Analyzing system with disposable calibration device

• US 6,045,502 A
• Filed: 08/01/1997
• Issued: 04/04/2000
• Est. Priority Date: 01/17/1996
• Status: Expired due to Term

• Current Assignee: Spectro Incorporated (Spectro Scientific, Inc.)
• Original Assignee: Spectro Incorporated (Spectro Scientific, Inc.)
• Inventors: Eppstein, Jonathan A., Ignotz, Keith D., Samuels, Mark A., Newman, Gregory J.
• Primary Examiner(s): MANUEL, GEORGE C
• Application Number:
  US08/904,766
• Time in Patent Office: 977 Days
• Field of Search: 178/18.09, 250/491.1, 73/620, 73/621, 378/18, 378/207, 356/243, 356/244, 600/306, 600/309, 600/310, 600/473, 600/476, 600/477, 600/315
• US Class Current: 600/306
• CPC Class Codes: A61B 2503/045 Newborns, e.g. premature baby monitoring
• CPC Class Codes: A61B 2560/0233 Optical standards
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/0075 by spectroscopy, i.e. measuring spectra, e.g. Raman spectroscopy, infrared absorption spectroscopy A61B5/0071 takes precedence
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes
• CPC Class Codes: A61B 5/4244 liver
• CPC Class Codes: G01J 5/02 Constructional details
• CPC Class Codes: G01J 5/021 Probe covers for thermometers, e.g. tympanic thermometers; Containers for probe covers; Disposable probes
• CPC Class Codes: G01J 5/04 Casings
• CPC Class Codes: G01J 5/048 Protective parts
• CPC Class Codes: G01J 5/53 Reference sources, e.g. standard lamps; Black bodies
• CPC Class Codes: G01N 21/278 Constitution of standards

Abstract

A system and method for calibrating a measurement instrument prior to making a measurement on a material or tissue includes utilizing a removable calibration device to calibrate the instrument, then removing a target portion of the calibration device so that a measurement may be performed. The calibration device may include an index matching agent, such as a gel, that is to be interposed between the patient'"'"'s skin and an output end of the measuring instrument. A method embodying the invention may include making a bilirubin concentration measurement on a skin of a patient by measuring the amplitude of light reflected from the patient'"'"'s skin at first and second wavelengths indicative of a blood content of the patient'"'"'s skin, and measuring the amplitude of reflected light at a third wavelength indicative of an uncorrected bilirubin concentration, then calculating a corrected bilirubin concentration based on the three measurements. The method may also include taking measurements at fourth and fifth wavelengths indicative of a melanin content of the patient'"'"'s skin, and calculating the bilirubin concentration based on the fourth and fifth measurements.

Claims

1. A method for determining a bilirubin concentration in a mammal, comprising the steps of:

a) illuminating a portion of a skin of the mammal with light;

b) detecting a frequency spectrum of light scattered from the skin;

c) determining, from first and second portions of the spectrum, a first parameter indicative of a blood oxygen content of the skin;

d) determining, from a third portion of the spectrum, a second parameter indicative of an uncorrected bilirubin concentration; and

e) calculating a corrected bilirubin concentration based on the first and second parameters.

2. The method of claim 1, further comprising the step of performing a calibration measurement on a calibration target and storing resulting calibration data prior to illuminating the mammal'"'"'s skin with light, wherein the step of calculating a corrected bilirubin concentration is also based on the calibration data.

3. The method of claim 1, wherein the first and second portions of the spectrum are at approximately 520 nm and 585 nm, respectively.

4. The method of claim 3, wherein the third portion of the spectrum is at approximately 476 nm.

5. The method of claim 1, wherein the third portion of the spectrum is at approximately 476 nm.

6. The method of claim 1, wherein the performance of steps a-e result in a first corrected bilirubin concentration, further comprising the steps of:

f) repeating steps a-e to calculate a second corrected bilirubin concentration; and

g) calculating an average corrected bilirubin concentration based on the first and second corrected bilirubin concentrations.

7. The method of claim 6, wherein different portions of the mammal'"'"'s skin are illuminated each time steps a-e are performed.

8. The method of claim 7, wherein the different portions of the mammal'"'"'s skin are located on different portions of the mammal'"'"'s body.

9. The method of claim 1, wherein the performance of steps a-e result in a first corrected bilirubin concentration, further comprising the steps of:

f) repeating steps a-e at least twice to calculate at least second and third corrected bilirubin concentrations;

g) calculating an average corrected bilirubin concentration and a standard deviation using at least the first, second and third corrected bilirubin concentrations;

h) comparing the calculated standard deviation to a predetermined maximum standard deviation; and

i) repeating steps a-g if the calculated standard deviation exceeds the predetermined maximum standard deviation.

10. A system for determining a bilirubin concentration in a mammal, comprising:

means for illuminating a portion of the mammal'"'"'s skin with light;

means for detecting a frequency spectrum of light scattered from the skin;

means for determining, from first and second portions of the spectrum, a first parameter indicative of a blood content of the skin;

means for determining, from a third portion of the spectrum, a second parameter indicative of an uncorrected bilirubin concentration; and

means for calculating a corrected bilirubin concentration based on the first and second parameters.

11. The system of claim 10, further comprising:

means for performing a calibration measurement on a calibration target and for storing resulting calibration data, wherein the means for calculating a corrected bilirubin concentration also utilizes the calibration data.

12. The system of claim 10, further comprising:

means for calculating an average corrected bilirubin concentration and a standard deviation using at least three calculated corrected bilirubin concentrations; and

means for comparing the calculated standard deviation to a predetermined maximum standard deviation.

13. The system of claim 10, further comprising means for holding a removable calibration target that can be used to calibrate the system prior to determining the bilirubin concentration of a mammal.

14. The system of claim 13, further comprising a removable calibration target mounted on the calibration target holding means.

15. The system of claim 14, wherein the removable calibration target comprises structure that remains attached to the calibration target holding means after a portion of the removable calibration target is removed to allow a measurement to be made.

16. A system for measuring a bilirubin concentration of a mammal by directing radiation onto a portion of a skin of the mammal and analyzing scattered or reflected radiation returning from the skin, comprising:

a radiation analyzing device for analyzing scattered or reflected radiation and for outputting radiation data;

a radiation source;

at least one radiation transmitting conduit for directing radiation from the radiation source to a portion of the mammal'"'"'s skin;

at least one radiation receiving conduit for directing radiation scattered or reflected from the mammal'"'"'s skin to the radiation analyzing device; and

means for calculating a bilirubin concentration of the mammal based on an amplitude of the reflected or scattered radiation at first and second wavelengths indicative of a blood content of the mammal'"'"'s skin and on an amplitude of the reflected or scattered radiation at a third wavelength indicative of a bilirubin concentration in the mammal'"'"'s skin.

17. The system of claim 16, wherein the at least one radiation transmitting conduit directs radiation at the mammal'"'"'s skin at acute angle relative to an axis perpendicular to the skin surface.

18. The system of claim 17, wherein the angle is approximately twelve degrees.

19. The system of claim 17, wherein the angle is large enough to reduce radiation backscattering.

20. The system of claim 16, wherein the at least one radiation transmitting conduit comprises a plurality of radiation transmitting conduits, and wherein the at least one radiation receiving conduit is surrounded by the plurality of radiation transmitting conduits.

21. The system of claim 20, wherein the plurality of radiation transmitting conduits are arranged in first and second annular rings, the first annular ring surrounding the at least one radiation receiving conduit, and the second annular ring surrounding the at least one radiation receiving conduit and the first annular ring.

22. The system of claim 16, wherein a numerical aperture of the at least one radiation transmitting conduit is matched to the radiation source, and wherein a numerical aperture of the at least one radiation receiving conduit is matched to the radiation analyzing device.

23. The system of claim 22, wherein the numerical aperture of the at least one radiation transmitting conduit is different from the numerical aperture of the at least one radiation receiving conduit.

24. The system of claim 16, further comprising a window located between the radiation transmitting and receiving conduits and an exterior measuring end of the system, wherein the window comprises a soft polymer that acts as an index matching agent between the radiation transmitting and receiving conduits and the mammal'"'"'s skin.

25. The system of claim 16, wherein a length of the at least one radiation receiving conduit is sufficiently long such that mode scrambling occurs.

26. The system of claim 16, further comprising a proximity sensing device for sensing a proximity of a distal end of the radiation transmitting and receiving conduits to the mammal'"'"'s skin.

27. The system of claim 26, wherein the system only measures the condition of the mammal when the proximity sensing device indicates that the radiation transmitting and receiving conduits are within a predetermined proximity to the mammal'"'"'s skin.

28. The system of claim 26, wherein the proximity sensing device comprises a spring loaded annulus that surrounds the radiation transmitting and receiving conduits.

29. The system of claim 16, further comprising a transmitter for transmitting data regarding the calculated condition of the mammal to a remote recording device.

30. The system of claim 29, wherein the transmitter comprises an infrared transmitter.

31. The system of claim 16, wherein the radiation analyzing device comprises a spectrometer.

32. The system of claim 16, wherein the radiation analyzing device comprises a diffraction grating and a plurality of detectors, wherein the diffraction grating focuses radiation having predetermined wavelengths on respective ones of the plurality of detectors.

33. The system of claim 16, wherein the radiation analyzing device comprises at least one radiation detector and a plurality of radiation filters, each of the plurality of radiation filters allowing only a narrow wavelength band of radiation to reach the at least one radiation detector.

34. The system of claim 16, wherein the radiation analyzing device comprises a radiation detector and a linear variable filter for allowing selected wavelengths of radiation to reach the radiation detector.

35. A method of measuring a condition of a mammal with a device that outputs radiation from a distal end of the device, comprising the steps of:

applying an index matching agent to one of a skin of the mammal and the distal end of the device;

emitting radiation from the distal end of the device so that the radiation passes through the index matching agent and is scattered or reflected by the mammal'"'"'s skin;

receiving the scattered or reflected radiation at the distal end of the device; and

analyzing the received radiation to determine the condition of the mammal.

36. The method of claim 35, further comprising the step of performing a calibration measurement on a calibration target and storing resulting calibration data prior to the step of emitting radiation so that the radiation is scattered or reflected by the mammal'"'"'s skin.

37. The method of claim 36, wherein the step of performing a calibration measurement comprises the steps of:

emitting radiation from the distal end of the device so that it is scattered or reflected from the calibration target;

receiving the scattered or reflected radiation at the distal end of the device;

calculating calibration data based on the received radiation; and

storing the calibration data.

38. The method of claim 37, wherein the step of applying an index matching agent is performed before the calibration measurement is performed.

39. A calibration device for calibrating a measuring system that transmits radiation to a material or tissue from an output end to effect measurements, comprising:

a removable calibration target;

a structure for holding the removable calibration target, the structure including an opening through which radiation can be transmitted; and

an index matching agent for interposition between the output end of the measuring system and the material or tissue being measured.

40. The calibration device of claim 39, wherein the index matching agent comprises a window of a soft polymer that is attached to the structure.

41. The calibration device of claim 39, further comprising a window attached to the structure.

42. The calibration device of claim 41, wherein a substance held within the structure acts an index matching agent between the output end of the measuring system and the removable calibration target while the calibration target is attached to the structure, and wherein the substance acts as an index matching agent between the output end of the measuring system and a material or tissue being measured when the removable calibration target is removed.

43. The calibration device of claim 39, wherein the index matching agent is a gel held within the structure.

44. The calibration device of claim 39, wherein the removable calibration target comprises a user removable tear tab.

45. A method for determining a bilirubin concentration in a mammal, comprising the steps of:

a) illuminating a portion of a skin of the mammal with light;

b) detecting a frequency spectrum of light scattered from the skin;

c) determining, from first and second portions of the spectrum, a first parameter indicative of a blood content of the skin;

d) determining, from third and fourth portions of the spectrum, a second parameter indicative of a melanin content of the mammal'"'"'s skin;

e) determining, from a fifth portion of the spectrum, a third parameter to indicative of an uncorrected bilirubin concentration; and

f) calculating a corrected bilirubin concentration based on the first, second and third parameters.

46. The method of claim 45, further comprising the step of performing a calibration measurement on a calibration target and storing resulting calibration data prior to illuminating the mammal'"'"'s skin with light, wherein the step of calculating a corrected bilirubin concentration is also based on the calibration data.

47. The method of claim 45, wherein the first and second portions of the spectrum are at approximately 526 nm and 586 nm, respectively.

48. The method of claim 45, wherein the fifth portion of the spectrum is at approximately 476 nm.

49. The method of claim 46, wherein the third and fourth portions of the spectrum are between approximately 600 nm and approximately 700 nm.