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Multiadaptive Plan (MAP) IMRT to Accommodate Independent Movement of the Prostate and Pelvic Lymph Nodes

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Final rept. 1 May 2008-12 May 2013

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Because of the challenge of the independent movement of the prostaterelativeto the lymph nodes, this research is to develop a novel method using multi-adaptive plan MAP IMRT to accommodate independent movement of the two targeted tumor volumes. In this project, we evaluated two adaptive strategies strategy A creates a set of IMRT plans individually optimizing on a series of possible prostate positions in the planning CT and strategy B creates a set of multi-adaptive plans by dynamically adjusting the radiation apertures to accommodate the daily position of the prostate. Using dual imaging registration method, we found that the bi-directional prostate movement in relative to the pelvic lymph nodes, particular in anterior-posterior and superior-inferior directions, must be considered with strategy A, which increases the number of prepared IMRT plans. Using implanted markers as a surrogate for the location of the prostate gland may mis-interpret the rotation of the gland and a special caution is needed when a large rotation is detected. The prostate rotation can be compensated with translational shifts of the radiation portals. With current clinical planning margins of 8mm6mm posterior to the prostate and 5 mm to the pelvic lymph nodes, the MLC tracking strategy is not necessary. Further reduction in the planning margins to the both targets may require MLC tracking method or real time planning.

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  • Medicine and Medical Research

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