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

Published online by Cambridge University Press:  15 August 2018

Mehmet Bahadır Çelik ,
Nezahat Olacak ,
Songül Barlaz Us  and
Emin Tavlayan
Mehmet Bahadır Çelik
Affiliation:
Department of Radiation Oncology, Mersin State Hospital, Mersin, Turkey
Nezahat Olacak
Affiliation:
Department of Radiation Oncology, Ege University Faculty of Medicine, İzmir, Turkey
Songül Barlaz Us*
Affiliation:
Department of Radiation Oncology, Mersin University Faculty of Medicine, Mersin, Turkey
Emin Tavlayan
Affiliation:
Department of Radiation Oncology, Ege University Faculty of Medicine, İzmir, Turkey
*
Author for correspondence: Songül Barlaz Us, Mersin University, 33100, Mersin, Turkey, E-mail: barlaz@gmail.com
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Abstract

Aim

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 depth–dose 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 2·31% 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 considering air gaps may cause erroneous dose distributions due to heterogeneity of tissue.

Keywords

brachytherapydose distributionGafchromic EBT3 filmtissue heterogeneity
Type
Original Article
Information
Journal of Radiotherapy in Practice , Volume 17 , Issue 4 , December 2018 , pp. 411 - 416
Copyright
© Cambridge University Press 2018 

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