 In 1971, there was the first report of the difference of the relaxation times for water in myocardium and pure water in spin-echo NMR by Hazlewood and Chang.This difference forms the physical basis of the image contract between cells and extracellular fluid.In 1973, the first simple NMR image was published and the first medical imaging in 1977, entering the clinical arena in the early 1980s.