title: Multiband excitation pulses for hyperpolarized 13C dynamic chemical-shift imaging.
abstract: Hyperpolarized 13C offers high signal-to-noise ratios for imaging metabolic activity in vivo, but care must be taken when designing pulse sequences because the magnetization cannot be recovered once it has decayed. It has a short lifetime, on the order of minutes, and gets used up by each RF excitation. In this paper, we present a new dynamic chemical-shift imaging method that uses specialized RF pulses designed to maintain most of the hyperpolarized substrate while providing adequate SNR for the metabolic products. These are multiband, variable flip angle, spectral-spatial RF pulses that use spectral selectivity to minimally excite the injected prepolarized 13C-pyruvate substrate. The metabolic products of lactate and alanine are excited with a larger flip angle to increase SNR. This excitation was followed by an RF amplitude insensitive double spin-echo and an echo-planar flyback spectral-spatial readout gradient. In vivo results in rats and mice are presented showing improvements over constant flip angle RF pulses. The metabolic products are observable for a longer window because the low pyruvate flip angle preserves magnetization, allowing for improved observation of spatially varying metabolic reactions.
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California-San Francisco, Byers Hall, Suite 102, 1700 4th Street, San Francisco, CA 94158, USA. peder.larson@radiology.ucsf.edu
authors.forename: Peder E Z
authors.initials: PE
authors.lastname: Larson
authors.forename: Adam B
authors.initials: AB
authors.lastname: Kerr
authors.forename: Albert P
authors.initials: AP
authors.lastname: Chen
authors.forename: Michael S
authors.initials: MS
authors.lastname: Lustig
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Zierhut
authors.forename: Simon
authors.initials: S
authors.lastname: Hu
authors.forename: Charles H
authors.initials: CH
authors.lastname: Cunningham
authors.forename: John M
authors.initials: JM
authors.lastname: Pauly
authors.forename: John
authors.initials: J
authors.lastname: Kurhanewicz
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Vigneron
mesh_terms: D000818:Animals; D002247:Carbon Isotopes / Q000032:analysis*; D045744:Cell Line, Tumor; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D051379:Mice; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology*; D051381:Rats; D012815:Signal Processing, Computer-Assisted
chemical_list: D002247:Carbon Isotopes