Evaluation of the conformal radiotherapy techniques in prostate cancer

Abstract

OBJECTIVES We aimed to determine the optimal radiotherapy technique enabling the most homogenous dose distribution for Clinic Target Volume (CTV) and Planned Target Volume (PTV) and providing conformal avoidance of Organs at Risk (OAR). METHODS CTV, PTV, and OAR were outlined by utilization of Sim-Pro (CMS-USA) using 5 mm slice spaced computed tomography scans. For each patient, individual 4, 5, 6, and 7 field plans, with 18 MV photons, were assessed with XiO (CMS-USA) 3D planning workstation. RESULTS In comparing the different techniques, the greatest rectal sparing was achieved with the 5 field plan (Rectal: 5F V25%=59.90±6.8 Gy, 4F V25%=62.30±10.3 Gy, 6F V25%=69.36±5.7 Gy, 7F V25%=61.32±7.3 Gy). CONCLUSION While all the techniques achieved the goal of optimal homogeneity of CTV-PTV, 4F provided the lowest femoral doses. The greatest rectal sparing was achieved with 5 field conformal technique.

Keywords

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Prostat kanserinin radyoterapisinde konformal radyoterapi tekniklerinin değerlendirilmesi

Öz

AMAÇ Prostat kanseri tanılı hastaların konformal radyoterapisinde farklı tedavi teknikleri kullanılarak PTV ve CTV için en homojen doz dağılımını veren, bununla beraber doz sınırlayıcı organ olan mesane, rektum ve femur başı için en uygun teknik araştırıldı. GEREÇ VE YÖNTEM Hastalardan, bilgisayarlı tomografi cihazı aracıyla 5 mm'lik kesitler alındı. Volüm tanımlama işlemi yapıldıktan sonra XiO (CMS-USA) 3D tedavi planlama bilgisayarında her hasta için 4, 5, 6 ve 7 alan 18MV X ışınları ile konformal tedavi planları yapıldı. BULGULAR Rektum için en iyi korumanın 5 alanlı konformal radyoterapi tekniğinde yapılabildiği saptandı. (Rektum için: 5 alan, %25'i 59.90±6.8 Gy; 4 alan, %25'i 62.30±10.3 Gy; 6 alan, %25'i 69.36±5.7 Gy; 7 alan %25'i 61.32±7.3 Gy). SONUÇ Bütün tekniklerde PTV, CTV için uygun doz homojenitesi sağlanırken, 4 alanlı konformal radyoterapi tekniğinde femur dozlarının diğer tekniklere göre daha düşük olduğu görüldü. Rektum için en iyi korumanın 5 alanlı konformal radyoterapi tekniğinde yapılabildiğini saptadık.

Anahtar Kelimeler

• Doz-volüm histogramı, konformal radyoterapi, prostat kanseri, tedavi planlama

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