Implantable optical measurement device and method for using same

• US 6,216,022 B1
• Filed: 06/22/2000
• Issued: 04/10/2001
• Est. Priority Date: 06/22/2000
• Status: Expired due to Fees

• Current Assignee: Biosafe Laboratories, Inc.
• Original Assignee: Biosafe Laboratories, Inc.
• Inventors: Ebner, Shannon J., Tyrrell, Steven P.
• Primary Examiner(s): WINAKUR, ERIC FRANK
• Application Number:
  US09/599,139
• Time in Patent Office: 292 Days
• Field of Search: 600/310, 600/316, 600/322, 600/323, 600/326, 600/327, 600/339, 600/341, 600/342, 600/473, 600/476
• US Class Current: 600/310
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1459 invasive, e.g. introduced into the body by a catheter A61B5/1464 takes precedence

Abstract

A method and apparatus for making an optical measurement through a tissue such as skin of a person includes an implantable optical system having an entry window, an exit window, a reference path between the windows and a measurement path between the windows. The reference path includes a reference element with known optical characteristics, and the measurement path is in fluid communication with the body fluids of the person. A first optical signal is directed through the tissue of the person, the entry window, the reference path, the exit window and the tissue of the person to an external optical sensor, and a second optical signal is directed through the same portion of the tissue of the person, the entry window, the measurement path, the exit window and the same portion of the tissue of the person to the external optical sensor. Variations in the optical effects of the tissue on the measurement can be measured with the second optical signal and used to improve measurement accuracy. A blocking element fills a measurement region in the measurement path when measurements are not being made. This blocking element prevents the accumulation of tissue in the measurement region.

Claims

1. An implantable optical system comprising:

a biocompatible housing adapted to be inserted under a tissue of a person, said housing comprising an entry window and an exit window, said housing configured to admit biological fluids to a measurement region positioned in an optical path extending between the windows;

a blocking element mounted in the housing to move between a first position, in which the blocking element substantially occupies the measurement region, and a second position, in which the blocking element is positioned outside the measurement region.

2. The invention of claim 1 further comprising:

a biasing element biasing the blocking element to the first position;

a pressure-receiving element movably mounted with respect to at least a portion of the housing, said pressure-receiving element coupled with the blocking element to move the blocking element to the second position in response to applied pressure.

3. The invention of claim 2 wherein the pressure-receiving element comprises first and second links coupled at a hinge axis, said first link reacting against the blocking element, said second link reacting against the housing.

4. The invention of claim 3 wherein the housing comprises an upper surface, wherein the windows are positioned in the upper surface, wherein the blocking element slides along a sliding axis, and wherein the hinge axis and the sliding axis are parallel to the upper surface.

5. The invention of claim 4 wherein the hinge axis is perpendicular to the sliding axis.

6. The invention of claim 1 further comprising:

a reference element positioned in a second optical path extending between windows; and

an optical switch mounted in the housing and operative to direct light through a selected one of the first and second optical paths in response to a control signal.

7. The invention of claim 6 wherein the optical switch comprises a movable reflector.

8. The invention of claim 6 wherein the optical switch comprises a movable shutter.

9. The invention of claim 6 wherein the optical switch comprises a variable opacity element.

10. The invention of claim 1 further comprising:

means for selectively moving the blocking element to the second position.

11. The invention of claim 10 further comprising:

means for biasing the blocking element to the first position.

12. A method for making an optical measurement through a tissue of a person, said method comprising:

(a) implanting an optical system under a tissue of a person, said optical system comprising an entry window, an exit window, a measurement path extending between the windows, and a measurement region in the measurement path, said measurement region accessible to body fluids of the person;

(b) positioning a blocking element in the measurement region;

(c) moving the blocking element out of the measurement region;

then

(d) directing at least one optical signal through the tissue of the person, the entry window, the measurement path, the exit window, and the tissue of the person, to an optical sensor; and

then

(e) re-positioning the blocking element in the measurement region.

13. The method of claim 12 wherein acts (b) and (e) position the blocking element to substantially fill the measurement region.

14. The method of claim 12 wherein act (c) comprises applying pressure to the optical system, thereby moving the blocking element out of the measurement region.

15. The method of claim 12 wherein the optical system further comprises a reference optical path between the windows, and wherein the method comprises:

(f) directing another optical signal through the tissue of the person, the entry window, the reference optical path, the exit window, and the skin of the person to the optical sensor.

16. The method of claim 15 wherein act (f) is performed after act (c) and before act (e).

17. The method of claim 15 wherein the optical system implanted in (a) comprises an optical switch operative to direct light through a selected one of the measurement and reference optical paths in response to a control signal.

18. The method of claim 17 wherein act (d) comprises the act of generating the control signal to cause the optical switch to direct light through the measurement optical path.

19. The method of claim 18 wherein act (f) comprises the act of generating the control signal to cause the optical switch to direct light through the reference optical path.

20. The method of claim 15 wherein the optical signals of acts (d) and (f) pass through substantially the same portions of the tissue of the person.