MR CONTRAST ENHANCEMENT - AN EXPERIMENTAL-STUDY IN POSTLAMINECTOMY EPIDURAL FIBROSIS

PURPOSE: To measure the effect of contrast medium dose, time elapsed s ince injection, and maturity of epidural scar tissue on the enhancemen t of scar tissue in MR imaging. METHODS: We imaged 12 beagle dogs with MR at 10 to 60 days after lumbar laminectomy, and at necropsy we obta ined exactly correlating histologic sections. Contrast enhancement of scar tissue at 2, 15, 40, and 60 minutes after 0.1 and 0.3 mmol of par amagnetic contrast medium per kilogram was measured. Contrast enhancem ent was analyzed with respect to the dose of contrast medium, the time of imaging, and the maturity of scar tissue. RESULTS: Epidural scar t issue enhanced more intensely at 2 and at 15 minutes than at 40 or at 60 minutes. Consistently greater enhancement was observed with the dos e of 0.3 mmol/kg than with the dose of 0.1 mmol/kg. Regions of loosely organized scar tissue enhanced less intensely and less quickly than d id more organized scar tissue. CONCLUSION: Contrast enhancement in sca r tissue can be heightened by increasing the dose of contrast medium f rom 0.1 to 0.3 mmol/kg and by obtaining images within 15 minutes of in jection.