Evaluation of Accuracy and Quality assurance of external beam therapy with photons

Introduction: Receiving exact dose by the patients is vital in radiotherapy. In radiation therapy, the dosimetry of radiations is too important because of successful radiation inquires for delivering the exact dose to the target volume. This study is to evaluate the tolerances and the accuracy of calculated dose of photon beams in the treatment software system. The TECDOC1583 protocol is used to achieve this goal.   Materials and Methods: In this work, the Treatment Planning System TiGRT to distribute dose of photon beams was used and the measurements results in inhomogeneity phantom are compared in 4 levels. Results: According to the TECDOC1583 protocl, the results are accepted but at third and fifth levels the error percent of lung and soft tissue were found to be 4.3%with a 0.3% difference and to be 5/7 with a 3% difference. Conclusion: Because of the low density of electrons in the lung tissues, there were more errors in the planning system hence, the treatment planning needs more accuracy and the data should be reevaluated. Restarting the device and checking the dose values are recommended for applying the algorithms to get more successful treatment. We must be to solve the mistakes because it will effect so undesirable on the treatment.