Speaker
Description
INTRODUCTION
To monitor range uncertainties in proton therapy, dose reconstruction is desirable,
and it has already been proposed in the literature starting from detected secondary radiation, mostly positron emitters (PE). Prompt-gammas (PG) can be alternatively used:
emitted within nanoseconds after nuclear interactions, they can be exploited for realtime adaptation.
MATERIAL AND METHODS
The purpose of this work is to assess the feasibility of three existing approaches for
dose reconstruction from PG: the analytical deconvolution method [1], the evolutionary
algorithm [2][3][4], and the maximum-likelihood expectation-maximization (MLEM)
algorithm [5][6]. These were chosen because of the inherent application of the filtering,
introduced first by Parodi and Bortfeld [7] for PET data, then extended to PG radiation
by Schumann et al. [2] and by Pinto et al. [8]. Mono- and polyenergetic proton beams irradiation of homogeneous and inhomogeneous phantoms were simulated (using Geant4
[9], v.10.07.p03). 1D laterally integrated depth-dose and depth-PG distributions were
considered.
RESULTS
The accuracy of the reconstructed depth-dose profiles was evaluated via comparison
with their corresponding ground truth using different metrics, which show an overall
match. Regardless of the method, ∆R80, ∆R50 and ∆R10 metrics (see table 1 caption)
were found to be below 1 mm. For the tests performed, the methods are sensitive to
properly reconstruct dose when range shifts of different magnitudes are introduced.
CONCLUSIONS
This work verifies the applicability of the investigated dose reconstruction techniques to PG distributions. Extension to 3D distributions is currently in progress, and
the application to measured data is foreseen in the near future. The final purpose consists
of the comparison of the evaluated strategies as part of their applicability to real-time
adaptive particle therapy
