Browsing by Author "Nart, M."

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The Comparison of Dose Distribution of Different 3d Conformal and Conventional Radiotherapy Plans for Gastric Cancer
(Ijrr-iranian Journal Radiation Res, 2016) Izmirli, M.; Yilmazer, G.; Cakir, T.; Palabiyik, Z. A.; Nart, M.
Aims: It was aimed to investigate postoperative conformal radiotherapy planning that provides the best target volume and the least dose for critical organs in cancers of stomach. Methods: This study was conducted on the CT simulation images of thirty patients diagnosed with gastric cancer. Target volumes and the organs at risk were contoured. AP-PA reciprocal parallel field conventional plan and three- and four-field 3D conformal plans were created using linear accelerator. Target volumes and doses consumed by organs at risk were compared by dose-volume histograms. Results: While a sufficient dose could be applied to target volumes in all plans with conformal planning, average figures showed that 95% of porta hepatis area failed to take the prescribed dose (D95) in some plans by using AP-PA reciprocal parallel zone conventional plans. The most convenient protection for spinal cord, heart and kidneys was obtained by conformal four-field technique and the liver doses were increased in conformal four-field plans but did not exceed the tolerance dose. And also, in the conventional AP-PA reciprocal parallel field plans, tolerance dose of spinal cord (4500 cGy) was exceeded. Conclusion: In this study, conformal four-field technique was superior considering target volume dose distributions, and especially spinal cord doses in all localizations and heart doses in cardia tumors. Kidney doses were also reduced in conformal four-field planning, but failed to reach statistical significance. There was a not exceeding tolerance limits dose increase in liver.
Impact of Contrast Agents on Dose Algorithms of Planning Systems
(Ijrr-iranian Journal Radiation Res, 2016) Izmirli, M.; Cakir, T.; Avcu, S.; Nart, M.
Background: Use of contrast agents (CAs) during CT simulation for treatment planing system leads to changes in electron density. In this study we aimed to investigate the effect on calculated dose of various concentrations of CAs on treatment planing systems in different dose calculation algorithms. Materials and Methods: Contrast agent (0.769 mg/ml Iopromid) - water mixtures at concentrations of 0%, 1%, 2%, 5% and 10% in total volume of 500 ml for each were made by using five identical balloons. Calculations were performed by Cobalt-60 and 10 MV linear accelerator devices in CMS XIO treatment planning system. The prescribed dose of 100cGy was given to the center of balloon that is isocenter of SAD technique at 10cm from the surface. The doses at maximum dose depth (dmax) and at 5 cm were calculated according to the separate algorithms by either making or not making a correction for CA, and the results were recorded. Results: In all algorithms, as contrast ratio increases, the dose values at dmax and 5 cm-depth increase accordingly. When the doses at dmax and 5 cm-depth were compared for Linac and Co-60 in all algorithms, it has been shown that the dmax value of Co-60 was higher and the difference was greater in parallel with increasing contrast ratio in comparing with Linac. Conclusion: When required during the planning, the treatment plan should be calculated via providing an electron density correction by contouring the volume retaining CAs along the beam line.