Abstract
AbstractThe virtual wedge (VW) is done by simultaneously controlling the movement of one of the upper collimator jaws and varying the dose rate during irradiation to deliver a dose profile comparable to that achieved when using a physical wedge (PW). The aims of this thesis are to analyze the clinical physical characteristics of virtual wedge and treatment case reports. The physical characteristics of VW contain VW angles verification, percentage depth doses, and the discrepancies of wedge factors and profiles between PWs and VWs with various field sizes and depths. The results show that the VW angles were stable, and the most central wedge factors were unity, and are independent of source-surface distance (SSD), field size, depth and monitor unit. Percent depth doses for VW were similar to that obtained for open field, and do not have beam hardening, like PW. The peripheral doses from VW were about half of that PW. The treatment planning with VW has more flexible applications than with PW. The VW has practical and dosimetric advantages over PW. The clinical applications of VW are more convenient for treatment setup with various arbitrarily angles so that it is a positive replacement for PW.