Patent Application
20080297769
The invention relates generally to determination of characteristics of a fluid contained in a vessel. In particular, the invention provides a photometric system operable to determine certain characteristics of a fluid sample by comparing one or more predetermined numeric values against a ratio of the intensity of light, or other radiation, measured at two characteristic wavelengths, wherein the intensities are measured subsequent to passing the radiation through walls of the container (and typically also through the fluid sample).
Many situations exist in which it is desirable to interrogate fluid samples to determine one or more properties of the fluid, or to gain insight for an evaluation or diagnosis. In particular, the medical industry generates and evaluates numerous fluid samples as a part of ordinary medical care. Certain laboratories currently process about 5,000 of such samples per day, with an expectation that the number of processed samples will double within 4 to 5 years. The sheer volume of samples to be characterized essentially dictates that some sort of automation in sample evaluation is necessary.
A fully automated sample characterization system has several important obstacles to overcome, including ensuring minimum/maximum sample volume and avoiding interferences in the sample and/or incorrect sample content. If the volume of a sample is insufficient, the probe of the analyzer may crash into the bottom of the tube. On the other hand, if the test tube is overfilled, spillage can occur once the cap is removed and the tube is moved around the track system through various robotic systems. Certain fluid samples can contain interferences such as lipemia, icterus, hemolysis, clots, etc. These occurrences may impede the various analyzers and consequently must be accounted for, and sometimes removed from the sample, before the test can be properly completed. Occasionally, a sample labeled as serum actually contains urine and vice versa. In such cases, the sample identification bar codes printed on the tube labels are incorrect, and the samples should be flagged for correction and removed from further processing.
The current state-of-the-art implements prescreening of test tubes for volume, interferences, and/or content, through tedious manual inspection. Each incoming sample is visually inspected for observed interferences. In those cases where labels that are attached to the outside of the tube impede a visual inspection, the technicians will remove the cap and look down into the tube. The need for manual inspection of the tubes can prevent an otherwise automated laboratory facility from increasing sample throughput to a desired daily total. In addition, the frequent need for opening samples exposes technicians to the unknown content of the test tube, may cause contamination of the sample, and may result in spillage from overfilled tubes. Furthermore, visual examination tends to rely on the color of the sample. In certain cases, a technician may not properly identify a sample as urine, which tends to have the same color as blood serum. In addition, the various levels of interferences such as lipemia and hemolysis sometimes produce subtle changes in color, which make visual inspection a significant challenge.
Body fluid samples to be characterized in medical procedures are typically placed into a test tube prior to being delivered to a test facility. Such test tubes are typically made from polypropylene and generally include at least one self-adhering label applied to the side of the tube. The label(s) permit a bar code to be associated with the sample for identification and tracking. Unfortunately, such labels are nonuniform, and present a source of almost random interference for a photometric fluid characterization system. Nonetheless, work has been done to provide photometric fluid characterizing systems that could potentially be modified and adapted to the instant sample verification and screening problem.
In U.S. Pat. No. 5,478,750, the contents of which are incorporated herein by this reference, Bernstein et al. disclose a photometric analyzer for measuring the concentration of substances found in a body fluid sample. This analyzer measures light absorption in the sample at a number of preselected frequencies. Typically, white light is directed through the sample to a pair of apertures that direct light from the sample through a plurality of beam splitters, interference filters, and associated photodetectors. The analyzer further includes means for performing automatic calibration and error checking. They disclose that the effect of random variations between measurements may be minimized by averaging repeated measurements of a given sample. A light wavelength of 850 nm is used as a reference, because while such wavelength is not absorbed by the sample, its intensity is affected to the same degree as the light having relevant characterization wavelengths. The intensity of light at 850 nm and a plurality of detection wavelengths of light passed through a test sample is compared to the corresponding intensity of light at 850 nm and the same plurality of detection wavelengths of light passed through a control sample to determine the degree of light absorption in the test sample due to presence of a known reaction product.
U.S. Pat. No. 6,711,424, the contents of which are incorporated herein by this reference, issued to Fine et al., discloses the use of optical measurement to determine parameter(s) in blood using at least two frequencies of light. The method can be applied to in vivo, and well as in vitro tests. Fine et al. disclose making a plurality of measurements, or continuous measurement spanning a period of time, subsequent to cessation of blood flow. The values obtained from the measurements can be plotted to determine a parametric slope. To determine the parametric slope aimed at determining a desired parameter of blood, at least two wavelengths are selected in accordance with the parameter to be determined. Fine et al. disclose determination of concentration of a substance in a patient's blood by comparing the obtained parametric slope to predetermined calibration curves.
U.S. Pat. No. 6,770,883, the contents of which are incorporated herein by this reference, issued to Mc Neal et al., discloses a method and apparatus for detecting the vertical position of the interfaces between blood cells, plasma, etc., and separation gel in test tubes that may be covered by labels. Their method and apparatus requires shining light having two wavelengths through a test tube to determine an elevation of the interfaces. The first wavelength is transmitted by serum, plasma, labels and the material but substantially blocked by the cells. The second wavelength is substantially blocked by serum, plasma, and cells, but substantially transmitted by the material and labels. The test tube is moved vertically with respect to the light beams, and changes in detected transmission through the tube indicate the location(s) of the interfaces.
U.S. Pat. No. 6,195,158 B1, the contents of which are incorporated herein by this reference, describes an optical scanning system based on an array of LEDs that emit light between 400 and 2500 nm. The length of the array corresponds to the length of the tube such that the entire tube is illuminated. The transmitted light is received on the opposite side of the tube by silicon detectors. By measuring the absorption of different wavelengths and comparing these measurements to values that were obtained through calibration measurements and using statistical analysis, the following parameters can be obtained: height of fluid level, hemoglobin, total bilirubin, and lipids. Also measured is the temperature of the specimen, as well as its type (urine vs. plasma vs. serum).
In United States Patent application No. 2004/0241736, the contents of which are incorporated herein by this reference, Hendee et al. disclose methods and structures adapted to determine one or more attributes in a fluid sample from a spectrum of the sample. Their apparatus includes a light source that can deliver light comprising a plurality of wavelengths to the optical sampling apparatus, a collector that collects light that has interacted with the sample, a spectrometer, and a processor. In general terms, their light source generates infrared light that is directed to the sampling apparatus, where the light interacts with the biological sample. The optical source can optionally comprise a plurality of narrow wavelength devices, such as light-emitting diodes or laser diodes. The exiting light is directed to a spectrometer that yields an absorbance spectrum. The optical measurement system processes the absorbance spectrum using a multivariate calibration model to yield measurements of attributes of the sample, e.g., constituents of a blood sample.
Additional photometric, or optically based, fluid interrogation systems are disclosed in the patent literature. See, e.g., U.S. Pat. Nos. 6,195,158; 6,315,955; 6,628,395; and 6,791,674. Other relevant published United States utility Patent applications may include 2006/0154327. The entire disclosures of all of the aforementioned patents and patent applications are hereby incorporated as though set forth herein, in their entirety, for their disclosures of structure and methods related to radiologically interrogating fluid samples.
To facilitate increased automation of fluid sample testing, and particularly for body fluid sample testing, an improved fully automated system that can prescreen unopened test tubes for sample content and volume is desired. In addition, the prescreening desirably would include the scanning and identification of different anticoagulants such as citrate, EDTA, heparin, or fluoride, which presently cannot be detected through visual inspection, but may have an effect on the sample analysis procedure and/or result.
An apparatus, and method of its use, to determine a characteristic of a fluid sample contained inside a closed container. The apparatus includes a radiation structure, intensity detector structure, and comparison structure. A first embodiment structured according to certain principles of the instant invention includes first and second radiation structure. An operable first radiation structure is configured and arranged to direct first emitted radiation through the container at a first location for reception of first transmitted radiation by a first intensity detector to obtain a first transmitted intensity. Desirably, the first emitted radiation includes a characteristic first wavelength selected as a reference based upon its substantial lack of attenuation when transmitted through a known fluid composition. An operable second radiation structure is configured and arranged to direct second emitted radiation through the container for reception of second transmitted radiation by the first intensity detector to obtain a second transmitted intensity. Desirably, the second emitted radiation includes a characteristic second wavelength that is distinguishable from the characteristic first wavelength, and is selected as a measurement tool based upon its predictive attenuation when transmitted through the same known fluid composition.
In addition, it is desirable for the first and second emitted radiation to be applied to the container at the same location. One currently preferred arrangement of first radiation structure and second radiation structure includes a first beam splitter in common, with the first beam splitter being arranged to cast first and second emitted radiation onto the same location.
An operable comparison structure is adapted to compare a first intensity ratio, of the first and second transmitted intensity, against a predetermined value. Sometimes, the intensity ratio includes division of the first transmitted intensity by the second transmitted intensity. Other times, the intensity ratio includes division of the second transmitted intensity by the first transmitted intensity.
A second embodiment structured according to certain principles of the instant invention includes third and fourth radiation structures. An operable third radiation structure maybe configured and arranged to direct third emitted radiation through the container at a second location effective to obtain a third transmitted intensity, where the second location is disposed at a container elevation that is different from the first location. An operable fourth radiation structure may be configured and arranged to direct fourth emitted radiation through the container at the second location effective to obtain a fourth transmitted intensity. In certain cases, the first emitted radiation and the third emitted radiation share the same characteristic first wavelength. In addition, the second emitted radiation and the fourth emitted radiation may share the same characteristic second wavelength. One currently preferred interrogation system includes a third radiation structure and fourth radiation structure having a second beam splitter in common. Such second beam splitter is desirably arranged to cast the third and fourth emitted radiation onto the same second location. Typically, the third and fourth transmitted radiations are received by a second intensity detector.
For data manipulation to determine a fluid characteristic, the comparison structure may be adapted to compare first data, comprising the second transmitted intensity, to second data, comprising the fourth transmitted intensity. Such data manipulation may be used to indicate presence of a desired fluid level in the container. Another operable way to indicate presence of fluid in the container is by comparing the first intensity ratio against a second intensity ratio, of the third and fourth transmitted intensity. It is also within contemplation alternatively to provide emission-directing structure adapted to move the container relative to the first intensity detector effective to permit detecting radiation transmitted through the container at a second elevation to verify a desired fluid level in the container.
A method for using an interrogation apparatus structured according to certain principles of the instant invention generally includes the steps of: disposing the container in position for interrogation by radiation; separately applying first emitted radiation and second emitted radiation, in any order, to the first location; obtaining a first numeric value corresponding to the first transmitted radiation and a second numeric value corresponding to the second transmitted radiation; calculating a first ratio of the first numeric value and the second numeric value; and comparing the first ratio to a predetermined value to make a determination about a fluid characteristic. Data manipulation may include dividing the first numeric value by the second numeric value, or dividing the second numeric value by the first numeric value.
Another method for using interrogation apparatus structured according to certain principles of the instant invention includes the steps of: disposing the container in position for interrogation by radiation; separately applying the first emitted radiation and the second emitted radiation, in any order, to the first location; obtaining a first numeric value corresponding to the first transmitted radiation and a second numeric value corresponding to the second transmitted radiation; separately applying the third emitted radiation and the fourth emitted radiation, in any order, to the second location; obtaining a third numeric value corresponding to the third transmitted radiation and a fourth numeric value corresponding to the fourth transmitted radiation; calculating a first ratio of the first numeric value and the second numeric value; and comparing the first ratio to a predetermined value to make a determination about a fluid characteristic. Such method may further include calculating a second ratio of the third numeric value and the fourth numeric value; and comparing the first ratio to the second ratio to make a determination about a fluid characteristic.
In the drawings, which illustrate what are currently considered to be the best modes for carrying out the invention:
A workable container in which to hold a fluid sample for interrogation by a system constructed according to certain principles of the instant invention is illustrated in
One currently preferred sample container is made from polypropylene, and is well known and commonly used in processing and evaluating medical samples. In general, the sample container material may be manufactured from substantially any suitable fluid-resistant container material capable of transmitting radiation through its walls, such as a soda-lime, borosilicate, Pyrex, RTM, or other glass or a polypropylene, polymethylpentene, polycarbonate, or other medical-grade plastic, and the like.
Container 100 illustrated in
The presence of one or more label causes additional absorption of radiation applied to the container, and can represent a source of substantially random error in optically based interrogation of a sample using certain prior art techniques. For example, repetitive accuracy for the prior art technique in which presence or absence of fluid is detected simply based on absolute intensity of transmitted light at a specific wavelength is frustrated by the random absorption caused by an unknown number of labels. The present system avoids such random error, in part, by comparing a ratio of intensity of transmitted light at two wavelengths, as will be described in detail below.
Structure of an operable sample interrogation system, generally indicated at 120, which is constructed according to certain principles of the instant invention, is illustrated in
For purpose of this disclosure, radiation may be described as having a wavelength, or characteristic wavelength. Such is intended, in certain instances, to encompass radiation spanning a range about a single recited wavelength. For example, a white light source can be applied through a filter system constructed to permit radiation having a restricted range of wavelengths to pass therethrough. A representative wavelength selected from such restricted range may be used as a characteristic wavelength to denote such emitted radiation. Certain intensity detectors may be arranged to detect the overall intensity of the entire spectrum of wavelengths in the restricted range of radiation that has been transmitted through a fluid sample, thereby providing an output denoting the transmitted intensity of such characteristic wavelength. Of course, in certain cases, such as when using a very high quality laser radiation source that emits radiation at substantially only a single wavelength, the characteristic wavelength simply applies over a more narrow range of wavelengths, such as a single wavelength. In other cases, the transmitted intensity of a single wavelength may be obtained from a suitably constructed detector, irrespective of the range of transmitted wavelengths received by the detector. It is believed that the proper scope encompassed by the terms “wavelength” and “characteristic wavelength” is logically determinable in context.
With continued reference to
It is also within contemplation that certain fluid characterizing systems structured according to certain principles of the invention could include data manipulation to characterize a fluid property, where the data manipulation is essentially hard-wired into an electromechanical system. For example, initial processing of an empty, or insufficiently full, sample container could generate a signal above a threshold value, and thereby cause a solenoid to kick the sample off from the processing conveyor.
With reference now to
With reference now to
In general, one of the first or second source of radiation, 158 or 172, is selected having a characteristic wavelength for use as a reference and typically based upon its substantial lack of attenuation when transmitted through a known fluid composition. The other of the first and second source of radiation is selected having a characteristic wavelength that is distinguishable from the other radiation's wavelength and is used as a measurement tool based upon its predictive attenuation when transmitted through the same known fluid composition. Desirably, both first and second radiation will have wavelengths that permit transmission through the container walls and a number of labels that may be carried on such walls. Data manipulation or reduction, to determine one or more fluid characteristic, typically includes dividing a value corresponding to the intensity of one transmitted radiation by the value corresponding to the intensity of the other transmitted radiation. The result of such calculation is then compared to a predetermined value to make a determination of a fluid characteristic.
The absolute intensity of the transmitted light, however, cannot be used as a reliable measure of detection. There are other factors such as the labels on the outside of the test tube, the test tube material, and its wall thickness that affect the transmission of light. To exclude these variables from the measurement, and to obtain a signal that only relates to the measure of interest, it is necessary to implement a reference and an absorption light each at a given wavelength. The reference wavelength is selected in a region outside of the absorption band, while the absorption wavelength is selected from inside this band. Computing the ratio of the intensity between the reference and the absorption wavelength removes all disturbance factors and results in a signal that only relates to the measure of interest.
It is within contemplation that emitted measurement radiation 162 and 162′ could be produced from the same source, such as a laser, LED, or assembly of a light source and filter arrangement. Similarly, emitted reference radiation 174 and 174′ could also be from the same source. In such case, a known optical arrangement (e.g. including one or more mirror, beam splitter, lens, and the like), can be provided to direct such radiation to a plurality of desired elevations and locations. It is also within contemplation that a reference or measurement radiation source may be disposed at each desired interrogation elevation. In any case, a detector would be operably provided at the corresponding elevation. It is further within contemplation to displace a container 100 with respect to one or more sources or beams of radiation, effective to provide a plurality of elevations for use in interrogation of the container 100.
Using the configuration shown in
However, there is an additional difficulty. Tubes are typically covered with labels of varying number that exhibit additional absorption, making it difficult, if not impossible, to detect volume simply based on absolute intensity of light at a specific wavelength. Instead it is advantageous to measure the intensity of transmitted light at two separate wavelengths at the same location on the test tube. A reference wavelength is selected in a region outside of the absorption spectrum whereas the measuring wavelength is selected in a region where absorption takes place. This is shown in
As is apparent from
With reference again to
Blood samples sometimes contain varying levels of hemolysis, which trained technicians detect by the color of the sample. Using an interrogation setup such as illustrated in
To detect the level of hemolysis and to eliminate the effects of paper labels, tube material, wall thickness, intensity ratios based on absorption and reference wavelengths can be computed. In reality, however, light sources such as light-emitting diodes (LEDs) are only available at certain wavelengths that may not necessarily match exactly the regions shown in
1. the minimum slope of the best line fit exceeds 0.001 (yields a 50% change from lowest to highest signal);
2. the relative change between the smallest and largest value is at least 50%; and
3. the worst data fit does not exceed 9.5%.
Combining a 565 nm with a 570 nm LED from Table 1 as shown in
Another frequently encountered interference in blood samples is lipemia. Low levels of lipemia can be tolerated in the sample. At higher levels, however, the presence of lipemia interferes with the results of the analyzers. A white light source and interrogation setup such as illustrated in
Based on the white light spectrum shown in
1. the minimum slope of the best line fit exceeds 0.055;
2. the relative change between the smallest and largest value is at least 50%;
3. the worst data fit does not exceed 8.5%.
The white light spectrum of blood samples containing various levels of icterus are shown in
Urine can easily be confused with blood serum because of their similar color. As such, having the ability to detect urine with an automated detection system is important. The white light spectrum illustrated in
The presence of anticoagulant agents can affect results from blood analysis tests, so screening for such anticoagulant may be important. The white light spectrum illustrated in
The white light spectrum illustrated in
