Method and apparatus for determining the count per unit volume of particles

Claim 1

A method for accurately determining the count per unit volume of first particles suspended in a fluid containing said first particles having a first index of refraction and at least one second particle having a second index of refraction different from the first index of refraction, comprising the steps of: passing each of said first and second particles from a predetermined volume of suspension fluid, in turn, through a light beam, each of said first and second particles producing, at least one forward light scattering pattern; detecting and counting the combined total number of said first and second particles passing through said light beam from said light scattering pattern; measuring the index of refraction of said second particles above or below a threshold value and counting and determining the volume of said second particles; and correcting the total count and volume of particles by the count and volume of said second particles to determine the count per unit volume of said first particles.

Claim 2

A method for accurately determining the count per unit volume of first particles suspended in a fluid containing said first particles having a first index of refraction and at least one second particle having a second index of refraction different from the first index of refraction, comprising the steps of: passing each of said first and second particles from a predetermined volume of suspension fluid, in turn, through a light beam, each of said first and second particles producing, at least one forward light scattering pattern; detecting and counting the combined total number of said first and second particles passing through said light beam from said light scattering pattern; measuring the index of refraction of said second particles above or below a threshold value and counting and determining the volume of said second particles; and correcting the total count and volume of particles by the count and volume of said second particles to determine the count per unit volume of said first particles.

Claim 3

The method of claim l, wherein the combined total number of said first and second particles is detected by measuring the intensity of light of at least a portion of each of said light scattering patterns, and further including the steps of: determining the volume and index of refraction of each of said first and second particles passing through said light beam from said at least one forward light scattering pattern; and discriminating between said first and second particles by their respective first and second indices of refraction.

Claim 4

The method of Claims 1 or 2, wherein the correcting step includes the steps of: determining the total number and volume of said second particles; determining the count and volume of said first particles passing through said light beam by modifying the combined total count of particles and the predetermined volume of fluid with the number and volume of second particles; and determining the count per unit volume of said first particles from the modified count and volume thereof.

Claim 5

The method of Claims 1 or 2 or 3, wherein said first particles are red blood cells and said second particles are air bubbles, and further including the steps of: aspirating a volume of said fluid from a mixing chamber prior to passing the fluid through the light beam; and mixing the fluid containing red blood cells causing air bubbles to be formed in said fluid prior to aspiration.

Claim 6

The method of any one of the preceding Claims, wherein the step of determining the volume and index of refraction of each of said first and second particles includes the steps of: detecting and measuring the intensity of light within each of a plurality of angular intervals of said scattering pattern to generate a signal from each angular interval, wherein said angular intervals are selected such that the light contained therein contains sufficient information for the precise determination of the volume and index of refraction of said first and second particles; and determining the volume and index of refraction of said first and second particles from the magnitudes of said signals.

Claim 7

The method of any one of Claims 2-5, wherein the discriminating step includes the step of providing a two-dimensional graphical representation depicting a first region of particles having said first index of refraction and a second region of particles having said second index of refraction.

Claim 9

An apparatus for accurately determining the count per unit volume of first particles suspended in a fluid containing said first particles having a first index of refraction and at least one second particle having a second index of refraction different from the first index of refraction comprising: means (16) for passing each of said first and second particles from a predetermined volume of suspension fluid in turn, through a light beam, each of said first and second particles producing at least one forward light scattering pattern; means (20,22) for detecting and counting the combined total number of said first and second particles passing through said light beam from said light scattering pattern; means (24,26) for measuring the index of said second particles above or below a threshold value and counting and determining the value of said second particles; and means (28) for correcting the total count and volume of particles by the count and volume of said second particles to determine the count per unit volume of said first particles.

Claim 10

An apparatus for accurately determining the count per unit volume of first particles suspended in a fluid containing said first particles having a first index of refraction and at least one second particle having a second index of refraction different from the first index of refraction comprising: means (16) for passing each of said first and second particles from a predetermined volume of suspension fluid in turn, through a light beam, each of said first and second particles producing at least one forward light scattering pattern; means (20,22) for detecting and counting the combined total number of said first and second particles passing through said light beam from said light scattering pattern; means (24,26) for measuring the index of said second particles above or below a threshold value and counting and determining the value of said second particles; and means (28) for correcting the total count and volume of particles by the count and volume of said second particles to determine the count per unit volume of said first particles.

Claim 12

The apparatus of Claims 8 or 9 wherein the correcting means (28) includes: means for determining the total number and volume of said second particles; means for determining the count and volume of said first particles passing through said light beam by modifying the combined total of particles and the predetermined volume of fluid with the number and volume of second particles; and means for determining the count per unit volume of said first particles from the modified count and volume of said first particles.

Claim 13

The apparatus of any one of Claims 8-10 further including means for aspirating a predetermined volume of fluid from a mixing chamber, and wherein the first particles are blood cells and the second particles are air bubbles and further including means for mixing the fluid containing blood cells causing air bubbles to be formed in said fluid.

Claim 14

The apparatus of any one of Claims 8-11 wherein said discriminating means (26) includes a means for providing a two dimensional graphical representation showing a first region of particles having said first index of refraction and a second region of particles having said second index of refraction, and wherein said correcting means (28) includes counter means for counting those particles above and below a threshold index of refraction and an adding means for determining the total volume of particles counted by said counting means.

Claim 15

The apparatus of any one of Claims 8-12 further including a microprocessor (28) for calculating the mean volume per second particles to determine the total volume of said second particles and calculating the count per unit volume of said first particles.

Claim 16

The apparatus of any one of Claims 8-13 wherein said volume and index of refraction determining means (24) includes: means for detecting and measuring the intensity of light within each of a plurality of angular intervals of said scattering pattern and for generating a signal from each angular interval wherein said angular intervals are selected such that the light contained therein contains sufficient information for the precise determination of the volume and index of refraction of said particle; and means responsive to said det ecting and measuring means for determining the volume and index of refraction of said particle from the magnitudes of said signals.