Page 636 - Clinical Hematology_ Theory _ Procedures ( PDFDrive )

620 PART 8 ■ Fundamentals of Hematological Analysis

FIGURE 30.2 Cell counting: impedance principles. T e number o pulses on the oscilloscope screen

indicates the number o particles passing through the aperture. T e height (amplitude) o each pulse

ref ects the volume o each cell. A. Histogram distribution o normal erythrocytes. B. Oscilloscope

appearance as erythrocytes pass through the cell counting aperture and produce an electrical resis-

tance. (Adapted rom Pierre R. Seminars and Case Studies: T e Automated Dif erential, Hialeah, FL:
Coulter Electronics, 1985:4, with permission.)

proportional to the number o cells passing through the 4. Orthogonal light scatter 90 degrees. T e result o this

sensing zone in a speci c period. application o light scatter is the production o data based

Te application o light scatter means that as a single cell on ref ection and re raction o internal components,

passes across a laser light beam, the light will be ref ected which correlates with internal complexity.

and scattered. T e patterns o scatter are measured at vari-

ous angles ( orward scatter 180 degrees and right angle 90 Radiofrequency

degrees). Scattered light provides in ormation about cell struc-

ture, shape, and ref ectivity. T ese characteristics can be used In this newer application, high-voltage electromagnetic cur-

to di erentiate the various types o white blood cells (WBCs) rent is used to detect cell size, based on the cellular density.

and to produce scatter plots with a ve-part di erential. T e radio requency (RF) pulse is directly proportional to the
nuclear size and density o a cell. RF or conductivity is related

Characteristics of Light Scatter to the nuclear-cytoplasmic ratio, nuclear density, and cyto-
plasmic granulation.

Optical Light Scatter

In this category, light ampli cation is generated by stimu- Fundamentals of Laser Technology

lated emission o radiation. T ree independent processes are In 1917, Albert Einstein speculated that under certain condi-

operational. T ese are as ollows:
tions, atoms or molecules could absorb light or other radia-

1. Di raction and the bending o light around corners with tion and then be stimulated to shed this gained energy. In the

the use o small angles 1950s, physicists theorized how this borrowed energy could

2. Re raction and the bending o light because o a change in be multiplied and emitted in high quantities. A decade later,

speed with the use o intermediate angles new lasers were developed and used in medical and indus-

3. Ref ection and light rays turned back by the sur ace or an trial applications.

obstruction with the use o large angles T e electromagnetic spectrum ranges rom long radio

waves to short, power ul gamma rays (Fig. 30.3). Within this
Angles of Light Scatter spectrum is a narrow band o visible or white light, which

Various angles o light scatter can aid in cellular analysis. is composed o red, orange, yellow, green, blue, and violet

Tese are as ollows: light. Light ampli ed by stimulated emission o radiation

(LASER) light ranges rom the ultraviolet and in rared spec-
1. Forward light scatter 0 degrees. T is is di racted light, trum through all the colors o the rainbow.

which relates to the volume o the cell.
In contrast to other di use orms o radiation, laser
2. Forward low-angle light scatter 2 to 3 degrees. T is char- light is:

acteristic can relate to size or volume.

3. Forward high angle 5 to 15 degrees. T is type o measure- ■ concentrated,

ment allows or description o the re ractive index o cel- ■ almost exclusively o one wavelength or color,

lular components. ■ the parallel waves travel in one direction.