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Dose Distribution of Oesophagus Stents Measured by EBT2 Film Dosimetry

B Poppe

D Poppinga1,2, A Schoenfeld1,2, N Chofor1,2, B Poppe1,2*, (1) University Oldenburg, Oldenburg, Germany (2) Pius Hospital, Oldenburg, Germany

SU-E-T-224 Sunday 3:00:00 PM - 6:00:00 PM Room: Exhibit Hall

Purpose: The purpose of this study is to investigate the dose enhancement at oesophagus stents made of nitinol. The material is a nickel titan alloy with an effective atomic number of 26. Because of the increased atomic number in comparison to the human body, dose enhancement in surrounding tissue is expected.

Methods: The relative dose distribution around the stent was measured in a water phantom. To simulate the air cavity within the oesophagus, a styrodur cylinder was placed inside the stent. The stent was held with a circular PMMA holder. An EBT2 film was wrapped around the stent to measure the relative radial dose distribution.
The setup was irradiated with a 6MV photon beam (Siemens Primus) and a field size of 5cmx5cm. The distance between source and centre of the stent was 100cm.
The EBT2 films were digitized at a scanning resolution of 72dpi using an Epson 10000XL flatbed scanner with a transparency unit. Furthermore, the films were fixed in a frame to prevent Newton rings in the scanned image.

Results: The dose increases in all directions around the stent. With approximately 18%, the highest increase is caused on the proximal side of the stent. On the backside the dose enhancement is approximately 10%.

Conclusions: Dose enhancements around a stent are detectable and one should be aware of it's occurence in the radiotherapeutical treatment of oesophageal cancer. Because of the enhancement in all directions healthy tissue may be affected.

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