Systems and methods for extending the useful life of optical sensors

• US 20050236580A1
• Filed: 04/26/2004
• Published: 10/27/2005
• Est. Priority Date: 04/26/2004
• Status: Active Grant

• Current Assignee: Senseonics, Incorporated (Senseonics Holdings, Inc.)
• Original Assignee: Sensors For Medicine and Science Incorporated
• Inventors: Lorenz, Carrie R., Colvin, Arthur Earl Jr., Lesho, Jeffery C.
• Granted Patent: US 7,375,347 B2
• Time in Patent Office: Days
• US Class Current: 250/459.100
• CPC Class Codes: A61B 2560/0209 adapted for power saving
• 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 5/14556 by fluorescence A61B5/14555 takes precedence
• CPC Class Codes: A61B 5/1459 invasive, e.g. introduced into the body by a catheter A61B5/1464 takes precedence
• CPC Class Codes: G01N 21/6428 Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes" in vivo A61B5/00; immunoassay G01N33/53

Abstract

The present invention provides a method for increasing the lifetime of an optical sensor. In one aspect, the method includes the step of configuring the optical sensor so that the duty cycle of sensor'"'"'s radiant source is less than 100% over a continuous period amount of time when the sensor is periodically obtaining data regarding an analyte. By operating the sensor according to the above inventive method, the indicator molecules of the optical sensor are not excited during the entire continuous period of time during which the sensor is needed to provide data regarding the presence or concentration of a substance. Thus, the method increases the life of the indicator molecules.

Claims

1. A method for increasing the lifetime of an optical sensor that, when active, is configured to obtain data regarding the presence or concentration of a substance within an area, wherein the optical sensor includes (i) indicator molecules having an optical characteristic that is affected by the presence of the substance and (ii) a radiant source, the method comprising:

(a) utilizing the optical sensor configured so that the duty cycle of the radiant source is greater than 0% but less than 100% during the period of time when the optical sensor is active;

(b) positioning the optical sensor at a location within the area;

(c) activating the optical sensor for a period of Z amount of time after performing step (b), wherein Z is greater than 0;

(d) operating the radiant source so that the duty cycle of the radiant source is greater than 0% but less than 100% during said Z amount of time when the optical sensor is active; and

(e) de-activating the optical sensor after said Z amount of time has elapsed.

2. The method of claim 1, wherein the duty cycle is less than or equal to about 50%.

3. The method of claim 1, wherein the duty cycle is less than or equal to about 10%.

4. The method of claim 1, wherein the duty cycle is less than or equal to about 1%.

5. The method of claim 1, wherein the duty cycle is less than or equal to about 0.1%.

6. The method of claim 1, wherein Z is about 0.5 to about 20 minutes.

7. The method of claim 1, wherein Z is about 1 to about 10 minutes.

8. The method of claim 1, wherein Z is about 7 minutes.

9. The method of claim 1, wherein Z is about 2 minutes.

10. The method of claim 1, wherein the optical sensor is activated for approximately 200 milliseconds every approximately 2 minutes.

11. The method of claim 10, wherein the radiant source is activated for approximately 100 milliseconds of the approximately 200 milliseconds the optical sensor is activated.

12. The method of claim 1, wherein the indicator molecules are fluorescent.

13. The method of claim 1, wherein the radiant source comprises a light emitting diode (LED).

14. The method of claim 1, wherein the drive current used to drive the LED is about less than or equal to 3 mA.

15. The method of claim 14, wherein the drive current used to drive the LED is about less than or equal to 2 mA.

16. The method of claim 14, wherein the drive current used to drive the LED is about less than or equal to 1 mA.

17. The method of claim 1, wherein the sensor further includes a cooling element.

18. The method of claim 1, wherein the indicator molecules are absorbance-type indicator molecules.

19. A method for increasing the useful lifetime of an optical sensor that provides data regarding the presence or concentration of a substance within an area, wherein the optical sensor includes (i) indicator molecules having an optical characteristic that is affected by the presence of the substance, (ii) a radiant source and (iii) a photodetector, the method comprising:

(a) positioning the sensor in a location in the area;

(b) activating the sensor, thereby placing the sensor in an active state;

(c) after performing step (b), utilizing the radiant source configured so that the radiant source outputs electromagnetic waves having a frequency within a certain frequency range and having an amplitude within a certain amplitude range;

(d) obtaining a first measurement from an output of said photodetector at some point in time after performing step (c);

(e) after Y amount of time has elapsed since step (c) was performed and while the sensor is still in an active state, utilizing the radiant source configured so that the radiant source does not output electromagnetic waves or utilizing the radiant source configured so that the radiant source outputs electromagnetic waves having a frequency that is less than the lowest frequency of said certain frequency range and/or having an amplitude that is less than the lowest amplitude of said certain amplitude range;

(f) utilizing, after X amount of time has elapsed since step (c) was performed and while the sensor is in the active state, the radiant source configured so that the radiant source outputs electromagnetic waves having a frequency within said certain frequency range and having an amplitude within said certain amplitude range, wherein X is greater than zero and greater than Y;

(g) obtaining a second measurement from an output of said photodetector at some point in time after performing step (f); and

(h) after N amount of time has elapsed since step (f) was performed and while the sensor is in the active state, utilizing the radiant source configured so that the radiant source does not output electromagnetic waves or utilizing the radiant source configured so that the radiant source outputs electromagnetic waves having a frequency that is less than the lowest frequency within said certain frequency range and/or having an amplitude that is less than the lowest amplitude within said certain amplitude range, wherein N is less than X.

20. The method of claim 19, wherein X is less than about 5 minutes.

21. The method of claim 19, wherein Y is less than X/2.

22. The method of claim 19, wherein Y is less than or equal to X/10.

23. The method of claim 19, wherein Y is less than one second.

24. The method of claim 19, wherein the indicator molecules are fluorescent.

25. The method of claim 19, wherein the radiant source comprises a light emitting diode (LED).

26. The method of claim 25, wherein step (b) includes the step of driving the LED with a drive current, wherein the drive current is about equal to the LED'"'"'s threshold drive current.

27. The method of claim 19, wherein the step of activating the sensor comprises the step of providing power to electrical components of the sensor.

28. The method of claim 19, wherein Y and N are both about 150 milliseconds and X is about 1 second.

29. An optical sensor, comprising:

indicator molecules having an optical characteristic that is affected by the presence of a substance;

a light source; and

a duty cycle controller for repeatedly turning on the light source for an amount of time and then turning it off for an amount of time while the optical sensor is being utilized to sense the presence or concentration of the substance.

30. The optical sensor of claim 29, further comprising a photodetector that receives light emitted from the indicator molecules.

31. The optical sensor of claim 29, wherein, while the optical sensor is being utilized to sense the presence or concentration of the substance, the duty cycle controller is configured to turn the light source on for not more than Y amount of time every X amount of time, where X is greater than Y.

32. The optical sensor of claim 31, wherein Y is less than or equal to about X/2.

33. The optical sensor of claim 31, wherein Y is about 150 milliseconds and X is about 1 second.

34. The optical sensor of claim 31, wherein Y is about 100 milliseconds and X is about 1 second.

35. The optical sensor of claim 31, wherein Y is about 50 milliseconds and X is about 1 second.

36. An optical sensor, comprising:

indicator molecules having an optical characteristic that is affected by the presence of a substance;

a light source; and

control means for repeatedly turning on the light source for an amount of time and then turning it off for an amount of time while the optical sensor is being utilized to sense the presence or concentration of the substance.

37. The optical sensor of claim 36, further comprising a photodetector that receives light emitted from the indicator molecules.

38. The optical sensor of claim 37, wherein, while the optical sensor is being utilized to sense the presence or concentration of the substance, the control means turns the light source on for not more than Y seconds every X seconds, where X is greater than Y.

39. The optical sensor of claim 38, wherein Y is less than or equal to about X/2.

40. The optical sensor of claim 38, wherein Y is about 150 milliseconds and X is about 1 second.

41. An optical sensor, comprising:

indicator molecules having an optical characteristic that is affected by the presence of a substance;

a light source that, when turned on, illuminates the indicator molecules;

a photoelectric transducer that receives light emitted from the indicator molecules; and

a cooling element configured to reduce the temperature of the indicator molecules.

42. The optical sensor of claim 41, further comprising a duty cycle controller for repeatedly turning on the light source for an amount of time and turning off the light source for an amount of time while the optical sensor is being utilized to sense the presence or concentration of the substance.

43. The optical sensor of claim 42, wherein, while the optical sensor is being utilized to sense the presence or concentration of the substance, the duty cycle controller turns the light source on for not more than Y seconds every X seconds, where X is greater than Y.

44. The optical sensor of claim 43, wherein Y is less than or equal to about X/2.

45. A method for increasing the useful lifetime of an optical sensor that, when in an active state, obtains data regarding the presence or concentration of a substance within an area at least once every X amount of time for a continuous Z amount of time, wherein the optical sensor includes indicator molecules having an optical characteristic that is affected by the presence of the substance and a light source for exciting the indicator molecules, the method comprising:

placing the optical sensor at a location within the area; and

exciting the indicator molecules for a total of not more than Y amount of time during the Z amount of time, wherein Y is less than Z.

46. The method of claim 45, wherein Y is less than z/2.

47. The method of claim 45, wherein Y is less than z/10.

48. The method of claim 45, wherein Y is less than z/100.

49. The method of claim 45, wherein the step of placing the optical sensor at a location within the area comprises implanting the optical sensor in a human being.

50. The method of claim 49, wherein the substance is a biological analyte.

51. The method of claim 50, wherein the biological analyte is glucose.

52. The method of claim 45, wherein Z is less than about 10 minutes.

53. The method of claim 52, wherein X is about 1 second.

54. A method for determining the useful lifetime of an optical sensor, comprising:

(a) continuously exposing indicator molecules to light emitted from a light source;

(b) periodically determining the output intensity of the indicator molecules;

(c) determining the amount of time it takes for the output intensity of the indicator molecules to degrade by a predetermined amount;

(d) determining an average expected amount of time that the optical sensor'"'"'s light source will be on per unit time; and

(e) determining the useful product life by dividing the amount of time determined in step (c) by the amount of time determined in step (d).

55. A method for determining a maximum duty cycle for a light source of an optical sensor, comprising:

(a) continuously exposing indicator molecules to light emitted from a light source;

(b) periodically determining the output intensity of the indicator molecules;

(c) determining the amount of time it takes for the output intensity of the indicator molecules to degrade by a predetermined amount;

(d) determining the total cumulative activation time for the sensor; and

(e) determining the maximum duty cycle by dividing the amount of time determined in step (c) by the amount of time determined in step (d).