MR Diskography and CT Diskography with Gadodiamide-Iodinated Contrast Mixture for the Diagnosis of Foraminal Impingement

This study was designed to investigate whether the use of MR diskography would result in improved reader confidence over the use of CT diskography alone for evaluating foraminal impingement causing lumbar radiculopathy. Sixteen disk levels in 14 consecutive patients with suspected foraminal impingement causing lumbar radiculopathy were prospectively included in the study. A mixture of diluted gadodiamide and iodinated contrast material was injected at each disk level. After diskography, a CT scan (CT diskography) and T1-weighted fat-suppressed MR image (MR diskography) were obtained. Two spine radiologists and an orthopedic spine surgeon independently scored CT diskography and MR diskography for foraminal evaluation on a 3-point scale: 1, low confidence; 2, moderate confidence; and 3, high confidence. Each reader also assessed whether MR diskography showed an additional benefit over CT diskography with regard to the depiction of foraminal abnormalities only. Another radiologist reviewed conventional MR images focused on disk height and morphology. The reviewers' confidence scores for MR diskography were superior to those for CT diskography (reader 1, p = 0.00008; reader 2, p = 0.0008; reader 3, p = 0.0015) (p < 0.05). MR diskography was considered beneficial in 13 of 16 disk levels (reader 1), 14 of 16 (reader 2), and 14 of 16 (reader 3). MR diskography increased the confidence scores for the detection of foraminal impingement, especially in cases of severe disk degeneration, but did not show additional benefits in cases of an extensive vacuum in the disk or large disk extrusion. Simultaneous MR diskography and CT diskography with a mixture of gadodiamide and iodinated contrast material may be beneficial for evaluating foraminal impingement causing lumbar radiculopathy.