3-10
CELL-DYN
3000 System Operator’s Manual
9140240E — May 1995
Principles of Operation Chapter 3
The orthogonal scatter is directed through a 700 µm slit which blocks the
scatter from the walls of the flow cell. A beam splitter then separates the
orthogonal light scatter into two portions. One portion of the light is
directed to the 90
°
photomultiplier tube (PMT). The remaining light is
directed through a horizontal polarizer. Only light that has changed
polarization (depolarized) can pass through the polarizer to the 90
°
D
PMT. (PMTs are used because relatively little light is scattered at this
high angle.)
The light signals collected by each detector are converted into electrical
signals or pulses. The pulses are digitized based on intensity and sorted
into 256 channels for each angle of light measured.
If a pulse falls above the hardware threshold (channel 23) in the 0
°
detector, the cell counter counts the pulse and stores it for further
evaluation. Pulses that fall below this threshold are not included in the
count and therefore, are not included in the differential. If this raw count
is estimated to be below a predetermined value, the instrument
automatically continues to count WBCs for an extended count period.
The results from the two count periods are averaged.
The information from each detector is collected in list mode. This format
stores the channel information from each of the four dimensions. The
data is then used to determine the differential. Data can be stored in the
list mode format. This data may be reconstructed into scatterplots at any
time or analyzed by different algorithms as revisions are made.
WBC Differential
The light scatter information is graphically presented in the form of dots
on a scatterplot. (Data can also be presented in histograms, which are
operator selectable.) The dots are plotted at a point determined by the
intersection of the channel information designated on the X and Y axes.
For example, if a cell falls in channel 50 on the X axis and channel 50 on
the Y axis, it is plotted at the intersecting point of the two channels.
The scatter information may be plotted in various combinations to yield
different information.
Mononuclear-Polymorphonuclear Separation
The scatter information is plotted with the 90
°
scatter on the Y axis and
the 10
°
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