We present a novel blood flow-enhanced-saturation-recovery (BESR) sequence, which allows rapid in vivo T1 measurement of blood for both 1H and 19F nuclei. BESR sequence is achieved by combining homogeneous spin preparation and time-of-flight image acquisition and therefore preserves high time efficiency and signal-to-noise ratio for 19F imaging of circulating perfluorocarbon nanoparticles comprising a perfluoro-15-crown-5-ether core and a lipid monolayer (nominal size = 250 nm). The consistency and accuracy of the BESR sequence for measuring T1 of blood was validated experimentally. With a confirmed linear response feature of 19F R1 with oxygen tension in both salt solution and blood sample, we demonstrated the feasibility of the BESR sequence to quantitatively determine the oxygen tension within mouse left and right ventricles under both normoxia and hyperoxia conditions. Thus, 19F BESR MRI of circulating perfluorocarbon nanoparticles represents a new approach to noninvasively evaluate intravascular oxygen tension. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.