Browsing by Author "Cakir, T."

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The Comparison of Absorbed Dose Measurements for Water and Artificial Body Fluid
(Ijrr-iranian Journal Radiation Res, 2012) Cakir, T.; Gur, A.; Arasoglu, A.
Background: Advances in radiation dosimetry concepts and the development of primary measurement standards based on absorbed dose to water over the last decades offer the possibility to calibrate ionisation chambers directly in terms of absorbed dose to water. The aim of this study is the investigation on utility of artificial body fluid (ABF) instead of water by comparing dosimetric measurements for radiotherapy between water and ABF which is more close to human tissue. Materials and Methods: The measurements were done using Co-60 gamma source with a radiation field sizes of 5 x 5, 10 x 10, 15 x 15, 20 x 20 and 25 x 25 cm(2) at PTW Freiburg MP3 water phantom front surface. The comparisons of the dose measurements were obtained by using IAEA TRS-398 dosimetry protocols and Mephysto mc(2) dose analyzer program. Percent depth dose (PDD), dose profiles and penumbras are compared for water and ABF. Results: When the results of the PDD for water and ABF were compared, the maximum difference was observed in big field sizes. The difference in penumbras was found 2.3 mm averagely for depth of maximum dose (d(max)). In addition same differences were observed between water and ABF when the dose profiles were compared. It is found that PDD values taken for water are good agreed with PDD values published in British Journal of Radiology (BJR) Supplement 25. Conclusion: Since the ABF is more equivalent to human tissue than water, it is suggested that advanced dosimetric studies should be performed with ABF instead of water. Iran. J. Radiat. Res., 2012; 10(3-4): 157-164
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.
Determination of Gamma and Fast Neutron Shielding Parameters of Magnetite Concretes
(Pergamon-elsevier Science Ltd, 2016) Oto, B.; Gur, A.; Kavaz, E.; Cakir, T.; Yaltay, N.
In this study, some gamma shielding parameters such as mass attenuation coefficient (mu(rho)), effective atomic number (Z(eff)), electron density (N-el) and buildup factors have been investigated for concretes with and without magnetite aggregate. The measurements have been carried out using 1.25 MeV (mean energy of 1.1732 MeV and 1.3325 MeV photons of a Co-60 radioactive source) gamma photons. The theoretical values of mu(rho) have been calculated in the energy range from 1 key to 100 GeV by WinXCom computer code and these values were used in order to calculate the values of Z(eff) and N-el. And fast neutron shielding parameter namely effective removal cross-sections (Sigma(R), cm(-1)) have been calculated. In addition, Energy absorption buildup factors (EABF) and exposure buildup factors (EBF) values of concrete samples have been calculated for photon energy 0.015-15 MeV up to 40 mfp (mean free path) penetration depths. The results of this study showed that the magnetite concrete is more efficient than the ordinary concrete for fast neutrons and gamma rays. (C) 2016 Elsevier Ltd. All rights reserved.
Dosimetric Comparison of 3d-Conformal and Imrt Techniques Used in Radiotherapy of Gastric Cancer: a Retrospective Study
(Prof.Dr. İskender AKKURT, 2024) Gul, O.V.; Demir, H.; Kanyilmaz, G.; Cakir, T.
This study aimed to compare three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) planning techniques commonly used in gastric cancer radiotherapy with dose volume histograms. Computed tomography (CT) images of 20 gastric cancer patients were retrospectively analyzed. 3D-CRT, 5F-IMRT and 7F-IMRT treatment plans were created for each patient. The 3 plans were compared on dose volume histogram (DVH). 3D-CRT, 5F-IMRT and 7F-IMRT plans achieved a prescribed dose of 45 Gy for 95% of PTV volume. D95 values were 45.06±0.47 Gy for 3D-CRT, 46.39±0.38 Gy for 5F-IMRT and 45.20±0.11 Gy for 7F-IMRT. In 3D-CRT, 5F-IMRT and 7F-IMRT techniques, the 13 Gy receiving volumes of the right kidney were found to be 35.08+9.59, 36.25+7.97 and 37.03+9.03 respectively. Moreover, the volume of the right kidney receiving a 20 Gy and 30 Gy dose received less dose with 5F-IMRT than with 7F-IMRT. Since each patient's critical organs are at different distances from the target and each technique has its own advantages in terms of critical organs, we suggest that the useful technique should be decided by clinical consensus. © IJCESEN.
Effect of Radiotherapy on Erythrocyte Catalase, and Carbonic Anhydrase Activities, Serum Levels of Some Trace Elements and Heavy Metals (Zn, Cu, Pb, Cd, Mn, Fe, Mg and Co) in Cancer Patients
(Ijrr-iranian Journal Radiation Res, 2022) Tuncer, G. Seven; Demir, H.; Izmirli, M.; Cakir, T.; Yilmazer, G.; Demir, C.
Background: We tried to reveal the relationship between the levels of some important minerals, rare elements and heavy metals by measuring serum cobalt (Co), lead (Pb), zinc (Zn), iron (Fe), copper (Cu), cadmium (Cd), magnesium (Mg), manganese (Mn), catalase (CAT) and carbonic anhydrase (CA) levels in head and neck, CNS, esophagus, stomach and breast cancers receiving radiotherapy. Materials and Methods: Serum Cu, Fe, Pb, Zn, Co, Mg, Mn and Cd levels were measured using atomic absorption spectrophotometry. Carbonic anhydrase activity (CA), CO2 hydration measurements were made using bromothymol blue method as indicator. Results: Catalase activity, carbonic anhydrase activity and serum copper, lead, zinc, iron, cobalt, cadmium, manganese, magnesium measurements for baseline and post-radiotherapy values differ greatly in cancer patients compared to healthy subjects (p<0.05). Conclusion: As a result, these findings have a significant impact on the pathophysiology of cancer. It can be argued that this paper shows a preliminary study for examining the effect of radiotherapy treatment on the activity of erythrocyte catalase, carbonic anhydrase and serum levels of cobalt, lead (Pb), zinc, iron, copper, cadmium, magnesium and manganese in the head and neck, CNS, stomach, esophagus and breast cancers receiving radiotherapy treatment.
Effects of Applied Electrical Field on Biochemical Parameters and Erythrocytes of Rats
(Mrs Pushpa Agarwal, 2006) Demir, H.; Cakir, T.; Karakaya, C.; Ilhan, A. Cebi; Onursal, N.; Gur, A.
The purpose of this study was to determine whether there was any effect of some biochemical parameters and erythrocyte carbonic anhydrase on electrical field stimulation in female rat. The experiments were performed under the animals' scientific procedures and conform to National Institute of Health guidelines for the use of experimental animals. This study was carried out on female Sprague-Dawley rats (250-270 g). Comparasons were made using student-t tests. A p value less than 0.001 was considered statistically significant. It was demonstrated that alanine aminotransferase, aspartate aminotransferase, amylase and lactate dehydrogenase in serum were significantly affected by this electric field stimulation (p < 0.001). In addition, particularly carbonic anhydrase activity was affected by applied electrical field.
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.
Photon Attenuation Properties of Concrete Produced With Pumice Aggregate and Colemanite Addition in Different Rates and the Effect of Curing Age To These Properties
(Pergamon-elsevier Science Ltd, 2015) Yaltay, N.; Ekinci, C. E.; Cakir, T.; Oto, B.
Radiation shielding properties of lightweight concrete produced with pumice aggregate and colemanite addition in different rates and effect of cure ages to the radiation shielding were investigated by using Co-60 (1250 key) radioactive source. Gamma rays were counted by 0.6 cc, Farmer type PTW (TM) Ion chamber. Experimental results were compared with the theoretical values calculated by WinXCom program. Consequently, colemanite addition make enhancement in the radiation shielding of the lightweight concrete, however there is no directly proportional relation between colemanite rate (0.4-2%) and attenuation properties of the lightweight concrete and cure age especially long timed, raises the linear attenuation coefficient and decreases the mean free path values. The theoretical values were obtained as nearby the experimental results, especially in the later cure ages (360 day). (C) 2014 Elsevier Ltd. All rights reserved.