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In vivo 17 O NMR approaches for brain study at high field
Author(s) -
Zhu XiaoHong,
Zhang Nanyin,
Zhang Yi,
Zhang Xiaoliang,
Ugurbil Kamil,
Chen Wei
Publication year - 2005
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.930
Subject(s) - in vivo , nuclear magnetic resonance , chemistry , oxygen 17 , relaxation (psychology) , analytical chemistry (journal) , cerebral blood flow , chromatography , physics , medicine , psychology , social psychology , microbiology and biotechnology , cardiology , biology
17 O is the only stable oxygen isotope that can be detected by NMR. The quadrupolar moment of 17 O spin ( I = 5/2) can interact with local electric field gradients, resulting in extremely short T 1 and T 2 relaxation times which are in the range of several milliseconds. One unique NMR property of 17 O spin is the independence of 17 O relaxation times on the magnetic field strength, and this makes it possible to achieve a large sensitivity gain for in vivo 17 O NMR applications at high fields. In vivo 17 O NMR has two major applications for studying brain function and cerebral bioenergetics. The first application is to measure the cerebral blood flow (CBF) through monitoring the washout of inert H 2 17 O tracer in the brain tissue following an intravascular bolus injection of the 17 O‐labeled water. The second application, perhaps the most important one, is to determine the cerebral metabolic rate of oxygen utilization (CMRO 2 ) through monitoring the dynamic changes of metabolically generated H 2 17 O from inhaled 17 O‐labeled oxygen gas in the brain tissue. One great merit of in vivo 17 O NMR for the determination of CMRO 2 is that only the metabolic H 2 17 O is detectable. This merit dramatically simplifies both CMRO 2 measurement and quantification compared to other established methods. There are two major NMR approaches for monitoring H 2 17 O in vivo , namely direct approach by using 17 O NMR detection (referred as direct in vivo 17 O NMR approach) and indirect approach by using 1 H NMR detection for measuring the changes in T 2 ‐ or T 1ρ ‐weighted proton NMR signals caused by the 17 O– 1 H scalar coupling and proton chemical exchange (referred as indirect in vivo 17 O NMR approach). Both approaches are suitable for CBF measurements. However, recent studies indicated that the direct in vivo 17 O NMR approach at high/ultrahigh fields appears to offer significant advantages for quantifying and imaging CMRO 2 . New developments have further demonstrated the feasibility for establishing a completely noninvasive in vivo 17 O NMR approach for imaging CMRO 2 in a rat brain during a brief 17 O 2 inhalation. This approach should be promising for studying the central role of oxidative metabolism in brain function and neurological diseases. Finally, the similar approach could potentially be applied to image CMRO 2 noninvasively in human brain. Copyright © 2005 John Wiley & Sons, Ltd.