Impact of Esophageal and Biliary Stents On Proton Dose Calculation
S Mossahebi1*, P Sabouri2, G Kim1, J Polf1, J Molitoris1, B Greenwald1, P Darwin1, S Chen1, (1) University of Maryland Medical School, Baltimore, MD, (2) Miami Cancer Institute, Miami, FL
Presentations
PO-GePV-T-136 (Sunday, 7/25/2021) [Eastern Time (GMT-4)]
Purpose: Hepatobiliary and esophageal malignancy patients who are commonly implanted with stents are often treated with radiotherapy. To date, the impact of the newer stents on proton calculated dose is unknown. This study aims to analyze and compare the radiation dosimetric impact of newer esophageal and biliary stents to determine if dose adjustments in areas with stent presence are needed.
Methods: Five esophageal and seven biliary stents were secured inside a water phantom and CT scans were acquired. The water equivalent thickness (WET) values of each sample were obtained using a multilayer ionization chamber and 2D-planar dose measurements of a proton field were performed using an ion chamber array. Dosimetric impact and WET of stents on treatment planning system (TPS) calculated dose was compared with measurements.
Results: WET values for all esophageal stents were less than 1mm (0.35 - 0.85 mm) and values for all biliary stents were less than 0.5mm (0.15 - 0.45 mm). For planar dose measurements in water, no difference (<1%) was observed for both esophageal and biliary stents, thereby implying that the perturbation effect of the stents was within the measurement uncertainty and not detectable. For biliary stents TPS indicated changes in WET values as large as 2 mm. This inconsistency between measured and TPS calculated WET values are due to CT artifacts and inaccuracy of SPR estimation.
Conclusion: Our study’s results show that the presence of biliary and esophageal stents has minimal impact on proton dose. However, inaccuracies associated with SPR estimation suggest that these devices can perturb calculated dose.
ePosters
Keywords
Radiation Therapy, Protons, Stents
Taxonomy
TH- External Beam- Particle/high LET therapy: Proton therapy – experimental dosimetry
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