QUANTITATIVE CONTRAST-ENHANCED MR-IMAGING OF THE OPTIC-NERVE

During the acute stages of optic neuritis damage to the blood-optic ne rve barrier can be detected using i.v. paramagnetic contrast-enhanced MR imaging. Quantification of the enhancement pattern of the optic ner ve, intraorbital fat and muscle was determined in 15 normal subjects u sing 3 fat-suppression MR imaging methods: T1-weighted spin-echo and s poiled gradient-echo sequences preceded by a fat-frequency selective p ulse (FATSAT + SE and FATSAT + SPGR, respectively) and a pulse sequenc e combining CHOPPER fat suppression with a fat-frequency selective pre paration pulse (HYBRID). Pre- and postcontrast-enhanced studies were a cquired for FATSAT + SE and FATSAT + SPGR. There was no significant en hancement of the optic nerve by either method (mean increase of 0.96% and 5.3%, respectively), while there was significant enhancement in mu scle (mean 118.2% and 108.2%, respectively; p<0.005) and fat (mean inc rease of 13% and 37%, respectively; p<0.05). Postcontrast optic nerve/ muscle signal intensity ratios (mean, SD) were 0.51 (0.07), 0.58 (0.05 ) and 0.75 (0.05) for FATSAT + SE, FATSAT + SPGR and HYBRID, respectiv ely. These results suggest a practical methodology and range of values for normal signal intensity increases and ratios of tissue signal tha t can be used as objective measures of optic neuritis for natural hist ory studies and treatment trials.