title: Mis-estimation and bias of hyperpolarized apparent diffusion coefficient measurements due to slice profile effects.
abstract: The purpose of this work was to explore the impact of slice profile effects on apparent diffusion coefficient (ADC) mapping of hyperpolarized (HP) substrates.
  
  
  
  Slice profile effects were simulated using a Gaussian radiofrequency (RF) pulse with a variety of flip angle schedules and b-value ordering schemes. A long T1water phantom was used to validate the simulation results, and ADC mapping of HP [13C,15N2]urea was performed on the murine liver to assess these effects in vivo.
  
  
  
  Slice profile effects result in excess signal after repeated RF pulses, causing bias in HP measurements. The largest error occurs for metabolites with small ADCs, resulting in up to 10-fold overestimation for metabolites that are in more-restricted environments. A mixed b-value scheme substantially reduces this bias, whereas scaling the slice-select gradient can mitigate it completely. In vivo, the liver ADC of hyperpolarized [13C,15N2]urea is nearly 70% lower (0.99 ± 0.22 vs 1.69 ± 0.21 × 10-3mm2/s) when slice-select gradient scaling is used.
  
  
  
  Slice profile effects can lead to bias in HP ADC measurements. A mixed b-value ordering scheme can reduce this bias compared to sequential b-value ordering. Slice-select gradient scaling can also correct for this deviation, minimizing bias and providing more-precise ADC measurements of HP substrates. Magn Reson Med 78:1087-1092, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
authors.affiliation: Department of Radiology & Biomedical Imaging, UCSF, San Francisco, California, USA.
authors.forename: Jeremy W
authors.initials: JW
authors.lastname: Gordon
authors.affiliation: Department of Radiology & Biomedical Imaging, UCSF, San Francisco, California, USA.
authors.forename: Eugene
authors.initials: E
authors.lastname: Milshteyn
authors.affiliation: Department of Radiology & Biomedical Imaging, UCSF, San Francisco, California, USA.
authors.forename: Irene
authors.initials: I
authors.lastname: Marco-Rius
authors.affiliation: Department of Radiology & Biomedical Imaging, UCSF, San Francisco, California, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Ohliger
authors.affiliation: Department of Radiology & Biomedical Imaging, UCSF, San Francisco, California, USA.
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Vigneron
authors.affiliation: Department of Radiology & Biomedical Imaging, UCSF, San Francisco, California, USA.
authors.forename: Peder E Z
authors.identifier: 0000-0003-4183-3634
authors.initials: PEZ
authors.lastname: Larson
mesh_terms: D000465:Algorithms; D000818:Animals; D003198:Computer Simulation; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008099:Liver / Q000000981:diagnostic imaging; D051379:Mice; D019047:Phantoms, Imaging
keywords: ADC; DNP; diffusion-weighted imaging; hyperpolarization; slice profile effects