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Objective To explore the dose of template-assisted 192Ir source hypofractionated stereotactic brachytherapy (SABT) for peripheral lung cancer. Methods We retrospectively analyzed the dose parameters of GTV and OARs of 28 peripheral lung cancer patients treated with template-assisted 192Ir-source hypofractionated SABT, and compared the dose parameters between SABT with virtual SBRT. Results The Dmean and V150 for the GTV in the SABT plan were significantly higher than those in the SBRT plan (all P < 0.01). For OARs, all dosimetric parameters in the SABT plan were significantly lower than those in the SBRT plan (all P < 0.01), except for the D1000cm3 and D1500cm3 for the lung (P > 0.05). Conclusion Template-assisted 192Ir source hypofractionated SABT ensures high dose in the gross tumor volume and reduces the dose in organs at risk in the treatment of peripheral lung cancer.
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Objective:To compare the calculation result and analyzes the reasons for their differences so as to provide reference for the revision and improvement of the current national standards on radiation shielding design for the room of brachytherapy.Methods:For the initial activity 10 Ci (1 Ci=3.7×10 10 Bq) of radioactive sources, the shielding schemes of brachytherapy room were designed in accordance with UK Institnte of Physics and Engineering in Medicine(IPEM) Report 75, USA NCRP Report 151 and the national standard GBZ/T 201.3-2014, respectively. The differences in shielding limits, occupancy factors and other relevant factors are compared in detail. Results:The annual exposure time in a typical brachytherpy room was about 330 h. The point-specific concrete thickness were 70, 65, 61, 70, 50 cm as required by NCRP Report 151, 41, 43, 30, 40, 39 cm by IREM regulations and 84, 79, 46, 88, 39 cm by GBZ/T 201.3, respectively. The concerned concrete shielding thickness calculated under the GBZ/T 201.3-2014 was generally thicker, with lesser difference from NCRP Report 151 result, whereas that from the IPEM75 report was thinnest. The equivalent lead shielding thicknesses of the protective doors calculated using the three method are 1.170, 0.854 and 1.040 cm, respectively.Conclusions:The shielding thickness calculated using the calculation method and evaluation index recommended by the current Chinese shielding standards for brachytherapy bunker is similar to that reported in NCRP151, but is conservative. In particular, the evaluation index of instantaneous dose equivalent rate required by the current national standards and the relative conservative value of occupancy factor will significantly increase the shielding thickness required by the main shielding area.
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Objective:To evaluate the impacts of tissue heterogeneity on dose calculation of cervical brachytherapy by comparing the doses calculated by two clinically used dose calculation method and the CT image-based Monte Carlo (MC) method.Methods:This study retrospectively selected 11 patients with cervical cancer treated with 3D brachytherapy in Anhui Provincial Cancer Hospital from January 2018 to June 2020. The dose distribution of each plan was calculated via three methods, dose calculation method described in American Association of Physicist in Medicine(AAPM) Task Group No. 43 Report (TG43-BT), Acuros BV(BV-BT) used to perform accurate dose calculations in high-dose-rate (HDR) brachytherapy with phantom heterogeneity, and CT image-based EGSnrc tool kit used to perform Monte Carlosimulation (MC-BT). The dose volumes( V3 Gy, V6 Gy, V9 Gy, and V12 Gy), target volume doses( D98, D90, D50), D2 cm 3 of organs at risk (OARs) calculated by the three methods were compared. Results:The HRCTV D90obtained by TG43-BT was 6.274 Gy, which was even overestimated by around 5% compared to the result calculated by MC-BT. Meanwhile, TG43-BT overestimated the dose volumesand the target volume doses compared to MC-BT.Except for D50 and V12 Gy, the differences between the doses to tumor calculated by BV-BT and MC-BT were not statistically significant( P>0.05). There was also no significant statistical difference between the D2 cm 3 of rectum, small intestine, and sigmoid calculated by BV-BT and MC-BT ( P>0.05). In contrast, the dose to D2 cm 3 of bladder determined by MC-BT was 4.609 Gy, which was notably higher than those deter mined by TG43-BT and BV-BT. Conclusions:TG43-BT overestimated the doses to tumor targets and most OARs since the effects of tissue heterogeneity were not taken into consideration. BV-BT performed efficient calculation and most of the dose distributionin target volume and OARs obtained by BV-BT were consistent with that calculated by MC-BT. Nevertheless, low accuracy occurred for the regions near the sources and full bladder, which warrants further caution in clinical evaluation.
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Objective@#To explore the treatment technique, occurrence and development patterns of such radiation injuries as in a major radiological accident in which a victim suffered mild bone marrow radiation sickness combined grade degree Ⅲ acute radiation induced skin injury, based on his dose estimation, clinical manifestations and disease treatments.@*Methods@#History inquiry in detail, earlier physical dose estimation and biological dose estimation were conducted in conjunction with analyzing the chromosome aberration of peripheral blood lymphocytes. The physical dose was estimated by Monte Carlo method.The systematic laboratory and imaging examination was performed to evaluate the condition. The comprehensive analysis was conducted to determine the diagnosis and treatment plan.@*Results@#At 3d after the exposure, "Ren" felt mild pain and discomfortable on the skin of the right index finger. The body of the right hand index finger was covered with blister at 21 d after exposure.The estimation of biological dose was 0.43 Gy (95%CI: 0.31-0.58 Gy), and the physical dose was estimated to be 36-164 Gy for each part of the right hand finger. The hematopoietic system, immune system and endocrine system were normal. The liver function index value was transiently increased. The liver damage resulted from the use of antibiotic-induced combined with the patient′s past medical history and admission examination result, and the relevant antibiotics were discontinued. The liver function returned to normal after liver protection treatment. At 22 d after irradiation, a right finger incision and decompression surgery were performed. The stem cells were extracted and implanted into the right index finger. After 59 days of hospitalization, there was no obvious discomfort in the body, and the right index finger recovered well, as well as the pain significantly relieved, and the knuckle activity was basically normal.@*Conclusions@#The patient with excessive radiation and grade Ⅲ acute radiation skin injury was successfully treated, and local application of autologous adipose-derived stem cell transplantation achieved good result .
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Objective@#To investigate the efficacy and feasibility of 192Ir high-dose rate brachytherapy for recurrent intrapulmonary oligometastasis after colorectal cancer surgery.@*Methods@#Patients from May 2013 to October 2017 with intrapulmonary oligometastasisafter colorectal cancer surgery in Cangzhou Integrated Traditional Chinese and Western Medicine Hospital were enrolled. A total of 15 lesions were obtained from 10 patients, which were treated with CT-guided high dose rate of 192Ir. The implant needles were inserted into the tumor and were adjusted to appropriate positions under the guidance of CT. Then the images after transplanting were uploaded to the planning system to delineate the target area and the organ at risk volume. Patients underwent a single radiation dose of 20 Gy.@*Results@#All 10 patients were successfully treated. Grade 1 adverse events were observed for 30% of patients. Of the 10 patients, one patient had a mild cough, and two had bloody sputum. There was no serious adverse events occurred. The local control rate (LC) of the patients at 1 year after treatment was achieved in 93.3%. Only one developed local advancement after six months, who received the secondary brachytherapy. The median progression-free survival(PFS) was 8.5 months and the median overall survival(OS) was 14.7 months.@*Conclusions@#High dose rate brachytherapy is effective in terms of recurrent lung metastases after surgery for colorectal cancer, with a moderate rate of adverse reactions and a favorable local tumor control rate.
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Objective To study the dosimetric parameters of Varian GammaMed Plus HDR 192 Ir source via Monte Carlo ( MC ) method based on the recommendation of the American Association of Physicist in Medicine ( AAPM) and European Society for Radiotherapy and Oncology ( ESTRO) . Methods Using the Monte Carlo program EGSnrc, an accurate model of 192 Ir source for MC calculations was establish firstly. Through formula derivation, bilinear interpolation and unit conversion, the air kerma strength per unit source activity, the dose rate constant, radial dose function and anisotropy function was obtained then , and compare the result with those in other published studies. Results The air kerma strength per unit source activity was 9. 781 × 10-8 U/Bq. The dose rate constant was 1. 113 cGy · h-1 · U-1 , with a discrepancy of less than 0. 4％ compared with result published in other works. Furthermore, the curves of radial dose function and anisotropy function overall agree with the data shown in the literature. Conclusions The feasibility of performing dosimetric studies of 192 Ir source using the MC software EGSnrc was demonstrated. This work provides a theoretical guidance on analysis of the dose distribution of brachytherapy and on evaluation of the dose accuracy of clinical radiotherapy.
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Objective To investigate the late effects induced by ionizing radiation and the rehabilitation treatment of local radiation injury by medical follow-up of the patient exposed to192 Ir at 5.7 accident in Nanjing,and to provide more experience for the treatments in the medical emergency of nuclear or radiological accident.Methods According to the history inquiry and physical examination of the patient in detail and the record of clinical symptoms and signs,the changes of the blood system,immune system,reproductive system,eyes,nervous system were systematically evaluated.The effects of rehabilitation treatment for the patient with lower limb dysfunction were also assessed.Results After the medical treatments of the patient,the hematopoietic immune system was restored,but the bone marrow aspiration still showed low bone marrow hyperplasia in right ilium.Meanwhile,the level of sex hormones was within the normal range,but semen examination showed sperm motility was 0.The radiation damage also occurred in the eye lens,retina and fundus.Howevcr,the psychological evaluation showed that the patient was stable and the right lower limb skin wound healing was well except for dysfunction and pain in some extent,which was relieved after the rehabilitation treatment.Conclusions The physiological function of the exposed victim with mild bone marrow type acute radiation sickness could be completely or partially restored after the clinical treatment in the early stage.
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Abstract Objective: To perform a comparative dosimetric analysis, based on computer simulations, of temporary balloon implants with 99mTc and balloon brachytherapy with high-dose-rate (HDR) 192Ir, as boosts to radiotherapy. We hypothesized that the two techniques would produce equivalent doses under pre-established conditions of activity and exposure time. Materials and Methods: Simulations of implants with 99mTc-filled and HDR 192Ir-filled balloons were performed with the Siscodes/MCNP5, modeling in voxels a magnetic resonance imaging set related to a young female. Spatial dose rate distributions were determined. In the dosimetric analysis of the protocols, the exposure time and the level of activity required were specified. Results: The 99mTc balloon presented a weighted dose rate in the tumor bed of 0.428 cGy.h-1.mCi-1 and 0.190 cGyh-1.mCi-1 at the balloon surface and at 8-10 mm from the surface, respectively, compared with 0.499 and 0.150 cGyh-1.mCi-1, respectively, for the HDR 192Ir balloon. An exposure time of 24 hours was required for the 99mTc balloon to produce a boost of 10.14 Gy with 1.0 Ci, whereas only 24 minutes with 10.0 Ci segments were required for the HDR 192Ir balloon to produce a boost of 5.14 Gy at the same reference point, or 10.28 Gy in two 24-minutes fractions. Conclusion: Temporary 99mTc balloon implantation is an attractive option for adjuvant radiotherapy in breast cancer, because of its availability, economic viability, and similar dosimetry in comparison with the use of HDR 192Ir balloon implantation, which is the current standard in clinical practice.
Resumo Objetivo: Análise dosimétrica comparativa entre técnicas de implantes temporários de reforço por meio de balões de 99mTc e de 192Ir de alta taxa de dose (high dose rate - HDR) mediante simulação computacional. A hipótese é que ambos produzem dosimetria equivalente em condições pré-estabelecidas de atividade e exposição. Materiais e Métodos: Simulações de implantes com balão preenchido com 99mTc e balão HDR-192Ir foram elaboradas no Siscodes/ MCNP5, modelando em voxels um tórax feminino reproduzido de ressonância magnética de mama jovem. Distribuições espaciais de taxas de dose absorvidas foram geradas. Análises dosimétricas dos protocolos foram apresentadas especificando tempo acumulado e atividade requerida. Resultados: Implante temporário com balão-99mTc apresentou taxa de dose ponderada no leito do tumor, na adjacência do balão, de 0,428 cGyh-1.mCi-1, e a 8-10 mm distante, de 0,190 cGyh-1.mCi-1, enquanto o implante de balão com 192Ir apresentou 0,499 e 0,150 cGyh-1.mCi-1, respectivamente. A exposição de 24 horas para balão-99mTc foi necessária para produzir o reforço de 10,14 Gy com 1,0 Ci, ao passo que para balão HDR-192Ir foram necessários 24 minutos com segmentos de 10,0 Ci para gerar 5,14 Gy no mesmo ponto de referência, ou 10,28 Gy em duas frações de 24 minutos. Conclusão: Implante temporário com balão-99mTc é atrativo para a radioterapia adjuvante do câncer de mama, devido a disponibilidade, viabilidade econômica e equivalência radiodosimétrica ao balão HDR-192Ir, protocolo presente na prática clínica.
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Objective To provide nutritional supportive scheme for patients with radiation injury through the treatment of the one exposed to Nanjing 192Ir source accident.Methods The reasonable nutrition treatment scheme was made on the basis of dietary survey and nutritional index monitoring during clinical stages of the patient,including body weight,body mass index(BMI),biochemical indexes,electrolyte,etc.,as well as metabolic cart determination of resting energy expenditure (REE).Results Patient on admission (days 5 post-irradiated) weighing 42.5 kg,172 days after the first irradiated (the first skin grafting) fell to a minimum of 36 kg,then gradually rise,hen rose back to normal range on days 383 before discharge.Normal admission hemoglobin was 135 g/L,172 d after irradiated to a minimum of 54 g/L,normal discharge;when lymphocytes admission low as 0.5 × 109/L,58 days back to normal after exposure,172 days after irradiated down to 0.4 × 109/L.Serum albumin was normal admission 41.2 g/L,172 days after irradiated down to 25.3 g/L.The normal level of serum prealbumin was 0.22 g/L,248 days to a minimum of 0.04 g/L,the basic return to normal at discharge was 0.17 g/L.Admission normal liver function,bilirubin index slightly higher,the all in one parenteral nutrition after about 2.5 months later,bilirubin and liver function indicators were gradually increased,the adjusted treatment and nutrition liver and gallbladder and other gradually returned to normal after treatment.REE and the body weight were determined by metabolic cart on days 294,308 and 342 for the energy requirements.Conclusions For patient with radiation injury,appropriate nutrition therapy is a key method for the clinical treatment and rehabilitation,which can maintain the nutritional status of patients and improve clinical treatment.
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Objective To make a summary of radiation-induced changes in ocular lens and retinal lesions based on dynamic follow-up of a patient exposed to a radiation exposure from 192 Ir source accident,in order to provide the information and experience for the clinical diagnosis and treatment of such injury in emergency of a nuclear or radiation accident.Methods The examination methods included eye lens and visual acuity,slit-lamp examination,fundus examination,automated perimetry,optical coherence tomography (OCT) examination,fundus photography,and fundus fluorescein angiography (FFA).The patient was followed-up for 20 months.Comparative analyses were made of the follow-up results.Results One month after 192Ir radiation exposure,the visual acuities in both eyes were 1.0.Mild age-related opacities were observed in peripheral cortex,but the fundus looked normal.Twenty months later,the patient was followed-up.The visual acuities reduced to about 0.6,evident powder-and punctuate-like opacities could be observed in the cortex of the right lens,and mild turbid foci in the posterior polar and capsule.Multiple scotomata appeared in the superior temporal and inferior nasal in the right eye.The macular fovea thickness was not changed significantly in the right eye.Examination with fundus photography demonstrated mild optical nerve atrophy,drusens,and pale optic discs,while FFA examination showed punctuate or flocculent leakages in both eyes.Conclusions The lens opacity could be induced or accelerated by radiation exposure.In addition to the posterior capsule and pole cataracts,punctuate opacity within cortical layer may also occur.It also suggests that cataract and fundus injuries may occur later during long-term follow-up,even though the eyes may look normal during early examination after the patient exposed to the radiation.
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Objective To explore the natural attenuation pattern of three biological dose estimation indexes in vivo by investigating the effect on biological dosimetry of peripheral blood sampling at different time points from the victim partially exposed to 192Ir radiation source at5.7 accident in Nanjing.Methods Peripheral blood of the patient was collected on days 5,40 and 280 after exposure,respectively.The yields of dicentrics plus rings chromosomes (dic + r),cytokinesis-block micronuclei (CBMN) and nucleoplasmic bridge + fusion + horse shoe + circular(NPB + FHC) were analyzed.The dynamic reduction and dose estimation were both observed using the biomarkers mentioned above after exposure.Results Compared to the estimates on days 5 after exposure,the dose values estimated on days 40 and 280 decreased by 34％ and 49％ fordic + r method,48％ and 79％ for the CBMN assay,and 48％ and 75％ for NPN + FHC method,respectively.Conclusions Three biological dose estimation indexes show a progressive decrease in vivo,with the half-life of dic + r/cell being 40 days.The doses estimated using these three indexes on days 40 after exposure showed a relative deviation more than 20％ compared with those on days 5 after exposure.
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Objective To use three different methods in attempt to estimate the biological dose of the patient partially exposed to 192Ir source at5.7 accident in Nanjing,so as to provide dosimetric information for clinical remedy of exposed patients in the emergency of a nuclear accident.Methods Peripheral blood samples were collected on days 5 after exposure.The biological dose was estimated by the yields of dicentrics plus rings ( dic + r),cytokinesis-block micronuclei (CBMN) assay and nucleoplasmic bridge plus FHC (NPB + FHC).The homogeneity of radiation exposure was examined by Poisson distribution of dicentrics.Results By using three different methods,the whole body equivalent dose was dic + r estimated to be 1.51 Gy (95％ CI 1.40-1.61),1.47 Gy (95％ CI 1.36-1.60) by CBMN and 1.30 Gy (95％ CI 1.00-1.60) by NPB + FHC,respectively.A non-poisson distribution was also detected,suggesting partial body radiation exposure.Conclusions The estimated whole body equivalent dose ot a non-uniform radiation exposure was consistent with clinical diagnosis,suggesting that the yields ofdic + r,CBMN,as well as NPB + FHC,are efficient approaches to the estimation of biological doses.
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Objective To make a rapid dose estimation for a patient exposed locally to high dose radiation exposure in early stage of 5.7 192Ir source accident in Nanjing.Methods Based on source parameters,exposure pattern,and time duration,the doses were estimated using MCNP simulations with the aid of the proper East Asia adult male voxel phantom and main physiological parameters of the exposed patient.Result Absorbed doses to 16 organs or tissues were estimated to be in the range 0.03 to 9.16 Gy.Also,the iso-dose curves for the skin of legs showed clearly the dose difference between right and left legs.Absorbed doses to patient's testicles and prostrate,about 9.16 Gy,were higher than those to other organs or tissues.The skin of both legs was exposed locally to high dose radiation exposure,for which the estimated doses were in agreement with the results obtained from infrared thermal imaging.Conclusions Monte Carlo simulation technique and common software can be used for dose estimation in early stage of radiation accidents effectively with integrating proper models.
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Objective To study the method of measuring the position accuracy and the step distance accuracy of afterloading system with192Ir source by using flushing-free film.Methods The position accuracy and the step distance accuracy of a China-made afterloading system with192Ir source was measured by using GAFCHROMIC (R) EBT3 flushing-free film.The film was scanned to proper image format,required by dose analysis software,by EPSON PREFACTION V700 PHOTO scanner.Then images are analyzed by using film dose analysis software in SNC Patient 5.2.Results With focus on the center of active section of source,the position accuracy of this afterloading system with192Ir source was-0.75 mm.Using film analysis could make the step point to tell apart if the step distance was 5 mm away by the method of film analysis,but couldnot make it to tell apart if the step distance was 2.5 mm away.The 2.5 mm step distance accuracy could be judged if the distance between the 1 st point and the 3rd point was 5 mm,then the 2.5 mm step distance could be deemed to no deviation.The 5 mm step distance of this afterloading system had no deviation in continuous 9 step points measured by flushing-free film.The indirect measuring results of the 2.5 mm step distance had no deviation as well.The position accuracy of this afterloading system measured with the flushing-free film accorded with the national standards.Conclusions The method of measuring the position accuracy and the step distance accuracy of the afterloading system with192Ir source by using flushing-free film is technically feasible.
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Objective To study the method of measuring air kerma strength of afterloading units with 192Ir source by using well type ionization chamber.MethodsThe air kerma strength of 30 afterloading units with 192Ir source was measured using 2000A electrometer and 1000 plus well type ionization chamber,and apparent activity of the source was calculated with the air kerma strength and apparent activity conversion factor.The measured activity of the source was compared with the original value of the source provided by the manufacturer,and the relevant deviation should be within ± 5%.Results Theair kerma strength of afterloding units with 192Ir sources was tested.The relevant deviation of the measured activity and the original value was within -0.1%-4.4%.Conclusions The measurement method with a well type ionization chamber is convenient and highly accurate which can be used for the test of quality control in hospitals.
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Objective To facilitate activity measurement by using the thimble ionization chamber in hospitals,to obtain air kerma scatter correction factor of medical afterloading of 192Ir source by developing an available and convenient calculation method.Methods According to International Atomic Energy Agency (IAEA) 1079 Report to calculate the scatter correction factor of 192 Ir source,to measure air kenna of 192Ir source with and without lead shield using thimble ionization chamber.Simulation measurement conditions were used to calculate scatter correction factor of 192Ir source and comparison was made between experimental results and literature records.At the same time,the different ionization chamber models were simulated at different room sizes to obtain scattering correction factor of 192 Ir source.ResultsComparison was made between the simulation scatter correction factors of 192Ir source and experiment by the shadow shield,and the relative deviation was 0.8%.The deviation of the 192 Ir activity calculated according to the simulated scatter correction factor and measured by well type ionization chamber was 2.4%.By comparison between the calculated results by using two kinds of spherical ionization chamber and those ones deduced by IAEA 1079 Report,the relative deviations ranged within 0.3%-0.4%.Five different types of thimble ionization chamber and different room sizes were simulated and calculated by MC simulation,with the relative deviation within 3%.Conclusions Monte Carlo simulation method for calculating afterloading 192 Ir source's scatter correction factor is feasible,and this method is convenient for use in the thimble chamber for brachytherapy QA work in the hospital.
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Most brachytherapy treatment planning systems employ a dosimetry formalism based on the AAPM TG-43 report which does not appropriately consider tissue heterogeneity. In this study we aimed to set up a simple Monte Carlo-based intracavitary high-dose-rate brachytherapy (IC-HDRB) plan verification platform, focusing particularly on the robustness of the direct Monte Carlo dose calculation using material and density information derived from CT images. CT images of slab phantoms and a uterine cervical cancer patient were used for brachytherapy plans based on the Plato (Nucletron, Netherlands) brachytherapy planning system. Monte Carlo simulations were implemented using the parameters from the Plato system and compared with the EBT film dosimetry and conventional dose computations. EGSnrc based DOSXYZnrc code was used for Monte Carlo simulations. Each (192)Ir source of the afterloader was approximately modeled as a parallel-piped shape inside the converted CT data set whose voxel size was 2x2x2 mm3. Bracytherapy dose calculations based on the TG-43 showed good agreement with the Monte Carlo results in a homogeneous media whose density was close to water, but there were significant errors in high-density materials. For a patient case, A and B point dose differences were less than 3%, while the mean dose discrepancy was as much as 5%. Conventional dose computation methods might underdose the targets by not accounting for the effects of high-density materials. The proposed platform was shown to be feasible and to have good dose calculation accuracy. One should be careful when confirming the plan using a conventional brachytherapy dose computation method, and moreover, an independent dose verification system as developed in this study might be helpful.
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Humans , Accounting , Brachytherapy , Film Dosimetry , Monte Carlo Method , Organoplatinum Compounds , Population Characteristics , Uterine Cervical Neoplasms , WaterABSTRACT
For HDR intracavitary brachytherapy with ovoids and a tandem, we compared the dose discrepancy of treatment plans using two different Ir-192 sources (microSelectron, Varian) and generated on two different treatment planning systems (PLATO, BrachyVision). The treatment plans of ten patient treated from Oct. 2007 to Jan. 2008 were selected for these comparisons. For the comparison of dose calculation using different sources, the average discrepancies were -0.91+/-0.09%, 0.27+/-0.07%, 0.22+/-0.39%, and 0.88+/-0.37% in total treatment time and at B-point and ICRU bladder and rectum reference point, respectively. Comparing the two systems, the average dose discrepancies between treatment planning programs were -0.22+/-0.42%, -0.25+/-0.29%, -0.23+/-0.63%, and -0.17+/-0.76%, and the average dose discrepancies between positioning methods (PLATO with film and BrachyVision with digitial image) were -0.61+/-0.59%, -0.77+/-0.45%, -0.72+/-1.70%, and 0.35+/-2.82% at A-point, B-point, and ICRU bladder and rectum reference points, respectively. The rectal dose discrepancies between two systems were reached 5.87%. The difference in the dwell position expected by each TPS are mainly affected by the differences in the positioning method in TPSs and have an effect on dose calculations of rectal and bladder located in AP direction.
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Humans , Brachytherapy , Rectum , Urinary BladderABSTRACT
Objective To develop measurement of reference air kerma for192Ir sources with NE 2570 electrometer,2571 ion-chamber and machining measured holder.Methods The measuring holder was placed at the distance of 1 m from the walls,the floor and ceiling,the ion-chambet was insert into the oolymethyl methacrylate(PMMA)jig of the measuring holder,lhe optimum distance is 16 cm from the source centre to ionchamber centre.The source was transmitted by the afterloding system to the plastic pipe to measure reference air kerma of the source.According to calibration factors from60Coγrays and 250 kV X rays with air exposure to calculated the air kerma calibration factor,the air kerma calibration factor of 192Ir soHree was calculated bv60Co γ rays and the effective energy of the 250 kV X ray beam.The scatter correction factor was giverl by the shadow shield experiment for the wails,the floor,the air and the measuring holder,the correction factors were given for the attenuation of primary photons in air and the electrons entering the air cavity are mainly generated in the innerwall of the chamber by 1079 report in IAEA.Results Two measuring methods were used for192Ir source undersame environment condition,the ion-chatuber and well-type chamber values are 1.584×1011Bq and 1.561×1011Bq respectively,and the relative deviation from them is within 1.4%,Conclusions The air kerma measurement of 192Ir source the ion-chamber with is not depended on the source geometry(point seurce,line source etc),the size.and the material of shell,the shape,the quality of materials and the size of the chamber.The uncertainty error of the air kerma is lessin comparison to the air exposure.
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Objective To evaluate the safety and efficacy of 192Ir intraluminal brachytherapy for the prevention of urethral re-stricture after transurethral incision or transurethral resection of scar. Methods From Mar. 2004 to Jun. 2006,48 patients aging 18-81 years were treated by 192Ir intraluminal brachytherapy. The length of stricture(0.5-5.5 era) was≤3.0 cm in 90% of the patients. The stricture was caused by trauma in 23 patients and prostate hyperplasia operation in 19 patients. The cause of remaining 6 patients was unclear. All patients were diagnosed by urethra photograph or endoscopy. Radiotherapy was the initial treatment in 26 patients and the second time treatment in 22. The irradiation dose was from 14 Gy to 18 Gy.Results The median follow up was 10 months,and the total response rate was 98%. Only one patient recurred and received transurethral incision again. The uresis was fluency in 47 patients and the maximum flow rate was 13.9-36.4(19.2±10.3) ml/s. No secondary urethral bleeding or urethral cancer was observed.Conclusions Being a safe and feasible treatment, ,192Ir intraluminal brachytherapy following transurethral incision or transurethral resection of scar can effectively prevent urethral re-stricture.