Researchers report that a magnetic resonance imaging (MRI) approach called quantitative susceptibility mapping (QSM) may play a key role in diagnosing and tracking the progression of multiple sclerosis (MS) and other neurological diseases. A news release from the Schulick School of Medicine & Dentistry states that QSM is designed to provide a quantitative method to measure myelin content and iron deposition in the brain. Ravi Menon, PhD, led the research, which appears in the Proceedings of the National Academy of Sciences (PNAS).
The release notes that Menon and his colleagues sought to determine whether QSM was quantitative. According to the researchers, the most common approach to creating QSM images was insufficient to generate quantitative images, meaning images in which myelin content and iron can be measured. To demonstrate this, the release says, the researchers explored the orientation of the MRI signal. The team reportedly showed that while this particular signal was conventionally though of as a constant, it depends upon tissue orientation in both cortical grey and white matter, but not in the deep brain structures such as the basal ganglia.
The results suggest that the discordance between the models for QSM using a device that rotated a rat’s brain in order to allow it to be scanned from 18 different angles using a 9.4 T MRI. The researchers say the brains were then sent to histology for comparison. The researchers add that the values depended upon the microstructure of the brain such as myelin concentration and integrity, and iron deposition. The findings indicated a correlation between MRI measurement and histology measurement when the correct model was used.
Menon notes that the methodology now provides a quantitative approach to interpreting myelin and iron concentrations, “and in particular, any changes to them over time. We’ve been doing these scans on MS patients for a while, but nobody knew if it was a valid approach or not. We now know how to interpret the data.”
This ability allows researchers to separate changes in white matter degeneration from other changes, such as iron deposition, Menon adds, which in conventional imaging “all looks the same.”
The next step, Menon says, will be use the new imaging approach to study changes that occur in MS and pinpoint if it is predictive of disease progression.
[Source: Schulich School of Medicine & Dentistry]