Impacto de la radiación de fuga a través del sistema de colimación multihojas en tratamientos de radioterapia de intensidad modulada

Para impartir la dosis de prescripción en tratamientos de radioterapia de intesidad modulada (IMRT), en general, se requerirá un mayor número de unidades monitor (UM) en comparación con impartir la misma dosis en un campo no modulado. Como consecuencia de esto, la dosis recibida por el paciente debido a la radiación de fuga (F) a través del colimador multiho-jas (MLC) incrementará. El objetivo de este trabajo es evaluar el impacto dosimétrico que pequeñas diferen-cias en la radiación de fuga podrían tener en trata-mientos de IMRT

Investigation of EBT3 radiochromic film’s response to humidity

Purpose: The aim of this work is to investigate the effects of immersing EBT3 radiochromic film in water and to evaluate its contribution to the total uncertainty in dose determination. Materials and methods: We used 3 cm 9 3 cm EBT3 radiochromic films irradiated in the range of 0–70 Gy to study the impact of water immersion on the change in net optical density. These films were placed in a water container for a period of 24 h. The net optical density was measured before (0 h) and after of the immersion in water (1, 3, 6, 12, 18, and 24 h). The absorbance spectrum of the EBT3 radiochromic film was measured at 0 h and 24 h after immersion in water. The uncertainty in dose determination due to the effects of keeping the EBT3 radiochromic film submerged in water at 0, 1, and 24 h were recorded in the red, green, and blue channels. Results: We observed an increase in the net optical density as an effect on the film due to its immersion in water. The penetration of the water at the edges of the radiochromic film was observed to be a function of time during which the film remained in the water. On the other hand, the penetration of water at the edges of the film was found to be independent of irradiation dose. Conclusions: EBT3 radiochromic film is found more resistant to water penetration through the edges than its predecessors. However, there is evidence that suggest that liquid water damage the Nylon cover layer of the film by changing its optical properties. Therefore, it is recommended to build a new calibration curve for radiochromic films for a specific situation involving dose measurements in liquid water.UAEMex INN

calibración de Unidades hounsfield en términos de números atómicos efectivos y densidades electrónicas usando CT de energía dual

El cálculo de dosis con algoritmos Monte Carlo (MC) utiliza imágenes de CT del paciente. A partir de las Unidades Hounsfield (HU) es posible obtener información sobre la densidad electrónica (ρe) y composición elemental de cada tejido. Un cálculo preciso de dosis y una adecuada corrección por inhomogeneidades es parcialmente determinada por la precisión de la calibración de las HU en términos de estos parámetros. En este trabajo se presentan resultados de calibración de HU en términos de números atómicos efectivos (Zeff) y ρe relativas utilizando un maniquí con insertos tejido-equivalente y estudios de tomografía computarizada (CT) de energía dual

Investigation of EBT3 radiochromic film’s response to humidity

Purpose: The aim of this work is to investigate the effects of immersing EBT3 radiochromic film in water and to evaluate its contribution to the total uncertainty in dose determination. Materials and methods: We used 3 cm 9 3 cm EBT3 radiochromic films irradiated in the range of 0–70 Gy to study the impact of water immersion on the change in net optical density. These films were placed in a water container for a period of 24 h. The net optical density was measured before (0 h) and after of the immersion in water (1, 3, 6, 12, 18, and 24 h). The absorbance spectrum of the EBT3 radiochromic film was measured at 0 h and 24 h after immersion in water. The uncertainty in dose determination due to the effects of keeping the EBT3 radiochromic film submerged in water at 0, 1, and 24 h were recorded in the red, green, and blue channels. Results: We observed an increase in the net optical density as an effect on the film due to its immersion in water. The penetration of the water at the edges of the radiochromic film was observed to be a function of time during which the film remained in the water. On the other hand, the penetration of water at the edges of the film was found to be independent of irradiation dose. Conclusions: EBT3 radiochromic film is found more resistant to water penetration through the edges than its predecessors. However, there is evidence that suggest that liquid water damage the Nylon cover layer of the film by changing its optical properties. Therefore, it is recommended to build a new calibration curve for radiochromic films for a specific situation involving dose measurements in liquid water.UAEMex INN