title: Dosimetric verification of the anisotropic analytical algorithm for radiotherapy treatment planning.
abstract: OBJECTIVE
  To investigate the accuracy of photon dose calculations performed by the Anisotropic Analytical Algorithm, in homogeneous and inhomogeneous media and in simulated treatment plans.
  
  
  METHODS
  Predicted dose distributions were compared with ionisation chamber and film measurements for a series of increasingly complex situations. Initially, simple and complex fields in a homogeneous medium were studied. The effect of inhomogeneities was investigated using a range of phantoms constructed of water, bone and lung substitute materials. Simulated treatment plans were then produced using a semi-anthropomorphic phantom and the delivered doses compared to the doses predicted by the Anisotropic Analytical Algorithm.
  
  
  RESULTS
  In a homogeneous medium, agreement was found to be within 2% dose or 2mm dta in most instances. In the presence of heterogeneities, agreement was generally to within 2.5%. The simulated treatment plan measurements agreed to within 2.5% or 2mm.
  
  
  CONCLUSIONS
  The accuracy of the algorithm was found to be satisfactory at 6 and 10MV both in homogeneous and inhomogeneous situations and in the simulated treatment plans. The algorithm was more accurate than the Pencil Beam Convolution model, particularly in the presence of low density heterogeneities.
authors.affiliation: Department of Radiotherapy Physics, Weston Park Hospital, Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK. Christopher.Bragg@sth.nhs.uk
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Bragg
authors.forename: John
authors.initials: J
authors.lastname: Conway
mesh_terms: D000465:Algorithms; D016880:Anisotropy; D003198:Computer Simulation; D006801:Humans; D008954:Models, Biological; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*