Oxygen-17 contrast agents. Fast imaging techniques.

Under physiologic conditions the stable isotope oxygen-17, in the form of O-17 water, lowers the proton T2 of blood, CSF, tissues, and whole organisms. With MRI the resulting changes in intensity can be detected using spin-echo pulse sequences, but much greater sensitivity is achieved in a fraction of the time with a steady-state free precession sequence such as FISP. With this sequence it is possible to detect levels as low as 0.4% Oxygen-17 water in 53 seconds or less.