title: Imaging amide proton transfer and nuclear overhauser enhancement using chemical exchange rotation transfer (CERT).
abstract: OBJECTIVE
  This study investigates amide proton transfer (APT) and nuclear overhauser enhancement (NOE) in phantoms and 9L tumors in rat brains at 9.4 Tesla, using a recently developed method that can isolate different contributions to exchange.
  
  
  METHODS
  Chemical exchange rotation transfer (CERT) was used to quantify APT and NOEs through subtraction of signals acquired at two irradiation flip angles, but with the same average irradiation power.
  
  
  RESULTS
  CERT separates and quantifies specific APT and NOE signals without contamination from other proton pools, and thus overcomes a key shortcoming of conventional CEST asymmetry approaches. CERT thus has increased specificity, though at the cost of decreased signal strength. In vivo experiments show that the APT effect acquired with CERT in 9L rat tumors (3.1%) is relatively greater than that in normal tissue (2.5%), which is consistent with previous CEST asymmetry analysis. The NOE effect centered at -1.6 ppm shows substantial image contrast within the tumor and between the tumor and the surrounding tissue, while the NOE effect centered at -3.5 ppm shows little contrast.
  
  
  CONCLUSIONS
  CERT provides an image contrast that is more specific to chemical exchange than conventional APT by means of asymmetric CEST Z-spectra analysis.
authors.affiliation: Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA; Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Zhongliang
authors.initials: Z
authors.lastname: Zu
authors.forename: Junzhong
authors.initials: J
authors.lastname: Xu
authors.forename: Hua
authors.initials: H
authors.lastname: Li
authors.forename: Eduard Y
authors.initials: EY
authors.lastname: Chekmenev
authors.forename: C Chad
authors.initials: CC
authors.lastname: Quarles
authors.forename: Mark D
authors.initials: MD
authors.lastname: Does
authors.forename: John C
authors.initials: JC
authors.lastname: Gore
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Gochberg
mesh_terms: D000465:Algorithms; D000577:Amides / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D001932:Brain Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D005910:Glioma / Q000378:metabolism*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D011522:Protons; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D000577:Amides; D011522:Protons
keywords: amide proton transfer (APT); chemical exchange rotation transfer (CERT); chemical exchange saturation transfer (CEST); nuclear overhauser enhancement (NOE)