title: Ultralow dose dentomaxillofacial CT imaging and iterative reconstruction techniques: variability of Hounsfield units and contrast-to-noise ratio.
abstract: OBJECTIVE
  The aim of this study was to evaluate whether application of ultralow dose protocols and iterative reconstruction technology (IRT) influence quantitative Hounsfield units (HUs) and contrast-to-noise ratio (CNR) in dentomaxillofacial CT imaging.
  
  
  METHODS
  A phantom with inserts of five types of materials was scanned using protocols for (a) a clinical reference for navigated surgery (CT dose index volume 36.58 mGy), (b) low-dose sinus imaging (18.28 mGy) and (c) four ultralow dose imaging (4.14, 2.63, 0.99 and 0.53 mGy). All images were reconstructed using: (i) filtered back projection (FBP); (ii) IRT: adaptive statistical iterative reconstruction-50 (ASIR-50), ASIR-100 and model-based iterative reconstruction (MBIR); and (iii) standard (std) and bone kernel. Mean HU, CNR and average HU error after recalibration were determined. Each combination of protocols was compared using Friedman analysis of variance, followed by Dunn's multiple comparison test.
  
  
  RESULTS
  Pearson's sample correlation coefficients were all >0.99. Ultralow dose protocols using FBP showed errors of up to 273 HU. Std kernels had less HU variability than bone kernels. MBIR reduced the error value for the lowest dose protocol to 138 HU and retained the highest relative CNR. ASIR could not demonstrate significant advantages over FBP.
  
  
  CONCLUSIONS
  Considering a potential dose reduction as low as 1.5% of a std protocol, ultralow dose protocols and IRT should be further tested for clinical dentomaxillofacial CT imaging.
  
  
  CONCLUSIONS
  HU as a surrogate for bone density may vary significantly in CT ultralow dose imaging. However, use of std kernels and MBIR technology reduce HU error values and may retain the highest CNR.
authors: 1 Department of Radiology, Innsbruck Medical University, Innsbruck, Austria.
authors: Gerlig
authors: G
authors: Widmann
authors: 2 Department of Craniomaxillofacial Surgery, Innsbruck Medical University, Innsbruck, Austria.
authors: Alexander
authors: A
authors: Bischel
authors: 3 OMFS-IMPATH Research Group, Department of Imaging & Pathology, University Leuven and Department of Oral and Maxillofacial Surgery, University Hospitals Leuven, Leuven, Belgium.
authors: Andreas
authors: A
authors: Stratis
authors: 3 OMFS-IMPATH Research Group, Department of Imaging & Pathology, University Leuven and Department of Oral and Maxillofacial Surgery, University Hospitals Leuven, Leuven, Belgium.
authors: Apoorv
authors: A
authors: Kakar
authors: 3 OMFS-IMPATH Research Group, Department of Imaging & Pathology, University Leuven and Department of Oral and Maxillofacial Surgery, University Hospitals Leuven, Leuven, Belgium.
authors: Hilde
authors: H
authors: Bosmans
authors: 3 OMFS-IMPATH Research Group, Department of Imaging & Pathology, University Leuven and Department of Oral and Maxillofacial Surgery, University Hospitals Leuven, Leuven, Belgium.
authors: Reinhilde
authors: R
authors: Jacobs
authors: 1 Department of Radiology, Innsbruck Medical University, Innsbruck, Austria.
authors: Eva-Maria
authors: EM
authors: Gassner
authors: 2 Department of Craniomaxillofacial Surgery, Innsbruck Medical University, Innsbruck, Austria.
authors: Wolfgang
authors: W
authors: Puelacher
authors: 3 OMFS-IMPATH Research Group, Department of Imaging & Pathology, University Leuven and Department of Oral and Maxillofacial Surgery, University Hospitals Leuven, Leuven, Belgium.|4 Department of Radiology, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand.
authors: Ruben
authors: R
authors: Pauwels
mesh_terms: D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D061330:Multidetector Computed Tomography / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D059629:Signal-To-Noise Ratio