multi channel cell counter utilizing the aperture impedance technique
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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 Introduction

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multi channel cell counter utilizing the aperture impedance technique

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
Overview
  • Introduction
  • Centralized approach
  • Clinical facts
  • Techniques of cell counting
  • Electrical and physical relationships
  • Disposable unit design
  • Conclusion
thesis concentration
Thesis Concentration

Construction, modeling and testing of the disposable unit and the electronics

introduction
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
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

Commercial blood cell counter
our challenges
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
cell count techniques
Cell count techniques
  • Electrical
  • Optical
electrical counting
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

Constant Current Source

Vacuum Pump

Electrodes

9% NaCl Electrolyte

Aperture

Tube with Aperture

Cell

Direction of Flow

Container

Impedance Principle
  • Constant current
  • Insulated chambers
  • Vacuum pump
  • Isotonic electrolytes
  • More on next slide
impedance principle cont d
Aperture size is 50-100um

“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

Impedance Principle (Cont’d)
capacitance principle
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

Photodiode

Darkfield stop disk

Inlet

Darkfield Optical Principle (Cont’d)
darkfield optical principle cont d16
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
Electrical and physical relationships
  • The pulse height-cell volume relationship can be calculated by using the Maxwell equation:
resistivity of electrolyte
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
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
design requirements
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
image of the aperture film under microscope
Image of the aperture film under microscope

Drilled by laser and measured under electronic microscope

~60um

conclusion
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
References
  • [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
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