Simultaneous measurement of macro- and microvascular blood flow and oxygen saturation for quantification of muscle oxygen consumption

Purpose: To investigate the relationship between blood flow and oxygen consumption in skeletal muscle, a technique called “Velocity and Perfusion, Intravascular Venous Oxygen saturation and T*₂ ” (vPIVOT) is presented. vPIVOT allows the quantification of feeding artery blood flow velocity, perfusion, draining vein oxygen saturation, and muscle T*₂, all at 4-s temporal resolution. Together, the measurement of blood flow and oxygen extraction can yield muscle oxygen consumption ((Formula presented.)) via the Fick principle. Methods: In five subjects, vPIVOT-derived results were compared with those obtained from stand-alone sequences during separate ischemia-reperfusion paradigms to investigate the presence of measurement bias. Subsequently, in 10 subjects, vPIVOT was applied to assess muscle hemodynamics and (Formula presented.) following a bout of dynamic plantar flexion contractions. Results: From the ischemia-reperfusion paradigm, no significant differences were observed between data from vPIVOT and comparison sequences. After exercise, the macrovascular flow response reached a maximum 8 ± 3 s after relaxation; however, perfusion in the gastrocnemius muscle continued to rise for 101 ± 53 s. Peak (Formula presented.) calculated based on mass-normalized arterial blood flow or perfusion was 15.2 ± 6.7 mL O₂/min/100 g or 6.0 ± 1.9 mL O₂/min/100 g, respectively. Conclusions: vPIVOT is a new method to measure blood flow and oxygen saturation, and therefore to quantify muscle oxygen consumption. Magn Reson Med 79:846–855, 2018.