Increase of signal-to-noise of more than 10,000 times in liquid state NMR.
Extract: Two major applications exist for Nuclear Magnetic Resonance (NMR): spectroscopy and imaging. NMR spectroscopy has gained acceptance as one of the major analytical techniques, due to the detailed information that can be obtained about molecular structure, dynamics and intra- and inter-molecular interactions. Magnetic resonance imaging (MRI) is a non-invasive technique with superior soft tissue contrast and broad diagnostic value. The technique has gained wide clinical acceptance and is of great importance in diagnostic medicine. However, despite significant technological advancements (increasing field strength and cooling of electronics), the application of NMR is limited by an intrinsically low sensitivity, as compared to other analytical methods. Fundamentally, the low sensitivity originates from the low magnetic energy of nuclear spins, compared to the thermal energy at room temperature. At a magnetic field strength of 1.5 Tesla and room temperature, the proton spins are polarized to only 5 parts per million, and an improvement of 200,000 is thus theoretically possible. For other nuclei bearing lower magnetic moments (1/4 for 13C and 1/10 for 15N, respectively, compared to 1H), the theoretical enhancement factor is proportionally greater. The weak nuclear polarization is generally compensated by a high concentration (i.e., a large number of nuclear spins). However, the sensitivity of several other nuclei is further reduced by the low natural abundance of the NMR-active isotope (1.1 % for 13C and 0.36 % for 15N, respectively).
Ardenkjær-Larsen
Jan H
JH
Amersham Health R&D AB, P.A. Hanssonsväg 41, SE-205 12 Malmö, Sweden.
Golman
Klaes
K
Gram
Andreas
A
Lerche
Mathilde H
MH
Servin
Rolf
R
Thaning
Mikkel
M
Wolber
Jan
J