Artifact and noise suppression in GRAPPA imaging using improved k-space coil calibration and variable density sampling

Jaeseok Park, Qiang Zhang, Vladimir Jellus, Orlando Simonetti, Debiao Li

Research output: Contribution to journalArticlepeer-review

57 Citations (Scopus)


A parallel imaging technique, GRAPPA (GeneRalized Auto-calibrating Partially Parallel Acquisitions), has been used to improve temporal or spatial resolution. Coil calibration in GRAPPA is performed in central k-space by fitting a target signal using its adjacent signals. Missing signals in outer k-space are reconstructed. However, coil calibration operates with signals that exhibit large amplitude variation while reconstruction is performed using signals with small amplitude variation. Different signal variations in coil calibration and reconstruction may result in residual image artifact and noise. The purpose of this work was to improve GRAPPA coil calibration and variable density (VD) sampling for suppressing residual artifact and noise. The proposed coil calibration was performed in local k-space along both the phase and frequency encoding directions. Outer k-space was acquired with two different reduction factors. Phantom data were reconstructed by both the conventional GRAPPA and the improved technique for comparison at an acceleration of two. Under the same acceleration, optimal sampling and calibration parameters were determined. An in vivo image was reconstructed in the same way using the pre-determined optimal parameters. The performance of GRAPPA was improved by the localized coil calibration and VD sampling scheme.

Original languageEnglish
Pages (from-to)186-193
Number of pages8
JournalMagnetic Resonance in Medicine
Issue number1
Publication statusPublished - 2005 Jan


  • Artifact
  • Magnetic resonance imaging (MRI)
  • Noise
  • Parallel imaging
  • Rapid imaging

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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