title: An analysis of 6-MV versus 18-MV photon energy plans for intensity-modulated radiation therapy (IMRT) of lung cancer.
abstract: OBJECTIVE
  To analyse the supposed benefits of low over high photon energies for the radiotherapy of lung cancer.
  
  
  METHODS
  For 13 patients, 6- and 18-MV IMRT planning was performed using identical planning objectives and dose constraints. Plans were compared according to dose-volume histogram (DVH) analysis including conformity and homogeneity indices (CI and HI) and overall plan quality (composite score CS), considering also magnitude and location of planning target volumes (PTVs).
  
  
  RESULTS
  With 6-MV plans, CSs were better in 11/13, HIs in 10/13 and CIs in 6/13 patients compared with 18-MV plans. Six-MV plans resulted in a better normal tissue sparing except for specified dose levels to the thorax and spinal cord. On average differences between 6 and 18 MV both for the PTV and normal tissues were not statistically significant (p>0.05). Considering size and location of the PTVs as well as their relative position to normal tissue, overall no significant differences between 6 and 18 MV were observed.
  
  
  CONCLUSIONS
  On average no clinically or statistically significant differences between 6- and 18-MV plans were observed. High photon energies should therefore not be excluded a priori when a dose-calculation algorithm is utilized that accurately accounts for heterogeneities.
authors.affiliation: Department of Radiation Oncology, Virginia Commonwealth University, Richmond, VA 23298, USA. eweiss@mcvh-vcu.edu
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Weiss
authors.forename: Jeffrey V
authors.initials: JV
authors.lastname: Siebers
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Keall
mesh_terms: D004307:Dose-Response Relationship, Radiation; D004947:Esophagus / Q000528:radiation effects; D006321:Heart / Q000528:radiation effects; D006801:Humans; D008168:Lung / Q000528:radiation effects; D008175:Lung Neoplasms / Q000532:radiotherapy*; D017785:Photons; D011878:Radiotherapy / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D013116:Spinal Cord / Q000528:radiation effects