title: Institutional patient-specific IMRT QA does not predict unacceptable plan delivery.
abstract: OBJECTIVE
  To determine whether in-house patient-specific intensity modulated radiation therapy quality assurance (IMRT QA) results predict Imaging and Radiation Oncology Core (IROC)-Houston phantom results.
  
  
  METHODS
  IROC Houston's IMRT head and neck phantoms have been irradiated by numerous institutions as part of clinical trial credentialing. We retrospectively compared these phantom results with those of in-house IMRT QA (following the institution's clinical process) for 855 irradiations performed between 2003 and 2013. The sensitivity and specificity of IMRT QA to detect unacceptable or acceptable plans were determined relative to the IROC Houston phantom results. Additional analyses evaluated specific IMRT QA dosimeters and analysis methods.
  
  
  RESULTS
  IMRT QA universally showed poor sensitivity relative to the head and neck phantom, that is, poor ability to predict a failing IROC Houston phantom result. Depending on how the IMRT QA results were interpreted, overall sensitivity ranged from 2% to 18%. For different IMRT QA methods, sensitivity ranged from 3% to 54%. Although the observed sensitivity was particularly poor at clinical thresholds (eg 3% dose difference or 90% of pixels passing gamma), receiver operator characteristic analysis indicated that no threshold showed good sensitivity and specificity for the devices evaluated.
  
  
  CONCLUSIONS
  IMRT QA is not a reasonable replacement for a credentialing phantom. Moreover, the particularly poor agreement between IMRT QA and the IROC Houston phantoms highlights surprising inconsistency in the QA process.
authors.affiliation: Imaging and Radiation Oncology Core at Houston, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas. Electronic address: sfkry@mdanderson.org.
authors.forename: Stephen F
authors.initials: SF
authors.lastname: Kry
authors.affiliation: Imaging and Radiation Oncology Core at Houston, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Andrea
authors.initials: A
authors.lastname: Molineu
authors.affiliation: Imaging and Radiation Oncology Core at Houston, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas; The University of Texas Health Science Center Houston, Graduate School of Biomedical Sciences, Houston, Texas.
authors.forename: James R
authors.initials: JR
authors.lastname: Kerns
authors.affiliation: Imaging and Radiation Oncology Core at Houston, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas; The University of Texas Health Science Center Houston, Graduate School of Biomedical Sciences, Houston, Texas.
authors.forename: Austin M
authors.initials: AM
authors.lastname: Faught
authors.affiliation: Imaging and Radiation Oncology Core at Houston, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas; The University of Texas Health Science Center Houston, Graduate School of Biomedical Sciences, Houston, Texas.
authors.forename: Jessie Y
authors.initials: JY
authors.lastname: Huang
authors.affiliation: Imaging and Radiation Oncology Core at Houston, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas; The University of Texas Health Science Center Houston, Graduate School of Biomedical Sciences, Houston, Texas.
authors.forename: Kiley B
authors.initials: KB
authors.lastname: Pulliam
authors.affiliation: Imaging and Radiation Oncology Core at Houston, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas; The University of Texas Health Science Center Houston, Graduate School of Biomedical Sciences, Houston, Texas.
authors.forename: Jackie
authors.initials: J
authors.lastname: Tonigan
authors.affiliation: Imaging and Radiation Oncology Core at Houston, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Paola
authors.initials: P
authors.lastname: Alvarez
authors.affiliation: The University of Texas Health Science Center Houston, Graduate School of Biomedical Sciences, Houston, Texas; Department of Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Francesco
authors.initials: F
authors.lastname: Stingo
authors.affiliation: Imaging and Radiation Oncology Core at Houston, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas; The University of Texas Health Science Center Houston, Graduate School of Biomedical Sciences, Houston, Texas.
authors.forename: David S
authors.initials: DS
authors.lastname: Followill
mesh_terms: D003406:Credentialing; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D019047:Phantoms, Imaging / Q000592:standards*; D011785:Quality Assurance, Health Care / Q000592:standards*; D012372:ROC Curve; D011879:Radiotherapy Dosage / Q000592:standards; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation / Q000379:methods / Q000592:standards*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods / Q000592:standards*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity