الفهرس 
Study of comparative dosimetry using inverse treatment planning system versus forward treatment planning system in intensity modulated radiotherapy
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Abstract
The ideal radiotherapy treatment is to deliver the maximum dose to the tumor and minimum dose elsewhere at the same time. Two treatment planning techniques are applied; the first is an extension of three dimensional conformal therapy (3DCRT) defined as forward plan. It{u2019}s a simplified form of Intensity Modulated Radiation Therapy (F-IMRT) and the planner tries a variety of configurations of simple beams, wedge fields and more than one segment are used in each beam direction. The other technique called inverse Intensity Modulated Radiation Therapy (I-IMRT). It is a fixed delivery technique that contains a set of intensity modulated beams that enter the patient from multiple directions. The calculation method for inverse plan starts with the desired result and then works backward to generate an optimum distribution to reach the required dose. In the present study a comparison is done between F-IMRT and I-IMRT techniques regarding the physical dose volume histogram (DVH) and dosimetric parameters. Thirty localized prostate cancer patients are chosen. The CT scanned data of those patients are transferred to the Xio treatment planning system. F-IMRT and I- IMRT treatment plan are designed for deliver on an ELEKTA precise linear accelerator with multi-leaf collimators (MLCs 40 leafs). The treatment plan dose analysis is based on isodose distributions, Dose Volume Histograms (DVHs) and several physical indices as mean dose (D mean max 95% ), maximum dose (D ), 95% dose (D ), integral dose (ID), volume of tumor receiving 10 and 20 Gy (IrV10 and IrV20), total number of segments and monitor units (MUs). Homogeneity index, Conformity index and Conformation number are other evaluation parameters that considered in this study