title: Quantitative assessment of the effects of water proton concentration and water T1changes on amide proton transfer (APT) and nuclear overhauser enhancement (NOE) MRI: The origin of the APT imaging signal in brain tumor.
abstract: To quantify pure chemical exchange-dependent saturation transfer (CEST) related amide proton transfer (APT) and nuclear Overhauser enhancement (NOE) signals in a rat glioma model and to investigate the mixed effects of water content and water T1on APT and NOE imaging signals.
  
  
  
  Eleven U87 tumor-bearing rats were scanned at 4.7 T. A relatively accurate mathematical approach, based on extrapolated semisolid magnetization-transfer reference signals, was used to remove the concurrent effects of direct water saturation and semisolid magnetization-transfer. Pure APT and NOE signals, in addition to the commonly used magnetization-transfer-ratio asymmetry at 3.5 ppm, MTRasym(3.5ppm), were assessed.
  
  
  
  The measured APT signal intensity of the tumor (11.06%, much larger than the value reported in the literature) was the major contributor (approximately 80.6%) to the MTRasym(3.5ppm) contrast between the tumor and the contralateral brain region. Both the water content ([water proton]) and water T1(T1w) were increased in the tumor, but there were no significant correlations among APT, NOE, or MTRasym(3.5ppm) signals and T1w/[water proton].
  
  
  
  The effect of increasing T1won the CEST signal in the tumor was mostly eliminated by the effect of increasing water content, and the observed APT-weighted hyperintensity in the tumor should be dominated by the increased amide proton concentration. Magn Reson Med 77:855-863, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
authors: Division of MR Research, Dept. of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors: Dong-Hoon
authors: DH
authors: Lee
authors: Division of MR Research, Dept. of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors: Hye-Young
authors: HY
authors: Heo
authors: Division of MR Research, Dept. of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors: Kai
authors: K
authors: Zhang
authors: Division of MR Research, Dept. of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors: Yi
authors: Y
authors: Zhang
authors: Division of MR Research, Dept. of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors: Shanshan
authors: S
authors: Jiang
authors: Division of MR Research, Dept. of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors: Xuna
authors: X
authors: Zhao
authors: Division of MR Research, Dept. of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.|F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA.
authors: Jinyuan
authors: J
authors: Zhou
mesh_terms: D000577:Amides / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000000981:diagnostic imaging* / Q000378:metabolism; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D011522:Protons; D051381:Rats; D011923:Rats, Nude; D012815:Signal Processing, Computer-Assisted; D014867:Water
chemical_list: D000577:Amides; D011522:Protons; D014867:Water
keywords: APT; CEST; MT; NOE; water T1; water content