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Objective:To evaluate the application value of robost optimization of brachytherapy for cervical cancer.Methods:Twenty patients who completed radical treatment were recruited in this study. The dose volume histogram (DVH) parameters were statistically compared between the conventional and robust optimization plans, and the robustness between the conventional and robust optimization plans was evaluated using DVH and DVH bands. The robust optimization method utilized the worst dose distribution to consider the dose in the presence of uncertainties. In each optimization iteration, the dose distributin when the radioactive source shifted along the X, Y, and Z directions (±2 mm), and the dose distribution when the radioactive source was not shifted were calculated. The worst dose distribution for each voxel was the lowest dose in the target and the highest dose outside the target under all circumstances. The iterative objective function was calculated by the worst dose distribution.Results:In the scenario of no shifting of radioactive source position, the mean value of robust optimization was significantly lower and that of V 150% was significantly higher than those of conventional optimization (both P<0.05). When considering the shifting of radioactive source position, the worst dosimetric parameters of multiple dose distributions were statistically compared. The mean HR-CTV D 100% values did not significantly differ between the robust and conventional optimization plans, whereas the mean D 90% value (range: 0.02-0.03 Gy) of robust optimization was significantly higher than that of conventional optimization ( P<0.05). Robust optimization increased the D 2cm 3 of the bladder and small intestine, and the rectum dose was increased with the shifting of the radioactive source position in the robust optimization. The DVH bands did not significantly differ between the conventional and robust optimization plans for all patients. Conclusions:Robust optimization based on the worst dose distribution fails to significantly improve the robustness of brachytherapy for cervical cancer. Alternative methods are required to minimize the dosimetric effect of uncertainties in brachytherapy.
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Objective@#To report an implementation method and results of an independent brachytherapy dose verification software (DVS).@*Methods@#The DVS was developed based on Visual C+ + and the modular structure design was adopted. The DICOM RT files exported from the treatment planning system (TPS) were automatically loaded into the DVS. The TG-43 formalism was employed for dose calculation. Six cervical cancer patients who underwent brachytherapy were retrospectively selected to test the DVS. Different applicators were utilized for each patient. Dosimetric parameters and γ analysis (0.1cm, 5%) were used to evaluate the dose difference between the DVS and the TPS.@*Results@#Compared with the TPS dose, the γ pass rates of the doses calculated by the DVS were higher than 98%. For CTV, the dosimetric differences were less than 0.29% and 0.53% for D100% and D90%. For bladder, rectum and sigmoid, the agreement of D0.1cm3, D1cm3 and D2cm3 within a 0.5% level.@*Conclusion@#With minimal human-computer interactions, the DVS can verify the accuracy of dose calculated by TPS for brachytherapy.
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Objective@#To investigate the Offset values of different applicators in afterloading brachytherapy.@*Methods@#Six types of applicators were selected in this study which included stainless steel interstitial needle (Part#083.062), proguide round needle (Part#189.608), proguide sharp needle (Part#189.601), vaginal multi-channel applicator (Part#110.800), fletcher CT/MR applicator (Part#189.745) and henschke titanium applicator (Part#110.437). According to the sources imaging in the fluorography film, the distance of applicators between the first dwell position and the top could be measured. Marker was pasted on the surface of applicator corresponding to the first dwell position. And then the applicator was put into the pelvic phantom for a CT scan. During applicator reconstruction in the treatment planning system, the Offset values of all applicators could be acquired through adjusting the value of offset to superimpose the first dwell and the marker images. On account of the density of plastic material applicators were similar to human tissues, it was difficult to reconstruct the top of the applicator. With the help of stopper or simulation source, the value of offset could be acquired for plastic material applicators. Based on the measurement results, the differences were analyzed among different applicators.@*Results@#The Offset values significantly differed among various applicators. The Offset value for stainless steel interstitial needle was -11.4 mm, -4.1 mm for proguide round needle, -3.5 mm for proguide sharp needle, 0 mm or -5.0 mm for vaginal multi-channel applicator, -6.5 mm for fletcher CT/MR applicator and -7.5 mm for henschke titanium applicator, respectively.@*Conclusion@#To adapt to the rapid development of precise radiotherapy, it is necessary to verify the Offset value in afterloading brachytherapy.
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Objective@#To compare the dosimetric differences of volumetric modulated arc therapy (VMAT) plans optimized with 3 different fluence smoothing parameters using Monaco treatment planning system.@*Methods@#A total of 15 patients with middle and upper esophageal carcinoma were planned with Low fluence smoothing (Low), Medium fluence smoothing (Medium) and High fluence smoothing(High) during VMAT optimization. The dosimetric differences in D95, Dmean, conformity index (CI), homogeneity index (HI) of targets, dose volume histogram (DVH) of organs at risk (OARs), and monitor unit (MU) were compared.@*Results@#There were no significant differences in D95, Dmean, CI and HI of targets, as well as in V40 and Dmean of the heart, V10, V20 and Dmean of the lung , and segment number among plans optimized with different fluence smoothing techniques (P>0.05). Plans with high fluence smoothing achieved less V30 of heart, Dmax of cord PRV(t=-2.167, -0.999, P<0.05), lower MU (t=-3.148, -6.692, P<0.05), but increased V5 of both lungs (t=1.306, -2.027, P<0.05) compared with plans with Medium and Low fluence smoothing. Plans with low fluence smoothing irradiated higher dose to the V30 and Dmean to heart (t=0.411, 0.589, 0.013, P<0.05), but less V5 of the lungs (t=0.423, P<0.05) compared with plans with medium fluence smoothing.@*Conclusions@#All VMAT plans with 3 different fluence smoothing can meet the clinical requirements. VMAT plans optimized with high fluence smoothing are recommended in the treatment of patients middle and upper thoracic esophageal carcinoma.
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Objective:To explore an implementation method and results of an inverse dose optimization algorithm (gradient-based planning optimization, GBPO) in three-dimensional brachytherapy.Methods:A standard quadratic objective function was used in the GBPO. The optimization code of GBPO was performed based on LBFGS (Limited memory Broyden Fletcher Goldberg Shanno). Seven cervical cancer patients using different applicators and 15 cervical cancer patients using the Fletcher applicator (Nucletron part#189.730) were retrospectively analyzed. The plan quality of GBPO was firstly assessed by isodose lines, then dose-volume histogram (DVH) parameters of CTV(D 100%, V 150%) and organs at risk(D 0.1cm 3, D 1.0cm 3, D 2.0cm 3) were used to evaluate the difference among the GBPO, IPSA and Graphic plans. Results:For the 7 patients using different applicators, GBPO could optimize the conformal dose distribution, and the DVH parameters of the target and organs at risk were basically the same among the GBPO, IPSA and Graphic plans. For 15 patients using the Fletcher applicator, the difference in DVH parameters between the GBPO and IPSA plans was not statistically significant. There was no remarkable difference in the DVH parameters between the GBPO and Graphic plans, but the D 100% of the GBPO plan was significantly higher ( P<0.01), and the V 150% was significantly lower ( P<0.01) than that of the Graphic plan. Conclusions:The quality of the GBPO plan is similar to that of the IPSA plan in terms of target coverage and organ protection. The inverse dose optimization algorithm GBPO can be integrated into a three-dimensional brachytherapy treatment planning system.
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Objective To report an implementation method and results of an independent brachytherapy dose verification software (DVS).Methods The DVS was developed based on Visual C++ and the modular structure design was adopted.The DICOM RT files exported from the treatment planning system (TPS) were automatically loaded into the DVS.The TG-43 formalism was employed for dose calculation.Six cervical cancer patients who underwent brachytherapy were retrospectively selected to test the DVS.Different applicators were utilized for each patient.Dosimetric parameters and γ analysis (0.1 cm,5％) were used to evaluate the dose difference between the DVS and the TPS.Results Compared with the TPS dose,the γ pass rates of the doses calculated by the DVS were higher than 98％.For CTV,the dosimetric differences were less than 0.29％ and 0.53％ for D100％ and D90％.For bladder,rectum and sigmoid,the agreement of D0.1cm3,D1cm3 and D2cm3 within a 0.5％ level.Conclusion With minimal human-computer interactions,the DVS can verify the accuracy of dose calculated by TPS for brachytherapy.
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Objective To investigate the Offset values of different applicators in afterloading brachytherapy.Methods Six types of applicators were selected in this study which included stainless steel interstitial needle (Part#083.062),proguide round needle (Part#189.608),proguide sharp needle (Part# 189.601),vaginal multi-channel applicator (Part # 110.800),fletcher CT/MR applicator (Part # 189.745)and henschke titanium applicator (Part#110.437).According to the sources imaging in the fluorography film,the distance of applicators between the first dwell position and the top could be measured.Marker was pasted on the surface of applicator corresponding to the first dwell position.And then the applicator was put into the pelvic phantom for a CT scan.During applicator reconstruction in the treatment planning system,the Offset values of all applicators could be acquired through adjusting the value of offset to superimpose the first dwell and the marker images.On account of the density of plastic material applicators were similar to human tissues,it was difficult to reconstruct the top of the applicator.With the help of stopper or simulation source,the value of offset could be acquired for plastic material applicators.Based on the measurement results,the differences were analyzed among different applicators.Results The Offset values significantly differed among various applicators.The Offset value for stainless steel interstitial needle was-11.4 mm,-4.1 mm for proguide round needle,-3.5 mm for proguide sharp needle,0 mm or-5.0 mm for vaginal multi-channel applicator,-6.5 mm for fletcher CT/MR applicator and-7.5 mm for henschke titanium applicator,respectively.Conclusion To adapt to the rapid development of precise radiotherapy,it is necessary to verify the Offset value in afterloading brachytherapy.
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Objective:To report an implementation method and result of an inverse dose optimization algorithm (GBPO) that can control the dwell time variation in three-dimensional brachytherapy.Methods:The GBPO used a quadratic objective function. A dwell time modulation item was added to the objective function to restrict the dwell time variation, and a DTMF (dwell time modulation factor) was used to adjust the dwell time variation. A retrospective study was made of 15 cervical cancer patients treated using the Fletcher applicator. The relationship between the DTMF and dwell time deviation was analyzed. Dose-volume histogram (DVH) parameters of HR-CTV ( D100%, V150%) and organs at risk (OARs) ( D0.1 cm 3, D1 cm 3, D2 cm 3) were used to evaluate the difference between the GBPO plans and the commercial treatment plan system (using the IPSA algorithm) plans. Results:When the DTMF was less than 20, the dwell time deviation decreased quickly. However, after the DTMF increased to 100, and the dwell time deviation had no remarkable change. The D100% of GBPO plan was higher than that of IPSA plan (3.63±0.36 vs. 3.53±0.34, t=2.45, P<0.05), and the difference in other dosimetric parameters between the GBPO plans and the IPSA plans was not statistically significant ( P>0.05). Conclusions:The method reported in this study to control the dwell time variation was feasible. The GBPO plans have a comparable quality as the IPSA plans for the studied cervical cancer cases. The GBPO algorithm could be integrated into a three-dimensional brachytherapy treatment planning system.
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Objective To compare the dosimetric differences of volumetric modulated arc therapy (VMAT) plans optimized with 3 different fluence smoothing parameters using Monaco treatment planning system.Methods A total of 15 patients with middle and upper esophageal carcinoma were planned with Low fluence smoothing (Low),Medium fluence smoothing (Medium) and High fluence smoothing (High) during VMAT optimization.The dosimetric differences in D95,D conformity index (CI),homogeneity index (HI) of targets,dose volume histogram (DVH) of organs at risk (OARs),and monitor unit (MU) were compared.Results There were no significant differences in D95,D CI and HI of targets,as well as in V40 and D of the heart,V10,V20 and D of the lung,and segment number among plans optimized with different fluence smoothing techniques (P＞0.05).Plans with high fluence smoothing achieved less V30 of heart,Dmax of cord PRV (t=-2.167,-0.999,P＜0.05),lower MU (t=-3.148,-6.692,P＜O.05),but increased V5 of both lungs (t=1.306,-2.027,P＜O.05)compared with plans with Medium and Low fluence smoothing.Plans with low fluence smoothing irradiated higher dose to the V30 and D to heart (t=O.411,0.589,0.013,P＜0.05),but less V5 of the lungs (t=O.423,P＜0.05) compared with plans with medium fluence smoothing.Conclusions All VMAT plans with 3 different fluence smoothing can meet the clinical requirements.VMAT plans optimized with high fluence smoothing are recommended in the treatment of patients middle and upper thoracic esophageal carcinoma.
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Objective To investigate the application value of a transmission reference stealth ionization chamber in the relative dosimetry of stereotactic radiotherapy.Methods The relative dosage of Varian (R) Novalis 6 MV photon rays equipped with Brainlab (R) conical applicators was determined by two different approaches in the IBA (R) Blue Phantom.One approach was designed to utilize IBA (R) SFD3G semiconductor ionization chamber alone in the "step by step" measurement mode,whereas the other method was to utilize IBA (R) SFD as the field detector combined with stealth ionization chamber as the reference detector in the "continuous" measurement mode.The central axial percentage depth dose (PDD) and off axis ratio (OAR) in a diameter of 4 and 15 mm were measured and the time spent on each measurement was recorded.Results The PDDs at the central axis and OARs at a depth of 10 cm for both conical applicators were in good agreement between the two measurement approaches with a dose difference of＜ 1％.The time spent on PDDs and OARs measurement with stealth ionization chamber was shortened by 13.1％ and 20.7％ compared with those without Stealth ionization chamber.Conclusion Stealth ionization chamber can be applied in the retative dosimetry of stereotactic radiotherapy with high dose accuracy and high efficiency.
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Objective To investigate effect of stanniocalcin-1 (STC1) gene on the proliferation,apoptosis and radiotherapy sensitivity of non-small cell lung cancer.Methods The STC1 siRNA (STC 1-siRNA) and the non-interfering siRNA (negative control group) were transfected into the human lung cancer A549 cells by LipofectamineTM2000,and the blank control group was established.The expression level of STC1 protein was detected after transfection for 48 h by Western blotting.Clone forming test was adopted to detect the proliferation of A549 cells after STC1-siRNA and irradiation treatment.CCK8 assay was performed to detect the cell viability after treatment with STC1-siRNA and STC1-siRNA+8 Gy.The cell apoptosis was detected by flow cytometry.The expression levels of Ki67,Bax,STAT3 and p-STAT3 proteins were quantitatively measured by Western blotting.Results The expression level of STC1 protein in the A549 cells transfected with STC1-siRNA was significantly down-regulated than that in the blank control group (P＜ 0.05).Compared with the blank control group,the sensitization ratio was significantly enhanced after STC1-siRNA transfection.Compared with the blank control group,the cell viability and the expression levels of Ki67 and p-STAT3 protein were significantly decreased,whereas the apoptosis rate and the expression of Bax protein were significantly increased in the STC1-siRNA group.Compared with the STC1-siRNA group,the cell viability and the expression levels of Ki67 and p-STAT3 proteins were significantly decreased,whereas the cell apoptosis rate and the expression of Bax protein were remarkably increased in the STC1-siRNA+ 8 Gy group (all P＜0.05).Conclusion Inhibition of STC1 gene expression can enhance the radiotherapy sensitivity and down-regulate the STAT3 signaling pathway in non-small cell lung cancer.
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Objective To evaluate the effect of stainless steel applicator on dose distribution in GZP 60 Co brachytherapy source and to obtain the dosimetric parameters of the 60 Co source with stainless steel applicator. Methods Geant4 was employed to obtain the mean adsorption dose of the 60 Co brachytherapy source in the range of 0-10 cm, and the dosimetric parameters were calculated according to the formula proposed by AAPM reports TG43 and TG43U1. The 60 Co source was located in the center of a sphere water phantom with a radius of 30 cm. Results For channel 1 and 2 of GZP 60 Co source, the results of Λ with stainless steel applicator were 1. 014 cGyh-1 U-1( with a difference of 0. 5％ compared with non-applicator) , the results of Λ with stainless steel applicator for channel 3 were 0. 998 cGyh-1 U-1 ( with a difference of 0. 1％ compared with non-applicator) . The radial dose function in the range of 0. 5-10. 0 cm in a longitudinal direction was calculated and the fitting formula for the function was obtained. The polynomial function for the radial dose function and the anisotropy function with a of 0°-175° and an r of 0. 5-10. 0 cm were obtained. Conclusion The dosimetric parameters of the 60 Co source with stainless steel applicator are obtained, which provide more accurate reference data for clinical application. In clinical practice, the effect of stainless steel applicator on dose distribution should be considered.
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Objective To compare dosimetric parameters between automated and manualvolumetric modulated arc therapy(VMAT) plans in the treatment of postoperative cervical cancer patients,and to investigatethe feasibility and dosimetric advantage of the automated VMAT planning.Methods Automated and manual VMAT plans were generated with Pinnacle3 treatment planning system (TPS) for twenty-three postoperative cervical cancer patients,including eight patients in stage Ⅱ A and fifteen in stage Ⅱ B,respectively.The differences in D D95,conformity index (CI) and homogeneity index (HI) of target,as well as dose volume histogram (DVH) of organs at risk (OAR),planning time,average optimization time and monitor unit (MU) were compared between automated and manual VMAT plans.Results The average D CI and HI of automated VMAT plans were better than those of manual VMAT plans (t=4.65-14.92,P ＜0.05).There was no significant difference in D95 (P ＞0.05).The automated VMAT plans achieved better average dosimetric parameters on OARs compared with the manual VMAT plans (t =3.30-14.42,P ＜ 0.05).Automated VMAT plans had a significantly shorter planning time (72 min,t =3.85,P ＜ 0.05) and interruption frequency (twice,t =5.41,P ＜ 0.05) than manual VMAT plans.However,automated VMAT plans had a higher average MU than manual VMAT plans with an average MU of 819 ± 53 and 638 ± 41 for automated and manual VMAT plans,respectively.Conclusions It is feasible to generate automated VMAT plans with Pinnacle3 TPS for postoperative cervical cancer patients.The automated VMAT plans increase the plan quality and reduce the optimization time compare with manual VMAT plans.Automated technique also eliminates the influence of human factors on the plan quality.
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Objective To investigate the dosimetric influence of dwell weight standard deviation (DWSD) and applicator displacement in cervical cancer patients treated with three-dimensional brachytherapy.Methods A total of 20 cervical cancer patients who had completed radical treatment were selected in this study.The Fletcher applicator (Nucletron#189.730) was used for these patients.A new plan,based on the former CT images and structures,was designed for each patient.In former and new plans,dwell weight was recorded,and DWSD was calculated.Two groups,low-DWSD (LDWSD,0.141-0.299) and high-DWSD (HDWSD,0.211-0.337),were set according to the DWSD size for the two plans.Dosimetric effects from ± 1 mm displacement of tandem applicator or ovoid applicator were simulated with Oncentra (R) Brachy V4.3 treatment planning system.D100,D90,and V150 for clinical target volume (CTV)and D0.1cc,D1cc,and D2cc for the bladder,rectum,and sigmoid were evaluated.Dosimetric comparisons were made between the LDWSD group and HDWSD group to study the dosimetric effects of DWSD and applicator displacement in cervical cancer patients.Results The dosimetric effects from applicator displacement increased with increasing DWSD.If there was a 1 mm displacement of tandem applicator or ovoid applicator,D100,D90,and V150 of CTV were 3.0％,23.8％,and 4.8％ higher or 0.5％,1.2％,and 5.2％ higher in the HDWSD group than in the LDWSD group;D0.1cc,D1cc,and D2cc of the bladder and rectum were significantly higher in the HDWSD group than in the LDWSD group,particularly for the sigmoid (up 44.0％,22.8％,and 16.8％) and (up 10.3％,14.4％,and 12.4％).Conclusions DWSD should be considered in plan evaluation for cervical cancer patients treated with three-dimensional brachytherapy.The dosimetric influence from applicator displacement can be decreased by reducing DWSD properly.
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Objective To explore the elementary properties of LiF (Mg,Cu,and P) thermoluminescent dosimeter (TLD) in dosimetry for tumor radiotherapy,and to provide a reliable basis for thermoluminescent dosimetry in clinical radiotherapy.Methods 60Coγ-ray and 6 MV X-ray were used for evaluation of the dispersion,repeatability,and dose response of LiF TLD.To meet the requirement of clinical radiotherapy,the effects of energy,dose (50-600 cGy),radiation dose rate (50-600 MU/min),and the angle of incidence for accelerator gantry (0°-± 90°) on TLD were determined and the respective correction factors were calculated.Results The errors of repeatability and dispersion of TLD were less than ±3％.There was a linear relationship between readout and irradiation dose within a certain range of irradiation dose.The minimal relative deviation of 0.3％ was obtained when 6 MV X-ray was used with a dose rate of 300 MU/min and an angle of incidence of 0°.Conclusions LiF TLD shows excellent repeatability,low dispersion,high stability,and strong linear correlation.It meets the international criteria and can be used for dose measurement in tumor radiotherapy.
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Objective To investigate the feasibility of the virtual source model in Monte Carlo dose calculation for clinical radiotherapy.Methods The Monte Carlo simulation was used to obtain the phase space files which recorded the physical properties of the particles emitted by a medical linear accelerator, and the information on the type, energy spectrum, and distribution of particles were extracted from these files and analyzed to establish the semi-empirical model of virtual two-photon source.The GMC dose calculation engine was used to obtain the 3 cm×3 cm, 5 cm×5 cm, 10 cm×10 cm, 20 cm×20 cm, and 30 cm×30 cm fields of radiotherapy and the results of Monte Carlo simulation of dose distribution in three-dimensional water phantom in 2 intensity-modulated radiotherapy ( IMRT) plans.These results were compared with the results of water phantom measurement or the results of Elekta Monaco planning system to verify the accuracy of Monte Carlo dose calculation based on a virtual source.Results As for the percentage depth-dose distribution curves of the central axis of the water phantom and the off-axis dose curves at different depths in the five fields for radiotherapy, the difference between the results of Monte Carlo simulation and the results of measurement was within 1%.As for the two IMRT plans, the three-dimensional passing rates of Monaco calculation results and Monte Carlo simulation results were 98.9%and 99.4%, respectively, for 3%/3 mm, and 95.1%and 95.4%, respectively, for 2%/2 mm.Conclusions Monte Carlo simulation based on the virtual source model can obtain accurate results of radiotherapy dose calculation.
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Objective To develop double-arc volumetric modulated arc therapy ( VMAT) plans using standard phantom and standard target volume in AAPM119 report, and to investigate the dosimetric parameters of Agility and MLCi2 leafs according to the requirements for target dose in AAPM119 report. Methods The Cshape, Head and Neck, Prostate, and Multitarget structures for standard target volume delineation in AAPM119 report were used.The Elekta Agility multi-leaf collimator was used to develop plans, and then with other parameters remaining unchanged, Elekta MLCi2 was used for plan optimization and dose calculation.The target dose in AAPM119 report was used as the standard to analyze the differences in target volume and dose-volume parameters of organs at risk between the four structures for target volume delineation.Results According to the mean dose in AAPM119 report, in the Cshape, Head and Neck, and Multitarget target volumes, the radiotherapy plans developed with Agility had better dosimetric parameters compared with those developed with MLCi2.In the prostate target volume, the radiotherapy plans developed with MLCi 2 had better dosimetric parameters compared with those developed with Agility .Conclusions With the structures for target volume delineation, plan designing personnel, designing parameters, and evaluation criteria remaining the same, Elekta Agility can achieve the dose target better than Elekta MLCi2 in the aspect of strict dose limit.
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Objective To investigate the dose and mechanical properties of medical electron linear accelerators in grass-roots radiotherapy units in Sichuan Province,China via sampling and inspection.Methods A total of eight radiotherapy units in Sichuan Province were selected by sampling,and the tests were performed for the dose and mechanical properties of the medical electron linear accelerators in use.Among these accelerators,there were 5 imported accelerators and 3 domestic accelerators.The test items and methods were determined according to the requirements in GB15213-94.Results Among the 14 test items,the items related to the flatness,symmetry,and overlap of radiation field.The other tests of dose accuracy and mechanical precision achieved good results.Conclusions There is a need to strengthen the daily quality control work for dose and mechanical accuracy of medical electron linear accelerators in grass-roots radiotherapy units in Sichuan Province and perfect the allocation of professional equipment and personnel and training of related personnel.With the support of Sichuan Radiotherapy Quality Control Center,quality control supervision and guidance should cover the whole province.
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Objective To understand the status of the radiation therapy in sichuan province, analysis the development level of radiotherapy in the past five years in sichuan province,provide reference for the rational allocation of radiotherapy resources in the province, promote the healthy development of radiotherapy. Methods With reference to the surveys carried out by other provinces and the survey of sichuan province in 2009,to determine the survey schemes,survey projects. The survey covers all medical units of radiation therapy in the province, adopt the way of combination of questionnaire and on?the?spot visiting. Results There is a big progress in basic condition, treatment equipment, auxiliary equipment, verification equipment,personnel and application of new technologies. Compared with 2009 survey,multiple projects achieve a 50% or even more than 100% growth. Conclusions The rapid development of radiation oncology in sichuan province will ultimately benefit a large number of tumor patients in sichuan province. Patients will be treated with better environment,treatment technology and quality. At the same time,higher requirement of quality control for the entire province is put forward to us.
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Objective To study the impact of setup error caused by computed tomography ( CT) images with different resolutions in the Sentinel system on clinical treatment. Methods A phantom was scanned by large?aperture positioning CT with two different resolutions ( CT1:0. 5 mm × 0. 5 mm × 1. 0 mm, FOV 256 mm, Matrix 512, thickness 1 mm;CT3:1. 0 mm×1. 0 mm×3. 0 mm, FOV 500 mm, Matrix 512, thickness 3 mm) . The CT images were transferred to the planning system. The radiation fields were designed and transferred to MOSAIQ and Sentinel systems. Ten fixed setup errors were applied to a six degree of freedom couch. The Sentinel system was used to position the two groups of CT images and generate the setup errors. The comparison of two datasets was made by paired t?test. Cone?beam CT was used for independent verification. Results The setup errors in x?, y?, and z?directions were significantly smaller on CT1 than on CT3(0.19±0. 11 vs. 0.33±0. 16 mm, P=0. 061;0.59±0. 79 vs. 1.07±1. 09 mm, P=0. 008;0.67±0. 75 vs. 1.16±1. 30 mm, P=0. 043). There were no significant differences in rotational errors in x?, y?, or z?directions between the two datasets ( P=0. 494;P=0. 182;P=0. 298) . Conclusions The Sentinel system has a higher setup accuracy in the 0. 5 mm×0. 5 mm×1. 0 mm mode than in the 1. 0 mm×1. 0 mm×3. 0 mm mode. However, the later mode is still an acceptable choice in clinical treatment.