Figure 7
Hematocrit exerts a significant influence on the relationship between Ve and the partition coefficient, λ. Ve (expressed as a percentage) is defined here as the following: Ve = [λ · (1-hematocrit) · ρ] - Vp where Ve is the myocardial extravascular extracellular volume fraction, ρ is the specific density of myocardial tissue (1.05), Vp is the myocardial plasma volume fraction (assumed to be a constant 0.045, reflecting capillary density), and λ=[ΔR1myocardium]/[ΔR1bloodpool] expressed as a decimal). Since anemia is common in various conditions (e.g., heart failure), obtaining the hematocrit is essential for accurate Ve measurement. Panel A shows how λ will vary nonlinearly with the hematocrit for a range of Ve values. Similarly, panel B shows how Ve will vary inversely with the hematocrit for a range of λ values.