Miniaturized microdosimeters as LET monitors: First comparison of calculated and experimental data performed at the 62 MeV/u 12C beam of INFN-LNS with four different detectors. (August 2018)

• Record Type: Journal Article
• Authors: Colautti, P.; Conte, V.; Selva, 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.
• Is Part Of: Physica medica. Volume 52(2018)
• Page Start: 113
• Page End: 121
• Publication Date: 2018-08
• Subjects: Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2018.07.004
• Languages: English
• ISSNs: 1120-1797

Abstract

Highlights: Miniaturized microdosimeters can monitor the dose-mean LET of carbon-ion beams. Four miniaturized microdosimeters have measured on the same beam and same phantom. The y - D values have been compared with Monte Carlo-calculated dose-mean LET values. The four detectors monitor the dose-mean LET with 11% precision up to the distal edge. In the distal edge the monitor precision worsens. Abstract: 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 12 C 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 LET ¯ 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 - D relative standard deviation has been assessed to be 13% for all the detectors. On average, the ratio between y - D and LET ¯ 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 - D to LET ¯ 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.