Microdosimetric evaluation of secondary fragments in Phantom produced by therapeutic 290MeV/nucleon carbon beam at HIMAC

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Abstract

Microdosimetric single event spectra as a function of depth in phantom for the therapeutic carbon beam from HIMAC have been measured by two ways: one is a fragment particle identification measurement (PID-mode) using a tissue equivalent proportional counter (TEPC) coupled with scintillation counter system and the other is an in-phantom measurement (IPM-mode) which a TEPC is actually positioned in phantom.For the PID-mode, fragments produced by carbon beam in phantom are identified by ΔE-TOF distribution between two scintillation counters. Lineal energy distribution for carbon and five fragments of proton, helium, lithium, beryllium and boron ions are obtained in the lineal-energy range of 0.1-1000keV/mm at eight depths (6.9-146.9mm).For the IPM-mode, the total lineal energy distributions at eight depths (59.9-295.9 mm) are measured and compared with the result of PID-mode measurement. Both spectra are consistent with each other. It shows that the PID-mode measurement can be discussed as in phantom measurement. The dose distribution of the carbon beam and fragments are obtained separately. The depth dose curve has consistent with the Bragg peak. And also, it can clearly be seen that the fragment-dose contributions dominated at the deeper position of the Bragg peak.Relative biological effectiveness for the carbon beam in the phantom has been calculated using a response function. RBE of the carbon beam is maximized at the Bragg peak. The maximum value of RBE is about 4.5 and then rapidly decreases at the deeper position of the peak.

Journal

  • The Japan Radiation Research Society Annual Meeting Abstracts

    The Japan Radiation Research Society Annual Meeting Abstracts 2005(0), 365-365, 2005

    Journal of Radiation Research Editorial Committee

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