sentences:  He and his colleagues pioneered the use of H2O17 as a water tracer in MRI and demonstrated that this novel approach could be used to measure brain blood flow.In 1990, the MGH-NMR Center received the first clinical echo planar imaging (EPI) MRI instrument, capable of forming MRI images in 25 ms.The EPI method proved extremely powerful in the study of both perfusion and diffusion by allowing Kwong, and others, to evaluate dynamic changes in signal, such as the flow of blood labeled with injected magnetic contrast agents through the organ systems.