title: Variability of myocardial perfusion dark rim Gibbs artifacts due to sub-pixel shifts.
abstract: BACKGROUND
  Gibbs ringing has been shown as a possible source of dark rim artifacts in myocardial perfusion studies. This type of artifact is usually described as transient, lasting a few heart beats, and localised in random segments of the myocardial wall. Dark rim artifacts are known to be unpredictably variable. This article aims to illustrate that a sub-pixel shift, i.e. a small displacement of the pixels with respect to the endocardial border, can result in different Gibbs ringing and hence different artifacts. Therefore a hypothesis for one cause of dark rim artifact variability is given based on the sub-pixel position of the endocardial border. This article also demonstrates the consequences for Gibbs artifacts when two different methods of image interpolation are applied (post-FFT interpolation, and pre-FFT zero-filling).
  
  
  RESULTS
  Sub-pixel shifting of in vivo perfusion studies was shown to change the appearance of Gibbs artifacts. This effect was visible in the original un-interpolated images, and in the post-FFT interpolated images. The same shifted data interpolated by pre-FFT zero-filling exhibited much less variability in the Gibbs artifact. The in vivo findings were confirmed by phantom imaging and numerical simulations.
  
  
  CONCLUSIONS
  Unless pre-FFT zero-filling interpolation is performed, Gibbs artifacts are very dependent on the position of the subendocardial wall within the pixel. By introducing sub-pixel shifts relative to the endocardial border, some of the variability of the dark rim artifacts in different myocardial segments, in different patients and from frame to frame during first-pass perfusion due to cardiac and respiratory motion can be explained. Image interpolation by zero-filling can be used to minimize this dependency.
authors.affiliation: National Heart and Lung Institute, Imperial College, London, UK. p.f.ferreira05@imperial.ac.uk
authors.forename: Pedro
authors.initials: P
authors.lastname: Ferreira
authors.forename: Peter
authors.initials: P
authors.lastname: Gatehouse
authors.forename: Peter
authors.initials: P
authors.lastname: Kellman
authors.forename: Chiara
authors.initials: C
authors.lastname: Bucciarelli-Ducci
authors.forename: David
authors.initials: D
authors.lastname: Firmin
mesh_terms: D000241:Adenosine; D016477:Artifacts; D003198:Computer Simulation; D003287:Contrast Media; D004562:Electrocardiography; D004699:Endocardium / Q000473:pathology; D019786:Gadolinium DTPA; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008955:Models, Cardiovascular; D055414:Myocardial Perfusion Imaging / Q000295:instrumentation*; D009206:Myocardium / Q000473:pathology*; D019047:Phantoms, Imaging; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012189:Retrospective Studies
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA; D000241:Adenosine