Display Settings:

Format

Send to:

Choose Destination

    Magn Reson Med. 2009 Jun;61(6):1500-6.

    Improved shim method based on the minimization of the maximum off-resonance frequency for balanced steady-state free precession (bSSFP).

    Lee J, Lustig M, Kim DH, Pauly JM.

    Advanced MRI, Laboratory for Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA. jonghoyi@mail.nih.gov

    In this work, a shim method that minimizes the maximum off-resonance frequency (min-max shim) in balanced steady-state free precession (bSSFP) is tested for brain imaging at 3T with constant and linear shim terms. The method demonstrates improvement of spatial coverage and banding artifact reduction over standard least-squares shimming. In addition, a new method (modified min-max shim) is introduced. This method reduces boundary band regions where the artifact is inevitable due to the excessive off-resonance frequency distribution. In comparison to standard least-squares shimming, the min-max based shim method either eliminates or reduces the size of banding artifacts. The method can be used to increase the signal-to-noise ratio (SNR) in bSSFP imaging or to increase the functional contrast in bSSFP functional MRI (fMRI) by allowing a longer usable repetition time (TR).

    PMID: 19319895 [PubMed - indexed for MEDLINE]

    PMCID: 2729138

    Supplemental Content

    Click here to read Click here to read Click here to read