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Context: Stereotactic body radiotherapy (SBRT) is increasingly being used for early-stage lung cancer and lung oligometastases. Aims: To report our experience of setting up lung SBRT and early clinical outcomes. Settings and Design: This was a retrospective, interventional, cohort study. Subjects and Methods: Patients were identified from multidisciplinary tumor board meetings. They underwent four-dimensional computed tomography-based planning. The ROSEL trial protocol, the Radiation Therapy Oncology Group (RTOG) 0236, and the UK-Stereotactic Ablative Body Radiotherapy Consortium guidelines were used for target volume and organs-at-risks (OARs) delineation, dosimetry, and plan quality assessment. Each SBRT plan underwent patient-specific quality assurance (QA). Daily online image guidance using KVCT or MVCT was done to ensure accurate treatment delivery. Statistical Analysis Used: Microsoft Excel 2010 was used for data analysis. Results: Fifteen patients were treated to one or more lung tumors. One patient received helical tomotherapy in view of bilateral lung oligometastases at similar axial levels. All the remaining patients received volumetric modulated arc therapy (VMAT)-based treatment. The prescription dose varied from 40 to 60 Gy in 5–8 fractions with alternate-day treatment. The mean and median lung V20 was 5.24% and 5.16%, respectively (range, 1.66%–9.10%). The mean and median conformity indexes were 1.02 and 1.06, respectively (range, 0.70–1.18). After a median follow-up of 17 months, the locoregional control rate was 93.3%. Conclusions: SBRT was implemented using careful evaluation of OAR dose constraints, dosimetric accuracy and plan quality, patient-specific QA, and online image guidance for accurate treatment delivery. It was safe and effective for early-stage nonsmall cell lung cancer and lung metastases. Prospective data were collected to audit our outcomes
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Objective To investigate the effect of the angle correction factors of ionization chamber array Matrixx on the dosimetric verification of volumetric modulated arc therapy plan.Methods The Matrixx (IBA)was put in the middle of the MultiCube Phantom. Computed tomography scan was performed and the results were sent to the Raystation treatment planning system(TPS). All data calculated from TPS and actually measured using MatriXX were gained under the following conditions:6 MV,100 MU,28 cm×28 cm radiation field. And the directions of beam were from 0°to 180°with an interval of 5°(except an interval of 1° from 85° to 95°). The angle correction factors(CF)(θ)cor of MatriXX were calculated by the calculated dose values from TPS and the measured values using MatriXX and then mirrored to the opposite side. CF (θ)cor values were compared with CF(θ)def values that were given by manufacturer. The comparison was made by paired t-test. Results CF(θ)cor and CF(θ)def were different, and the difference was significant between 85° and 95°,with a maximum of 7.5%(P<0.05). The CF(θ)cor correction method had a higher gamma pass rate than the CF(θ)def correction method,with a maximum of 17%(P<0.05). Conclusions The ionization chamber array MatriXX has an angular dependence and the angle correction should be performed.The angle correction factors have the individual characteristics and are different in every unit ionization chamber of the MatriXX. Therefore, it is necessary to do angle correction for every unit ionization chamber of the MatriXX and the possible errors caused by various factors should be considered in order to improve the accuracy rate and gamma pass rate of the plan verification.
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Objective To study the real?time dose verification with 2D array ion chamber array in volumetric modulated arc therapy ( VMAT) with a 2D array ion chamber array. Methods The 2D ion chamber array was fixed on the panel of electronic portal imaging device (EPID). Source?detector distance (SDD) was 140 cm. 8 mm RW3 solid water was added to the 2D array to improve the signal noise ratio. Patient plans for esophageal, prostate and liver cancers were selected to be delivered on the cylindrical Cheese phantom 5 times in order to validate the reproducibility of doses. Real?time patient transit dose measurements were performed at each fraction. Dose distributions were evaluated using gamma index criteria of 3 mm DTA and 3% dose difference referred to the first time result. Results The gamma index pass rate in the Cheese phantom were about 98%;the gamma index pass rate for esophageal, prostate and liver cancer patient were about 92%, 92% and 94%, respectively. Gamma pass rate for all single fraction were more than 90%. Conclusions The 2D array is capable of monitoring the real time transit doses during VMAT delivery. It is helpful to improve the treatment accuracy.
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Objective To compare the dosimetric parameters of volumetric modulated arc therapy(VMAT),fixed field intensity modulated radiation therapy(IMRT)and three-dimensional conformal radiotherapy(3D-CRT)in the radiotherapy for the patients with locally recurrent nasopharyngeal carcinoma, and to analyze their characteristics. Methods Twelve patients with locally recurrent nasopharyngeal carcinoma were treated with VMAT, IMRT and 3D-CRT plan designed by Pinnacle 9.2 and Preciseplan 2.03 treatment planning system.The dosimetric parameters of targeted volumes and organs at risk were compared between three groups. Results The conformation indexes (CI)of VMAT and IMRT plans were similar,and they were both better than 3D-CRT plan,the difference was significant(P0.05).The monitor units(MU)and beam time in 3D-CRT group were better than those in other two groups,and VMRT group was better than IMRT group,the statistical differences were observed between three groups (P0.05).The doses of the spinal cord,optic nerve,optic chiasm and temporal lobe of brain in VMAT and IMRT groups were better than those in 3D-CRT group,there were statistical differences between them(P0.05).Conclusion There are differences of the targeted dose distribution between the three kinds of radiation technology, while VMAT and IMRT plans can cover the targeted areas and reduce the received doses of organs at risk.The CI,MU and beam time of VMAT plan are better than those of IMRT plan. 3D-CRT plan only has advantage in the MU and beam time.
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Objective To compare the dosimetric characteristics of intensity-modulated arc therapy( IMAT ),fixed-gantry intensity-modulated radiotherapy ( IMRT ) and 3-dimensional conformal radiotherapy (3D-CRT) for the thoracic esophageal cancer.Methods A total of 15 patients with thoracic esophageal cancer were enrolled.3D-CRT,5-field IMRT( IMRT5 ),7-field IMRT( IMRT7 ),9-field IMRT ( IMRT9 ),single arc ( Arc1 ) and double arc ( Arc2 ) RapidArc plans were generated for each patient.All plans were prescribed 40 Gy in 20 fractions and 19.6 Gy in 14 fractions to PTV at 95％ isodose line.Results RapidArc and all IMRT treatment plans in dosimetric parameters of target volumes were obviously better compared to 3-dimentional conformal treatments( t =5.77,3.52,P ＜ 0.05 ).The result of V95 of PTV for 3D-CRT,IMRT5,IMRT7,IMRT9,Arc1 and Arc2 plans was 91.55 ±2.90,96.66 ±1.05,96.87 ± 1.23,96.81 ± 1.16,94.98 ± 1.41 and 95.93 ± 1.32,respectively.The best conformation index in PTV was observed in the RapidArc plans ( t =3.76,10.01,P ＜ 0.05 ),and the best homogeneity index in PTV was observed in the IMRT plans( t =3.93,3.37,P ＜ 0.05 ).In terms of organ sparing,no statistical difference was observed between IMRT and RapidArc plans( P ＞ 0.05 ),while 3D-CRT provided the lowest number of V1 cGy and V5 cGy for total lung.Compared with the IMRT treatment plans,the number of monitor units was lower in all 3D-CRT and RapidArc cases with differences of 75％.Conclusions All the IMRT and RapidArc plans could offer high quality treatment for patients.3D-CRT might show advantage in low-dose region to organs at risk.Compared with IMRT,no obvious advantage in PTV dosimetric parameters could be observed in RapidArc plans.
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Objective To compare the dosimetric differences of three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT) and volumetric modulated arc radiotherapy(V-MAT) for external beam partial breast irradiation.Methods Twelve patients with breast cancer receiving breast-conserving surgery and external beam partial breast irradiation were enrolled.Three different techniques including 3D-CRT,IMRT and V-MAT were designed for each patient.The dosimetry in the target,the dose to the organs at risk(OAR),the MU and delivery time were compared.Results All three plans met the clinical requirement. 3D-CRT showed the worst conformity in target. V-MAT provided the lowest target coverage and homogeneity in target.3D-CRT plans showed the lowest values for the V5,V10,mean dose and the highest values for V30 in the ipsilateral lung.No statistically significant differences were observed in V20 of the ipsilateral lung among three plans.V-MAT showed the lowest values in ipsilateral normal breast volume 15,20 and 25 Gy post-irradiation.For V5,the mean and max dose in heart,the mean dose in contralateral lung and the mean,max dose in thyroid,IMRT and 3D-CRT showed the highest and lowest value respectively(z =-2.94 - -2.09,P ＜ 0.05 ).The MUs in 3D-CRT,IMRT and V-MAT were 417.6 ± 34.4,772.8 ± 54.4 and 631.0 ± 109.0,respectively (z =- 2.93, - 2.76,-2.93,P ＜ 0.05 ). V-MAT significantly reduced the delivery time. Conclusions V-MAT shows significant advantages in reducing the dose in the ipsilateral normal breast and the delivery time compared with 3D-CRT and IMRT.