Abstract
Interventional magnetic resonance (MR) using laser fiberoptics is being tested clinically for tumor ablation. The response of MR contrast agents to photothermal exposure in tumors is unknown. This study explores the effect of heating at reduced pH and intense light on release of toxic cations by five different paramagnetic contrast agents. Metal complexes tested include gadopentetate, gadoteridol, gadodiamide, dextran-coated Fe3O4, and manganese tetraphenylporphyrin sulfonate. Methods used were column chromatography assessed by MR and MTT cell toxicity assays after heat, KTP532 laser, or xenon light exposure of the contrast media. Contrast agents heated at pH 4 to 80 or to 121°C did not release free metal ions detectable by MR after chromatography. Photothermal KTP532 laser exposure followed by MTT assays detected toxicity only in the ionic GdDTPA contrast agent. The newer nonionic Gd chelates appear safe for MR-guided laser ablation.
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