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영어

The paper is in continuation of the previous work in which the effect on Bragg peak position, range and penumbra width of proton beam in radiation therapy is observed when inhomogenities such as brain, kidney and thyroid are placed in a homogeneous medium. The human organs along with the positioning of the tumour region were designed and the suitable energy range for each tumour of the human organ was optimized. A significant shift in the Bragg peak position was observed in each case i.e., approx. -0.36% for muscular skeleton, -0.44% for soft tissue (S. Bhatnagar et.al, 2014) [1]. In this paper, we will discuss the significant effect of the absorbed dose of proton beam during treatment in different ages. Distinct phantom volumes with their respective organs i.e. brain, kidney and thyroid of children at various ages such as 0, 1, 5, 10, 15 years and also an adult are considered from OAK RIDGE NATIONAL LABORATORY (ORNL) report (M. Cristy et.al) [2] for present simulation study. The relation between dose equivalent, absorbed dose as function of depth to target volume is computed. We observed that the dose deposition is dependent on the age where patient at younger age receives dose at higher rate while it gradually decreases in the other cases i.e. 10 year, 15 year and adult. The step length of the particle is varied which imposes a limit during particle interaction in the medium per unit length. The obtained dose rate on varying the step length is compared among the Geant4 9.3 and 9.4 versions to observe its data accuracy.