Comparison of VWF and platelet density near the channel wall. VWF staining (A) and Carstairs staining (B) of a SIPA clot in the transverse direction (original magnification, ×10). (C) Normalized intensity level along the red lines in panels A and B. Near the lumen wall, VWF was concentrated and dark, yielding low-intensity levels; whereas the Carstairs-stained platelet was light at the wall, corresponding to a high-intensity level. Black arrows indicate the starting point close to the wall, and blue arrows indicate a pore in the clot.