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Slide 1

BLOOD CELL COUNTERS

Slide 2

Blood cell counter

The blood cell counter count the number of RBC or WBC per unit of volume of blood using either of two method:

Electrical method called aperture impedance change

Optical method called flow cytometry

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Slide 3

Electrical method:Aperture impedance change

When blood is diluted in the proper type of solution, the electrical resistivity of blood cells (ρc) is higher then the resistivity of the surrounding fluid (ρf)

By a measurement arrangement these resistivities can be differentiated from each

other

we can count cells

Slide 4

External Electrode

ApertureInternal Electrode

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Slide 5

Aperture impedance change measurementBlood cell sensing

The sensor consists of a two-chamber vessel in which the dilute incoming blood is on one side of barrier, and the waste blood to be discarded is on the other

A hole with a small diameter (50μm) is placed in the partition between the tow halves of the cell

Ohmmeter measures the change of resistance when blood cells pass through the aperture

Vessel

Chamber 1 Chamber 2

Aperture

Slide 6

Aperture impedance change measurementBlood cell sensing

Two electrodes from the ohmmeter are placed each in one chamber

Resistance of the path through the hole is measured

When blood cell is in the aperture

R=(ρfluid x L)/A R: resistivity of ohmmeter [ohm] Ρfluid: resistivity of fluid [ohm-cm] L: length of the path [cm] A: cross-sectional area of aperture [cm2]

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Slide 7

Aperture impedance change measurementBlood cell sensing

The change in resistance when a blood cell passes through the aperture is described by:

K: ratio of the aperture resistance to its volume

v: volume of the sphere (e.g., blood cell)

X: ratio of cross-section of sphere to that of the aperture

Slide 8

Coulter Counter

Constant current source (CCS) and voltage amplifier replace the ohmmeter

RA is the resistance of the aperture and will be either high or low, depending on whether or not the blood cell is inside the aperture

Amplifier convert the current pulse to voltage pulse

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Slide 9

ExternalElectrode

ApertureInternal Electrode

U = R x I

Slide 10

Time [sec]

Pulse Picture

Volume [fl]

Pulses / Volume

Blood suspension

TransducerStart-Sensor Stop-Sensor

Manometer

Counting Time(defined Volume)

Prerun Afterrrun

DC Detection MethodAbsolute Counting I

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Slide 11

Block diagram of an

impedance aperture cell counter

A1o/pTD & Osc.vert.

TDo/pA2o/p

A2o/p Dig. C. &Osc.horiz.

Controlo/pOsc.trig.& Dig.C.

Coulter Counter

Slide 12

scan

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Slide 13

Threshold detector

i/p>2.5V o/p=5V

i/p<2.5V o/p=0V

Slide 14

Block diagram of theThreshold detector

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Slide 15

Blood cell counter usually consists of three parts:

1- Electrical part which includes power supply, WBC and RBC preamplifier and amplifier boards, microprocessor boards, interface boards and other electrical components

2- Pneumatic supply that provides compressed and vacuum air which is needed for different parts of counter to work

3- Diluents part which includes all the components necessary to aspirate the whole blood sample, dilute it and measure the cells of the blood depending on electrical conductivity

Slide 16

Flow cytometry cell countersOptical flow cytometry sensing

The optical cytometrysensor consists of a quartz sensing sheath designed with a hydrodynamic focusing

region cell path region that passes

only a single cell at time.

Focusing is done by decreasing the diameter of the aperture.

Light source is (He-Ne) Laser

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Slide 17

Flow cytometry cell countersoptical flow cytometry sensing

Two Photodetectors(photosensors) Photodetector A detects

forward scatted light Photodetector B detects

orthogonal scatted light

Blood sample enters the analyzer Optical counter → WBC

count Colorimeter → hemoglobin Optical flow sensor → RBC

count

Slide 18

Maintenance

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Slide 19

1.External Check

Is there enough reagent for routine daily analyses?

Enough printing-paper?

Tubing and wiring connected correctly?

Sampler* ready?(*optional)

Waste container empty?

Slide 20

Maintenance

2. Switch on the instrument– Main switch at the instrument.

3. Auto-rinse sequence is performed– Automatic background check

4. Instrument goes into READY status.

5. Measure control material

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Slide 21

Maintenance

6. Standby mode (only if available)– If you do not use the analyser for a certain period of time the

system will go automatically into the “standby” mode. Recovering by pressing START button.

7. Execute shut down sequence – Press SHUT DOWN / END.

– Put CELLCLEAN under aspiration pipette. (for K-4500 press 1). After the ready indication is turned off and a peep signal sounds 3 times remove the CELLCLEAN. The system performs automatic rinse cycles and the message “Turn Power Off” will be announced.

– Turn the Analyser off.

Slide 22

Maintenance

Daily: Clean transducer and manometer

Program: ”Shut Down" Check trap chambers and remove water

Weekly: Clean tray Clean waste chamber

Program: ”clean waste chamber” (*if available) approx. 20 min

Monthly: Clean orifice Clean WBC/RBC-aperture

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Slide 23

Maintenance

If necessary: Clean sample rotor valve

Clean rinse cup mechanism

Remove aperture cloggingProgram: ”clog removal"

Remove obstinate clogs at apertures.Program: “drain sample”Clean aperture manual with transducer glass-fibre brush and Cellclean.

Slide 24

Maintenance Checklist

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Slide 25

Maintenance Checklist