PN 177196BB
7-13
DATA MANAGEMENT AND REVIEW
DATA ANALYSIS - MEASUREMENT PRINCIPLES
7
6. Absorbance readings are taken on the cytochemically treated WBCs in the optical
window of the flow cell.
a. As a cell passes through the optical portion of the flow cell, light is scattered in all
directions.
b. Sensor detects only forward scattered light.
c. Optical measurement is derived as a function of the amount of light lost due to
diffraction and absorbance, as compared to full transmission when no cell is
present.
7. Collected signals are converted into voltage pulses and are processed.
a. Signals from the flow cell aperture and from the optical measurement are correlated
by a window of time.
a. The optical pulse must be detected within 100 to 300 microseconds of the
impedance pulse; otherwise, the signal is rejected.
8. Output signals from the focused flow impedance and the light absorbance measurements
are combined to define the WBC differential population clusters: lymphocytes,
monocytes, neutrophils, and eosinophils, and their precursors.
a. The magnitude of the voltage pulses are proportional to the physical and chemical
characteristics of the cells being analyzed.
b. The light absorbance is related to cellular contents (granularity, nuclear content,
and so forth) after cytochemical staining.
Cell Measurement Components in Flow Cell
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