title: Comparison of action levels for patient-specific quality assurance of intensity modulated radiation therapy and volumetric modulated arc therapy treatments.
abstract: OBJECTIVE
  To perform a comprehensive and systematic comparison of fixed-beam IMRT and volumetric modulated arc therapy (VMAT) patient-specific QA measurements for a common set of geometries using typical measurement methods.
  
  
  METHODS
  Fixed-beam IMRT and VMAT plans were constructed for structure set geometries provided by AAPM Task Group 119. The plans were repeatedly delivered across multiple measurement sessions, and the resulting dose distributions were measured with (1) radiochromic film and ionization chamber and (2) a commercial two-dimensional diode array. The resulting QA measurements from each delivery technique were then analyzed, compared, and tested for statistically significant differences.
  
  
  RESULTS
  Although differences were noted between QA results for some plans, neither modality showed consistently better agreement of measured and planned doses: of the 22 comparisons, IMRT showed better QA results in 11 cases, and VMAT showed better QA results in 11 cases. No statistically significant differences (p < 0.05) between IMRT and VMAT QA results were found for point doses measured with an ionization chamber, planar doses measured with radiochromic film, or planar doses measured with a two-dimensional diode array.
  
  
  CONCLUSIONS
  These results suggest that it is appropriate to apply patient-specific QA action levels derived from fixed-beam IMRT to VMAT.
authors: Department of Physics and Astronomy, Louisiana State University and Agricultural and Mechanical College, Baton Rouge, LA 70803, USA.
authors: Gordon M
authors: GM
authors: Mancuso
authors: Jonas D
authors: JD
authors: Fontenot
authors: John P
authors: JP
authors: Gibbons
authors: Brent C
authors: BC
authors: Parker
mesh_terms: D005373:Film Dosimetry / Q000592:standards*; D006801:Humans; D009369:Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D011785:Quality Assurance, Health Care; D011859:Radiography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods* / Q000592:standards*; D020266:Radiotherapy, Conformal / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity