Program Information
Dose Perturbation Study of Self-Expandable Metal and Polyester Esophageal Stents in Proton Therapy Beams
S Lee1*, S Jalaj2 , C McGaw2 , B K John2 ,J S Scolapio2 , J C Munoz2, Z Li1 , (1) University of Florida Proton Therapy Institute, Jacksonville, FL, (2) division of Gastoenterology, Department of Medicine, University of Florida, Jacksonville, FL
Presentations
SU-E-T-115 Sunday 3:00PM - 6:00PM Room: Exhibit HallPurpose:This work investigates dose perturbations due to Self-expandable metal and polyester esophageal stents undergoing proton radiotherapy for esophageal cancer.
Methods:Five commercially available esophageal stents made of nitinol (Evolution, Wallflex and Ultraflex), stainless steel (Z-Stent) and polyester (Polyflex) were tested. Radiochromic film (GafChromic EBT3 film, Ashland, Covington, KY) wrapped around a stent and a 12cc syringe was irradiated with 2CGE (Cobalt Gray Equivalent) of proton beam in a custom fabricated acrylic phantom. An air-hollow syringe simulates the esophagus.
Results:The Z-stent created the largest dose perturbations ranges from -14.5% to 6.1% due to the steel composition. The WallFlex, Evolution and Ultraflex stents produced the dose perturbation ranges of (-9.2%~8.6%), (-6.8%~5.7%) and (-6.2%~6.2%), respectively. The PolyFlex stent contains the radiopaque tungsten markers located top, middle and bottom portions. When the focal cold spots induced by the markers were excluded in the analysis, the dose perturbation range was changed from (-11.6%~6.4%) to (-0.6%~5.0%).
Conclusion:The magnitude of dose perturbation is related to material of a metallic stent. The non-metallic stent such as PolyFlex shows relatively lower dose perturbation than metallic stents except a radiopaque marker region. Overall Evolution and Ultraflex stent appear to be less dose perturbations. The largest dose perturbations (cold spots) were located at both edges of stents in distal area for the single proton beam irradiation study. The analysis of more than two proton beam which is more typical clinical beam arrangement would be necessary to minimize the doe perturbation effect in proton ratiotherapy.
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