Transcript Multi-channel Cell Counter Utilizing The Aperture Impedance

Multi-channel Cell Counter
Utilizing The Aperture Impedance
Technique
Aaron Lee & Dr. Ash M. Parameswaran
Simon Fraser University
School of Engineering Sciences
Burnaby, B.C. Canada V5A 1S6
Email: [email protected]
This work is sponsored by
Brain Insights, California
Overview
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Introduction
Centralized approach
Clinical facts
Techniques of cell counting
Electrical and physical relationships
Disposable unit design
Conclusion
Thesis Concentration
Construction, modeling and
testing of the disposable unit and
the electronics
Introduction
Most people have blood test at some point
in their lives
Blood is the vital fluid of our body and the
quality of blood is an indication of health
Measured in number of cells per cubic
millimeter of blood
Centralized approach
Most blood cell counting today is done by
sending the blood samples to a centralized
laboratory
Very complex system and required skilled
personnel to operate
Long turn-around time
Patient has to visit another time
Commercial blood cell counter
 18 cell sizes result
and histograms
 Dimensions:
37x47x38(cm)
 Weight: 18 kg net
 Power: AC
 No portable blood
counter in the market
Our challenges
Shortens the turn around time
Reduce the cost so clinics can afford to
own the blood cell counter
Miniaturize the testing equipment
Maintain or improve accuracy
Blood cell sizes and their normal ranges
Blood cell type Sizes Normal Ranges
(um)
(per mm3)
--Male
Female
Red blood cell
6-10
4.5-6.5 M
3.9-5.6 M
White blood cell 10-20
4.5-11 k
4.5-11k
Platelets
2-4
150-350 k 150-350 k
Diseases of the Blood
Cell Type Increase count
 Infectious diseases
WBC
 Inflammatory disease
 Severe emotional
 Physical stress
 Tissue damage
Decrease count
 Bone marrow failure
 Presence of toxic substance
 Disease of the liver/spleen
 Radiation
RBC
 Renal tumor
 Iron overload in organs
 Anemia
 Chronic inflammation
Platelet
 Renal disease
 Infection or inflammation
 Anemia
 Bone marrow failure
 Uremia
 Liver disease
Cell count techniques
Electrical
Optical
Electrical Counting
Gain in precision and reproducibility
Lower coefficient of variation and complete
a large number of determinations quickly
Cost of the electrical cell-counting
equipments ($2500 to over $50,000)
Samples has to be diluted before the
count
Impedance Principle
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Constant current
Insulated chambers
Vacuum pump
Isotonic electrolytes
More on next slide
Electrodes
Constant
Current Source
Vacuum Pump
9% NaCl
Electrolyte
Aperture
Cell
Tube with
Aperture
Container
Direction of
Flow
Impedance Principle (Cont’d)
 Aperture size is 50100um
 “Aperture size: 80 µm for
commercial unit”
 Measure changes in
electrical resistance
 Change in impedance is
proportional to individual
volume
 Accurately counts and
sizes cells
Capacitance Principle
Similar idea as the impedance method
Measured in the function of the change in
capacitance
However, pulse amplitude generated is not
proportional the cell size
Darkfield Optical Principle (Cont’d)
Outlet
Light Source
Beam
Aperture
Inlet
Darkfield
stop disk
Photodiode
Darkfield Optical Principle (Cont’d)
The pulse generated by the system is not
proportional to the size of the cell
Optical detection is sensitive to size of the
dark field stop disk, and the optical
magnification
An offset of the parameters will greatly
affect the amplitude of the signal
Electrical and physical relationships
The pulse height-cell volume relationship
can be calculated by using the Maxwell
equation:
(i   2 )
Voltage  V
2
A
Resistivity of electrolyte
0.9% NaCl used as the electrolyte
Conductivity of aqueous solutions are
usually expressed in Siemens
Conductivity (S/cm) =
Molarity (mol/L) x ion conductance
(SL/cm/eq) x 1 eq/mol
Resistance of the 0.9% NaCl solution is
calculated to be 51 Ω/cm
Coincidence correction
When a particle is in the aperture, and
while the detecting electronics are still
busy processing data, the system cannot
simultaneously measure another cell
Raw _ Count _ Rate
Corrected _ count _ rate 
1  Activity
Design requirements
Cell sizes that we are measuring vary from
2 μm to 20 μm in diameter
Aperture size of 50-100 μm in diameter will
be used
Design of a disposable unit and
electronics that can be put in a portable
cell counter
Cell counter handheld unit
Disposable unit (1st design)
Aperture
To Vacuum
Disposable unit (1st design)
Images of Disposable unit (1st design)
Image of the aperture film under
microscope
Drilled by laser and measured
under electronic microscope
~60um
Conclusion
Theory of multi-channel cell counter
utilizing the aperture impedance technique
have been discussed
Highest resolution available in the industry
for particle counting and size distribution
Color or refractive index does not affect
results
More design on the disposable unit will be
performed and more testing will be done
References
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[1] Basic Principles in Biology by Y.K.To, Hung Fung Book Co.
[2] Haematology, R.B. Thompson
[3] Kubitschek HE: Counting and sizing micro-organisms with the Coulter counter, in Methods in
Microbiology, ed DW Ribbons and JR Norris. London: Academic Press, 1969
[4] Coulter WH: High speed automatic blood cell counter and cell size analyzer. Presented at the
National Electronics Conference, Chicago, October 1956
[5] Hayes TL: The scanning electron microscope: principles and applications in biology and
medicine. Adv Biol Med Phys 12:85, 1968
[6] Brightfield and darkfield: http://www.wsu.edu/~omoto/papers/Fig1.html
[7] Mansberg HP: Optical techniques of particle counting, in Advances in Automated Analysis, Vol
1. Technicon International Congress. New York: Mediad, 1969
[8] Hematology; principles and practice. Edited by Charles E. Mengel, Emil Frei, III [and] Ralph
Nachman.
[9] http://www.principalhealthnews.com/topic/topic100587682
[10] http://www.utmem.edu/physpharm/.010.html
[11] Brecher G et al: Evaluation of an electronic red cell counter. Am J Clin Pathol 16:1439, 1956
[12] Ionic reactions and equilibria. New York : Macmillan, [1967]
[13] http://www.colby.edu/chemistry/CH141B/CH141B.Lab/CH141L4condFall2002.pdf
[14] Practical guide to modern hematology analysers, warren Groner, Elkin Simson, john wiley
and sons ltd, 1995
Questions