Surgery – Diagnostic testing – Measuring or detecting nonradioactive constituent of body...
Reexamination Certificate
2000-06-22
2001-04-10
Winakur, Eric F. (Department: 3736)
Surgery
Diagnostic testing
Measuring or detecting nonradioactive constituent of body...
C600S316000
Reexamination Certificate
active
06216022
ABSTRACT:
BACKGROUND
The present invention relates to systems for optically measuring biological parameters, such as glucose concentration for example.
There has been substantial activity in the field of optical measurement of biological analytes. One approach is to make such measurements using noninvasive optical systems that direct an optical signal against the skin of a person and measure optical characteristics of reflected, transmitted or scattered light. Messerschmidt U.S. Pat. No. 5,823,951, Mendelson U.S. Pat. No. 5,277,181, Clarke U.S. Pat. No. 5,222,495, and Yamaguchi U.S. Pat. No. 5,127,406 are examples of such noninvasive measurement systems. A recurring problem with this approach is that the skin of the person absorbs, scatters and otherwise affects optical signals to a substantial degree, thereby interfering with the desired measurement. Interference of this type can vary substantially from person to person, and such variations can make it difficult or impossible to achieve high accuracy noninvasive optical measurements.
In principle, it would be possible to implant an entire optical measuring system, thereby eliminating adverse effects of the skin on the optical measurement. See Van Heuvelen U.S. Pat. No. 4,704,029. However, such an implantable system would require power for operation which would represent yet another disadvantage.
Various approaches have been suggested for combining an external optical source and sensor with an implantable optical system. See, for example, Rao U.S. Pat. No. 5,628,310, Palti U.S. Pat. No. 5,368,028, and Slate U.S. Pat. No. 5,605,152. The system described in the Slate patent overcomes the problem of skin interference by using a fiber optic cable to interconnect the internal and external portions of the system. The devices disclosed in the Rau and PaIti patents suffer from the disadvantage that variations in the optical characteristics of the skin can adversely effect the optical measurement.
Thus, a need presently exists for an improved implantable optical system that reduces or eliminates measurement problems associated with variations in the optical characteristics of the skin.
SUMMARY
The preferred embodiments described below provide an implantable optical system intended to be placed under a tissue such as the skin of a person. This optical system includes an entry window, an exit window, and a measurement path between the windows. The measurement path traverses a measurement region that is open to body fluids. A blocking element is normally positioned in the measurement region to prevent tissue from entering the measurement region. This blocking element is temporarily removed from the measurement region to allow a measurement to be made, and then the blocking element is replaced.
Preferably, the optical system also includes a reference path. The reference path includes a reference element that provides a predetermined optical characteristic. In use, a first optical signal is directed through the tissue of the person, the entry window, the reference path, the exit window, and the tissue to an optical sensor. Then a second optical signal is directed through the tissue, the entry window, the measurement path, the exit window, and the tissue to the optical sensor. The first and second optical signals pass through the same portion of the tissue, and thus the first optical signal can be used to compensate for absorption, scattering and other optical effects of the tissue on the second optical signal.
The foregoing paragraphs have been provided by way of introduction, and they are not intended to limit the scope of the following claims.
REFERENCES:
patent: 4704029 (1987-11-01), Van Huuvelen
patent: 4803992 (1989-02-01), Lemelson
patent: 5127406 (1992-07-01), Yamaguchi
patent: 5222495 (1993-06-01), Clarke et al.
patent: 5277181 (1994-01-01), Mendelson et al.
patent: 5368028 (1994-11-01), Palti
patent: 5598841 (1997-02-01), Taniji et al.
patent: 5605152 (1997-02-01), Slate et al.
patent: 5628310 (1997-05-01), Rao et al.
patent: 5823951 (1998-10-01), Messerschmidt
patent: 6002954 (1999-12-01), Van Antwerp et al.
patent: 6049727 (2000-04-01), Crothall
Ebner Shannon J.
Tyrrell Steven P.
Biosafe Laboratories, Inc.
Brinks Hofer Gilson & Lione
Winakur Eric F.
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