(fclin,fref)_(Qclin,Qref)的测量及修正,验证蒙特卡罗计算模型,并分别计算了6款小灵敏体积电离室在FF、FFF束流不同射野范围(0.8 cm×0.8 cm~10 cm×10 cm)的k_(Qclin,Qref)^(fclin,fref)。研究发现,同一电离室在FF、FFF束流不同射野条件下计算的k_(Qclin,Qref)^(fclin,fref)存在明显差异,其中PTW 31015在FFF模式下计算的k_(Qclin,Qref)^(fclin,fref)与FF模式计算结果相比最大偏差超过1.02%。因此,通过细化电离室k_(Qclin,Qref)^(fclin,fref)的方法能够有效提升临床小野水吸收剂量测量准确性。展开更多
文摘Flattening filter-free(FFF) beams generated by medical linear particle accelerators(linacs) have recently been used in radiotherapy clinical practice.FFF beams have fundamental physical parameter differences with respect to standard flattening filter(FF) beams,such that the generally used dosimetric parameters and definitions are not always viable.This study investigates dosimetric parameters for use in the quality assurance of FFF beams generated by medical linacs in radiotherapy.The main characteristics of the photon beams are analyzed using specific data generated by a Varian True Beam linac having both FFF and FF beams of 6 and 10 MV(megavolt) energy,respectively.Definitions for dose profile parameters are suggested,starting from the renormalization of the FFF with respect to the corresponding FF beam.From this point,the flatness concept is translated into one of "un-flatness",and other definitions are proposed,maintaining a strict parallelism between FFF and FF parameter concepts.The quality controls used in establishing a quality assurance program when introducing FFF beams into the clinical environment are given,maintaining similarity to those used for standard FF beams,and recommendations for the introduction of FFF beams into clinical radiotherapy application for breast cancer patients are provided as an example for comparison between FFF and FF for dose distribution and coverage for a target volume.Although there are many advantages of using a FFF beam,especially for advanced radiotherapy techniques,there are a few limitations(e.g.,using a relatively higher energy photon beam for stereotactic radiotherapy(SRT),limited speed of current multileaf collimators(MLCs),and off-axis distance-dependent modulation in intensitymodulated radiation therapy(IMRT)) as well as challenges(e.g.,criteria for beam quality evaluation and penumbra,establishment of dosimetry methods,and consequences of photon target burn-up) that need to be addressed for establishing the FFF beam as a viable alternative to the FF beam.
基金Supported by a grant of the Military Medical Metrology Project(No.2011-JL2-005)
文摘Objective The aim of the study was to compare flattening filter-free(FFF) beams and conventional flattening filter(FF) beams in volumetric modulated arc therapy(VMAT) for cervical cancer after surgery, through a retrospective planning study.Methods VMAT plans of FFF beams and normal FF beams were designed for a cohort of 15 patients. The prescribed dose was 45 Gy to 1.8 Gy per fraction, and at least 95% of the planning target volume received this dose. Doses were computed with a commercially available treatment planning system using a Monte Carlo(MC) algorithm. Plans were compared according to dose-volume histogram analysis in terms of planning target volume homogeneity and conformity indices(HI and CI), as well as organs at risk(OAR) dose and volume parameters. Results FFF-VMAT was similar to FF-VMAT in terms of CI, but inferior to FF-VMAT considering HI. No statistically differences were observed between FFF-VMAT and FF-VMAT in following organ at risks including pelvic bone marrow, small bowel, bladder, rectum, and normal tissue(NT)..Conclusion For patients with cervical cancer after hysterectomy, the FFF beam achieved target and OAR dose distribution similar to that of the FF beam. Reduction of beam-on time in cervical cancer is beneficial.
文摘<strong>Background:</strong><span><span><span style="font-family:""><span style="font-family:Verdana;"> Postoperative irradiation for brain tumor in pregnant women is a matter of concern. </span><b><span style="font-family:Verdana;">Aim:</span></b><span style="font-family:Verdana;"> We aimed to assess the safety of radiotherapy for brain tumors in pregnancy. We here report a successful treatment for anaplastic astrocytoma during pregnancy: surgery + postoperative irradiation. We wish to emphasize how we devised irradiation procedure to achieve both therapeutic effectiveness and safety to the fetus/infant. </span><b><span style="font-family:Verdana;">Case Presentation: </span></b><span style="font-family:Verdana;">A 34-year-old pregnant woman suffered with brain anaplastic astrocytoma. Tumor resection under craniotomy was performed with success. We decided to conduct postoperative radiotherapy at 25 weeks of gestation to reduce the risk of recurrence. We used a flattening filter-free volumetric arc therapy (FFF-VMAT) technique, which can achieve lower out-of-field dose than VMAT with a flattening filter or helical tomotherapy. We prescribed 60 Gy over 30 fractions. During actual beam delivery, surface and rectal dose to the patient (mother) were measured. The total fetal dose was estimated at 0.006 - 0.018 Gy, which is under the threshold set by the ICRP. A male healthy infant was born vaginally at the 37th week of pregnancy. The patient (mother) and the infant are healthy at the time of writing.</span><b><span style="font-family:Verdana;"> Conclusion: </span></b><span style="font-family:Verdana;">FFF-VMAT is a good choice for brain tumors during pregnancy</span></span></span></span><span style="font-family:Verdana;">.</span>
文摘There is increasing interest in the clinical use of flattening filter-free(FFF) beams.In this study,we aimed to investigate the dosimetric characteristics of volumetric modulated arc radiotherapy(VMAT) with FFF beams for nasopharyngeal carcinoma(NPC).Ten NPC patients were randomly selected to undergo a RapidArc plan with either FFF beams(RA-FFF) or conventional beams(RA-C).The doses to the planning target volumes(PTVs),organs at risk(OARs),and normal tissues were compared.The technical delivery parameters for RapidArc plans were also assessed to compare the characteristics of FFF and conventional beams.Both techniques delivered adequate doses to PTVs.For PTVs,RA-C delivered lower maximum and mean doses and improved conformity and homogeneity compared with RA-FFF.Both techniques provided similar maximum doses to the optic nerves and lenses.For the brain stem,spinal cord,larynx,parotid glands,oral cavity,and skin,RA-FFF showed significant dose increases compared to RA-C.The dose to normal tissue was lower in RA-FFF.The monitor units(MUs) were(536 ± 46) MU for RA-FFF and(501± 25) MU for RA-C.The treatment duration did not significantly differbetween plans.Although both treatment plans could meet clinical needs,RA-C is dosimetrically superior to RA-FFF for NPC radiotherapy.
基金General program of National Natural Science Foundation of China,31371425microRNA regulates the mechanism of mitochondrial fusion protein OPA1 involved in apoptosis induced by chemotherapy drugs Special fund of NSFC director,31240025regulation of mitochondrial injury on apoptosis induced by sorafenib
文摘Objective This study aimed to analyze the dosimetric parameters of volumetric modulated arc therapy(VMAT) and dynamic multileaf collimator(DMLC) plans with lumbosacral spine(LS) and pelvic bone marrow(PBM) sparing in the flattening filter-free(FFF) model.Methods Thirty patients with cervical cancer were selected for analysis.For each patient,four plans with different strategies were generated:VMAT_FF,VMAT_FFF,DMLC_FF,and DMLC_FFF.Dose volumes for organs at risk,conformity index,heterogeneity index(HI),and total number of machine unit(MU) were compared by paired t-test.Result Compared with plans in the FF model,the irradiated dose to LS significantly decreased both VMAT_FFF and DMLC_FFF plans in the FFF model while the MU increased.The mean dose of LS decreased by 107.2 cGy(P<0.05) in the VMAT_FFF plan.In comparison with the VMAT plans in both models of FF and FFF,the DMLC plans reduced the dose volume of 10 Gy by 5.9%(P<0.05),and the mean dose of LS was 189.6-293.1 cGy.The PBM volume receiving 40 Gy showed a decrease of 0.5%-1.1%(P<0.05) as well.The HI increased in the VMAT plans by approximately 0.053 and 0.039.Conclusion The DMLC plans exhibited the best sparing of the PBM and LS in both FF and FFF models and increased the HI.The plans in the FFF model could limit the volume dose of LS but increase the MU.
文摘目的比较肺癌立体定向放射治疗有无均整器模式下容积旋转调强(VMAT)计划,评估两种模式计划的剂量学和计划执行效率差异。方法选择行立体定向放射治疗的非小细胞肺癌患者20例,其中男性14例,女性6例;年龄42~83岁,中位年龄62岁;TNM分期T_(1)N0M0_(7)例,T2N0M013例;病理诊断类型,腺癌15例,鳞状细胞癌5例。基于Monte Carlo算法设计有均整器(FF)模式和无均整器(FFF)模式的VMAT计划,计划靶区(PTV)给予相同的处方剂量50 Gy/5F照射,在满足临床要求的情况下,比较两种计划在剂量学、机器跳数、出束时间及计划验证通过率的差异。结果FFF模式PTV的适形指数(CI)优于FF模式,差异有统计学意义(0.87±0.21 vs 0.84±0.04。P<0.05),梯度指数(GI)差异亦有统计学意义(5.22±0.09 vs 5.95±0.17。P<0.05),靶区D_(98%)、D2%、D_(2cm)两者比较,差异均无统计学意义(P>0.05);FFF模式在食管平均剂量保护上优于FF模式[(5.02±1.34)Gy vs(5.81±0.76)Gy。P<0.05],在脊髓的D0.25cc、心脏D150cc、双肺D1000cc、D1500cc、Dmean及皮肤D10cc两者比较,差异无统计学意义(P>0.05);FFF模式的机器总跳数相对于FF模式增加,出束总时间较FF模式缩短,两种模式间差异均有统计学意义[4072.72±273.04 vs 3638.79±255.35、(303.52±137.20)s vs(429.95±158.04)s。P<0.05]。两种模式基于TH=10%、3%/2 mm的条件下伽马分析,验证率均大于95%,差异无统计学意义(P>0.05)。结论基于Monte Carlo算法下有无均整器模式肺癌立体定向放射治疗均能满足临床需求,FFF模式的肺癌立体定向放射治疗能提升靶区的适形度并降低靶区GI,较FF模式有一定的剂量优势;FFF模式下,计划执行效率有所提升。
文摘国际原子能机构(International Atomic Energy Agency,IAEA)与美国医学物理学家协会(American Association of Physicists in Medicine,AAPM)联合制定的外照射光子束小野静态射野剂量学操作规程(TRS-483)中提供的小野射野输出修正因子(k_(Qclin,Qref)^(fclin,fref))未考虑均整模式(Flattening Filter,FF)、非均整模式(Flattening Filter Free,FFF)束流间差异,对于电离室在相同射野条件下测量的小野射野输出因子(Ω^(fclin,fref) _(Qclin,Qref))给出相同修正系数,可能引入超过1%的偏差。据此,提出利用蒙特卡罗模拟细化电离室k_(Qclin,Qref)^(fclin,fref)的方法,对FF、FFF束流下电离室小野测量数据进行分别修正,进一步提升临床小野剂量测量准确性。基于EGSnrc构建Elekta Synergy加速器机头模型,建立电离室k_(Qclin,Qref)^(fclin,fref)模拟方法。通过电离室在FF束流不同射野条件下Ω^(fclin,fref)_(Qclin,Qref)的测量及修正,验证蒙特卡罗计算模型,并分别计算了6款小灵敏体积电离室在FF、FFF束流不同射野范围(0.8 cm×0.8 cm~10 cm×10 cm)的k_(Qclin,Qref)^(fclin,fref)。研究发现,同一电离室在FF、FFF束流不同射野条件下计算的k_(Qclin,Qref)^(fclin,fref)存在明显差异,其中PTW 31015在FFF模式下计算的k_(Qclin,Qref)^(fclin,fref)与FF模式计算结果相比最大偏差超过1.02%。因此,通过细化电离室k_(Qclin,Qref)^(fclin,fref)的方法能够有效提升临床小野水吸收剂量测量准确性。
