title: Patient QA systems for rotational radiation therapy: a comparative experimental study with intentional errors.
abstract: OBJECTIVE
  The purpose of the present study was to investigate the ability of commercial patient quality assurance (QA) systems to detect linear accelerator-related errors.
  
  
  METHODS
  Four measuring systems (Delta(4®), OCTAVIUS(®), COMPASS, and Epiqa™) designed for patient specific quality assurance for rotational radiation therapy were compared by measuring four clinical rotational intensity modulated radiation therapy plans as well as plans with introduced intentional errors. The intentional errors included increasing the number of monitor units, widening of the MLC banks, and rotation of the collimator. The measurements were analyzed using the inherent gamma evaluation with 2% and 2 mm criteria and 3% and 3 mm criteria. When applicable, the plans with intentional errors were compared with the original plans both by 3D gamma evaluation and by inspecting the dose volume histograms produced by the systems.
  
  
  RESULTS
  There was considerable variation in the type of errors that the various systems detected; the failure rate for the plans with errors varied between 0% and 72%. When using 2% and 2 mm criteria and 95% as a pass rate the Delta(4®) detected 15 of 20 errors, OCTAVIUS(®) detected 8 of 20 errors, COMPASS detected 8 of 20 errors, and Epiqa™ detected 20 of 20 errors. It was also found that the calibration and measuring procedure could benefit from improvements for some of the patient QA systems.
  
  
  CONCLUSIONS
  The various systems can detect various errors and the sensitivity to the introduced errors depends on the plan. There was poor correlation between the gamma evaluation pass rates of the QA procedures and the deviations observed in the dose volume histograms.
authors: Department of Radiation Oncology, Radiation Medicine Research Center, Copenhagen, Denmark. per.munck@rh.regionh.dk
authors: Anna
authors: A
authors: Fredh
authors: Jonas Bengtsson
authors: JB
authors: Scherman
authors: Lotte S
authors: LS
authors: Fog
authors: Per
authors: P
authors: Munck af Rosenschöld
mesh_terms: D006801:Humans; D008297:Male; D009369:Neoplasms / Q000532:radiotherapy; D010315:Particle Accelerators; D011786:Quality Control; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061106:Radiotherapy Setup Errors / Q000517:prevention & control*; D050397:Radiotherapy, Intensity-Modulated / Q000295:instrumentation / Q000379:methods*; D012399:Rotation