TIME-COURSE IMAGING OF RAT EMBRYOS IN-UTERO WITH MAGNETIC-RESONANCE MICROSCOPY

Magnetic resonance (MR) microscopy was used to noninvasively investiga te the development of live rat embryos in utero. The difficulty in mak ing sequential observations of a developing mammalian embryo has frust rated developmental biologists for many years. Most current technologi es analyze normal and abnormal development by observing end point phen otypes (in fixed specimens) rather than investigating the live embryo. MR microscopy was adapted to allow rat litters to be scanned three ti mes each (at 1- to 3-day intervals) and has produced images of live de veloping embryos. It was demonstrated that repeated anesthesia and ima ging protocols produced no gross malformations in the rat pups that we re subsequently delivered and observed. Three-dimensional projection e ncoding with phase rewinders produced isotropic (256(3)) image data se ts in about 30 minutes with excellent tissue contrast arising from ste ady-state effects in the amniotic fluid.