Researchers in the UK have invented a new way of boosting the sensitivity of nuclear magnetic resonance (NMR) measurements by a factor of 1000. The technique involves mixing molecules of interest with a “spin isomer” of hydrogen and a metal hydride, which forces the nuclear spins of the sample into a specific energy state. This makes the molecules much more visible to NMR measurements as well as magnetic resonance imaging (MRI), which uses NMR to map different tissue types within the body.
According to the researchers, led by Simon Duckett and Gary Green from the University of York, molecules that have been treated in this way could someday be injected into the body, reducing the time to take an MRI image from hours to a fraction of a second. This, they say, could allow medical researchers to watch how a patient responds in real time to drug therapy. It could also allow larger and more detailed scans to be made — allowing doctors to see tumours earlier than possible today (Science 323 1708).
NMR measurements are made by exposing a sample to a very high magnetic field, which aligns the magnetic moments of its nuclei in a specific direction. The magnetic energy levels are quantized, and the spacing between the levels — as well as the time it takes for transitions between those levels — can be measured by applying a radio-frequency signal to cause a transition and then measuring the radio signals that are given off as the magnetic moments return to equilibrium. This provides a wealth of information about the chemical and structural composition of the sample.
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