Microvascular Blood Volume Measurement

CEUS was used to measure microvascular blood volume (MBV) as previously described in detail (21 (link)). Repeated high mechanical-index flash/replenishment cycle recordings were made during intravenous infusion of Sonovue microbubble contrast agent (Bracco) and used to estimate changes in thigh MBV between recording periods indicated in Figure 1. Leg blood flow (LBF) was measured by using Doppler ultrasound, with a linear 9- to 3-MHz probe positioned over the origin of the left common femoral artery. LBF was estimated as the product of vessel cross-sectional area and mean velocity over 6 cardiac cycles. Mean LBF was calculated at a time corresponding to each CEUS recording episode on the basis of 3 such recordings made on each of 4 occasions distributed across the study day, as indicated in Figure 1 (i.e., flow during 72 cardiac cycles contributed to a mean leg flow measure). Each individual’s LBF was standardized to his own fasting LBF and normalized to leg lean tissue mass as assessed by DXA (Lunar Prodigy II; GE Medical Systems).