title: The Hanes-Woolf linear QUESP method improves the measurements of fast chemical exchange rates with CEST MRI.
abstract: OBJECTIVE
  Contrast agents for chemical exchange saturation transfer MRI often require an accurate measurement of the chemical exchange rate. Many analysis methods have been reported that measure chemical exchange rates. Additional analysis methods were derived as part of this study. This report investigated the accuracy and precision of each analysis method.
  
  
  METHODS
  Chemical exchange saturation transfer spectra were simulated using the Bloch-McConnell equations modified for chemical exchange. Chemical exchange saturation transfer spectra of iopromide were obtained with a range of saturation times, saturation powers, and concentrations. These simulated and experimental results were used to estimate the chemical exchange rate using the QUESP, QUEST, Omega Plot (LB-QUESP), EH-QUESP, HW-QUESP, LB-Conc, EH-Conc, and HW-Conc methods.
  
  
  RESULTS
  Bloch fitting produced the most precise estimates of chemical exchange rates, although substantial expertise and computation time were required to achieve these results. Of the more simplistic analysis methods, the HW-QUESP method produced the most accurate and precise estimates of fast exchange rates. The QUEST and LB-QUESP methods produced the most accurate estimates of slow exchange rates, especially with samples that have short T(1w) relaxation times.
  
  
  CONCLUSIONS
  HW-QUESP is a simplistic analysis method that should be used when fast chemical exchange rates need to be estimated from chemical exchange saturation transfer MRI results.
authors.affiliation: Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona, USA.
authors.forename: Edward A
authors.initials: EA
authors.lastname: Randtke
authors.forename: Liu Qi
authors.initials: LQ
authors.lastname: Chen
authors.forename: L Rene
authors.initials: LR
authors.lastname: Corrales
authors.forename: Mark D
authors.initials: MD
authors.lastname: Pagel
mesh_terms: D003198:Computer Simulation; D003287:Contrast Media / Q000493:pharmacokinetics; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007472:Iohexol / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008954:Models, Biological; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media; D007472:Iohexol; C038192:iopromide
keywords: Bloch; MRI; QUESP; QUEST; chemical exchange rates; chemical exchange saturation transfer; omega plot