Journal of Medical Physics
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ORIGINAL ARTICLE
Year : 2010  |  Volume : 35  |  Issue : 2  |  Page : 65-72

Analytical correction of an extension of the "MU Fraction Approximation" for Varian enhanced dynamic wedges


1 Tri-State Regional Cancer Center, Medical Physics Section, 706 23rd Street, Ashland, Kentucky 41101, USA
2 Parkview Comprehensive Cancer Center, Radiation Oncology Department, 11141, Parkview Plaza Drive, Fort Wayne, Indiana 46845, USA

Correspondence Address:
Michael S Gossman
Tri-State Regional Cancer Center, Medical Physics Section, 706 23rd Street, Ashland, Kentucky - 411 01
USA
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0971-6203.62195

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The most common method to determine enhanced dynamic wedge factors begins with the use of segmented treatment tables. These segmental dose delivery values set as a function of upper jaw position are the backbone of a calculation process coined the "MU Fraction Approximation." Analytical and theoretical attempts have been made to extend and alter the mathematics for this approximation for greater accuracy. A set of linear equations in the form of a matrix are introduced here which correct one published extension of the MU Fraction Approximation as it applies to both symmetric and asymmetric photon fields. The matrix results are compared to data collected from a commissioned Varian Eclipse Treatment Planning System and previously published research for Varian linear accelerators. A total enhanced dynamic wedge factor with excellent accuracy was achieved in comparison to the most accurate previous research found. The deviation seen here is only 0.4% and 1.0% for symmetric and asymmetric fields respectively, for both 6MV and 18MV photon beams.


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