A computerized analysis of platelet aggregation detected by ultrasound

The purpose of this study was to determine if computerized image processing could be used to characterize platelet aggregation visualized by ultrasound. Citrated whole blood (WB) or platelet-rich plasma (PRP) was imaged with a 12 mHz transducer before and after the addition of adenosine diphosphate. The images were digitized using a 512 x 512 pixel resolution with 256 levels of gray. Raster interference was eliminated by filtering and aggregates were separated from background by gray level discrimination. The results showed that platelet aggregation in PRP can be described by the number of aggregates counted, their sizes or their gray levels. However, aggregation in WB can be detected only by the sizes or gray levels of the aggregates due to the greater echogenicity of ex vivo WB. This methodology, applied to ultrasonic images of brachial arteries and veins, demonstrates that venous particles are common in patients and normal controls, but arterial particles are more common in patients. Differences in the size and brightness of these particles may have prognostic implications.