Spectra of linear energy transfer and other dosimetry characteristics as measured in C290 MeV/n MONO and SOBP ion beams at HIMAC-BIO (NIRS, Japan) with different detectors

Microdosimetry for a carbon ion beam using track-etched detectors

Track-etched detectors (TED) have been used as linear energy transfer (LET) spectrometers in heavy ion beams for many years. LET spectra and depth-dose distribution of a carbon ion beam were measured behind polymethylmethacrylate degraders at Heavy Ion Medical Accelerator in Chiba, Japan. The measurements were performed along monoenergetic beam with energy 290 MeV u(-1) in different positions: (1) at beam extraction area, (2) at beginning, (3) maximum and (4) behind the Bragg peak region (0, 117, 147 and 151 mm of water-equivalent depth, respectively). The LET spectra inside and outside of the primary ion beam have been evaluated. TED record only heavy charged particles with LET above 8-10 keV µm(-1), while electrons and ions with lower LET are not detected. The Geant4 simulation toolkit version 4.9.6.P01 has been used to estimate the contribution of non-detected particles to absorbed dose. Presented results demonstrate the applicability of TED for microdosimetry measurements in therapeutic carbon ion beams.

Spectrometry of linear energy transfer with track-etched detectors in carbon ion beams, MONO and SOBP

Five various materials employed as track-etched detectors (TEDs) were exposed in beams of carbon ions with energy 290 MeV. u(-1) in the HIMAC-BIO facility in Japan. The exposures were performed behind various types of polymethyl methacrylate shielding. The beam had two possible set-ups--monoenergetic set-up and modulated spread-out Bragg peak set-up. All used TEDs are polyallyl diglycol carbonates (PADCs): Page from Mouldings (Pershore) Ltd, Tastrak from Track Analysis Systems Ltd, both from the UK; USF4 from American Technical Plastics from the USA and two products of Japan Fukuvi Chemical Industry Co., Ltd--TD1 and Baryotrak. Spectra of linear energy transfer and depth-dose distributions were obtained. Besides, differences among PADCs are discussed.