Radyoterapide Kullanılan Yeni Tasarlanmış Koruyucu Blokların Gama Işını Geçirgenliklerinin Monte Carlo Simülasyonu

Abstract

Radyoterapi, günümüzde en yaygın hastalık olan kanserin en önemli tedavi yöntemlerinden biridir. Radyoterapi sırasında ışınlanan alan içindeki kritik organların ve sağlıklı dokuların korunması esastır. Bu nedenle her hastaya özel olarak yapılan Cerrobend blok (lipowitz alaşımı) hastanelerde yaygın olarak kullanılmaktadır. Klinik uygulamada, Cerrobend bloklar için kabul edilen gama ışını geçirgenlik seviyesi % 5'ten azdır. Bu çalışmada, GEANT4 tabanlı GATE simülasyon programı modellenerek, standart Cerrobend bloğunun gama ışını aktarımları farklı sayılarda saf kurşun bilyelerin ilave edilmesiyle oluşturulan yeni tasarlanmış Cerrobend blokların gama radyasyonu geçirgenlikleriyle karşılaştırılmıştır. 2010 yılında Dr. Abdurrahman Yurtaslan Ankara Onkoloji Eğitim ve Araştırma Hastanesinde, çeşitli radyasyon alan boyutları için Alcyon II model Co-60 teleterapi cihazı ile Farmer tipi 0,6 cc iyon odası, PTW Unidos Dozimetre ve katı fantom kullanılarak deneysel ölçümleri gerçekleştirilmiştir. Yeni tasarlanan Cerrobend blokların gama ışını geçirgenliği standart bloktan daha az olarak bulunmuştur, böylelikle hasta için kritik organların daha iyi korunması sağlanmış olacaktır. GEANT4 tabanlı GATE simülasyon programı ile elde edilen doz değerleri, deneysel olarak ölçülen radyasyon doz değerleri ile tutarlı olarak hesaplanmıştır. Ayrıca, XCOM yazılımından teorik olarak elde edilen doğrusal sönüm katsayısı, deney ve simülasyonla elde edilen sonuçlarla da uyumlu olarak bulunmuştur.

Keywords

• Cerrobend
• GATE simülasyonu
• doğrusal sönüm katsayısı
• ışın tedavisi
• koruyucu blok

Monte Carlo Simulation of the Gamma-Ray Transmissions for the newly Designed Shielding Blocks used in Radiotherapy

Abstract

Radiotherapy is one of the most important treatment methods of cancer, which is the worldwide disease nowa-days. It is essential to protect the critical organs and healthy tissue inside the radiated area during the radiotherapy. For this reason, Cerrobend block (lipowitz alloy), which is made specifically for each patient, are commonly used in the hospitals. In the clinical application, the acceptable level of the gamma-ray transmission for Cerrobend blocks must be less than 5%. In this research, GEANT4 based GATE simulation program modelled to compare between gamma-ray transmissions of the standard Cerrobend block and newly designed Cerrobend blocks formed by adding the various number of the pure lead marbles. Experimental measurements were carried out with Alcyon II model Co-60 teletherapy machine for various field sizes by using Farmer type 0,6 cc ion chamber, PTW Unidos Dosimeter and solid phantom in Dr. Abdurrahman Yurtaslan Ankara Oncology Training and Research Hospital in 2010. The gamma-ray transmission of the newly designed Cerrobend block was found less than the standard block, therefore the protection of the critical organs for the patient could be better. The dose acquired by GEANT4 based GATE simulation program is consistent in experimentally measured radiation dose. Furthermore, the values of the linear attenuation coefficient theoretically obtained from XCOM software agree with the values acquired by experiment and simulation.

Keywords

• correband
• GATE simulation
• radiotherapy
• shielding block
• linear attenuation coefficient

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