title: Spatial and contrast resolution of ultralow dose dentomaxillofacial CT imaging using iterative reconstruction technology.
abstract: OBJECTIVE
  The objective of this study was to determine how iterative reconstruction technology (IRT) influences contrast and spatial resolution in ultralow-dose dentomaxillofacial CT imaging.
  
  
  METHODS
  A polymethyl methacrylate phantom with various inserts was scanned using a reference protocol (RP) at CT dose index volume 36.56 mGy, a sinus protocol at 18.28 mGy and ultralow-dose protocols (LD) at 4.17 mGy, 2.36 mGy, 0.99 mGy and 0.53 mGy. All data sets were reconstructed using filtered back projection (FBP) and the following IRTs: adaptive statistical iterative reconstructions (ASIRs) (ASIR-50, ASIR-100) and model-based iterative reconstruction (MBIR). Inserts containing line-pair patterns and contrast detail patterns for three different materials were scored by three observers. Observer agreement was analyzed using Cohen's kappa and difference in performance between the protocols and reconstruction was analyzed with Dunn's test at α = 0.05.
  
  
  RESULTS
  Interobserver agreement was acceptable with a mean kappa value of 0.59. Compared with the RP using FBP, similar scores were achieved at 2.36 mGy using MBIR. MIBR reconstructions showed the highest noise suppression as well as good contrast even at the lowest doses. Overall, ASIR reconstructions did not outperform FBP.
  
  
  CONCLUSIONS
  LD and MBIR at a dose reduction of >90% may show no significant differences in spatial and contrast resolution compared with an RP and FBP. Ultralow-dose CT and IRT should be further explored in clinical studies.
authors.affiliation: 1 Department of Radiology, Innsbruck Medical University, Innsbruck, Austria.
authors.forename: Gerlig
authors.identifier: http://orcid.org/0000-0002-7255-0672
authors.initials: G
authors.lastname: Widmann
authors.affiliation: 2 Department of Craniomaxillofacial Surgery, Innsbruck Medical University, Innsbruck, Austria.
authors.forename: Alexander
authors.initials: A
authors.lastname: Bischel
authors.affiliation: 3 Department of Imaging and Pathology, OMFS-IMPATH Research Group, KU Leuven-Group Biomedical Sciences Oral and Maxillofacial Surgery-UZ Leuven, Leuven, Belgium.
authors.forename: Andreas
authors.initials: A
authors.lastname: Stratis
authors.affiliation: 3 Department of Imaging and Pathology, OMFS-IMPATH Research Group, KU Leuven-Group Biomedical Sciences Oral and Maxillofacial Surgery-UZ Leuven, Leuven, Belgium.
authors.forename: Hilde
authors.initials: H
authors.lastname: Bosmans
authors.affiliation: 3 Department of Imaging and Pathology, OMFS-IMPATH Research Group, KU Leuven-Group Biomedical Sciences Oral and Maxillofacial Surgery-UZ Leuven, Leuven, Belgium.
authors.forename: Reinhilde
authors.initials: R
authors.lastname: Jacobs
authors.affiliation: 1 Department of Radiology, Innsbruck Medical University, Innsbruck, Austria.
authors.forename: Eva-Maria
authors.initials: EM
authors.lastname: Gassner
authors.affiliation: 2 Department of Craniomaxillofacial Surgery, Innsbruck Medical University, Innsbruck, Austria.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Puelacher
authors.affiliation: 3 Department of Imaging and Pathology, OMFS-IMPATH Research Group, KU Leuven-Group Biomedical Sciences Oral and Maxillofacial Surgery-UZ Leuven, Leuven, Belgium.|4 Department of Radiology, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand.
authors.forename: Ruben
authors.initials: R
authors.lastname: Pauwels
mesh_terms: D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D011861:Radiography, Dental / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: CT; contrast resolution; iterative reconstruction technology; spatial resolution; ultralow dose