Q.- In the lumbar spine, the SE and
FSE imaging sequences are optimal for evaluating degenerative spine
disorders.Why?
The major reason for the success of SE imaging in the lumbar
spine is that epidural and foraminal fat is abundant and stands out as high
intensity on T1-weighted SE images compared with the relatively lower intensity
of the adjacent thecal sac, herniated disc, or other tissue.
On most T2-weighted GRE and FSE images, the intensity of the
epidural fat is similar to or less than that of CSF and does not always provide
adequate contrast between the other tissues in the spinal canal. This is
especially true in the lumbar neural foramen, where lateral herniated may be
very difficult to visualize on T2-weighted FSE images and the same disc
fragment is obvious on the T1-weighted SE image.
Q.Why is GRE sequence preferred in
imaging of cervical spine?
The epidural space in the cervical and thoracic spine has
little epidural fat. In the cervical spine, contrast is provided by the signal
intensity differences related to the presence of prominent epidural veins and
from CSF in the thecal sac. Therefore, GRE imaging is an important tool in the
cervical spine for defining epidural disease.
In
the cervical and thoracic spine, disc spaces are thinner and the neural
foramina are smaller, so thinner slice thicknesses are necessary. Cervical
spine imaging requires the use of contiguous slices, a factor that favors GRE sequences, because contiguously
acquired conventional SE
scans may be degraded by cross-excitation artifacts
(“cross-talk”) or necessitate very long scan times.
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