Radyoterapide Monte Carlo Simülasyonu ile Yüzde Derin Dozların Doğrulanması ve Çeşitli Hasta Dokuları İçin Kütle Zayıflatma Katsayılarının Hesaplanması

Amaç: Bu çalışmanın ilk kısmında, 6 MV ve 18 MV x-ışını foton demeti için deneysel olarak elde edilen yüzde derin doz eğrilerinin, Geant4 Monte Carlo simülasyonu kullanılarak doğrulanması amaçlanmıştır. Buna ek olarak; çalışmanın ikinci kısmında, MATLAB ve XCOM programları kullanılarak, çeşitli insan dokularının ve suyun kütle zayıflatma katsayıları hesap edilerek karşılaştırıldı. Materyal-Metot: Varian Clinac IX lineer hızlandırıcı cihazında deneysel olarak ölçülen merkezi eksen yüzde derin dozları; 6 MV ve 18 MV x-ışını foton enerjileri için 10x10 cm2 ve 30x30 cm2 alan boyutlarında, Monte Carlo simülasyonu (Geant4) ile hesap edilerek doğrulandı. Ek olarak; kan, kemik, yağ dokusu, kas, deri ve suyun kütle zayıflama katsayıları MATLAB ile hesaplanarak, NIST XCOM verileri ile karşılaştırıldı. Bulgular: Geant4 modellemesinin sonuçları, yüzde derin doz eğrileri için deneysel ölçümlerle uyumlu bulundu. Geant4' ün; deneysel sonuçlar ile tutarlılığı, 10x10 cm2 alan büyüklüğünde 6 MV foton enerjisi için daha belirgindi. MATLAB ve XCOM sonuçları arasında; bahsi geçen tüm insan dokuları için kemik hariç hiçbirinde istatistiksel olarak anlamlı bir fark bulunmadı (her iki cinsiyette kemik için p=0,039). En düşük medyan yüzde farkı, su ve cilt için sırasıyla %1,23 ve %2,19 olarak hesaplandı. Sonuç: Geant4, tıbbi linaklarda, yüzde derin doz eğrilerini hesaplamak için kullanılabilir. MATLAB ile hesaplanan kütle zayıflatma katsayıları önceki çalışmalarda diğer yazılım programları ile elde edilen sonuçlarla tutarlı bulundu. Bu da, MATLAB'ın çeşitli insan dokularının yanı sıra suyun kütle zayıflama katsayılarını hesap etmek için alternatif bir simülasyon aracı olarak kullanılabileceğini göstermektedir.

Verification Of Percentage Depth-Doses With Monte Carlo Simulation and Calculation Of Mass Attenuation Coefficients For Various Patient Tissues In Radiation Therapy

Objective: First part of this work dedicated to theverification of the percentage depth dose curves that obtainedexperimentally for 6 MV and 18 MV x-ray photon beams viausing Geant4 Monte Carlo simulation. Second part of thisstudy compared the computed mass attenuation coefficientsof various human tissues and water between MATLAB andXCOM.Material-Method: The central-axis percentage depth doses ofVarian Clinac IX linear accelerator were verified via MonteCarlo simulation (Geant4) with square field sizes (10x10and 30x30 cm2) for 6 MV and 18 MV x-ray photon energies.In addition, mass attenuation coefficients of adipose tissue,blood, muscle, bone, skin and water were computed withMATLAB and were compared with the NIST XCOM data.Results: Results of the Geant4 modeling were in line with theexperimental measurements for percentage depth dose curves.The consistency of Geant4 with experimental results was moreexplicit for 6 MV photons with the field size of 10x10 cm2.No statistically significant difference between MATLAB andXCOM were found for all mentioned human tissues, exceptfor bone (p=0.039 for bone in both genders). The minimummedian percentage differences were calculated for water andskin with a result of 1.23% and 2.19%, respectively.Conclusions: Geant4 can be used to predict percentage depthdose curves for medical linacs. Mass attenuation coefficientscalculated with MATLAB yielded consistent results withprevious studies, which means MATLAB can be used as analternative simulation tool for estimating mass attenuationcoefficients of various human tissues and water.

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