Intra-serum and intra-gel for modeling human skin tissue

• US 6,475,800 B1
• Filed: 02/10/2000
• Issued: 11/05/2002
• Est. Priority Date: 07/22/1999
• Status: Expired due to Fees

• Current Assignee: GLT Acquisition Corporation
• Original Assignee: Instrumentation Metrics Inc.
• Inventors: Malin, Stephen F., Ruchti, Timothy L., Hazen, Kevin H., Blank, Thomas B., Troy, Tamara L., Lorenz, Alexander D., Thennadil, Suresh, Welch, James Matthew
• Primary Examiner(s): WALLENHORST, MAUREEN
• Application Number:
  US09/502,877
• Time in Patent Office: 999 Days
• Field of Search: 436/8, 436/63, 436/71, 436/164, 436/166, 738/664, 252/408.1, 600/309, 600/310, 600/316, 600/365
• US Class Current: 436/8
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 2560/0233 Optical standards
• 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 5/1075 for measuring dimensions by non-invasive methods, e.g. for determining thickness of tissue layer A61B8/0858 takes precedence
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00
• CPC Class Codes: G01N 21/274 Calibration, base line adjustment, drift correction
• CPC Class Codes: G01N 21/359 using near infrared light
• CPC Class Codes: G01N 21/4785 Standardising light scatter apparatus; Standards therefor
• CPC Class Codes: G01N 21/49 within a body or fluid
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems
• CPC Class Codes: Y10T 436/10 Composition for standardization, calibration, simulation, stabilization, preparation or preservation; processes of use in preparation for chemical testing

Abstract

The invention provides a class of samples that model the human body. This family of samples is based upon emulsions of oil in water with lecithin acting as the emulsifier. These solutions that have varying particle sizes may be spiked with basis set components (albumin, urea and glucose) to simulate skin tissues further. The family of samples is such that other organic compounds such as collagen, elastin, globulin and bilirubin may be added, as can salts such as Na⁺, K⁺ and Cl⁻. Layers of varying thickness with known index of refraction and particle size distributions may be generated using simple crosslinking reagents, such as collagen (gelatin). The resulting samples are flexible in each analyte'"'"'s concentration and match the skin layers of the body in terms of the samples reduced scattering and absorption coefficients, μm_s and μm_a. This family of samples is provided for use in the medical field where lasers and spectroscopy based analyzers are used in treatment of the body. In particular, knowledge may be gained on net analyte signal, photon depth of penetration, photon radial diffusion, photon interaction between tissue layers, photon density (all as a function of frequency) and on instrument parameter specifications such as resolution and required dynamic range (A/D bits required). In particular, applications to delineate such parameters have been developed for the application of noninvasive glucose determination in the near-IR region from 700 to 2500 nm with an emphasis on the region 1000 to 2500 nm (10,000 to 4,000 cm−¹).

Claims

1. A human tissue surrogate material, comprising:

an emulsion comprising oil in water, and further comprising lecithin;

wherein said lecithin comprises an emulsifier;

wherein said emulsion models optical characteristics of skin tissue; and

wherein said emulsion contains no glycerol therein.

2. The human tissue surrogate of claim 1, wherein said oil comprises castor oil or other oils that can form particles approximately 0.2 to 3.0 μ

m in size.

3. The human tissue surrogate of claim 2, wherein said castor oil has either a Gaussian or bimodal particle size distribution with peaks centered anywhere from 0.2 to 3.0 μ

m.

4. The human tissue surrogate of claim 2, wherein castor oil droplets are suspended in an aqueous solution with said lecithin.

5. The human tissue surrogate of claim 2, wherein particle size distribution has two widely separated peaks near 0.4 and 3.0 μ

m.

6. The human tissue surrogate of claim 1, wherein observed intensity in 2^nd overtone (1000 to 1450 nm), 1st overtone (1450 to 2000 nm) and combination band (2000 to 2500 nm) spectral regions of a human arm is closely modeled by said tissue surrogate.

7. The human tissue surrogate of claim 1, further comprising additional organic components.

8. The human tissue surrogate of claim 7, wherein said additional organic components comprise any of collagen, elastin, globulin, lactic acid bilirubin and electrolytes.

9. The human tissue surrogate of claim 8, wherein said electrolytes comprise any of Na⁺, K⁺ and Cl⁻

.

10. The human tissue surrogate of claim 1, further comprising a crosslinker.

11. The human tissue surrogate of claim 10 wherein said crosslinker comprises collagen.

12. The human tissue surrogate of claim 11, further comprising:

albumin having a concentration of 0 to 6000 mg/dL;

globulin having a concentration of 0 to 2500 mg/dL;

urea having a concentration of 0 to 200 mg/dL;

and glucose having a concentration of 0 to 800 mg/dL.

13. The human tissue surrogate of claim 12, wherein said water, oil and lecithin emulsion comprises 1.5 to 15% of said tissue surrogate.

14. The human tissue surrogate of claim 13, wherein said water, oil and lecithin emulsion comprises 2 to 4% of said tissue surrogate.

15. The human tissue surrogate of claim 11, wherein said collagen comprises gelatin.