Retinal flow cytometer tracks circulating blood cells

A retinal flow cytometer developed by researchers from the Wellman Center for Photomedicine at Massachusetts General Hospital and Harvard Medical School (Cambridge, MA) has demonstrated the potential to noninvasively monitor disease progression and enhance treatment by measuring blood flow in the eyes.

Jan 1st, 2008

A retinal flow cytometer developed by researchers from the Wellman Center for Photomedicine at Massachusetts General Hospital and Harvard Medical School (Cambridge, MA) has demonstrated the potential to noninvasively monitor disease progression and enhance treatment by measuring blood flow in the eyes. The in vivo instrument is capable of continuous, real-time monitoring of fluorescently labeled blood cells as they circulate in retinal tissue at the back of the eye, eliminating the need to draw blood samples.

The cytometer improves cell-detection sensitivity by increasing sampling volume. Two phase-locked resonant galvanometer scanners steer the 635 nm beam at a rate of 4.8 kHz, creating a circular scan on the retina. Fluorescence is descanned by the resonant scanning mirrors and detected through a dichroic long-pass filter at 45º and through a 670 nm bandpass filter. A confocal pinhole in front of the photomultiplier tube rejects any out-of-focus signal. In feasibility experiments, the team monitored 1 million circulating cells in a mouse and were able to observe 250 cells/min.

According to the researchers, the ability to count circulating cells is important in diseases like multiple myeloma in which the number of cancer cells in the bloodstream can quickly change over time. The retinal flow cytometer could thus become a valuable tool in the development of better drugs and treatment strategies. Contact Charles P. Lin at lin@helix.mgh.harvard.edu.

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