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Direct absorbed dose to water determination based on water calorimetry in scanning proton beam delivery
Author(s) -
Sarfehnia A.,
Clasie B.,
Chung E.,
Lu H. M.,
Flanz J.,
Cascio E.,
Engelsman M.,
Paganetti H.,
Seuntjens J.
Publication year - 2010
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3427317
Subject(s) - absorbed dose , calorimeter (particle physics) , calorimetry , dosimetry , materials science , proton , dose profile , proton therapy , nuclear medicine , dosimeter , beam (structure) , radiochemistry , nuclear physics , physics , optics , chemistry , medicine , detector , thermodynamics
Purpose The aim of this manuscript is to describe the direct measurement of absolute absorbed dose to water in a scanned proton radiotherapy beam using a water calorimeter primary standard. Methods The McGill water calorimeter, which has been validated in photon and electron beams as well as in HDRI192 r brachytherapy, was used to measure the absorbed dose to water in double scattering and scanning proton irradiations. The measurements were made at the Massachusetts General Hospital proton radiotherapy facility. The correction factors in water calorimetry were numerically calculated and various parameters affecting their magnitude and uncertainty were studied. The absorbed dose to water was compared to that obtained using an Exradin T1 Chamber based on the IAEA TRS‐398 protocol. Results The overall 1‐sigma uncertainty on absorbed dose to water amounts to 0.4% and 0.6% in scattered and scanned proton water calorimetry, respectively. This compares to an overall uncertainty of 1.9% for currently accepted IAEA TRS‐398 reference absorbed dose measurement protocol. The absorbed dose from water calorimetry agrees with the results from TRS‐398 well to within 1‐sigma uncertainty. Conclusions This work demonstrates that a primary absorbed dose standard based on water calorimetry is feasible in scattered and scanned proton beams.