title: Application of flow sensitive gradients for improved measures of metabolism using hyperpolarized (13) c MRI.
abstract: OBJECTIVE
  To develop the use of bipolar gradients to suppress partial-volume and flow-related artifacts from macrovascular, hyperpolarized spins.
  
  
  METHODS
  Digital simulations were performed over a range of spatial resolutions and gradient strengths to determine the optimal bipolar gradient strength and duration to suppress flowing spins while minimizing signal loss from static tissue. In vivo experiments were performed to determine the efficacy of this technique to suppress vascular signal in the study of hyperpolarized [1-(13)C]pyruvate renal metabolism.
  
  
  RESULTS
  Digital simulations showed that in the absence of bipolar gradients, partial-volume artifacts from the vasculature were still present, causing underestimation of the apparent reaction rate of pyruvate to lactate (kP). The addition of a bipolar gradient with b = 32 s/mm(2) sufficiently suppressed the vascular signal without a substantial decrease in signal from static tissue. In vivo results corroborate digital simulations, with similar peak lactate signal to noise ratio (SNR) but substantially different kP in the presence of bipolar gradients.
  
  
  CONCLUSIONS
  The proposed approach suppresses signal from flowing spins while minimizing signal loss from static tissue, removing contaminating signal from the vasculature and increasing kinetic modeling accuracy without substantially sacrificing SNR or temporal resolution.
authors.affiliation: Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Jeremy W
authors.initials: JW
authors.lastname: Gordon
authors.affiliation: Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Niles
authors.affiliation: Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Erin B
authors.initials: EB
authors.lastname: Adamson
authors.affiliation: Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Johnson
authors.affiliation: Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA.|Radiology, University of Wisconsin-Madison, Madison, Madison, Wisconsin, USA.|Biomedical Engineering, University of Wisconsin-Madison, Madison, Madison, Wisconsin, USA.
authors.forename: Sean B
authors.initials: SB
authors.lastname: Fain
mesh_terms: D000818:Animals; D002247:Carbon Isotopes / Q000032:analysis / Q000378:metabolism; D003198:Computer Simulation; D019344:Lactic Acid / Q000378:metabolism; D008279:Magnetic Resonance Imaging / Q000379:methods*; D055442:Metabolome; D055432:Metabolomics / Q000379:methods*; D051379:Mice; D008813:Mice, Inbred ICR; D019289:Pyruvic Acid / Q000378:metabolism; D012815:Signal Processing, Computer-Assisted
chemical_list: D002247:Carbon Isotopes; D019344:Lactic Acid; D019289:Pyruvic Acid
keywords: DNP; diffusion; hyperpolarization; metabolism; pyruvate; vascular suppression