Diffusion tensor imaging measurements may help diagnosis of spinal cord trauma

A new technique may help characterize diffusion anisotropy in the spinal cord in a clinical setting. Researchers have determined that using 3D single-shot diffusion-weighted stimulated echo-planar imaging in the cervical spinal cord results in higher resolution and less distortion than 2D single-shot diffusion-weighted echo-planar imaging.

Although diffusion-weighted imaging has been useful to obtain information about the brain, the technique has been little used for the spinal cord, said Dr. Majda Thurnher, a researcher with the Medical University of Vienna.

While MRI has been the modality of choice for detection of spinal cord diseases, it is limited by its high sensitivity and low specificity, she said.

The studies were performed on a 3T system. Three-D single-shot diffusion-weighted stimulated echo-planar imaging (ss-DWSTEPI) was applied to obtain images of a localized volume from the midbrain to the cervical cord of 10 healthy volunteers.

DWI was performed in the sagittal plane with isotropic resolution over seven minutes and 12 slice locations, with b = 0 and 500 sec/mm² along 12 noncollinear diffusion encoding directions and eight magnitude averages at each direction. These diffusion-weighted images were postprocessed using diffusion-tensor imaging analysis software to obtain the fractional anisotropy and to visualize the principal eigenvector and fiber tracts.

Results produced with high-resolution sagittal DTI using 3D ss-DWSTEPI provided contiguous coverage of the spinal cord with shorter echo-train length, and therefore reduced distortion artifact, than those obtained with 2D single-shot diffusion-weighted echo-planner imaging (ss-DWEPI).

DTI measurements in the spinal cord using 3D ss-DWSTEPI may help in the diagnosis and treatment of spinal cord trauma, degenerative and inflammatory conditions, cord demyelination, and tumors.

Clinical applications include the treatment of spinal cord ischemia, multiple sclerosis, HIV myelopathy, transverse myelitis, spondylosis, spinal cord tumors, ependymoma, astrocytoma, hemangioblastoma, ependymoma, and spinal cord injury.

In a related study, 20 healthy volunteers underwent MRI at 3T. Both transverse and sagittal DTI were performed using single-shot spin-echo echo-planar imaging.

Researchers found the fractional anisotropy values of the cervical spinal cord were significantly higher with axial DTI than with sagittal DTI in the central cord. Given the higher standard deviations of fractional anisotropy and apparent diffusion coefficient values with sagittal DTI in all measured regions, axial DTI may provide more accurate values and may be more desirable for comparative studies between patients and healthy controls.

In the comparison of DTI studies, possible differences in DTI metrics due to either axial or sagittal imaging must be taken into account, according to the researchers.