title: Estimation of Observer Performance for Reduced Radiation Dose Levels in CT: Eliminating Reduced Dose Levels That Are Too Low Is the First Step.
abstract: This study aims to estimate observer performance for a range of dose levels for common computed tomography (CT) examinations (detection of liver metastases or pulmonary nodules, and cause of neurologic deficit) to prioritize noninferior dose levels for further analysis.
  
  
  
  Using CT data from 131 examinations (abdominal CT, 44; chest CT, 44; head CT, 43), CT images corresponding to 4%-100% of the routine clinical dose were reconstructed with filtered back projection or iterative reconstruction. Radiologists evaluated CT images, marking specified targets, providing confidence scores, and grading image quality. Noninferiority was assessed using reference standards, reader agreement rules, and jackknife alternative free-response receiver operating characteristic figures of merit. Reader agreement required that a majority of readers at lower dose identify target lesions seen by the majority of readers at routine dose.
  
  
  
  Reader agreement identified dose levels lower than 50% and 4% to have inadequate performance for detection of hepatic metastases and pulmonary nodules, respectively, but could not exclude any low dose levels for head CT. Estimated differences in jackknife alternative free-response receiver operating characteristic figures of merit between routine and lower dose configurations found that only the lowest dose configurations tested (ie, 30%, 4%, and 10% of routine dose levels for abdominal, chest, and head CT examinations, respectively) did not meet criteria for noninferiority. At lower doses, subjective image quality declined before observer performance. Iterative reconstruction was only beneficial when filtered back projection did not result in noninferior performance.
  
  
  
  Opportunity exists for substantial radiation dose reduction using existing CT technology for common diagnostic tasks.
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905. Electronic address: fletcher.joel@mayo.edu.
authors.forename: Joel G
authors.initials: JG
authors.lastname: Fletcher
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905.
authors.forename: Lifeng
authors.initials: L
authors.lastname: Yu
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905.
authors.forename: Jeff L
authors.initials: JL
authors.lastname: Fidler
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905.
authors.forename: David L
authors.initials: DL
authors.lastname: Levin
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905.
authors.forename: David R
authors.initials: DR
authors.lastname: DeLone
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905.
authors.forename: David M
authors.initials: DM
authors.lastname: Hough
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905.
authors.forename: Naoki
authors.initials: N
authors.lastname: Takahashi
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905.
authors.forename: Sudhakar K
authors.initials: SK
authors.lastname: Venkatesh
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905.
authors.forename: Anne-Marie G
authors.initials: AG
authors.lastname: Sykes
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905.
authors.forename: Darin
authors.initials: D
authors.lastname: White
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905.
authors.forename: Rebecca M
authors.initials: RM
authors.lastname: Lindell
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905.
authors.forename: Amy L
authors.initials: AL
authors.lastname: Kotsenas
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905.
authors.forename: Norbert G
authors.initials: NG
authors.lastname: Campeau
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905.
authors.forename: Vance T
authors.initials: VT
authors.lastname: Lehman
authors.affiliation: Department of Health Sciences Research, Mayo Clinic, Rochester, Minnesota.
authors.forename: Adam C
authors.initials: AC
authors.lastname: Bartley
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905.
authors.forename: Shuai
authors.initials: S
authors.lastname: Leng
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota.
authors.forename: David R
authors.initials: DR
authors.lastname: Holmes
authors.affiliation: Biostatistics Consulting, LLC, Kensington, Maryland.
authors.forename: Alicia Y
authors.initials: AY
authors.lastname: Toledano
authors.affiliation: Department of Health Sciences Research, Mayo Clinic, Rochester, Minnesota.
authors.forename: Rickey E
authors.initials: RE
authors.lastname: Carter
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905.
authors.forename: Cynthia H
authors.initials: CH
authors.lastname: McCollough
mesh_terms: D005260:Female; D006801:Humans; D008113:Liver Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D055613:Multiple Pulmonary Nodules / Q000000981:diagnostic imaging*; D015588:Observer Variation; D012372:ROC Curve; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: CT; iterative reconstruction; observer performance; radiation dose; radiation dose reduction