title: Image Quality in Oncologic Chest Computerized Tomography With Iterative Reconstruction: A Phantom Study.
abstract: OBJECTIVE
  The purpose of this study was to validate iterative reconstruction technique in oncologic chest computed tomography (CT).
  
  
  METHODS
  An anthropomorphic thorax phantom with 4 simulated tumors was scanned on a 64-slice CT scanner with 2 different iterative reconstruction techniques: one model based (MBIR) and one hybrid (ASiR). Dose levels of 14.9, 11.1, 6.7, and 0.6 mGy were used, and all images were reconstructed with filtered back projection (FBP) and both iterative reconstruction algorithms. Hounsfield units (HU) and absolute noise were measured in the tumors, lung, heart, diaphragm, and muscle. Contrast-to-noise ratios (CNRs) and signal-to-noise ratios (SNRs) were calculated.
  
  
  RESULTS
  Model-based iterative reconstruction (MBIR) increased CNRs of the tumors (21.1-192.2) and SNRs in the lung (-49.0-165.6) and heart (3.1-8.5) at all dose levels compared with FBP (CNR, 1.1-23.0; SNR, -7.5-31.6 and 0.2-1.1) and with adaptive statistical iterative reconstruction (CNR, 1.2-33.2; SNR, -7.3-37.7 and 0.2-1.5). At the lowest dose level (0.6 mGy), MBIR reduced the cupping artifact (HU range: 17.0 HU compared with 31.4-32.2). An HU shift in the negative direction was seen with MBIR.
  
  
  CONCLUSIONS
  Quantitative image quality parameters in oncologic chest CT are improved with MBIR compared with FBP and simpler iterative reconstruction algorithms. Artifacts at low doses are reduced. A shift in HU values was shown; thus, absolute HU values should be used with care.
authors.affiliation: From the *Intervention Centre, Rikshospitalet, Nydalen; †Institute of Physics, University of Oslo; ‡Department of Radiology and Nuclear Medicine, Rikshospitalet, Nydalen, Oslo, Norway; §Department of Medical Radiation Physics, Lund University, Skåne University Hospital, Malmö, Sweden; and ∥Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
authors.forename: Kristin
authors.initials: K
authors.lastname: Jensen
authors.forename: Trond Mogens
authors.initials: TM
authors.lastname: Aaløkken
authors.forename: Anders
authors.initials: A
authors.lastname: Tingberg
authors.forename: Erik
authors.initials: E
authors.lastname: Fosse
authors.forename: Anne Catrine T
authors.initials: AC
authors.lastname: Martinsen
mesh_terms: D000465:Algorithms; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D011856:Radiographic Image Enhancement; D011857:Radiographic Image Interpretation, Computer-Assisted; D013902:Radiography, Thoracic / Q000295:instrumentation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000295:instrumentation