(Tuesday, 7/31/2018) 1:15 PM - 1:45 PM
Room: Exhibit Hall | Forum 7
Purpose: Esophageal stents are commonly used to palliate dysphagia in patients with esophageal cancer. There is concern about the safety of combining stents with radiotherapy (RT) due to the risk of stent migration and potential impact of the stent on dosimetric parameters. The aim of this study was to investigate the RT dose perturbations caused by esophageal stents in patients undergoing volumetric modulated arc therapy (VMAT).
Methods: A silicone-coated, Nitinol wire-braided esophageal stent (WallFlex Fully Covered; Boston Scientific) was examined in this study. The stent had an outer diameter of 18 mm and length of 150 mm. The stent was centered in a 20-cm×15-cm×10-cm water phantom. Computed tomography images of the phantom were obtained using a 2.5-mm slice thickness and 0.5-mm axial resolution. A cylindrical planning target volume with 4-cm diameter and 5-cm length was placed in the center of the phantom surrounding the stent. A 6-MV VMAT plan was generated with Eclipse using the Anisotropic Analytical Algorithm (version 11.0.31) for dose calculations. Gafchromic EBT3 films were placed abutting the stent and the phantom was irradiated with the VMAT plan. Dose distributions were compared using Film QA Pro (version 5.0).
Results: The mean (± standard deviation) percentage difference of the dose measured on film versus the dose calculated by the treatment planning software was -1.0%±1.4% at a distance of 2.5 mm from the stent, -1.5%±1.7% at a distance of 5 mm from the stent, -1.5%±2.1% at a distance of 7.5 mm from the stent, and -2.1%±1.7% at a distance 10 mm from the stent.
Conclusion: The measured dose distribution at distances greater than 2.5 mm from the stent agrees with the dose calculated by the treatment planning system. Monte Carlo simulations are warranted to investigate dose perturbations at distances less than 2.5 mm from the stent.
Keywords
Radiochromic Film, Intensity Modulation, Dosimetry
Taxonomy
TH- External beam- photons: Quality Assurance - VMAT
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