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Blood=Cell=Counter /131
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
Blood=Cell=Counter /1313
Slide 25
Maintenance Checklist