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Microdosimetry at the CATANA 62 MeV proton beam with a sealed miniaturized TEPC

2019; Elsevier BV; Volume: 64; Linguagem: Inglês

10.1016/j.ejmp.2019.06.011

1724-191X

V. Conte, Anna Bianchi, A. Della Selva, Giada Petringa, G.A.P. Cirrone, Alessio Parisi, F. Vanhavere, P. Colautti,

Boron Compounds in Chemistry

A new mini-TEPC with cylindrical sensitive volume of 0.9 mm in diameter and height, and with external diameter of 2.7 mm, has been developed to work without gas flow. With such a mini counter we have measured the physical quality of the 62 MeV therapeutic proton beam of CATANA (Catania, Italy). Measurements were performed at six precise positions along the Spread-Out Bragg Peak (SOBP): 1.4, 19.4, 24.6, 29.0, 29.7 and 30.8 mm, corresponding to positions of clinical relevance (entrance, proximal, central, and distal-edge of the SOBP) or of high lineal energy transfer (LET) increment (distal-dose drop off). Without refilling the microdosimeter with new gas, the measurements were repeated at the same positions 4 months later, in order to study the stability of the response in sealed-mode operation. From the microdosimetric spectra the frequency-mean lineal energy y - F and the dose-mean lineal energy y - D were derived and compared with average LET values calculated by means of Geant4 simulations. The comparison points out, in particular, a good agreement between microdosimetric y - D and the total dose-average L E T ¯ d , which is the average LET of the mixed radiation field, including the contribution by nuclear reactions.