Safety of 4-T MR imaging: study of effects on developing frog embryos.

Fertilized eggs of Rana pipiens (leopard frogs) were exposed to 0.15- or 4.5-T magnetic resonance (MR) imaging and were compared with unexposed fertilized eggs with respect to the percentage of embryos cleaving and percentage of tail buds forming normally. Similarly exposed or unexposed sperm were used to fertilize unexposed eggs, and the same parameters were observed. There was no evidence that MR imaging exposure at 0.15 or 4.5 T had any effect on cleaving embryos or tail bud formation. Since embryogenesis in amphibians is very sensitive to foreign insult, the authors conclude that exposure to a magnetic field of up to 4.5 T has no adverse effect on early development.