Dosimetric Application of SRT Treatment Plans in Patients with Brain Metastases for IRIS and Mlc-Based Collimators in the CyberKnife System

Abstract

The purpose of this study is to evaluate and compare the quality of the plans made with IRIS collimator and MLC for intracranial treatments performed with Cyberknife. Homogeneity, conformality, gradient index, Monitor Unit and treatment time parameters were used in the evaluation. When creating treatment plans, attention was paid to the fact that % 100 of the prescribed dose enveloped % 95 of the target volume, while ensuring maximum protection of critical organs. Treatment plans were made for the target volumes of 10 cases with brain metastases in different localizations using two different collimators. The dose prescribed in the plans was defined as 18 Gy in 3 fractions. In order to make an accurate comparison, the planning parameters used for IRIS collimator and MLC were kept constant for each case. The prescribed dose was defined as a minimum isodose curve of % 80. There was no statistically significant difference between the two decouples for the values of HI, nCI, GI (p>0.05). CI was lower in plans with IRIS than MLC, and for MU and MLC treatment periods, quite low values were obtained in plans with IRIS collimator and there is a statistically significant difference (p<0.05). The mean MU values were 10399 ± 3017.3 MU, 3166 MU ± 792.7 MU for IRIS and MLC, respectively, and the mean treatment time was 25 ± 7.5 min, 14.5 ± 2.3 for IRIS and MLC, respectively. When the quality of the plan for IRIS collimator and MLC was compared in the treatment of intracranial Cyberknife, it was found that in the plans made with MLC for the duration of treatment and MU, the treatment was completed in a shorter time with less MU value without loss in the quality indices. This, in turn, allows the patient to complete his treatment in less time.

Keywords

• Brain Metastasis
• Stereotactic Radiosurgery
• CyberKnife
• Breast Cancer
• Collimator

CyberKnife Sisteminde IRIS ve MLC Tabanlı Kolimatörler için Beyin Metastazlı Olgularda SRT Tedavi Planlarının Dozimetrik Karşılaştırması

Abstract

Bu çalışmanın amacı; Cyberknife ile gerçekleştirilen intrakranial tedavilerde IRIS kolimatör ve MLC ile yapılan planların kalitelerini değerlendirmek ve karşılaştırmaktır. Değerlendirme yapılırken homojenite, konformalite, gradiyent indeks, Monitör Unit ve tedavi süresi parametreleri kullanıldı. Tedavi planları oluşturulurken kritik organların maksimum derecede korunması sağlanırken reçete edilen dozun %100’ünün, hedef hacmin %95’ini sarmasına dikkat edildi. Beyin metastazlı 10 olgunun, iki farklı kolimatör kullanılarak farklı lokalizasyonlarda bulunan hedef hacimlere yönelik, tedavi planları yapıldı. Planlarda reçete edilen doz 3 fraksiyonda 18 Gy olarak tanımlandı. Doğru bir karşılaştırma yapabilmek için IRIS kolimatör ve MLC için kullanılan planlama parametreleri, her bir olgu için sabit tutuldu. Reçete edilen doz minumum %80’lik izodoz eğrisine tanımlandı. HI, nCI, GI değerleri için iki ayrı planlama arasında istatistiksel anlamlı bir fark bulunmadı (p>0,05). CI, IRIS ile yapılan planlarda MLC’ye göre daha düşük, MU ve tedavi süreleri için ise MLC ile yapılan planlarda IRIS kolimatöre göre oldukça düşük değerler elde edildi ve istatistiksel olarak anlamlı fark vardır (p<0,05). Ortalama MU değerleri sırasıyla IRIS ve MLC için; 10399 ± 3017,3 MU, 3166 MU ± 792,7 MU ve ortalama tedavi süresi sırasıyla IRIS ve MLC için; 25 ± 7,5 dk, 14,5 ± 2,3 idi. İntrakranial Cyberknife tedavisinde IRIS kolimatör ve MLC için plan kalitesi karşılaştırıldığında tedavi süresi ve MU için MLC ile yapılan planlarda kalite indekslerinde kayıp olmadan tedaviyi daha az MU değeri ile daha kısa sürede bitirdiği tespit edilmiştir. Bu da olgunun daha az sürede tedavisini tamamlamasına olanak sağlamaktadır.

Keywords

• Beyin Metastazı
• Stereotaktik Radyocerrahi
• CyberKnife
• Meme Kanseri
• Kolimatör

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