Percentage Depth Dose Comparative Study of 6 MV Photon Beam of Both Linear Accelerators Varian Clinac 2100 and Varian Clinac 2300 Using Gamma Index Method and Investigation of the Varian Technology

Abstract

This work presents a comparative study of percentage depth dose (PDD), and especially the build-up region, on 6 MV photon beam in water phantom for Varian linear accelerators: Varian Clinac 2100 and Varian Clinac 2300. The build-up region depends on the photon beam energy, the field size, the incidence angle of the beam, the air gap, and the beam modifier devices. In our study, we have investigated the Varian technology evolution and we have clarified how Varian had optimized the delivered dose in its recent medical linear accelerator technology.

The PDDs were compared for both Varian medical linear accelerators; we have use the relative dose parameter and the gamma index for this comparison study. The measurements were carried out for a field size of 10×10 cm², for both Varian linear accelerators, it is the reference field size for this study, the photon beam energy of 6 MV and source-to-surface distance (SSD) is the 100 cm.

The relative dose was less than 1 and gamma index criterion acceptance was 100% for gamma index < 1,5 beyond the depth of dose maximum(D_max), and the PDD difference was in the build-up region and especially in the shallower depth beneath the surface dose, this difference due to the beam modifier enhancement and the technological development . The recent Varian technology was more developed in the build-up region due to amelioration in the photon beam modifiers, and Varian Clinac 2300 is more recent than Varian Clinac 2100, thus the technology has the focus in the photon beam modifiers.

Our work contributes in dosimetry study of Varian linear accelerator and to make an investigation of Varian technology. The aim of this work was to investigate the Varian technology via a comparative study of PDD distributions, and especially the build-up region, for accelerators Varian Clinac 2300 and Varian Clinac 2100, and to highlight the features of this technological evolution from Varian Clinac 2100 to Varian Clinac 2300.