**5.2.1 Luminal inlet: Concentration**

Because mass transport within the artery's lumen is convection dominated, it would be virtually impossible for drugs to diffuse in the direction opposing blood flow. Therefore it can be assumed that the luminal inlet concentration has a constant value equal to zero. This boundary condition has been used extensively in mass transport studies on DES (Balakrishnan et al., 2008, 2007, 2005; Mongrain et al., 2007, 2005).
