Diffusion tensor magnetic resonance imaging of lesions in multiple sclerosis patients

Multiple sclerosis (MS) is a disease that affects the central nervous system (CNS). Diffusion tensor magnetic resonance imaging (DT-MRI) provides an advanced tool for a quantitative noninvasive technique to detect MS lesions. This technique exploits the sensitivity of MRI to random water diffusion in tissues in the presence of diffusion gradient pulses incorporated into the imaging sequence. Large diffusion weighting is achieved by increasing the magnitude of diffusion pulses; it is essential for the generation of a high SNR diffusion signal. However, large diffusion gradients induce strong eddy currents in the metallic structure of the cryostat, resulting in distortion of MR images. This suggests that moderate diffusion weighting should be optimum for inspection. This study investigates the use of DT-MRI of the brain of human MS patients at a diffusion level of 480 s/mm², which proved to be optimum in a previous study conducted on normal volunteers. MRI studies were performed on a GE 1.5 tesla scanner at Hermann Hospital, Houston, using a single shot diffusion weighted echo planar imaging sequence. All acquisitions were cardiac gated to minimize the effect on the images of cerebrospinal fluid (CSF) pulsation. The presented quantitative results compare various DT-MRI stains for lesion and normal tissue and they reveal that DT-MRI is a powerful noninvasive technique for detecting MS lesions in the human brain.