en Radiation Biology Radiation Biology تحقيق بديع Original Research <p><strong>Background:</strong> The present work aims to study the out-of-field photon calculation accuracy of a commercial treatment planning system (TPS), Oncentra, for three-dimensional conformal radiotherapy (3D-CRT) and intensity modulated radiation therapy (IMRT) treatment techniques from Elekta Synergy medical linear accelerator. <strong>Materials and Methods:</strong> Accuracy of individual out-of-field dose components was studied by defining a square field of 10 x 10 cm² in our TPS and it is verified by using ionization chamber and TLDs (Thermoluminescent dosimeter) at 5 cm depth. Using 3D-CRT and IMRT techniques Ca (carcinoma) prostate treatment plans were created using 6 MV photon beam and calculated in Oncentra Masterplan v4.3 planning systems for out-of-field and further compared the same with TLD measurements. <strong>Results:</strong> Individual components study shows the poor out-of-field calculations in TPS, with respect to that obtained from TLD measurements. Underestimation increases from 10 % to 80 % as a contribution from various components while moving far from field edge. Complex IMRT plans resemble this underestimation of TPS calculations in greater extend. <strong>Conclusion:</strong> This study quantifies the poor accuracy for out-of-field dose calculations in TPS. No significant difference in 3D-CRT and IMRT plans is found at near field edge. While, as distance from field edge increases, underestimation of TPS in IMRT plan is higher. 10 % &ndash; 60 % difference in out-of-field dose was found as distance move from 2 cm to 7.5 cm far from field edge between TPS estimations and the measurements.</p> TPS, TLD, out-of-field dose, 3D-CRT, IMRT 127 134 http://ijrr.com/browse.php?a_code=A-10-1-550&slc_lang=en&sid=1 T. Siji Cyriac sijicyriacsanju@gmail.com 790031947532846009743 790031947532846009743 Yes Department of Physics, Noorul Islam Centre for Higher Education, Kumaracoil, Thuckalay, Kanyakumari District, 629 180, Tamilnadu, India M.M. Musthafa 790031947532846009744 790031947532846009744 No Department of Physics, University of Calicut, Thenhipalam, Malappuram, 673 635, Kerala, India R. Ganapathi Raman 790031947532846009745 790031947532846009745 No Department of Physics, Noorul Islam Centre for Higher Education, Kumaracoil, Thuckalay, Kanyakumari District, 629 180, Tamilnadu, India K. Abdul Haneefa 790031947532846009746 790031947532846009746 No INFN and Department of Physics, University of Torino, Via P. Giuria, 10125, Torino, Italy Saju Bhasi 790031947532846009747 790031947532846009747 No Department of Radiation Physics, Regional Cancer Center, Trivandrum, 695 011 , Kerala, India