Meme kanseri radyoterapisinde 3 boyutlu bilgisayarlı planlama ve dozimetrik sürecin randofantom üzerinde termolüminesans dozimetri ile kontrolü
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Date
2009
Authors
Yeşil, Abdullah
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Publisher
Uludağ Üniversitesi
Abstract
Bu çalışmanın amacı sol meme radyoterapisinde, iki farklı yöntem ile [kaynak-cilt mesafeli (SSD) ve kaynak-eksen mesafeli (SAD)] elde edilen, hedef volüm ve kritik organ dozlarını, birbirleriyle ve 3 boyutlu bilgisayarlı tedavi planlama sisteminden (BTPS) elde edilen verilerle karşılaştırmak ve in-vivo dozimetriyle doz hesaplama algoritmasında kullanılan dozimetrik sürecin kontrolüdür.Sunulan çalışmada Uludağ Üniversitesi Tıp Fakültesi Radyoterapi Merkezi'nde bulunan tedavi planlama ve uygulama sistemleri ile dozimetrik ekipman kullanılmıştır. Randofantom üzerinde ölçüm yapılacak noktalara yalancı TLD'ler yerleştirildi ve BT simülatör ile 0,5 cm aralıklarla tomografi kesitleri alındı. Hedef volümler, kritik organlar konturlandı ve BTPS'ye aktarıldı. Meme radyoterapisinde kullanılan alanlar hem SSD hem de SAD tekniği için ayrı ayrı belirlendi. BTPS'den elde edilen dijital radyografilere uygun olarak göğüs duvarı (meme), mammaria interna (Mİ) ve supraklavikuler fossa (SCF) alanları konvansiyonel simülatörde randofantom üzerine çizildi. Alınan simülasyon filmleri BTPS'ne aktarılarak kontrol edildi ve nokta doz değerleri hesaplandı. Kalibre edilen TLD'ler randofantom üzerine önceden belirlenen noktalara yerleştirildi. Her teknik için 5'er kez ışınlama yapılarak ölçüm değerlerinin ortalamaları elde edildi. Işınlama öncesinde alanların port filmleri çekilerek simülasyon filmleri ile karşılaştırılıp kontrol edildi. Bu işlemler SSD ve SAD teknikleri için ayrı ayrı yapıldı. Çalışmada hedef hacim ve kritik organ (sol akciğer, kalp ve sağ meme) dozları incelendi. Ayrıca supraklavikuler fossa ve mammmaria interna ile tanjansiyel alanların bitiştiği bölgelerdeki dozlara bakıldı. BTPS ve ölçülen değerler arasında ±%5'in altındaki değerler kabul edilebilir sınırlar içine alındı.Üç ve dört alan SSD tekniğiyle hedef volüm (sol meme) içindeki üç noktada BTPS ile hesaplanan doz değerlerinin ortalaması sırasıyla 206.67 cGy ve 209.03 cGy iken, bu noktalarda TLD ile ölçülen dozların ortalaması sırasıyla 208.55 cGy ve 210.78 cGy'dir. Aradaki fark %2'in altında olup bu değer SAD tekniğinde de %2'in altındaydı. Her iki teknikte de kalp ve akciğer noktalarında ölçülen ve hesaplanan dozlar arasındaki fark %5'in altındayken sağ meme cildinde %10-%14 arasında fark bulundu.Supraklaviküler alan ile tanjansiyel alanların çakışma düzleminde üç ve dört alan SSD tekniğiyle hesaplanan ve ölçülen dozlar arasındaki fark sırasıyla %5.91 ve % 4.31 iken SAD tekniğinde bu değerler sırasıyla %4.15 ve %3.83 idi. Mammaria interna alanı ile tanjansiyel alanların çakışma bölgesinde, foton-foton çakışması için SSD ve SAD tekniklerinde saptanan farklar sırasıyla %8.64 ve %7.5, foton-elektron çakışması için SSD ve SAD teknikleriyle saptanan farlar ise %3.36 ve %2'dir. Üç ve dört alan tekniklerinde santral aks üzerinde elde edilen giriş-çıkış dozları için, hesaplanan ve ölçülen değerler arasındaki fark da %5'in altında idi.Çalışmamızda elde edilen sonuçlar tedavi planlama sürecinde oluşabilecek hataların belirlenmesinde TLD ile yapılan in-vivo doz ölçümlerinin, ideal olmasa da, yararlı olabileceğini göstermektedir. Ayrıca SAD tekniğiyle elde edilen sonuçların daha iyi olması set up hatalarını azaltması nedeniyle SSD tekniğine üstün olduğunu göstermektedir.
The purpose of this study is to compare the target volume and critical organ doses which are obtained from two different methods (source-skin distance (SSD) and source-axis distance (SAD)) at the left breast radiotherapy with each other and with the data obtained from 3D computer-based treatment planning system (TPS) and is the control of the dosimetric process by in-vivo dosimetric method.Treatment planning and application system and dosimetric equipment located in Uludag University Medical Faculty Radiation Oncology Center were used at the presented study. Dummy TLDs were placed on the randophantom to the measurement points and tomography cutaways were taken with CT simulator by 0.5 cm interwals. Target volumes and critical organs were contured and transferred to TPS. The fields used in breast radiotherapy were defined for both SSD and SAD methods seperately. Chest wall (breast), mammaria interna (MI) and supraclavicular fossa (SCF) fields were drawn on randophantom at the convensional simulator according to the digital radiographics taken from TPS. The recorded simulation films were controlled by transferring them to TPS and the point doses values were calculated. Calibrated TLDs were placed to the points defined in advance. Average of the measurements values was calculated by 5 times irradiation for each methods. Before the irradiation, the port films of the fields were taken and compared with the simulation films. These operations were done seperately for both SSD and SAD methods. In the study, target volume and critical organs (left lung, heart and right breast) doses were investigated. Furthermore the doses at the sections where supraclavicular fossa and mammaria interna is getting contiguous with the tangential areas investigated. TPS and measured values were taken into acceptable limits under the %5.Whereas the average of dose values calculated with TPS at three points in target volume (left breast) by three and four field SSD methods were respectively 206.67 cGy and 209.03 cGy, the avarage of measured doses at this points with TLD were respectively 208.55 cGy and 210 cGy. The difference is below %2 and this value was also below %2 at SAD method. Whereas the difference of measured and calculated doses at the heart and left lung points with both methods were below %5, the difference at right breast skin was calculated as %10-%14. Whereas the difference of the doses measured and calculated with three and four field SSD methods at coincidence plane of supraclavicular area and tangential areas were respectively %5.91 and %4.31, with SAD there were %4.15 and %3.83. The difference of photon-photon coincidence at the coindience plane of mammaria interna and tangential fields by SSD and SAD methods were respectively %8.64 and %7.5, the differences of photon-electron coincidence established by SSD and SAD methods are respectively %3.36 and %2. The difference of calculated and measured values was below %5 for input-output doses received on central axis with both methods.The results observed in our study have shown that in-vivo doses measurements made with TLD are not ideal but helpful for defining the failures which may show up during the treatment planning process. Furthermore, since the beter results received with SAD means reduction in set-up failures, SAD can be descriped as more preferable then SSD.
The purpose of this study is to compare the target volume and critical organ doses which are obtained from two different methods (source-skin distance (SSD) and source-axis distance (SAD)) at the left breast radiotherapy with each other and with the data obtained from 3D computer-based treatment planning system (TPS) and is the control of the dosimetric process by in-vivo dosimetric method.Treatment planning and application system and dosimetric equipment located in Uludag University Medical Faculty Radiation Oncology Center were used at the presented study. Dummy TLDs were placed on the randophantom to the measurement points and tomography cutaways were taken with CT simulator by 0.5 cm interwals. Target volumes and critical organs were contured and transferred to TPS. The fields used in breast radiotherapy were defined for both SSD and SAD methods seperately. Chest wall (breast), mammaria interna (MI) and supraclavicular fossa (SCF) fields were drawn on randophantom at the convensional simulator according to the digital radiographics taken from TPS. The recorded simulation films were controlled by transferring them to TPS and the point doses values were calculated. Calibrated TLDs were placed to the points defined in advance. Average of the measurements values was calculated by 5 times irradiation for each methods. Before the irradiation, the port films of the fields were taken and compared with the simulation films. These operations were done seperately for both SSD and SAD methods. In the study, target volume and critical organs (left lung, heart and right breast) doses were investigated. Furthermore the doses at the sections where supraclavicular fossa and mammaria interna is getting contiguous with the tangential areas investigated. TPS and measured values were taken into acceptable limits under the %5.Whereas the average of dose values calculated with TPS at three points in target volume (left breast) by three and four field SSD methods were respectively 206.67 cGy and 209.03 cGy, the avarage of measured doses at this points with TLD were respectively 208.55 cGy and 210 cGy. The difference is below %2 and this value was also below %2 at SAD method. Whereas the difference of measured and calculated doses at the heart and left lung points with both methods were below %5, the difference at right breast skin was calculated as %10-%14. Whereas the difference of the doses measured and calculated with three and four field SSD methods at coincidence plane of supraclavicular area and tangential areas were respectively %5.91 and %4.31, with SAD there were %4.15 and %3.83. The difference of photon-photon coincidence at the coindience plane of mammaria interna and tangential fields by SSD and SAD methods were respectively %8.64 and %7.5, the differences of photon-electron coincidence established by SSD and SAD methods are respectively %3.36 and %2. The difference of calculated and measured values was below %5 for input-output doses received on central axis with both methods.The results observed in our study have shown that in-vivo doses measurements made with TLD are not ideal but helpful for defining the failures which may show up during the treatment planning process. Furthermore, since the beter results received with SAD means reduction in set-up failures, SAD can be descriped as more preferable then SSD.
Description
Keywords
Meme ışınlaması, Termolüminesans dozimetri (TLD), Rando fantom, Bilgisayarlı tedavi planlama sistemi (BTPS), Breast irradiation, Thermoluminescence dosimetry (TLD), Randophantom, Computer-based treatment planning system (TPS)
Citation
Yeşil, A. (2009). Meme kanseri radyoterapisinde 3 boyutlu bilgisayarlı planlama ve dozimetrik sürecin randofantom üzerinde termolüminesans dozimetri ile kontrolü. Yayınlanmamış yüksek lisans tezi. Uludağ Üniversitesi Sağlık Bilimleri Enstitüsü.