Open AccessBeam focal spot position determination for an Elekta linac with the Agility ® head; practical guide with a ready‐to‐go procedure
Author(s) -
Chojnowski Jacek M.,
Taylor Lee M.,
Sykes Jonathan R.,
Thwaites David I.
Publication year - 2018
Publication title -
journal of applied clinical medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.83
H-Index - 48
ISSN - 1526-9914
DOI - 10.1002/acm2.12344
Subject(s) - linear particle accelerator , isocenter , collimator , offset (computer science) , computer science , optics , beam (structure) , medical physics , imaging phantom , physics , programming language
A novel phantomless, EPID ‐based method of measuring the beam focal spot offset of a linear accelerator was proposed and validated for Varian machines. In this method, one set of jaws and the MLC were utilized to form a symmetric field and then a 180 o collimator rotation was utilized to determine the radiation isocenter defined by the jaws and the MLC , respectively. The difference between these two isocentres is directly correlated with the beam focal spot offset of the linear accelerator. In the current work, the method has been considered for Elekta linacs. An Elekta linac with the Agility ® head does not have two set of jaws, therefore, a modified method is presented making use of one set of diaphragms, the MLC and a full 360 o collimator rotation. The modified method has been tested on two Elekta Synergy ® linacs with Agility ® heads and independently validated. A practical guide with instructions and a MATLAB ® code is attached for easy implementation.