Device and method for measuring blood flow in an organ
First Claim
1. A device for measuring blood flow in an organ using an injected indicator comprising:
- a radiation source for emitting near infrared radiation into tissue of the organ at a first location;
a sensor for detecting a proportion of the emitted near infrared radiation that exits from the organ at a second location; and
an evaluation unit that detects the proportion of the emitted near infrared radiation that exits from tissue of the organ as a single input signal, said evaluation unit being programmed to perform the following evaluation steps;
(a) dividing up said single input signal into a pulsatile component and a non-pulsatile component;
(b) determining an injected indicator concentration with reference to the organ tissue from said non-pulsatile component of said single input signal;
(c) iteratively determining, from said non-pulsatile component, an inflow function i(t) that characterizes blood flow through the organ by incrementally varying a mean transit time mtt until a stop criterion is reached;
(d) determining an injected indicator concentration with reference to blood volume in the organ from said pulsatile component of said single input signal and the iteratively determined inflow function i(t);
(e) calculating a blood volume in the organ as a quotient of the injected indicator concentration with reference to the organ tissue and the injected indicator concentration with reference to the blood volume in the organ; and
(f) calculating a blood flow in the organ as a quotient of the blood volume in the organ and the mean transit time mtt when the stop criterion has been reached.
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Accused Products
Abstract
A device has a source for emitting near infrared radiation into cerebral tissue, a sensor for detecting radiation exiting from the tissue, and an evaluation unit which detects the exiting radiation as an input signal having pulsatile and non-pulsatile components and is programmed to determine the concentration of an injected indicator in the tissue from the non-pulsatile signal component, iteratively determine an inflow function characterizing cerebral blood flow by varying a mean transit time until reaching a stop criterion, determine indicator concentration relative to cerebral blood volume from the inflow function and the pulsatile signal component, calculate cerebral blood volume by dividing indicator concentration in the tissue by indicator concentration relative to cerebral blood volume, calculate cerebral blood flow by dividing the cerebral blood volume by the mean transit time when the stop criterion has been reached, and scale the inflow function using values determined from the pulsatile signal component.
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Citations
22 Claims
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1. A device for measuring blood flow in an organ using an injected indicator comprising:
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a radiation source for emitting near infrared radiation into tissue of the organ at a first location; a sensor for detecting a proportion of the emitted near infrared radiation that exits from the organ at a second location; and an evaluation unit that detects the proportion of the emitted near infrared radiation that exits from tissue of the organ as a single input signal, said evaluation unit being programmed to perform the following evaluation steps; (a) dividing up said single input signal into a pulsatile component and a non-pulsatile component; (b) determining an injected indicator concentration with reference to the organ tissue from said non-pulsatile component of said single input signal; (c) iteratively determining, from said non-pulsatile component, an inflow function i(t) that characterizes blood flow through the organ by incrementally varying a mean transit time mtt until a stop criterion is reached; (d) determining an injected indicator concentration with reference to blood volume in the organ from said pulsatile component of said single input signal and the iteratively determined inflow function i(t); (e) calculating a blood volume in the organ as a quotient of the injected indicator concentration with reference to the organ tissue and the injected indicator concentration with reference to the blood volume in the organ; and (f) calculating a blood flow in the organ as a quotient of the blood volume in the organ and the mean transit time mtt when the stop criterion has been reached. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A device for measuring blood flow in an organ using an injected indicator comprising:
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a radiation source for emitting near infrared radiation into tissue of the organ at a first location; a sensor for detecting a proportion of the emitted near infrared radiation that exits from the organ at a second location; and an evaluation unit that detects the proportion of the emitted near infrared radiation that exits from tissue of the organ as a single input signal, said evaluation unit being programmed to perform the following evaluation steps; (a) dividing up said single input signal into a pulsatile component and a non-pulsatile component; (b) determining an injected indicator concentration with reference to the organ tissue from said non-pulsatile component of said single input signal; (c) iteratively determining, from said non-pulsatile component, an inflow function i(t) that characterizes blood flow through the organ by incrementally varying a mean transit time mtt until a stop criterion is reached; (d) determining an injected indicator concentration with reference to blood volume in the organ from said pulsatile component of said single input signal and the iteratively determined inflow function i(t); (e) calculating a blood volume in the organ as a quotient of the injected indicator concentration with reference to the organ tissue and the injected indicator concentration with reference to the blood volume in the organ; (f) calculating blood flow in the organ as a quotient of the blood volume in the organ and the mean transit time mtt when the stop criterion has been reached; and (g) scaling the inflow function i(t) by means of values determined from said pulsatile component of said single input signal.
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10. A method for measuring blood flow in an organ of a patient comprising the steps of:
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injecting the patient with an indicator; emitting near infrared radiation into tissue of the organ at a first location; detecting a proportion of the emitted near infrared radiation that exits from the organ at a second location as a single input signal; dividing up said single input signal into a pulsatile component and a non-pulsatile component; determining an injected indicator concentration with reference to the organ tissue from said non-pulsatile component of said single input signal; iteratively determining, from said non-pulsatile component, an inflow function i(t) that characterizes blood flow through the organ by incrementally varying a mean transit time mtt until a stop criterion is reached; determining an injected indicator concentration with reference to blood volume in the organ from said pulsatile component of said single input signal and the iteratively determined inflow function i(t); calculating a blood volume in the organ as a quotient of the injected indicator concentration with reference to the organ tissue and the injected indicator concentration with reference to the blood volume in the organ; and calculating a blood flow in the organ as a quotient of the blood volume in the organ and the mean transit time mtt when the stop criterion has been reached. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A method for measuring blood flow in an organ comprising the steps of:
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injecting an indicator; emitting near infrared radiation, into tissue of the organ at a first location; detecting a proportion of the emitted near infrared radiation that exits from the organ at a second location as a single input signal; dividing up said single input signal into a pulsatile component and a non-pulsatile component; determining an injected indicator concentration with reference to the organ tissue from said non-pulsatile component of said single input signal; iteratively determining, from said non-pulsatile component, an inflow function i(t) that characterizes blood flow through the organ by incrementally varying a mean transit time mtt until a stop criterion is reached; determining an injected indicator concentration with reference to blood volume in the organ from said pulsatile component of said single input signal and the iteratively determined inflow function i(t); calculating a blood volume in the organ as a quotient of the injected indicator concentration with reference to the organ tissue and the injected indicator concentration with reference to the blood volume in the organ; calculating a blood flow in the organ as a quotient of the blood volume in the organ and the mean transit time mtt when the stop criterion has been reached; and scaling the inflow function i(t) by means of values determined from said pulsatile component of said single input signal. - View Dependent Claims (20, 21)
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22. A device for measuring blood flow in an organ using an injected indicator comprising:
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a radiation source for emitting near infrared radiation into tissue of the organ at a first location; a sensor for detecting a proportion of the emitted near infrared radiation that exits from the organ at a second location; and an evaluation unit that detects the proportion of the emitted near infrared radiation that exits from tissue of the organ as a single input signal, said evaluation unit being programmed to perform the following evaluation steps; (a) dividing up said single input signal into a pulsatile and a non-pulsatile component; (b) determining an injected indicator concentration with reference to the organ tissue from said non-pulsatile component of said single input signal; (c) iteratively determining, from said non-pulsatile component, an inflow function i(t) that characterizes blood flow through the organ by incrementally varying a mean transit time mtt until a stop criterion is reached; (d) determining an injected indicator concentration with reference to blood volume in the organ from said pulsatile component of said single input signal and the iteratively determined inflow function i(t); (e) scaling the inflow function i(t) by means of values determined from said pulsatile component of said single input signal; (f) back-extrapolating the scaled inflow function i(t) to a time of injection of the indicator; (g) calculating a blood volume in the organ as a quotient of the injected indicator concentration with reference to the organ tissue and the injected indicator concentration with reference to the blood volume in the organ; and (h) calculating a blood flow in the organ as a quotient of the blood volume in the organ and the mean transit time mtt when the stop criterion has been reached.
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Specification