The Effect of ≤3 mm Geometric Errors on the Percentage Depth Dose (PDD) and Beam Profile (BP) Parameters in Relative Dose Measurements Taken in the Linear Accelerator Device (Linac)

Abstract

The modern linear accelerator (Linak) is a device that produces high-energy X-rays and electron beams for the treatment of cancer patients. The basis of radiation therapy is based on the interaction between substance and radiation. Therefore, the interaction between radiation and matter transforms the science of radiation physics into clinical treatment of cancer. In radiotherapy, the most basic relative evaluations for dosimetric measurements are; It consists of a percentage deep dose (DD%) which shows the variation of the X-ray depending on the depth, and the beam profile (IP) measurements at which the flatness and symmetry of the beam can be calculated at a certain depth. DD% is the ratio of the radiation dose measured at a certain depth to the dose measured at the maximum dose depth. In this study, it is aimed to investigate the effect of ≤ 3 mm geometric error that can be made in beam data measurements on DD% for different field sizes and on IP parameters for different depths. In addition, the effect of geometric error on DD%  and IP parameters for different ion chambers was investigated. The results show that the ≤3 mm geometric error during the measurements has a significant effect especially on DD% parameters and small field symmetry.

Keywords

• Linear accelerator,Radiotherapy,Percentage depth dose,Beam profile

Lineer Hızlandırıcı Cihazında (Linak) Alınan Rölatif Doz Ölçümlerinde ≤ 3 mm Geometrik Hataların Yüzde Derin Doz (%DD) ve Işın Profil (IP) Parametreleri Üzerine Etkisi

Abstract

Modern lineer hızlandırıcı (Linak), kanserli hastaların tedavisi için yüksek enerjili X ışınları ve elektron demetleri üreten bir cihazdır. Radyasyon tedavisinin temeli madde ve radyasyon arasındaki etkileşime dayanır. Bu nedenle, radyasyon ve madde arasındaki etkileşim, radyasyon fiziği bilimini kanserin klinik tedavisine dönüştürür. Radyoterapide, dozimetrik ölçümler için en temel rölatif değerlendirmeler; X- ışınının derinliğe bağlı olarak değişimi gösteren yüzde derin doz (%DD) ve belli bir derinlikte ışının düzgünlüğünü ve simetrisini gösteren ışın profil (IP) ölçümlerden oluşmaktadır. %DD, belli bir derinlikte ölçülen radyasyon dozunun, maksimum doz derinliğinde ölçülen doza bölünmesiyle hesaplanır. Bu çalışmada, lineer hızlandırıcıda hasta öncesi başlangıç ölçümlerinde yapılabilecek ≤ 3 mm geometrik hatanın farklı alan boyutları için %DD ve farklı derinlikteki IP parametreleri üzerindeki etkisini görmek amaçlanmıştır. Ayrıca yapılabilecek geometrik hatanın iyon odası farkına göre değişimi araştırılmıştır. Sonuçlar, ölçümler sırasında yapılabilecek ≤3 mm geometrik hatanın, özellikle yüzde derin doz parametreleri ve küçük alan simetrisi üzerinde etkisinin oldukça fazla olduğunu göstermektedir. 

Keywords

• Lineer hızlandırıcı,Radyoterapi,Yüzde derin doz,Işın profil

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