title: Objective assessment of image quality and dose reduction in CT iterative reconstruction.
abstract: OBJECTIVE
  Iterative reconstruction (IR) algorithms have the potential to reduce radiation dose in CT diagnostic imaging. As these algorithms become available on the market, a standardizable method of quantifying the dose reduction that a particular IR method can achieve would be valuable. Such a method would assist manufacturers in making promotional claims about dose reduction, buyers in comparing different devices, physicists in independently validating the claims, and the United States Food and Drug Administration in regulating the labeling of CT devices. However, the nonlinear nature of commercially available IR algorithms poses challenges to objectively assessing image quality, a necessary step in establishing the amount of dose reduction that a given IR algorithm can achieve without compromising that image quality. This review paper seeks to consolidate information relevant to objectively assessing the quality of CT IR images, and thereby measuring the level of dose reduction that a given IR algorithm can achieve.
  
  
  METHODS
  The authors discuss task-based methods for assessing the quality of CT IR images and evaluating dose reduction.
  
  
  RESULTS
  The authors explain and review recent literature on signal detection and localization tasks in CT IR image quality assessment, the design of an appropriate phantom for these tasks, possible choices of observers (including human and model observers), and methods of evaluating observer performance.
  
  
  CONCLUSIONS
  Standardizing the measurement of dose reduction is a problem of broad interest to the CT community and to public health. A necessary step in the process is the objective assessment of CT image quality, for which various task-based methods may be suitable. This paper attempts to consolidate recent literature that is relevant to the development and implementation of task-based methods for the assessment of CT IR image quality.
authors.affiliation: Diagnostic X-Ray Systems Branch, Office of In Vitro Diagnostic Devices and Radiological Health, Center for Devices and Radiological Health, United States Food and Drug Administration, 10903 New Hampshire Avenue, Silver Spring, Maryland 20993.
authors.forename: J Y
authors.initials: JY
authors.lastname: Vaishnav
authors.affiliation: Diagnostic X-Ray Systems Branch, Office of In Vitro Diagnostic Devices and Radiological Health, Center for Devices and Radiological Health, United States Food and Drug Administration, 10903 New Hampshire Avenue, Silver Spring, Maryland 20993.
authors.forename: W C
authors.initials: WC
authors.lastname: Jung
authors.affiliation: Division of Imaging and Applied Mathematics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, United States Food and Drug Administration, 10903 New Hampshire Avenue, Silver Spring, Maryland 20993.
authors.forename: L M
authors.initials: LM
authors.lastname: Popescu
authors.affiliation: Division of Imaging and Applied Mathematics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, United States Food and Drug Administration, 10903 New Hampshire Avenue, Silver Spring, Maryland 20993.
authors.forename: R
authors.initials: R
authors.lastname: Zeng
authors.affiliation: Division of Imaging and Applied Mathematics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, United States Food and Drug Administration, 10903 New Hampshire Avenue, Silver Spring, Maryland 20993.
authors.forename: K J
authors.initials: KJ
authors.lastname: Myers
mesh_terms: D000465:Algorithms; D006801:Humans; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods* / Q000592:standards