Is a Mixture of Gadolinium and Iodinated Contrast Material Safe During MR Arthrography?

OBJECTIVE: This study was designed to determine whether a mixture of iodinated contrast material and gadopentetate dimeglumine used during MR arthrography yields free gadolinium ion, a systemically toxic metal. MATERIALS AND METHODS: Mixtures of commercially available nonionic and ionic iodinated contrast agent, gadopentetate dimeglumine, lidocaine, and epinephrine were analyzed using a spectrophotometric titration with a gadolinium ion titrant and methyl thymol blue indicator. RESULTS: We found no significant dissociation of gadolinium ion when gadopentetate dimeglumine was mixed with iodinated contrast agents, lidocaine, or epinephrine in any of the dilutions tested. CONCLUSION: Gadopentetate dimeglumine and iodinated contrast material can be mixed before MR imaging without any release of free gadolinium and are therefore safe for confirming the intraarticular placement of contrast material before MR arthrography.