Background: The quality assurance of 3D treatment planning system (TPS)will be investigated by different
things such as beam configuration, dose calculation and plane evaluation which uses dose volume histogram
analyzes. Material and method: the study was performed by XIO TPS (version 4.3.3) available at South Egypt Cancer
Institute (SECI). This TPS employs two different 3D 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 dosecalculation (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 10×10cm2 and 25×25cm2 for open field. Results: The OAR and PDD are divided into regions each of these having a tolerance limit of the accuracy
acceptable. The large point of deviation appeared in field size 25×25cm2 at energy 15MV in outer regionδ4 of
OAR. This region recorded the largest deviation than the others regions. In PDD curves haven’t any
deviation.Larger deviations were observed with CLK algorithm compared to CON algorithm. 20 points out of
criteria were observed in the RDC of a large field size 25×25cm2, while 16 points were out of criteria in the
field size 10×10cm2. Conclusion: This work presents a feasibility and performance of quality assurance tasks the TPS for external
photon beam