Thesis (M.Sc.)--Chulalongkorn University, 2013

The purpose of this study is to verify dosimetric accuracy of Electron Monte Carlo (eMC) algorithm in Eclipse treatment planning for small field electron beams by comparing eMC calculations and measurements of percentage depth doses, beam profile, output factor and isodose distributions for 6, 12 and 20 MeV with small cutout size combinations. Measurements were made using EDR2 film and diode detector–EFD10025. All comparisons of percentage depth doses, beam profile, output factor, isodose distribution matched well within tolerance of 2% and 2 mm, gamma pass were greater than 93% for all of tested energies in the case of square field sizes cutout from 3x3 to 10x10 cm^2. However, The 1x1 and 2x2 cm^2 cutout presented the worst results of running-out the tolerance, gamma pass were below 90%. The comparison of percentage depth dose, output factors and dose distribution for irregular shape of one dimension of the shape field which was equal to small square fields were not significantly different with standard shape (less than 2%). Our results indicated that the eMC algorithm can accurately predict percentage depth doses, beam profiles and output factor for field sizes as small as 3.0 cm diameter for energies in the 6, 12 and 20 MeV. The Monte Carlo algorithm for electron planning in Eclipse is more accurate than previous algorithms for small field sizes in homogenous media