title: Knowledge-based iterative model reconstruction: comparative image quality and radiation dose with a pediatric computed tomography phantom.
abstract: BACKGROUND
  CT of pediatric phantoms can provide useful guidance to the optimization of knowledge-based iterative reconstruction CT.
  
  
  OBJECTIVE
  To compare radiation dose and image quality of CT images obtained at different radiation doses reconstructed with knowledge-based iterative reconstruction, hybrid iterative reconstruction and filtered back-projection.
  
  
  METHODS
  We scanned a 5-year anthropomorphic phantom at seven levels of radiation. We then reconstructed CT data with knowledge-based iterative reconstruction (iterative model reconstruction [IMR] levels 1, 2 and 3; Philips Healthcare, Andover, MA), hybrid iterative reconstruction (iDose(4), levels 3 and 7; Philips Healthcare, Andover, MA) and filtered back-projection. The noise, signal-to-noise ratio and contrast-to-noise ratio were calculated. We evaluated low-contrast resolutions and detectability by low-contrast targets and subjective and objective spatial resolutions by the line pairs and wire.
  
  
  RESULTS
  With radiation at 100 peak kVp and 100 mAs (3.64 mSv), the relative doses ranged from 5% (0.19 mSv) to 150% (5.46 mSv). Lower noise and higher signal-to-noise, contrast-to-noise and objective spatial resolution were generally achieved in ascending order of filtered back-projection, iDose(4) levels 3 and 7, and IMR levels 1, 2 and 3, at all radiation dose levels. Compared with filtered back-projection at 100% dose, similar noise levels were obtained on IMR level 2 images at 24% dose and iDose(4) level 3 images at 50% dose, respectively. Regarding low-contrast resolution, low-contrast detectability and objective spatial resolution, IMR level 2 images at 24% dose showed comparable image quality with filtered back-projection at 100% dose. Subjective spatial resolution was not greatly affected by reconstruction algorithm.
  
  
  CONCLUSIONS
  Reduced-dose IMR obtained at 0.92 mSv (24%) showed similar image quality to routine-dose filtered back-projection obtained at 3.64 mSv (100%), and half-dose iDose(4) obtained at 1.81 mSv.
authors.affiliation: Department of Radiology, Seoul National University Hospital, 101 Daehak-ro, Jongno-gu, Seoul, 110-744, Korea.|Department of Radiology, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Young Jin
authors.initials: YJ
authors.lastname: Ryu
authors.affiliation: Department of Radiology, Seoul National University Hospital, 101 Daehak-ro, Jongno-gu, Seoul, 110-744, Korea. iater@snu.ac.kr.|Department of Radiology, Seoul National University College of Medicine, Seoul, Korea. iater@snu.ac.kr.
authors.forename: Young Hun
authors.initials: YH
authors.lastname: Choi
authors.affiliation: Department of Radiology, Seoul National University Hospital, 101 Daehak-ro, Jongno-gu, Seoul, 110-744, Korea.|Department of Radiology, Seoul National University College of Medicine, Seoul, Korea.|Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea.
authors.forename: Jung-Eun
authors.initials: JE
authors.lastname: Cheon
authors.affiliation: Dalio Institute of Cardiovascular Imaging, New York-Presbyterian Hospital and the Weill Cornell Medical College, New York, NY, USA.
authors.forename: Seongmin
authors.initials: S
authors.lastname: Ha
authors.affiliation: Department of Radiology, Seoul National University Hospital, 101 Daehak-ro, Jongno-gu, Seoul, 110-744, Korea.|Department of Radiology, Seoul National University College of Medicine, Seoul, Korea.|Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea.
authors.forename: Woo Sun
authors.initials: WS
authors.lastname: Kim
authors.affiliation: Department of Radiology, Seoul National University Hospital, 101 Daehak-ro, Jongno-gu, Seoul, 110-744, Korea.|Department of Radiology, Seoul National University College of Medicine, Seoul, Korea.|Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea.
authors.forename: In-One
authors.initials: IO
authors.lastname: Kim
mesh_terms: D002675:Child, Preschool; D003198:Computer Simulation; D005260:Female; D006801:Humans; D051188:Knowledge Bases; D000069550:Machine Learning; D008297:Male; D015233:Models, Statistical; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D000069079:Radiation Exposure / Q000032:analysis*; D011835:Radiation Protection / Q000379:methods; D011856:Radiographic Image Enhancement / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D014057:Tomography, X-Ray Computed / Q000295:instrumentation* / Q000379:methods*
keywords: Children; Computed tomography; Infants; Iterative model reconstruction; Iterative reconstruction; Knowledge-based iterative reconstruction; Pediatric; Radiation