P Colautti1, V Conte2, A Selva2, S Chiriotti3, A Pola4, D Bortot4, A Fazzi4, S Agosteo4, M Treccani4, L De Nardo5, C Verona6, G Verona Rinati6, G Magrin7, G A P Cirrone8, F Romano9. 1. INFN Laboratori Nazionali di Legnaro, viale dell'Università 2, 35020 Legnaro, Italy. Electronic address: paolo.colautti@lnl.infn.it. 2. INFN Laboratori Nazionali di Legnaro, viale dell'Università 2, 35020 Legnaro, Italy. 3. Belgian Nuclear Research Centre, SCK·CEN, Boeretang 200, 2400 Mol, Belgium. 4. Politecnico di Milano, Dipartimento di Energia, via La Masa 34, 20156 Milano, Italy; INFN, Sezione di Milano, via Celoria 16, 20133 Milano, Italy. 5. INFN, Sezione di Padova, via Marzolo 8, 35131 Padova, Italy; University of Padova, Physics and Astronomy Department, via Marzolo 8, 35131 Padova, Italy. 6. INFN, Sezione di Roma Tor Vergata, via della Ricerca Scientifica, 1, 00133 Roma, Italy; University of Roma Tor Vergata, via del Politecnico 1, Roma 00133, Italy. 7. EBG MedAustron, Marie Curie-St. 5, 2700 Wiener Neustadt, Austria. 8. INFN Laboratori Nazionali del Sud, via S.Sofia 62, 95123 Catania, Italy; ELI-Beamlines, Za Radnici 835, Dolní Břežany 252 41, Czech Republic. 9. INFN Laboratori Nazionali del Sud, via S.Sofia 62, 95123 Catania, Italy; ELI-National Physical Laboratory, CMES - Medical Radiation Science, Teddington, UK.
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 12C 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 withLET¯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.
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 12C 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 withLET¯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.