Comparison of Error Detection Capabilities of Equipment Used in Patient-Specific Quality Assurance in Intensity Modulated Radiotherapy

Öz

Aim: The aim of this study is to compare the error detection capabilities of film, in-vivo EPID dosimetry, and two-dimensional detectors used in patient-specific quality assurance of IMRT plans. Method: Alderson Rando phantom was used in our study. In the first stage, two treatment plans were created on CT images of the Alderson Rando phantom. One of the created plans represents GBM treatment, while the other represents the treatment of the head and neck. These plans are called as the original plan. Then, the plans with errors were obtained by deliberately creating different types of errors. Quality controls of all plans were made with film, in-vivo EPID and 2D detectors. The obtained results were compared with the gamma analysis method. Results: The original plans passed the gamma analysis for all methods. MLC error was detected by in vivo EPID dosimetry for head and neck irradiation. Errors related to machine calibration were caught in all methods. Errors related to fraction dose, gantry and collimator angle could not be determined by the methods used in the study. Conclusions: There is no difference in error detection capabilities between film, 2D detectors and in-vivo EPID dosimeters, which are widely used in patient-specific quality control applications in IMRT treatments. All methods are sensitive to calibration errors. In-vivo EPID dosimetry comes to the fore in the detection of MLC errors. However, mechanical errors especially in the gantry and collimator could not be detected with the existing systems.

Anahtar Kelimeler

• Radiation therapy
• IMRT
• patient QA
• dosimetry

Yoğunluk Ayarlı Radyoterapide Hastaya Özel Kalite Kontrol Uygulamalarında Kullanılan Gereçlerin Hata Tespit Yeteneklerinin Karşılaştırılması

Öz

Amaç: Bu çalışmanın amacı, Yoğunluk Ayarlı Radyoterapi (YART) planlarının hastaya özel kalite kontrolü için kullanılan film, in-vivo elektronik portal görüntüleme cihazları (Electronically Portal Imaging Devices-EPID) ve iki boyutlu (2B) detektörlerin hata tespit yeteneklerini karşılaştırmaktır. Yöntem: Bu çalışmada, Alderson Rando fantom kullanılmıştır. İlk olarak, Alderson Rando fantomun bilgisayarlı tomografi (BT) görüntüleri üzerine glioblastoma (GBM) ve baş-boyun (HN) kanseri tedavisini temsil eden iki tedavi planı oluşturulmuştur. Bu planlar, orijinal planlar olarak adlandırılmıştır. Daha sonra, bilinçli bir şekilde farklı türde hatalar yaratılarak hatalı planlar elde edilmiştir. Film, in-vivo EPID ve 2B detektörler ile tüm planların hastaya özel kalite kontrolleri yapılmıştır. Elde edilen sonuçlar, gamma analizi yöntemi kullanılarak karşılaştırılmıştır. Bulgular: Orijinal planlar tüm yöntemlerde gamma analizi testini geçmiştir. HN radyoterapisi için çok yapraklı kolimatör (ÇYK) hatası, in-vivo EPID dozimetrisi ile tespit edilmiştir. Cihaz kalibrasyonu ile ilgili hatalar, tüm yöntemlerde yakalanmıştır. Ancak fraksiyon dozu, gantri ve kolimator açısına bağlı hatalar, kullanılan yöntemlerle tespit edilememiştir. Sonuç: Hastaya özel kalite kontrol uygulamalarında kullanılan film, 2B dedektörler ve in-vivo EPID dozimetresi arasında hata tespit yetenekleri bakımından belirgin bir fark bulunmamaktadır. Tüm yöntemler, kalibrasyon hatalarını tespit etme konusunda duyarlıdır. ÇYK hatalarının tespiti için in-vivo EPID dozimetrisi ön plana çıkmaktadır. Ancak özellikle gantri ve kolimatöre ait mekanik hatalar, mevcut sistemlerle tespit edilememektedir.

Anahtar Kelimeler

• Radyoterapi
• YART
• hasta QA
• dozimetri

Kaynakça

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