Vascular reactions to laser in vivo

Platelet aggregates form in arterial vessels following exposure of the vessels to a single pulse ruby-red laser beam. Usually, a small cluster of red blood cells occupies the center of the aggregate. It appears that endothelial damage is not required for the platelet aggregation, but that platelet activity is initiated by rupture of red blood cells, possibly through the release of ADP from the injured red cells. Also, no shape change is noted in platelets that adhere to the vessel wall or to each other.