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Objective:To compare the dose distribution among CyberKnife, Tomotherapy, Edge, Triology and γ-knife in stereotactic body radiation therapy (SBRT) for pancreatic cancer.Methods:Clinical data of 10 panreatic cancer patients receiving CyberKinife treatment were retrospectively analyzed. The treatment plans were designed by five apparatuses from five centers according to the uniform requirement. All plans were transferred to MIM system for the extraction of parameters, which mainly included D min, D mean and D max of PTV, conformity index (CI), new conformity index (nCI), homogeneity index (HI), gradient index (GI), coverage, D max and dose-volume of the stomach and bowel. Results:The best CI and nCI were obtained in Triology ( P<0.001), and the worst HI was found in γ-knife ( P<0.001). The best GI was found in CyberKnife, followed by γ-knife and Tomotherapy, and Edge showed the worst GI ( P<0.001). The highest D min of PTV was found in both Edge and Triology, while lower D min of PTV was found in CyberKnife and Tomotherapy ( P<0.001). Additionally, γ-knife provided the highest D mean and D max of PTV ( P<0.001). Regarding the organs at risk, the lowest D max and D 5cm 3 of the bowel ( P<0.001), D max of the stomach ( P=0.003), D max( P=0.001), D 5cm 3 ( P<0.001) and D 10cm 3 ( P=0.005) of the duodenum, D max( P<0.001) and D 0.35cm 3 ( P<0.001) of the spinal cord were found in CyberKnife. The highest D max of the bowel was found in γ-knife. Furthermore, the highest D 5cm 3 of the duodenum was demonstrated in Edge ( P<0.001) and Tomotherapy provided the highest D max( P<0.001) and D 0.35cm 3 of the spinal cord ( P<0.001). Conclusions:All five radiotherapy apparatuses can meet the requirement of SBRT for pancreatic cancer. More rapid dose fall-off could be obtained via CyberKnife and γ-knife. Triology and Edge provide better target conformity. CyberKnife can better protect the gastrointestinal tract.
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Objective To investigate the feasibility and plan quality of the image-guided volumetric modulated arc therapy (VMAT) based voluntary deep exhale breath-holding technique in the stereotactic ablative body radiotherapy (SABR) for liver tumors.Methods Fifteen patients with liver tumors were involved in this study.All patients were immobilized with voluntary deep exhale breath hold (vDEBH) combined with real-time position management (RPM) respiratory gating system.Treatment was planned using VMAT with 2 modified partial arc and re-planned using intensity modulated radiation therapy (IMRT) technique for comparison.Dosimetric parameters were calculated for plan quality assessment.Quality assurance studies included absolute dose and multiple planar dose verifications,total monitor units and delivery time analysis.Daily cone beam computed tomography imaging was used to verify the motions.Results There were no significant dosimetric differences between VMAT and conventional IMRT plans (P ＞0.05).Both techniques were able to minimize doses to organs at risk including normal liver,kidneys,spinal cord,and stomach.However,the average monitor units with VMAT were significantly lower 28.1％ than those with IMRT(t =3.064,P ＜0.05).The average beam-on time in VMAT plans was 31.6％ shorter than that in IMRT plans(t =2.278,P ＜ 0.05).Conclusions The utilization of VMAT in the treatment planning of SABR for liver tumors under breath control mode has better dosimetrics.In comparison to conventional IMRT plans,VMAT plans have higher efficiency and feasibility.
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Objective To evaluate the performance of a customized vacuum-form body immobilization method in the radiotherapy of pelvic malignancies by comparing it with conventional approaches, thus to improve immobilization accuracy in the radiotherapy of pelvic malignancies. Methods A total of 66 patients with pelvic malignancies were enrolled in this study. These patients were divided into three groups according to three immobilization approaches: radiotherapy board ( Group N ) , conventional vacuum cushion ( Group V ) , and a customized vacuum cushion specifically for pelvic immobilization ( Group New-V) . Setup deviations of these immobilizations were comparatively evaluated by translational and rotational errors during intra-fractional measurements. Results The average translational setup errors in vertical(x), longitudinal(y), lateral(z) and rotational error r were (0. 35 ± 0. 37), (0. 21 ± 0. 22), (0. 29 ± 0. 28) cm and (0. 70 ± 0. 65)° for Group New-V; (0. 44 ± 0. 43), (0. 31 ± 0. 62), (0. 45 ± 0. 60) cm and (1. 25 ± 1. 00)° for Group N; (0. 38 ± 0. 36), (0. 27 ± 0. 25), (0. 32 ± 0. 29) cm and (1. 09 ± 0. 77)° for Group V, respectively. Significant differences were observed in r direction among these three method (F=7. 859,P <0. 05). Group New-V with customized cushion showed the least standard deviations in four directions and the least setup error in r direction compared with the other two method (F=3. 166,P<0. 05). Reconstructed dose distribution based on the isocenter shift result ed from setup errors revealed that Group New-V showed the least deviations in the minimum and mean dose and of the planning target volume (PTV) before and after isocenter shift(F=8. 018, P<0. 05). Conclusions The customized vacuum cushion provided best immobilization and dosimetric advantage. It helps to optimize the immobilization accuracy and improve the clinic outcome potentially.
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Objective To analyze the radiation dose to contra-lateral breasts and estimate the incidence risk of contra-lateral breast cancer for women undergone unilateral breast cancer radiotherapy.Methods The radiation doses of contra-lateral breasts for 49 patients were counted and analyzed in a hospital,and the risk of contra-lateral breast cancer in different age groups that induced by radiotherapy was estimated based on BEIR Ⅶ model combined with the Chinese lifetime table.Results The prescribed doses for the patients were all 50 Gy.The mean dose to contra-lateral breasts ranged from 0.14 Gy to 3.59 Gy,with an average of (1.21 ±0.89) Gy,and the maximum point dose varied from 0.98 Gy to 45.27 Gy,with the average of (17.42 ±13.20) Gy.Both the maximum point dose and the mean dose obviously varied among the patients,and their correlation was significant (R =0.527,P =0.000).Furthermore,no significant differences of the mean dose was found among the ages (P ＞ 0.05).The lifetime attribute risks of contra-lateral breast cancer were estimated to be 2 449,1 857,994,446,173 and 55 for per 100 thousand women corresponding to the ages of 35,40,50,60,70 and 80,respectively.Conclusions In the radiotherapy for unilateral breast cancer,the dose delivered to the contra-lateral breast is about 1 Gy order of magnitude,the risk of contra-lateral breast cancer cannot be ignored for young women.Therefore,the irradiation dose of contra-lateral breasts should be controlled as less as possible in planning the treatment.
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Objective To dosimetrically compare three delivery techniques of VMAT,IMRT and 3D-CRT in the treatment of accelerated partial breast irradiation (APBI).Methods Twenty patients with T1/2N0M0breast cancer were treated with VMAT.These cases were subsequently re-planned using static gantry IMRT and 3D-CRT technology to evaluate dosimetric differences.Dosimetric parameters including dose conformity index (CI),dose volume histogram (DVH) analysis of normal tissue coverage,dose parameters of PTV and normal tissues were evaluated,the delivery parameters including MU and delivery time were also analyzed.Results The IMRT and VMAT plans provided lower maximum dose,better mean dose and more conformal target dose distributions than the 3D-CRT plans (F =14.86,8.57,18.23,P ＜0.05).The volume of ipsilateral breast receiving 5 Gy for VMAT technique was significantly less than that of3D-CRTor IMRT(F=5.83,P＜0.05).The ipsilateral lung volume receiving 20 Gy (V20),5 Gy(V5) and the 5％ volume dose (D5) of IMRT were superior to those of 3D-CRT and VMAT(F =16.39,3.62,4.81,P ＜ 0.05).The low volume dose distributions of D5 in contralateral lung for IMRT was better than that of VMAT and 3D-CRT(F =3.99,3.43,P ＜ 0.05).The total mean MUs for VMAT,3D-CRT and IMRT were 621.0 ± 111.9,707.3 ± 130.9 and 1161.4 ± 315.6,respectively (F =31.30,P ＜ 0.05).The average machine delivery time was(1.5 ± 0.2)min for the VMAT plans,(7.0 ± 1.6)min for the 3D-CRT plans and (11.5 ± 1.9)min for the IMRT plans.Conclusions VMAT and IMRT techniques offer improved dose conformity as compared with 3D-CRT techniques without increasing dose to the ipsilateral lung.In terms of MU and delivery time,VMAT is more efficient for APBI than conventional 3D-CRT and static beam IMRT.
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Objective To investigate a new automatic inverse optimal solution based on VMAT optimization model and verify its result.Methods A variant of the new automatic inverse optimal solution was proposed in this study,which provided a solution to calculate treatment plan with the minimized number of beams and the minimized levels of their intensities on the basis of VMAT optimization model by customized software tools.The verifications were evaluated on the simulated head-neck phantom by dosimetric parameters.Results Compared with conventional IMRT/VMAT treatment plans,the adaptive optimization program(AOP)plan showed that plan20/40(20 fields with totally 40 sub-fields,m=2)made the best achievement and it was clinicable.Conclusions The proposed new optimization technique provides an effective way to reach an inverse treatment plan with the best compromise and less sub-fields compared with IMRT/VMAT plans.
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Objective To evaluate the feasibility and accuracy of performing dose calculation on megavoltage cone-beam CT(MVCBCT) in the head and neck. Methods MiniCTQC phantom was imaged using MVCBCT scanner, and the MVCBCT value density calibration curve was established. Conventional CT and MVCBCT image of phantom and nasopharyngeal carcinoma(NPC) patient were acquired respectively. Two kinds of single field plan were designed for conventional CT image of phantom,and IMRT plan was used for conventional CT image of a NPC patient. The conventional CT plans were copied to MVCBCT image. The dose distribution was calculated for targets and normal tissues using the MVCBCT value density calibration curve,and compared with that of conventional CT. Results For all the cases,the differences between the calculated dose distributions using MVCBCT and CT were less than 3% and 3 mm in single field plan. In IMRT plan, DVHs of conventional CT and MVCBCT were in excellent agreement. The biggest difference between conventional CT and MVCBCT was 95 cGy with the error of 1.4%. On the isocenter plane,the passing rate was 95.5% ,99.4% ,93.8% ,98.7%, 100% ,94.5% ,97.3% ,95.6% ,99.3% and 99.4% for the beam angle of 0°,45°,90°,120°,160°,200°,240°,280° and 320°. Conclusions Performing dose calculation using MVCBCT in head-and-neck region was feasible, and the dose distributions on the conventional CT and MVCBCT were in excellent agreement.