Method and apparatus for direct spectrophotometric measurements in unaltered whole blood

• US 6,519,025 B2
• Filed: 07/10/2001
• Issued: 02/11/2003
• Est. Priority Date: 02/23/1989
• Status: Expired due to Fees

• Current Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Original Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Inventors: Steinke, John M., Shepherd, Albert Pitt
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): LAUCHMAN, LAYLA G
• Application Number:
  US09/902,823
• Publication Number:
  US 20020041371A1
• Time in Patent Office: 581 Days
• Field of Search: 356/39, 356/442, 356/40, 356/41, 356/409, 356/436, 250/573, 250/574
• US Class Current: 356/39
• CPC Class Codes: G01N 2021/3148 using three or more wavelengths
• CPC Class Codes: G01N 21/31 Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry G01N21/72 takes precedence
• CPC Class Codes: G01N 33/72 involving blood pigments, e.g. haemoglobin, bilirubin or other porphyrins; involving occult blood

Abstract

A method and apparatus that allows accurate spectrophotometric determination of the concentrations of various hemoglobin species in whole undiluted blood. The invention employs 1) an optical apparatus designed to maximize the true optical absorbance of whole blood and to minimize the effects of light scattering on the spectrophotometric measurements of the concentrations of various constituent components, and 2) methods to correct the hemoglobin concentration measurements for light scattering and for the effects of the finite bandwidth of the substantially monochromatic light. In the optical apparatus optical parameters, such as sample thickness, detector size, sample-to-detector distance, wavelengths, monochromicity, and maximum angle of light capture by detector, are selected so as to minimize the contribution of light scattering and to maximize the contribution of true optical absorbance. After making measurements of a blood sample'"'"'s optical density at each of the wavelengths, corrections are made for the effects of light scattering.

Claims

1. An apparatus for determining the concentrations of a plurality of constituent components of unaltered whole blood, comprising:

a cuvette for holding a sample of unaltered whole blood;

a radiation generator for directing radiation into said sample, said radiation having a plurality of substantially monochromatic radiation wavelengths;

a radiation detector for detecting n radiation wavelengths after passing through said sample of unaltered whole within said cuvette, n being an integer;

a computer for calculating concentrations of k constituent components of said sample of unaltered whole blood, corrected for the effects of radiation scattering, as a function of said detected intensities of said n radiation wavelengths, k being an integer less than n.

2. The apparatus of claim 1, said cuvette having a sample chamber with a depth in the range of 80 to 150 micrometers.

3. The apparatus of claim 2, said cuvette having a sample chamber with a depth of approximately 90 micrometers.

4. The apparatus of claim 1, said detector detecting both unscattered and scattered radiation.

5. The apparatus of claim 4, said detector detecting scattered radiation at an angle of at least approximately 30°

from a central axis of radiation emanating from said sample.

6. The apparatus of claim 5, said detector detecting scattered radiation at an angle of at least approximately 70°

from said central axis of radiation emanating from said sample.

7. The apparatus of claim 1, the detector comprising a single detector having a detecting area of at least 150 square millimeters.

8. The apparatus of claim 7, said single detector having a detecting area of at least approximately 600 square millimeters.

9. The apparatus of claim 1, wherein a distance between said detector and said cuvette is within the range of 0 to 10 millimeters.

10. The apparatus of claim 9, wherein said distance between said detector and said cuvette is approximately 1 millimeter.

16. The apparatus of claim 4, said detector detecting scattered radiation within an angle of at least approximately 30°

from a central axis of radiation emanating from said sample.

17. The apparatus of claim 16, said detector detecting scattered radiation within an angle of at least approximately 70°

from said central axis of radiation emanating from said sample.

11. A method for determining the concentrations of a plurality of constituent components of unaltered whole blood, comprising:

generating a plurality of substantially monochromatic radiation wavelengths;

irradiating a sample of unaltered whole blood with said plurality of radiation wavelengths;

detecting intensities of n radiation wavelengths after passing through said sample of unaltered whole blood, where n is an integer; and

calculating concentrations of k constituent components of said sample of unaltered whole blood, corrected for the effects of radiation scattering, as a function of said detected intensities of said n radiation wavelengths, k being an integer less than n.

12. The method of claim 11, said calculating step comprising:

iteratively determining at least one radiation scattering vector for the particular composition of the unaltered whole blood sample being analyzed; and

using said at least one radiation scattering vector to correct said calculated concentrations of said k constituent components.

13. The method of claim 12, said iteratively determining step, comprising:

iteratively determining a red blood cell radiation scattering vector for the particular composition of the unaltered whole blood sample being analyzed.

14. The method of claim 13, said iteratively determining step, further comprising:

iteratively determining a non-specific radiation scattering vector for the particular composition of the unaltered whole blood sample being analyzed.

15. The method of claim 12, said iteratively determining step, comprising:

iteratively determining a non-specific radiation scattering vector for the particular composition of the unaltered whole blood sample being analyzed.