Method for improving signal-to-noise in clinical spectrometric procedures

• US 5,795,292 A
• Filed: 05/02/1996
• Issued: 08/18/1998
• Est. Priority Date: 10/14/1994
• Status: Expired due to Term

• Current Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Original Assignee: Somanetics Corporation (Medtronic Plc)
• Inventors: Gonopolskiy, Oleg, Scheuing, Richard S., Lewis, Gary D., Messing, Wayne P.
• Primary Examiner(s): Cohen, Lee S.
• Application Number:
  US08/641,875
• Time in Patent Office: 838 Days
• Field of Search: 128/633, 128/664-667, 128/639, 128/640, 128/901, 600/323, 600/473, 600/476, 600/310, 600/322
• US Class Current: 600/323
• CPC Class Codes: A61B 2562/182 Electrical shielding, e.g. using a Faraday cage
• CPC Class Codes: A61B 5/14553 specially adapted for cerebral tissue
• CPC Class Codes: A61B 5/7217 of noise originating from a therapeutic or surgical apparatus, e.g. from a pacemaker

Abstract

A method of conducting clinical examination procedures by use of electrically actuated spectrometric apparatus, of the type which uses a sensor that is placed in contact with the patient to transmit and receive electromagnetic energy of selected wavelengths for non-invasive in vivo examination of a selected area on the body, in which a conductive member is placed in contact with the patient near or at the location of the sensor and connected to the signal-processing circuitry of the processor for the spectrometric signals in a manner such that the examination signals have significantly less noise content than would otherwise be true. In so doing, the signal-processing circuitry is isolated from the power supply circuitry, and the sensor and conductive member are preferably coupled to the processor by use of an isolation preamplifier, such that the signal-processing ground potential reference is maintained separate and distinct from the power supply ground. The specially-grounded conductive member that is placed in contact with the patient is preferably made part of the sensor itself, as by using a conductive material on at least part of the sensor surface that is placed in contact with the patient, and such a conductive surface element may comprise a flexible outer coating or layer of a compliant sensor which is conformable to the shape of the patient extremity to which it is applied. In this manner, the surface potential of the patient at the location of the sensor may be equalized with that of the signal-processing circuitry ground potential to substantially reduce signal noise content, and ambient sources of electrical noise may be effectively shielded as well.

Claims

1. A method of conducting clinical patient examinations by spectrometric apparatus, comprising the steps:

placing an electrically actuated sensor in contact with the patient for receiving and transmitting selected energy wavelength signals between the sensor and the patient;

coupling the sensor to an electrically powered controller and processor having electrical power circuits which are electrically isolated from at least portions of signal-processing circuits thereof to transmit patient examination signals to said signal-processing circuits; and

electrically coupling at least a selected surface portion of said patient to said portions of said signal-processing circuits of said controller and processor which are electrically isolated from said power circuits thereof, to thereby establish and maintain substantially the same electrical potential between said selected surface portion of said patient and said portions of said processing circuits to which said selected surface portion is coupled and thereby substantially reduce the electrical noise content of said examination signals transmitted from said sensor to said processor.

2. The method set forth in claim 1, wherein said step of electrically coupling at least a selected portion of said patient to said signal-processing circuits is done by placing an electrically conductive member in direct physical contact with a selected surface area of the patient.

3. The method set forth in claim 2, wherein said step of electrically coupling is done by embodying said conductive member in said sensor and applying said sensor to said patient with said conductive member disposed in contact with the surface of said patient.

4. The method set forth in claim 3, wherein said electrically conductive member is embodied in a softly compliant outer layer of said sensor arranged for yieldable direct contact with the patient.

5. The method set forth in claim 2, wherein said signal-processing circuits have a signal ground potential reference and said step of electrically coupling is additionally done by electrically connecting said conductive member from said patient to the signal ground potential reference of said signal-processing circuits.

6. The method set forth in claim 2, wherein said electrically conductive member is secured in place against said patient by using electrically conductive adhesive therebetween.

7. The method set forth in claim 1, including the step of electrically isolating the electrical power circuits of said controller and processor from the signal-processing circuits thereof by connecting an isolation preamp having isolated power and signal-processing paths between said sensor on the one hand and said controller and processor on the other hand.

8. In a method of conducting clinical patient examination by use of electrically operated spectrometric apparatus of the type which transmits selected energy wavelengths to the patient for examination purposes and receives corresponding examination signals back from the patient, the improvement which comprises the step of placing an electrically conductive member in contact with a selected surface area of the patient, and using said conductive member to maintain at least said selected area of said patient at a predetermined electrical potential, to thereby substantially reduce the amount of electrical noise otherwise present in the examination signals received from the patient.

9. The improved method according to claim 8, wherein said examination signals have a signal ground potential reference and said electrically conductive member placed in contact with the patient is used by connecting it electrically to said ground potential reference for said examination signals.

10. The improved method according to claim 9, wherein electrical power circuits of said apparatus have a ground potential reference, and including the step of isolating said examination signal ground potential reference from said electrical power circuits ground potential reference.

11. In a method of conducting clinical patient examinations by spectrometric procedures in which selected energy wavelength signals are transmitted to the patient and resulting examination signals are received and coupled to an electrically powered processor having signal-processing circuits and electrical power circuits, for processing said clinical patient data, the improvement comprising the steps of:

using a sensor disposed in contact with said patient to transmit said energy wavelength signals thereto and receive said examination signals by electrically actuated components physically associated with said sensor;

electrically coupling said electrically actuated components to said processing circuits of said processor, for transmittal and receipt of said energy signals and said examination signals therebetween;

placing an electrically conductive member in contact with said patient, and establishing an electrically conductive path between said conductive member and said processor, whereby the electrical potential of said patient in the area contacted by said conductive member may be accessed; and

electrically isolating said conductive member and conductive path from the electrical power circuits of said processor, and establishing and maintaining substantially the same electrical potential between said conductive member and at least portions of said signal-processing circuits to thereby substantially reduce the electrical noise content of said examination signals transmitted to said processor.

12. The improved method according to claim 11, wherein said sensor is disposed in contact with said patient by conforming a softly compliant component against a surface area of the patient.

13. The improved method according to claim 11, wherein said electrically conductive member is secured in contact with the patient by using conductive adhesive therebetween.

14. The improved method according to claim 13, wherein said conductive member and said sensor are secured in contact with said patient by using adhesive therebetween.