Abstract: A displacement pump comprising a pump assembly and a cassette assembly. The pump assembly includes upper and lower housing portions that define a cavity, an arm disposed in the cavity, a roller attached to the distal end of the arm, and a motor attached to the proximal end of the arm for rotating the arm. The cassette assembly is removably disposed in the cavity and comprises upper and lower cassette housing portions that form an annular compression surface with a channel therein. A hollow compression tube having a flange extending along a length thereof is secured to the compression surface by the flange being engaged with the channel. As the motor rotates the roller arm, the roller presses the compression tube against the compression surface to create a moving occlusion of the compression tube for pushing fluid through the compression tube.

Abstract: Most automatic particle classification methods produce errors. The invention provides a method for improving the accuracy of particle classification while shortening the amount of manual review time required from the operator. The method uses class weights, which are statistically-derived correction factors that accounts for frequency of classification errors. A first class weight and a second class weight are assigned to the first class and the second class, respectively. The number of particles in each of the first and the second classes is multiplied by the first class weight and the second class weight, respectively, to generate a corrected number of particles in each of the classes. If particles are reclassified, the class weights are recalculated in response to the reclassification. The method is usable with a complete classification where all the particles in a sample are classified, or a selective classification of a subset of the particles in the sample.

Abstract: The invention is a state machine having a host controller that controls a level-i controller, wherein the level-1 controller controls the level-2 controller. The level-2 controller controls system component controllers, which in turn control system components to execute a process segment. For example, the machine includes a host controller that selects a set of states to be executed, a level-1 controller that activates the set of states in a predetermined order, wherein each state includes commands, and a level-2 controller that controls system components according to the commands. A method of executing a process includes identifying a set of states to be executed, issuing state commands that need to be issued to execute the current state in the set of states, and activating a next state only after all expected status reports have been received for the current state.

Abstract: A method and apparatus for classifying a plurality of elements in images, where electronic images of a field of view containing elements are formed. Each of the elements has a plurality of features. A first subgroup of the plurality of features from the images of the plurality of elements are extracted and processed to segregate the plurality of elements into first and second groups. A classification class only for each of the elements in the first group is determined by selecting and processing a second subgroup of the extracted features to determine a physical characteristic of the element, and by selecting and processing a third subgroup of the extracted features in response to the determined physical characteristic to determine a classification class of the element. The second group of elements bypasses the determination of classification class.

Abstract: A particle analyzer that includes a specimen source, a flow cell, a pump and delivery tube for transporting specimen fluid from the specimen source to the flow cell, a dispensing valve for injecting stain from a stain source into the specimen fluid in the delivery tube, and a mixing device for mixing the stain and the specimen fluid together. The mixing device includes a cylindrical shaped member having an outer surface, a channel formed in the outer surface with the channel including circumferential and longitudinal turns, and a hollow mixing tube disposed in the channel. As the stain and the specimen fluid flow through the mixing tube, they travel through the circumferential and longitudinal turns and are mixed together. A fluid sensor employing a sensor RC circuit and a reference RC circuit detects capacitance changes in the delivery tube for detecting the presence or absence of fluid therein.

Abstract: A displacement pump comprising a pump assembly and a cassette assembly. The pump assembly includes upper and lower housing portions that define a cavity, an arm disposed in the cavity, a roller attached to the distal end of the arm, and a motor attached to the proximal end of the arm for rotating the arm. The cassette assembly is removably disposed in the cavity and comprises upper and lower cassette housing portions that form an annular compression surface with a channel therein. A hollow compression tube having a flange extending along a length thereof is secured to the compression surface by the flange being engaged with the channel. As the motor rotates the roller arm, the roller presses the compression tube against the compression surface to create a moving occlusion of the compression tube for pushing fluid through the compression tube.

Abstract: A particle analyzer that includes a specimen source, a flow cell, a pump and delivery tube for transporting specimen fluid from the specimen source to the flow cell, a dispensing valve for injecting stain from a stain source into the specimen fluid in the delivery tube, and a mixing device for mixing the stain and the specimen fluid together. The mixing device includes a cylindrical shaped member having an outer surface, a channel formed in the outer surface with the channel including circumferential and longitudinal turns, and a hollow mixing tube disposed in the channel. As the stain and the specimen fluid flow through the mixing tube, they travel through the circumferential and longitudinal turns and are mixed together. A fluid sensor employing a sensor RC circuit and a reference RC circuit detects capacitance changes in the delivery tube for detecting the presence or absence of fluid therein.

Abstract: A multi-neural net imaging apparatus and method for classification of image elements, such as biological particles. The multi-net structure utilizes subgroups of particle features to partition the decision space by an attribute or physical characteristic of the particle and/or by individual and group particle classification that includes an unknown category. Preprocessing and post processing enables heuristic information to be included as part of the decision making process. Preprocessing classifies particles as artifacts based on certain physical characteristics. Post processing enables the use of contextual information either available from other sources or gleaned from the actual decision making process to further process the probability factors and enhance the decisions.

Abstract: A flow cell for examining specimen fluid flowing within sheath fluid. A housing defines a hollow fluid passage that includes a geometric focusing portion in which the fluid passage narrows in height and an examination area. A cannula injects specimen fluid into the fluid passage as a stream of the specimen fluid with an initial velocity. The sheath fluid flows through the fluid passage, having a first velocity as it passes the point the specimen fluid is injected. The initial velocity is less than the first velocity, which focuses down the height of the specimen fluid stream via linear flow rate focusing. The narrowing geometric focusing portion of the fluid passage also focuses down the height of the specimen fluid stream via geometric focusing. A microscope and camera capture images of the focused down specimen fluid stream passing through the examination area.

Abstract: Particles in a fluid are counted as the fluid flows through an examination area of a particle analyzer. Parameters based upon the particle count are calculated. It is determined whether the at least one calculated parameter is within an allowable range for the parameter. Based on this determination, an indication is provided of uniformity of the fluid sample in the examination area.

Abstract: A flow cell for analysis of particles in a sample fluid buffered by sheath fluid has a sample inlet to receive the sample fluid and a sheath inlet for receiving the sheath fluid. The sample fluid flows in a flow direction from the sample inlet past an examination region to an outlet. A flow distributor is positioned between the sheath inlet and the examination region for distributing the sheath fluid ranging in a first direction substantially paralleled to the flow direction to the second direction substantially perpendicular to the flow direction. The distribution of the sheath fluid at the output of the distributor is vortex-free over a wide range of input directions and input chamber geometries. It eliminates the creation of vortices that could cause mixing and instability of the sample fluid in the examination area and allows greater freedom in shaping the fluid system for optimal hydrodynamic focusing.

Abstract: Particles in a fluid are counted as the fluid flows through an examination area of a particle analyzer. Parameters based upon the particle count are calculated. It is determined whether the at least one calculated parameter is within an allowable range for the parameter. Based on this determination, an indication is provided of uniformity of the fluid sample in the examination area.

Abstract: Particles in a fluid are counted as the fluid flows through an examination area of a particle analyzer. Parameters based upon the particle count are calculated. It is determined whether the at least one calculated parameter is within an allowable range for the parameter. Based on this determination, an indication is provided of uniformity of the fluid sample in the examination area.

Abstract: A method and an apparatus for analyzing particles in a fluid sample is accomplished by distributing the sample over an extended area. A plurality of optical still images is taken of the sample, with each image representing a different portion of the area. Each optical image is converted into an electronic image, with the images of the particles in the electronic images. Each electronic image is classified into one of a plurality of classifications of visually discernible characteristics. For each classification, the percentage of the total number of particles classified is determined. The images of the particles are extracted from the electronic images. The images of the particles are displayed in an ordered array by the classification with the number of particles within each classification so displayed being proportional to the percentage determined of the total number of particles displayed.

Abstract: An analyte control solution system tests a plurality of identical test strips, with each test strip having a plurality of different reactive chemicals attached on pads. The analyte control solution system has a first mixture of a first plurality of different analytes, with each of the first plurality of different analytes not reacting with one another, but reacting with a different one of the dipstick pads to generate a visual indicator. The first plurality of different analytes do not react with all of the pads attached to each test strip. Another control solution has a second mixture, physically different from the first mixture, of a second plurality of different analytes. Each of the second plurality of different analytes does not react with one another, but reacts with a different one of the plurality of different reactive chemicals on the test strip to generate a visual indicator.

Abstract: A method and apparatus for selecting the best focal position of an image in a field of view is based upon pixel values located in the image that correspond to locations defining an invariant optical property of the image. In the preferred embodiment, the invariant optical property of the image are pixels that form a "halo" that surround the boundary of an object and are contiguous and immediately adjacent thereto. It has been determined that a certain relationship should exist for this "halo" that surround the boundary of an object when the best focal position is selected.

Abstract: To identify the boundary pixels of a number of particles in the same field of view, an electrical image of the field of view is formed by a CCD raster scan device. The electrical signal from the CCD device is segmented and is digitized. The signals are processed such that the boundary pixels have non-zero values and are linked to one another. The values of the pixels are stored in a boundary memory addressable by a row signal and column signal. In an addressable index memory, a plurality of values are stored with each value being an address to the boundary memory where the pixels having the boundary are located. Finally, a location memory has the same addressable dimensions as the boundary memory. The location memory stores, in address locations corresponding to address locations in the boundary memory where the pixels having characteristics of interest are located, addresses to the addressable index memory.

Abstract: A method and apparatus for selecting the best focal position of an image in a field of view is based upon pixel values located in the image that correspond to locations defining an invariant optical property of the image. In the preferred embodiment, the invariant optical property of the image are pixels that form a "halo" that surround the boundary of an object and are contiguous and immediately adjacent thereto. It has been determined that a certain relationship should exist for this "halo" that surround the boundary of an object when the best focal position is selected.

Abstract: A method of separating red blood cells within a volume of blood provides rapid separation of the red blood cells to permit efficient analysis of the white blood cells. First, a container is filled with the volume of blood while the container is in a substantially vertical position. The container has an open top portion, a side wall, and a closed bottom portion. The volume of blood in the container defines a first surface region having a particular spatial relationship to the side wall. Then, the container is moved to a first position, away from the substantially vertical position. The container is maintained at the first position for at least a first predetermined time such that red blood cells within the volume of blood settle substantially to the side wall of the container. The cross sectional area of the container at the first surface region of the volume of blood is such that the particular spatial relationship is maintained between the first surface region and the side wall.

Abstract: A composition and method for separating red blood cells from whole blood comprising a rouleaux-forming aggregator and an enhancer for enhancing the settling rate. The enhancer is a material which alters directly or indirectly the properties of the red blood cell and may alter the structure and/or reactivity of the aggregator, without adversely affecting the morphology and function of white blood cells. In most instances, the red blood cell enhancers of the invention are osmotic agents. Such agents create a hypertonic solution while not entering the cells themselves. Preferably the enhancer is a salt of oxalic acid, a salt of malonic acid, mannitol or sucrose. Potassium oxalate is most preferred. High molecular weight substances which are large enough to form molecular bridges between red blood cells form the aggregators used in the invention.