Presentation Observation of Therapeutic Proton Beam Flux by Radio-activation Transfer Imaging using an Anthropomorphic Phantom

小原, 哲  ,  神澤, 聡  ,  森, 祐太郎  ,  照沼, 利之  ,  磯辺, 智範  ,  赤羽, 恵一  ,  島田, 義也  ,  榮, 武二

Purpose:The present work is intended to pilot the possible use of radio-activation of phantom compositions for verification of the calculated planning patient dose and delivery spatial accuracy. And the radio-activity of phantom material shows incident and scattering particle energy mapping within the tissue equivalent anthropomorphic phantoms. The activity transfer imaging is the real projectile roots which runs throughout the phantoms, that useful to estimate range uncertainties therapeutic proton beam.Experimental procedures:Measurements were performed inside a water equivalent phantom 15cm^3 (Tough Water; Kyoto Kagaku) and anthropomorphic phantom (5yr child phantom, 705-C, CIRS-ATOM), which are sliced in 2.5cm thickness. The target volumes were designed for verification the simple status of 50mm*50mm^2, 155MeV mono-peak proton beam into the water equivalent phantom and 60mm SOBP into anthropomorphic phantom. This measurement shows only axial views of proton projectile profiles on cross sections of the phantom slices setting on the IP (imaging plates; BAS-MS) after the irradiations. The images from the IPs are the total signals of the beta-plus activity which decay 3, 7 and 30 minutes later from proton beam irradiation. This study reports how to get special high-resolution (especially penumbra) mapping of projectiles distribution on the phantom surface.Summary :It is seen that the results of the relative activation profiles from both Monte Carlo simulations and measurements agree well for the mono peak proton beams. The analyzing of the activation imaging, the PDD (percentage depth dose) of the region vicinity of the center of proton beam is good agreement with MC calculation which converted to treatment planning. In contrast, OCR (off-central-axis ratio) it have been seen mismatching a few percent, especially around the area of penumbra. Conclusions:It needs to evaluate the amount of penetrating particles incoming along the gaps of the phantom slices. However it is important to mention here that this experimental imaging method has capability to observe therapeutic beam contamination experimentally which is low energy protons and scattering secondary neutrons mixture that should taking into account to estimate the LET differences in penumbra region.
15th International Congress of Radiation Research

Number of accesses :  

Other information