Evaluation of air cavities on dose distributions with air-filled apparatuses having different volumes using Gafchromic EBT3 films in brachytherapy

WOS: 000450073600010Aim: The data used in brachytherapy planning are obtained from homogeneous mediums. In practice, the heterogeneous tissues and materials affect the dose distribution of brachytherapy. It is aimed to investigate the effect of air cavities on brachytherapy dose distribution using a specially designed device. Material and methods: In this study, the special device designed with different volumes of air and water to be irradiated and measured at different depths using EBT3 Gafchromic films. EBT3 Gafchromic films were preferred for this study because they can be cut to the shape of the experimental geometry, are water resistance and double directional usability. Results: In our study, sudden dose increases and decreases were observed at the water-air-water interfaces. Increases were 9, 11.8 and 15% in the 13, 18 and 22 mm apparatus, respectively. These effects were expected and the results were consistent with the literature and within the tolerance limits stated in the clinical dose guidelines. The most important result is that the percent depthdose curve of the radiation passing through the air to the water and only passing through the water medium is different The average differences were 1.97, 2.97 and /31% for the 13, 18 and 22 mm apparatus, respectively. Conclusion: Although the effect of heterogeneity may be neglected according to clinical guidelines, it is suggested that the dose effect of heterogeneity is taken into account so that the dose can be estimated sensitively. Brachytherapy plans using dose data without unisidering air gaps may cause erroneous dose distributions due to heterogeneity of tissue

Dosimetric Evaluation of The Tomotherapy, Non-coplanar and Coplanar IMRT Plannings for Total Scalp Irradiation

In this study, the dosimetric effects of the Tomotherapy, noncoplanar and coplanar IMRT plannings were evaluated for the total scalp irradiation. Tomotherapy based and linac based IMRT plans were compared for 61 years old female patient with multipl myeloma. Two different linac based IMRT plans which are coplanar and noncoplanar were performed for total scalp irradiation. 20 Gy was given to the PTV volume. Firstly, homogeneity index and conformity index values were calculated for PTV. Secondly, the doses of organ at risk (OaR) which are lenses, brain, brainstem and parotid glands were dosimetrically evaluated. While, tomotherapy plan was more homogenous, noncoplanar plan was more conformal than the others. Our study figure out that the OaR doses can be decreased by using tomotherapy based IMRT. However, the treatment time was increased when the tomotherapy based IMRT used for treatment. Tomotherapy based IMRT can be used for total scalp irradiation with respect to OaR. [Med-Science 2015; 4(2.000): 2155-64