Purpose: To investigate the effects of iodinated contrast agents in MRI.
Material and methods: Twenty patients were examined with MRI immediately, 8 and 24 h after lumbar myelography. Signal intensities and calculated T1- and T2-relaxation times of different iodinated contrast agents, a dilution row of iopamidol, and a mixture of CSF and iotrolan were compared with physiological saline solution using different T1- and T2-weighted sequences. 1H-spectroscopy was performed with several solutions containing iodine or other substances.
Results: A fluid-fluid level of the CSF existed in the lumbar dural sac in all patients immediately after lumbar myelography with a non-ionic iodinated contrast agent. Increased signal intensity on T1-weighted and decreased signal intensity on T2-weighted sequences was found for all contrast agents, as well as for the dilution row, compared with physiological saline solution. The structure of the side chains of the contrast agents is responsible for the T1- and T2-shortening effect.
Conclusion: It is important to be aware of the effect of iodinated contrast agents in MRI. To avoid misinterpretation of atypical findings, MRI of the spine should not be performed earlier than 24 h after myelography.