Combined brain imaging using oxygen-17 NMR

¹⁷O NMR spectroscopy enables the simultaneous measurement of cerebral blood flow and metabolic rate of oxygen in small animals, factors which normally require separate experiments to measure. The trick to combining the two procedures lies in the use of ¹⁷O₂ as a tracer for inhalation and measuring the H₂¹⁷O that is produced.

This technique was described for the first time in Magnetic Resonance in Medicine when it was demonstrated on rats. The labelled water molecules can be tracked as a perfusion tracer and their decay rate can be used to determine cerebral blood flow, allowing the non-invasive measurement of both factors within a few minutes. The technique could also be expanded to include measurement of the oxygen extraction fraction which is a third measure of the balance between oxygen supply and metabolism.

The same method will be suitable for studying other organs and will facilitate the study of healthy and diseased brains in vivo.