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Dose distribution of narrow beam irradiation for small lung tumor
Hidetoshi Saitoh1, Tatsuya Fujisaki, Ryoko Sakai
1Department of Radiologic Sciences, Tokyo Metropolitan University of Health Sciences, Tokyo, Japan. saitoh@metro-hs.ac.jp
Purpose:
To aid in the selection of incident X-ray energy for stereotactic irradiation (STI) of lung tumor, dose distribution was investigated in a model of a thorax embedded with a tumor.
Methods And Materials:
The dose distribution in a thorax model was calculated using the EGS4 Monte Carlo simulation; it was also measured with dosimetric film of a tentative thorax phantom. Uniformity of dose distribution in a tumor region was compared among the results of irradiation for several X-ray energies, and optimal X-ray energy for STI of a lung tumor was discussed.
Results:
Dose distributions in the thorax were obtained. An increase in X-ray energy led not only to an increased dose delivered to the tumor, but also to an increased dose to surrounding normal lung tissue.
Conclusions:
The flat range in dose distribution along the beam axis and in the beam profiles of the tumor increases with decreasing X-ray energy. Consequently, lower energy, rather than higher energy, is recommended for STI of a lung tumor in terms of higher uniformity in the target volume.