In addition to common day usage as an intravenous contrast agent for magnetic resonance imaging, Gadopentetate Dimeglumine has been used in joint arthrography. There have been no reports of its use as an intradiscal contrast agent for MRI-discography. This study was performed to compare the reliability and utility of discogram-CT scans to discogram-MRI scans.
Methods
28 discs in eight patients were studied utilizing posterior lateral approach for lumbar and anterior lateral approach for cervical discography. Water soluble iodinated contrast agent premixed with Gadopentetate Dimeglumine in a concentration of 3mg/cc of iodinated contrast. Immediate post discogram AP and lateral radiographs, CT scans and T1 weighted MRI scans in three planes were performed. Two spine specialist neuroradiologists interpreted the results of each disc level, blinded to the patient's name and the results of other studies. Interobserver variability was determined for the two neuroradiologists and interscan variability was determined for MRI-discogram and CT-discogram. The following parameters were studied: Normal vs. abnormal, annulus fissures, annulus attenuation, disc herniations and contrast leakage.
Results
1) Interobserver variability was lower for CT discography than for MRI discography (.86 to .68) in simply deciding whether a disc was normal or abnormal. MRI discography variability was lower than CT discography variability in the diagnosis of herniated disc (.93 to .76). Annulus attenuation was less variable with CT discography than MRI discography (.93 to .68).
2) Interscan variability: There was similarity in variability of CT discogram and MRI discogram for each level by each neuroradiologist in detecting normal vs. abnormal (.86 for both). Similarly, presence or absence of fissures between scans varied .71 and .76 by the two neuroradiologists. Disc herniation detection between scans varied .86 and .76. In general, one neuroradiologist felt CT-discogram was slightly superior and the other felt MRI-discogram was slightly superior.
Conclusion
Interobserver variability as a measure of diagnostic efficacy of CT discography and MRI discography indicates the two techniques are both effective. CT discography may be better for detection of overall normality and MRI discography may be better for disc herniations. MRI scan is advantageous because it obviates radiation exposure; CT scan is advantageous in patients with claustrophobia. |
