title: Determination of an Effective Wedge Angle by Combination of Two Arbitrary Universal Wedge Fields in Radiation Therapy of Cancer Patients with Megavoltage Photon Beams.
abstract: BACKGROUND
  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 (15°, 30°, 45°, 60°),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 angles. The isodose curves also are derived for these wedges.
  
  
  METHODS
  we performed the dosimetry of Varian Clinac 2100C/D with Scanditronix Wellhofer water blue phantom, CU500E, OmniPro - Accept software and 0.13cc ionization chamber for 6Mv photon beam in depth of 10cm (reference depth) for universal physical wedges (15°, 30°, 45°, and 60°) and reference field 10x10cm2. 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 3°. 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Medical physics, Golestan Hospital, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran E-mail : Tahmasebi_mj @yahoo.com.
authors.forename: Azin
authors.initials: A
authors.lastname: Shamsi
authors.forename: Mohammad Javad
authors.initials: MJ
authors.lastname: Tahmasebi Birgani
authors.forename: Mohammad Ali
authors.initials: MA
authors.lastname: Behrooz
authors.forename: Sholeh
authors.initials: S
authors.lastname: Arvandi
authors.forename: Jafar
authors.initials: J
authors.lastname: Fatahiasl
authors.forename: Reza
authors.initials: R
authors.lastname: Maskny
authors.forename: Neda
authors.initials: N
authors.lastname: Abdalvand
mesh_terms: D001835:Body Weight / Q000528:radiation effects; D006801:Humans; D009369:Neoplasms / Q000532:radiotherapy*; D010315:Particle Accelerators; D019047:Phantoms, Imaging; D017785:Photons; D010808:Physical Examination / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012984:Software