278 - Hematology flow analyzers: history of continuously evolving technology. Part 2: the optical method
Autor(s): M. Buttarello
Issue: RIMeL - IJLaM, Vol. 2, N. 4, 2006 (MAF Servizi srl ed.)
In flow cytometry the optical method was developed
before the impedance method and the first application
dates back to 1934 by A.Moldavan.
The use of dark field analysis and the introduction of
sheath flow by P.Crosland-Taylor in 1953 represent two
fundamental steps toward obtaining relatively accurate
cell counts.
Following these developments the first commercial
instruments based on optical method to perform the
blood cell counts were produced. Specifically Technicon
(now Bayer) introduced the SMA4A/7A in 1965.
The next decade was characterized by theoretical and
experimental research on the effects of interaction
between narrow light beams (diameters 100-300 µ) and
individual cells while they pass through a flow cell. The
goal was to obtain the greatest amount of information
on cell characteristics. The amplitude of scattered
light collected at narrow angle (forward scatter) was
found to be correlated to cell volume while at greater
angles refraction index and the structural complexity
became more important......