Peripheral Organ Dose Evaluation using a Human Body Phantom in Intensity Modulated Radiation Therapy for Lung Cancer with Helical Type Accelerator

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Purpose: Intensity modulated radiation therapy (IMRT) is characterized by a relatively long period for beam exposure and consequently the risk for unnecessary exposure to non-targeted organs, mainly due to the scattered radiation, should be considered. The puposes of this study are to measure the absorbed dose of the peripheral organs during helical IMRT using a fluorescent glass dosimeter. Materials and Methods: In this research, we took lung cancer as a model and measured the absorbed dose of the peripheral organs during helical IMRT using a fluorescent glass dosimeter. The planning target volume (PTV) dose of 95% was set to be 5 Gy in the phantom. Results and Discussion: The highest exposure dose was observed for the breasts, which were on the PTV trajectory, with the left and right breasts receiving doses of 227.94 mGy and 371.90 mGy, respectively. The exposure doses of the left and right lenses were 3.13 mGy for the left lens and 3.22 mGy for the right lens. An exponential dose reduction to the distance from PTV was confirmed. Our data suggest that the doses for peripheral organs were acceptable in lung cancer case based on past literature search. However, the use of custom blocks for the eyes should be considered to prevent possible late occurance of cataract.