The Impact of Number of Beams in IMRT of Cancer Prostate
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Abstract
Purpose: The aim of this study is to judge the effect of number of IMRT beams in cancer prostate on different physical and biological evaluation indices and treatment plan quality.
Material and Methods: Seven IMRT plans with different number of beams ranging between five and eleven have been evaluated physically and biologically. Physical evaluation, have been performed by calculating dose homogeneity indices (MHI and HI), target coverage and conformity indices (PITV, TCI, CI, and CN), dose gradient (GI and GM) and an index for overall plan quality factor (QF). Biological evaluation has been performed by calculating TCP, NTCP, and P+.
Results: In IMRT plans with number of beams more than seven, all the physical and biological indices don't vary with the number of beams. In plans with number of beams less than or equal to seven only the values of TCI, PITV, GI, GM and QF are affected by changing the number of beams.
Conclusion: In IMRT, changing the number of beams will affect PITV, TCI, GI, GM, and QF indices and the number of Mus. In IMRT of prostate cancer the optimal number of beams is seven which has a high QF and low number of Mus.