Dose profile evaluation for two fields of a 6 MV LINAC X-ray beam

Abstract

Radiotherapy is an established method of cancer treatment and is widely applied to control this disease. Medical Linear Accelerators (LINAC) is widely used in modern radiotherapy due to their flexibility and high therapeutic reliability. Traditionally, national and international codes of conduct provide guidelines on dosimetry with a reference field of 10x10 cm², considering that for larger fields, dosimetric parameters are well-defined and can be accurately measured. In this work, a LINAC X-ray beam of 6 MV was used to irradiate a solid water phantom, using fields of 10x10 and 5x5 cm². X-ray beam was generated in a 6MV linear accelerator (Linac) model Synergy Platform from the manufacturer Elektra. Radiochromic film sheets were used to record dose profiles inside the solid water phantom. For irradiation of the phantom loaded with the film, it was positioned twice 1.0 m away from the focus of the X-ray beam for both field sizes. In the first irradiation, the phantom was exposed laterally to obtain the longitudinal dose variation profile and in the second irradiation, the phantom was irradiated frontally. The longitudinal profile of the absorbed dose obtained showed the maximum dose value at 1.30 cm depth for both fields. Axial dose profiles were recorded at 1 cm depth and showed a plateau in the axis Y for both fields. The plateau for the field of 10x10 cm² in axis X presented a depression in the central area and that did not happen in the 5x5 cm² field.