【摘 要】
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The purpose of this study is to investigate and to evaluate the effects of target motion resulting from respiration on its dosimetric parameters such as absolute dose, intensity profiles, and dose dis
【机 构】
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Department of Radiologic Sciences Thomas Jefferson University Philadelphia, PA USA
【出 处】
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BIT‘s2nd Annual World Cancer Congess-2009 (2009第二届癌症大会)
论文部分内容阅读
The purpose of this study is to investigate and to evaluate the effects of target motion resulting from respiration on its dosimetric parameters such as absolute dose, intensity profiles, and dose distributions delivered by respiratory-gated intensity modulated radiation therapy (IMRT).A moving phantom was designed and built to simulate the cycle of normal breathing motion.A commercial respiratory gating system was used to automatically control the beam on and off based on the motion of an external marker placed on the phantom.For the gated beam delivery, the gated window was determined by examining the 4D-CT images of the moving phantom.Different widths of the gated windows representing different length in time scale were selected so that the motion of the phantom during the beam-on period within the window would range from 1 to 3cm.We delivered IMRT fields to expose ready-pack radiographic films placed in three various conditions: a stationary phantom, a moving phantom with the gated controlling beam and a moving phantom without the gated controlling beam.The IMRT dose distributions obtained from the stationary phantom would serve as a reference for comparison with other two cases with moving phantom.Our results showed significant dose variations in dose distributions between the cases of stationary phantom and the moving phantom without gating.However, the absolute doses and dose profiles delivered with IMRT fields to a moving target of 1cm maximum displacement had shown no significant differences from those of a stationary target.With the gating system of beam delivery, the results have shown that significant reduction of the level of variations and deviations in dose distribution and absolute dose measurement in spite of the target motion.
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