Frequency estimation of electro-islet-graphy

• US 6,884,215 B1
• Filed: 05/28/1999
• Issued: 04/26/2005
• Est. Priority Date: 05/28/1998
• Status: Expired due to Fees

• Current Assignee: Carmel Biosensors Ltd. (Medtronic Plc)
• Original Assignee: Carmel Biosensors Ltd. (Medtronic Plc)
• Inventors: Charash, Dan
• Primary Examiner(s): WINAKUR, ERIC FRANK
• Application Number:
  US09/530,684
• Time in Patent Office: 2,160 Days
• Field of Search: 600/300, 600/309, 600/345, 600/347, 600/365, 600/407, 128/897, 128/898
• US Class Current: 600/309
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/24 Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
• CPC Class Codes: A61B 5/425 pancreas
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal

Abstract

The fundamental frequency of EIG events is determined directly, without first detecting the events themselves. Use is made of an analysis window containing more than one event (3-5). Techniques (1-8) are utilized which are somewhat similar to those utilized to detect, and estimate pitch in speech processing. The invention is based on two important biological discoveries. The first is that the EIG is generated by a functional pace maker. The second is that the EIG signal is quasi-periodic most of the time. The use of pitch detection algorithms is based on the essentially quasi-periodic nature of the EIG signal. Quasi-periodic means that the intervals between successive events are not exactly identical, but may vary slightly, that the amplitude and shape of successive events may also exhibit some variance.

Claims

1. A method for monitoring biological micro-structure activity which produces detectable signals characterizing events, comprising the steps of estimating the fundamental frequency of the occurrence of events from the detectable signals, without detecting the occurrence of individual events, wherein the estimating step includes an autocorrelation operation.

2. The method of claim 1 further including one of the following steps:

estimating the fundamental frequency based upon a lower autocorrelation value disposed among several adjacent peaks;

treating “

unvoiced”

segments of the detectable signal as undecided as to pitch and estimating the pitch of those segments through subsequent processing;

seeking to estimate the fundamental frequency in the range of 0.25 to 5 Hertz,

utilizing an analysis window duration in the range of several seconds;

performing a pre-processing operation which has the effect of increasing the effective duration of an event; and

utilizing an autocorrelation process which performs segmented autocorrelation.

3. A method for monitoring biological micro-structure activity which produces detectable signals characterizing events, comprising the steps of estimating the fundamental frequency of the occurrence of events from the detectable signals, without detecting the occurrence of individual events, further comprising the step of using the number of “

unvoiced”

windows within a predetermined time as a measure of a blood constituent level of a patient.

4. A method for monitoring biological micro-structure activity which produces detectable signals characterizing events, comprising the steps of estimating the fundamental frequency of the occurrence of events from the detectable signals, without detecting the occurrence of individual events, further comprising the step of using a sureness grade as measure of a blood or tissue constituent level of a patient.

5. In a system for monitoring biological micro-structure activity which produces detectable signals characterizing events, a sensor capable of receiving the sensible signals and a processor including a module for estimating the fundamental frequency of the occurrence of events from the detectable signals, without first detecting the occurrence of individual events, wherein the processor further comprises a module for producing an analysis window during which events are analyzed, the analysis window spanning more than one event, wherein the module for estimating includes components to perform an autocorrelation operation.

6. The system of claim 5 wherein the module for estimating further includes one of the following submodules:

a submodule which estimates the fundamental frequency based upon a lower autocorrelation value disposed among several adjacent peaks;

a sub-module which identifies “

unvoiced”

segments of the detectable signal as undecided as to pitch, the pitch of those segments being estimated by a subsequent processing submodule;

a submodule which controls the estimate of the fundamental frequency to be in the range of 0.25 to 5 Hertz;

a submodule controlling the analysis window to have a duration in the range of several seconds; and

a submodule performing a pre-processing operation which has the effect of increasing the effective duration of an event.

7. In a system for monitoring biological micro-structure activity which produces detectable signals characterizing events, a sensor capable of receiving the sensible signals and a processor including a module for estimating the fundamental frequency of the occurrence of events from the detectable signals, without first detecting the occurrence of individual events, wherein the processor further comprises a module for producing an analysis window during which events are analyzed, the analysis window spanning more than one event, wherein the processor is constructed to perform a segmented autocorrelation process.

8. In a system for monitoring biological micro-structure activity which produces detectable signals characterizing events, a sensor capable of receiving the sensible signals and a processor including a module for estimating the fundamental frequency of the occurrence of events from the detectable signals, without first detecting the occurrence of individual events, wherein the module for estimating includes components to perform an autocorrelation operation.

9. In a system for monitoring biological micro-structure activity which produces detectable signals characterizing events, a sensor capable of receiving the sensible signals and a processor including a module for estimating the fundamental frequency of the occurrence of events from the detectable signals, without first detecting the occurrence of individual events, wherein the processor is constructed to perform a segmented autocorrelation process.

10. A method for monitoring biological micro-structure activity which produces detectable signals characterizing events, comprising the steps of estimating the fundamental frequency of the occurrence of events from the detectable signals, without detecting the occurrence of individual events, wherein events are analyzed during an analysis window which spans more than one event, wherein the estimating step includes an autocorrelation operation.