ABSTRACT
Aim of Study: The report of the task group number 43(TG-43) of AAPM has been known as the most common method to obtain the dose distribution around brachytherapy sources. The error caused by independent obtaining and rounding and combinational error caused by algebraic operations of each TG-43 dosimetry parameters increase the total error in the calculation of the dose distribution around the brachytherapy sources. The aim of the present study is to present and evaluate a matrix-based approach for simplifying and reducing calculation errors. Materials and Methods: In this study, the simulation method with MCNPX code was used to obtain the dose distribution. Four sources were simulated, and the dose matrix around these sources was obtained. Finally, the dose distribution obtained from the matrix-based method was compared with the dose distribution obtained from the method of TG-43 report. Results: There is little difference between the values obtained from the two methods in some points. Absolute mean differences between the values obtained by these two methods were 1.4% for the 60Co, 3.52% for the 137Cs, 2.67% for the 192Ir, and 2.42% for the 103Pd sources. The advantage of the matrix-based method is its simple computing process and less computation time. Conclusion: Considering that the comparison of brachytherapy sources is not raised in calculations of treatment planning systems and also considering the more uncertainty in the calculation of the dose distribution in TG-43 method, it is recommended that dose distribution obtained from matrix-based method be used as input for treatment planning systems.
ABSTRACT
En marzo del año 2005, la Fundación Bengoa comprometió a diversos profesionales para asumir los retos de la alimentación y nutrición del país. Así, el 11 de julio de 2005, se realizó la reunión fundacional del grupo de trabajo sobre Transición Alimentaria y Nutricional (grupo TAN) con la presencia de Mercedes López de Blanco, Melania Izquierdo y Alexander Laurentin. El Grupo TAN es un espacio de encuentro interdisciplinario e interinstitucional, que sirve para la reflexión y la discusión de ideas, con la finalidad de identificar e instrumentar estrategias relacionadas con la transición alimentaria y nutricional. En Venezuela esta transición ha ocasionado una doble carga, debido a la superposición del sobrepeso con la desnutrición. Se decidió enfrentar la carga del sobrepeso. La primera actividad fue un foro realizado en noviembre de 2005, donde se detectó que grupos de investigación del país, usan diferentes criterios y valores límite para identificar los factores de riesgo y diagnosticar las enfermedades relacionadas con la nutrición, particularmente en niños, niñas y adolescentes. El grupo, con el enfoque investigación acción, enfrentó este problema: una encuesta electrónica detectó variabilidad en la utilización de las referencias, inconsistencia entre la referencia y las variables utilizadas, y un déficit en la evaluación de los hábitos de vida; por lo que se diseñó un taller de actualización (que incluye un caso clínico). Esta actividad ha beneficiado a más de un centenar de pediatras venezolanos y ha formado una decena de facilitadores en varias regiones del país(AU)
In March 2005, the Bengoa Foundation committed a number of professionals to the challenge of food and nutritional issues in Venezuela. On July 11th 2005, the founding meeting of the TAN group (short for Nutrition Transition Task Group) took place with the presence of Mercedes López de Blanco, Melania Izquierdo and Alexander Laurentin. The TAN group is an interdisciplinary and inter institutional group that debates and discusses ideas, in order to identify and develop strategies on nutrition transition. In Venezuela, this transition has resulted in the double burden of malnutrition, as overweight coexists with under nutrition. The task group decided to address the overweight problem. The first activity was a forum held on November 2005, where it was detected that various research groups in Venezuela use different criteria and cut-off limits to identify risk factors and diagnose diseases related to nutrition, particularly in children and adolescents. The TAN group, with an action research approach, addressed this problem: An electronic survey detected variability in the use of the references, inconsistencies between a particular reference and the variables used, and a deficit on lifestyle evaluation; therefore, a workshop was designed (using a clinical case). This activity has benefited a hundred of Venezuelan pediatricians and trained ten facilitators across the country(AU)