FUNCTIONAL DESCRIPTIONS
10-2 Sysmex SF-3000 Operator's Manual -- Revised September 1995
2. DETECTION PRINCIPLES
This section describes the flow cytometry by means of semiconductor laser and the DC
(direct current) detection method for blood cell analysis.
2.1 Flow Cytometry by Semiconductor Laser
After a predetermined volume of blood is
aspirated and diluted by a specific amount of
reagent or diluent, it is injected into the flow cell
(conical chamber) being surrounded with front
sheath reagent of a particle-free fluid. This sheath
flow method, also called Hydrodynamic
Focusing, improves cell count accuracy and
reproducibility. Because the blood cells pass
through the center of the flow cell in a single file,
the generation of abnormal cell pulses is
prevented.
Sheath
Nozzle
Blood Cell
Sheath
Reagent
Flow
Cell
Figure 10-1: Flow Cell
When the blood cells are suspended in the diluent pass through the flow cell, the blood
cells are radiated with rays from a laser beam, generating scattered light in intensities
proportional to the size of blood cells. The low-angle (1-6°) scattered light reflects cell
size, and the high-angle (8-20°) scattered light reflects intracellular density (nucleus size
and density). The photo-diodes receive this scattered light and convert it into electrical
pulses.
Data collected on the size of these pulses can be used to draw a 2-dimensional
distribution (scattergram) of blood cell size and intracellular density. Various types of
analysis data can then be obtained from the scattergrams.
Semiconductor
Laser
Condenser Lens
Collimator Lens
Flow Cell
Beam Stopper
High-Angle Scattered Light
Receiver (Photo Diode)
Collector Lens
Sample Flow
Low-Angle Scattered Light
Receiver (Photo Diode)
Figure 10-2: Scattered Light Measurement System
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