Dosimetry measurements of radiation fields

摘要

The Study was performed on a high-energy linear accelerator (Elekta Precise), with built-in multileaf collimator (MLC) which produces two nominal photon energies (6MV and 15MV). Dosimetric measurements were carried out using linear accelerator (ElektaPrecise), PTW-UNIDOS Electrometer, a dual (0.125 cc) ion Chamber and Farmer (0.6 cc) ion Chamber, MEPHYSTO Version 7.3, and Therapy Beam Analyzer (MP3-S). Three-dimensional treatment planning (Precise PLAN) was used for calculating dose distribution. Inthis study, the physical properties characterizing high energy photon beams of (6MV and 15MV) that include the central axis percentage depth dose (CADD), beam profile specification, tissue maximum ratio (TMR), surface dose, buildup region and output factor, for different field sizes at different depths, were determined to show the effect of field size and beam energy on the central axis percentage depth dose also to show the effect of field size and depth on beam flatness, beam symmetry, penumbra, TMRand out put factor. Also in this study, the physical properties characterizing high energy photon beams of (6MV and 15MV) were measured and compared with the corresponding published data and calculated data by Precise PLAN (3DTPS).