Verification of Percentage Depth-Doses with Monte Carlo Simulation and Calculation of Mass Attenuation Coefficients for Various Patient Tissues in Radiation Therapy

Öz

Objective: First part of this work dedicated to the verification of the percentage depth dose curves that obtained experimentally for 6 MV and 18 MV x-ray photon beams via using Geant4 Monte Carlo simulation. Second part of this study compared the computed mass attenuation coefficients of various human tissues and water between MATLAB and XCOM. Material-Methods: The central-axis percentage depth doses of Varian Clinac IX linear accelerator were verified via Monte Carlo simulation (Geant4) with square field sizes (10x10 and 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 with MATLAB and were compared with the NIST XCOM data. Results: Results of the Geant4 modeling were in line with the experimental measurements for percentage depth dose curves. The consistency of Geant4 with experimental results was more explicit for 6 MV photons with the field size of 10x10 cm2. No statistical significant difference between MATLAB and XCOM were found for all mentioned human tissues, except for bone (p=0.039 for bone in both genders). The minimum median percentage difference were calculated for water and skin with a result of 1.23% and 2.19%, respectively. Conclusion: Geant4 can be used to predict percentage depth dose curves for medical linacs. Mass attenuation coefficients calculated with MATLAB yielded consistent results with previous studies, which means MATLAB can be used as an alternative simulation tool for estimating mass attenuation coefficients of various human tissues and water.

Anahtar Kelimeler

• Radiation therapy,Geant4,MATLAB,Mass attenuation coefficient,Percentage depth dose

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

Öz

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.

Anahtar Kelimeler

• Radyoterapi,Geant4,MATLAB,Kütle zayıflatma katsayısı,Yüzde derin doz

Kaynakça

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