Measuring and testing – Instrument proving or calibrating – Volume of flow – speed of flow – volume rate of flow – or mass...
Reexamination Certificate
1998-07-06
2001-06-26
Williams, Hezron (Department: 2856)
Measuring and testing
Instrument proving or calibrating
Volume of flow, speed of flow, volume rate of flow, or mass...
C073S168000, C073S001160
Reexamination Certificate
active
06250130
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to optical flow verification systems, and in particular to an optical flow verification system employing reflectivity measurements to confirm aspiration or dispense of a liquid volume.
BACKGROUND OF THE INVENTION
Medical laboratories increasingly rely upon automated assay equipment in order to handle large numbers of assays efficiently in terms of time and cost, and further to increase the reliability of such assays by decreasing the amount of human intervention involved in such assays. However, this reduction in human intervention necessitates a corresponding increase in equipment and devices which ensure the accurate performance of such automated assays. In particular, regulatory agencies responsible for oversight of such testing are reluctant to approve certain forms of automated equipment absent enhanced monitoring and error reporting devices.
Assay equipment currently in use is commonly programmed for withdrawal of a desired reagent in preparation for execution of an assay. While such programmed aspirations are typically accurate, there remains the possibility that a reagent source has run dry though the assay equipment continues to aspirate from the empty reagent container, giving a “short shot” of reagent. Further, while an initial indication that reagent exists in a respective container prior to aspiration may be provided, equipment does not currently detect the evacuation of a supply of reagent during an aspiration. Finally, reagent aspiration equipment in existing automated assay apparatus does not provide the capability to detect an occlusion or an incorrect flow rate in real time or errors from a line break.
Optical verification systems are presently used to measure the transmittance of light through a tube as affected by the contents of the tube. Such transmittance detectors include a light source disposed opposite a light sensor on either side of a tube and are primarily useful for detecting and identifying the contents of a tube at any given moment, and do not find utility in confirming a volume of aspirated liquid.
SUMMARY OF THE INVENTION
The present invention provides an apparatus for verifying a volume of reagent aspirated within an automated assay instrument. A tube has a reagent probe disposed at one end, and a pump or like device disposed at an opposite end. Intermediate the probe and the pump is an optical fluid detector having a housing, through which a transparent portion of the tube passes. Within the fluid detector housing, the fluid detector includes an optical source, such as an infra-red light emitting diode, disposed proximate the tube and oriented to illuminate the interior of the tube. The fluid detector also includes, within the housing and proximate the tube passing therethrough, a photodetector, oriented ninety degrees about the circumference of the tube to detect optical source illumination reflected off an interior surface of the tube opposite the optical source.
The photodetector provides one voltage level when a gas is within the tube in the optical fluid detector, and a different voltage when a liquid is within the tube. This is due to the absolute differences between the refractive indexes of the content of the tube and the tube itself. A threshold determining and comparison circuit in communication with the detector discriminates between the two levels. The rate at which aspirate is pumped and the volume of the tube from a probe tip inlet to the detector are known, typically by using a stepper motor driven syringe plunger on the end of the tube. Therefore, a given volume of aspirate should take a predictable amount of time (or steps) to pass through the detector, taking into consideration established tolerances. Typically, the tube is water filled to the probe tip before aspiration. Time (or stepper motor steps) is measured from the start of the aspiration of reagent. A liquid-air transition is detected at the end of the aspiration of reagent occasioned by the tip being withdrawn from the reagent source and the pump being driven further to place the reagent in a heater zone. If the liquid-air transition is not seen at the expected time, one of several problems with the aspiration are assumed, and the assay is canceled.
A further embodiment of the presently disclosed invention utilizes essentially the same hardware as described in the foregoing, though the data processing which is performed on the output of the threshold determining and comparison circuit differs. For instance, in this further embodiment, a processor circuit receives input from both the threshold determining and comparison circuit and a pump control circuit for the purpose of sampling the detected conditions at the photodetector in relation to the operation of the pump. A profile of photodetector condition versus pump operation is thus created from the point an aspiration cycle is commenced at least until a fluid-to-air boundary is detected, or from the point a dispense cycle is commenced at least until an air-to-fluid boundary is detected. Each profile is then compared against a standardized profile in order to determine if the detected transition occurred at a desired point in the profile.
The processor circuit is programmable to define acceptable margins of error relative to the reference profile, and to define a variety of error conditions under which the detected profile is designated as being outside of an acceptable range. For instance, a maximum number of fluid-air or air-fluid boundaries may be defined, above which the aspirate or dispense function is flagged as in error, and suitable warning, maintenance or diagnostics routines are initiated.
It is an object of the present invention to provide to an automated assay instrument offering an enhanced measure of confidence in the withdrawal accuracy of a desired quantity of aspirate. It is a further object of the present invention to provide error detection and notification which is applicable to a variety of error conditions.
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“CCD 800 Series Service Manual” for the Ciba Corning 800 Series Blood Gas Instrument (1994).
Cha Ying
Howard David J.
Murthy Kurukundi Ramesh
Bayer Corporation
Fayyaz Nashmiya
Weingarten, Schurgin Gagnebin & Hayes LLP
Williams Hezron
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