Investigation of the Constancy of the Dosimetric Parameters of the Proton Therapy System

Abstract

Purpose: Determination of fluctuation ranges of dosimetry parameters of the proton therapy system
 (PTS) to clarify the permissible limit deviations.
 Methods and materials: The basis for the quality assurance program (QA) of the PTS is the report of the
 American Association of Physicists in Medicine AAPM TG-224. According to this report, the QA program is a living, adaptive document that needs to be refined, corrected and optimized taking into account the features of the PTS being in use and the available dosimetry equipment. After setting-up
 checks within the framework of the daily QA program, it became possible to automatically collect data
 containing dosimetry parameters of the PTS for subsequent analysis. It was decided to investigate the
 stability over time of some dosimetry parameters of the PTS in order to determine the ranges of their
 fluctuations and, as a result, to clarify the permissible deviations of these parameters.
 Results: The stability of the parameters associated with the constancy of the proton beam energy selection was studied. As a result, the study showed that the values of the parameters associated with the
 constancy of the proton beam energy selection fluctuated within much smaller limits compared to
 those proposed in TG-224.
 Conclusion: The obtained result may allow us to reconsider the approach to proton therapy planning
 system in the FSBI FSCCRO of the FMBA of Russia, in particular, to the choice of PTV margins. The new
 refined tolerances for the maximum deviations of the analyzed parameters are proposed in this research work