The MR imaging protocol consisted of an initial T2-weighted sagittal scan of the entire spinal cord. The sagittal images were used to prescribe axial sections of the spinal cord. Next, conventional axial T2-weighted scans were obtained on controls and children with SCI. Finally, DTI images were obtained in the same anatomic location prescribed for the T2-weighted images. The MR imaging parameters for the axial fast spin-echo T2-weighted imaging were as follows: TR = 3500 ms, TE = 124 ms, FOV = 240 mm, 256 × 256, and 2 acquisitions. All the scanning was performed by using a 1.5T Signa scanner (GE Healthcare, Milwaukee, Wisconsin).
DTI was performed by using a single-shot echo-planar diffusion-weighted imaging sequence. The scanner is equipped with a 33-mT/m gradient amplitude with a gradient rise time of 276 μs, which is extremely useful for physiologic imaging like DTI. A standard 8-channel phased-array coil was used for scanning. To determine the diffusion tensor fully, we obtained diffusion-weighted images along 6 different directions with a b-value of 700 s/mm2 as well as an image acquired without diffusion weighting (b = 0 s/mm2). A slab of DTI acquisition consisted of twenty-three 3-mm axial sections with no intersection gaps. In controls, 2 slabs of DTI images were acquired to cover the entire cervical spinal cord (C1-C7). In subjects with SCI, 1 slab of DTI images was acquired with the most central section (section 12) placed in the middle of the injury (2 vertebral bodies above and below the injury based on T2 images and confirmed by a neuroradiologist). This was done to reduce patient discomfort by reducing the overall imaging time spent inside the scanner. Other imaging parameters included the following: TR = 6000 ms, TE = 60 ms, FOV = 240 mm, 128 × 128, and 4 acquisitions. The total imaging time to collect 1 slab of DTI images was approximately 8 minutes. Sedation and/or anesthetic was not administered to the subjects in this study. To test reproducibility of the DTI scans, we brought the patients back within a mean of 34.3 days to the MR imaging center and scanned them a second time. During the second visit, care was taken to position the subjects in the MR imaging scanner in the same anatomic location as those in the first visit. This was performed with the aid of the sagittal image from the first scan for controls and subjects with SCI as well as placement of the first section location at the superior margin of the dens of the C1 vertebral body for controls.
DTI was performed by using a single-shot echo-planar diffusion-weighted imaging sequence. The scanner is equipped with a 33-mT/m gradient amplitude with a gradient rise time of 276 μs, which is extremely useful for physiologic imaging like DTI. A standard 8-channel phased-array coil was used for scanning. To determine the diffusion tensor fully, we obtained diffusion-weighted images along 6 different directions with a b-value of 700 s/mm2 as well as an image acquired without diffusion weighting (b = 0 s/mm2). A slab of DTI acquisition consisted of twenty-three 3-mm axial sections with no intersection gaps. In controls, 2 slabs of DTI images were acquired to cover the entire cervical spinal cord (C1-C7). In subjects with SCI, 1 slab of DTI images was acquired with the most central section (section 12) placed in the middle of the injury (2 vertebral bodies above and below the injury based on T2 images and confirmed by a neuroradiologist). This was done to reduce patient discomfort by reducing the overall imaging time spent inside the scanner. Other imaging parameters included the following: TR = 6000 ms, TE = 60 ms, FOV = 240 mm, 128 × 128, and 4 acquisitions. The total imaging time to collect 1 slab of DTI images was approximately 8 minutes. Sedation and/or anesthetic was not administered to the subjects in this study. To test reproducibility of the DTI scans, we brought the patients back within a mean of 34.3 days to the MR imaging center and scanned them a second time. During the second visit, care was taken to position the subjects in the MR imaging scanner in the same anatomic location as those in the first visit. This was performed with the aid of the sagittal image from the first scan for controls and subjects with SCI as well as placement of the first section location at the superior margin of the dens of the C1 vertebral body for controls.
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