Optics: measuring and testing – Blood analysis
Reexamination Certificate
1999-06-22
2001-07-17
Font, Frank G. (Department: 2877)
Optics: measuring and testing
Blood analysis
C356S040000, C356S042000
Reexamination Certificate
active
06262799
ABSTRACT:
TECHNICAL FIELD
This invention relates to a method for rapidly making centrifuged material layer volume measurements. The method of this invention is particularly useful in performing blood constituent count measurements in a centrifuged sample of anticoagulated whole blood while the blood sample is being centrifuged.
BACKGROUND ART
The measurement of the blood cell counts in a centrifuged sample of anticoagulated whole blood has been described in the scientific literature, and a method for easily measuring certain blood cell and other constituent layers is described in U.S. Pat. No. 4,027,660, granted Jun. 7, 1977 to Stephen C. Wardlaw et al. In the patented method, a sample of anticoagulated whole blood is centrifuged in a precision capillary tube which contains a plastic float. The float linearly expands some of the cell layers and the platelet layer.
In performing the patented method, the blood sample is centrifuged for about five minutes at about 12,000 RPM, and then the expanded lengths of the cell and platelet layers are measured. One of the problems in the patented method pertains to the need for the operator to remove the tube from the centrifuge and re-insert it into a reader. Because this operation must be performed within a limited time interval following centrifugation, it requires the close attendance of the technician, which is inefficient and further exposes the technician to a potentially hazardous sample. This problem is particularly important in that relatively unskilled technicians may not appreciate the need for timely reading of the sample tubes, and thus may result in erroneous readings. Another problem which arises with the aforesaid prior art method results from the fact that the capillary tube expands slightly as a result of the high pressure of the blood sample column during centrifugation of the blood sample. After the cell layers have been compacted around the float, they form a relatively solid plug in the bore of the tube and, as the centrifuge decelerates, the wall of the tube springs back to its normal shape, and thus tends to “pumps” the blood cell layers upwardly in the tube. This action causes disruption of at least a part of the cell layers in some samples and thus renders such cell layers difficult or impossible to read.
It would be desirable to be able to measure the blood constituent layers while the tube Is still under centrifugal stress so that the cell layers are not disrupted, and also to reduce the amount of sample tube handling and the potential for error.
DISCLOSURE OF THE INVENTION
This invention relates to an assembly for quickly determining individual material volume measurements during centrifugation of a gravimetrically separable material mixture sample, such as an anticoagulated whole blood sample. Additionally, this invention relates to a method which can determine blood constituent volume measurements, and blood constituent counts during centrifugation. The method of this invention utilizes a combined centrifuge and reader which will perform the functions of both centrifugation and reading, and thus simplify the performance of the material layer measurements described in the aforesaid U.S. patents. By following the principles of this invention, white blood cell and platelet layers can be quantified with a minimum of sample manipulation and with minimal disruption of the formed layers in the blood sample.
The method of this invention involves the use of: a centrifuge; a high intensity fluorescent colorant excitation light source; a photodetector; and a processor controller for controlling operation of the assembly. The light source is preferably a high intensity pulsed light source which periodically illuminates the blood sample in the sampling tube as the latter is being centrifuged. Illumination of the blood sample in the tube causes fluorescence of certain of the blood cell constituents as well as illumination of the red blood cell layer, so that the photodetector can discriminate between the various cell layers in the tube that are gravimetrically compacted during the centrifugation step. Appropriate selection of filters on both the light source and the detector allows fluorescent light emanating from the fluorescing cell layers to be detected and measured, and also allows light reflected from material layers in the sample to be detected and measured. The pulsing of the light source is synchronized with the rotational position of the tube during centrifugation so that the tube will be momentarily illuminated as it passes by the photodetector. The optics and filters used in performing the method of this invention are generally similar to those described in U.S. Pat. No. 4,558,947, granted Dec. 17, 1985 to S. C. Wardlaw, the disclosure of which is incorporated herein in its entirety.
The light source for Illuminating the tube for the excitation of fluorescence must have sufficient emission in the excitation band (about 420-480 nm) to provide adequate emission energy from the sample tube, when received by a filtered, solid-state image dissector, such as a CCD array. Further, the energy must be delivered in the time period when the tube to be imaged is within the focal range of the detector, which is typically about 50 &mgr;sec. These requirements are best met by a xenon flash tube having an associated focusing means, rather than a diffuser, which flash tube is driven by a power supply capable of delivering short pulses at the needed power levels and wherein the light flashes are precisely tuned to the position of the tube relative to the detector when the flash tube is triggered.
The processor controller controls operation of the assembly in that, on command, it will: initiate centrifugation; monitor the RPM of the centrifuge; time the period of centrifugation; synchronize the light pulses with the ongoing centrifuge RPM; control operation of the photodetector; receive and store constituent layer readings; calculate the constituent layer compaction, and the resultant constituent counts or values; and shut the centrifuge down. The operator thus need only place the blood sampling tube in the centrifuge, and initiate operation of the assembly. For operator convenience and safety, the blood sampling tube can be contained in a special cassette of the general type described in U.S. Pat. No. 5,776,078, granted Jul. 7, 1998.
This invention also involves the use of a centrifuge component which is operable to synchronize the pulsing of a light source irregardless of the speed of rotation of the centrifuge. The inclusion of such a synchronization component in the centrifuge takes into account centrifuge wear, eliminates the need to set or adjust the pulsing synchronization of the assembly, and also allows the centrifuge to be intentionally operated at different speeds.
It is therefore an object of this invention to provide a method for obtaining information from a material mixture which will allow the reading of material layer thicknesses following a fixed period of centrifugation while the sample is still within the centrifuge and the centrifuge is still rotating.
It is a further object of this invention to provide a method of the character described wherein the material mixture is a sample of anticoagulated whole blood.
It is another object of this invention to provide a method of the character described wherein the ultimate thickness of a plurality of material layers in the sample being centrifuged can be derived from layer thickness measurements made during centrifugation.
These and other objects and advantages of the invention will become more readily apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings, in which:
REFERENCES:
patent: 41 16 313 A1 (1992-11-01), None
Font Frank G.
Jones William W.
Levine Robert A.
Ratliff Reginald A.
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