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Objective:To analyze the dosimetric differences of volumetric modulated arc therapy (VMAT) plans for lung cancer caused by different dose calculation algorithms and radiation field settings and thus to provide a reference for designing clinical VMAT plans for lung cancer.Methods:This study randomly selected 20 patients with lung cancer and divided them into four groups of VMAT plans, namely, a group adopting two fields and two arcs based on the AAA algorithm (2F2A_AAA), a group employing two fields and two arcs based on the AXB algorithm (2F2A_AXB), a group using two fields and two arcs based on the MC algorithm (2F2A_MC), and a group adopting one field and two arcs based on the MC algorithm (1F2A_MC). Then, this study evaluated the target coverage, high-dose control, dose homogeneity index (HI), conformity index (CI), and organs at risk (OARs) of the plans using different algorithms and radiation field settings.Results:The planning target volume (PTV) results of two fields combined with two arcs (2F2A) of three groups using different algorithms are as follows. 2F2A_MC achieved better results in both D1% and V 95% (the relative volume of the target volume surrounded by 95% of the prescribed dose) of planning gross target volume (PGTV) than 2F2A_AAA (D1%: t=-2.44, P=0.03; V95%:z=-2.04, P=0.04) and 2F2A_AXB (D1%: t=2.34, P=0.03; z=-3.21, P < 0.01). 2F2A_AXB outperformed 2F2A_AAA ( z=-3.66, P < 0.01) and was comparable to 2F2A_MC in terms of the CI of PGTV. Regarding OARs, 2F2A_AXB and 2F2A_MC decreased the V5 Gy of the whole lung by 0.68% ( z=-2.69, P=0.01) and 3.05% ( z=-3.52, P < 0.01), respectively compared to 2F2A_AAA. 2F2A_AXB achieved a whole-lung Dmean of 1776.44 cGy, which was superior to that of 2F2A_MC ( t=2.67, P=0.02) and 2F2A_AAA ( t=8.62, P < 0.01). Compared to 2F2A_AAA and 2F2A_MC, 2F2A_AXB decreased the V20 Gy of Body_5 mm by 1.45% ( z=-3.88, P < 0.01) and 2.01% ( z=-3.66, P < 0.01), respectively. The results of the two groups with different field settings showed that 1F2A_MC was superior to 2F2A_MC in both the CI of PTV1 and the HI of PTV2 (CI: t=2.61, P=0.02; HI: z=-2.20, P=0.03). Moreover, 1F2A_MC increased the Dmean of the whole lung by 26.29 cGy compared to 2F2A_MC ( t=2.28, P=0.04). Conclusions:Regarding the design of VMAT plans for lung cancer, the MC algorithm is suitable for the target priority and the AXB algorithm is suitable for the OAR priority. When only the MC algorithm is available, it is recommended to choose 1F2A in the case of target priority and select 2F2A in the case of OAR priority.
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Objective To explore the intensity of coplanar arc-adjusted radiotherapy with volume-modulated arc therapy (VMAT) and whether the position of the head tilt influences the distribution of radiotherapy dose.Methods From 2015 to 2017,500 patients underwent radiotherapy of the head and kept their head tilted.The simulated non-inclined CT images were obtained by rotating the original CT images.The protocol of the coplanar VMAT whole brain irradiation was 30 Gy and the maximum dose of planning target volume in the hippocampus was limited to 16 Gy.The doses of the optic nerve,optic chiasm and eyeball were lower than 37.5 Gy.The dosimetric parameters of two different protocols were statistically compared by paired t-test.Results The average head tilt angle was (11.12°±0.68°).The homogeneity and the conformal index in the tilted and non-tilted positions were decreased by (8.3±9.6) ％(P=0.033) and (5.2±4.1)％(P=0.009).The dose of hippocampus in the tilted position of the head was decreased by (13.6±6.2) ％ on average compared with that in the non-inclined position (P=0.004).The dose of the lenses was decreased by (15.5±11.1)％(P=0.008) on average.The doses of optic nerve and eyeball were declined by (6.8±5.6) ％(P=0.013) and (8.6±6.5) ％(P=0.016).Conclusions By tilting the head at an appropriate angle during VMAT whole-brain radiotherapy,the radiation dose distribution of the target volume can be significantly improved and the radiation dose in the hippocampus and visual system can be reduced simultaneously to maintain the therapeutic effect and minimize the effect upon the cognitive and memory function of patients.
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Objective@#To explore the intensity of coplanar arc-adjusted radiotherapy with volume-modulated arc therapy (VMAT) and whether the position of the head tilt influences the distribution of radiotherapy dose.@*Methods@#From 2015 to 2017, 500 patients underwent radiotherapy of the head and kept their head tilted. The simulated non-inclined CT images were obtained by rotating the original CT images. The protocol of the coplanar VMAT whole brain irradiation was 30 Gy and the maximum dose of planning target volume in the hippocampus was limited to 16 Gy. The doses of the optic nerve, optic chiasm and eyeball were lower than 37.5 Gy. The dosimetric parameters of two different protocols were statistically compared by paired t-test.@*Results@#The average head tilt angle was (11.12°±0.68°). The homogeneity and the conformal index in the tilted and non-tilted positions were decreased by (8.3±9.6)%(P=0.033) and (5.2±4.1)%(P=0.009). The dose of hippocampus in the tilted position of the head was decreased by (13.6±6.2)% on average compared with that in the non-inclined position (P=0.004). The dose of the lenses was decreased by (15.5±11.1)%(P=0.008) on average. The doses of optic nerve and eyeball were declined by (6.8±5.6)%(P=0.013) and (8.6±6.5)%(P=0.016).@*Conclusions@#By tilting the head at an appropriate angle during VMAT whole-brain radiotherapy, the radiation dose distribution of the target volume can be significantly improved and the radiation dose in the hippocampus and visual system can be reduced simultaneously to maintain the therapeutic effect and minimize the effect upon the cognitive and memory function of patients.
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Objective To explore the feasibility of the volume modulated arc therapy ( VMAT) auto-planning based on template library ( TL). Methods VMAT plans of 68 patients diagnosed with postoperative rectal cancer in Eclipse system were retrospectively selected. The prescription dose was 50 Gy/25F. In 19 patients, the feature values of target and organs at risk were extracted as the vectors. The final optimized restricted conditions were saved as the TL. Then, the plans of 15 rectal cancer patients (10 cases from TL and 5 outside TL) were automatically optimized. According to the multi-dimensional vector similarity principle, the similarity parameter αwas defined. The designed program automatically selected the optimal-object template in an in-house software developed with Matlab. The dosimetric parameters of the auto-optimized plans with the optimal-object template (ATP) and the clinical plan (CP) were compared by the paired t-test. The changes in the dosimetric parameters and similarity parameter α were statistically compared by Pearson′s correlation analysis. The linear fitting of the dosimetric parameters with α was used by least squares method to explore the tendency of the ATP dosimetric parameters relative to CP. Results The dosimetric parameters of ATP for 13 cases were slightly worse than those of CP. The conformal index (P=0. 004), heterogeneous index (P= 0. 015),V40(P= 0. 003) and mean dose (P= 0. 022) of the intestine significantly differed. The α values of these 13 cases were 2. 67,2. 60,2. 60,2. 49,2. 67,2. 74,2. 72,2. 48, 2. 53,2. 86,2. 68,2. 56 and 2. 63. The α value was significantly correlated with the V40 or mean dose of the bladder (r= 0. 649 and 0. 603,P= 0. 016 and 0. 029).Along with the increase of α value ,V40 and mean dose of the intestine for ATP were gradually deteriorated than those of CP . The remaining dosimetric para-meters of ATP were close to or superior to those of CP. Conclusions The results of ATP are slightly worse than those of CP, whereas can satisfy the clinical requirements. The TL, the quality of TL and ATP remain to be further optimized.
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Objective To evaluate the dosimetric difference between fixed-field static intensity-modulated radiotherapy (IMRT), fixed-field dynamic multileaf collimator (DMLC), and volumetric modulated arc therapy (VMAT), all of which involve supraclavicular and infraclavicular regions, in breast cancer patients after breast-conserving surgery.Methods This study included 14 female patients with breast cancer who received radiotherapy after breast-conserving surgery in our hospital from October 2012 to April 2016.The radiation field included the chest wall and supraclavicular and infraclavicular regions.IMRT, DMLC, and VMAT plans were generated for each patient while using identical optimization conditions.The doses to planning target volume (PTV) and organs at risk (OARs) were compared based on dose-volume histogram (DVH);one-way analysis of variance or nonparametric Wilcoxon rank test was used for comparison.Results For the dose distribution of PTV, VMAT achieved the best V95, V98, CI, and HI (P<0.009).Concerning the doses to OARs, VMAT achieved the best V5, V20, and Dmean of the ipsilateral lung and the best V5 and Dmean of the contralateral lung (P<0.022).Dmean of the spinal cord was significantly lower in VMAT than in IMRT and DMLC (P=0.004).Conclusions VMAT is preferred for the patients with breast cancer to be treated with radiotherapy involving supraclavicular and infraclavicular regions after breast-conserving surgery.It can improve the dose distribution of target and reduce the doses to organs at risk and radiotherapy toxicities.
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Objective To evaluate clinical effect of volume modulated arc therapy ( VMAT) for spinal metastases .Methods Twenty patients with spinal metastases who had been treated with VMAT were chosen to participate in the study .The prescribed dose varied from 45 to 60 Gy within 15 -20 fractions, 3 Gy per fraction, and one fraction per day of VMAT .Pain and quality of life were measured before VMAT and at several time points up to 6 months after treatment , by the numerical rating scale (NRS) and verbal rating scale (VRS) and the quality of life scale for bone metastases (EORTC QLQ-BM22) questionnaire.In addition, Frankel grading was used to evaluate the neurological function of spinal cord.The primary endpoint was frequency and duration of complete pain relief , and the secondary endpoint was death.Results At the end of the follow-up, the number of patients reporting no pain from spinal metastases, as measured by the NRS, increased from 0 of 20 before VMAT to 10 of 14 ( t =20.24, P0.05).After VMAT, the patients who suffered from nerve function impairment recovered to different extent . No one had radiation-induced injury , such as radiation myelitis , radiation pneumonitis , etc.Median survival time was 10 month.Conclusions VMAT is a safe and effective treatment method for spinal metastases .Significant reductions in patient-reported pain were observed , along with nerve dysfunction improved .The patients′quality of life was significantly improved .VMAT has no late spinal cord toxicities .
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Objective To compare the dosimetric differences between helical tomotherapy (HT) and volume-modulated arc therapy (VMAT) in the treatment of upper thoracic esophageal carcinoma (UTEC).Methods A total of 10 patients with UTEC were randomly selected.HT plan and double-arc VMAT plan were designed and optimized for each patient.The prescription dose was 50 Gy/30 fractions for gross target volume (GTV), 66 Gy/30 fractions for planned target volume (PTV).The dose distribution and conformal index (CI), homogeneity index (HI) of target volume, the D1％, D5％, Dg5％, D99％, and dose of organ at risk (OAR) were analyzed by using the dose volume histogram (DVH).The monitor units and delivery time were also evaluated.Results For GTV and PTV, the D99％ of HT plans were slightly higher than those of VMAT plans (t =4.476, 3.756, P ＜ 0.05) , but no significant differences in D1％ , D5％ , D95％ , HI and CI (P ＞ 0.05) were found.The V10, V15, V20 and mean lung dose (MLD) to the total-lung of HT plans were all significantly lower than those of VMAT plans (t =-3.369,-4.824, -4.869,-3.657, P ＜ 0.05).There were no significant differences for V5, V30 and Dmax of cord (P ＞ 0.05).The monitor units and delivery time of VMAT plans were significantly lower than those of HT plans (t =13.970, 7.982, P ＜ 0.05).Conclusions Both HT and VMAT are appropriate for esophageal cancer radiotherapy.HT significantly reduces the radiation dose of the total-lung, while VMAT has obvious advantages in efficiency.
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Objective To study the novel methods of VMAT planning based dose volume histogram ( DVH) optimization, evaluated the dosimetry and planning efficiency in VMAT planning for Esophageal Carcinoma. Methods Twelve Esophageal carcinoma patients were enrolled in this study. The conventional VMAT planning as the reference, using multi?criterion optimization DVH ( MCO?DVH ) and overlapping volume histogram prediction DVH ( OVH?DVH ) two different methods to get ideal objectives function for informing VMAT plans, Then evaluate the dosimetric, planning efficiency for all new VMAT plans. The difference between the paired t?test groups. Results The two VMAT plans based DVH objective function can meet the clinical needs. Compared with the conventional VMAT plan, Conformity index ( CI ) and Homogeneity index ( 0. 77 vs. 0. 72, P=0. 017 and 0. 10 vs. 0. 12, P=0. 047 ) is better in DVH informed plans;lung V5 and spinal cord V50 are better in MCO?DVH informed plan (54. 66 vs.60. 23,P=0. 013 and 0. 98 vs.0. 49,P=0. 037).Furthermore,the DVH informed plans had higher planning efficiency (8. 2 vs. 19. 5,P=0. 023) . Conclusions DVH Objective informed VMAT Planning can achieve clinical needs with much uniform dose to target,lower OAR dose and higher planning efficiency.
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Objective To compare volumetric‐modulated arc therapy(VMAT) with intensity‐modulated radiation therapy (IMRT) for brain metastases with regard to the dosimetric character .Methods Sixty patients who were diagnosed with brain me‐tastases were included in this study .The target area received two dose levels using late addition amount technique ,WBRT (30 Gy/10 F) with following addition (20 Gy/10 F) to 59 Gy .For a fair comparison ,VMAT and IMRT treatment plans were respectively designed for every patient with the same dosimetric constraints .Dosimetric comparisons between VMAT and IMRT plans were ana‐lyzed to evaluate :target coverage and homogeneity ,conformity of PTV ;sparing of OARs ;monitor units (MUs) .Results Two treatment plans all reached the treatment need .When compared with IMRT ,there was no significant difference in Dmean of eyeball , len ,optic never ,visual chiasma ,parotid ,brain stem ,and external auditory canal of VMAT (P>0 .05) .The Dmax of eyeball ,len ,pa‐rotid ,and external auditory canal of VMAT were lower than that in IMRT group (P<0 .05) .The VMAT group has the less MUs (P=0 .017) and less treatment time .Conclusion VMAT can reach the big‐dose radiotherapy need on brain metastases clinically . There are no significant diffference between VMAT and IMRT on Dmax ,Dmean ,CI ,and HI .The Dmax of eyeball ,len ,parotid ,and external auditory canal of VMAT were lower than that in IMRT group .The VMAT can reduce the radiotherapy time .
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Objective To study the dosimetry characteristics of VMAT plan in the esophageal carcinoma radiotherapy.Methods Application of 0.6 cm3 ionization chamber and COMPASS threedimensional dose verification system,20 cases of upper and middle chest esophageal carcinoma on the VMAT plans for absolute dose and relative dose verification.Dose volume histogram (DVH) comparison treatment target,lungs,heart,and differences in the spinal cord irradiation dose and volume,and analyses γpass rate of GTV,CTV,PTV and organs at risks.Results The center dose of upper and middle chest esophageal carcinoma accurate rates were above 99％.Thoracic segment esophageal:GTV,PTV and organs at risks of γ pass rate above 97％.D95％ and Dmean of GTV,CTV and PTV were relatively undervalued within 3％.D1％ of spinal cord is 2.21％ overvalued.Left and right pulmonary V5 were slightly overvalued by about 0.5％,V10-D30,Dmean undervalued within 2％.In period of middle chest esophageal carcinoma:the gamma passed rate of GTV,CTV,PTV and organs at risks of above 97％,GTV,CTV,PTV D95％,Dmean were relatively undervalued within 2％.Spinal cord D1％ is 2.04％ overvalued.Left and right pulmonary V5-D30 to V10 as a trend of gradually to be underestimated,at 1.5％.Heart Dmean was undervalued by 2.68％.Conclusion VMAT technology is applicable in the chest esophageal carcinoma radiotherapy.