title: Method for high-resolution imaging of creatine in vivo using chemical exchange saturation transfer.
abstract: OBJECTIVE
  To develop a chemical exchange saturation transfer (CEST)-based technique to measure free creatine (Cr) and to validate the technique by measuring the distribution of Cr in muscle with high spatial resolution before and after exercise.
  
  
  METHODS
  Phantom studies were performed to determine contributions from other Cr kinase metabolites to the CEST effect from Cr (CrCEST). CEST, T2 , magnetization transfer ratio and (31) P magnetic resonance spectroscopy acquisitions of the lower leg were performed before and after plantar flexion exercise on a 7T whole-body magnetic resonance scanner on healthy volunteers.
  
  
  RESULTS
  Phantom studies demonstrated that while Cr exhibited significant CEST effect there were no appreciable contributions from other metabolites. In healthy human subjects, following mild plantar flexion exercise, increases in the CEST effect from Cr were observed, which recovered exponentially back to baseline. This technique exhibited good spatial resolution and was able to differentiate differences in muscle utilization among subjects. The CEST effect from Cr results were compared with (31) P magnetic resonance spectroscopy results showing good agreement in the Cr and phosphocreatine recovery kinetics.
  
  
  CONCLUSIONS
  Demonstrated a CEST-based technique to measure free Cr changes in in vivo muscle. The CEST effect from Cr imaging can spatially map changes in Cr concentration in muscle following mild exercise. This may serve as a tool for the diagnosis and treatment of various disorders affecting muscle.
authors: Center for Magnetic Resonance and Optical Imaging, Department of Radiology, University of Pennsylvania, B1 Stellar-Chance Labs, 422 Curie Boulevard, Philadelphia, Pennsylvania, USA; Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors: Feliks
authors: F
authors: Kogan
authors: Mohammad
authors: M
authors: Haris
authors: Anup
authors: A
authors: Singh
authors: Kejia
authors: K
authors: Cai
authors: Catherine
authors: C
authors: Debrosse
authors: Ravi Prakash Reddy
authors: RP
authors: Nanga
authors: Hari
authors: H
authors: Hariharan
authors: Ravinder
authors: R
authors: Reddy
mesh_terms: D000328:Adult; D000465:Algorithms; D003401:Creatine / Q000378:metabolism*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution; D055815:Young Adult
chemical_list: D003401:Creatine
keywords: CEST; chemical exchange; creatine; endogenous contrast; muscle