Chromium-cage complex as contrast agent in MR imaging--biodistribution studies of the [57Co]cobalt analogue.

The synthesis and T1 and T2 relaxivities of the Cr(III)-(NH2)-Sar-cage complex is reported. An outer-sphere relaxation mechanism is postulated for the relaxivity of the complex. Tissue distribution studies in mice using a [57Co]cobalt analogue as a radioactive tracer showed that the complex is excreted rapidly in the urine. Some renal uptake of the complex is seen. Appreciable uptake of labelled cage complex was observed in 3-methylcholanthrene induced murine rhabdomyosarcoma.