Optimization and validation of accelerated golden-angle radial sparse MRI reconstruction with self-calibrating GRAPPA operator gridding

Magn Reson Med. 2018 Jul;80(1):286-293. doi: 10.1002/mrm.27030. Epub 2017 Nov 28.


Purpose: Golden-angle radial sparse parallel (GRASP) MRI reconstruction requires gridding and regridding to transform data between radial and Cartesian k-space. These operations are repeatedly performed in each iteration, which makes the reconstruction computationally demanding. This work aimed to accelerate GRASP reconstruction using self-calibrating GRAPPA operator gridding (GROG) and to validate its performance in clinical imaging.

Methods: GROG is an alternative gridding approach based on parallel imaging, in which k-space data acquired on a non-Cartesian grid are shifted onto a Cartesian k-space grid using information from multicoil arrays. For iterative non-Cartesian image reconstruction, GROG is performed only once as a preprocessing step. Therefore, the subsequent iterative reconstruction can be performed directly in Cartesian space, which significantly reduces computational burden. Here, a framework combining GROG with GRASP (GROG-GRASP) is first optimized and then compared with standard GRASP reconstruction in 22 prostate patients.

Results: GROG-GRASP achieved approximately 4.2-fold reduction in reconstruction time compared with GRASP (∼333 min versus ∼78 min) while maintaining image quality (structural similarity index ≈ 0.97 and root mean square error ≈ 0.007). Visual image quality assessment by two experienced radiologists did not show significant differences between the two reconstruction schemes. With a graphics processing unit implementation, image reconstruction time can be further reduced to approximately 14 min.

Conclusion: The GRASP reconstruction can be substantially accelerated using GROG. This framework is promising toward broader clinical application of GRASP and other iterative non-Cartesian reconstruction methods. Magn Reson Med 80:286-293, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Keywords: GROG-GRASP; gridding; iterative reconstruction; non-Cartesian.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Aged
  • Algorithms
  • Calibration
  • Contrast Media
  • Heart / diagnostic imaging*
  • Humans
  • Image Enhancement / methods
  • Image Processing, Computer-Assisted / methods*
  • Magnetic Resonance Imaging*
  • Male
  • Middle Aged
  • Observer Variation
  • Phantoms, Imaging
  • Radiology
  • Radionuclide Imaging
  • Retrospective Studies
  • Software


  • Contrast Media