Cerebral perfusion monitor
First Claim
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1. A method of estimating cerebral blood flow, comprising:
- a) obtaining a measure of time-varying blood volume in the head, using impedance plethysmography electrode units that pass current through the head;
b) obtaining a measure of time-varying blood volume in the scalp using a plethysmography sensor; and
c) weighting the measures of time-varying blood volume in the head and time-varying blood volume in the scalpd) estimating the cerebral blood flow from the weighted measures of time-varying blood volume in the head and time-varying blood volume in the scalp.
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Abstract
A method of estimating cerebral blood flow includes obtaining a measure of time-varying blood volume in the head, using an impedance plethysmography (102 and 104), obtaining a measure of time-varying blood volume in the scalp, and using the time-varying blood volume in the head and scalp to estimate cerebral blood flow.
54 Citations
16 Claims
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1. A method of estimating cerebral blood flow, comprising:
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a) obtaining a measure of time-varying blood volume in the head, using impedance plethysmography electrode units that pass current through the head; b) obtaining a measure of time-varying blood volume in the scalp using a plethysmography sensor; and c) weighting the measures of time-varying blood volume in the head and time-varying blood volume in the scalp d) estimating the cerebral blood flow from the weighted measures of time-varying blood volume in the head and time-varying blood volume in the scalp. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A unit for estimating cerebral blood flow, adapted for placing on the head, the unit comprising:
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a) at least one electrode unit adapted to pass current through the head for impedance plethysmography, and adapted to be placed on the head so that a significant part of the current goes through the brain, the electrode unit comprising; i) a current-carrying electrode adapted for injecting current through the head when it is placed on the skin; and ii) a voltage-measuring electrode adapted for measuring voltage across the head when it is placed on the skin, and when the current-carrying electrode is injecting current; and b) a plethysmography sensor adapted for measuring blood flow in a scalp;
adapted for use in infant patients, wherein the current-carrying electrode comprises an annulus surrounding the voltage-measuring electrode, and the radial thickness of the annulus and the gap between the current-carrying and voltage-measuring electrodes are each at least twice as great as a typical thickness of the epidermis in said infant patients. - View Dependent Claims (13, 14)
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15. A system for estimating cerebral blood flow, comprising:
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a) at least one plethysmography sensor adapted for measuring time-varying blood volume in a scalp; b) an impedance measuring unit comprising at least two electrode units adapted for placing on the head and performing impedance plethysmography to measure time-varying blood volume in the head; c) a power supply adapted for passing current across the head between the at least two electrode units of the impedance measuring unit, when said electrode units are placed on different sides of the head; and d) a data analyzer which calculates a cerebral blood flow using a weighted difference between impedance data on time-varying blood volume of the head obtained from the impedance measuring unit, and data on time-varying blood volume in the scalp generated by the plethysmography sensor. - View Dependent Claims (16)
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Specification