Diffuse nuclear Overhauser effect MRI contrast changes detected in multiple sclerosis subjects at 7T

Area of Science:

• Neuroimaging
• Biochemistry
• Medical Physics

Background:

• Multiple sclerosis (MS) is a central nervous system inflammatory demyelinating disease affecting ~1 million people in the USA.
• Standard structural MRI is crucial for MS diagnosis and management but lacks metabolic profiling capabilities.
• Ultra-high field 7T MRI enhances signal-to-noise ratio and spatial resolution, enabling advanced sequences like NOE imaging for metabolite analysis.

Purpose of the Study:

• To spatially map differences in lipid metabolites between MS patients and healthy controls using NOE imaging.
• To investigate the potential of NOE imaging to detect metabolic changes in normal-appearing brain matter and lesions.
• To compare NOE imaging findings with conventional T1 maps.

Main Methods:

• Acquired NOE images on 15 MS subjects and 10 healthy controls using a 7T MRI system.
• Utilized a five-pool Lorentzian line fitting model to quantify direct saturation (DS), magnetization transfer (MT), amide proton transfer (APT), amine, and relayed NOE (rNOE) pools.
• Segmented grey matter, white matter, and lesions, and performed correlation analyses between disease duration and lesion load.

Main Results:

• Statistically significant decreases observed in the rNOE pool in normal-appearing white matter (NAWM) (11.4%) and normal-appearing grey matter (NAGM) (10.6%) in MS subjects compared to controls.
• A significant decrease in the amine pool was also found in NAWM (15.3%) in MS subjects.
• Measurable contrast changes in DS, amine, and rNOE pools were detected in MS lesions, which were not visible on T1 maps.

Conclusions:

• NOE imaging reveals diffuse decreases in mobile lipids and proteins in the brains of MS patients, detectable in both normal-appearing and lesioned tissues.
• These metabolic changes identified by NOE imaging are not discernible with conventional T1 mapping.
• NOE imaging offers complementary metabolic information to conventional MRI, with potential for longitudinal disease tracking in MS and other demyelinating diseases.