ELECTROMAGNETIC FLOWMETER

• US 3,759,247 A
• Filed: 07/01/1971
• Issued: 09/18/1973
• Est. Priority Date: 08/24/1970
• Status: Expired due to Term

• Current Assignee: Hans J. Broner, Henri Georges Doll
• Original Assignee: Hans J. Broner, Henri Georges Doll
• Inventors: Doll, Henri Georges, Broner, Hans J.
• Primary Examiner(s): Howell, Kyle L.
• Application Number:
  US05/158,697
• Time in Patent Office: 810 Days
• Field of Search: 128/2.5F,2.5R,2.5V,2.5P,2R 73/194EM
• US Class Current: 600/407
• CPC Class Codes: A61B 5/0265 using electromagnetic means, e.g. electromagnetic flowmeter
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: G01F 1/58 by electromagnetic flowmeters

Abstract

A noninvasive electromagnetic flowmeter particularly adapted to measure arterial blood flow in human beings is provided. A homogeneous magnetic field is produced in the region of the artery under measurement by means of at least one electromagnetic coil or a permanent magnet suitably positioned near the human being. Blood flow induced signals are sensed by electrodes placed on the skin adjacent the artery and fed to a measurement and control circuit. Electrocardiogram signals are sensed by a second pair of electrodes placed on the body near the heart and synchronize the operation of this system. One embodiment of the control and measurement system comprises a pair of auxiliary electrodes located where a strong and sharp cardiogram pulse can be repeatedly obtained to be used as a synchronizing signal and as a clock, at least one coil of large enough size having enough turns of wire to be adequate for the production of a strong and homogeneous magnetic field in the region of the artery under study, a source of D.C. current to feed that coil, means to reverse that D.C. current after a given number of heart cycles in accordance with a program controlled by the sychronizing signal, a pair of measuring electrodes placed on the skin adjacent the artery, an amplifier to amplify the signal appearing between said measuring elecrodes, with filtering means to eliminate the D.C. unbalance of the electrodes and the high frequency noise, means to paralyze the amplifier and to reverse its output during current reversal, and means synchronized by the synchronizing signal to average the pulsatile signal measured between the measuring electrodes during successive heart cycles so as to extract the repetitive wave shape of the blood flow pulses from the large random noise in which it is otherwise buried. In another embodiment of the control and measurement system, the coil in which a stable current is maintained during all the measuring intervals, as described in the paragraph above, is replaced by an electrically reversible permanent magnet. This permanent magnet is surrounded by a magnetizing coil in which DC current pulses of short duration are passed only at the times when the polarity of the magnetic field, and therefore the polarity of the permanent magnet, have to be reversed. There is no current in the magnetizing coil during the intervals when measurements of blood flow cycles are made and averaged. In still another embodiment of the control and measurement system, a permanent magnet is also used, but the reversal of the magnetic field, at the times when it is needed, is obtained by mechanically reversing or displacing the permanent magnet.

Claims

1. An electromagnetic flowmeter for measuring the blood flow pulse in a blood Vessel of a living being comprising:

first sensing means adapted to be positioned on the skin of the being at a location where a strong and sharp cardiogram pulse can be repeatedly obtained to be used as a synchronizing signal and as a clock;

means connected to said first sensing means for providing a synchronizing signal and a clock;

a permanent magnet for producing a strong and homogeneous magnetic field in the region of said vessel, means for reversing said magnetic field after a given number of heart cycles in accordance with a program controlled by said synchronizing signal, said magnetic field reversing means including a magnetizing coil through which a short duration pulse of D.C. current is applied to reverse the polarity of said permanent magnet;

second sensing means adapted to be placed on the skin or in the tissue of said being at a location adjacent said vessel;

amplifier means for amplifying the signal sensed by said second sensing means;

means for reversing the polarity of said amplifier means during said reversal of said magnetic field; and

measuring means synchronized by the synchronizing signal for averaging the pulsatile signal sensed by said second sensing means during a given number of heart cycles while the magnetic field is stable at one polarity, and for averaging an equal number of heart cycles after reversal of said polarity of both said magnetic field and said measuring circuit;

whereby there is obtained the wave shape of the blood flow pulses free from both the local cardiogram and the random noise.

2. The electromagnetic flowmeter of claim 1, including a source of D.C. current pulses for reversing the magnetization of said coil.

3. The electromagnetic flowmeter of claim 2, also including a pair of pole pieces supported at the respective ends of said permanent magnet.

4. An electromagnetic flowmeter for measuring the blood flow pulse in a blood vessel of a living being comprising:

first sensing means adapted to be positioned on the skin of the being at a location where a strong and sharp cardiogam pulse can be repeatedly obtained to be used as a synchronizing signal and as a clock;

means connected to said first sensing means for providing a synchronizing signal and a clock;

a permanent magnet for producing a strong and homogeneous magnetic field in the region of said vessel;

means for reversing said magnetic field after a given number of heart cycles in accordance with a program controlled by said synchronizing signal, said magnetic field reversing means including means for physically moving said permanent magnet from a first position to a second position whereby the polarity of said magnetic field is reversed;

second sensing means adapted to be placed on the skin or in the tissue of said being at a location adjacent said vessel, amplifier means for amplifying the signal sensed by said second sensing means, means for reversing the polarity of said amplifier means during said reversal of said magnetic field, and measuring means synchronized by the synchronizing signal for averaging the pulsatile signal sensed by said second sensing means during a given number of heart cycles while the magnetic field is stable at one polarity, and for averaging an equal number of heart cycles after reversal of said polarity of both said magnetic field and said measuring circuit;

whereby there is obtained the wave shape of the blood flow pulses free from both the local cardiogram and the random noise.

5. The electromagnetic flowmeter of claim 4, wherein said permanent magnet is driven by a motor controlled in accordance with said synchronizing signal.

6. The electromagnetic flowmeter of claim 4, including a pole piece made of highly permeable material and supported in a fixed position close to the vessel under investigation, said pole piece supported adjacent said permanent magnet in a position which provides a small air gap between the end of said pole piece and said permanent magnet during the periods of measurement.

7. The electromagnetic flowmeter oF claim 6, wherein said pole piece is made of soft iron.