A spreadsheet solution for off-axis, noncentral enhanced dynamic wedge factors

Enhanced dynamic wedges can be very useful in increasing radiation therapy treatment efficiency. A drawback to their use is finding a factor analogous to a conventional wedge factor to calculate the dose to a point in a dynamically wedged field. A formalism has previously been published [J. Gibbons, Med. Phys. 25, 1411-1418 (1998)] to determine this factor at the central point of a dynamically wedged field. This paper expands the use of the previous formalism to show efficacy at any point under a dynamically wedged field, provided the point is not in a penumbra region. Results of measurements taken with four clinically relevant field sizes, both symmetric and asymmetric, are given. These results show acceptable correlation between the original formalism and its expanded use to noncentral points.