RACER-GRASP: Respiratory-weighted, aortic contrast enhancement-guided and coil-unstreaking golden-angle radial sparse MRI

Li Feng, Chenchan Huang, Krishna Shanbhogue, Daniel K. Sodickson, Hersh Chandarana, Ricardo Otazo

Research output: Contribution to journalArticlepeer-review


Purpose: To develop and evaluate a novel dynamic contrast-enhanced imaging technique called RACER-GRASP (Respiratory-weighted, Aortic Contrast Enhancement-guided and coil-unstReaking Golden-angle RAdial Sparse Parallel) MRI that extends GRASP to include automatic contrast bolus timing, respiratory motion compensation, and coil-weighted unstreaking for improved imaging performance in liver MRI. Methods: In RACER-GRASP, aortic contrast enhancement (ACE) guided k-space sorting and respiratory-weighted sparse reconstruction are performed using aortic contrast enhancement and respiratory motion signals extracted directly from the acquired data. Coil unstreaking aims to weight multicoil k-space according to streaking artifact level calculated for each individual coil during image reconstruction, so that coil elements containing a high level of streaking artifacts contribute less to the final results. Self-calibrating GRAPPA operator gridding was applied as a pre-reconstruction step to reduce computational burden in the subsequent iterative reconstruction. The RACER-GRASP technique was compared with standard GRASP reconstruction in a group of healthy volunteers and patients referred for clinical liver MR examination. Results: Compared with standard GRASP, RACER-GRASP significantly improved overall image quality (average score: 3.25 versus 3.85) and hepatic vessel sharpness/clarity (average score: 3.58 versus 4.0), and reduced residual streaking artifact level (average score: 3.23 versus 3.94) in different contrast phases. RACER-GRASP also enabled automatic timing of the arterial phases. Conclusions: The aortic contrast enhancement–guided sorting, respiratory motion suppression and coil unstreaking introduced by RACER-GRASP improve upon the imaging performance of standard GRASP for free-breathing dynamic contrast-enhanced MRI of the liver. Magn Reson Med 80:77–89, 2018.

Original languageEnglish (US)
Pages (from-to)77-89
Number of pages13
JournalMagnetic resonance in medicine
Issue number1
StatePublished - Jul 2018


  • coil unstreaking
  • compressed sensing
  • free breathing
  • liver
  • radial imaging
  • streaking artifact
  • Humans
  • Middle Aged
  • Breath Holding
  • Magnetic Resonance Imaging/methods
  • Male
  • Data Compression
  • Young Adult
  • Aorta/diagnostic imaging
  • Computer Simulation
  • Image Processing, Computer-Assisted/methods
  • Adult
  • Female
  • Image Interpretation, Computer-Assisted/methods
  • Motion
  • Imaging, Three-Dimensional/methods
  • Artifacts
  • Algorithms
  • Contrast Media
  • Respiration
  • Liver/diagnostic imaging
  • Cluster Analysis

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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