A new method of magnetic resonance imaging (MRI) is making brain scans seven times faster than currently possible.
Researchers from Oxford University were part of a international team that developed two improvements in MRI that allow full three-dimensional brain scans in less than half a second, instead of the typical two to three seconds.
This will allow doctors to learn more about the constantly changing dynamics of brain activity, said Professor David Feinberg of the University of California, Berkeley, who led the research.
It could be particularly useful for studying neurologic and psychiatric disorders, such as autism and schizophrenia, which may be brain-connectivity disorders.
‘While it simply is not possible to show the billions of synaptic connections in the live human brain, the hope is that understanding patterns of how the normal brain is functionally interacting and structurally connected will lead to insights about diseases that involve miswiring in the brain,’ said Feinberg.
The technique works on all modern MRI scanners so the impact of the ultrafast imaging will be immediate and widespread at research institutions worldwide, he added.
The faster scans are made possible by combining two technical improvements invented in the past decade that separately boosted scanning speeds two to four times over what was already the fastest MRI technique, echo planar imaging (EPI).
MRI works by using a magnetic field and radio waves to probe the environment of hydrogen atoms in water molecules in the body, which respond differently depending on what kind of tissue they are part of.
Functional MRI is the technique used to scan the brain by looking for areas that are using oxygen and presumably engaged in neuronal activity.
In 2002, Feinberg proposed using a sequence of two radio pulses to obtain twice the number of images in the same amount of time as a traditional MRI scan.
At about the same time, Dr David Larkman of Imperial College London proposed another acceleration technique using multiple magnetic coils.
Both these methods were limited but Feinberg and his colleagues combined these techniques to increase the acceleration further while maintaining the same image resolution.
‘With the two methods multiplexed, 10, 12 or 16 images the product of their two acceleration factors were read out in one echo train instead of just one image,’ said Feinberg said.
The ability to scan the brain in under 400 milliseconds moves functional MRI closer to electroencephalography (EEG) for capturing very rapid sequences of events in the brain.
‘Other techniques which capture signals derived from neuronal activity have much higher temporal resolution; hundred microsecond neuronal changes,’ said Feinberg.
‘But MRI has always been very slow, with two-second temporal resolution. Now MRI is getting down to a few hundred milliseconds to scan the entire brain and we are beginning to see neuronal network dynamics with the high spatial resolution of MRI.’