Browsing by Author "Tuğrul, Taylan"

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Estimation of Neutrons Occurring in the Linac Room at Differentphoton Energies
(2021) Tuğrul, Taylan
The high-energy photons produced by the Linear accelerator (Linac) induce some nuclearreactions in the materials in the Linac room and Linac head. Neutrons formed as a result of theinteraction of photons with materials are called photoneutrons. The aim of the study is to examine theneutron doses formed in the environment for 6 different photon energies. In the study, the componentsin the Linac head and the Linac chamber are modeled with the help of the Monte Carlo N-Particle(MCNP) program. Then, the flux and dose of photoneutrons formed at 8 different points as a result of 6different photon energies obtained from the Linac head were measured. as can be seen from the results,as the photon energy used in the Linac increases, the resulting dose, and flux of photoneutron increase.It can be understood from the results that the amount of neutron dose to be received by the organs inthe treatment field may be higher than the other organs. Especially in the treatments where the patientis lying in the prone position, there may be a possibility of neutrons reaching the patient spinal cord.Since photoneutrons with high radiobiological ability may pose a risk of secondary cancer for patients,the photon energy chosen for patient treatments should be chosen appropriately and the use ofunnecessary high photon energy should be avoided.
Investigation of the Dose Profiles in the Junction Region Between the Supraclavicular and Tangential Fields
(2024) Tuğrul, Taylan
Aim: To evaluate the homogeneity of the dose at the junction for fields used in breast radiotherapy using a different technique. Methods: A total of 4 fields, including 2 tangential fields and AP-PA fields, were planned on the phantom on the RayStation treatment planning system. Gamma analysis was used to compare the results of the measurement and treatment planning system. Results: When the graphs are analyzed, it is seen that the dose obtained in the junction region on the 2D measurement system as a result of the 1st tangential field and AP field irradiation is 8.3% less than the dose obtained in the treatment planning system. For the 2nd tangential field and PA field, this difference was obtained as 11.8%. When the horizontal profile in the junction region was analyzed as a result of irradiation of all areas, dose differences were measured between 12.5-8.2%. Due to the examination of a region with a high dose gradient, parameters such as the tongue-and-groove effect of MLCs, jaw calibration, parameters included in the treatment planning system's calculations, and measurement setup can directly impact the obtained data. Conclusions: The results of our study indicate that doses in the connection area should be planned by treatment centers with different techniques, examined with different dosimetric devices, and the acceptability of the obtained doses should be verified.
Measuring Out-Of Dose to the Whole Brain in Radiotherapy
(Yuzuncu Yil Universitesi Tip Fakultesi, 2024) Gül, Osman Vefa; Tuğrul, Taylan; Hikmettin, Demir
The aim of this study is to measure out-of-field lens and thyroid doses in whole brain radiotherapy with thermoluminescence dosimeters (TLD) and compare them with treatment planning system (TPS) calculation values. Before Computed Tomography (CT), TLDs were placed on the lens and thyroid surfaces of the rando phantom and then the phantom was scanned with CT. Data was transferred from CT to RayStation™ TPSs and then target volume and critical organs were determined. The treatment plan was created. TLDs were placed on the lens es and thyroid for out-of- field dose measurement. For the right lens, the mean value of TLD measurements were 188.3±2.2 cGy and the mean values of TPS measurement were 192.0±0.2 cGy. The average TLD measurement for the left lens was 190.2 ±0.5 cGy, and the average TPS dose reading was 192.0±0.1 cGy. For doses in the thyroid region, which is further from the target, the TLD measurement and TPS reading averages were 44.9±5.2 cGy and 40.9±6.3 cGy, respectively. Accordingly, right lens point doses calculated from TPS were 1.93% higher than TLD measurements. For the left lens, this difference in the same direction was determined as 0.93%. Within the thyroid region, TLD measurements were observed to be higher than TPS readings. We measured out-of-field doses via TLDs and found that TPS calculations for thyroid were 8.90% lower than the measured dose. The results we obtained from our study are guiding in estimating out -of-field lens and thyroid doses in 3DCRT whole brain irradiation.
Radyoterapide Kullanılan Baş Yastığının Dozimetrik Etkisinin Farklı Algoritmalarla İncelenmesi
(2021) Tuğrul, Taylan
GİRİŞ ve AMAÇ: Radyoterapide immobilizasyon cihazlarının kullanılması hastanın doğru pozisyon alması ve tedavinin doğru uygulanması için zorunludur. Tedavi sırasında hastanın hareketini kısıtlamak ve rahat bir şekilde yatışını sağlamak için baş yastıkları sıklıkla kullanılmaktadır. Bu çalışmanın amacı, baş yastığının doz dağılımı üzerindeki etkisini iki farklı algoritma kullanarak incelemektir. YÖNTEM ve GEREÇLER: Yedi hasta görüntüsündeki vücut konturları, baş yastıklı ve baş yastıksız olarak şekillendirildi. Baş yastığının vücut konturuna dahil edilip çıkarıldığı durumlarda hem Collapse Cone (CC) hem de Monte Carlo (MC) algoritmaları kullanılarak her hasta için vücut içindeki doz dağılımı hesaplandı. Elde edilen sonuçlar gama analizi yöntemi ile karşılaştırıldı. BULGULAR: Spesifik olarak, gama analizinin sonuçları, baş yastığı vücut konturuna dahil edildiğinde hastaya ulaşan dozların bir miktar azaldığını göstermektedir. CC algoritması, düşük yoğunluklu bir ortamda ikincil fotonların ve saçılan radyasyonun yeterince doğru hesaplanmasına izin vermediğinden, CC algoritmasının benzerlik sonuçları gama analizinde MC algoritmasına göre daha yüksektir. TARTIŞMA ve SONUÇ: Hastaya ulaşan radyasyon dozunun doğru bir şekilde hesaplanabilmesi için tedavi sırasında radyasyonun geçtiği tüm materyaller bir tedavi planlama sisteminde belirtilmelidir. Radyoterapide kullanılan immobilizasyon cihazlarının düşük yoğunluklu materyalden oluşsa bile hasta üzerindeki doz dağılımı üzerinde etkilerinin olduğu ve tedavi planlama sistemine dahil edilmesi gerektiği sonucuna varılmıştır.