الفهرس 
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Abstract
Quality assurance of 3D treatment planning system (TPS) was investigated by different methods such as beam configuration, dose calculation and plane evaluation, which uses dose volume histogram analyses. This study was performed using computer soft were model XIO TPS (version 4.3.3) available at South Egypt Cancer Institute (SECI). This TPS employs two different 3D calculation algorithms Clarkson (CLK) and Fast Fourier Transform Convolution (CON). Relative dose calculation (RDC), in terms of percentage depth dose (PDD) and off-axis beam profiles (OAR), and absolute dose calculation (ADC), in terms of dose and output factor, were used and compared with the measured one using ionization chambers with water or solid phantoms in medical linear accelerator (linac), (Siemens Mevatron MD2). Two photon energies, 6MV and 15MV, were studied using field sizes of (10×10) cm 2 and (25×25) cm 2 for open and wedged fields using wedges (15°, 30°, and 45° ). In (W60°) used a maximum field size in this wedge (20×25) cm2 . The OAR and PDD were divided into regions. Each region has a tolerance limit of the accuracy acceptable. The larger point of deviation appeared in wedged field size 25×25 cm 2 at energy 6MV in outer region (δ4) of OAR. This region recorded the largest deviation of all other regions. Also, (W60°) recorded a larger deviation larger than the open and other wedges which contained about 64 points of deviations at OAR profile curves. In PDD curves, no deviation was recorded. Larger deviations were observed in CLK algorithm compared to CON algorithm. At a big field size of (25×25) cm 2 in the RDC, 97 points out of criteria were observed, and in field size (10×10) cm 2 as well, 71 points were out of criteria.