We propose a new method to measure the depth dose distribution in matter. The method is to use organic plastic scintillator as a phantom, which has the effective atomic number close to that of human soft tissue, and to measure the position distribution of the scintillation light by a wavelength analyzer through a thread of plastic optical fiber. The purpose of this study is to examine possibility to measure the depth dose distribution with the proposed method. We carried out the following three measurements. First, we measured the effective field of view (FOV); the plastic optical fiber accepts the light from the FOV. Then, we measured the dose dependence of the amount of emission light. Finally, the light distribution in the depth direction by the present method was compared to the depth dose distribution by the ionization chamber. The results are as follows. The angular range of FOV is 7.03 degrees +/- 0.21 degrees The dose dependence shows a good linearity. In other words, the amount of emission light is proportional to the absorbed dose. Both of the light and the dose distributions are proportional each other, and they show the same attenuation in the region deeper than 15 mm. From these results, we conclude that the present method can be used for the measurement of the depth dose distribution in matter.
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