Figure 1b: Fast spin-echo sagittal images of the dorsal spine. (a) T1-weighted (repetition time msec/echo time msec, 500/20; section thickness, 4 mm) image shows the posterior epidural mass (arrow) has signal intensity similar to that of the spinal cord. The subarachnoid space is obliterated at the level of the mass, and the spinal cord is compressed. Note the normal shape and signal intensity of the vertebrae. (b) T2-weighted (4000/111; section thickness, 4 mm) image shows the mass has mixed signal intensity, with dura mater seen as a dark line (arrow) separating the extradural mass from the intradural structures. High signal intensity within the compressed spinal cord probably represents edema secondary to compression.