title: Monoenergetic extrapolation of cardiac dual energy CT for artifact reduction.
abstract: BACKGROUND
  Monoenergetic extrapolation of cardiac dual-energy computed tomography (DECT) could be useful in artifact reduction in clinical practice.
  
  
  OBJECTIVE
  To evaluate the potential of monoenergetic extrapolation of cardiac DECT data for reducing artifacts from metal and high iodine contrast concentration.
  
  
  METHODS
  With IRB approval and in HIPAA compliance, 35 patients (22 men, 61 ± 12 years) underwent cardiac DECT with dual-source CT (100 kVp and 140 kVp). Contrast material injection protocols were adapted to the patient's weight using non-ionic low-osmolar 370 mgI/mL iopromide. Datasets were transferred to a stand-alone workstation and dedicated monoenergetic analysis software was used for postprocessing. Reconstructions with the following five photon energies were generated: 40 keV, 60 keV, 80 keV, 100 keV, and 120 keV. Artifact severity was graded on a 5-point Likert scale (0, massive artifact; 5, absence of artifact). The size of artifact and image noise (expressed as HU) in anatomic structures adjacent to the artifact were measured. Quantitative and subjective image quality was compared using Friedman and Wilcoxon tests.
  
  
  RESULTS
  We observed artifacts arising from densely concentrated contrast material in the superior vena cava (SVC) in 18 patients, from sternal wires in 14, from bypass clips in eight, and from coronary artery stents in seven. Artifact size in monoenergetic reconstructions from 40 to 120 keV decreased from 21.3 to 19 mm for the SVC (P < 0.001), from 8.4 to 2.6 mm for sternal wires (P < 0.001), from 6.4 to 2.2 mm for bypass clips (P < 0.001), and from 5.9 to 2.7 mm for stents (P < 0.001), respectively. The quality score changed from 0.2 to 3.8 for the SVC (P < 0.001), from 0.1 to 4 for sternal wires (P < 0.001), from 0 to 3.9 for bypass clips (P < 0.001), and from 0 to 3.9 for stents (P < 0.001). Lowest noise in adjacent structures was found at 80 keV for the SVC (39.1 HU), for sternal wires (33.3), for bypass clips (26.9), and for stents (33.9).
  
  
  CONCLUSIONS
  A significant reduction of high-attenuation artifacts can be achieved by use of higher monoenergetic energy levels with cardiac DECT. However, image noise in anatomic structures affected by artifacts is lowest at 80 keV, which suggests an evaluation approach that makes use of multiple energy levels for a complete diagnosis.
authors.affiliation: Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA IRCCS Policlinico San Donato, Radiology Unit, San Donato Milanese, Italy francesco.secchi@grupposandonato.it.
authors.forename: Francesco
authors.initials: F
authors.lastname: Secchi
authors.affiliation: Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA Department of Radiological Sciences, Oncology and Pathology, University of Rome "Sapienza" - Polo Pontino, Latina, Italy.
authors.forename: Carlo Nicola
authors.initials: CN
authors.lastname: De Cecco
authors.affiliation: Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: James Vance
authors.initials: JV
authors.lastname: Spearman
authors.affiliation: Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: Justin Robert
authors.initials: JR
authors.lastname: Silverman
authors.affiliation: Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA Department of Cardiology and Intensive Care Medicine, Heart Center Munich-Bogenhausen, Munich, Germany.
authors.forename: Ullrich
authors.initials: U
authors.lastname: Ebersberger
authors.affiliation: IRCCS Policlinico San Donato, Radiology Unit, San Donato Milanese, Italy Università degli Studi di Milano, Dipartimento di Scienze Biomediche per la Salute, Milano, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Sardanelli
authors.affiliation: Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: U Joseph
authors.initials: UJ
authors.lastname: Schoepf
mesh_terms: D016477:Artifacts; D003287:Contrast Media; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging*; D006801:Humans; D007472:Iohexol / Q000031:analogs & derivatives; D008297:Male; D008875:Middle Aged; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D007472:Iohexol; C038192:iopromide
keywords: Dual energy CT (DECT); artifact; monoenergetic extrapolation