title: Prepolarized magnetic resonance imaging around metal orthopedic implants.
abstract: A prepolarized MRI (PMRI) scanner was used to image near metal implants in agar gel phantoms and in in vivo human wrists. Comparison images were made on 1.5- and 0.5-T conventional whole-body systems. The PMRI experiments were performed in a smaller bore system tailored to extremity imaging with a prepolarization magnetic field of 0.4 T and a readout magnetic field of 27-54 mT (1.1-2.2 MHz). Scan parameters were chosen with equal readout gradient strength over a given field of view and matrix size to allow unbiased evaluation of the benefits of lower readout frequency. Results exhibit substantial reduction in metal susceptibility artifacts under PMRI versus conventional scanners. A new artifact quantification technique is also presented, and phantom results confirm that susceptibility artifacts improve as expected with decreasing readout magnetic field using PMRI. This proof-of-concept study demonstrates that prepolarized techniques have the potential to provide diagnostic cross-sectional images for postoperative evaluation of patients with metal implants.
authors.affiliation: Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California 94305-9510, USA. ross@mrsrl.stanford.edu
authors.forename: Ross D
authors.initials: RD
authors.lastname: Venook
authors.forename: Nathaniel I
authors.initials: NI
authors.lastname: Matter
authors.forename: Meena
authors.initials: M
authors.lastname: Ramachandran
authors.forename: Sharon E
authors.initials: SE
authors.lastname: Ungersma
authors.forename: Garry E
authors.initials: GE
authors.lastname: Gold
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Giori
authors.forename: Albert
authors.initials: A
authors.lastname: Macovski
authors.forename: Greig C
authors.initials: GC
authors.lastname: Scott
authors.forename: Steven M
authors.initials: SM
authors.lastname: Conolly
mesh_terms: D000328:Adult; D000497:Alloys; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009985:Orthopedics; D019047:Phantoms, Imaging; D019736:Prostheses and Implants; D014025:Titanium
chemical_list: D000497:Alloys; D014025:Titanium