Contrast Agents for Tumor Diagnosis in Magnetic Resonance Imaging

Abstract

In order to develop contrast agents for tumor diagnosis in magnetic resonance imaging (MRI) , we investigated the effects of several gadolinium-complexes on T₁ relaxation time of proton in some tissues of Ehrlich solid tumor-bearing mice. L-Aspartic acid, L-glutamic acid, DL-homocysteine, L-glutamyl-glutamic acid, glutathione, sperimidine and ethylenediaminetetrakis (methylenephosphate) (EDTMP) were used as ligands for Gd³⁺.Since each Gd-complex could not be purified except Gd-EDTMP, the mixture of GdCl₃ and a ligand was administered intravenously. Among the compounds tested, the mixture of aspartic acid, glutathione or spermidine with GdCl₃ showed the almost same or above reduction of T₁ relaxation times in the tumor tissue compared with Gd-diethylenetriamine pentaacetic acid (Gd-DTPA) which is used clinically. Furthermore, the contrast-enhancing effect of the three mixtures in the tumor was observed by in vivo T₁-weighted magnetic resonance imaging. The in vivo tissue distribution using radioactive ¹⁵³Gd³⁺ showed that these mixtures mentioned above were also taken up more highly in the tumor than ¹⁵³GdCl₃ itself and ¹⁵³Gd-DTPA, suggesting the formation of Gd-complexes. However, the overall tissue distribution of the mixtures was similar to that of ¹⁵³GdCl₃ because the Gd-complexes were not purified. Gd-EDTMP exhibited the almost same effects with Gd-DTPA as a contrast agent.