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Abstract

Aim: This study aims at examining the differences between thermoluminescense dosimeters and metal oxide semiconductor field effect transistors in terms of radiation doses at different photon energies treatment area dependence in patients who recieved radiotherapy at the Department of Radiation Oncology, İnönü University. Material and Methods: Thermoluminescense dosimeter systems and metal oxide semiconductor fıeld effect transistors were used at 6MV and 25MV in the range of 25-1000 cGy radiation doses to examine radiation dose dependence. Results were evaluated by taking measurements of treatment areas 5x5, 10x10, 15x15, 20x20, 25x25, 30x30, and 40x40 cm², respectively, to specify treatment area dependence of these systems. Results: In both thermoluminescense dosimeters (TLD) and metal oxide semiconductor field effect transistors (MOSFET), reading values at 6 MV and 25 MV photon energies remained up to 800 cGy. We observed that both systems deviate from linearity at doses above 800 cGy. In TLDs, we recorded a %±1 (6 MV photon energy) and %+4 (25 MV photon energy) change in reading values. This change was %±1 (6 MV photon energy) and %+4 (25 MV photon energy) in MOSFETs. Conclusion: Both dosimeter systems have advantages and disadvantages in terms of accuracy and applicability. Being familiar with dosimeter systems is very important in identifying the accuracy of dose to be admisnistered

Keywords

• Radiotherapy; Invivo dosimeter; Thermoluminescense Dosimeter; Metal oxide semiconductor fıeld effect transistor; Linear accelerator

A Comparative Study of Radiation Doses and Treatment Area Dependence in Thermoluminescence Dosimetry Systems and Metal Oxide Semiconductor Field Effect Transistors / Radyasyon Dozu ve Tedavi Alanı Bağımlılıklarının Termolüminesans Dozimetre Sistemleri ve

Öz

Abstract

Aim: This study aims at examining the differences between thermoluminescense dosimeters and metal oxide semiconductor field effect transistors in terms of radiation doses at different photon energies treatment area dependence in patients who recieved radiotherapy at the Department of Radiation Oncology, İnönü University.

Material and Methods: Thermoluminescense dosimeter systems and metal oxide semiconductor fıeld effect transistors were used at 6MV and 25MV in the range of 25-1000 cGy radiation doses to examine radiation dose dependence. Results were evaluated by taking measurements of treatment areas 5x5, 10x10, 15x15, 20x20, 25x25, 30x30, and 40x40 cm², respectively, to specify treatment area dependence of these systems.

Results: In both thermoluminescense dosimeters (TLD) and metal oxide semiconductor field effect transistors (MOSFET), reading values at 6 MV and 25 MV photon energies remained up to 800 cGy. We observed that both systems deviate from linearity at doses above 800 cGy. In TLDs, we recorded a %±1 (6 MV photon energy) and %+4 (25 MV photon energy) change in reading values. This change was %±1 (6 MV photon energy) and %+4 (25 MV photon energy) in MOSFETs.

Conclusion: Both dosimeter systems have advantages and disadvantages in terms of accuracy and applicability. Being familiar with dosimeter systems is very important in identifying the accuracy of dose to be admisnistered.

Key Words: Radiotherapy; Invivo dosimeter; Thermoluminescense Dosimeter; Metal oxide semiconductor fıeld effect transistor; Linear accelerator.

 Özet

Amaç: Bu çalışmada, radyoterapi alan hastaların giriş dozunun belirlenmesi için İnönü Üniversitesi Tıp Fakültesi Radyasyon Onkolojisi Anabilim Dalı’nda kullanılan in vivo dozimetre sistemlerinin farklı foton enerjilerinde radyasyon dozu ve tedavi alanına bağımlılıklarının incelenmesi amaçlanmıştır.

Gereç ve Yöntemler: Çalışmada termolüminesans dozimetre ve metal oksit yarıiletken alan etkili transistör invivo dozimetre sistemleri ile lineer hızlandırıcı cihazının 6 MV ve 25 MV foton enerjileri kullanılmıştır. Dozimetre sistemlerinin radyasyon dozu bağımlılığının incelenmesi için 25-1000 cGy radyasyon dozu aralığında ışınlamalar yapılmıştır. Sistemlerin tedavi alanına bağımlılığının belirlenmesi için ise sırasıyla 5x5, 10x10, 15x15, 20x20, 25x25, 30x30, 40x40 cm²’lik tedavi alanlarında ölçümler alınarak sonuçlar değerlendirilmiştir.

Bulgular: 6 MV ve 25 MV foton enerjilerinde artan radyasyon doz değerlerine bağlı okuma değerleri değişimi metal oksit yarıiletken alan etkili transistör dozimetre sisteminde lineer iken, temolüminesans dozimetrede 800 cGy’e kadar lineer, 800 cGy’den sonra ise lineerlikten saptığı gözlenmiştir. Artan tedavi alanı boyutuna bağlı okuma değerleri değişimi ise temolüminesans dozimetrelerde 6 MV foton enerjisi için %±1, 25 MV foton enerjisi için %+4 değerindedir. Metal oksit yarıiletken alan etkili transistör dozimetre sisteminde 6 MV foton enerjisinde değişim %± 1 iken 25 MV foton enerjisinde % ± 4 değerinde olduğu görülmüştür.

Sonuç: İnvivo dozimetrelerin birbirlerine göre bazı üstünlükleri vardır. Günlük kullanımda kullanıcıların dozimetre sistemlerini tanımaları ve ölçüm sonuçlarını etkileyecek özelliklerini bilmeleri, radyoterapi uygulanan hastaya verilen dozların doğruluğunun tespit edilmesi açısından oldukça önemlidir.

Anahtar Kelimeler: Radyoterapi; İn vivo Dozimetre; Termolüminesans Dozimetre; Metal Oksit Yarıiletken Alan Etkili Transistör; Lineer Hızlandırıcı.

Anahtar Kelimeler

• Radyoterapi; İn vivo Dozimetre; Termolüminesans Dozimetre; Metal Oksit Yarıiletken Alan Etkili Transistör; Lineer Hızlandırıcı

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