title: Multilevel wavelet-transform encoding in MRI.
abstract: This paper explores an alternative to standard Fourier MRI called wavelet-transform encoding. Spatially selective radiofrequency (RF) pulses are used to excite slice profiles in the shape of the wavelet-basis functions of a discrete wavelet transform. Our implementation on a standard commercial whole body MRI system resolves one spatial dimension through wavelet encoding and orthogonal directions through conventional frequency encoding and rectangular-slice selection. The wavelet transform is described as a method for multiresolution analysis, and we show how a high resolution MR image can be constructed from lower resolution images, representing the approximation and detail structures of the object. A multiple level architecture of the wavelet reconstruction is described, thereby allowing wavelet-encoded images to be reconstructed through several modes. Multilevel wavelet-encoded images of a gel phantom are presented that show comparable image quality to Fourier-encoded images of similar signal-to-noise ratio. However, a chemical-shift artifact is identified with this particular implementation.
authors.affiliation: Department of Medical Biophysics, University of Toronto, Sunnybrook Health Science Center (Imaging Research), Ontario, Canada.
authors.forename: R D
authors.initials: RD
authors.lastname: Peters
authors.forename: M L
authors.initials: ML
authors.lastname: Wood
mesh_terms: D016477:Artifacts; D005583:Fourier Analysis; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation*; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D019047:Phantoms, Imaging; D012984:Software