Radyoterapide kullanılan baş yastığının dozimetrik etkisinin farklı algoritmalarla incelenmesi

Öz

GİRİŞ ve AMAÇ: Radyoterapide immobilizasyon cihazlarının kullanılması hastanın doğru pozisyon alması ve tedavinin doğru uygulanması için zorunludur. Tedavi sırasında hastanın hareketini kısıtlamak ve rahat bir şekilde yatışını sağlamak için baş yastıkları sıklıkla kullanılmaktadır. Bu çalışmanın amacı, iki farklı algoritma kullanarak baş yastığını vücut konturuna dahil ederek baş yastığının doz dağılımı üzerindeki etkisini incelemektir. YÖNTEM ve GEREÇLER: Elde edilen sonuçlar gama analizi yöntemi ile karşılaştırıldı. Yedi hasta görüntüsündeki vücut konturları, baş yastıklı ve baş yastıksız olarak şekillendirildi. Baş yastığının vücut konturuna dahil edilip çıkarıldığı durumlarda hem Collapse Cone (CC) hem de Monte Carlo (MC) algoritmaları kullanılarak her hasta için vücut içindeki doz dağılımı hesaplandı. BULGULAR: Sonuçlardan da anlaşılacağı gibi, koltuk başlığı doz dağılımı üzerinde bir miktar etkiye sahiptir. Spesifik olarak, gama analizinin sonuçları, baş yastığı vücut konturuna dahil edildiğinde hastaya ulaşan dozların bir miktar azaldığını göstermektedir. CC algoritması, düşük yoğunluklu bir ortamda ikincil fotonların ve saçılan radyasyonun yeterince doğru hesaplanmasına izin vermediğinden, CC algoritmasının benzerlik sonuçları gama analizinde MC algoritmasına göre daha yüksektir TARTIŞMA ve SONUÇ: Hastaya ulaşan radyasyon dozunun doğru bir şekilde hesaplanabilmesi için tedavi sırasında radyasyonun geçtiği tüm materyaller bir tedavi planlama sisteminde belirtilmelidir. Radyoterapide kullanılan immobilizasyon cihazlarının düşük yoğunluklu materyalden oluşsa bile hasta içindeki doz dağılımı üzerinde bir miktar etkilerinin olduğu ve tedavi planlama sistemine dahil edilmesi gerektiği sonucuna varılmıştır.

Anahtar Kelimeler

• Radyoterapi
• immobilizasyon cihazları
• baş yastığı
• tedavi planlama sistemi.

Examination of the dosimetric effects of the headrest used in radiotherapy by different algorithms

Abstract

INTRODUCTION: The use of immobilization devices is imperative in radiotherapy to ensure proper positioning of the patient and correct application of the treatment. Headrests are frequently used to restrict the movement of a patient and to provide comfortable laying during the treatment. The aim of the present study was to examine the effect of a headrest on dose distribution by including the headrest in the body structure using two different algorithms. METHODS: The body structures on seven patient images were contoured with and without headrest. Dose distribution within the body was calculated for each patient using both Collapse Cone (CC) and Monte Carlo (MC) algorithms for cases where the headrest was included in the body structure and removed. RESULTS: the headrest has some effect on the dose distribution. Specifically, the results of the gamma analysis indicate that when the headrest was included in the body structure doses to the body were somewhat reduced. Since the CC algorithm does not allow calculation of secondary photons and scattered radiation sufficiently accurate in a low density environment, the similarity results of the CC algorithm were higher in the gamma analysis than those of the MC algorithm. DISCUSSION AND CONCLUSION: In order to accurately calculate the radiation dose, all the materials through which the radiation passes during the treatment must be specified in a treatment planning system. It is concluded that even if the immobilization devices are of low-density material, they have some effect on the dose distribution within a patient and should be included in the treatment planning system.

Keywords

• Radiotherapy
• immobilization devices
• headrest
• treatment planning system.

Kaynakça

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