A new brain-imaging technique where subjects are given small amounts of oxygen and CO2 while being scanned, could give invaluable prognostic data.
The method is a variant of functional magnetic resonance imaging (fMRI). Unlike fMRI, however, it provides true quantitative measurements of, for example, blood flow, that could help in the management of conditions such as stroke.
‘With functional imaging, you can point to an area of the brain and say they’re definitely using that area, the signal has gone up two per cent,’ said Daniel Bulte of Oxford University.
‘But if you’re trying to use that diagnostically, it’s really difficult because you can say: “we’ve fitted the statistics to the signal change, it’s a good fit” and then clinician asks “is the patient going to die?” and you say: “well I don’t know”.’
In the new technique, patients lie in an MRI scanner and breathe gas through a mask. By varying the proportion of CO2 and oxygen, the scientists showed it was possible to use the MRI signal to measure blood flow, blood volume, oxygen use and brain metabolism across the whole brain.
At the moment, the only way of measuring all these parameters at once is with oxygen-15 positron emission tomography (15O-PET). There are only two such facilities in the UK, scans cost around £4,000 each and patients are subjected to radioactive labels.
‘If we can do the same thing, but have it available at every hospital in the country at a fraction of the cost with no radiation, then you can use it for anything — Alzheimer’s, Parkinson’s, MS, traumatic brain injury — anything where you’re interested in seeing what the metabolism in the brain is doing,’ Bulte said.