Characterization of platelet adhesion under flow using microscopic image sequence analysis

A method for quantitative analysis of platelet deposition under flow is discussed here. The model systemis based uponperfusion of blood platelets on an adhesive subtrate immobilized over a glass coverslip acting as the lower surface of a rectangular flow chamber. the perfusion apparatus is mountedonto an inverted microscope equipped with epifluorescentillumination and intesified CCD vide camera. Characterization is based on information derived from a specific image analysis method applied to continuous sequences of microscopical images. Platelet recognition across the sequence of images is based on a time-dependent bidimensional, gausssian-like pdf. Once a platelet is located, the variation of its position and shaped as a function of time (i.e., the platelet history) can be determined. Analyzing the history we can establish if the platelet is moving on the surface, the frequency of this movement and the distance traveled before its resumes the velocity of a non-interacting cell. Therefore, we can determine how long the adhesion would last which is correlated to the resistence of the platelet-substrate bond. This algorithm enables the dynamic quantification of trajectories, as well as residence times, arrest and release frequencies for a high number of platelets at the same time. Statstically significant conclusions on platelet-surface interaction can be obtained. An image analysis tool of this kind candramatically help the investigation and characterization of the thrombogenic properties of artificial surfaces such as those used in artificial organs and biomedical devices.