Program Information
Parametric Equation for Quick and Reliable Estimate of Stray Neutron Doses in Proton Therapy and Application for Intracranial Tumor Treatments
A Bonfrate1*, J Farah1 , L De Marzi2 , S Delacroix2 , J Herault3 , R Sayah1 , C Lee4 , W Bolch5 , I Clairand1 , (1) Institut de Radioprotection et de Surete Nucleaire (IRSN), Fontenay-aux-roses, (2) Institut Curie Centre de Protontherapie d Orsay (CPO), Orsay, (3) Centre Antoine Lacassagne (CAL) Cyclotron biomedical, Nice, (4) National Cancer Institute, Rockville, MD, (5) Univ Florida, Gainesville, FL
Presentations
SU-E-T-598 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: Development of a parametric equation suitable for a daily use in routine clinic to provide estimates of stray neutron doses in proton therapy.
Methods: Monte Carlo (MC) calculations using the UF-NCI 1-year-old phantom were exercised to determine the variation of stray neutron doses as a function of irradiation parameters while performing intracranial treatments. This was done by individually changing the proton beam energy, modulation width, collimator aperture and thickness, compensator thickness and the air gap size while their impact on neutron doses were put into a single equation. The variation of neutron doses with distance from the target volume was also included in it. Then, a first step consisted in establishing the fitting coefficients by using 221 learning data which were neutron absorbed doses obtained with MC simulations while a second step consisted in validating the final equation.
Results: The variation of stray neutron doses with irradiation parameters were fitted with linear, polynomial, etc. model while a power-law model was used to fit the variation of stray neutron doses with the distance from the target volume. The parametric equation fitted well MC simulations while establishing fitting coefficients as the discrepancies on the estimate of neutron absorbed doses were within 10%. The discrepancy can reach ~25% for the bladder, the farthest organ from the target volume. Finally, the validation showed results in compliance with MC calculations since the discrepancies were also within 10% for head-and-neck and thoracic organs while they can reach ~25%, again for pelvic organs.
Conclusion: The parametric equation presents promising results and will be validated for other target sites as well as other facilities to go towards a universal method.
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