Nazofarenks Kanseri Radyoterapi Tedavisinde Hibrit Tedavi Planının TLD ile Dozimetrik Doğrulanması

Year 2019, , 395 - 401, 30.11.2019

Gamze Boz Murat Okutan , Bayram Demir

https://doi.org/10.29233/sdufeffd.631975

Abstract

Nazofarenks kanserinde geleneksel tedavi planlama, günümüzde
yerini optimizasyon tekniklerinin kullanıldığı tersten planlamaya Yoğunluk
Ayarlı Radyoterapi – Yoğunluk Ayarlı Arc Terapi (IMRT-IMAT) ve ikisinin
birlikte kullanıldığı Hibrit tedavi planlamalara bırakmıştır. Özellikle IMAT veya IMRT tedavi planlarında
düşürülemeyen kritik organ dozları veya iyi kapsanamayan PTV hacimleri için
Hibrit planlara ihtiyaç duyulmaktadır.  Bu karmaşık hesaplamaları yapan Tedavi Planlama
Sistemlerinin (TPS) doz hesaplarının dozimetrik yöntemlerle doğrulanması gerekmektedir.
Bu çalışmada Termolüminesans dozimetre (TLD) yöntemi ile TPS doğruluğu test
edilmiştir. Alderson® Rando Fantom’un nazofarenks kanseri tedavi planlaması
için tedavi şartlarında bilgisayarlı tomografi görüntüleri çekilmiştir. Planlanan
Hedef Hacim 70 Gy (PTV70) ve kritik organlar (sağ parotis, sol parotis, medulla
ve beyin sapı) tespit edilirken standart bir nazofarenks tümörlü hastanın
Bilgisayarlı tomografi kesitlerinden füzyon yapılarak yararlanılmıştır. IMRT,
IMAT ve Hibrit tedavi planları Eclipse (version 8.9.17) TPS kullanılarak fantom
üzerinde aynı doz reçetesi ile oluşturulmuştur. Alderson® Rando Fantomda sağ ve
sol parotise, medulla spinalise ve beyin sapına denk gelecek şekilde yerleştirilen
TLD’lerin okuma değerleri toplam doza dönüştürülerek tedavi planlama
bilgisayarındaki doz değerleriyle karşılaştırılmıştır. Eclipse TPS ile TLD
ortalama okuma değerleri arasında en fazla fark IMRT planında Sol Parotiste % 3.5,
IMAT planında Beyin Sapında % 2.78, Hibrit planda Beyin Sapında % 3.16 olarak
bulunmuştur. Bu çalışma ile Nazofarenks için yapılan Hibrit tedavi planının TPS
de doğruluğunun % 4 ten az olduğunu dozimetrik olarak tespit ettik.

Keywords

Nazofarenks, Eclips TPS, Hibrit plan, TLD

Supporting Institution

İstanbul Üniversitesi

Project Number

BAP Proje ID: 23057

Thanks

Bu çalışma, "Radyasyon Onkolojisinde Tümör Kontrol Oranlarının Artırılması ve Volümetrik Ark Tedavilerinin Radyasyon Onkolojisinde Yan Etkilerinin Azaltılması" isimli İstanbul Üniversitesi BAP projesi kapsamında güncellenmiş TPS (Eclipse 15.1) versiyonuyla gerçekleştirilmiştir (Proje ID: 23057).

Dosimetric Verification of Hybrid Treatment Plan by TLD in the Treatment of Nasopharyngeal Cancer Radiotherapy

Abstract

Traditional
treatment planning in nasopharyngeal cancer is now replaced by reverse planning
using optimization techniques Intensity Modulated Radiotherapy-Intensity Modulated
Arc Therapy (IMRT-IMAT) and Hybrid therapy planning using both. Hybrid plans are needed especially for critical
organ doses that cannot be reduced in IMAT or IMRT treatment plans, or for PTV
volumes that are not well covered. The dose calculations of the Treatment Planning Systems (TPS) that make
these complex calculations need to be verified by dosimetric methods. In this study, TPS accuracy was tested by Thermoluminescence
dosimeter (TLD). Computed tomography images of the Alderson® Rando Phantom for treatment
planning in nasopharyngeal cancer were scanned. Planned Target Volume 70 Gy (PTV70) and critical
organs (right parotid, left parotid, medulla and brain stem) were detected
while computed tomography sections of a standard nasopharyngeal tumor patient
were utilized by fusion. IMRT, IMAT and Hybrid treatment plans were created with the same dose
prescription on the phantom using Eclipse (version 8.9.17) TPS. In Alderson® Rando Phantom, TLDs placed in the
right and left parotid, medulla spinalis and brain stem were converted to
cumulative doses and compared with the dose values on the treatment planning
computer. The highest
difference between Eclipse TPS and TLD mean reading values was found to be 3.5 %
in the left parotid IMRT plan, 2.78 % in the brain stem in the IMAT plan and
3.16 % in the brain stem in the hybrid plan. In this study, we determined dosimetric accuracy
of the Hybrid treatment plan for nasopharynx is less than 4 % in TPS.

Keywords

Nasopharynx, Eclipse TPS, Hybrid Plan, TLD

Project Number

BAP Proje ID: 23057

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