Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-06-09T18:38:57Z No. of bitstreams: 0 / Made available in DSpace on 2015-06-09T18:38:57Z (GMT). No. of bitstreams: 0 / As últimas estimativas da Organização Mundial da Saúde mostram a ocorrência de 14,1 milhões de novos casos de câncer em 2012. Sendo que desses casos, 8,2 milhões virão a óbito. Os tumores paravertebrais e intracraniais, também chamados de cânceres do Sistema Nervoso Central, tem origem no cérebro, nervos cranianos e meninges. Uma nova modalidade de braquiterapia começou a ser usada nesta última década. Neste procedimento, placas poliméricas flexíveis, carregando fósforo-32, são colocadas próximas ou em contato ao tumor para o tratamento. Este tratamento apresenta vantagens em relação aos demais porque aplica uma alta taxa de dose no tumor poupando tecidos sadios. A produção destas placas ainda é pouco estudada, embora já existam resultados satisfatórios no seu uso para o tratamento dos cânceres do sistema nervoso central. Neste trabalho foram realizados estudos iniciais para a produção deste tipo de placas poliméricas para braquiterapia. Foram avaliadas as propriedades mecânicas e a capacidade de imobilização de material radioativo de duas resinas comercias, uma poliuretânica e outra epoxídica, com e sem presença de substrato de policarbonato. Os testes iniciais apontaram o uso da resina epoxídica como melhor alternativa e com o uso dela foram feitos os primeiros protótipos e testes. O uso do policarbonato como substrato não foi necessário em uma das metodologias, facilitando o procedimento, mas oferecendo uma barreira menor de segurança. Os ensaios de tração mostraram que a adição de solução ácida à resina epóxi alterou suas características mecânicas, mas houve uma pequena melhora em sua flexibilidade. Os testes de adesão evidenciaram uma melhor adesão da resina à face texturizada do policarbonato. A termogravimetria mostrou que a solução ácida adicionada a resina fica presa à estrutura mesmo com elevações de temperatura acima de 100°C. A resina epoxídica utilizada teve a capacidade de incorporar o material radioativo em forma de solução ácida e manter-se estanque após testes de esfregaço e imersão em líquido quente. De acordo com os resultados obtidos, a produção destas placas com resina epoxídica é possível e atende às normas internacionais de segurança contra vazamento de material radioativo para fontes utilizadas em braquiterapia. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-07-29T15:29:14Z (GMT). No. of bitstreams: 1 Dissertacao Livia C de S N Bianchi - Oftalmologia.pdf: 3291987 bytes, checksum: bf690044678ae1c1ecf40768b3ef062a (MD5) Previous issue date: 2012-03-27 / Purpose: To evaluate the efficacy and safety of strontium-90 epimacular brachytherapy combined with intravitreal bevacizumab for treating subfoveal choroidal neovascularization secondary to exudative age-related macular degeneration. Its effects on visual acuity and macular thickness at 36 months of follow up were also studied. Methods: Sixteen patients with predominantly classic, minimally classic and occult choroidal neovascularization were treated with a single 24 Gy dose of radiation during pars plana vitrectomy, associated to two injections of bevacizumab at baseline and one injection at the one-month visit. The patients underwent a complete ophthalmologic examination, which included fluorescein angiography and optical coherence tomography, at the initial visit, every three months during the first year, and every six months during the second and third years of follow up. Results: Of the 16 cases, 2 patients (12.5%) lost more than 15 letters at the end of 36 months, and 3 (18.75%) lost fewer than 15 letters. Among the patients with improved visual acuity, 3 (18.75%) gained less than 15 letters and 8 (50%) gained more than 15 letters at the end of treatment. The mean best corrected visual acuity showed a gain of 16.0 letters at 12 months. After 36 months (n = 16), the mean best corrected visual acuity showed a gain of 10.4 letters. Of the 16 eyes included in the study, six required further therapy. The evaluation of macular thickness showed decreased thickness in 10, among the 16 patients (62.5%). Three eyes (18.75%) had similar values at the beginning and the end of 36 months, and 3 eyes (18.75%) showed increased macular thickness. Conclusion: Epimacular brachytherapy combined with bevacizumab may be considered a possible therapeutic option for choroidal neovascularization in age-related macular degeneration. The procedure was thought to be safe and was well tolerated by the patients. The treatment resulted in anatomical and functional improvements, compatible with currently available therapies. / Objetivo: Avaliar a eficácia e segurança da braquiterapia epimacular com estrôncio 90 e bevacizumabe intravítreo para tratamento da neovascularização coróidea subfoveal secundária à degeneração macular relacionada à idade exsudativa, e observar seus efeitos na acuidade visual e espessura macular, em 36 meses de seguimento. Metodologia: Foram estudados 16 pacientes portadores de neovascularização coróidea, (predominantemente clássicas, minimamente clássicas e ocultas) tratados com dose única de radiação de 24Gray, durante vitrectomia via pars plana, associada a duas injeções de bevacizumabe uma no início do tratamento e a outra um mês após. Foram realizados exame oftalmológico completo, angiofluoresceinografia e tomografia de coerência óptica na visita inicial, a cada três meses durante o primeiro ano e a cada seis meses durante o segundo e o terceiro anos de seguimento. Resultados: Dos 16 casos, 2 (12,5%) perderam mais de 15 letras ao final de 36 meses, e 3 pacientes (18,75%) perderam menos de 15 letras. Dentre os pacientes que melhoraram a acuidade visual, 3 (18,75%) ganharam menos de 15 letras e 8 (50%) ganharam mais de 15 letras ao final do tratamento. A média da melhor acuidade visual corrigida demonstrou ganho de 16,0 letras ao final de 12 meses. Após 36 meses (n = 16), a média da melhor acuidade visual corrigida apresentou um ganho de 10,4 letras pela tabela ETDRS. Dos 16 olhos observados, 6 necessitaram de tratamento adicional. Na avaliação da espessura macular, 10 (62,5%) dos 16 pacientes apresentaram diminuição da espessura, 3 olhos (18,75%) mantiveram valores semelhantes no início e ao final de 36 meses, e 3 olhos (18,75%) apresentaram aumento da espessura macular. Conclusão: A braquiterapia epimacular combinada ao uso de bevacizumabe se mostra como uma possível opção terapêutica para a neovascularização de coróide na degeneração macular relacionada à idade. O procedimento foi considerado seguro e bem tolerado, com melhora antômica-funcional compatível aos tratamentos atualmente disponíveis.

Brachytherapy (BT) with continuous low dose rate (LDR) has been used for 100 years and is considered as the radiotherapy method able to deliver a dose in the shortest time with high efficacy and low risk of side effects. The drawbacks are need for patient isolation and radiation exposure of the staff during the treatment. Brenner and Hall published the radiobiology concept for pulsed dose rate (PDR) in 1991.  Short (10-20 minutes), hourly pulses of high dose rate (HDR) given to the same dose, with same overall treatment time will virtually simulate continuous LDR. At the same time new afterloading machine technology became available, where a single millimetre sized radiation 192Iridium source sequentially moves through the applicator in small individually timed steps. The advantages are that the radiation dose can be optimized along the applicator and with no radiation exposure of the staff and no need for patient isolation more than during the pulse. This work deals with four different aspects of PDR BT An experimental comparison of measured absorbed doses outside a left sided breast target on a body equivalent Alderson phantom was made.  Five external beam radiotherapy (EBRT) whole breast treatments to 50 Gy versus five accelerated partial breast irradiations (APBI) by PDR BT to 50 Gy were studied. The absorbed doses were measured in 67 different positions inside the body phantom by thermoluminescence dosimeters. The result shows that dose points distant to the left breast will have 1-1.4 % of the prescribed dose with no difference between EBRT and PDR BT. Organs at risk in short distance (<5 cm) to the target (such as parts of the left lung, heart muscle and the right breast) will have significantly less dose by PDR BT. In conclusion PDR BT has dosimetric advantages close to the target compared to EBRT and cannot do more damage to remote organs. PDR APBI as the adjuvant RT treatment to breast conserving surgery after early breast cancer was studied. Between 1994-2004 we treated 50 women and 51 breasts. The median age of the population was 53 (40-72) years. The cases were radically resected, unifocal T1-2N0-1M0 tumours. PDR BT was given to a dose of 50 Gy for 5 days directed to the operated sector of the breast. The median treated volume was 160 cm3, constituting in median 31 % of the breast volume. The treatment is called accelerated because total treatment time is 5 days compared to 5 weeks for EBRT. After a median follow-up of 130 months (>10 years) we noted 5 (10 %) local recurrences in the treated breast. Four of these recurrences were outside the treated volume. Three women (6 %) developed cancers in the other breast. Early side effects were mild and less than with EBRT. As late side effects we found mild to moderate local fibroses in the treated volume. A cosmetic evaluation was done by both the patient and a nurse and was found to be lower than in other published data (56 % = good to excellent). The 10 years local failure rate is similar to the result from a large Swedish randomized study on whole breast radiotherapy to 50 Gy. The study indicates that PDR BT is highly effective. A combination of EBRT (40.8 Gy) and PDR boost (35 Gy) to T1-4N0-3M0, base of tongue (BOT) cancer, treated during 1994-2007 was analyzed. The study is the first with PDR and second largest with BT worldwide. A number of 83 patients with a median age of 60 (38-82) years were included. BT was given to a mean volume of 58 ccm 2 days after the neck dissection. Median follow-up was 54 months. At 5 years we found 89 % local tumour control, 95 % neck control, 80 % disease free survival and an overall survival of 65 %. Late side effects were 13 % minor transient soft tissue necrosis and 12 % long lasting or permanent soft tissue- or osteoradio-necrosis. The results are among the best published worldwide. An extensive quality of life analysis was done on 45 patients at last follow-up and showed limited, persistent xerostomia and dysphagia. The global quality of life was rated good in 75 % of the patients. The last study presented was PDR mono-brachytherapy (55-60 Gy) to cancer of the lip (T1-3N0M0). The study included 43 patients with a median age of 74 (37-92) years. The treatment time was 5.5-6 days and the mean treated volume was 15 ccm. The median follow-up time was 54 (1-158) months. Five year Kaplan-Meier data showed, local control 94 %, disease free survival 86 % and overall survival 59 %. An early side effect was a strong radiation mucositis and dermatitis, which healed in 1 month. Late side effects were uncommon and the cosmetic appearance and the lip function were found to be normal. Our data in total and per T-stage was compared to a European survey from 1993 on 2794 patients treated by LDR BT. The results are similar and are a strong indication of equal efficacy between PDR and LDR.

In the past twenty years, the combination of the advances in medical imaging technologies and therapeutic methods had a great impact in developing minimally invasive interventional procedures. Although the use of medical imaging for the surgery and therapy guidance dates back to the early days of x-ray discovery, there is an increasing evidence in using the new imaging modalities such as computed tomography (CT), magnetic reso- nance imaging (MRI) and ultrasound in the operating rooms. The focus of this thesis is on developing image-guided interventional methods and techniques to support the radiation therapy treatment of gynecologic cancers. Gynecologic cancers which involves malignan- cies of the uterus, cervix, vagina and the ovaries are one of the top causes of mortality and morbidity among the women in U.S. and worldwide. The common treatment plan for radiation therapy of gynecologic cancers is chemotherapy and external beam radiation therapy followed by brachytherapy. Gynecological brachytherapy involves placement of interstitial catheters in and around the tumor area, often with the aid of an applicator. The goal is to create an optimal brachytherapy treatment plan that leads to maximal radiation dose to the cancerous tissue and minimal destructive radiation to the organs at risk. The accuracy of the catheter placement has a leading effect in the success of the treatment. However there are several techniques are developed for navigation of catheters and needles for procedures such as prostate biopsy, brain biopsy, and cardiac ablation, it is obviously lacking for gynecologic brachytherapy procedures. This thesis proposes a technique which aims to increase the accuracy and efficiency of catheter placements in gynecologic brachytherapy by guiding the catheters with an electromagnetic tracking system. To increase the accuracy of needle placement a navigation system has been set up and the appropriate software tools were developed and released for the public use as a module in the open-source 3D Slicer software. The developed technology can be translated from benchmark to the bedside to offer the potential benefit of maximizing tumor coverage during catheter placement while avoiding damage to the adjacent organs including bladder, rectum and bowel. To test the designed system two independent experiments were designed and performed on a phantom model in order to evaluate the targeting accuracy of the tracking system and the mean targeting error over all experiments was less than 2.9 mm, which can be compared to the targeting errors in the available commercial clinical navigation systems.

La curiethérapie est une méthode pour traiter les tumeurs cancéreuses qui consiste à placer à leur proximité des sources radioactives dont les rayonnements endommagent les cellules et mènent éventuellement à leur destruction. En curiethérapie conventionnelle, les sources utilisées sont scellées et seuls des rayonnements bêta et gamma s’en échappent. Dans une méthode de curiethérapie récemment commercialisée, la source n’est pas scellée et permet à des radionucléides, situés à quelques nanomètres sous sa surface, de s’échapper par mouvement de recul lors de leur désintégration. Ces radionucléides se diffusent par la suite dans la tumeur tout en poursuivant une chaîne de désintégration au cours de laquelle ils émettent principalement des particules alpha. L’énergie déposée par les particules alpha par unité de masse de tissu tumoral constitue la dose alpha. Les outils numériques de la curiethérapie conventionnelle ne tiennent pas compte de la diffusion des émetteurs et sont de ce fait inaptes à calculer correctement la distribution spatiale de la dose alpha. Le travail présenté ici avait pour but de développer des outils numériques incluant la modélisation de la diffusion, permettant ainsi un calcul adéquat de la distribution de dose. La méthode des volumes fnis a été utilisée pour développer des modèles en une, deux et trois dimensions, en coordonnées cylindriques et cartésiennes. Ces modèles déterminent où et quand se produisent les désintégrations, une information clé dans ce travail qui pourra aussi être utilisée dans des travaux futurs comme donnée d’entrée des outils numériques de la curiethérapie conventionnelle pour calculer les doses bêta et gamma. / Brachytherapy is a method for treating cancerous tumors which consists of placing near them radioactive sources whose radiation damages cells which eventually leads to their destruction. In conventional brachytherapy, the sources are sealed and only beta and gamma radiations escape. In a recently commercialized method of brachytherapy, the source is not sealed and allows radionuclides, located a few nanometers below its surface, to be released by recoil during their decay. These radionuclides then diffuse into the tumor while continuing to follow a decay chain during which they mainly emit alpha particles. The energy deposited by alpha particles per unit mass of tumor tissue constitutes the alpha dose. The numerical tools of conventional brachytherapy do not take into account the diffusion of emitters and are therefore unable to correctly calculate the spatial distribution of the alpha dose. The work presented here aimed at developing numerical tools including diffusion modeling, thus allowing an adequate calculation of the dose distribution. The finite volume method was used to develop models in one, two and three dimensions, in cylindrical and Cartesian coordinates. These models determine where and when radioactive decays occur, a key information in this work having also the potential of being used in future work as an input data for conventional brachytherapy numerical tools to calculate beta and gamma doses.

Le cancer du col de l’utérus, le quatrième cancer le plus répandu chez la femme, affecte principalement les régions à faible et moyen revenu. Alors que les taux d’incidence et de mortalité sont les plus élevés dans les pays en développement, l’accessibilité aux systèmes de dépistage et traitement y est limitée. La curiethérapie (BT) à haut débit de dose (HDR) fait partie du traitement standard recommandé pour les cancers du col de l’utérus en stade localement avancé IIIB-IVA. Les applicateurs commerciaux pour les traitements de BT combinés intracavitaire et interstitiel (IC/IS) sont très chers et n’offrent que des positions et orientations fixes pour les aiguilles IS. L’applicateur à demi anneaux Montréal (MSR) propose la modification d’un applicateur IC commercial par l’ajout de capuchons Adaptiiv, imprimés 3D à faible coût avec la technologie de photopolymérisation (SLA) en résine stérilisable et biocompatible, permettant l’intégration et l’optimisation d’un maximum de 10 trajectoires IS. Dans cette étude, une nouvelle génération de capuchons réduit le diamètre de l’applicateur MSR d’au plus 8.4 mm et introduit quatre positions d’aiguilles IS additionnelles à l’intérieur du demi anneau (SR), deux positions par SR. Ces capuchons sont imprimés avec la résine BioMed Clear sur l’imprimante SLA Form3B (Formlabs Inc., Massachusetts, États-Unis) et accommodent des angles d’aiguilles IS allant jusqu’à 45°. Les erreurs sur les trajectoires des aiguilles IS de l’applicateur MSR avec les nouveaux capuchons sont évaluées dans un fantôme gynécologique (GYN), développé dans le cadre de ce projet, et comparées dans une analyse statistique aux performances de l’applicateur Venezia (Elekta, Stockholm, Suède). Le fantôme GYN développé comprend une masse implantable en silicone, dont la texture est optimisée avec l’expérience clinique de deux radio-oncologistes spécialisées en BT GYN pour simuler l’insertion d’implants cliniques, pouvant supporter un grand nombre d’aiguilles IS. L’étude sur ce fantôme a démontré que la performance de l’un des capuchons de la nouvelle génération ne présente pas de différence statistiquement et cliniquement significative avec l’applicateur Venezia. Les performances de ce capuchon sont reproductibles dans les différents milieux en silicone et en utilisant différents types d’aiguilles IS. / Cervical cancer, the fourth most common cancer in women, mainly affects low- and middleincome regions. While incidence and mortality rates are highest in developing countries, the accessibility to screening and treatments is limited in those regions. High dose rate (HDR) brachytherapy (BT) is part of the standard of care recommended for locally advanced cervical cancer. Commercial applicators for combined intracavitary-interstitial (IC/IS) BT treatments are very expensive and only offer fixed IS needle positions and orientations. The Montreal split ring (MSR) applicator modifies the CT/MR split-ring IC applicator by the addition of Adaptiiv caps, 3D printed at low cost with stereolithography apparatus (SLA) technology in biocompatible and sterilizable resin in order to allow integration and optimization of up to 10 IS trajectories. In this study, a new generation of caps reduces the diameter of the MSR applicator by at most 8.4 mm and introduces four additional IS needle positions inside the split ring (SR), two positions per SR. These caps are 3D printed using BioMed Clear resin on the Form3B (Formlabs Inc., Massachusetts, USA) SLA printer and accommodate up to 45° IS needle angles. The errors on the IS needle trajectories of the MSR applicator with the new caps are evaluated in a gynecological (GYN) phantom, developed within the framework of this project, and compared in a statistical analysis to the performance of the Venezia applicator (Elekta, Stockholm, Sweden). The developed GYN phantom includes an implantable silicone structure, optimized according to the feedback of two radiation oncologists specialized in GYN BT to simulate clinical implants insertion, which can support a large number of IS needles. The study on this phantom showed that the performance of one of the caps from the new generation does not present a statistically and clinically significant difference with the Venezia applicator. The performance of this cap is reproducible in different silicone media and using different IS needle types.

No description available.

<p>Developing radiation delivery systems for optimisation of absorbed dose to the target without normal tissue toxicity requires advanced calculations for transport of radiation. In this thesis absorbed dose and fluence in different radiotherapy applications were calculated by using Monte Carlo (MC) simulations.</p><p>In paper I-III external neutron activation of gadolinium (Gd) for intravascular brachytherapy (GdNCB) and tumour therapy (GdNCT) was investigated. MC codes MCNP and GEANT4 were compared. MCNP was chosen for neutron capture reaction calculations. Gd neutron capture reaction includes both very short range (Auger electrons) and long range (IC electrons and gamma) products. In GdNCB the high-energetic gamma gives an almost flat absorbed dose delivery pattern, up to 4 mm around the stent. Dose distribution at the edges and inside the stent may prevent stent edge and in-stent restenosis. For GdNCT the absorbed dose from prompt gamma will dominate over the dose from IC and Auger electrons in an in vivo situation. The absorbed dose from IC electrons will enhance the total absorbed dose in the tumours and contribute to the cell killing.</p><p>In paper IV a model for calculation of inter-cluster cross-fire radiation dose from β-emitting radionuclides in a breast cancer model was developed. GEANT4 was used for obtaining absorbed dose. The dose internally in cells binding the isotope (self-dose) increased with decreasing β-energy except for the radionuclides with substantial amounts of conversion electrons and Auger electrons. An effective therapy approach may be a combination of radionuclides where the high self-dose from nuclides with low β-energy should be combined with the inter-cell cluster cross-fire dose from high energy β-particles.</p><p>In paper V MC simulations using correlated sampling together with importance sampling were used to calculate spectra perturbations in detector volumes caused by the detector silicon chip and its encapsulation. Penelope and EGSnrc were used and yielded similar results. The low energy part of the electron spectrum increased but to a less extent if the silicon detector was encapsulated in low z-materials.</p>

O câncer de próstata é um problema de saúde pública no Brasil, sendo a segunda causa de óbitos por câncer em homens, superado apenas pelo câncer de pulmão. Entre os possíveis tratamentos disponíveis para o câncer de próstata encontra-se a braquiterapia, onde, pequenas sementes contendo o radioisótopo 125I são implantadas na próstata. A semente consiste de uma cápsula de titânio selada de 0,8 mm de diâmetro externo e 4,5 mm de comprimento, contendo um fio de prata com 125I adsorvido. A soldagem por arco plasma é uma das técnicas viáveis para selagem, o equipamento tem um custo menor que o de outros processos. Constituem os objetivos deste trabalho o desenvolvimento e a validação do procedimento de selagem utilizando processo de soldagem plasma e a elaboração de rotinas para selagem segundo as Boas Práticas de Fabricação. O desenvolvimento do trabalho apresentou as seguintes fases: corte e limpeza do material, determinação dos parâmetros de soldagem, desenvolvimento de dispositivos para fixação do tubo de titânio durante o processo de soldagem, ensaios de validação de fontes seladas conforme norma ISO 2919 Sealed Radioactive Sources General Requirements and Classification, ensaios de estanqueidade conforme norma ISO 9978 Sealed Radioactive Sources Leakage Test Methods e ensaio metalográfico. O procedimento desenvolvido para a selagem das sementes de 125I mostrou-se eficiente, atendendo a todos os requisitos estabelecidos na norma ISO 2919. Os resultados apresentados neste trabalho possibilitaram a elaboração de rotinas de fabricação segundo as orientações apresentadas na resolução RDC nº 59 Boas Práticas de Fabricação de Produtos Médicos da ANVISA - Agência Nacional de Vigilância Sanitária. / The prostate cancer, which is the second cause of death by cancer in men, overcome only by lung cancer, is a problem of public health in Brazil. Brachytherapy is among the possible available treatments for prostate cancer, in which small seeds containing 125I radioisotope are implanted in the prostate. The seed consists of a titanium sealed capsule with 0.8 mm external diameter and 4.5 mm length, containing a central silver wire with adsorbed 125I. The plasma arc welding is one of the viable techniques for the sealing process. The equipment used in this technique is less costly than in other processes. The main objective of this work was the development and the validation of the welding procedure using plasma welding process and the elaboration of a sealing routine according to Good Manufacturing Practices. The development of this work has presented the following phases: cut and cleaning of the titanium material, determination of the welding parameters, development of a device for holding the titanium tube during the welding process, validation of sealed sources according to ISO 2919 Sealed Radioactive Sources - General Requirements and Classification, leakage test according to ISO 9978 Sealed Radioactive Sources - Leakage Test Methods and metallographics assays. The developed procedure, to seal 125I seeds using plasma welding process, has shown to be efficient, satisfying all the established requirements of ISO 2919. The results obtained in this work have given the possibility to establish a routine production process according to the orientations presented in resolution RDC nº 59 - Good Manufacturing Practices to Medical Products of the ANVISA - National Agency of Sanitary Surveillance.

As expectativas da Organização Mundial de Saúde para o ano de 2030 são que o número de mortes por câncer seja de aproximadamente 13,2 milhões, evidenciando a elevada parcela desta doença no problema de saúde mundial. Com relação ao câncer de próstata, de acordo com o Instituto Nacional do Câncer, o número de casos diagnosticados no mundo em 2012 foi de aproximadamente 1,1 milhão, enquanto que no Brasil os dados indicam a incidência de 68 mil novos casos. O tratamento deste tipo de neoplasia pode ser realizado com cirurgia (prostatectomia) ou radioterapia. Dentre a radioterapia, podemos destacar a técnica de braquiterapia, a qual consiste na introdução (implante) de pequenas fontes radioativas (sementes) no interior da próstata, onde será entregue um valor elevado de dose no volume de tratamento e baixa dose nos tecidos ao redor. No Brasil, a classe médica estima uma demanda de aproximadamente 8000 sementes/mês, sendo o custo unitário de cada semente de pelo menos U$ 26,00. A Associação Americana de Físicos na Medicina publicou alguns documentos descrevendo quais parâmetros e análises devem ser realizadas para avaliações da distribuição de dose, como por exemplo, os parâmetros Constante de taxa de dose, Função radial e Função de anisotropia. Estes parâmetros podem ser obtidos através de medidas experimentais da distribuição de dose ou por simulações computacionais. Neste trabalho foram determinados os parâmetros dosimétricos da semente OncoSeed-6711 da empresa Oncura-GEHealthcare e da semente desenvolvida pelo Grupo de Dosimetria de Fontes de Braquiterapia do Centro de Tecnologia das Radiações (CTR IPEN-CNEN/SP) por simulação computacional da distribuição de dose utilizando o código MCNP5, baseado no Método de Monte Carlo. A semente 6711 foi modelada, assim como um sistema dosimétrico constituído por um objeto simulador cúbico de 30x30x30 cm3 preenchido com água. Os valores obtidos da semente 6711 foram comparados com alguns apresentados na literatura, onde o parâmetro Constante de taxa de dose apresentou erro relativo em relação ao valor publicado no TG- 43 de 0,1%, sendo que os outros parâmetros analisados também apresentaram boa concordância com os valores publicados na literatura. Deste modo, pode-se considerar que os parâmetros utilizados nas simulações (espectro, modelagem geométrica e avaliação de resultados) estão compatíveis com outros estudos, sendo estes parâmetros também utilizados nas simulações da semente do IPEN. Considerando as análises de incerteza estatística, os valores obtidos da semente do IPEN são semelhantes aos valores da semente 6711. / Expectations of the World Health Organization for the year 2030 are that the number of cancer deaths is approximately 13.2 million, reflecting the high proportion of this disease in global health issue. With respect to prostate cancer, according to the National Cancer Institute, the number of cases diagnosed worldwide in 2012 was approximately 1.1 million, while in Brazil the data demonstrated the incidence of 68,000 new cases. The treatment of cancer can be performed with surgery (prostatectomy) or radiation therapy. Among radiotherapy, we can highlight the brachytherapy technique, which consists in the introduction of small radioactive sources (seeds) within the prostate, which is delivered a high dose value in the treatment volume and low dose in the surrounding tissues. In Brazil, the medical profession estimates a demand of approximately 8000 seeds / month, and the unit cost of each seed at least US $ 26.00. The AAPM protocol TG-43 recommend the dose-rate constant, radial dose function and anisotropy function for dosimetric analysis LDR brachytherapy seeds. In this work, Monte Carlo simulations were performed in order to assess the dosimetric parameters of the OncoSeed-6711, manufactured by Oncura-GEHealthcare, and a seed developed by Radiation Technology Center, using the MCNP5 code. A 6711 seed, anIPEN seed and the 30x30x30cm3phantom filled with water were modeled to simulatethe dose distribution. The 6711 seed parameters were compared with literature, and the results presented relative error less than 0.1% for &Lambda;. In comparison with the 6711 seed, the IPEN model seed dosimetric parameters were similar, account the statistical uncertainty.