Fig 3. Comparison between enhanced MR imaging and fluorescent micrograph of the cauda equina.

A and B, Control group. No enhancement of a healthy cauda equina (CE) was found on a gadolinium-enhanced MR image (T1-weighted spin-echo [SE] image, 600/25 [TR/TE]). The cauda equina and epidural root sleeves (ERS) showed moderate signal intensities and the signal intensity was similar to that of muscle in normal conditions (A), EBA emits a bright red fluorescence in clear contrast to the green fluorescence of the nerve tissue. EBA was limited inside the blood vessels, and the blood-nerve barrier was maintained as seen under fluorescent microscopy (B).

C and D, After 1 week constriction.

E and F, After 3 weeks constriction. Clear enhancement was seen inside the cauda equina constricted by a silicon tube (S) as seen on gadolinium-enhanced MR image. No enhancement of epidural root sleeves (ERS) was found on gadolinium-enhanced MR image (T1-weighted spin-echo [SE] image, 600/25 [TR/TE]) (C and E). In the cauda equina, where enhancement was found on MR imaging, EBA emits a bright red fluorescence, which leaked outside the blood vessels, and intraradicular edema was seen under a fluorescent microscope (D and F). BV, blood vessel; CE, cauda equine; ENS, epidural root sleeves; NR, nerve root; RS, root sheath; SS, subarachnoid space.