Miniaturized microdosimeters as LET monitors: First comparison of calculated and experimental data performed at the 62 MeV/u C-12 beam of INFN-LNS with four different detectors

作者：Colautti P^*; Conte V; Seiva A; Chiriotti S; Pola A; Bortot D; Fazzi A; Agosteo S; Treccani M; De Nardo L; Verona C; Rinati G Verona; Magrin G; Cirrone G A P^*; Romano F

来源：Physica Medica, 2018, 52: 113-121.

DOI：10.1016/j.ejmp.2018.07.004

Purpose: The aim of this paper is to investigate the limits of LET monitoring of therapeutic carbon ion beams with miniaturized microdosimetric detectors.
Methods: Four different miniaturized microdosimeters have been used at the 62 MeV/u C-12 beam of INFN Southern National Laboratory (LNS) of Catania for this purpose,i.e. a mini-TEPC and a GEM-microdosimeter, both filled with propane gas, and a silicon and a diamond microdosimeter. The y(D) (dose-mean lineal energy) values, measured at different depths in a PMMA phantom, have been compared with L (E) over barT(D) (dose-mean LET) values in water, calculated at the same water-equivalent depth with a Monte Carlo simulation setup based on the GEANT4 toolkit.
Results: In these first measurements, no detector was found to be significantly better than the others as a LET monitor. The (y) over bar (D) relative standard deviation has been assessed to be 13% for all the detectors. On average, the ratio between (y) over bar (D) and L (E) over barT(D) values is 0.9 +/- 0.3, spanning from 0.73 +/- 0.08 (in the proximal edge and Bragg peak region) to 1.1 +/- 0.3 at the distal edge.
Conclusions: All the four microdosimeters are able to monitor the dose-mean LET with the 11% precision up to the distal edge. In the distal edge region, the ratio of (y) over bar (D) to L (E) over barT(D) changes. Such variability is possibly due to a dependence of the detector response on depth, since the particle mean-path length inside the detectors can vary, especially in the distal edge region.

• 出版日期2018-8