title: Noise reduction in three-dimensional phase-contrast MR velocity measurements.
abstract: The authors have developed a method to reduce noise in three-dimensional (3D) phase-contrast magnetic resonance (MR) velocity measurements by exploiting the property that blood is incompressible and, therefore, the velocity field describing its flow must be divergence-free. The divergence-free condition is incorporated by a projection operation in Hilbert space. The velocity field obtained with 3D phase-contrast MR imaging is projected onto the space of divergence-free velocity fields. The reduction of noise is achieved because the projection operation eliminates the noise component that is not divergence-free. Signal-to-noise ratio (S/N) gains on the order of 15%-25% were observed. The immediate effect of this noise reduction manifests itself in higher-quality phase-contrast MR angiograms. Alternatively, the S/N gain can be traded for a reduction in imaging time and/or improved spatial resolution.
authors.affiliation: Richard M. Lucas Center for Magnetic Resonance Spectroscopy and Imaging, Department of Diagnostic Radiology, Stanford University, CA 94305-5488.
authors.forename: S M
authors.initials: SM
authors.lastname: Song
authors.forename: S
authors.initials: S
authors.lastname: Napel
authors.forename: G H
authors.initials: GH
authors.lastname: Glover
authors.forename: N J
authors.initials: NJ
authors.lastname: Pelc
mesh_terms: D000465:Algorithms; D001783:Blood Flow Velocity; D002339:Carotid Arteries / Q000033:anatomy & histology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008955:Models, Cardiovascular; D008961:Models, Structural; D008962:Models, Theoretical