title: Dual-Echo EPI sequence for integrated distortion correction in 3D time-resolved hyperpolarized13C MRI.
abstract: To provide built-in off-resonance correction in time-resolved, volumetric hyperpolarized13C metabolic imaging by implementing a novel dual-echo 3D echo-planar imaging (EPI) sequence and reconstruction.
  
  
  
  A spectral-spatial pulse for single-resonance excitation followed by a dual-echo 3D EPI readout was implemented to provide 64 × 8 × 6 cm3coverage at 5 × 5 × 5 mm3nominal resolution. Multiple sources of EPI distortions were encoded using a multi-echo1H EPI reference scan. Phase maps computed from the reference scans were combined with a bulk13C frequency offset encoded in the dual-echo [1-13C]pyruvate images to correct geometric distortion and improve spatial registration. The proposed scheme was validated in a phantom study, and in vivo [1-13C]pyruvate and [1-13C]lactate rat images were acquired with intentional transmit frequency deviations to assess the dual-echo 3D EPI sequence.
  
  
  
  The phantom study demonstrated improved spatial registration in off-resonance corrected images. Close agreement was observed between metabolic kidney signal and the underlying anatomy in rat imaging experiments. Relative to a single-echo acquisition, the coherent addition of the two corrected echoes provided the expected increase in signal-to-noise ratio by approximately 2.
  
  
  
  A novel dual-echo 3D EPI acquisition sequence for integrated off-resonance correction in hyperpolarized13C imaging was developed and demonstrated. The proposed sequence offers clear advantages over flyback EPI for time-resolved metabolic mapping. Magn Reson Med 79:643-653, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
authors.affiliation: Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.|Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario, Canada.
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Geraghty
authors.affiliation: Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.|Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario, Canada.
authors.forename: Justin Y C
authors.initials: JYC
authors.lastname: Lau
authors.affiliation: GE Healthcare, Toronto, Ontario, Canada.
authors.forename: Albert P
authors.initials: AP
authors.lastname: Chen
authors.affiliation: Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.|Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario, Canada.
authors.forename: Charles H
authors.initials: CH
authors.lastname: Cunningham
mesh_terms: D000818:Animals; D017352:Echo-Planar Imaging / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007668:Kidney / Q000000981:diagnostic imaging; D057054:Molecular Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D051381:Rats; D017207:Rats, Sprague-Dawley
keywords: EPI; hyperpolarized 13C; metabolic imaging; off-resonance correction