Determination of an Effective Wedge Angle by Combination of Two Arbitrary Universal Wedge Fields in Radiation Therapy of Cancer Patients with Megavoltage Photon Beams.

Introduction: Wedge filters are commonly used in radiation oncology for eliminating hot spots and creating a uniform dose distribution in optimizing isodose curves in the target volume for clinical aspects. These are some limited standard physical wedges (۱۵°, ۳۰°, ۴۵°, ۶۰°), or creating an arbitrary wedge angle, like motorized wedge or dynamic wedge, ... The new formulation is presented by the combination of wedge fields for determining an arbitrary effective wedge angle. The isodose curves also are derived for these wedges.   Materials and Methods: we performed the dosimetry of Varian Clinac ۲۱۰۰C/D with Scanditronix Wellhofer water blue phantom, CU۵۰۰E, OmniPro - Accept software and ۰.۱۳cc ionization chamber for ۶Mv photon beam in depth of ۱۰cm (reference depth) for universal physical wedges (۱۵°, ۳۰°, ۴۵°, and ۶۰°) and reference field ۱۰x۱۰cm۲. By combining the isodose curve standard wedge fields with compatible weighting dose for each field, the effective isodose curve is calculated for any wedge angle.   Results: The relation between a given effective wedge angle and the weighting of each combining wedge fields was derived. A good agreement was found between the measured and calculated wedge angles and the maximum deviation did not exceed ۳°. The difference between the measured and calculated data decreased when the combined wedge angles were closer. The results are in agreement with the motorized single wedge appliance in the literature.   Conclusion: This technique showed that the effective wedge angle that is obtained from this method is adequate for clinical applications and the motorized wedge formalism is a special case of this consideration.

کلیدواژه ها:

Universal physical wedge ، Profile ، Megavoltage photon ، Beam ، Radiation Therapy