León-Marroquín Elsa Y, Lárraga-Gutiérrez José M, Herrera-González J Alfredo, Camacho-López Miguel A, Villarreal Barajas José E, García-Garduño Olivia A
Laboratorio de Fotomedicina, Biofotónica y Espectroscopia Láser de Pulsos Ultracortos, Facultad de Medicina, Universidad Autónoma del Estado de México, Toluca, México.
Laboratorio de Física Médica & Unidad de Radiocirugía, Instituto Nacional de Neurología y Neurocirugía, Mexico City, México.
J Appl Clin Med Phys. 2018 May;19(3):283-290. doi: 10.1002/acm2.12337. Epub 2018 Apr 29.
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.
We used 3 cm × 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.
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.
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.
本研究旨在探究将EBT3放射变色薄膜浸入水中的影响，并评估其对剂量测定总不确定度的贡献。
我们使用尺寸为3 cm×3 cm、在0 - 70 Gy范围内辐照的EBT3放射变色薄膜，研究水浸对净光密度变化的影响。这些薄膜被放置在一个盛水容器中24小时。在浸入水之前（0小时）以及浸入水后1、3、6、12、18和24小时测量净光密度。在浸入水0小时和24小时后测量EBT3放射变色薄膜的吸收光谱。记录在0、1和24小时将EBT3放射变色薄膜浸没在水中的影响所导致的剂量测定不确定度，分别在红、绿和蓝通道进行记录。
我们观察到由于薄膜浸入水中，其净光密度增加。观察到放射变色薄膜边缘处水的渗透是薄膜在水中停留时间的函数。另一方面，发现薄膜边缘处水的渗透与辐照剂量无关。
发现EBT3放射变色薄膜比其前代产品更能抵抗水从边缘渗透。然而，有证据表明液态水通过改变其光学性质损坏了薄膜的尼龙覆盖层。因此，建议针对涉及液态水中剂量测量的特定情况，为放射变色薄膜建立新的校准曲线。
