Contouring, planning and dose calculation in treatment planning systems (TPS) are based on computedtomography (CT) images. Therefore, it is important to have developed, optimized and adapted scanning protocolsfor specific anatomic regions and special radiotherapy modalities such as stereotactic radiosurgery (SRS). The aimof this study was to determine influence of tube voltage, field of view size (FOV) and reconstruction kernels on CTnumbers and the resulting radiotherapy (RT) dose calculation.This study was performed at Clinic of Oncology, Clinical Center University of Sarajevo. Verification electrondensity and CT number values was performed using CIRS Thorax 002LFC phantom, while anthropomorphic CIRS038 phantom for stereotactic end-to-end verification was used for the purpose of dose plan calculation analysis withlarge bore CT simulator Canon Aquillion LB.The significant correlation between the tube voltage and the measuredvalues of CT numbers is significant for all materials (p < 0.05), except for water (p = 0.310). No significantcorrelation between FOV and obtained values of CT numbers was found in any of the evaluated tissue equivalentmaterials. Evaluating the impact of reconstruction kernels on Hounsfield units (HU), significant deviations werefound for the FC62, FC68 and FC07 reconstruction kernels. Also, analyzing the influence of reconstruction kernelson the RT dose calculation, the extreme values are associated with Dmin/D in PTV for kernels FC41 and FC68, wheredeviations from the values obtained using the baseline scanning parameters were -1.3% and -1.9%. For deviation of1 HU in muscle tissue of CIRS 002LFC, the calculated Dmin/D in PTV of CIRS STEEV phantom will reduce by0.79%. Similarly, the reduction of D₉₈ and D₂ would be 6.8 cGy and 3.03 cGy for 1 HU, respectively. Change of thereconstruction kernels caused differences of 0.4% in Dmin/D calculation in clinical target volume (CTV).CT scanning and reconstruction parameters may affect Hounsfield units, which could have an impact on dosecalculations in RT plan. Hence, it is recommended to standardize the scanning protocol used in calibration curvegeneration for TPS. One should avoid use of different tube voltages and kernels, while according to this study, thechange of FOV will have no impact on dose calculations

Background: Radiotherapy is one of the earliest fields in Medicine in which computers have made an inroad. The main uses of computers, which include treatment planning, dose calculations, localization of tumors, verification of patient setups and radiation beam data acquisition, are highlighted in this paper. It is believed that a modern Radiotherapy department cannot function optimally without some form of computing facilities. Aim: To discus the use of computers in the radiotherapy department of Institute of Oncology in Sarajevo Bosnia and Herzegovina Methods and Materials: In 1999, a first and in the 2005 the second linear accelerator were installed in our department for external radiotherapy, supported with CMS and Precise Plan planning systems. In the department for Brachytherapy we installed GamaMed plus High Dose Brachytherapy machine with Ir 192 radioactive sources, and ABACUS planning system. The patients were treated with 1D, 2D and 3D planning systems. Results: There were around 2300 patients treated in our department for external radiotherapy and 250 patients yearly treated in our department for brachytherapy. Of these 1500 with 1D were irradiated, 500 with 2D and 250 with 3D planning treatments, with constant tendency of increase in 3D planning for about 20% yearly. Conclusion: New equipment supported with new sophisticate planning systems enabled us to treat more patients in the more accurate way in less time. We are now approaching European standards in this field of medicine.