title: Impact of image denoising on image quality, quantitative parameters and sensitivity of ultra-low-dose volume perfusion CT imaging.
abstract: OBJECTIVE
  To examine the impact of denoising on ultra-low-dose volume perfusion CT (ULD-VPCT) imaging in acute stroke.
  
  
  METHODS
  Simulated ULD-VPCT data sets at 20 % dose rate were generated from perfusion data sets of 20 patients with suspected ischemic stroke acquired at 80 kVp/180 mAs. Four data sets were generated from each ULD-VPCT data set: not-denoised (ND); denoised using spatiotemporal filter (D1); denoised using quanta-stream diffusion technique (D2); combination of both methods (D1 + D2). Signal-to-noise ratio (SNR) was measured in the resulting 100 data sets. Image quality, presence/absence of ischemic lesions, CBV and CBF scores according to a modified ASPECTS score were assessed by two blinded readers.
  
  
  RESULTS
  SNR and qualitative scores were highest for D1 + D2 and lowest for ND (all p ≤ 0.001). In 25 % of the patients, ND maps were not assessable and therefore excluded from further analyses. Compared to original data sets, in D2 and D1 + D2, readers correctly identified all patients with ischemic lesions (sensitivity 1.0, kappa 1.0). Lesion size was most accurately estimated for D1 + D2 with a sensitivity of 1.0 (CBV) and 0.94 (CBF) and an inter-rater agreement of 1.0 and 0.92, respectively.
  
  
  CONCLUSIONS
  An appropriate combination of denoising techniques applied in ULD-VPCT produces diagnostically sufficient perfusion maps at substantially reduced dose rates as low as 20 % of the normal scan.
  
  
  CONCLUSIONS
  Perfusion-CT is an accurate tool for the detection of brain ischemias. The high associated radiation doses are a major drawback of brain perfusion CT. Decreasing tube current in perfusion CT increases image noise and deteriorates image quality. Combination of different image-denoising techniques produces sufficient image quality from ultra-low-dose perfusion CT.
authors.affiliation: Department of Diagnostic and Interventional Neuroradiology, RWTH Aachen University, 52074, Aachen, Germany.|Department for Diagnostic and Interventional Radiology, Eberhard Karls University Tuebingen, University Hospital Tuebingen, 72076, Tübingen, Germany.
authors.forename: Ahmed E
authors.initials: AE
authors.lastname: Othman
authors.affiliation: Department of Diagnostic and Interventional Neuroradiology, RWTH Aachen University, 52074, Aachen, Germany.
authors.forename: Carolin
authors.initials: C
authors.lastname: Brockmann
authors.affiliation: Department of Transdisciplinary Studies, Graduate School of Convergence Science and Technology, Seoul National University, Suwon, 433-270, South Korea.|Department of Radiology, Seoul National University College of Medicine, Seoul, 110-744, South Korea.
authors.forename: Zepa
authors.initials: Z
authors.lastname: Yang
authors.affiliation: Department of Transdisciplinary Studies, Graduate School of Convergence Science and Technology, Seoul National University, Suwon, 433-270, South Korea.|Department of Radiology, Seoul National University College of Medicine, Seoul, 110-744, South Korea.
authors.forename: Changwon
authors.initials: C
authors.lastname: Kim
authors.affiliation: Department of Diagnostic and Interventional Neuroradiology, RWTH Aachen University, 52074, Aachen, Germany.
authors.forename: Saif
authors.initials: S
authors.lastname: Afat
authors.affiliation: Department of Diagnostic and Interventional Neuroradiology, RWTH Aachen University, 52074, Aachen, Germany.
authors.forename: Rastislav
authors.initials: R
authors.lastname: Pjontek
authors.affiliation: Department of Diagnostic and Interventional Neuroradiology, RWTH Aachen University, 52074, Aachen, Germany.
authors.forename: Omid
authors.initials: O
authors.lastname: Nikoubashman
authors.affiliation: Department of Diagnostic and Interventional Neuroradiology, RWTH Aachen University, 52074, Aachen, Germany.
authors.forename: Marc A
authors.initials: MA
authors.lastname: Brockmann
authors.affiliation: Department for Diagnostic and Interventional Radiology, Eberhard Karls University Tuebingen, University Hospital Tuebingen, 72076, Tübingen, Germany.
authors.forename: Konstantin
authors.initials: K
authors.lastname: Nikolaou
authors.affiliation: Department of Diagnostic and Interventional Neuroradiology, RWTH Aachen University, 52074, Aachen, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Wiesmann
authors.affiliation: Department of Transdisciplinary Studies, Graduate School of Convergence Science and Technology, Seoul National University, Suwon, 433-270, South Korea. kimjhyo@snu.ac.kr.|Department of Radiology, Seoul National University College of Medicine, Seoul, 110-744, South Korea. kimjhyo@snu.ac.kr.|Center for Medical-IT Convergence Technology Research, Advanced Institute of Convergence Technology, Suwon, 433-270, South Korea. kimjhyo@snu.ac.kr.|Department of Radiology, Seoul National University Hospital, 101 Daehak-Ro, Chongno-gu, Seoul, 110-744, South Korea. kimjhyo@snu.ac.kr.
authors.forename: Jong Hyo
authors.initials: JH
authors.lastname: Kim
mesh_terms: D001921:Brain / Q000000981:diagnostic imaging; D002545:Brain Ischemia / Q000000981:diagnostic imaging*; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D059629:Signal-To-Noise Ratio
keywords: Brain ischemia; Computed tomography; Perfusion imaging; Radiation dosage; Stroke