Short name: Gd-DTPA-PEG, generic name: Gd-DTPA-PEG polymers, chemical compound: Gadolinium DTPA polyethylene glycol, central moiety: Gd2+, relaxivity: r1=6.0, B0=1.0 T
A substance under development (preclin.) as an intravascular MRI contrast agent for MR angiography and capillary permeability detection.

Short name: PLLGd-DTPA, generic name: (Gd-DTPA)n-polylysine, chemical compound: Gd-DTPA poly(L-lysine-Gd-diethylenetriamine-N,N,N',N'',N''-pentaacetic acid), central moiety: Gd2+, relaxivity: r1=13.1, B0=0.23T
A polymeric MRI contrast agent under development (preclin., Bayer Schering Pharma AG, Berlin, Germany) with advantages in both MRA and in the differential diagnosis of tumors, particularly in perfusion studies of the myocardium and potential in MR lung perfusion. Dozens of the relatively small molecule Gd-DTPA is bound covalently to polylysine, a large molecular weight backbone. The stable, highly water-soluble agent does not diffuse through the endothelium of the vascular system; it is subject to renal elimination.

Perflubron® is a perfluorochemical for use as an oral contrast agent. Due to its insolubility in water it does not mix with intestinal secretions; thus bowel lumina appear homogeneously dark on MR images when Perflubron® replaces bowel contents. Filled bowel loops appear black with all pulse sequences because the contrast agent lacks mobile protons.
It is commercially available as Imagent GI. Because rapid transit through the gastrointestinal tract it reaches the rectum within 30 to 40 minutes in most patients. MR imaging of the upper abdominal region should begin within 15 minutes and of the pelvic region 15 to 60 minutes after ingestion of perflubron.

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Molecular imaging agents may be useful in bimodal imaging - fluorescence and MRI. Bimodal imaging of PBR expressing cells has been possible with Ln-PK-11195, a new imaging agent for the further study of mitochondrial function and its relationship to cancer cell proliferation. By preparing cocktails of both the Gd3+ and Eu3+ or Tb3+ complexes, it will be possible to obtain non-invasive anatomic-scale images by MRI and perform microscopic-scale imaging by fluorescence on the same cell or tissue.
New agents will be created, these include a long circulating bimetallic with enhanced relaxivity for MRI. In-vitro and in-vivo studies will show the safety and efficacy of these molecular imaging agents.

Oral administration of this liposomal encapsulated manganese chloride results in a reduction of the T1 relaxation time causing enhanced signal on T1 weighted MR images. Bracco received marketing approval in December 1997 in the United States, but marketing state is still uncertain.

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