CONTRAST-MEDIA OF HIGH AND LOW-MOLECULAR WEIGHTS IN THE DETECTION OF RECURRENT HERNIATED DISKS

PURPOSE: Our goal was to compare contrast enhancement of recurrent her niated disk fragments and scar after intravenous injection of a new hi gh-molecular-weight contrast medium, Gadomer 17 (gadomer), with that a fter injection of a low-molecular-weight contrast medium, (gadopenteta te dimeglumine), METHODS: Recurrent herniated disks were modeled in do gs by placing a fragment of intervertebral disk cartilage in the epidu ral space at laminectomy. MR imaging was performed with one of the con trast media at 20 and 50 days and with the other medium at 22 and 52 d ays, The changes in signal intensity from baseline in the disk fragmen t and in the adjacent scar tissue was measured at 2, 22, and 45 minute s. Differences were tested for significance with a student t-test, RES ULTS: At 50 days after surgery, signal intensity in the intervertebral disk fragment increased by an average of 0.52 at 2 minutes after inje ction of gadomer and by an average of 0.90 after injection of gadopent etate. For scar, the increases in signal intensity were 1.41 (gadomer) and 1.62 (gadopentetate), At 22 and 45 minutes after injection, the s ignal intensity change in the disk fragment continued to be significan tly greater after gadopentetate than after gadomer injection. In compa rison with the changes at 50 days, both scar and disk fragment tended to show greater signal intensity changes at 20 days. Signal intensity changes in the disk fragments were significantly less after gadomer th an after gadopentetate. Signal intensity changes in scar were slightly less with gadomer than with gadopentetate, CONCLUSION: Greater contra st is achieved between scar and recurrent herniated disk with a higher -molecular-weight contrast medium than with one of lower molecular wei ght. The difference between the high-and low-molecular-weight contrast media increases with maturation of the scar tissue.