A Measurement Setup for Direct 17O MRI at 7 T

An efficient breathing system was designed for direct O-17 MRI to perform oxygen metabolism studies of the human brain. The breathing system consists of a demand oxygen delivery device for O-17(2) supply and a custom-built re-breathing circuit with pneumatic switching valve. To efficiently deliver the O-17 gas to the alveoli of the lungs, the system applies short gas pulses upon an inspiration trigger via a nasal cannula. During and after O-17(2) administration, the exhaled gas volumes are stored and filtered in the re-breathing section to make the most efficient use of the rare O-17 gas. In an inhalation experiment, 2.2 +/- 0.1 L of 70%-enriched O-17(2) were administered to a healthy volunteer and direct O-17 MRI was performed for a total imaging time of 38 min with a temporal resolution of 50 s per 3D data set. Mapping of the maximum signal increase was carried out showing regional variations of oxygen concentration of up to 30% over the natural abundance of O-17 water. Magn Reson Med 66: 1109-1115, 2011. (C) 2011 Wiley-Liss, Inc.