title: Keyhole Dixon method for faster, perceptually equivalent fat suppression.
abstract: OBJECTIVE
  To reduce the acquisition time associated with the two-point Dixon fat suppression technique by combining a keyhole in-phase (Water + Fat) k-space data set with a full out-of-phase (Water - Fat) k-space data set and optimizing the keyhole size with a perceptual difference model.
  
  
  METHODS
  A set of keyhole Dixon images was created by varying the number of lines in the keyhole data set. Off-resonance correction was incorporated into the image reconstruction process to improve the homogeneity of the fat suppression. A perceptual difference model (PDM) was validated with human observer experiments and used to compare the keyhole images to images from a full two-point Dixon acquisition. The PDM was used to determine the smallest keyhole width required to obtain perceptual equivalence to images obtained from the full two-point Dixon method.
  
  
  RESULTS
  In experimental phantom studies, the keyhole Dixon image reconstructed from 96 of 192 Water + Fat k-space lines and 192 Water - Fat k-space lines was perceptually equivalent to the full (192 + 192) two-point Dixon images, resulting in a 25% reduction in scan time. Clinical images of a volunteer's knee, orbits, and abdomen created from the smallest, perceptually equivalent keyhole width resulted in a 27%-38% reduction in total scan time.
  
  
  CONCLUSIONS
  This method improves the temporal efficiency of the conventional two-point Dixon technique and may prove especially useful for high-field systems where specific absorption rate (SAR) limits will constrain radiofrequency (RF)-based fat suppression techniques.
authors.affiliation: Case Western Reserve University and University Hospitals of Cleveland, Department of Radiology, Ohio 44106, USA.
authors.forename: Chris A
authors.initials: CA
authors.lastname: Flask
authors.forename: Kyle A
authors.initials: KA
authors.lastname: Salem
authors.forename: Hisamoto
authors.initials: H
authors.lastname: Moriguchi
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Lewin
authors.forename: David L
authors.initials: DL
authors.lastname: Wilson
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Duerk
mesh_terms: D000273:Adipose Tissue; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging