Quantitative characterization of nuclear overhauser enhancement and amide proton transfer effects in the human brain at 7 tesla
Article first published online: 13 DEC 2012
Copyright © 2012 Wiley Periodicals, Inc.
Magnetic Resonance in Medicine
Volume 70, Issue 4, pages 1070–1081, October 2013
How to Cite
Liu, D., Zhou, J., Xue, R., Zuo, Z., An, J. and Wang, D. J. J. (2013), Quantitative characterization of nuclear overhauser enhancement and amide proton transfer effects in the human brain at 7 tesla. Magn Reson Med, 70: 1070–1081. doi: 10.1002/mrm.24560
- Issue published online: 24 SEP 2013
- Article first published online: 13 DEC 2012
- Manuscript Accepted: 24 OCT 2012
- Manuscript Revised: 27 SEP 2012
- Manuscript Received: 17 JUL 2012
- Ministry of Science and Technology of China. Grant Number: 2012CB825500 and 2009IM030900
- Knowledge Innovation Project. Grant Number: KSCX2-YW-R-259
- Major Scientific & Research Equipment and Instrument Developing Project of the Chinese Academy of Sciences. Grant Number: ZDYZ2010-2
- National Natural Science Foundation of China (NSFC). Grant Numbers: 91132302, 90820307, 81128006
- National Institutes of Health. Grant Number: R01EB009731 and R01MH080892-04S1
- magnetization transfer;
- nuclear Overhauser enhancement;
- amide proton transfer;
- ultra high field;
- chemical exchange saturation transfer
This study aimed to quantitatively investigate two main magnetization transfer effects at low B1: the nuclear Overhauser enhancement (NOE) and amide proton transfer in the human brain at 7 T.
The magnetization transfer effects in the human brain were characterized using a four-pool proton model, which consisted of bulk water, macromolecules, an amide group of mobile proteins and peptides, and NOE-related protons resonating upfield. The pool sizes, exchange rates, and relaxation times of these proton pools were investigated quantitatively by fitting, and the net signals of amide proton transfer and NOE were simulated based on the fitted parameters.
The results showed that the four-pool model fitted the experimental data quite well, and the NOE effects in human brain at 7 T had a broad spectrum distribution. The NOE effects peaked at a B1 of ∼ 1–1.4 μT and were significantly stronger in the white matter than in the gray matter, corresponding to a pool-size ratio ∼ 2:1. As the amide proton transfer effect was relatively small compared with the NOE effects, magnetization transfer asymmetry analysis yielded an NOE-dominated contrast in the healthy human brain in this range of B1.
These findings are important to identify the source of NOE effects and to quantify amide proton transfer effects in human brain at 7 T. Magn Reson Med, 70:1070–1081, 2013. © 2012 Wiley Periodicals, Inc.