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)

Year 2019, , 239 - 247, 30.11.2019

Aysun İnal

https://doi.org/10.29233/sdufeffd.587284

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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