ABSTRACT
Currently, the dose distribution calculation used by commercial treatment planning systems (TPSs) for high-dose rate (HDR) brachytherapy is derived from point and line source approximation method recommended by AAPM Task Group 43 (TG-43). However, the study of Monte Carlo (MC) simulation is required in order to assess the accuracy of dose calculation around three-dimensional Ir-192 source. In this study, geometry factor was calculated using segmented sources integration method by dividing microSelectron HDR Ir-192 source into smaller parts. The Monte Carlo code (MCNPX 2.5.0) was used to calculate the dose rate D(r,theta) at a point (r,theta) away from a HDR Ir-192 source in spherical water phantom with 30 cm diameter. Finally, anisotropy function and radial dose function were calculated from obtained results. The obtained geometry factor was compared with that calculated from line source approximation. Similarly, obtained anisotropy function and radial dose function were compared with those derived from MCPT results by Williamson. The geometry factor calculated from segmented sources integration method and line source approximation was within 0.2% for r> or =0.5 cm and 1.33% for r=0.1 cm, respectively. The relative-root mean square error (R-RMSE) of anisotropy function obtained by this study and Williamson was 2.33% for r=0.25 cm and within 1% for r>0.5 cm, respectively. The R-RMSE of radial dose function was 0.46% at radial distance from 0.1 to 14.0 cm. The geometry factor acquired from segmented sources integration method and line source approximation was in good agreement for r> or =0.1 cm. However, application of segmented sources integration method seems to be valid, since this method using three-dimensional Ir-192 source provides more realistic geometry factor. The anisotropy function and radial dose function estimated from MCNPX in this study and MCPT by Williamson are in good agreement within uncertainty of Monte Carlo codes except at radial distance of r=0.25 cm. It is expected that Monte Carlo code used in this study could be applied to other sources utilized for brachytherapy.
Subject(s)
Anisotropy , Brachytherapy , Organothiophosphorus Compounds , Uncertainty , WaterABSTRACT
Os sintomas resultantes das lesões endobrônquicas são comuns nos pacientes portadores de câncer do pulmão e tem um impacto negativo significativo na qualidade de vida. Inúmeras opções terapêuticas estão disponíveis para o tratamento paliativo destes pacientes: braquiterapia endobrônquica, colocação de próteses endobrônquicas, ressecção com laser ou eletrocautério ou a radioterapia convencional. Esta revisão tem como objetivos descrever o método e o papel da braquiterapia endobrônquica em pacientes portadores de neoplasia pulmonar e mostrar nossa experiência com o método em nossa instituição.
Symptoms resulting from tumors extending to the endobronchial wall are common in patients with lung cnacer and significantly impacts quality of life. A number of treatment options are available for palliation, including endobronchial brachytherapy, stent placement, laser photoresection, eletrocautery resection and external-beam radiation therapy. This reviewwill focus on the methodology and role of endobronchial brachytherapy in patients with lung cancer and will review ourexperience with this procedure.
Subject(s)
Humans , Male , Female , Palliative Care , Brachytherapy , Lung Neoplasms , Brachytherapy , Brachytherapy/history , Brachytherapy/methods , Quality of LifeABSTRACT
The compatibility with GammaMed-12i brachytherapy machine for an Ir-192 encapsulated source (IRRS20, KAERI, Korea) manufactured by Korea atomic energy research institute (KAERI) has been investigated. As a mechanical testing of compatibility, precise measurement of step movement with channels, measurement of curvature of radius for wire, and emergency return testing were performed. Periodic measurements of air kerma strength for 45 days were carried out to evaluate decay characteristics of Ir-192 radioisotope and comparison of dose distributions in phantom between KAERI and old sources previously used were performed by film dosimetry. KAERI source has a good compatibility with GammaMed12i machine as a result of mechanical testing. There are in good agreement with calculated values in activity characteristics and there were small differences in dose distributions around the source in comparison between KAERI and old source.
Subject(s)
Academies and Institutes , Brachytherapy , Emergencies , Film Dosimetry , Korea , Nuclear Energy , RadiusABSTRACT
Objective To perform thermoluminescent measurements of radial dose function and anisotropy function of a newly designed 192Ir microSelectron-HDR source, and establish evaluation methods for HDR dosimetry.Methods A polystyrene phantom with sylindrical holes in different measure positions was designed to accommodate thermo luminescent dosimeter (TLD) rods and radiation source.TLD rods with similar sensitivity were placed on a semicircle around the source center which had been precisely localized by either radiographic means or dose measurement.Dose-rates were measured at θ = 90° and r = 1-14 cm to calculate radial dose function (gL (r)), while measured along polar angles θ = 0° -165°(interval 15°) at radial distances r = 1 cm, 3 cm and 5 cm to calculate anisotropy function (F(r,θ)).All data were compared with those calculated by Monte Carlo (MC) method.The t-test was used for the statistics.Results The values of gL (r) were 1.007 -0.681 by calculation and 1.007 -0.598 by measurement with r = 1 - 14 cm(t = 0.00 - 2.89, all P > 0.05).The values of F (r,θ) were 0.631 - 1,0.660 - 1 and 0.696 - 1 by calculation, while 0.701 - 1, 0.668 - 1 and 0.629 - 1 by measurement at 1 cm, 3 cm and 5 cm with θ=0° -165°(t=0.40 -1.63, 0.02 -2.10, 0.08 -2.03, all P>0.05).Conclusions The results of radial dose function and anisotropy function measured by TLD measurement are in consistent with those calculated by MC calculations, which can be applied in treatment planning system as original input.
ABSTRACT
El cáncer representa un problema de salud pública. El cáncer de mama, es una entidad que aumenta su incidencia en el mundo. Esto ha llevado a nuevos enfoques terapéuticos quirúrgicos, químicos y radiantes. En el siguiente trabajo se hace mención del tratamiento con braquiterapia de alta tasa de dosis realizado en el Hospital Universitario de Mérida, en el servicio integral de oncología. Se evaluaron 148 pacientes con cáncer de mama en todos los estadios desde febrero 2007 hasta 30 mayo 2008. Se seleccionaron pacientes estadio I-IIANO MO, se analizaron las pacientes que reunieron los criterios de inclusión. En 19 pacientes (12,8 %) se cumplió braquiterapia intersticial hiperfraccionada con intervalo de 6 horas (800 cGy/día) 4 sesiones (400 cGy por fracción). Dosis total 3200 cGy. Con rango de seguimiento entre 18 meses y 2 meses y un promedio de 10 meses sin evidencia de recaída locorregional.
The breast cancer represents a public health problem. The breast cancer is entities which increase his incidence in the world. These problem do to a creation of new surgery, chemical and radiant therapeutically modes. In these work we mention the high dose brachytherapy tease doses realized in the University Merida Hospital in the integral service of oncology. We evaluated 148 patients with breast cancer disease in all the stage since February 2007 to May30 of 2008. We selected a 148 patients classified stage I-IIANO MO, and analyzed the patients with have inclusion therapeutically criterions. In 19 (12.8 %) patients were underwent to interstitial brachytherapy hyperfraccion with and interval to 6 hours (800 cGy/day) in 4 sessions (400 cGyfor fraction). Total doses applied was 3200 cGy. With a control range between 18 month and 2 month, and average of 10 month without any evidence of loco regional distress.
Subject(s)
Humans , Female , Brachytherapy/methods , Doppler Effect , Breast Neoplasms/surgery , Breast Neoplasms/pathology , Breast Neoplasms/radiotherapy , Iridium Radioisotopes/administration & dosage , Carcinoma/pathology , Carcinoma/therapy , Early Diagnosis , Mastectomy, Radical/methodsABSTRACT
The quality correction in the air kerma dosimetry for Ir-192 using farmer type ionization chambers calibrated by Co-60 quality is required. In this study we determined quality factor (kappa u) of two ionization chambers of PTW-N30001 and N23333 for Ir-192 source using dosimetric method. The quality factors for energy spectrum of microSelectron were determined as kappa u=1.016 and 1.017 for PTW-N30001 and N23333 ionization chambers respectively. We applied quality factors in air kerma dosimetry for microSelectron source and compared with reference values. As a results we found that the differences between reference air kerma rate and measured it with and without quality correction were about -0.5% and -2.0% respectively.
Subject(s)
Gamma Rays , Reference ValuesABSTRACT
PURPOSE: A PC based brachytherapy planning system was developed to display dose distributions on simulation images by 2D isodose curve including the dose profiles, dose-volume histogram and 3D dose distributions. MATERIALS AND METHODS: Brachytherapy dose planning software was developed especially for the Ir-192 source, which had been developed by KAERI as a substitute for the Co-60 source. The dose computation was achieved by searching for a pre-computed dose matrix which was tabulated as a function of radial and axial distance from a source. In the computation process, the effects of the tissue scattering correction factor and anisotropic dose distributions were included. The computed dose distributions were displayed in 2D film image including the profile dose, 3D isodose curves with wire frame forms and dose- volume histogram. RESULTS: The brachytherapy dose plan was initiated by obtaining source positions on the principal plane of the source axis. The dose distributions in tissue were computed on a 200x200 (mm2) plane on which the source axis was located at the center of the plane. The point doses along the longitudinal axis of the source were 4.5~9.0% smaller than those on the radial axis of the plane, due to the anisotropy created by the cylindrical shape of the source. When compared to manual calculation, the point doses showed 1~5% discrepancies from the benchmarking plan. The 2D dose distributions of different planes were matched to the same administered isodose level in order to analyze the shape of the optimized dose level. The accumulated dose-volume histogram, displayed as a function of the percentage volume of administered minimum dose level, was used to guide the volume analysis. CONCLUSION: This study evaluated the developed computerized dose planning system of brachytherapy. The dose distribution was displayed on the coronal, sagittal and axial planes with the dose histogram. The accumulated DVH and 3D dose distributions provided by the developed system may be useful tools for dose analysis in comparison with orthogonal dose planning.
Subject(s)
Anisotropy , Axis, Cervical Vertebra , Benchmarking , BrachytherapyABSTRACT
Authors have developed highly reproducible calibration method for the Micro-Selection HDR Ir-192 system(Nucletron, Netherland). The new jig has a 10cm radius circular hole in the 30cm x 30cm x 0.2cm acrylic plate, and 5F flexible bronchial tubes are attached around the hole. The source moves along the circle in the tubes an? the ionization chamber is placed vertically at the center of the circular hole(center of the jig). Dose distribution near the center was derived theoretically, and measured with the film dosimetry system. Theoretical calculation and measurement show the error margin below 0.1% for 1mm or 2mm position deviation. We have measured at 12 and 24 points of circle with 1, 6, 11 and 21 second dwell time of source in order to calculate the activity of the source. Measurements have been repeated daily for 50 days. The accuracy and the reproducibility are below 1% error margin. The half life of the source from our measurement is estimated 73.4+/-0.4 days.
Subject(s)
Calibration , Film Dosimetry , Half-Life , RadiusABSTRACT
Recently radiation and radioisotope are being used widely in many fields such as medicine and industry. But only a few papers were reported about the radio dermatitis due to industrial use of radiation. Authors experienced 4 cases of occupational radiodermatitis due to Ir-192 occur red during the radioisotope traspierce test. All 4 patients noticed painful swelling, erythema, and bullae on their fingers or palms 1-2 weeks after exposure. All laboratory tests to detect ystemic effects of radiation were normal. Three patients recovered after treatment with systemic and topical corticosteroid and emollient cream for 2-4 weeks. But one patient suffered from complication of fibrosis and recurrent cellulitis on his fingers. We discussed about the working situation of our patients and reviewed the literatures about the radiodermatitis.