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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 T2*” (vPIVOT) is presented. vPIVOT allows the quantification of feeding artery blood flow velocity, perfusion, draining vein oxygen saturation, and muscle T2*, all at 4-s temporal resolution. Together, the measurement of blood flow and oxygen extraction can yield muscle oxygen consumption ( V˙O2) 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 V˙O2 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 V˙O2 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, 2017. © 2017 International Society for Magnetic Resonance in Medicine.

Purpose To determine whole-brain cerebral metabolic rate of oxygen (CMRO2), an improved imaging approach, based on radial encoding, termed radial OxFlow (rOxFlow), was developed to simultaneously quantify draining vein venous oxygen saturation (SvO2) and total cerebral blood flow (tCBF). Methods To evaluate the efficiency and precision of the rOxFlow sequence, 10 subjects were studied during a paradigm of repeated breath-holds with both rOxFlow and Cartesian OxFlow (cOxFlow) sequences. CMRO2 was calculated at baseline from OxFlow-measured data assuming an arterial O2 saturation of 97%, and the SvO2 and tCBF breath-hold responses were quantified. Results Average neurometabolic-vascular parameters across the 10 subjects for cOxFlow and rOxFlow were, respectively: SvO2 (%) baseline: 64.6 ± 8.0 versus 64.2 ± 6.6; SvO2 peak: 70.5 ± 8.5 versus 72.6 ± 5.4; tCBF (mL/min/100 g) baseline: 39.2 ± 3.8 versus 40.6 ± 8.0; tCBF peak: 53.2 ± 5.1 versus 56.1 ± 11.7; CMRO2 (µmol O2/min/100 g) baseline: 111.5 ± 26.8 versus 120.1 ± 19.6. The above measures were not significantly different between sequences (P > 0.05). Conclusion There was good agreement between the two methods in terms of the physiological responses measured. Comparing the two, rOxFlow provided higher temporal resolution and greater flexibility for reconstruction while maintaining high SNR. Magn Reson Med 79:217–223, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Purpose In this work, we compare susceptometry-based oximetry (SBO) and two T2-based methods for estimating resting baseline SvO2 in the superior sagittal sinus (SSS). Methods SBO is a field-mapping technique whereas in T2-based methods the intravascular blood signal is isolated either with velocity-encoded projections [projection-based T2 (PT2)] or a tag-control scheme [T2-relaxation under spin tagging (TRUST)] after T2-preparation. The measurements were performed on twelve healthy subjects (mean age = 33 ± 6 years) at 3 Tesla field strength. The reliability, precision, and reproducibility were examined for the three techniques. Results The mean (± standard deviation) SvO2 quantified by SBO, PT2, and TRUST were found to be 65.9 ± 3.3, 65.6 ± 3.5, and 63.2 ± 4.1%. The standard deviation (SD) for 10 consecutive measurements in the quantified SvO2 was less than 2.7%, 4.7%, and 5.0% for SBO, PT2, and TRUST across all subjects. In testing reproducibility across different days, the resulting SDs were 2.6, 3.5, and 2.0% for SBO, PT2, and TRUST. Conclusion The results indicate that all three SvO2 quantification techniques to be reliable with good agreement between PT2 and SBO while TRUST yielded slightly lower values compared with the other two techniques. Magn Reson Med 73:2122–2128, 2015. © 2014 Wiley Periodicals, Inc.

In this work, we compare susceptometry-based oximetry (SBO) and two T2 -based methods for estimating resting baseline SvO2 in the superior sagittal sinus (SSS).SBO is a field-mapping technique whereas in T2 -based methods the intravascular blood signal is isolated either with velocity-encoded projections [projection-based T2 (PT2 )] or a tag-control scheme [T2 -relaxation under spin tagging (TRUST)] after T2 -preparation. The measurements were performed on twelve healthy subjects (mean age = 33 ± 6 years) at 3 Tesla field strength. The reliability, precision, and reproducibility were examined for the three techniques.The mean (± standard deviation) SvO2 quantified by SBO, PT2 , and TRUST were found to be 65.9 ± 3.3, 65.6 ± 3.5, and 63.2 ± 4.1%. The standard deviation (SD) for 10 consecutive measurements in the quantified SvO2 was less than 2.7%, 4.7%, and 5.0% for SBO, PT2 , and TRUST across all subjects. In testing reproducibility across different days, the resulting SDs were 2.6, 3.5, and 2.0% for SBO, PT2 , and TRUST.The results indicate that all three SvO2 quantification techniques to be reliable with good agreement between PT2 and SBO while TRUST yielded slightly lower values compared with the other two techniques.