MRI of the postoperative lumbar spine: triple-dose gadodiamide and fat suppression

In ten patients who had undergone lumbar laminectomy, visual assessment of epidural scar enhancement and diagnostic confidence was performed after 0.1 mmol/kg gadodiamide intravenously, again after a further 0.2 mmol/kg, and once more using a fat-suppression sequence. The single-dose contrast-enhanced T1-weighted images showed clear enhancement of epidural scar in eight cases, and clearly improved diagnostic confidence as regards scar and/or disc herniation in six. Triple-dose contrast-enhanced images showed further increase in epidural enhancement clearly in only two cases and marginally in six, with no significant increase in diagnostic confidence. Fat-suppression, performed in eight cases, showed a further clear increase in epidural enhancement in seven cases, but again no increase in diagnostic confidence. In one patient with arachnoiditis contrast enhancement and diagnostic confidence increased only slightly after each contrast injection, and again with the fat-suppression sequence. Increasing contrast medium dose was thus not useful following laminectomy when epidural scarring obscures a possible recurrent disc herniation. Use of fat suppression may, however, permit reduction of the dose of contrast medium necessary to provide adequate scar enhancement.