Combined measurement of perfusion, venous oxygen saturation, and skeletal muscle T-2* during reactive hyperemia in the leg

Background: The function of the peripheral microvascular may be interrogated by measuring perfusion, tissue oxygen concentration, or venous oxygen saturation (SvO(2)) recovery dynamics following induced ischemia. The purpose of this work is to develop and evaluate a magnetic resonance (MR) technique for simultaneous measurement of perfusion, SvO(2), and skeletal muscle T-2*. Methods: Perfusion, Intravascular Venous Oxygen saturation, and T-2* (PIVOT) is comprised of interleaved pulsed arterial spin labeling (PASL) and multi-echo gradient-recalled echo (GRE) sequences. During the PASL post-labeling delay, images are acquired with a multi-echo GRE to quantify SvO(2) and T-2* at a downstream slice location. Thus time-courses of perfusion, SvO(2), and T-2* are quantified simultaneously within a single scan. The new sequence was compared to separately measured PASL or multi-echo GRE data during reactive hyperemia in five young healthy subjects. To explore the impairment present in peripheral artery disease patients, five patients were evaluated with PIVOT. Results: Comparison of PIVOT-derived data to the standard techniques shows that there was no significant bias in any of the time-course-derived metrics. Preliminary data show that PAD patients exhibited alterations in perfusion, SvO(2), and T-2* time-courses compared to young healthy subjects. Conclusion: Simultaneous quantification of perfusion, SvO(2), and T-2* is possible with PIVOT. Kinetics of perfusion, SvO(2), and T-2* during reactive hyperemia may help to provide insight into the function of the peripheral microvasculature in patients with PAD.