Here’s another interesting story from MIT Technology Review which is profiling three new imaging modalities that can help physicians diagnose mild brain damage that is typically invisible to standard CT and MRI scans:
Scientists hypothesize that mild head trauma damages the brain’s white matter–the long projections, called axons, that ferry messages between neurons. White matter is invisible to CT scans and magnetic resonance imaging (MRI). One of the most promising techniques for detecting subtle brain injury, called diffusion tensor imaging (DTI), is a variation of MRI that tracks water molecules in the brain’s white matter. In research presented this week at the Society for Neurosciences conference in Washington, DC, Brody and his colleagues found that DTI analysis of brain-injury patients revealed signs of white-matter damage not visible with normal MRI. The damage seemed to correlate with cognitive deficits, including slowed reaction time.
A second variation of MRI, known as magnetic resonance spectroscopic imaging (MRSI), can analyze the spectral frequencies of chemicals in the body. Andrew Maudsley and his colleagues at the University of Miami have used new advances in MRI technology, including higher-power magnets, to develop MRSI methods that can measure concentrations of two chemicals in the brain: n-acetylaspartate (NAA), a marker of white-matter density, and choline, which has been linked to injury. Previous MRSI methods yielded information only about specific brain regions, but the new technique can measure chemical concentrations across the whole brain. The researchers found decreases in NAA, possibly due to damaged axons, and increases in choline in a group of 25 patients with traumatic brain injury. “We see widespread metabolic changes, even in those with the mildest injuries,” says Maudsley, who presented the work at the conference.
A third study presented at the conference found that changes to slow-wave activity, which have been previously linked to traumatic brain injury, are likely caused by damage to the white matter. Mingxiong Huang and his colleagues used magnetoencephalography (MEG), which measures the magnetic fields produced by the electrical activity of nerve cells, to pinpoint the source of abnormal brain activity, and they discovered that it often overlapped with the location of damage detected using DTI.