Gynecological brachytherapy for postoperative endometrial cancer: dosimetric analysis (Ir-192 vs Co-60)

Introduction. Endovaginal brachytherapy treatment dosimetry differences were studied using Ir-192 or Co-60 sources for postoperative endometrial cancer. Materials and methods. A prospective descriptive study was conducted. Thirty-six dosimetry plans of different patients were studied (15 by Ir-192 and 21 by Co-60). Variables studied included D2cc Rectum, D2cc Bladder, D2cc Sigmoid, dose percentage at point 0 (applicator surface on the top of the cylinder) and dose percentage at point 1 (5 mm deep on the top of the cylinder). A comparative analysis was performed of the values obtained from each variable between Ir-192 and Co-60 treatments. We compared average of each variables between Iridium and Cobalt by T Student for independent samples (SPSS 22). Results. here were no significant differences on using Ir-192 or Co-60 by variables, except for dose percentage at point 1 in which we detected significant differences (Table 1). Discussion. Brachytherapy treatment dosimetry plans are similar using Ir-192 or Co-60, except dose percentage at point 1. In the scientific literature, some differences exist and there are some advantages in using cobalt (AU)

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Development of a mouse computational model for MCNPx based on Digimouse (r) images and dosimetric assays

ABSTRACT The aim of this study was to create and test a new mice 3D-voxel phantom named DM_BRA for mice and human first-estimation radiopharmaceutical dosimetry. Previously, the article reviews the state-of-art in animal model development. Images from Digimouse CT database were used in the segmentation and on the generation of the voxelized phantom. Simulations for validation of the DM_BRA model was performed at 0.015, 0.1, 0.5, 1 and 4 MeV photons with heart-source. Specific Absorbed Fractions (SAF) data were compared with literature data. The organ masses of DM_BRA correlated well with existing models based on the same dataset; however, few small organ masses hold significant variations. The SAF data in most simulated cases were statistically equal to a significant level of 0.01 to the reference data.

Comparing CTVs for permanent prostate brachytherapy

Background and purpose: To delineate the clinical target volume (CTV) in low dose rate (LDR) brachytherapy for prostate cancer, American Brachytherapy Society (ABS) recommends a CTV = prostate. ESTRO advocates a CTV = prostate + 3 mm excluding rectum and many authors use and recommend other different CTVs. This study aims to: (1) evaluate the appropriateness of these recommendations and (2) test the applicability of seed distributions on the different CTVs and contrast the dosimetric differences. Materials and methods: Ninety-eight patients treated with 125I seeds (dose 145 Gy; CTV = prostate) were studied. We established for every patient: (1) risk of extraprostatic extension (EPE), (2) adequacy of original plan to an extended CTV with 3 mm-margin (3) a new planning and seed distribution for this CTV and (4) comparison of dosimetry of both plans. Results: Mean risk of EPE was 28.46 %. Original plan, when applied to the extended CTV, resulted in unsatisfactory dosimetry. A plan was generated for the 98 extended CTVs meeting all dosimetric specifications. Conclusions: The risk of EPE is high enough to consider a 3 mm-margin around prostate necessary for all cases. A CTV = prostate + 3 mm except rectum as ESTRO recommends is feasible and would adjust planning to the most probable extension of the tumor (AU)

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Resultados de implante de semillas de iodo-125 con sistema de preplanificación en 250 pacientes con carcinoma de próstata / Results of 125-Iodine seed implant with preplanning system in 250 patients with prostate cancer

Objetivo: Revisar la experiencia con implantes permanentes de semillas de I-125 en carcinoma de próstata y el resultado a los 8 años de comenzar la técnica. Material y métodos: De 2002 a 2007 hemos realizado 250 implantes con braquiterapia de baja tasa con RapidStrand® y sistema de preplanificación. La edad media fue 68 años (49-78). El PSA medio fue 7,32 (2,31-14,6), 98% T1-T2a, 96% Gleason ≤ 6, 81% de bajo riesgo y 19% de riesgo intermedio (10 de estos últimos recibieron 46 Gy de radioterapia externa). Un 42% recibieron hormonoterapia. Resultados: Con seguimiento medio de 48 meses, 14 pacientes (5,7%) tuvieron recaída bioquímica (RB). En 11 pacientes (4,5%) con teórica RB el PSA descendió espontáneamente sin tratamiento. La supervivencia actuarial sin recaída bioquímica a 5 años fue del 91% (92% bajo riesgo, 86% riesgo intermedio); 92 vs 81% en pacientes con PSA < 10 vs > 10 (p < 0,05). Hubo complicaciones rectales G2 en el 0,6%, sondaje vesical en un 6,5%; el 60% conservaron la función sexual. El V100 medio fue del 89% y el D90 143 Gy. Conclusión: El resultado en carcinoma de próstata de bajo riesgo mediante semillas de Iodo-125es muy bueno con muy pocas complicaciones. Las elevaciones de PSA deberían ser controladas antes de dar tratamiento de rescate (AU)

Introduction: We review the experience with prostate carcinoma patients treated with permanent implants of 125-I seeds and the outcome eight years after the beginning of this technique. Material and methods: From 2002 to 2007 we have performed 250 implants with LDR brachytherapy with RapidStrand® and preplanning system. Mean age was 68 (49-78). Mean PSA was 7.32 (2.31 - 14.6). T1-T2a was the stage in 98%, and Gleason ≤ 6 in 96%. Low risk cases were 81% and intermediate risk 19% (ten of them received 46 Gy EBRT). Hormonal treatment was used in 42%. Results: With a mean follow-up of 48 months, 14 patients (5.7%) showed biochemical failure (BF). Eleven patients (4.5%) with theoretical BF were observed and PSA decreased without treatment. Actuarial PSA relapse-free survival at 5 years was 91%, (92% low risk, 86% intermediate cases), and 92% vs 81% with PSA <10 vs >10 (p < 0.05). Rectum complications were G2 in0 .6%. A urinary catheter was necessary in 6.5%. Sexual function was conserved in 60%. Mean V100 was 89% and D90 143 Gy. Conclusion: The outcome of patients with low risk prostate carcinoma treated with I-125 seed is very good with very low complications rate. Cases with PSA bounces should be controlled before starting a salvage treatment (AU)

Estudo comparativo de dosimetria computacional entre modelos homogêneos e um modelo voxel em mamografia: uma discussão de aplicações em testes de constância e cálculo de dose glandular em pacientes / Comparative study of computational dosimetry involving homogeneous phantoms and a voxel phantom in mammography: a discussion on applications in constancy tests and calculation of glandular dose in patients

OBJETIVO: Comparar dados de dosimetria e fluência de fótons entre diferentes modelos de mama, discutindo as aplicações em testes de constância e estudos dosimétricos aplicados à mamografia. MATERIAIS E MÉTODOS: Foram simulados diferentes modelos homogêneos e um modelo antropomórfico de mama tipo voxel, sendo contabilizadas: a dose total absorvida no modelo, a dose absorvida pelo tecido glandular/material equivalente, e a dose absorvida e a fluência de fótons em diferentes profundidades dos modelos. Uma câmara de ionização simulada coletou o kerma de entrada na pele. As combinações alvo-filtro estudadas foram Mo-30Mo e Mo-25Rh, para diferentes potenciais aceleradores de 26 kVp até 34 kVp. RESULTADOS: A dose glandular normalizada, comparada ao modelo voxel, resultou em diferenças entre -15 por cento até -21 por cento para RMI, -10 por cento para PhantomMama e 10 por cento para os modelos Barts e Keithley. A variação dos valores da camada semirredutora entre modelos foi geralmente inferior a 10 por cento para todos os volumes sensíveis. CONCLUSÃO: Para avaliar a dose glandular normalizada e a dose glandular, em mamas médias, recomenda-se o modelo de Dance. Os modelos homogêneos devem ser utilizados para realizar testes de constância em dosimetria, mas eles não são indicados para estimar a dosimetria em pacientes reais.

OBJECTIVE: To compare data regarding dosimetry and photons fluence in different breast phantoms, discussing constancy tests and dosimetry applied to mammography. MATERIALS AND METHODS: Different homogeneous breast phantoms and one anthropomorphic voxel phantom were developed for collection of data regarding total absorbed dose in the phantom, absorbed dose in the glandular tissue material-equivalent, absorbed dose and photons fluence at different depths in the phantoms. A simulated ionization chamber collected the entrance skin kerma. Target-filter combinations (Mo-30Mo and Mo-25Rh) were studied for different accelerating potentials of 26 kVp to 34 kVp. RESULTS: As compared with the voxel phantom, the normalized glandular dose resulted in differences from -15 percent to -21 percent for RMI, -10 percent for PhantomMama, and 10 percent for the Barts and Keithley models. The half-value layer variation was generally < 10 percent for all the sensitive volumes. CONCLUSION: The phantom proposed by Dance is recommended for evaluating the glandular dose and normalized glandular dose in a standard breast. Homogeneous phantoms should be utilized for constancy tests in dosimetry, but they are not appropriate for estimating dosimetry in actual patients.

Braquiterapia endobrônquica de alta taxa de dose: estudo dosimétrico / High dose-rate endobronchial brachytherapy: a dosimetric study

OBJETIVO: Avaliar a distribuição de dose em diferentes situações de braquiterapia endobrônquica de alta taxa de dose, com foco principalmente nos volumes de altas doses, e tentar definir situações de melhor ou pior distribuição de dose que possam servir de guia na prática clínica. MATERIAIS E MÉTODOS: Estudo teórico, simulando braquiterapia endobrônquica de alta taxa de dose utilizando dois cateteres, com variação da extensão de carregamento, angulação entre os cateteres, profundidade de cálculo e o intervalo entre as paradas da fonte. Com prescrição de 7,5 Gy, foram calculados os volumes englobados pelas isodoses correspondentes a 100 por cento, 150 por cento e 200 por cento da dose prescrita (V100, V150 e V200, respectivamente) e as razões V150/V100 e V200/V100. RESULTADOS: Os volumes aumentaram com o aumento da extensão de carregamento dos cateteres, profundidade de cálculo e angulação, com tendência a um aumento proporcionalmente menor para angulações maiores. As relações V150/V100 e V200/V100 foram, em geral, homogêneas, ao redor de 0,50 e 0,30, respectivamente. CONCLUSÃO: A distribuição de dose na situação considerada padrão é em geral adequada. Nenhum parâmetro específico que pudesse ser relacionado à maior toxicidade foi identificado. Recomendamos uma avaliação rápida da qualidade do implante por meio da análise das relações V150/V100 e V200/V100.

OBJECTIVE: To evaluate the dose distribution in different situations of high dose-rate endobronchial brachytherapy, focusing especially on high-dose volumes, and try to identify better or worse situations in terms of dose distribution to aid as guidance in the clinical practice. MATERIALS AND METHODS: Theoretical study simulating high dose-rate endobronchial brachytherapy utilizing two catheters, varying the loading extent, angle between the catheters, prescription depth, and source step. With a prescription dose of 7.5 Gy, the volumes involved by the 100 percent, 150 percent and 200 percent isodoses (V100, V150 and V200, respectively) and V150/V100 and V200/V100 ratios were calculated. RESULTS: There was a volume enhancement with larger loaded lengths, increase in prescription depth and angles, with a tendency towards a proportionally smaller increase with larger angulations. In general, the V150/V100 and V200/V100 ratios were homogeneous, respectively around 0.50 and 0.30. CONCLUSION: Overall, the dose distribution in the standard situation was appropriate. No specific parameter that could be related to a higher toxicity was identified. The authors recommend a swift evaluation of the treatment quality through the analysis of the V150/V100 and V200/V100 ratios.

Elaboración de dosímetros de alanina y sus posibles aplicaciones en riesgos profesionales / Elaboração de dosímetros de alanina e suas possíveis aplicações em riscos profissionais / Elaboration of alanine dosimeters and their possible applications in professional risks

Desarrollar dosímetros de alanina y alanina/parafina con miras a atender la creciente utilización de la radiación ionizante a nivel tecnológico. Materiales y métodos. Los radicales libres producidos por la radiación ionizante en la alanina se detectan por resonancia magnética electrónica (ESR); la parafina se utiliza como aglutinante. La metodología de preparación incluye: elaboración, irradiación, lectura y análisis de datos para los dos tipos de dosímetros. Los espectros ESR estudiados corresponden a dosímetros de alanina con masas entre 60 y 120 mg e irradiados con dosis de 10 y 20 Gy, y dosímetros de alanina/parafina de 160 mg e irradiados con diferentes dosis en un haz de fotones de 4 MV. Resultados. La intensidad de los espectros (las cinco líneas características) depende de las dosis recibidas por los dosímetros y su relación es lineal. Con alanina pura y una dosis de 10 Gy la mínima cantidad requerida fue 120 mg; la compactación del cilindro lograda no fue suficiente para evitar la fragmentación parcial del dosímetro. La parafina no tiene señal paramagnética; en los dosímetros de alanina/parafina (cilindros de longitud 13 mm y diámetro 3.5 mm, en la relación 80:20, y buena dureza) se estudió la respuesta señal ESR-dosis en un rango entre 20 y 120 Gy. Conclusiones. Los cilindros de alanina/parafina fabricados tienen una dureza apropiada para ser manipulados como dosímetros de radiación ionizante; su reproducibilidad y la efectividad en la acumulación de dosis es buena...

Elaboration of alanine dosimeters and their possible applications in professional risks. Objective. To develop dosimeters of alanine and alanine/paraffin in order to meet the growing use of ionizing radiation at the technological level. Materials and methods. Free radicals produced by ionizing radiation in alanine are detected by electron spin resonance (ESR); paraffin is used as binder. The methodology ofpreparation includes: elaboration, irradiation, data collection and data analysis for the two types of dosimeters. The ESR spectra studied correspond to alanine dosimeters with masses between 60 and 120 mg and irradiated with doses of 10 and 20 Gy, and alanine/paraffin dosimeters with 160 mg and irradiated with different doses in a beam of photons 4 MV. Results. The intensity of the spectra (thecharacteristic five lines) depends on the doses received by the dosimeters and their relationship is linear. With pure alanine and a dose of 10 Gy, the minimum amount required was 120 mg; the achieved cylinder compaction was not sufficient to avoid the partial fragmentation of the dosimeter. Paraffin has no paramagnetic signal; in the alanine/paraffin dosimeters (cylinders of 13 mm in length and 3.5 mm of diameter, with a ratio 80:20, and good hardness) the response signal ESR-dose was studied in a range between 20 and 120 Gy. Conclusions. The cylinders of alanine/paraffin manufactured have an appropriate hardness to be handled as dosimeters of ionizing radiation; their reproducibility and effectiveness in the accumulation of dose is good...

Elaboração de dosímetros de alanina e suas possíveis aplicações em riscos profissionais. Objetivo. Desenvolver dosímetros de alanina e alanina/parafina com a finalidade de satisfazer a crescente utilização de radiações ionizantes ao nível tecnológico. Materiais e métodos. Os radicais livres produzidos pela radiação ionizante na alanina são detectados por ressonância magnética eletrônica (EPR); a parafina é utilizada como aglutinante. O método de preparação inclui: elaboração, irradiação, leitura e analise dos dados para os dois tiposde dosímetros. Os espectros ESR estudados correspondem a dosímetros de alanina com massas entre 60 e 120 mg e irradiados com doses de 10 e 20 Gy, e dosímetros de alanina/parafina de 160 mg e irradiados com diferentes doses de um feixe de fótons de 4 MV. Resultados.A intensidade dos espectros (as cinco linhas características) depende das doses recebidas pelos dosímetros e sua relação é linear. Com lanina pura e uma dose de 10 Gy a mínima quantidade requerida foi de 120 mg; a compactação do cilindro alcançada não foi suficiente para evitar a fragmentação parcial do dosímetro. A parafina não tem sinal paramagnético; nos dosímetros de alanina/parafina (cilindros de 13 mmde comprimento e 3,5 mm de diâmetro, na proporção 80:20 e boa dureza) foi estudada a resposta a sinal ESR-dose em um intervalo entre 20 e 120 Gy. Conclusões. Os cilindros de alanina/parafina fabricados têm uma dureza adequada para ser tratados como dosímetros de radiação ionizante; sua reprodutibilidade e eficiência no acúmulo de dose é bom...