title: Dosimetric accuracy assessment of a treatment plan verification system for scanned proton beam radiotherapy: one-year experimental results and Monte Carlo analysis of the involved uncertainties.
abstract: During one year of clinical activity at the Italian National Center for Oncological Hadron Therapy 31 patients were treated with actively scanned proton beams. Results of patient-specific quality assurance procedures are presented here which assess the accuracy of a three-dimensional dose verification technique with the simultaneous use of multiple small-volume ionization chambers. To investigate critical cases of major deviations between treatment planning system (TPS) calculated and measured data points, a Monte Carlo (MC) simulation tool was implemented for plan verification in water. Starting from MC results, the impact of dose calculation, dose delivery and measurement set-up uncertainties on plan verification results was analyzed. All resulting patient-specific quality checks were within the acceptance threshold, which was set at 5% for both mean deviation between measured and calculated doses and standard deviation. The mean deviation between TPS dose calculation and measurement was less than ±3% in 86% of the cases. When all three sources of uncertainty were accounted for, simulated data sets showed a high level of agreement, with mean and maximum absolute deviation lower than 2.5% and 5%, respectively.
authors.affiliation: Medical Physics Unit, Centro Nazionale Adroterapia Oncologica (CNAO), I-27100 Pavia, Italy. molinelli@cnao.it
authors.forename: S
authors.initials: S
authors.lastname: Molinelli
authors.forename: A
authors.initials: A
authors.lastname: Mairani
authors.forename: A
authors.initials: A
authors.lastname: Mirandola
authors.forename: G
authors.initials: G
authors.lastname: Vilches Freixas
authors.forename: T
authors.initials: T
authors.lastname: Tessonnier
authors.forename: S
authors.initials: S
authors.lastname: Giordanengo
authors.forename: K
authors.initials: K
authors.lastname: Parodi
authors.forename: M
authors.initials: M
authors.lastname: Ciocca
authors.forename: R
authors.initials: R
authors.lastname: Orecchia
mesh_terms: D006801:Humans; D009010:Monte Carlo Method; D057285:Precision Medicine; D061766:Proton Therapy / Q000379:methods* / Q000592:standards; D011786:Quality Control; D011874:Radiometry; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods* / Q000592:standards; D035501:Uncertainty