Broad Stream, Tight Spot
Giacomo Vacca, Ph.D., R&D program manager and research fellow at Abbott Laboratories drew interest with his presentation on laser rastering in flow cytometry. Three features distinguish laser rastering flow cytometry from conventional flow cytometry. First, instead of narrowing the stream of fluid to a single line of cells, the laser-rastering system uses a wide stream with many cells coming through at the same time to increase throughput.
Second, instead of a broad, elongated spot, it uses a tight laser spot in both dimensions. And lastly, instead of a fixed laser beam that waits for cells to flow past, the laser beam is scanned, or rastered, across the core stream as the cells go by, and interacts with each cell multiple times.
Dr. Vacca and his colleagues have been building and perfecting laser rastering flow cytometry at Abbott Hematology for several years with the goal of creating a better hematology analyzer. “We can measure the same things you can in a flow cytometer or hematology analyzer, but at a much greater rate,” he said.
The large amount of complex data does, however, require some “heavy-duty signal processing.” The system can process more than 300,000 cells per second, claims Dr. Vacca, whereas a high-end hematology analyzer can handle only about 10,000 to 20,000 cells per second. One advantage of this higher rate might be to scan for rare events.
One common problem in using a flow cytometer to analyze blood cells is called the coincidence problem. This is when two cells are in the beam at the same time and cannot be resolved. Surprisingly, Dr. Vacca’s laser-rastered system does not have a greater degree of coincidence than a conventional flow cytometer because the wider stream is compensated for by the tighter laser spot.