title: Quantitative assessment of susceptibility-weighted imaging processing methods.
abstract: OBJECTIVE
  To evaluate different susceptibility-weighted imaging (SWI) phase processing methods and parameter selection, thereby improving understanding of potential artifacts, as well as facilitating choice of methodology in clinical settings.
  
  
  METHODS
  Two major phase processing methods, homodyne-filtering and phase unwrapping-high pass (HP) filtering, were investigated with various phase unwrapping approaches, filter sizes, and filter types. Magnitude and phase images were acquired from a healthy subject and brain injury patients on a 3T clinical Siemens MRI system. The results were evaluated based on image contrast-to-noise ratio and presence of processing artifacts.
  
  
  RESULTS
  When using a relatively small filter size (32 pixels for the matrix size 512 × 512 pixels), all homodyne-filtering methods were subject to phase errors leading to 2% to 3% masked brain area in lower and middle axial slices. All phase unwrapping-filtering/smoothing approaches demonstrated fewer phase errors and artifacts compared to the homodyne-filtering approaches. For performing phase unwrapping, Fourier-based methods, although less accurate, were 2-4 orders of magnitude faster than the PRELUDE, Goldstein, and Quality-guide methods.
  
  
  CONCLUSIONS
  Although homodyne-filtering approaches are faster and more straightforward, phase unwrapping followed by HP filtering approaches perform more accurately in a wider variety of acquisition scenarios.
authors.affiliation: Image Processing Core, Center for Neuroscience and Regenerative Medicine, Bethesda, Maryland, USA.
authors.forename: Ningzhi
authors.initials: N
authors.lastname: Li
authors.forename: Wen-Tung
authors.initials: WT
authors.lastname: Wang
authors.forename: Pascal
authors.initials: P
authors.lastname: Sati
authors.forename: Dzung L
authors.initials: DL
authors.lastname: Pham
authors.forename: John A
authors.initials: JA
authors.lastname: Butman
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: homodyne filter; image contrast; phase unwrapping; susceptibility weighted imaging