ENDOMETRİUM KANSERLERİNDE YOĞUNLUK AYARLI RADYOTERAPİ İLE 3 BOYUTLU KONFORMAL RADYOTERAPİNİN DOZİMETRİK OLARAK KARŞILAŞTIRILMASI

Abstract

Endometrium kanserli olgularda 3 boyutlu konformal radyoterapi (3B KRT) ile yoğunluk ayarlı radyoterapinin (YART) doz volüm histogramlarının karşılaştırılması ve YART’ın kalite kontrolünün değerlendirilmesi amaçlanmaktadır. Erken evre endometrium kanserli 15 olgu çal›flmaya dahil edilmifltir. Olgular›n prone pozisyonda bilgisayarları tomografi görüntüleri alınmıştır, ve tedavi planlama sisteminde CTV (klinik tümör volümü), PTV (planlanan tedavi volümü) ve kritik organlar olan ince bağırsak, rektum ve mesane volümleri belirlenmiştir. Her olgu için 3B KRT ve YART tedavi tekniklerine göre planlamalar yapılmış ve doz volüm histogramları karşılaştırmıştır. YART tekniğinin kalite kontrolünde, planlanan ve ölçülen dozları karşılşmak için absolüt dozimetrede iyon odası ve rölatif dozimetrede radyografik x ışını doğrulama filmleri kullanılmıştır. YART’de 3BKRT ile karşılaştırıldığında; rektum, mesane ve ince bağırsak için 45 Gy alan doz volüm yüzdeli¤inde azalma saptanmıştır (sırasıyla; %50, %42, %4, p<0.05). PTV 4500 cGy alacak şekilde planlama yapıldığında, hacmin %95’inin aldığı doz 3B KRT’de 4418 cGy iken YART modelinde 4500 cGy olup, YART modelinde PTV’nin daha homojen sarıldığı gösterilmifltir. YART’ın kalite kontrol değerlendirmesinde hata payları sın›ılar içinde bulunmuş, rölatif dozimetrede ortalama hata %1.088, ve absolüt dozimetrede gamma indeksin (g) £1 oldu¤u saptanmıştır. Sonuç olarak endometrium kanserlerinde YART tedavi tekniğinin, 3B KRT tekniğine göre PTV’de daha homojen doz dağılımı, kritik organ dozlarında daha fazla düşüş sağladığı ve tedavinin yüksek doğrulukta uygulanabileceği gösterilmiştir.

Keywords

• Endometrium kanseri, konformal radyoterapi, yoğunluk ayarlı radyoterapi, doz volüm histogramı, kalite kontrol

Abstract

Our aim is to compare dose-volume histograms of 3D conformal radiotherapy with intensity modulated radiotherapy (IMRT) and to test the quality assurance of IMRT in endometrial cancer patients. Fifteen consecutive patients with early stage endometrial cancer were included in the study. Computed tomography (CT) scans of each patients were obtained in prone position and CTV (clinical target volume), PTV (planning target volume) and organs at risk (bladder, rectum and small intestine) volumes were delineated on treatment planning system. Each patient was planned with 3D conformal radiotherapy (4-field pelvic box) and IMRT and dose-volume histograms of each plan were compared. Calculated and measured doses of IMRT plans were compared for the quality assurance purposes of IMRT using the following 2 methods: 1) ion chamber for absolute dosimetry 2) radiographical X ray film verification for relative dosimetry. IMRT reduced V45 of rectum, bladder and small intestine by (50%, 42%, 4% p<0.05, respectively). Both plans were normalized to deliver 4500 cGy to the PTV and D95 of PTV was 4500 cGy for IMRT and 4418 cGy for 3D CRT and more homogenous dose coverage was achieved with IMRT. Quality assurance tests of IMRT revealed that margin of error was within the limits (mean error was 1.088% for relative dosimetry and gamma index (g) was £1 for absolute dosimetry). In conclusion IMRT provides better PTV coverage and decreases the doses of critical organs and the quality assurance results suggest that IMRT could be performed with high precision.

Keywords

• Endometrial cancer, conformal radiotherapy, intensity modulated radiotherapy, dose volume histogram, quality assurance.

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