Hamit BAŞARAN, Osman Vefa GÜL, Gökçen İNAN

Farklı Radyoterapi Teknikleri İle Meme Işınlamalarında Alan Dışı Dozların TLD İle Dozimetrik Olarak İncelenmesi

Amaç: Bu çalışmada Alderson Rando fantom üzerinde, tüm meme kanseri tedavisinde farklı organlarda absorbe edilen doz araştırılmıştır. Farklı organlardaki ortalama doz için tedavi planlama sistemi (TPS) ve termolüminesans dozimetre (TLD) doz ölçümleri karşılaştırılmıştır. Gereç ve Yöntemler: İnsan ölçüleri ile fiziksel olarak benzer şekilde üretilen fantom üzerinde sol meme dokusu hedef hacim olarak seçildi. Varian DHX cihazında 3DCRT, 5 Alan- IMRT, 7 Alan- IMRT tedavi planları oluşturuldu. Fantomda belirlenen hacim içindeki yerlere TLD-100 dozimetreleri yerleştirildikten sonra ışınlandı. Daha sonra her bir teknik için elde edilen doz ölçümleri TPS dozları ile karşılaştırıldı. Bulgular: 3DCRT, 5 Alan- IMRT ve 7 Alan- IMRT tekniklerinde planlanan hedef volümün (PTV) ortalama doz değeri için TPS dozları ve TLD dozları arasındaki istatistiksel anlamlılık sırasıyla, p=0.042, p=0.002 ve p=0.030 olarak bulunmuştur. Tiroid’in ortalama dozunda IMRT tekniği ile yapılan planlarda TPS ve TLD dozları arasındaki farkın arttığı görülmüştür. Fetüs dozları incelendiğinde TPS ile doz saptanmazken TLD ile ortalama fetüs dozu 3.13-16.87 cGy olarak bulunmuştur. Ayrıca parotis dozları incelendiğinde TPS ile doz saptanmazken TLD ile ortalama parotis dozu 10.37- 57.75 cGy olarak ölçülmüştür. Sonuç: TPS’in 8 cm’den uzak mesafelerde organ dozlarını tahmin etmede başarısız olduğu söylenebilir. Meme radyoterapisinde 3DCRT tedavi tekniğinin tercih edilmesi daha avantajlı olacaktır.

Dosimetric Examination of Out-of-Field Doses with TLD in Breast Irradiation with Different Radiotherapy Techniques

Objective: In this study, the absorbed dose in different organs was investigated in the treatment of whole breast cancer on the Alderson Rando phantom.Treatment planning system (TPS) and thermolu- minescence dosimeter (TLD) dose measurements were compared for the mean dose in different organs. Material and Methods: The left breast tissue was chosen as the target volume on the phantom, which was produced physically similar to human dimensions. 3DCRT, 5 Field-IMRT, 7 Field-IMRT treatment plans were created in the Varian DHX device. After TLD-100 dosimeters were placed in the places in the determined volume in the phantom, they were irradiated. Then, the dose measurements obtained for each technique were compared with the TPS doses. Results: The statistical significance between TPS doses and TLD doses for the mean dose value of the planned target volume (PTV) in 3DCRT, 5 Fields- IMRT, 7 Fields- IMRT techniques were found as p = 0.042, p = 0.002 and p = 0.030, respective- ly. It was observed that the difference between TPS and TLD doses increased in the plans made with the IMRT technique in the mean dose of the thyroid. When the fetus doses were examined, the dose was not determined with TPS, while the average fetus dose was found to be 3.13-16.87 cGy with TLD. In addition, when the parotid doses were examined, the dose was not determined with TPS, while the mean parotid dose was measured as 10.37-57.75 cGy with TLD. Conclusion: It can be said that TPS fails to estimate organ doses at distanc- es greater than 8 cm. It will be more advantageous to choose the 3DCRT treatment technique in breast radiotherapy.

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