Abstract: Objective To study the correction of algorithm for Varian enhanced dynamic wedge(EDW) factors and compare the
dose/monitor unit (MU) deviation measured at the central axis of EDW field with that obtained by manual calculation or using
the treatment planning system. Methods EDW factors and dose were measured with Thimble ion chamber at 10 cm depth
under the water for 6 MV and 10 MV photon on Varian linear accelerator. The corresponding calculations were done with the
radiation treatment planning system. An analytic formula, namely the“MU Fraction model”, was used to calculate the EDW
factor, which was corrected with a constant factor. The MU of conventional 2-D planning derived from manual calculating,
treatment planning system, and actual measurements were compared. Results With the measured results as the standard, the
corrected manual calculation deviation of EDW factors was significantly reduced. For photon 6 MV, the maximum deviation
reduced from 4.2% to 1.3% for 60° symmetry fields was, and from -4.7% to -1.8% for asymmetric fields. For photon 10 MV, the
maximum deviation for all EDW fields was reduced from -3.0% to 1.1%. Comparison of the manual calculations with the
measured results showed a MU deviation for symmetric fields within 2%, and more than 5% for some asymmetric fields. The
deviation between the calculations of the treatment planning and the measured results was less than 1.5% . Conclusion
Constant factor correction can effectively reduce the deviation of manual calculation. For MU calculation of EDW field in
conventional 2-D dimensional treatment planning, the corrected results of symmetric fields meet clinical requirements. While
the minimum distance between the field edge and the central axis was less than 4 cm in asymmetric fields, the corresponding
special method, measurement or the treatment planning system should be used to calculate the dose/MU.