Assessing Spinal Cord Compression Using Diffusion Tensor Imaging

Begin with a human participant positioned inside an MRI scanner.

Acquire sagittal and axial images of the cervical spinal cord.

Align the axial positioning line with the sagittal image to minimize imaging errors.

Next, set the MRI for diffusion tensor imaging to visualize the movement of water molecules.

In a healthy spinal cord, water diffusion occurs along the axons, whereas in compressed regions, axonal damage disrupts this directional diffusion.

Acquire images and define spherical regions of interest, excluding cerebrospinal fluid, to reduce artifacts.

Generate color maps based on fractional anisotropy (FA) values, which indicate the directionality of water diffusion, and the apparent diffusion coefficient (ADC) values, which measure overall diffusion magnitude.

Compare these maps of a compressed spinal cord with a healthy one.

In the compressed spinal cord, altered FA map patterns in the region of interest indicate axonal damage, while altered ADC map patterns suggest changes in water diffusion, highlighting spinal cord compression.

Before beginning the imaging procedure, provide earplugs to the participant, and help the participant into a comfortable supine position. Place the head-neck coil over the cervical region and a landmark at the thyroid cartilage level. When the participant is in position, use fast perturbation gradient echo to obtain axial, sagittal, and coronal position maps.

Locate the T2-weighted sagittal plane and copy and paste the sagittal T1-weighted positioning line to the T2-weighted positioning line using the coronal position maps to ensure that the positioning baseline is parallel to the spinal canal. Set the T1 and T2-weighted field of view to 240 by 240 millimeters, the voxel size to 1 by 0.8 by 3 millimeters, the slice gap to 0.3 millimeters, the slice thickness to 3 millimeters, the number of excitation to 2, the fold over direction to feed head, the time of echo of repetition to 10 over 700 milliseconds for the T1-weighted field and 101 over 2,500 for the T2-weighted field.

Then obtain nine sagittal images covering the entire cervical spinal cord, and position the axial positioning line on the sagittal T2W image. Next, cover the intervertebral disk from C2-3 to C6-7, centering on the anteroposterior diameter of the intervertebral space, and set the field of view to 180 by 180 millimeters, the voxel size to 0.7 by 0.6 by 3 millimeters, the slice thickness to 3 millimeters, the fold over direction to anterior/posterior, the number of excitation to 2, and the time of echo /time of repetition to 120 over 3,000 milliseconds.

Then position the axial positioning line on the sagittal T2-weighted image, centering on the anteroposterior diameter of the intervertebral space with 45 slices covering the cervical spinal cord from C1 to C7. To obtain diffusion tensor imaging, use single-shot spin-echo echo-planar imaging with 20 orthogonal directions and non-coplanar diffusion directions, with b-values equal to 800 seconds per millimeters squared.

And set the field of view to 230 by 230 millimeters, the acquisition matrix to 98 by 98, the reconstructed resolution to 1.17 by 1.17, the slice thickness to 3 millimeters, the fold over direction to anterior/posterior, the number of excitation to 2, the echo-planar imaging factor to 98, and the time of echo /time of repetition to 74 over 8,300 milliseconds.

For image post-processing, export the images to the analyzer, and load the T2-weighted sagittal and axial images of the intervertebral space into the filming interface. Locate the most compressed portion of the cervical spinal cord, and load the fractional anisotropy image in the 2-to-1 viewing interface. Click Position Display Series and determine the level of highest compression from the top to the bottom of the location map.

Click File to select the tensor image. Select Neuro 3D Magnetic Resonance to automatically create apparent diffusion coefficient and fractional anisotropy color maps. Advance to the side of the highest compression and use the Start Evaluation mode to create spherical 6-millimeter cubed regions of interest in and around the inner spinal cord to exclude the partial volume effects of cerebrospinal fluid. The fractional anisotropy and apparent diffusion coefficient values will be calculated automatically.