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MR contrast enhancement: an experimental study in postlaminectomy epidural fibrosis.

PURPOSE
To measure the effect of contrast medium dose, time elapsed since injection, and maturity of epidural scar tissue on the enhancement 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 obtained exactly correlating histologic sections. Contrast enhancement of scar tissue at 2, 15, 40, and 60 minutes after 0.1 and 0.3 mmol of paramagnetic contrast medium per kilogram was measured. Contrast enhancement was analyzed with respect to the dose of contrast medium, the time of imaging, and the maturity of scar tissue.


RESULTS
Epidural scar tissue enhanced more intensely at 2 and at 15 minutes than at 40 or at 60 minutes. Consistently greater enhancement was observed with the dose 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 did more organized scar tissue.


CONCLUSION
Contrast enhancement in scar tissue can be heightened by increasing the dose of contrast medium from 0.1 to 0.3 mmol/kg and by obtaining images within 15 minutes of injection.