title: A 2DRF pulse sequence for bolus tracking in hyperpolarized 13C imaging.
abstract: OBJECTIVE
  A novel application of two-dimensional (2D) spatially selective radiofrequency (2DRF) excitation pulses in hyperpolarized 13C imaging is proposed for monitoring the bolus injection with highly efficient sampling of the initially polarized substrate, thus leaving more polarization available for detection of the subsequently generated metabolic products.
  
  
  METHODS
  A 2DRF pulse was designed with a spiral trajectory and conventional clinical gradient performance. To demonstrate the ability of our 2DRF bolus tracking pulse sequence, hyperpolarized [1-(13)ruvate in vivo imaging experiments were performed in normal rats, with a comparison to 1DRF excitation pulses.
  
  
  RESULTS
  Our designed 2DRF pulse was able to rapidly and efficiently monitor the injected bolus dynamics in vivo, with an 8-fold enhanced time resolution in comparison with 1DRF in our experimental settings. When applied at the pyruvate frequency for bolus tracking, our 2DRF pulse demonstrated reduced saturation of the hyperpolarization for the substrate and metabolic products compared to a 1DRF pulse, while being immune to ±0.5 ppm magnetic field inhomogeneity at 3T.
  
  
  CONCLUSIONS
  2DRF pulses in hyperpolarized 13C imaging can be used to efficiently monitor the bolus injection with reduced hyperpolarization saturation compared to 1DRF pulses. The parameters of our design are based on clinical scanner limits, which allows for rapid translation to human studies.
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California - San Francisco, San Francisco, California, USA.
authors.forename: Shuyu
authors.initials: S
authors.lastname: Tang
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California - San Francisco, San Francisco, California, USA.|UC Berkeley-UCSF Graduate Program in Bioengineering, University of California, San Francisco and University of California, Berkeley, USA.
authors.forename: Wenwen
authors.initials: W
authors.lastname: Jiang
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California - San Francisco, San Francisco, California, USA.|UC Berkeley-UCSF Graduate Program in Bioengineering, University of California, San Francisco and University of California, Berkeley, USA.
authors.forename: Hsin-Yu
authors.initials: HY
authors.lastname: Chen
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California - San Francisco, San Francisco, California, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Bok
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California - San Francisco, San Francisco, California, USA.|UC Berkeley-UCSF Graduate Program in Bioengineering, University of California, San Francisco and University of California, Berkeley, USA.
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Vigneron
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California - San Francisco, San Francisco, California, USA.|UC Berkeley-UCSF Graduate Program in Bioengineering, University of California, San Francisco and University of California, Berkeley, USA.
authors.forename: Peder E Z
authors.initials: PE
authors.lastname: Larson
mesh_terms: D000465:Algorithms; D000818:Animals; D002247:Carbon Isotopes / Q000493:pharmacokinetics; D066241:Carbon-13 Magnetic Resonance Spectroscopy / Q000379:methods*; D005240:Feasibility Studies; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007668:Kidney / Q000033:anatomy & histology / Q000378:metabolism*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D057054:Molecular Imaging / Q000379:methods*; D019289:Pyruvic Acid / Q000493:pharmacokinetics*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D051381:Rats; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted
chemical_list: D002247:Carbon Isotopes; D019275:Radiopharmaceuticals; D019289:Pyruvic Acid
keywords: 13C; 2DRF pulse; MRI; bolus tracking; hyperpolarized; pyruvate; reduced field of view imaging