Fig. 3.

Schematic illustration of a “complete model” describing three parallel processes of the ¹⁷O-labeled metabolic water (H₂¹⁷O) occurring in the brain when the ¹⁷O-labeled oxygen gas molecules are introduced via an inhalation. In this model, only the metabolic H₂¹⁷O is considered because the ¹⁷O-labeled O₂ is invisible by in vivo ¹⁷O NMR. C_a(t), C_b(t) and C_v(t) stand for the H₂¹⁷O concentration in arteriole, brain tissue and venule, respectively, as a function of the ¹⁷O₂ inhalation time.