STABLE POLYMERIC MICELLES - LYMPHANGIOGRAPHIC CONTRAST-MEDIA FOR GAMMA-SCINTIGRAPHY AND MAGNETIC-RESONANCE-IMAGING

Rationale and Objectives. Amphiphilic biocompatible polyoxyethylene (P EO)-based polymers form particles (micelles) that are 10-50 nm in diam eter. In the current research, we successfully incorporated amphiphili c indium-111 (In-111) and gadolinium chelates into these particles and used them as particulate contrast media in percutaneous lymphography. Methods. Micelles of amphiphilic PEG-lipid conjugates were loaded wit h In-111 and gadolinium diethylenetriamine pentaacetic acid-phosphatid ylethanolamine (Gd-DTPA-PE) and were injected subcutaneously into the rabbit's paw. Corresponding images of local lymphatics were acquired u sing a gamma camera and a magnetic resonance (MR) imager. Results. The entire lymphatic chain from the paw to the thoracic duct could be vis ualized using In-111 micelles after injection site massage. T1-weighte d MR images of the primary lymph node and collecting vessels were obta ined within 4 min after administration of gadolinium micelles and mass age. Era Conclusion. Polymeric PEG-containing micelles can be loaded w ith diagnostic metals and, on subcutaneous injection, can visualize el ements of lymphatic system. The major fraction of injected micelles st ays within the lymph fluid, thus serving as lymphangiographic agents f or indirect MR or gamma lymphography.