PMID: 2120560Jul 1, 1990Paper

Small-field electron dosimetry for the Philips SL25 linear accelerator

Medical Physics
H RashidJ Y Ting

Abstract

Electron-beam characteristics of a Philips SL25 linear accelerator have been studied. Central-axis percentage depth doses, cross-beam profiles and beam output factors of 6-, 10-, and 20-MeV beams, selected from the available energy range of 4 to 22 MeV, are reported in this paper. The main thrust of this work is to determine the systematic variation of beam characteristics, especially the output factor, with standard cone sizes and cerrobend beam-shaping cutouts down to a field size of 2 X 2 cm Output factors for the standard cones (open field) are energy dependent in a complex manner, increasing with the cone size for the 6-MeV beam whereas decreasing for 10- and 20-MeV beams. The output factor falls below unity at lower energies (6 and 10 MeV) for fields with at least one side smaller than 6 cm, and stays nearly constant for the 20-MeV beam. Measured output factors of small fields are least squares fitted by a second-order polynomial function. Output factors for small rectangular fields have been derived from the one-dimensional and square-root formulas, and the equivalent-square method. Only the one-dimensional formula predicts the measured output factors of highly elongated fields to within +/- 1% experimental uncertainties...Continue Reading

Citations

Nov 7, 2016·International Journal of Radiation Oncology, Biology, Physics·Emil SchülerPeter G Maxim
Feb 14, 2015·Journal of Applied Clinical Medical Physics·Cristina Di VenanzioMaria Pimpinella
Jun 23, 2006·Physics in Medicine and Biology·Kenneth R Hogstrom, Peter R Almond
Jun 8, 2006·Physics in Medicine and Biology·E TynerB McClean
Dec 30, 1998·Physics in Medicine and Biology·A KapurA L Boyer

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