Browsing by Author "Tugrul, Taylan"

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Absorption Ratio of Treatment Couch and Effect on Surface and Build-Up Region Doses
(Elsevier Science Bv, 2018) Tugrul, Taylan
Aim: In this study, at different fields, energies and gantry angles, treatment couch and rails dose absorption ratio and treatment couch effect on surface and build-up region doses were examined. Background: It is assumed that radiation attenuation is minimal because the carbon fiber couches have low density and it is not generally accounted for during treatment planning. Consequently, it leads to a major dosimetric mistake. Materials and methods: Solid water phantom was used for relative dose measurement. The measurements were done using a Farmer ion chamber with 0.6 cc volume and a parallel plane ion chamber starting from surface with 1 mm depth intervals at 10 x 10 cm(2) field, SSD 100 cm. Measurements were taken for situations where the beams intersect the couch and couch rails. Results: Dose absorption ratio of carbon fiber couch obtained at gantry angle of 180 was 1.52%, 0.69%, 0.33% and 0.25% at different field sizes for 6 MV. For 15 MV, this ratio was 0.95%, 0.27%, 0.20% and 0.05%. The absorption ratio is between 3.4% and 1.22% when the beams intersect with couch rails. The couch effect increased surface dose from 14% to 70% for 6 MV and from 11.34% to 53.03% for 15 MV. Conclusions: The results showed that the carbon fiber couch increased surface dose during posterior irradiation. Therefore, the skin -sparing effect of the high energy beams was decreased. If the effect of couch is not considered, it may cause significant differences at dose which reaches the patient and may cause tissue problems such as erythema. (C) 2017 Greater Poland Cancer Centre. Published by Elsevier Sp. z o.o. All rights reserved.
Analysis of Water-Equivalent Materials Used During Irradiation in the Clinic With Xcom and Beamnrc
(Elsevier, 2020) Tugrul, Taylan; Erogul, Osman
The devices used in the departments of Radiology, Nuclear Medicine, and Radiation Oncology should check for precise dose at some periods. The purpose of study is to compare the materials used for dosimetric control using Monte Carlo (MC) simulation. For MC simulation, BEAMnrc and DOSXYZnrc were used. For photoelectric absorption and total absorption, XCOM was used. Five phantom materials were selected. These materials were PMMA, polystyrene, blood liquid, soft tissue, and water. The PDD's have calculated for each material by DOSXYZnrc. When Percent Depth Dose (PDD's) examined, we could see that the water and polystyrene behaved like soft tissue and blood. However, The PMMA material didn't match with water and other materials. As a result, dose distribution for any materials is independent of its atomic number. Density of material is more important for dose distribution at MV energies. For dosimetric control, density of material should be chosen close the water properties. PMMA material shouldn't use instead of water for dose control.
Clinical Commissioning and Dosimetric Verification of the Raystation Treatment Planning System
(V N Karazin Kharkiv Natl Univ, 2021) Tugrul, Taylan
Background: The software used by treatment planning systems (TPS) plays an important role for treatments using radiation. The accuracy of the calculated dose in radiation treatments depends on the assumptions made by the TPS. In this study, we summarize our methods and results regarding clinical commissioning of the basic functions needed for photon therapy. Materials and Method: Measurements were obtained for the 6 and 15 MV photon energies obtained from the Siemens Artiste linear accelerator device. Important data such as percent deep dose, profile and output measurements were taken in the water phantom and transferred to the RayStation Treatment Planning System. Results: When the absolute dose values calculated by the RayStation TPS are compared with the water phantom data, the differences obtained are less than 3%. When the 2-dimensional quality control of asymmetrical areas and patients with IMRT plan was controlled by gamma analysis method, the gamma rate was more than 95%. Conclusion: One of the most important quality control tests is TPS acceptance tests, which must be performed before clinical use. In this study, in which we checked the basic dose measurement and patient planning, it was seen that the RayStation TPS can be used in patient treatment for clinical use. The doses calculated by the RayStation TPS were found to be reliable and within the expected accuracy range. These results are sufficient for the application of 3-dimensional conformal radiotherapy (3D-CRT) and IMRT technique.
Comparison of Conformal Radiotherapy, Intensity-Modulated Radiotherapy and Tomotherapy Irradiation Techniques in Prostate Cancers
(Cambridge Univ Press, 2019) Tugrul, Taylan; Olacak, Nezahat; Koylu, Murat
Aim The aim of this study is to compare three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT) and tomotherapy techniques used in the treatment of prostate cancer with target and critical organ doses to be included. Materials and Methods The target dose was studied with 4-and 6-field 3D-CRT, 7-field IMRT and tomotherapy techniques used to treat ten patients for prostate cancer and the dose volume histograms of critical organs were analyzed. The same target volumes, critical organs doses prescribed and treatment times for the three techniques were compared. Total dose of 76 Gy was given using 6 MV and 18 MV for 3D-CRT, 6 MV for IMRT and tomotherapy techniques. Results When we compare the three techniques, for rectum V-35(p:0 center dot 001), V-65(p:0 center dot 001), D-50(p:0 center dot 020) and D-25(p:0 center dot 002), for bladder V-50(p:0 center dot 027), V-65(p:0 center dot 006), V-100(p:0 center dot 006) and for femoral head, the V-50(p:0 center dot 001) dose was found to be significantly different and more favourable in the tomotherapy technique. Significant differences were found with IMRT planning in 50% of bladder volume (p:0 center dot 002). There is no significant difference between the three techniques for doses of 100% volume of rectum and 25% of volume of bladder. The minimum dose that healthy tissue received which was outside the tumour volume was investigated. Findings Doses to critical organs were lower using the tomotherapy technique. However, the minimum doses that healthy tissue received were higher for the tomotherapy technique. When the beam on times were compared for all three techniques, a significant difference was found in favor of tomotherapy.
Comparison of Monaco Treatment Planning System Algorithms and Monte Carlo Simulation for Small Fields in Anthropomorphic Rando Phantom: the Esophagus Case
(Wolters Kluwer Medknow Publications, 2021) Tugrul, Taylan
Background: In this study, the dose distributions obtained by the algorithms used in Monaco treatment planning system (TPS) and Monte Carlo (MC) simulation were compared for small fields in the anthropomorphic RANDO phantom, and then, the results were analyzed using the gamma analysis method. Materials and Methods: In the study, dose distributions obtained from the collapse cone algorithm, MC algorithm, and MC simulation were examined. The EGSnrc was utilized for MC simulation. Results: In radiation fields smaller than 3 cm x 3 cm, the doses calculated by the CC algorithm are particularly high in the region of lung/soft-tissue interfaces. In the region of soft-tissue/vertebral interfaces, the doses calculated by the CC algorithm and the MC algorithm are compatible with the MC simulation. For each algorithm, the main reason for the non-overlapping dose curves in small fields compared to MC simulation is that the lateral electronic equilibrium loss is not taken into account by the algorithms. Conclusion: The doses calculated by the algorithms used in TPS may differ, especially in environments where density changes are sharp. Even if the radiation dose from different angles is calculated similarly in the target area by the algorithms, the calculated doses in the tissues in each radiation field path may be different. Therefore, to increase the quality of radiotherapy and to protect critical organs more accurately, the accuracy of the algorithms in TPS should be checked before treatment, especially in multi-field treatments such as stereotactic body radiation therapy and intensity-modulated radiotherapy for tumors in the abdominal region.
Determination of Initial Electron Parameters by Means of Monte Carlo Simulations for the Siemens Artiste Linac 6 Mv Photon Beam
(Elsevier Science Bv, 2019) Tugrul, Taylan; Erogul, Osman
Aim: In this study, we investigated initial electron parameters of Siemens Artiste Linac with 6 MV photon beam using the Monte Carlo method. Background: It is essential to define all the characteristics of initial electrons hitting the target, i.e. mean energy and full width of half maximum (FWHM) of the spatial distribution intensity, which is needed to run Monte Carlo simulations. The Monte Carlo is the most accurate method for simulation of radiotherapy treatments. Materials and methods: Linac head geometry was modeled using the BEAMnrc code. The phase space files were used as input file to DOSXYZnrc simulation to determine the dose distribution in a water phantom. We obtained percent depth dose curves and the lateral dose profile. All the results were obtained at 100 cm of SSD and for a 10 x 10 cm(2) field. Results: We concluded that there existed a good conformity between Monte Carlo simulation and measurement data when we used electron mean energy of 6.3 MeV and 0.30 cm FWHM value as initial parameters. We observed that FWHM values had very little effect on PDD and we found that the electron mean energy and FWHM values affected the lateral dose profile. However, these effects are between tolerance values. Conclusions: The initial parameters especially depend on components of a linac head. The phase space file which was obtained from Monte Carlo Simulation for a linac can be used as calculation of scattering, MLC leakage, to compare dose distribution on patients and in various studies. (C) 2019 Greater Poland Cancer Centre. Published by Elsevier B.V. All rights reserved.
The Effect of Algorithms on Dose Distribution in Inhomogeneous Phantom: Monaco Treatment Planning System Versus Monte Carlo Simulation
(Wolters Kluwer Medknow Publications, 2021) Tugrul, Taylan
Background: The aim of this study is to evaluate the dose calculation algorithms commonly used in TPS by using MC simulation in the highly different inhomogeneous region and in the small fields and to provide the following uniquely new information in the study of correction algorithm. Materials and Methods: We compared the dose distribution obtained by Monaco TPS for small fields. Results: When we examine lung medium, for four different fields, we can see that the algorithms begin to differ. In both the lung and bone environment, the percentage differences decrease as the field size increases. In areas less than or equal to 3x3 cm2, there are serious differences between the algorithms. The CC algorithm calculates a low dose value as the photon passes from the lung environment to water environment. We can also see that this algorithm measures a low dose value in voxel as the photon passes from the water medium to the bone medium. In the transition from the water environment to the bone environment or from the bone environment to the water environment, the results of the CC algorithm are not close to MC simulation. Conclusion: The effect of the algorithms used in TPS on dose distribution is very strong, especially in environment with high electron density variation and in applications such as Stereotactic Body Radiotherapy and Intensity Modulated Radiotherapy where small fields are used.
Effect of Different Target Materials of Linac Head on Photon Spectrum
(Taylor & Francis Ltd, 2021) Tugrul, Taylan
The X-rays were examined, which consist of the effect of 6 MeV energized electrons on different thickness and material of targets, using the MC method. When the PDDs are examined, we can see that the curves obtained for the Target 4 and Target 8 containing only tungsten material are very close PDD values to each other. The highest TPR20,10 value was also obtained for Target 8. For Target 4 and Target 8, which are composed only of tungsten material, when we examine the mean photon energy distributions formed, we observe an increase in energy towards the edge of the field. We obtained the closest TPR20,10 value for Target 6 to the TPR20,10 value generated by the original LINAC target (Target 1). However, the mean photon energy distribution value obtained for Target 6 is higher than the mean photon energy distribution value obtained from the Target 1. The mean photon energy distribution generated by the selected material according to the desired X-ray penetration and the homogeneity of this energy should be considered. The results obtained in the study are of a guiding nature both in modeling studies and for companies that will make target production.
The Effect of the Tongue and Groove of the Multileaf Collimator on Dose Distribution: Examination of Results of Measurements and Treatment Planning System
(Taylor & Francis Ltd, 2023) Tugrul, Taylan
Multileaf collimators play an important role in the field of radiotherapy and are widely used today. The effect of multileaf collimator structure on dose distribution should be well investigated and whether treatment planning systems reflect these effects on dose distribution should be examined. In our study, we examined the effect of tongue-and-groove on irregular fields and intensity-modulated radiotherapy plan. We also investigated the depth dependence of the tongue-and-groove effect. All fields are created in RayStation treatment planning system. Data obtained from treatment planning systems were compared with data obtained with 2-dimensional dose-measuring devices. We found the tongue-and-groove effect consistent in both measurements in single field measurements. We calculated dose reductions due to tongue-and-groove effect between 6% and 14%. When we examined the tongue-and-groove effect at different depths, we observed that the tongue-and-groove effect decreased as the depth increased. Although the tongue-and-groove effect did not create significant results on the dose distribution in multi-field use, we observed that this effect could occur at the edge of the field. Dose differences due to multileaf collimator structure should be examined by clinics. In addition, the extent to which treatment planning system takes these effects into account should be checked with some measurements. Otherwise, undesirable dose differences may be seen in the patient.
The Effects of Thymoquinone on Dna Damage, Apoptosis and Oxidative Stress in an Osteoblast Cell Line Exposed To Ionizing Radiation
(Taylor & Francis Ltd, 2021) Yilmaz, Osman; Yuksek, Veysel; Cetin, Sedat; Dede, Semiha; Tugrul, Taylan
Ionizing radiation (IR) may induce oxidative-stress-related molecular changes (DNA damage, cell death, etc.) in living organisms by affecting them directly and indirectly in a time- and dose-dependent manner. This study was planned to present the effects of thymoquinone (TQ) in preventing oxidative stress, DNA damage and apoptotic cell death that may occur after IR exposure. For this purpose, hFOB 1.19 osteoblast cells were used. Using the MTT viability test, the dose of IR reducing the proliferation of cells and the concentration of TQ increasing cell proliferation the most were determined. Five groups were formed as the Control (C), Thymoquinone (TQ), Ionizing radiation (IR), Ionizing radiation + Thymoquinone (IR + TQ) and Thymoquinone + Ionizing radiation (TQ + IR) groups. By applying the determined concentrations on the cells, DNA damage level was determined with the Comet assay, and the gene expression levels of enzymes effective in the oxidative and apoptotic mechanisms were determined with the RT-qPCR method expression. It was determined that, as a result of IR application for 24 and 72 h, DNA damage occurred in the osteoblast cell line. While no significant change was observed in the oxidative and apoptotic gene expression levels at the end of 24 h, an increase in comparison to the control group was determined in the Sod-1 (2.4-fold), Caspase-3, and Caspase-9 gene expression levels at the end of 72h. . Application of TQ in 72 h of incubation before and after IR application significantly reduced the expression levels of Caspase-3, Caspase-9, and DNA damage together with the increased GPx-3 and Sod-1 gene expression.Consequently, it was seen that IR application affected apoptotic and oxidative stress-regulating genes in the hFOB 1.19 osteoblast cell line in a time- and dose-dependent manner, and it was thought that the harmful effects on this cell line may have been caused by the activation of the mitochondrial pathway. It was determined that TQ significantly reduced the gene expression values that changed due to IR and brought them close to those of the control group, and it was concluded that TQ became useful by showing antioxidant properties against the harmful effects of IR.
Evaluation of Gamma Index Analysis for Detecting Errors in Patient-Specific Quality Assurance in Intensity Modulated Radiotherapy
(Lippincott Williams & Wilkins, 2025) Tugrul, Taylan
Quality assurance practices performed before treatment are believed to identify various potential errors. In this study, 2-dimensional (2D) dosimetric results were analyzed by making some intentional mistakes in six different treatment plans. In this way, the detectability of errors was investigated. In all segments of all treatment plans, one of the multileaf collimators was kept fixed at different positions on the central axis. In addition to multileaf collimators error, gantry error was also examined in the study. The dose distribution results obtained by Treatment Planning System (TPS) were compared with those obtained by the 2D array device, both as local calculation and global calculation methods, using the gamma analysis method. When the results are examined in the case where the Multi-leaf collimators (MLC) is fixed at the 1 cm position, the gamma analysis pass rate of the other plans, except two plans in the MD criterion, are calculated above the 95% limit. When the dose distributions obtained as a result of irradiation with 0.5-degree erroneous gantry angle were analyzed, it was found that all plans were at an acceptable rate in the maximum dose criterion. In case of incorrect irradiation, dose reduction or overdose may occur in the irradiated target area, even if gamma analysis pass rates are sufficient. Quality control procedures performed before treatment may be less effective. It is suggested that it would be better to examine the gamma analysis criteria applied for error detection with different values and local calculation method, and that device-based quality controls should be performed frequently.
Investigation of Buildup Region and Surface Dose: Comparison of Parallel Plane Ion Chamber, Treatment Planning System, and Mc Simulation
(Taylor & Francis inc, 2022) Tugrul, Taylan
In these days, Monte Carlo (MC) simulation is a method that can calculate the radiation dose that occurs in an environment in the most accurate way. The correct measurement of the dose occurring on the patient's surface is of great importance to estimate the reactions that may occur on the patient's skin. This importance encouraged us to do this study. The aim of this study is to determine buildup region and surface doses using MC simulation and to compare them with results of the parallel plane ion chamber and Treatment Planning System (TPS) measurements for 6-MV photon beams. Surface doses normalized to the maximum dose for the parallel plane ion chamber, MC simulation, fast photon (FP) algorithm, and collapsed cone convolution superposition (CC) algorithm are 13.6%, 30.28%, 0%, and 27.33%, respectively. The CC algorithm and parallel plane ion chamber measurements are compatible with MC simulation but the FP algorithm has calculated the dose less to a depth of 0.8 cm. Measuring the surface dose and the doses in the buildup region is of great importance in terms of accurately predicting the complications that may occur in the patient's skin and taking precautions early. Using some methods and correction factors, the surface dose and the doses that may occur in the buildup region can be accurately calculated. It is recommended not to use the FP algorithm for stereotactic body radiation therapy and intensity-modulated radiation therapy treatments, as it cannot calculate doses correctly in the buildup region and surface.
Investigation of Mass Attenuation Coefficients, Effective Atomic Numbers, and Effective Electron Density for Some Molecules: Study on Chemotherapy Drugs
(Elsevier, 2020) Tugrul, Taylan
Several authors have mentioned calculations of the effective atomic numbers (Z(eff)) and effective electron density (N-eff) on amino acids, carbohydrates, and nucleotides. Recently, numerous studies performed for determination of the mass attenuation coefficient (mu/rho), Z(eff) and N-eff on some biological compounds. However, theoretical studies for Z(eff), N-eff, and mu/rho for any of chemotrapy drugs is not available in the literature. For 11 different chemoterapy drugs, which are cisplatin, carboplatin, oxaliplatin, ifosfamide, gemcitabine, fluorouracil, pemetrexed, etoposide, vincristine, tamoxifen,and paclitaxel, by applying XCOM program we calculated the mu/rho values, and from these values, the Z(eff) and N-eff values have been acquired.Z(eff)N(eff)Z(eff) The minimum Z(eff) and N-eff values were seen at approximately 0.1 MeV < E < 3 MeV energies where Compton scattering is dominant. When molecules are compared, we can see that Z(eff) reaches the highest values for cisplatin, carboplatin and oxaliplatin that contain Pt element and a minimum Z(eff) value is obtained for Vincristine. Because the N-eff is related to Z(eff), the curves of the N-eff values on graphic exhibit same properties with Z(eff) values. It is thought that Z(eff) and N-eff values presented in this study should be known for use in various medical applications such as radiology, radiation oncology, etc.
Investigation of Photon Doses Reaching Healthy Tissues in the Use of Different Neutron Energies in Boron Neutron Capture Therapy
(Vinca inst Nuclear Sci, 2022) Tugrul, Taylan
Bo ron neu tron cap ture ther apy is a unique treat ment method that aims to kill the tu mor cells with the help of heavy par ti cles. Par ti cles re sult ing from the in ter ac tion of the tu mor re gion containing 10B at oms with ther mal or epi ther mal neu trons have the most im por tant role in this treat ment method. In this study, gamma ra di a tion reach ing healthy tis sues, which is the result of 10B(n,a)7Li reaction, was investigated. A simulation suitable for boron neutron cap-ture ther apy treat ment, in clud ing the hu man head model, was cre ated by the Monte Carlo N-Particle (MCNP) program. By using five different neutron energies, the gamma radiations resulting from the 10B(n,a)7Li re ac tion in the de ter mined re gions, close to the tu mor tis sue, were in ves ti gated. It was ob served that the healthy tis sue be tween the tu mor area and the sur - face is ex posed to the high est gamma flux and the high est gamma ra di a tion ab sorp tion. It was also ob served that these val ues in crease as neu tron en ergy de creases. It was found that the gamma doses re ceived by some re gions out side the neu tron ir ra di a tion area could be sig nif i - cant. It has been un der stood that the change in neu tron en ergy may cause sig nif i cant changes in gamma ra di a tion val ues reach ing healthy tis sues, es pe cially in re gions close to the sur face. In boron neu tron cap ture ther apy treat ments, the neu trons sent to the tu mor should be se -lected de pend ing on the lo ca tion of the tu mor and the size of the tu mor area. This study con -tains sig nif i cant data about pho ton doses in healthy tis sues around the brain re gion treated us ing dif fer ent neu tron en er gies with the boron neu tron cap ture ther apy tech nique.
Investigation of Radiological Properties of Imaging Agents Used in Nu Clear Med I Cine With Dif Fer Ent Meth Ods and Gate/Geant4 Sim U La Tion Pro Gram
(Vinca inst Nuclear Sci, 2023) Sahmaran, Turan; Tugrul, Taylan
This study aims to determine the radiological properties of various radiopharmaceuticals used in nuclear medicine. In the study, mass attenuation coefficient values in different energy ranges were ob tained for six dif fer ent radiopharmaceuticals dimercaptosuccinic acid, diethylenetriamine pentaacetate, mercaptoacetyltriglycine, hexamethylpropyleneamine oxime, methoxyisobutylisonitrile, meth y lene diphosphate by us ing GATE sim u la tion pro gram, XCOM and WinXCom pro grams. Us ing these val ues, ef fec tive atomic num ber and elec tron den sity val ues were cal cu lated with the help of the di rect method, in ter po la tion method, Auto-Zeff soft ware, Phy-X/ZeXTra, XMuDat pro gram, and Mayneourd's for mula. In ad di tion, the ef fec tive atomic num ber and elec tron den sity val ues ob tained were com pared for each radiopharmaceutical, both among them selves and be tween the meth ods. When radiopharmaceuticals were com pared among them selves in low and high-en ergy re gions, the high est ef fec tive atomic num ber val ues were ob tained in dimercaptosuccinic acid, meth y lene diphosphate, and mercaptoacetyltriglycine. The mass attenuation coefficient values calculated us ing the GATE code in di cate that it is a suit able method for de ter min ing the mass at tenuation coefficient for imaging agents with no experimental values. This study indicates that the sim u la tion ge om e try method is suit able to be used as an al ter na tive method for the ex per i ments. In ad di tion, the val ues ob tained for these mol e cules used as radiopharmaceuticals were ex am ined for the first time.