[P182] Dosimetric study of radioactive esophageal stents for the treatment of advanced esophageal cancer

Autor: Akbar Beiki-Ardakani, Shahab Sheibani, Hossein Poorbaygi, Daryiush Rezaey Uchbelagh, Mojtaba Arjmand, Payman Rafiepour
Rok vydání: 2018
Předmět:
Zdroj: Physica Medica. 52:153
ISSN: 1120-1797
DOI: 10.1016/j.ejmp.2018.06.482
Popis: Purpose Perform a comprehensive dosimetric investigation of photon- and beta-emitting esophageal stents for the treatment of advanced esophageal cancer. Methods Using Geant4 toolkit, esophageal stents carrying 125I, 103Pd and 131Cs brachytherapy seeds as well as esophageal stents coated with 166Ho and 188Re radioisotopes were simulated and their dose distributions were investigated. The effects of stent material, the presence of a magnetic field and the arrangement of the seeds on dose distributions were investigated. For validation, radiochromic EBT3 film dosimetry was performed for 125I seed-loaded and 166Ho impregnated esophageal stents. Furthermore, the accumulated dose of each radioactive stent (at the dose reference points), was calculated for different activities. Results Peak to valley dose (PVD) ratio is defined as a measure of dose uniformity for esophageal stents loaded with brachytherapy seeds to show the difference of dose intensity between the location of the presence of a radioactive seed and the adjacent vacant place. Due to the short penetration depth of beta particles in tissue, only palliative treatment is expected for beta-emitting esophageal stents. 103Pd and 131Cs seed-loaded stents cannot deliver the sufficient dose at the reference point, due to their short half-lives. It is shown that the edge restenosis in beta-emitting esophageal stents is more probable than in photon-emitters due to their rapid dose falloff on the stent edges. The presence of a magnetic field (>1.5 Tesla) along the stent axis, has a significant effect on dose distributions of beta-emitting stents. Conclusions The interval distance between two adjacent seeds (center to center) should not exceed 15 mm, due to the presence of cold spots in the spaces between seeds that are the locations of the tumor recurrence and it is more critical for 103Pd seeds. Since the radioactive esophageal stents are permanent implants, 125I with 28.4 keV mean energy and 59.4 days half-life is the best choice among the low energy brachytherapy seeds.
Databáze: OpenAIRE
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