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Jun Shen, PhD, Unit Chief
OVERVIEW
This Unit focuses on development and application of state-of-the-art magnetic resonance spectroscopy (MRS) and imaging (MRI) technologies. The Unit has access to a 7 Tesla and a 3 Tesla whole-body spectrometer for research on human subjects as well as an 11.7 Tesla vertical widebore spectrometer for both in vivo and in vitro studies of small rodents. The high field strength magnets allow dramatic improvement in resolution and sensitivity for MRS and MRI measurements while presenting unique technical challenges. These technical challenges are addressed using novel design and implementation of RF probes, RF pulses and RF/gradient pulse sequences as well as sophisticated data analysis methods.
Using high-field MRS and MRI methods this Unit also performs basic research on neurotransmission and neurotransmitter metabolism. In particular, in vivo assessment of glutamate and GABA neurotransmission and metabolism is used to explore the function and modulation of these neurotransmitters in the brain under a variety of conditions. The aim is to further our understanding of the role of these neurotransmitters and other important metabolites in psychiatric disorders.
Contact Information Jun Shen, Ph.D. MIB/MADP/NIMH Building 10, 2D51A, MSC-1527 10 Center Drive Bethesda, MD. 20892-1527 Phone: (301) 435-8444 Fax: (301) 402-3480 Email: shenj@intra.nimh.nih.gov
PEOPLE
ON GOING PROJECTS
- GABA spectroscopy imaging development. GABA spectroscopic imaging maps spatial distribution of GABA concentrations and synthesis rates. Significant challenges to GABA spectroscopic imaging exist including 1) elimination of overlap with the intense creating resonance, 2) separation of the GABA resonance from the resonance of co-edited macromolecules, 3) the development of inverse detection methods which allow measurement of GABA synthesis, 4) achievement of the highest possible sensitivity and resolution. We are evaluating a novel multiple quantum filtering method for the purpose of GABA spectroscopic imaging. The method is designed to provide complete suppression of overlapping creatine, glutathione and macromolecules without sacrificing sensitivity relative to J-editing methods.
- 90o adiabatic slice selective excitation. Selective adiabatic RF pulses are widely used as 180o inversion and refocusing pulses in magnetic resonance experiments. Significant signal loss is still incurred by the use of non-adiabatic excitation pulses with surface transceivers. A novel selective adiabatic pulse for 90o excitation is being proposed and evaluated to improve the sensitivity of many spectroscopy experiments using surface transceivers
- In vivo 13C isotopomer analysis. 3, 4 - 13C2 glutamate isotopomer is quantitatively linked to the isotopic composition of acetyl-CoA. By measuring the isotopic composition of acetyl-CoA the preference of brain of differently labeled respiration fuels can be determined at a variety of conditions. The cases of 1-13C-glucose and 2-13C-acetate are being evaluated.
PUBLICATIONS
J Shen and DL Rothman (2002)
Magnetic resonance spectroscopic approaches to study neuronal:glial
interactions, Biol. Psychiatry 52, 694-700.
J Shen, DL Rothman, and P Brown (2002)
In vivo GABA editing using a novel doubly selective multiple
quantum filter, Magn. Reson. Med. 47, 447-454.
J Shen (2001)
Effect of degenerate spherical harmonics and a method for automatic shimming of
oblique slices, NMR Biomed. 14, 177-183.
J Shen, KF Petersen, KL Behar, P Brown, TW
Nixon, GF Mason, OAC Petroff, GI Shulman, RG Shulman, and DL Rothman (1999)
Determination of the rate of the glutamate-glutamine cycle in the human brain
by in vivo 13C NMR, Proc. Natl. Acad. Sci. USA 96, 8235-8240 .
J Shen, NR Sibson, G Cline, KL Behar, DL Rothman, and RG Shulman (1998)
15N NMR studies of ammonia transport and glutamine synthesis in the hyperammonemic rat brain, Dev. Neurosci. 20, 434-443
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